Abstract P2-06-02: Development of a first-in-class small molecule inhibitor (EC359) targeting oncogenic LIF/LIFR signaling for the treatment of triple negative breast cancer

Background: Leukemia inhibitory factor (LIF) and its receptor LIFR are over-expressed in multiple solid tumors and play a key role in tumor growth, progression, and resistance to standard anti-cancer treatments. Triple-negative breast cancer (TNBC) lacks targeted therapies and represents a disproportional share of breast cancer (BCa) mortality. TNBC exhibits autocrine stimulation of the LIF/LIFR axis and overexpression of LIF is associated with poorer relapse-free survival in BCa patients. LIF signaling also promotes maintenance of stem cells. Therefore, targeting the LIF/LIFR axis may have therapeutic utility in TNBC.

Methods: We rationally designed a small organic molecule (EC359) that emulates the LIF/LIFR binding site and functions as a LIFR inhibitor from a library of compounds. In silico docking studies were used to identify the putative interaction of the EC359 and LIF/LIFR complex. Direct binding of EC359 to LIFR was confirmed using surface plasmon resonance (SPR) and microscale thermophoresis technique (MST) assays. In vitro activity was tested using Cell-Titer Glo, MTT, invasion, and apoptosis assays. Mechanistic studies were conducted using Western blot, reporter gene assays, and RNA-seq analysis. Xenograft, patient-derived xenograft (PDX), and patient-derived explant (PDEX) models were used for preclinical evaluation and toxicity.

Results: Molecular docking studies showed that EC359 interacts at the LIF/LIFR binding interface. SPR and MST studies confirmed direct interaction of EC359 to LIFR. EC359 reduced the growth of TNBC cells with high potency (IC50 50-100nM) and promoted apoptosis. Further, EC359 treatment reduced invasion and stemness of TNBC cells. EC359 activity is dependent on the expression levels of LIFR and showed little or no activity on TNBC cells that have low levels of LIFR or ER+ve BCa cells. Further, EC359 significantly reduced the viability of cisplatin and taxane-resistant TNBC cells and enhanced the efficacy of HDAC inhibitors. Mechanistic and biochemical studies showed that EC359 interacts with LIFR and effectively blocking LIF/LIFR interactions. EC359 also blocked LIFR interactions with other LIFR ligands such as oncostatin M, ciliary neurotrophic factor, and cardiotrophin-1. EC359 treatment attenuated the activation of LIF/LIFR driven pathways including STAT3, mTOR, AKT, and MAPK. RNA-seq analysis identified regulation of apoptosis as one of the important pathway modulated by EC359. In TNBC xenograft and PDX assays, EC359 significantly reduced tumor progression. Further, using human primary BCa PDEX cultures, we demonstrated that EC359 has the potential to substantially reduce the proliferation of human BCa. Pharmacologically, EC359 exhibited high oral bioavailability and long half-life with a wide therapeutic window.

Conclusions: EC359 is a novel targeted therapeutic agent that inhibits LIF/LIFR oncogenic signaling in TNBC via a unique mechanism of action. EC359 has the distinct pharmacologic advantages of oral bioavailability, in vivo stability, and is associated with minimal systemic side effects. (DOD BCRP grant #BC170312)

Citation Format: Viswanadhapalli S, Luo Y, Sareddy GR, Santhamma B, Zhou M, Li M, Pratap UP, Altwegg KA, Li X, Srinivasan U, Ma S, Chang A, Riveros AC, Zhang KY, Dileep KV, Pan X, Murali R, Bajda M, Raj G, Brenner A, Manthati V, Rao M, Tekmal RR, Nair HB, Nickisch KJ, Vadlamudi RK. Development of a first-in-class small molecule inhibitor (EC359) targeting oncogenic LIF/LIFR signaling for the treatment of triple negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-06-02.

Abstract P5-04-23: Enhancing the activity of a novel estrogen receptor coregulator binding modulator (ERX-11) against ER-positive therapy resistant breast cancer

Background:We had previously reported a novel small molecule, ERX-11, that directly interacts with ER and blocks the interaction between a subset of coregulators with both native and mutant forms of ER. ERX-11 effectively blocks ER oncogenic signaling and has potent anti-proliferative activity against therapy-sensitive and therapy-resistant human breast cancer cells. To enhance the clinical translation of ERX-11, we sought to pursue both lead optimization and evaluate combinations of ERX-11 with other approved agents in breast cancer.

Methods: We designed, synthesized and tested 500 derivatives of ERX-11 in multiple models of ER+ breast cancer. We also tested combinations of ERX-11 with multiple agents, including other ER targeting agents, chemotherapies and CDK4/6 inhibitors. We tested the effect of combination therapy using breast cancer cells with acquired resistance (Tamoxifen, Letrozole, Ribociclib resistant) and engineered models that express ER mutations. In vitro activity was tested using Cell titer glo, MTT, and apoptosis assays. Mechanistic studies were conducted using Western blot, reporter gene assays and RNA-seq analysis. Xenograft, patient derived xenograft (PDX), patient derived explant (PDE) and xenograft derived explant (XDE) models were used for preclinical evaluation and toxicity.

Result: Evaluation of 500 analogs of ERX-11 identified a number of leads with differential activity against ER+ and ER- breast cancer cells, identified several analogs including ERX-144, 208, 296, 315 with nanomolar potency against ER+ and therapy-resistant ER+ breast cancers. Validation of the mechanism of action of these analogs is ongoing. The combination of ERX-11 and palbociclib significantly blocked ER-mediated and ER-coregulators mediated oncogenic signaling and showed potent anti-proliferative activity against both endocrine therapy-sensitive and resistant breast cancer cells. In addition, ERX-11 inhibited ribociclib-resistant ER+ cell proliferation in a dose dependent manner. Mechanistic studies using IP-Mass spectrometry demonstrated that ERX-11 and palbociclib blocks the interaction between larger subset of coregulators with ER in therapy resistant breast cancer models. ERX-11 and palbociclib both exhibited potent anti-proliferative activity against therapy-sensitive and therapy-resistant ER+ve breast cancer cells, in xenograft models and in PDEs. Importantly, combination therapy of ERX-11 and palbociclib synergistically reduced the growth of tamoxifen and letrozole resistant xenograft tumors compared to either drug alone. Mass spec based DIA analyses and RNA-seq studies revealed that combinational treatment uniquely activated p53, unfolded response mediated apoptotic pathways, altered DNA damage response and suppressed E2F and Myc target genes. Biochemical studies confirmed combination therapy significantly altered E2F1, ER and DNA damage response pathways.

Conclusion: We have successfully pursued two avenues to improving ERX-11 for clinical translation. We have developed ERX-11 analogs with higher potency against ER+ breast cancer. We have shown that combinational treatment with ERX-11 and palbociclib may overcome endocrine therapy resistance and CDK4/6 inhibitor (ribociclib) resistance.

Citation Format: Viswanadhapalli S, Ma S, Lee T-K, Sareddy GR, Liu X, Ekoue D, Alluri A, Luo Y, Kassees K, Arteaga C, Alluri P, Weintraub SE, Tekmal RR, Ahn J-M, Raj GV, Vadlamudi RK. Enhancing the activity of a novel estrogen receptor coregulator binding modulator (ERX-11) against ER-positive therapy resistant breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-04-23.

Abstract P4-07-01: A small molecule inhibitor (ERX-41) induces endoplasmic reticulum stress in triple negative breast cancer

Background: Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer and represents a disproportional share of the breast cancer mortality, primarily due to a lack of targeted therapies. There is a major unmet need for rationally designed novel therapies that can extend survival of patients with TNBC. TNBCs are characterized by a high basal level of endoplasmic reticulum stress, due to high protein turnover and need for proliferation. Recent studies revealed the role of several members of the Nuclear Receptor (NR) superfamily as molecular drivers in TNBC, including the androgen receptor (AR), glucocorticoid receptor (GR) and the orphan NR tailless (TLX).

Methods: Recently, using peptidomimetics, we have developed small molecules that specifically target and block interactions of multiple coregulators with oncogenic NRs. We performed a screen of our 500+ compound peptidomimetic library derived from our ERX-11 oligobenzamide (that was rationally designed to target ERα) for anti-proliferative activity in TNBC cell lines. Identified leads were then validated in multiple TNBC cell lines. In vitro activity was tested using Cell titer glo, MTT, matrigel invasion, and apoptosis assays. Mechanistic studies were conducted using Western blot, reporter gene assays, CRISPR/Cas9 KO and RNA-seq analysis. Xenograft, patient derived xenograft (PDX), patient derived explant (PDE) and xenograft derived explant (XDE) TNBC models were used for preclinical evaluation and toxicity.

Results: We have identified a first-in-class drug (ERX-41) that has potent activity (IC50 = 50-250nM) against all six molecular subtypes of TNBC. Systematic evaluation using CRISPR/Cas9 KO screen and overexpression screen comprising 48 NRs identified TLX as a preferred target of ERX-41. Analyses of primary breast tumors revealed TLX was highly expressed in TNBC. Further, TLX was amplified in nearly 50% of TNBC xenografts (cbioportal.org). Modelling, mechanistic and biochemical studies showed that ERX-41 interact with TLX and selectively blocks its interactions with coregulators. Gene expression analyses revealed both significant reduction of TLX-activated genes (CCND1, WNT7A) and significant activation of TLX-repressed genes (p21) upon treatment with ERX-41 in TNBC models. Gene ontogeny pathway analyses of RNA-seq data in TNBC cells showed that ERX-41 treatment positively correlated with apoptosis. Our ultrastructural studies indicated that ERX-41 enhances endoplasmic reticulum stress in TNBC inducing autophagic flux and subsequent apoptosis. ERX-41 has significant potency against multiple TNBC xenografts and PDXs in vivo, PDEs and XDEs ex vivo, indicating its potential for clinical translation. Pharmacologically, ERX-41 exhibited high oral bioavailability and associated with minimal toxicity upon oral gavage for up to 120 days in animal studies.

Conclusions: We believe that the ability of ERX-41 to block NR signaling and target a critical molecular vulnerability in TNBC and its ability to enhance endoplasmic reticulum stress in TNBC, will revolutionize the therapeutic landscape of TNBC. ERX-41 is oral bioavailable, potent against multiple TNBC molecular subtypes, and is associated with minimal systemic side effects. (supported by NIH grant RO1 CA223828-01)

Citation Format: Liu X, Viswanadhapalli S, Ma S, Lee T-K, Sareddy GR, Ekoue DN, Blatt EM, Zhou M, Li M, Tekmal RR, Ahn J-m, Vadlamudi RK, Raj GV. A small molecule inhibitor (ERX-41) induces endoplasmic reticulum stress in triple negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-07-01.

Abstract P1-09-09: Efficacy of estrogen receptor β agonists in the prevention of breast cancer progression to therapy resistance

Estrogen plays an important role in the initiation and progression of breast cancer (BCa). Approximately, 70% of breast tumors are estrogen receptor (ER) positive at the time of presentation. Endocrine therapy using aromatase inhibitors (AI), or anti-estrogen (AE) molecules are widely used for treating ER+ve BCa. However, their efficacy is limited by intrinsic and acquired therapy resistance and most patients develop resistance to these drugs. The transcriptional effects of estrogen are mediated by two ERs (ERα and ERβ) and both are expressed in normal breast tissue. Unlike ERα, ERβ functions as tumor suppressor. However, role of ERβ specific agonists in the prevention of BCa progression remains elusive. In this study, we investigated the effectiveness of two ERβ agonists (S-Equol and LY500307) in the prevention of BCa progression using endocrine therapy sensitive (MCF7-aro) and letrozole resistant (MCF7-aro-LTLT) cells. Our results demonstrated that treatment with ERβ agonists inhibit short-and long-term growth of both endocrine therapy sensitive and resistant BCa cells. In addition, ERβ agonists treatment inhibited invasion and migration of both MCF7-aro and MCF7-aro-LTLT cells. Importantly, cell cycle analysis revealed that ERβ agonists induced cell cycle arrest. Our gene microarray analysis demonstrated that both ERβ agonists significantly modulated genes involved in the cell cycle progression, DNA replication and cell death pathways. Further, gene enrichment analysis of differentially expressed genes revealed that genes involved in the cell cycle checkpoints emerged as significant pathway modulated by ERβ agonists treatment in MCF7-aro cells. Interestingly, in letrozole-resistant MCF7-aro cells, DNA replication was significantly affected by ERβ agonists treatment. Pathway analysis also identified enrichment for chemokine signaling pathways. We confirmed pathway analysis by qRT-PCR and western blot analysis. Accordingly, treatment of in vivo syngeneic xenografts with ERβ agonists significantly inhibited BCa progression. Collectively, these results from this study suggest that ERβ agonists have potential to prevent the progression of BCa progression.

Citation Format: Ramasamy K, Samayoa C, Krishnegowda NK, Vadlamudi RK, Tekmal RR. Efficacy of estrogen receptor β agonists in the prevention of breast cancer progression to therapy resistance [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-09-09.

Abstract P1-09-06: Blocking ER coregulator signaling enhances CDK4/6 inhibitor palbociclib therapy in ER-positive advanced breast cancer

BACKGROUND: Recently,CDK4/6 inhibitors in combination with endocrine therapy (AE/AI/SERDs) is approved for the treatment of ER+ advanced breastcancer (BCa). However, not all patients benefit from CDK4/6 inhibitors therapy. Emerging studies indicate many therapy-resistant tumors retainER signaling, via interaction with critical oncogenic coregulatorproteins. Considering complex signaling interplay of ER and CDK4/6 axis, combination therapy of CDK inhibitor with other potent ER-targeted agents that block ER coregulatory signaling may extend the efficacy and may prevent the development of resistance to the CDK4/6 inhibitors. We recently developed a small organic molecule, ER coregulator binding modulator ERX-11 (EtiraRx-11). The objective of this study is to test the utility of novel combination therapy of ERX-11 with CDK4/6 inhibitor palbociclib in treating therapy resistant advanced BCa.

METHODS: We have utilized multiple therapy sensitive and therapy-resistant BCa models with various genetic backgrounds. We tested efficacy using both acquired resistance and engineered models that express ER mutations or oncogenes. Efficacy of combination therapy was tested using established in vitro assays including, MTT, colony formation, apoptosis, and cell cycle progression. Mechanistic studies were conducted using reporter gene assays, gene expression, RNA-seq analysis and signaling alterations. Patient-derived BCa explant and Xenograft studies were used to determine the in vivo efficacy of the combination therapy.

RESULTS: ERX-11 effectively blocked ER-mediated and ER-coregulator mediated oncogenic signaling and has potent anti-proliferative activity against both endocrine therapy-sensitive and therapy-resistant BCa cells. Mechanistic studies using IP-Mass spectrometry showed that ERX-11 blocks the interaction between a subset of coregulators with ER in resistant BCa models. ERX-11 exhibited potent anti-proliferative activity against therapy-sensitive and therapy-resistant ER-driven BCa cells in vitro, in xenograft models in vivo and in patient-derived breast tumor explants ex vivo. Co-treatment of ERX-11 with palbociclib synergistically reduced cell viability and induced apoptosis of therapy sensitive and resistant BCa model cells. Importantly, combination therapy of ERX-11 and the palbociclib synergistically reduced the growth and induced apoptosis of tamoxifen and letrozole resistant xenograft tumors compared to either drug alone. RNA-seq studies revealed that combinational treatment with ERX-11 and palbociclib uniquely activated p53 and unfolded response mediated apoptotic pathways and suppressed E2F and Myc target genes. Biochemical studies confirmed combination therapy significantly altered E2F1 and ER signaling pathways and promoted apoptosis.

CONCLUSIONS: Our data support a critical role of blocking ER coregulator signaling in treating therapy resistance in advanced ER+ BCa. Combinational treatment with ERX-11 and palbociclib may overcome/delay endocrine therapy resistance.

Citation Format: Viswanadhapalli S, Sareddy GR, Zhou M, Ali E, Li X, Ma S-H, Lee T-K, Tekmal RR, Ahn J-M, Raj GV, Vadlamudi RK. Blocking ER coregulator signaling enhances CDK4/6 inhibitor palbociclib therapy in ER-positive advanced breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-09-06.

Abstract P6-11-15: Pre-clinical investigation of estrogen receptor β agonists for the treatment of breast cancer

Breast Cancer is the primary cause of cancer-associated mortality worldwide, and in United States alone, more than 250,000 women are diagnosed every year. Current breast cancer treatment strategies focus on Estrogen Receptor α signaling, given that the majority of cases diagnosed are ERα positive. These treatment strategies include endocrine therapies; such as anti-estrogens or aromatase inhibitors. Although, endocrine therapy has been demonstrated to be successful and effective, therapy resistance commonly arises and results in relapse. While current endocrine therapies focus on ERα signaling, emerging studies highlight the importance of Estrogen Receptor β.Unlike ERα, ERβ has been shown to have tumor-suppressive function in various cancers, including breast cancer. Recent studies have identified, synthesized, and tested the clinical safety of ERβ-selective agonists. The objective of this study was to investigate the utility of using ERβ agonists in the treatment of breast cancer.

To investigate the utility of ERβ agonists in the treatment of breast cancer, we used in-vitro and in-vivo pre-clinical models systems. Our results demonstrated that treatment with ERβ agonists, S-Equol and LY500307, was able to inhibit the short-term and long-term growth of both endocrine therapy sensitive and resistant breast cancer cells. Progression through the cell cycle, cell migration and cell invasion was also abrogated upon treatment. In-vivo, our syngeneic tumor mouse model demonstrates a decline in tumor growth rate after treating with a combination of letrozole and ERβ agonist. Gene expression array analysis reveal that treatment with ERβ agonist elicits changes in key signaling molecules involved in cell death and cell cycle pathways. In Letrozole resistant cells, Letrozole treatment had not effect on gene expression, while LY500307 treatment resulted in the modulation of 780 genes. Interestingly, combining Letrozole with LY500307 resulted in the modulation of 966 genes, of which 417 were unique to the combination treatment. Our studies suggest that activation of ERβ signaling is a valuable strategy in the treatment of breast cancer, even in cases which have developed resistance to current endocrine therapies.

Citation Format: Samayoa C, Krishnegowda NK, Vadlamudi RK, Tekmal RR. Pre-clinical investigation of estrogen receptor β agonists for the treatment of breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-11-15.

Abstract P4-15-02: Investigating the use estrogen receptor β agonists in the prevention of breast cancer using a transgenic mouse model

Breast cancer is the most common cancer among women worldwide. In the United States, 1 in 8 women will develop breast cancer during her lifetime, and in 2016 over 240,000 new cases will be diagnosed. Incidence rates differ by geographic location, with women living in Asia having the lowest rates. However, after migrating to the U.S and adopting a western diet their rates increase. This highlights the importance of lifestyle, including diet, in modulating breast cancer risk. Soy has been previously implicated as the dietary component contributing to the reduced breast cancer rates in Asian women. Compounds that can selectively activate Estrogen Receptor β have been identified in plants, including soy. Given the tumor-suppressive properties of ERβ, it may be possible to use these agonists in the chemoprevention of breast cancer.

The objective of this study was to investigate the utility of using ERβ agonists in the prevention of breast cancer using a transgenic mouse model. MMTV-HER2/neu mice develop premalignant lesions at 4-5 months, and tumors starting at month 7 due to overexpression of the Her2/neu proto-oncogene. MMTV-HER2/neu mice were treated with 2 different ERβ agonists, S-equol or LY500307, for 3 months and evaluated for branching, hyperplasia and differential gene expression. When compared to controls, ERβ agonist-treated mice exhibited a significant decrease in branching and ductal hyperplasia, with no change in body weight. Differential gene expression analysis revealed 218 modified genes in response to S-equol treatment, and 258 genes modified by LY500307 treatment, with an overlap of 36 genes. Pathway analysis identified an enrichment for chemokines signaling pathways, particularly TNF, in the reversal of hyperbranching resulting from treatment with ERβ agonists.

Although previous studies have demonstrated crosstalk between ER's non-genomic signaling and growth factor signal transductions pathway, this is the first study to demonstrate the impact of ERβ activation on HER2/neu mediated pre-neoplastic changes. Our study suggest that ER β agonist treatment may be a valuable therapeutic option for the chemoprevention of breast cancer in women at increased risk.

Citation Format: Samayoa C, Krishnegowda NK, Vadlamudi RK, Tekmal RR. Investigating the use estrogen receptor β agonists in the prevention of breast cancer using a transgenic mouse model [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-15-02.

Abstract S3-04: ESR1 coregulator binding inhibitor (ECBI) as a novel therapeutic to target hormone therapy resistant metastatic breast cancer

BACKGROUND: Estrogen contribute to the progression of breast cancer via estrogen receptor 1 (ESR1) and current therapies involve either antiestrogens or aromatase inhibitors. However, most patients develop resistance to these drugs. Critically, therapy-resistant tumors retain ESR1-signaling. Mechanisms of therapy resistance involve the activation of ESR1 in the absence of ligand or mutations in ESR1 that allow interaction between the ESR1 and coregulators leading to sustained ESR1 signaling and proliferation. For patients with therapy-resistant breast cancers, there is a critical unmet need for novel agents to disrupt ESR1 signaling by blocking ESR1 interactions with its coregulators.

METHODS: Using rational design, we synthesized and evaluated a small organic molecule (ESR1 coregulator binding inhibitor, ECBI) that mimics the ESR1 coregulator nuclear receptor box motif. Using in vitro cell proliferation and apoptosis assays, we tested the effect of ECBI on several breast cancer and therapy-resistant model cells. Mechanistic studies were conducted using established biochemical assays, reporter gene assays, RT-qPCR and RNA-Seq analysis. Differentially expressed genes were analyzed using Ingenuity Pathway Analysis (IPA). ESR1 positive (MCF7 and ZR75) xenografts were used for preclinical evaluation and toxicity. The efficacy of ECBI was tested using ex vivo cultures of freshly extirpated primary human breast tissues.

RESULTS: In estrogen induced proliferation assays using several ESR1 positive model cells, ECBI significantly inhibited growth and promoted apoptosis. Importantly, ECBI showed little or no activity on ESR1 negative cells. Further, ECBI also reduced the proliferation of several ESR1 positive hormonal therapy resistant cells. Mechanistic studies showed that ECBI interacts with ESR1, efficiently blocks ESR1 interactions with coregulators and reduces the ESR1 driven ERE reporter gene activity. Further, ECBI directly interacted with mutant-ESR1 with high affinity and significantly inhibited mutant-ESR1 driven oncogenic activity. RNA sequencing analysis revealed that ECBI blocks multiple ESR1 driven pathways, likely representing the ability of a single ECBI compound to block multiple ESR1-coregulator interactions. Treatment of ESR1-positive xenograft tumors with ECBI (10 mg/kg/day/oral) significantly reduced the tumor volume compared to control. Further, ECBI also significantly reduced the tumor growth of coregulator-overexpressed breast cancer cells in xenograft model. Using human primary breast tissue ex vivo cultures, we have provided evidence that ECBI has potential to dramatically reduce proliferation of human breast tumors.

CONCLUSIONS: The ECBI is a novel agent that targets ESR1 with a unique mechanism of action. ECBI has distinct pharmacologic advantages of oral bioavailability, in vivo stability, and is associated with minimal systemic side effects. Remarkably, ECBI block both native and mutant forms of ESR1 and have activity against therapy resistant breast cancer cell proliferation both in vitro and in vivo and against primary human tumor tissues ex vivo. Thus development of ECBI represents a quantum leap in therapies to target ESR1.

Citation Format: Vadlamudi RK, Sareddy GR, Viswanadhapalli S, Lee T-K, Ma S-H, Lee WR, Mann M, Krishnan SR, Gonugunta V, Strand DW, Tekmal RR, Ahn J-M, Raj GV. ESR1 coregulator binding inhibitor (ECBI) as a novel therapeutic to target hormone therapy resistant metastatic breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr S3-04.

Proline, glutamic acid and leucine-rich protein-1 is essential for optimal p53-mediated DNA damage response

Proline-, glutamic acid- and leucine-rich protein-1 (PELP1) is a scaffolding oncogenic protein that functions as a coregulator for a number of nuclear receptors. p53 is an important transcription factor and tumor suppressor that has a critical role in DNA damage response (DDR) including cell cycle arrest, repair or apoptosis. In this study, we found an unexpected role for PELP1 in modulating p53-mediated DDR. PELP1 is phosphorylated at Serine1033 by various DDR kinases like ataxia-telangiectasia mutated, ataxia telangiectasia and Rad3-related or DNAPKc and this phosphorylation of PELP1 is important for p53 coactivation functions. PELP1-depleted p53 (wild-type) breast cancer cells were less sensitive to various genotoxic agents including etoposide, camptothecin or γ-radiation. PELP1 interacts with p53, functions as p53-coactivator and is required for optimal activation of p53 target genes under genomic stress. Overall, these studies established a new role of PELP1 in DDRs and these findings will have future implications in our understanding of PELP1's role in cancer progression.

Abstract P5-09-14: Plant-derived estrogen receptorb agonists alone or in combination with aromatase inhibitors restore sensitivity in endocrine therapy resistant breast tumors

Estrogen receptors (ER) play an important role in breast cancer. Over two-thirds of all breast cancers express ERa, and current endocrine therapies target its signaling. Antiestrogens (AE) block the binding of estrogen to ERα, while aromatase inhibitors (AI) inhibit local and systemic estrogen production. Both treatments improve outcomes for about 50% of patients with early or advanced ERα positive breast cancer. Unfortunately, therapeutic resistance frequently arises. There is a critical need to develop effective alternate strategies to prevent or delay the development of resistance to endocrine therapy and the resulting tumor progression. Both normal and tumor tissue express ERβ which has anti-proliferative activity and recent studies have identified several natural compounds that have the potential to function as ERβ agonists. Plant-derived ERβ-agonists, Liquiritigenin (Liq), from the plant Glycyrrhizae uralensis and S-equol, from the soy isoflavone daidzein, are currently in clinical trials for the treatment of vasomotor hot flashes associated with menopause. In this study we sought to determine if ERβ agonists alone or in combination with AI could resensitize Letrozole-resistant breast cancer cells in vivo. Xenografts were established using cells which model post-menopausal breast cancer. Endocrine therapy sensitive (MCF-7aro) and Letrozole resistant (LTLT-Ca) tumors were treated with either ERβ agonists or in combination with AI and progression was measured. In MCF-7aro tumors, ERβ agonist treatment reduced tumor volume and prolonged sensitivity to AI. In the therapy resistant tumors (LTLT-Ca), ERβ agonist treatment blocked tumor growth and restored sensitivity to AI therapy. To determine the molecular mechanism by which ERβ agonists inhibit tumor growth and prolong and restore sensitivity, qRT-PCR and western blot analysis was performed. Our results show changes in the levels of p53, NFkB, cyclin D1, and KLF5 in addition to other genes. To determine the role of ERβ agonists on the activation of these genes specific gene promoter-luciferase reporter constructs were used and the specificity of ERβ-mediated actions was confirmed using a siRNA approach. This study suggests that ERβ acts as a tumor suppressor by suppressing cell growth through the inhibition of cell cycle genes and by inducing apoptosis through the regulation of p53. In conclusion, this study demonstrates the potential role for ERβ agonists to improve adjuvant endocrine therapy to treat both hormone-responsive and hormone-resistant breast cancers.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-09-14.

Abstract P1-06-01: NSAID use attenuates breast cancer recurrence in obese women: Role of prostaglandin-aromatase interactions

Introduction: Obesity is associated with a worse breast cancer prognosis, with the most prominent effects seen in hormone responsive postmenopausal patients. It has also been linked to elevated levels of inflammation, including greater cyclooxygenase-2 (COX-2) expression and activity in adipose-infiltrating macrophages. The product of this enzyme, the pro-inflammatory eicosanoid prostaglandin E2 (PGE2), stimulates adipose tissue aromatase expression and subsequent estrogen production, which could promote breast cancer progression. Consequently, we hypothesized that non-steroidal anti-inflammatory drug (NSAID) use decreases estrogen receptor (ER) positive breast cancer recurrence in the obese population via inhibition of PGE2-mediated local aromatase expression.

Methods: Four-hundred and forty women treated for invasive, ER positive breast cancer at San Antonio area clinics were retrospectively classified according to NSAID use, body mass index category (Normal Weight (NW): 18.5-24.9 kg/m2; Overweight (OW): 25.0-29.9 kg/m2; Obese (OB): ≥30.0 kg/m2), and disease recurrence. To examine the role of obesity-induced local aromatase expression in the link between NSAID use and disease recurrence, we utilized an in vitro model of obesity in which we exposed macrophages to pooled sera samples from NW or OB postmenopausal breast cancer patients. Adipose stromal cells’ (ASC) aromatase expression was measured following exposure to conditioned media (CM) collected from these sera-exposed macrophages. ER activity and in vitro measures of cancer aggression were assessed in MCF-7 and T47D breast cancer cells cultured in CM from sera-exposed macrophage/ASC co-cultures.

Results: Within our patient population, which had an average BMI in the obese range, NSAID users had significantly lower recurrence rates (p = 0.05) and their time to disease progression was delayed by almost 28 months in comparison to nonusers. Our in vitro studies demonstrated that growth in OB macrophage CM significantly enhances ASC aromatase expression in comparison to NW (p<0.05), while macrophage treatment with celecoxib during the generation of CM neutralizes the difference between OB and NW. This was correlated with significantly greater macrophage PGE2 production following OB versus NW sera exposure (p<0.05). In addition, CM from macrophage/ASC co-cultures exposed to OB patient sera stimulates more breast cancer cell ER activity, proliferation, and S phase activity, and these differences are eliminated by the addition of an aromatase inhibitor during the generation of CM. We also plan to examine how the co-culture CM impacts breast cancer cell expression of a panel of genes related to cancer aggression.

Conclusions: Our results indicate that NSAID use can improve the recurrence rate for hormone-responsive breast cancer patients, particularly those with an elevated BMI. The in vitro model suggests that obesity-related enhancement of PGE2-induced local aromatase expression and estrogen production may be a key mechanism mediating this effect. Further studies designed to examine the clinical benefit of NSAID use in the obese breast cancer patient population are warranted.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-06-01.

Abstract P2-05-01: Induction of PELP1 expression in mammary gland promotes tumorigenesis by enhancing CDK-CyclinD1 signaling

Introduction: Estrogen receptor coregulator over-expression promotes carcinogenesis and/or progression of endocrine related-cancers where steroid hormones are powerful mitogenic agents. Recent studies in our laboratory as well as others demonstrated that PELP1 is a proto-oncogene and a prognostic indicator of decreased survival in breast cancer patients. Recent studies indicated that PELP1 is needed for optimal epigenetic modifications at ER target genes and PELP1 interactions with KDM1 play a key role in PELP1 mediated oncogenic functions. However, the in vivo significance of PELP1 deregulation during initiation and progression of breast cancer remains unknown. The objective of this study is determine the molecular mechanisms by which PELP1 regulate breast cancer progression in vivo.

Method: To determine the significance of PELP1 over-expression in mammary tumorigenesis, we used an inducible, tissue-specific PELP1 expressing transgenic mouse. Mammary epithelial-specific expression of PELP1 was validated by immunohistochemistry and Western blot analysis. PELP1-mediated morphological and histological changes were analyzed by examining carmine-stained whole mounts and H&E-stained paraffin embedded mammary glands sections. Differential expression of breast cancer-focused genes between wild type and PELP1 transgenic mammary glands was determined using real-time RT2 Profiler PCR array. Proliferation was analyzed using Ki-67 immuno staining. RTqPCR, Western and IHC analysis were used to confirm the changes in the expression of PELP1 regulated genes.

Results: We observed an increase in proliferation, extensive side branching and precocious differentiation in PELP1 expressing mammary gland compared to controls. Aged MMTVrtTA-TetOPELP1 bitransgenic mice revealed hyperplasia and preneoplastic changes as early as 12 weeks and mammary tumors occurred at a latency of 10.5 months. Mechanistic studies using tissues from control and PELP1 transgenic mice revealed that PELP1 deregulation modulates expression of a number of known ER target genes involved in cellular proliferation (such as cyclin D1, CDKs) and morphogenesis (EGFR, MMPs) and such changes facilitated altered mammary gland morphogenesis and tumor progression. Western and IHC analysis of mammary glands confirmed upregulation of CDK and Cyclin D1 protein levels in PELP1 Tg mice. Further, PELP1 is hyperphosphorylated at CDK phosphorylation site in PELP1 (Ser 991), suggesting an autocrine loop involving CDk-CyclinD1-PELP1 axis in promoting mammary tumorigenesis. Treatment of PELP1 Tg mice with pargyline, an inhibitor of KDM1 for four months significantly reduced PELP1 driven hyperplasia. Mechanistic studies revealed that pargyline treatment reduced cyclin D1 expression levels and substantially reduced CDK driven PELP1 phosphorylation.

Conclusions: PELP1 deregulation modulates expression of a number of known ER target genes and cancer promoting genes. PELP1 mediated epigenetic changes via KDM1 play role in PELP1 oncogenic functions in vivo. Collectively, these results support that PELP1 deregulation has potential to promote breast tumorigenesis in vivo.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-05-01.

Abstract P5-04-04: Significance of PELP1/HDAC2/microRNA-200 regulatory network in EMT and metastasis of breast cancer

Tumor metastasis remains a significant clinical problem and is the leading cause of death among breast cancer patients. Estrogen receptor (ER)-coregulators play an essential role in cancer progression and metastatic tumors express increased levels of coregulators. Proline glutamic acid rich protein (PELP1) is an ER coregulator, its expression is upregulated during breast cancer progression to metastasis and is an independent prognostic predictor of shorter survival of breast cancer patients. MicroRNA (miR) mediated regulation of tumorigenesis is emerging as a new paradigm in cancer biology and widespread misexpression of miRs has been reported in breast cancer. The objective of this study is to examine the mechanism and therapeutic significance of PELP1 regulation of miRs leading to breast cancer metastasis. We have used both ER+ve (ZR75, MCF7) and ER-ve (MDAMB231, MDAMB468) models that either stably overexpress PELP1 or PELP1shRNA. Boyden chamber, and invasion assays demonstrated that PELP1 down regulation significantly affect migration of both ER+ve and ER-ve cells. Epithelial to Mesenchymal Transition (EMT) real time qPCR Array studies identified PELP1 modulate expression of EMT genes Snail, Twist, ZEB1, ZEB2, Vimentin and MMPs. Importantly, whole genome microRNA array analysis using PELP1 model cells revealed that miR200a and miR141 were significantly upregulated in cells expressing PELP1-shRNA compared to control cells. Accordingly, over expression of PELP1 in low metastatic model cells decreased expression of miR200a and miR141. PELP1 regulation of miRs was further confirmed by ZEB1 and ZEB2 3′ UTR luciferase reporter assays. ChIP analysis revealed recruitment of PELP1 to the proximal promoter region of miR-200a and miR141 and promoter reporter assays further confirmed PELP1 regulation of miRs. Interestingly, PELP1 down regulated expression of miR200a and miR141 by promoting repressive chromatin modifications via HDAC2. Supporting this, HDAC inhibitors reversed PELP1 driven repressive effects. Further, ectopic expression of miR200a and miR141 mimetic decreased PELP1 mediated invasion/metastatic functions. Prognostic significance of PELP1-miRNA axis was determined using Tissue micro-array (TMA) and in situ hybridization (ISH assays) of Locked Nucleic Acid (LNA™)-based microarray approach in 102 human breast tumors. To test therapeutic potential in vivo, we have generated ZR-PELP1- and MCF7-PELP1-shMIMIC of miR200a and miR141 stable cells. In vitro gene expression and Boyden chamber assays using these model cells revealed that shMIMIC of miR200a and miR141 reversed PELP1 mediated alterations in gene expression and reduced PELP1 driven migration/invasion. Proof of principle studies using IVIS imaging of nude mice based assays of GFP-Luc labeled cells demonstrated therapeutic efficacy of miRIDIAN shMIMIC of miR200a and miR141 on PELP1 driven in vivo metastasis. Collectively, these novel findings demonstrate for the first time a previously unknown role for PELP1 in epigenetically controlling the functions of tumor metastasis suppressor miR-200a and miR141. These results suggest that PELP1-miR axis may be crucial stimulus for promoting EMT and breast cancer metastasis. This study is funded by NIH T32CA148724 Postdoc Fellowship Grant.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-04-04.

Abstract P6-04-07: Significance and therapeutic potential of PELP1-mTOR axis in breast cancer progression and therapy resistance

Proline, Glutamic-acid and Leucine-rich Protein 1 (PELP1) is a proto-oncogene that modulates ER signaling by functioning as an ER-coregulator. Emerging studies demonstrated that in a subset of breast tumors, PELP1 is predominantly localized in the cytoplasm and that PELP1 participates in extranuclear signaling by facilitating ER interactions with Src, PI3K, and AKT. PELP1 expression is upregulated in breast cancer, its deregulation contributes to therapy resistance, and PELP1 is a prognostic marker of poor survival. However, the mechanism by which PELP1 extranuclear actions contributes to cancer progression and therapy resistance remains unknown. We have recently discovered that PELP1 has the potential to interact with mammalian target of rapamycin (mTOR), a serine/threonine kinase that forms two distinct complexes called mTORC1 (containing Raptor and PRAS40) and mTORC2 (containing Rictor and Protor). The objective of this application is to test whether crosstalk occurs between mTOR and PELP1 signaling axis and to test whether mTOR targeting drugs can be used to target PELP1 oncogenic functions. We have used breast cancer cells with PELP1 overexpression (MCF7-PELP1, ZR75-PELP1, T47D-PELP1) or PELP1 down regulation (MCF7-PELP1shRNA, ZR75-PELP1shRNA) along with controls to study the role of PELP1 in the regulation of mTOR axis. PELP1 knockdown significantly reduced downstream mTOR signaling components as analyzed by Western analysis using phospho-S6K, -4EBP1, -mTOR and -Akt, antibodies. Overexpression of PELP1 activated mTOR signaling components. Using immunoprecipitation, we have demonstrated that PELP1 interacts with mTOR. Further immunopreciptation analysis using Rictor and Raptor specific antibodies revealed that PELP1 associates with both TORC1 and TORC2 complexes. Using PELP1WT and PELP1cyto (that predominantly localizes in the cytoplasm), we have demonstrated the differential activation of mTOR signaling components: PELP1WT activated both TORC1 and TORC2 pathways, while PELP1cyto uniquely activated TORC2. mTOR targeting drugs (Rapamycin or AZD8055) showed a significant effect on the in vitro proliferation of PELP1 model cells. AZD8055 is more potent in reducing PELP1 driven tumor growth in vivo compared to rapamycin. Immunohistochemical studies on xenografts derived from MCF7, MCF7-PELP1WT and MCF7-PELP1cyto models demonstrated that PELP1 signaling modulates mTOR signaling in vivo and inhibition of mTOR signaling rendered PELP1 driven tumors to be highly sensitive to therapeutic inhibition. Further, mTOR inhibitors sensitized tamoxifen therapy resistant PELP1cyto model cells to hormonal therapy. IHC analysis of mammary glands and mammary tumors from PELP1Tg mice revealed deregulation of mTOR signaling components with excessive activation of S6K and 4EBP1. Using breast tumor tissue arrays (n = 100), we found significant correlation of PELP1 cytosolic localization with mTOR signaling. Collectively, the experimental results from these studies identified PELP1-mTOR axis as a novel component of PELP1 oncogenic functions and suggests, mTOR inhibitor(s) will be effective chemotherapeutic agents for down regulating PELP1 oncogenic functions and for blocking PELP1-mediated therapy resistance.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-04-07.

P4-02-01: Bis(2-Ethylhexyl) Phthalate: A Potential Endocrine Disruptor Confer Letrozole Insensitivity and Induction of Aromatase Activity in Breast Cancer Cells

Exposure to endocrine disrupting compounds (EDC's) is an important determinant of mammary gland development and mammary tumor pathogenesis. The risk of breast cancer in adulthood is known to be influenced by environmental factors experienced as a fetus. Fetal exposure to dietary factors or certain pharmaceuticals and environmental chemicals that affect or mimic steroid hormones increase predisposition to breast cancer. The mechanisms by which EDC's alter epigenetic programming, differentiation and deregulation of ductal branching of mammary glands are poorly understood. A high ratio of estrogen receptor a (ERα) to ERβ has been recently found to be associated with poor prognosis and aggressive disease in breast cancer patients. Preliminary studies from our laboratory revealed that bis(2-ethylhexyl) phthalate (DEHP) is a possible EDC which induces cell proliferation in T47D, MCF7, MCF7/Aro breast cancer cells in vitro and confers insensitivity to letrozole, a third generation aromatase inhibitor. DEHP increased cell proliferation (MTT assay) in a dose dependent manner and was non toxic to T47D, MCF7 and MCF 7 Aro cells. 1, 10 and 100 nM concentrations of DEHP up regulated ERα and down regulated ERβ at the mRNA level. Hypermethylation in the estrogen receptor beta (ERβ) promoter was observed after treatment with 1nM DEHP for 24 h, suggesting that DEHP alter epigenetic programming through changes in the DNA methylation to modify the chromatin structure and change the accessibility of DNA to transcription factors. When breast cancer cells were treated with letrozole (200nM and DEHP (1nM) together, they survived, whereas those treated with letrozole alone did not survive. Aromatase mRNA and enzyme levels were higher in the DEHP treated cells by comparison with sham control MCF7/Aro cells. Nonmalignant MCF-10A breast epithelial cells showed a proliferation advantage (MTT assay) by up regulation of ERα as well as aromatase expression when treated with 1nM DEHP. Aromatase transgenic mice treated with 10mg/Kg b.wt of DEHP over a period of 30 days resulted in the excessive ductal branching density and epithelial outgrowth in the mammary gland. The present data suggest that dietary accumulation of DEHP through plastic food containers, water bottles, etc. may contribute to risk of hormone sensitive breast cancer in women and chemoinsensitivity and or drug resistance in breast cancer patients.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-02-01.

P4-02-08: Obesity-Induced Aromatase Expression in the Breast Microenvironment Promotes Estrogen Receptor Activity Independent of Circulating Estradiol Levels

Epidemiological studies indicate that obesity increases the risk of postmenopausal breast cancer by approximately 50%. In the past, researchers have hypothesized that elevated estrogen synthesis by the peripheral adipose tissue may be the principal mediator of breast tumorigenesis in this population, which primarily develops estrogen receptor alpha (ERα) positive breast cancer. However, obesity is also accompanied by an elevation in growth factor and cytokine signaling, and these pathways have been linked to tumorigenesis. In addition, certain growth factor and cytokine family members can promote aromatase expression in both the epithelial and stromal tumor compartments. Consequently, we hypothesized that obesity increases the risk of postmenopausal breast cancer via elevated aromatase expression and/or activity in the local mammary tissue.

To test our hypothesis, we investigated how ERa activity in mammary epithelial cells was influenced by adipose stromal cells (ASC) cultured under obesity-associated conditions, including high cell density and exposure to elevated levels of circulating growth factors and cytokines. For the latter condition, sera was obtained from postmenopausal women, pooled by BMI category (lean: 18.5−24.9; obese: ≥30), and applied to the ASC, which were originally derived from women undergoing reduction mammoplasty. High ASC density was achieved via the protocol previously published by Dr. Li. Preliminary data indicated that both elevated cell density and sera from obese postmenopausal women induces greater aromatase expression in ASC, indicating that multiple factors may be contributing to the increased local aromatase expression seen with obesity. We are currently exploring the signaling pathways responsible for obesity's upregulation of ASC aromatase expression and will present these results at the meeting. Intriguingly, exposure to conditioned media from both the high density and obese sera-exposed ASC enhanced ERa activity in MCF-7 mammary epithelial cells, independent from exogenous estradiol but dependent on the presence of androgens, suggesting an important role for the aromatase enzyme in this observation. To expand on this finding, we plan to investigate the effect of ASC conditioned media on different markers of cancer aggression, including proliferation and survival, and assess the degree to which these effects depend on estradiol. Through further examination of obesity's impact on signaling pathways in both the epithelial and stromal tumor compartments, we ultimately hope to identify more effective chemopreventive and therapeutic regimens for the high-risk obese postmenopausal population.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-02-08.

P4-03-05: Development of an Inducible Estrogen Receptor Co-Activator PELP1 Mammary Tumor Model

Despite treatment advances, breast cancer remains the second most lethal malignant disease for women worldwide. Given the importance of estrogen receptor (ER) and hormone-dependent nature of breast cancer, pharmacologic agents were developed to either modulate ER functions or reduce circulating estrogens levels. Although targeted endocrine therapies significantly reduce mortality in patients with estrogen sensitive (ER+) tumors, both de novo and acquired resistance limits efficacy. A critical need for identifying more precise diagnostic/prognostic biomarkers and novel therapeutic targets prompted deeper investigation into ER-coregulatory protein function and regulation. ER-coactivator PELP1, mediates both nuclear and extra-nuclear estrogen signaling and crosstalk with growth factors. PELP1 is deregulated in hormone-driven cancers, associates with undifferentiated invasive breast adenocarcinomas and an independent prognostic biomarker in assessing clinical outcome of luminal-like breast cancer patients. Collectively, several studies suggest PELP1 is an ERα coregulator with tumorigenic potential. However, the in vivo significance of PELP1 deregulation during initiation and progression of breast cancer is unknown. To determine the role of PELP1 overexpression in mammary tumorigenesis, we generated an inducible transgenic murine model. Transgene construct (pTetOPELP1) consists of a full-length human PELP1 cDNA linked to luciferase gene reporter through an internal ribosomal entry site (IRES). PELP1 transgene was purified and microinjected into mouse zygotes to generate pTetOPELP1 mice. Founder mice were identified by Southern blot analysis, of genomic DNA extracted from tail biopsies, for transgene integration through germline transmission. pTetOPELP1 mice were breed with mammary gland-specific rtTA mice (MMTVrtTA) to produce MMTVrtTA-TetOPELP1 bitransgenic mice. Potential founder mice were identified by polymerase chain reaction and breed to establish two independent transgenic lines. Transgene expression was induced in adult female bitransgenic animals with 200mg/mL of doxycycline administered in drinking water. Concurrent expression and activity of the luciferase gene reporter was detected specifically in the mammary gland by in vivo bioluminescence imaging, luciferase assay and RT-PCR. Mammary epithelial-specific expression of PELP1 was validated by immunohistochemistry and Western blot analysis. PELP1-mediated morphological and histological changes were analyzed by examining carmine-stained whole mounts and H&E-stained mammary glands sections. Our early findings with MMTVrtTA-TetOPELP1 bitransgenic mice (n=30) early preneoplastic changes and hyperplasia were evident as early as 12 weeks and the formation of mammary tumors by 8 months of age following PELP1 induction by doxycycline treatment. By utilizing the tetracycline-regulatory system, we created a novel, inducible and mammary gland-specific PELP1-expressing transgenic model for future in vivo studies into molecular mechanisms of PELP1-mediated mammary tumorigenesis.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-03-05.

Modeling ductal carcinoma in situ: a HER2-Notch3 collaboration enables luminal filling

A large fraction of ductal carcinoma in situ (DCIS), a non-invasive precursor lesion of invasive breast cancer, overexpresses the HER2/neu oncogene. The ducts of DCIS are abnormally filled with cells that evade apoptosis, but the underlying mechanisms remain incompletely understood. We overexpressed HER2 in mammary epithelial cells and observed growth factor-independent proliferation. When grown in extracellular matrix as three-dimensional spheroids, control cells developed a hollow lumen, but HER2-overexpressing cells populated the lumen by evading apoptosis. We demonstrate that HER2 overexpression in this cellular model of DCIS drives transcriptional upregulation of multiple components of the Notch survival pathway. Importantly, luminal filling required upregulation of a signaling pathway comprising Notch3, its cleaved intracellular domain and the transcriptional regulator HES1, resulting in elevated levels of c-MYC and cyclin D1. In line with HER2-Notch3 collaboration, drugs intercepting either arm reverted the DCIS-like phenotype. In addition, we report upregulation of Notch3 in hyperplastic lesions of HER2 transgenic animals, as well as an association between HER2 levels and expression levels of components of the Notch pathway in tumor specimens of breast cancer patients. Therefore, it is conceivable that the integration of the Notch and HER2 signaling pathways contributes to the pathophysiology of DCIS.

Abstract P4-06-01: Significance and Therapeutic Potential of PELP1 in ER-Negative Breast Cancers

Background: During the past 20 years, studies have extensively focused on the role of estrogen receptor (ER) and progesterone receptor (PR) in breast cancer. Even through ER and PR explain the biology of ER-positive tumors, it remain unknown as to what drives ER-negative metastatic tumors. Recent advances implicated potential importance of several additional nuclear receptor (NRs) including ERRα, AR, GR, and PPAR in breast cancer. NR action is complex, requires functional interactions with coregulators, and deregulation of coregulators occur during cancer progression. As a modulator of multiple NR functions, coregulators are likely to play a role in breast cancer progression to metastasis. Recent studies indicated that metastatic tumors have increased expression of corgulators. Proline glutamic acid rich protein (PELP1) is a NR coregulator, and its expression is upregulated during breast cancer progression. The objective of this study is to examine whether proto-oncogene PELP1 contributes to metastatic potential of ER-negative breast cancer cells and to test whether blocking of PELP1 signaling axis will have therapeutic effect.

Methods: We have used two ER-negative model cells; (1) MDA-MB231 cells that facilitate study of bone and lungs metastasis of breast cancer cells using Nude mice models, (2) 4T1 cells, a clinically relevant model of spontaneous breast cancer metastasis that facilitate tumor growth studies using syngenic mice. To establish the significance of PELP1 axis, we have established clones stably expressing PELP1-shRNA (MDA-MB231- PELP1 shRNA, 4T1-PELP1 shRNA). Proliferation was measured using CellTiter-Glo assays. Role of PELP1 on metastasis was studied using Boyden chamber, wound healing, invasion and MMP assays. Epithelial to Mesenchymal Transition (EMT) real time qPCR Array (Super array) was used to identify PELP1 target genes and targets were validated using ChIP assays. Nude mice based assays were performed to study the role of PELP1 on in vivo metastasis.

Results: MDA-MB231 and 4T1 cells expressing PELP1-shRNA showed decreased PELP1 expression (∼75% of endogenous levels) and exhibited decreased propensity to proliferate in in vitro growth assays. Boyden chamber and wound healing assays showed PELP1 down regulation substantially affect migratory potential of MDA-MB231 and 4T1 cells. PELP1 shRNA model cells showed alterations in the expression of the EMT markers. EMT array studies identified eight genes involved in the EMT (including MMPs, E-cadherin, MTA1) as PELP1 potential target genes and ChIP studies showed PELP1 recruitment to these gene promoters. Overexpression of PELP1 in nonmetastatic cells increases their propensity for metastasis in vivo, while, PELP1 knockdown in metastatic model cells decreased their metastatic potential. Nanopartiles delivering PELP1-siRNA significantly affected the growth and metastatic potential of ER-ve cells.

Conclusions: These results suggest that PELP1 play a role in ER-ve breast cancer metastasis by promoting cell motility and EMTand blockage of PELP1 axis reduces metastasis potential of ER-negative breast cancer cells. Understanding how NR coregulator PELP1play a role in metastasis will be useful in maximizing treatment opportunities for metastatic breast cancer. This study is funded by Komen grant KG091267.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-06-01.

Abstract P5-03-01: Role of Aromatase and Its Inhibitor in Breast Cancer-Induced Tumorigenesis and Bone Metastasis

Aromatase (Aro) is the rate-limiting enzyme that catalyzes the final step in estrogen (E2) biosynthesis. An important strategy to treat hormone-dependent BCa is suppression of estrogen receptor (ER) action by antiestrogens or aromatase inhibitors (AI). Letrozole is a very specific and potent AI. In postmenopausal women, the ovaries cease to make E2 but concentration of E2 in their BCa tissue are maintained at a certain level for survival and proliferation of BCa cells, which is dependent on local E2 formation catalyzed by Aro. Although BCa cells have been shown to express Aro, the local E2 is largely produced by adipose stromal cells in the breast. This raises the question of how ER positive (ER+) metastatic BCa cells survive after they enter blood circulation, where E2 level is very low.

We cultured human ER+ BCa CAMA-1, Aro-transfected MCF-7 and ZR-75-1 (ZR) cells in suspension to mimic circulating BCa cells. Interestingly, suspension culture increased Aro expression, suggesting circulating ER+ BCa may up-regulate intracrine E2 activity for survival after leaving the E2-rich adipose stroma at primary site. The expression of Aro also enhances cell proliferation and supplementation of testosterone (T), the substrate of Aro, stimulates this proliferation further. Notably, while these cells show an increased rate of apoptosis in suspension than in adherent culture, addition of T in suspension culture significantly suppressed the rate of apoptosis and addition of letrozole blocked the T-induced cell survival in suspension culture. To investigate the importance of intracrine E2 in promoting tumorigenesis and metastasis, we implanted Aro-expressing ZR cells orthotopically and intracardiacally (I.C.) into female athymic mice; vector-transfected ZR cells were used as control. While control ZR cells were incapable of forming tumors without E2 supplementation, Aro-expressing cells generated orthotopic tumors with no E2 supplementation after 3-weeks of inoculation. More interestingly, mice with I.C. inoculated Aro-expressing cells also presented distant bone metastasis in the mandible and tibiae/femora after 2-weeks of inoculation, detected by whole mouse fluorescence and bioluminescence imaging as the cells were stably transfected with a luciferase and GFP expression vector. To determine whether growth of orthotopic tumors can be inhibited by systemic administration of an AI, we treated the mice in one group with letrozole at 10 mg/mouse/day and the other group with the vehicle as control after the average tumor volume reached 150 mm3. After 3-weeks, the tumor burden in the letrozole treatment group reduced significantly while tumor burden in the control group increased continuously. Our studies show that suspension culture increases expression of Aro mRNA in several ER+ BCa cell lines, which likely results in increased intracrine E2 signaling and contributes to the survival of these BCa cellsin suspension. This provides a mechanistic insight into how ER+ BCa cells may survive the low E2 condition in circulation and subsequently induce distant metastasis as observed in the I.C. model. Our study provides an important foundation for future investigation on how hormone-dependent BCa cells up-regulate Aro expression in circulation and induce bone metastasis.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-03-01.

Abstract P4-02-10: Significance of ER-Coregulator-Src Axis in Hormonal Resistance

Background: The estrogen receptor (ER) is implicated in the progression of breast cancer. Endocrine therapy using Tamoxifen, a selective estrogen receptor modulator (SERM), improves disease-free survival in postmenopausal women. Despite positive effects, initial or acquired resistance to endocrine therapies frequently occurs. Recent studies suggested the presence of alternative signaling pathways (including HER2 and c-Src kinase) that contribute to ER activation in the absence of estrogen. ER-coregulators play an essential role in hormonal responsiveness and coregulators such as PELP1 couples Src axis to ER thus representing a new pathway for targeted drug therapy. In this study, we examined the therapeutic efficacy of targeting the PELP-Src axis in blocking therapy resistance.

Methods: Three breast cancer model cell lines with resistance to Tamoxifen were used in this study: (1) MCF7-PELP1 (2) MCF7-HER2/neu and (3) MCF7-Tam. To establish the significance of ER-PELP1 coregulator-Src axis, we have generated additional model cells that stably express Src-ShRNA (MCF7-PELP1 -Src-shRNA and MCF7-HER2-SrcshRNA). Model cells were tested for proliferation using CellTiter-Glo assays, anchorage dependence and ER-extranuclear signaling by Western analysis using phospho-antibodies. Orally soluble Src inhibitor Dasatinib (SPRYCEL)was used to test whether it (a) blocks of ER-coactivator-Src signaling and (b) sensitizes the resistant breast cancer cells to endocrine therapy. Pre-clinical nude mice xenograft based studies were performed to validate the effect of Dasatinib alone or in combination with tamoxifen in vivo. IHC analysis of the tumors was performed to examine the effect of Dasatinib on ER signaling components.

Results: Src knock down or Dasatinib (100 nM) treatment substantially inhibited the growth of MCF7-PELP1, MCF7-HER2/neu and MCF7- Tam model cells in proliferation assays. Depletion of Src using siRNA substantially reduced E2 mediated activation of Src, MAPK and AKT in resistant model cells. In post-menopausal xenograft based studies, treatment with Dasatinib significantly inhibited the growth of therapy resistant cells. IHC analysis revealed that the tumors are ER positive, and Dasatinib (15 mg/kg/d) treated tumors exhibited alterations in Src and AKT pathways. Combinatorial therapy of Tamoxifen (100 μg/mouse/day) with Dasatinib showed better therapeutic effect compared to single agent therapy on the growth of therapy resistant tumors.

Conclusions: The results from this study showed that ER-PELP1 coregulator-Src axis play an important role in promoting hormonal resistance and blocking this axis prevents the development of hormonal independence in vivo. ER coregulator PELP1 and Src kinase are commonly deregulated in breast cancers therefore combination therapies using both endocrine agents and Dasatinib may have better therapeutic effect by delaying the development of hormonal resistance This study is supported by DOD grant W81XWH-08-1-0604.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-02-10.

Potential Role of Pargyline in Overcoming Adaptive Resistance in Breast Cancer Cells

Background: Estrogen-induced breast carcinogenesis is shown to be characterized by global changes in histone modifications. LSD1 (KDM1), a histone demethylase enzyme, play a key role in establishing specific histone methyl marks at target gene promoters. Recent evidence suggest that LSD1 is recruited to a significant fraction of estrogen receptor (ER) target genes and is required to demethylate proximal histones to enable productive ER transcription. These emerging findings also suggest that deregulation of LSD1 epigenetic pathway could contribute to hormonal independence and adaptive resistance in breast cancer cells. In this study, we examined the therapeutic efficacy of treating breast tumor cells with Pargyline, an FDA approved drug for blocking LSD1 functions, and evaluated the therapeutic benefit.Methods: To test this hypothesis, we used model cells that acquired resistance to hormonal therapy including (a) MCF7-HER2 that overexpress oncogene neu/HER2, (b) MCF7-Tam that have acquired resistance to Tamoxifen, (c) MCF7-Ca-LTLT cells that have acquired resistance to Letrozole, (d) MCF7 cells that overexpress proto-oncogene PELP1 (MCF7-PELP1). Parental MCF7 cells were used as a control. Cells were treated with LSD1 inhibitor Pargyline either alone or in combination with Letrozole and Dasatinib. Activation of ER genomic functions was studied using luciferase reporter gene assays. Epigenetic modifications at target promoters were analyzed by Chromatin immune precipitation (CHIP) assays using H3 methyl (di and Tri -H3K4, -K9) specific antibodies. Biological significance and hormonal therapy sensitivity was measured by in vitro cell proliferation assays. Xenograft studies were used to validate the drug effect in vivo. Pilot studies were performed for delivery of drug combinations using nanoparticle formulation.Results: Reporter gene assays showed that LSD1 has potential to enhance ER mediated transcription. LSD1 functionally interacts with ER coregulator PELP1 and is recruited to ER target genes. Pargyline substantially inhibited ER transactivation functions. ChIP analysis revealed that aggressively growing breast cancer cells and therapy resistant cells have distinct activating histone methyl modifications at growth regulatory ER target genes. Treatment of breast cancer models with LSD1 inhibitor Pargyline facilitated reversal of these specific modifications and thereby inhibited the growth of breast cancer cells in vitro and in vivo models. Combinatorial therapy using three agents; (a) that block Estrogen receptor genomic actions (Tamoxifen or Letrozole), (b) ER nongenomic actions (Dasatinib) and (c) ER epigenetic modifications (Pargyline) showed the most promising therapeutic effect compared to single agent therapy on the growth of therapy resistant cells.Conclusions: Our results suggest that histone methyl modification plays a role in therapy resistance and validates the therapeutic potential of Pargyline in combinational therapies. Collectively, these results suggest that targeting LSD1 axis with Pargyline in combination with current endocrine therapies will have better therapeutic effect and may inhibit or delay development of hormonal resistance, thus providing major benefits to patients care. This study is funded by Komen grant KG090447.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 409.

mTOR Inhibition and Diet Induced Obesity in a Mouse Model of Postmenopausal Breast Cancer

Background:Breast cancer is the most common type of noncutaneous cancer among white women. It is more frequently diagnosed after menopause, and the majority of cases are estrogen receptor positive (ER+). Obesity is associated with poor prognosis, increasing risk by 50% in post-menopausal women, and correlates with shorter disease-free and overall survival. Unfortunately, the mechanism underlying the poorer outcomes in obese breast cancer patients is not known. The majority of ER+ tumors present with genomic ER activity; however, nongenomic ER activity can also occur, resulting in interaction with growth factor (GF) receptors.In the obese state nongenomic activity may be especially enhanced, promoting ER and GF signaling crosstalk, breast tumor cell growth and survival. Since Akt/mTOR signaling has been implicated in breast cancer, and obesity (through activation of GF signaling pathways) can activate this pathway, we hypothesized that the enhancement of tumor growth in response to obesity can be offset by mTOR inhibition. To test this we used a mouse model of postmenopausal breast cancer and investigated the effects of obesity (relative to lean and overweight phenotypes) with and without pharmacologic mTOR inhibition by RAD001.Methods:Ovariectomized C57BL/6 mice were randomized to diet regimens that induce either a lean, control (overweight), or a diet-induced obesity (DIO) phenotype. After 17 weeks on the diets, DIO mice were switched to the control diet and acclimated for 3 weeks. To determine diet-induced changes in adiposity, quantitative magnetic resonance (qMR) was performed at wk 18. At wk 21 mice were injected with syngeneic MMTV-Wnt-1 mammary tumor cells in the 4th mammary fat pad. Two weeks after tumor injection, the mice received RAD001 (10 mg/kg) or vehicle by oral gavage twice a week for 6 weeks.Tumor growth was measured weekly.Results:At week 17, mice in the DIO group were significantly heavier (42.8 g) than control (34.5 g) and lean mice (24.6 g) (p <0.001) and % fat was also higher (p<0.001) in DIO (54.5%) when compared to the control (42.2%) and lean (30.7%) groups.Tumor growth was different between the three diet regimens, confirming that dietary modulation directly influences MMTV-Wnt-1 tumor growth in a postmenopausal mouse model of breast cancer. DIO mice displayed significantly enhanced tumor growth (p<0.05) when compared to the control and lean mice. Overall, RAD001 was effective at decreasing tumor growth in all diet groups (p<0.01). However, the relative effect of RAD001 versus placebo was diminished in DIO mice compared to control and lean mice, suggesting obese mice may be partially resistant to RAD001. This resistance was overcome in the DIO mice by increasing the RAD001 dose to 15 mg/kg.Conclusion:Our results confirm that DIO increases tumor growth in the context of postmenopausal breast cancer. In addition, treatment with the mTOR inhibitor RAD001 reversed the mammary tumor enhancing effects of obesity (particularly at the higher dose of RAD001), further supporting mTOR as an important molecular target for breaking the obesity-breast cancer link.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5077.

Targeting Aldose Reductase: A Novel Strategy in Treating Endocrine Resistance Using Combination Therapy

Breast cancer is the most commonly diagnosed form of cancer in women. Among breast cancer patients about 2/3 are initially hormone sensitive or estrogen receptor (ER) positive and respond to endocrine therapy. Aromatase inhibitors (AI's) are superior class of hormonal therapeutic agents effectively control ER positive breast cancer in postmenopausal women. Acquired resistance to AI's is expected to be an emerging serious problem in clinics and recent studies have shown that tumors use adaptive signaling mechanisms to overcome AI sensitivity. Thus there is an urgent need for newer treatment modalities. Combination of endocrine and non endocrine agents that block these signaling pathways may prevent or delay the adaptive mechanism and thereby onset of resistance to hormonal therapy. In our study we have found that Fidarestat, an aldose reductase (enzyme which catalyzes the rate limiting step of glucose to fructose or sorbitol formation in polyol pathway) inhibitor effectively re-sensitize letrozole resistant LTLT-Ca breast cancer cells to letrozole. 1µM of fidarestat + 1uM letrozole was found very effective in inducing maximum cell death in LTLT-Ca cells when compared to fidarestat alone. The combination treatment not only restored ER-α levels but also down regulated HER2/MAPK signaling proteins. Aldose reductase siRNA (100nM)- treated MCF-7/Aro and MCF-7 cells upregulated ER-α in western blot and ER-functionality assays. On the other hand in aldose reductase-siRNA- treated LTLT-Ca cells, ER-α levels were down- regulated as in fidarestat treatment. Pretreatment of LTLT-Ca with fidarestat for one week showed reduced proliferation of cells and the effect was maintained until four passages with 1µM letrozole alone. Fidarestat treatment up-regulated E2-mediated transcription in LTLT-Ca cells. In order to enhance the efficacy and targeted delivery of fidarestat in LTLT–Ca cells we have used a nanoparticle-based therapeutic formulation. Folate receptor, highly expressed on epithelial carcinomas, could be a potential molecular target for tumor selective drug delivery. Physcio-chemically well characterized Fidarestat–folate nanoparticles (FFNP's) were prepared to increase the tumor selective intracellular delivery. FFNP's were found superior in exerting cytotoxicity when compared to fidarestat alone. Combination therapy was equally effective in controlling LTLT-Ca cell growth using xenograft model. Taken together, the increased glucose metabolism in LTLT-Ca cells may be critically contributing to chemotherapeutic resistance by increasing drug metabolism and decreasing uptake. Hence targeting aldose reductase in endocrine resistance may be attractive alternative to increase the sensitivity of hormonal therapy.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 67.

Effects of obesity on anastrozole response in a mouse model of postmenopausal breast cancer

Abstract #1146

Background: The prevalence of obesity, an established breast cancer risk factor for postmenopausal women, has risen rapidly in the US in recent decades. The majority of postmenopausal breast tumors are estrogen receptor-α positive (ER-α+) and responsive to the mitogenic effects of estrogen. Tamoxifen, a selective estrogen receptor modulator, has been the endocrine agent of choice for the treatment and prevention of ER-α+ breast cancer. Unfortunately, resistance to tamoxifen develops in the majority of cases. Akt activation in breast tumors is associated with poor prognosis and resistance to tamoxifen and other forms of endocrine therapy. Akt activation in the mammary epithelium is also enhanced by obesity, possibly due to elevated growth factor and hormone levels known to activate the PI3K/Akt/mTOR pathway. Aromatase inhibitors, such as anastrozole, are emerging as the treatment of choice for the postmenopausal patient, yet little is known as to how obesity may modulate response to these agents. In this study we examined the effect of obesity on tumor growth response to anastrozole and local tumor aromatase expression. We also assessed the correlation between obesity, Akt activation and tumor growth.
 Methods: To mimic postmenopausal obesity, ovariectomized C57BL/6 mice (n=80) were randomized to a control diet (10 Kcal% fat; ∼10.2 kcal/day) or a diet-induced obesity (DIO) regimen (60 Kcal% fat; ∼14.4 kcal/day). After 14 wk on the diets mice were injected with isogenic MMTV-Wnt-1 mammary tumor cells (5x104 cells/mouse) in the 4th mammary fat pad. After tumors became palpable mice were injected with the AI anastrozole (10 μg/day s.c.) or vehicle control (0.3% hydroxypropylcellulose) for 4 wk. Serum leptin and resistin were measured at the end of the study, RT-PCR and western blot analyses were used to determine aromatase gene expression and total and phosphorylated protein levels in the tumors.
 Results: Mice on the DIO regimens were significantly heavier (39.2 g ±0.7) than controls (29.7 g ±1.23), with significantly higher circulating levels of the obesity-related adipokines leptin and resistin. Tumors from DIO mice, relative to controls, displayed increased aromatase expression. Anastrozole had no effect on food consumption or body weight but intriguingly increased aromatase expression in tumors from both control and DIO mice. Importantly, DIO mice, relative to controls, were much less responsive to the tumor inhibitory effect of anastrozole. Akt protein expression correlated positively with tumor weight, regardless of dietary or hormonal treatment.
 Conclusion: In the context of postmenopausal breast cancer, our results suggest that obese mice compared to controls are less responsive to the effects of anastrozole on tumor growth and that aromatase expression in tumors is higher in obese mice regardless of anastrozole treatment. We also found a strong correlation between Akt activation and tumor growth, irrespective of diet or hormonal treatment.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1146.

Novel mouse model for studying role of ER-nongenomic actions in breast cancer

Abstract #601

Back ground: Estradiol (E2) and estrogen receptor (ER) signaling play a key role in development and progression of breast cancer. ER signaling is complex, involves coregulatory proteins and the status of ER coregulators in tumor cells plays an important role in hormonal responsiveness and tumor progression. In addition, ER also participates in non-genomic signaling events in the cytoplasm, however the significance of non-genomic signaling in mammary tumorigenesis remain unknown. PELP1/MNAR is novel ER coregulator that participates in ER genomic and non-genomic actions. PELP1 expression is deregulated in breast tumors and in a subset of tumors PELP1 is predominantly localized in the cytoplasm. Since PELP1 cytoplamsic localization promotes excessive activation of Src and AKT pathways, we hypothesized that PELP1 mediated excessive activation of ER-nongenomic functions may play a role tumorigenesis. To test this, we have generated MMTV-PELP1cyto TG model that uniquely express PELP1 in the cytoplasm of mammary glands that mimics the pathological situation of PELP1 localization seen breast cancer.
 Methods: As a means of targeting the expression of the PELP1 transgene to the mammary gland, we placed the PELP1cyto cDNA under the control of the MMTV promoter. PELP1 transgene integration was verified by PCR and expression levels by Western and IHC in each founder line. Whole-mount preparations and IHC analysis was performed using Tg and age controlled wild type littermates from different developmental stages. Total protein extracts of mammary gland were used for western blot analysis of nongenomic signaling components.
 Results: Preliminary analysis of mammary gland from PELP-cyto mice showed hyperplasia, increased proliferation as analyzed by PCNA staining. Mammary tumors were observed as early as 32 weeks. No spontaneous mammary tumors were found in the wild type cohort. Pathological analysis revealed that these tumor masses represent full blown mammary adenocarcinomas. Mammary tumors showed excessive activation of nongenomic signaling including activation of Src and AKT pathways. A clear induction of aromatase expression was found in PELP1 tumors compared with the wild-type that showed no aromatase expression in the mammary gland.
 Discussion: We have established and characterized a transgenic mouse model that mimics deregulated ER-nongenomic signaling. Our results suggest that PELP1 is a proto-oncogene and demonstrates its in vivo tumorigenic potential. PELP1 driven tumors are ER+ve, express aromatase, thus provide an interesting in vivo model for studying ER-mediated tumorigenesis and to study effect of local E2 on ER-mediated tumorigenesis.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 601.

Potential role of estrogen receptor coregulator in mitosis

Abstract #5036

Background: Estrogen stimulates breast tissue to increase cell divisions (mitosis) and is implicated in breast cancer progression. ER action is complex and requires functional interactions with coregulators. Proline-, glutamic acid-, and leucine-rich protein (PELP)-1, also known as modulator of nongenomic actions of estrogen receptor (MNAR), is a novel nuclear receptor (ER) coregulator with multitude of functions. Emerging evidence suggest that PELP1 expression is deregulated in breast cancer and serves as a scaffolding protein that couples various signaling complexes with estrogen receptor. In this study we found that ER coregulator PELP1 plays a novel role in mitosis.
 Material and Methods: To understand the mechanism by which ER coregulator PELP1 contribute to breast cancer progression, we have utilized small RNA interference methodology and established breast cancer model cells that stably express PELP1-shRNA (MCF7-PELP1shRNA). FACS analysis was used to determine the cell cycle status of the model cells. Using confocal microscopy, immunoprecipitation, in vitro kinase assays, site directed mutagenesis and Western analysis using phospho-antibodies we studied the mechanism and significance of PELP1 signaling in mitotic progression. We also developed PELP1 siRNA nanoparticles and used them as well as CDK1 inhibitors in cell proliferation studies.
 Results: Down regulation of PELP1 expression resulted in decreased estrogen mediated cell proliferation, delayed mitotic progression and induced accumulation of mitotic cells. Interestingly, PELP1 depleted cells also exhibited multinucleation. Western analysis of various markers of mitotic progression revealed a delay in the kinetics of G2M initiation and progression. Confocal analysis revealed colocalization of CDK1 and PELP1 in G2M. Immunoprecipitation assays demonstrate that endogenous CDK1 form functional complex with PELP1 and Src kinase during mitosis. Using deletion and mutagenesis approach, we have mapped the putative CDK1 phosphorylation sites on PELP1. Down regulation of PELP1 or overexpression of PELP1 mutants (that cannot be phosphorylated by CDK1), reduces the magnitude of Src activation, which is an essential driving force for timely progression of M phase. PELP1 siRNA nanoparticles alone or in combination with CDK1 inhibitors have shown to significantly reduce the proliferation of breast cancer cells and showed increased response in tamoxifen resistant breast cancer cells.
 Discussion: These results suggest that ER coregulator PELP1 play a novel role in G2M progression. Since PELP1 expression is deregulated in breast cancer, PELP1 ability to regulate mitosis could contribute to the progression of cancer by causing genomic instability through the deregulation of mitosis. Taken together our findings suggest that estrogen can promote neoplasia using coregulators by two distinct mechanisms (1) Coregulator induction of target genes and (2) Coregulator mediated actions in mitosis. ER coregulator PELP1 play multiple roles in Estrogen mediated neoplasia, and thus represent a target for novel therapeutic breast cancer strategies by forming the “next generation” of antimitotic drugs.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5036.

Preclinical modeling of endocrine response: a combination therapy approach with the ERβ agonist, diarryl propionitrile and letrozole restores sensitivity to letrozole-resistant breast cancer cells

Abstract #17

The majority of breast cancer patients are postmenopausal women with estrogen receptor-positive (ER+) tumors. Approximately 66% of breast carcinomas contain aromatase. Aromatase inhibitors are proving to be more effective than tamoxifen in the treatment of postmenopausal women with ER+ breast cancer. However, the development of resistance to treatment is a concern. The transition of the ER+ tumors from a responsive to unresponsive state is associated with different molecular pathways. We have therefore investigated the properties of resistance that develops in response to the aromatase inhibitor letrozole in the preclinical MCF-7-aromatase xenograft animal model following long-term treatment with letrozole by using the derived letrozole-resistant MCF-7-aromatase LTLTca breast cancer cells. The combination treatment of letrozole and the ERβ agonist diarryl propionitrile (DPN) restored sensitivity to letrozole in the letrozole-resistant LTLTca cells. Studies from our group using this postmenopausal breast cancer preclinical model clearly showed the therapeutic advantage of the ERβ agonist in overcoming unresponsiveness to letrozole. A 67% reduction in tumour size was observed in the group of animals bearing the letrozole-resistant LTLTca tumors that received the combination of letrozole and DPN. A novel delivery method using letrozole-DPN nanoparticles showed enhanced sensitivity (∼80%) to the combination nanoparticles. Letrozole was found to be relatively ineffective in these animals with only a 36% reduction in tumor size with tumors having a mean tumor weight of 0.95g by the end of four weeks of treatment. Biochemical analysis showed a reduction in the tumor aromatase enzyme levels in mice treated with letrozole + DPN when compared to letrozole alone. QRT-PCR as well as protein analysis studies of the letrozole-resistant LTLTca tumors showed a decrease in P27 levels and elevated expression levels of HER-2. Expression levels of cyclin D1 and the ERα to ERb ratio was higher in the untreated letrozole-resistant tumors compared to tumors that responded to the combination therapy. These findings provide further support for the development and testing of novel therapeutic approaches for selective regulation of ER-dependent (ERα and β) actions. Combination treatments involving agents that modulate ERβ activity may provide therapeutic advantage in the treatment, for overcoming resistance to estrogen-ablation and prevention of breast cancer.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 17.

Therapeutic targeting of the c-fms oncogene diminishes the growth of breast cancer cells and ductal hyperplasia in the mammary gland of the CSF-1 transgenic mouse model

Abstract #3120

The macrophage colony-stimulating factor (CSF-1) is a cytokine produced by macrophages as well as epithelial cancer cells. By signaling via its receptor c-fms, CSF-1 induces growth/survival pathways in breast cancer cells. Defects in mammary gland development were observed in mice deficient in CSF-1/c-fms signaling, implicating this pathway in normal mammary development as well. In breast cancer, elevated levels of both CSF-1 and c- fms have been detected, with 80% of invasive breast carcinomas abnormally expressing c-fms. To study the role of CSF-1 signaling in breast cancer, we have previously generated mammary specific transgenic mouse models that over-express these factors (termed MMTV-CSF-1 and MMTV-c-fms). Both these transgenic mouse strains developed ductal hyperplasia and dysplasia as well as tumor formation. Our previous evidence also showed increase in cellular proliferation factors such as Cyclin D1 and PCNA in these mice. To examine which signaling pathways are altered in these mice, we have compared in this study the expression profile of target genes of signaling pathways in MMTV-CSF-1 mice and wild type mice using the Signal Transduction Pathway Finder RT-PCR array (Superarrray). Wnt signaling pathway was induced in the mammary gland of the MMTV-CSF-1 mouse strain compared to wild type, suggesting that this pathway may mediate CSF-1 signaling. In a proof-of-principle experiment, an MMTV-CSF-1 mouse was injected subcutanuously with neutralizing anti-c-fms antibody (Santacruz Biotech, 2-4A5) at a dose of 5 μg daily for 7 days. The treated mouse exhibited a decrease in the elevated ductal branching and hyperplasia that are characteristics of untreated MMTV-CSF-1 mice. This treatment also resulted in reversing many of expression alterations in MMTV-CSF-1 mice. For example, expression of the CSF-1 responsive gene Cyclin D1 was reduced by over 3-fold due to antibody treatment. Fas, the receptor for the pro-apoptotic factor Fas ligand, decreased by 5-folds in the MMTV-CSF-1 strain relative to wild type but increased 14-folds due to c-fms antibody treatment. The expression of the proapoptotic factor Bax increased about 4-fold, whereas the angiogenic factor Angiopoietin 1 was reduced by 60% due to anti-cfms antibody treatment. The treatment also reversed alterations in the expression of the wnt transcription factors Lef-1/TCF7. Because small molecule tyrosine kinase inhibitors that target c-fms, Gleevecâ (Imatinib, obtained from Novartis) and GW2580 (Calbiochem), are emerging, we examined their effects on the growth of SKBR3 breast cancer cells that express both CSF-1 and c-fms. Our data showed both these drugs inhibited the growth of SKBR3 cells, providing the rationale to test their effects on tumor formation and underlying biochemical effects in our transgenic preclinical models. The current studies warrant further investigation of treating breast cancer using antibody and small molecule drugs targeting CSF-1/c-fms signaling.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3120.

Akt-induced endocrine therapy resistance is reversed by inhibition of mTOR signaling

BACKGROUND

Resistance to endocrine therapy is a major impediment in breast cancer therapeutics. The Phosphatidylinositol-3-OH kinase (PI3K)/Protein kinase B (Akt/PKB) kinase signaling pathway has been implicated in altering breast cancer response to multiple therapies. How Akt modulates response is an area of significant clinical relevance.

METHODS

We have used an in vitro model to discern the effects of robust Akt activity on breast cancer cellular response to endocrine therapies.

RESULTS

High levels of Akt activity confer resistance to the aromatase inhibitor Letrozole (Let) and the selective estrogen receptor (ER) down-regulator Fulvestrant (ICI). Akt-induced resistance is not due to failure of these endocrine agents to inhibit estrogen receptor alpha activity. Instead, resistance is characterized by altered cell cycle and apoptotic response. Cotreatment with low concentrations of the mTOR inhibitor RAD-001 and either Let or ICI restores response of the resistant cells to levels observed in the responsive cells treated with either Let or ICI as a single agent.

CONCLUSIONS

Our preliminary findings in experiments with RAD-001 indicate that cotreatment with mTOR inhibitors and either Let or ICI reverses the Akt-mediated resistance and restores responsiveness to antiestrogens. Concurrent ER and mTOR inhibition is therefore an effective strategy to overcome growth factor-induced resistance and bears significant implications for optimal clinical development of these agents in breast cancer treatment.

Anti-aromatase chemicals in red wine

Estrogen synthesized in situ plays a more important role in breast cancer cell proliferation than does circulating estrogen. Aromatase is the enzyme that converts androgen to estrogen and is expressed at a higher level in breast cancer tissue than in surrounding noncancer tissue. A promising route of chemoprevention against breast cancer may be through the suppression of in situ estrogen formation using aromatase inhibitors. A diet high in fruits and vegetables may reduce the incidence of breast cancer, because they contain phytochemicals that can act as aromatase inhibitors. In our previous studies, we found that grapes and wine contain potent phytochemicals that can inhibit aromatase. We show that red wine was more effective than white wine in suppressing aromatase activity. Interestingly, our results from white wine studies suggest a weak inductive effect of alcohol on aromatase activity. On the other hand, the potent effect of anti-aromatase chemicals in red wine overcomes the weak inductive effect of alcohol in wine. Several purification procedures were performed on whole red wine to separate active aromatase inhibitors from non-active compounds. These techniques included liquid-liquid extraction, silica gel chromatography, various solid phase extraction (SPE) columns, and high performance liquid chromatography. An active Pinot Noir red wine SPE C18 column fraction (20% acetonitrile:water) was more effective than complete Pinot Noir wine in suppressing aromatase assay. This red wine extract was further analyzed in a transgenic mouse model in which aromatase was over-expressed in mammary tissue. Our gavaged red wine extract completely abrogated aromatase-induced hyperplasia and other neoplastic changes in mammary tissue. These results suggest that red wine or red wine extract may be a chemopreventive diet supplement for postmenopausal women who have a high risk of breast cancer. Further research is underway to purify and characterize the active compounds in red wine that are responsible for the inhibition of aromatase.

Aromatase overexpression transgenic mice model: cell type specific expression and use of letrozole to abrogate mammary hyperplasia without affecting normal physiology

Our recent studies have shown that overexpression of aromatase results in increased tissue estrogenic activity and induction of hyperplastic and dysplastic lesions in female mammary glands and gynecomastia and testicular cancer in male aromatase transgenic mice. Both aromatase mRNA and protein are overexpressed in transgenic mammary glands and its expression is not limited to epithelial cells. However, it is more in epithelial than in stromal cells. Our results also indicate aromatase overexpression-induced changes in mammary glands can be abrogated with very low concentrations of the aromatase inhibitor, letrozole. Low concentration of letrozole had no effect on normal physiology as indicated by no significant change in the circulating levels of estradiol and follicle stimulating hormone as well as no change in estrogen responsive genes such as the progesterone receptor and lactoferrin in the uterine tissue. These observations indicate that the expression of aromatase in both epithelial and stromal cells can influence the complex interactions of biochemical pathways leading to mammary carcinogenesis and that the aromatase inhibitor, letrozole can be used as chemopreventive agents without affecting normal physiology.

The effects of aromatase overexpression on mammary growth and gene expression in the aromatase x transforming growth factor alpha double transgenic mice

The transforming growth factor alpha (TGFalpha) and its receptor (EGFR) are expressed in many breast cancers. Typically, the progression of estrogen dependent primary breast cancers into a hormone-independent state, due to the loss of the estrogen receptor, is associated with increased levels of TGFalpha and EGFR, leading to aggressive breast carcinomas. The relationship between breast tumorigenesis and TGFalpha is evident in the transgenic mice overexpressing TGFalpha in the mammary glands. In the aromatase transgenic mice, the mammary glands exhibit preneoplastic developments but do not form frank tumors. To test the interactions between growth factor overexpression with tissue estrogen, we have crossed the aromatase transgenic mice with the TGFalpha transgenic mice to produce a double transgenic strain. The histological data for the mammary glands of aromatase x TGFalpha double transgenic mice show that these mice develop hyperplastic changes similar to the aromatase parental strain but no tumors are formed. Consistently, the expression of cyclin D1 and PCNA is diminished in the double transgenic strain as compared to the parental strains. In addition, the expression of TGFalpha, EGF and EGFR are also decreased in the double transgenic strain, suggesting that continuous estrogen presence in the tissue due to aromatase overexpression downregulates the expression of EGFR and its ligands.

Regulation of colony stimulating factor-1 (CSF-1) in endometrial cells: glucocorticoids and oxidative stress regulate the expression of CSF-1 and its receptor c-fms in endometrial cells

OBJECTIVE

To evaluate the regulation and expression of CSF-1 and its receptor c-fms in endometrial cells.

DESIGN

In vitro study.

SETTING

Research and teaching institution.

PATIENT(S)

None.

INTERVENTION(S)

In vitro experimental study.

MAIN OUTCOME MEASURE(S)

The effect of glucocorticoid and oxidative stress on the expression of CSF-1 and c-fms in endometrial cells.

RESULT(S)

Cultured nonmalignant EM42 cells not only express CSF-1 and c-fms but are also capable of responding to exogenous CSF-1. We have also seen that glucocorticoids can regulate the expression of CSF-1/c-fms in endometrial cells. Furthermore, this study shows that oxidative stress plays a significant role in the induction of CSF-1 and its receptor c-fms.

CONCLUSION(S)

The results suggest that CSF-1 may promote the growth of nonmalignant endometrial cells in both an autocrine and paracrine manner and that endometrial cells under oxidative stress induce CSF-1 and c-fms.

Acceleration of mammary neoplasia in aromatase transgenic mice by 7,12-dimethylbenz[a]anthracene

Our studies using the aromatase transgenic mice model have shown that early exposure of mammary epithelium to in situ estrogen as a result of overexpression of aromatase predispose mammary tissue to preneoplastic changes. Here, we hypothesize that the preneoplastic changes induced by mammary estrogen in aromatase transgenic females may be susceptible to environmental carcinogens like 7,12-dimethylbenz[a]anthracene (DMBA), and may result in the acceleration and/or increase in the incidence of breast cancer. Results presented in this study show that tumors appeared in 25% of the mice that were treated with DMBA and all treated transgenic animals had microscopic evidence of neoplastic progression. Control non-transgenic females did not have significant changes even after treatment with DMBA. Consistent with increased neoplastic changes in DMBA-treated aromatase mice, we have seen an increase in the expression of genes involved in cell proliferation and cell cycle. We have also seen changes in the expression of oxidative stress markers and changes in estrogen-mediated growth factors. These studies indicate that more than one event is required for tumor formation, and that early estrogen exposure leading to preneoplastic changes in the mammary epithelial cells increases susceptibility to environmental carcinogens that may result in acceleration and/or an increase in the incidence of breast cancer.

Suppression of aromatase (estrogen synthetase) by red wine phytochemicals

Estrogen promotes the proliferation of breast cancer cells. Aromatase is the enzyme that converts androgen to estrogen. In tumors, the expression of aromatase is upregulated compared to surrounding non-cancerous tissue. In this study, we found that wine contains phytochemicals that are capable of suppressing aromatase. Red wine was shown to be much more effective than white wine in the suppression of aromatase activity. Whole wine, lyophilized wine, and heat-treated extracts were examined for aromatase inhibition in a human placenta microsomal assay. C18 Sep-Pak cartridge (Waters Co.) separation of red wine extracts under an increasing acetonitrile (ACN) gradient found that the most active components were in the 20% ACN fraction, in that they inhibited the wild-type human placenta aromatase, wild-type porcine placenta and blastocyst aromatase in a dose-dependent fashion. The 20% ACN active fraction was heat stable and inhibited aromatase in a non-competitive manner. The aromatase-inhibitory action of red wine extracts was also examined with a transgenic mouse model in which aromatase is over-expressed in the mammary tissues. It was found that the intake of the 20% ACN fraction by gavage completely abrogated aromatase-induced hyperplasia and other changes in the mammary tissue. This is the first report demonstrating that wine, especially red wine, contains phytochemicals that can inhibit aromatase.

Overexpression of aromatase in transgenic male mice results in the induction of gynecomastia and other biochemical changes in mammary glands

Our previous studies have shown that overexpression of aromatase in mammary glands results in the induction of hyperplastic and dysplastic changes in female transgenic mice. In this study we show that overexpression of aromatase in male transgenic mice results in increased mammary growth and histopathological changes similar to gynecomastia. Increased estrogenic activity also results in an increase in estrogen and progesterone receptor expression in the mammary glands of transgenic males as compared to the nontransgenic males, as well as an increase in the expression of various genes involved in cell cycle and cell proliferation. We have also observed an increase in certain growth factors, such as bFGF and TGFbeta, as a result of aromatase overexpression in the male transgenic mammary glands. In order to obtain a better understanding of the biological significance of gynecomastia, a reliable model is necessary to explain the mechanisms and correlations associated with human cancers. This model, can potentially serve as a predictable and useful tool for studying gynecomastia, hormonal carcinogenesis and action of other carcinogens on hormone induced cancers.

Overexpression of aromatase leads to hyperplasia and changes in the expression of genes involved in apoptosis, cell cycle, growth, and tumor suppressor functions in the mammary glands of transgenic mice

Our previous studies have shown that overexpression of aromatase results in increased tissue estrogenic activity and induction of hyperplastic and dysplastic lesions in aromatase transgenic mammary glands. In this study, we have examined the effects of aromatase overexpression on biochemical changes in the aromatase transgenic mice. Our results show an increase in the expression of both estrogen and progesterone receptors, and their expression is maintained in the transgenic mammary tissue even without circulating ovarian estrogens. Our results also show an increase in the expression of several growth factors and cell cycle genes in the aromatase transgenic mammary glands, which is consistent with the observed increase in proliferating cell nuclear antigen levels and cellular proliferation. Interestingly, we have also observed a decrease in the expression of epidermal growth factor receptor and its ligands, epidermal growth factor and transforming growth factor alpha, as well as several tumor suppressor genes such as p53 and retinoblastoma. This study presents novel and interesting findings that are consistent with the current models of aromatase influence and the complex interactions of biochemical pathways leading to mammary tumorigenesis.

Reproductive tissue renin gene expression in preeclampsia

OBJECTIVE

Using an analogy with renin gene overexpression, low-renin hypertension animal models, we wished to test the hypothesis that renin gene expression is increased in decidua basalis in human gestation with preeclampsia.

METHODS

Human placentas were obtained immediately after delivery from 11 control (C) and 11 preeclamptics (PE). Tissue samples were microdissected and renin gene expression in decidua basalis (DB), chorionic villi (CV), and decidua vera (DV) was measured using dot-blot hybridization.

RESULTS

Overall renin gene expression is highest in decidua basalis (mean +/- SEM, 2.66 +/- 0.69 densitometry area units) compared to chorionic villi (mean +/- SEM, 1.85 +/- 0.5) or compared to decidua vera (mean +/- SEM, 1.63 +/- 0.9) (both t-tests p = 0.001 two-tailed and analysis of variance p = 0.0001). Renin gene expression in DB and in CV was similar in both preeclamptic and normal pregnancies (DB mean +/- SEM C 2.79 +/- 0.96 versus PE 2.54 +/- 1.04, and CV mean +/- SEM C 2.11 +/- 0.91 versus PE, 1.59 +/- 0. 44). Renin gene expression in DV was approximately threefold higher in tissues from preeclamptics compared to control (mean +/- SEM PE 2. 44 +/- 1.76 versus C 0.82 +/- 0.42). Using the median value of 0.5 units for DV as cutoff, the preeclamptics displayed higher renin gene expression (chi square p = 0.033, two tailed).

CONCLUSION

Our data suggest that renin gene expression is increased in preeclampsia in decidua vera. This may explain previously reported increased renin secretion in uterine circulation in preeclampsia.

Tissue-specific synthesis and oxidative metabolism of estrogens

Estrogen exposure represents the major known risk factor for development of breast cancer in women and is implicated in the development of prostate cancer in men. Human breast tissue has been shown to be a site of oxidative metabolism of estrogen due to the presence of specific cytochrome P450 enzymes. The oxidative metabolism of 17beta-estradiol (E2) to E2-3,4-quinone metabolites by an E2-4-hydroxylase in breast tissue provides a rational hypothesis to explain the mammary carcinogenic effects of estrogen in women because this metabolite is directly genotoxic and can undergo redox cycling to form genotoxic reactive oxygen species. In this chapter, evidence in support of this hypothesis and of the role of P4501B1 as the 4-hydroxylase expressed in human breast tissue is reviewed. However, the plausibility of this hypothesis has been questioned on the grounds that insufficient E2 is present in breast tissue to be converted to biologically significant amounts of metabolite. This critique is based on the assumption that plasma and tissue E2 levels are concordant. However, breast cancer tissue E2 levels are 10-fold to 50-fold higher in postmenopausal women than predicted from plasma levels. Consequently, factors must be present to alter breast tissue E2 levels independently of plasma concentrations. One such factor may be the local production of E2 in breast tissue through the enzyme aromatase, and the evidence supporting the expression of aromatase in breast tissue is also reviewed in this chapter. If correct, mutations or environmental factors enhancing aromatase activity might result in high tissue concentrations of E2 that would likely be sufficient to serve as substrates for CYP1B1, given its high affinity for E2. This concept, if verified experimentally, would provide plausibility to the hypothesis that sufficient E2 may be present in tissue for formation of catechol metabolites that are estrogenic and which, upon further oxidative metabolism, form genotoxic species at levels that may contribute to estrogen carcinogenesis.

Overexpression of aromatase leads to development of testicular leydig cell tumors : an in vivo model for hormone-mediated TesticularCancer

Despite recent advances in diagnosis and treatment of testicular cancer, its causes remain unknown. The most common conditions known to be associated with testicular cancer are cryptorchidism, infertility, and overexposure to pesticides or radiation. Recent studies also indicate hormones may play a crucial role in testicular tumorigenesis. Our studies show that about half of the male transgenic mice overexpressing aromatase in testis were infertile and/or had larger than normal testicles. Gross pathology and histological analysis showed the mice to have Leydig cell tumors, unilaterally or bilaterally. Serum estradiol levels for transgenic mice were at least twice as high as those for nontransgenic mice. Expression of aromatase and estrogen receptor were also very high in testicular tissue of transgenic mice compared to nontransgenic mice. Consistent with increased estrogenic activity in the testicular tissue, we also saw an increase in the levels of genes involved in cell cycle that are regulated by the estrogen. To obtain a better understanding of the biological significance of testicular tumorigenesis, a reliable animal model is necessary to clarify the mechanisms and correlations associated with human cancers. Here we describe such a model, which shows that overexpression of aromatase results in increased estrogen production and a changed hormone milieu, leading to the induction of testicular cancer (Leydig cell tumors). This predictable and useful model is a potential tool for the study of testicular tumorigenesis, hormonal carcinogenesis, synergistic action of other carcinogens on hormone-induced tumors, and tumor dependency on endocrine factors.

Aromatase overexpression and breast hyperplasia, an in vivo model--continued overexpression of aromatase is sufficient to maintain hyperplasia without circulating estrogens, and aromatase inhibitors abrogate these preneoplastic changes in mammary glands

To test directly the role of breast-tissue estrogen in initiation of breast cancer, we have developed the aromatase-transgenic mouse model and demonstrated for the first time that increased mammary estrogens resulting from the overexpression of aromatase in mammary glands lead to the induction of various preneoplastic and neoplastic changes that are similar to early breast cancer. Continued overexpression of aromatase that leads to increased breast-tissue estrogen contributes to a number of epigenetic changes in mammary tissue such as alteration in the regulation of genes involved in apoptosis, activation of genes involved in cell cycle and cell proliferation, and activation of a number of growth factors. Our current studies show aromatase overexpression is sufficient to induce and maintain early preneoplastic and neoplastic changes in female mice without circulating ovarian estrogen. Preneoplastic and neoplastic changes induced in mammary glands as a result of aromatase overexpression can be completely abrogated with the administration of the aromatase inhibitor, letrozole. Consistent with complete reduction in hyperplasia, we have also seen downregulation of estrogen receptor and a decrease in cell proliferation markers, suggesting aromatase-induced hyperplasia can be treated with aromatase inhibitors. Our studies demonstrate that aromatase overexpression alone, without circulating estrogen, is responsible for the induction of breast hyperplasia and these changes can be abrogated using aromatase inhibitors.

Serum levels of macrophage colony-stimulating factor-1 in cervical human papillomavirus infection and intraepithelial neoplasia

OBJECTIVE

Our goal was determine the correlation between serum colony stimulating factor-1 levels, cervical human papillomavirus infection, and dysplasia.

STUDY DESIGN

Serum samples were obtained from control subjects from the United States and from a group of Panamanian women. Members of the latter group fell into 3 categories: those who serve as Panamanian control subjects and who test negative for human papillomavirus (n = 10); those who are high risk by history and test positive for human papillomavirus types 16/18 and 30s (n = 10); and those with the same high-risk history with biopsy-proven cervical intraepithelial neoplasia (n = 8). Serum colony-stimulating factor-1 levels were determined using enzyme-linked immunosorbent assay. Data were analyzed with the Student-Newman-Keuls and t tests.

RESULTS

Mean serum colony-stimulating factor-1 levels of patients with a positive test result for human papillomavirus (1166 +/- 949 pg/mL) and cervical intraepithelial neoplasia (1295 +/- 314 pg/mL) were higher than those of control subjects from the United States (584 +/- 237 pg/mL) and those of Panamanian control subjects (520 +/- 229 pg/mL). Statistical analysis revealed the concentration of colony-stimulating factor in patients with positive test results for human papillomavirus or cervical intraepithelial neoplasia were significantly higher than in control groups. In addition, combining patients with human papillomavirus with those who have cervical intraepithelial neoplasia results in a group that has significantly higher colony-stimulating factor levels compared with control subjects.

CONCLUSIONS

Both high-grade cervical dysplasia and high-risk human papillomavirus infection are associated with higher mean serum colony-stimulating factor levels, suggesting a possible role for colony-stimulating factor-1 in cervical neoplasia. Further studies are needed to understand the mechanism of colony- stimulating factor activation in human papillomavirus infection. This may assist in designing therapeutic approaches for the management of this disease.

Overexpression of macrophage colony-stimulating factor (CSF-1) and its receptor, c-fms, in normal ovarian granulosa cells leads to cell proliferation and tumorigenesis

OBJECTIVE

To investigate the interdependent role of macrophage colony-stimulating factor (CSF-1) and its receptor (c-fms) on their induction and their role in granulosa cell tumorigenesis.

METHODS

Normal ovarian granulosa cells were used to develop stable transfectants that overexpress CSF-1 or CSF-1/c-fms. CSF-1 was expressed under the control of tissue/cell specific alpha-inhibin promoter, and c-fms was expressed constitutively using a viral promoter. Stable transfectants were used to examine the effect of overexpression of these molecules on the proliferation, induction of autocrine loop, and tumorigenesis.

RESULTS

Expression vectors were developed for CSF-1 and its receptor, c-fms, and used to generate stable transfects overexpressing these genes in granulosa cells. Data show that overexpression of CSF-1 leads to the induction of its receptor. Stable transfectants that overexpress CSF-1 show about a 2.5-fold increase in cell proliferation compared with normal granulosa cells, and these cells are also converted to anchorage-independent and tumorigenic phenotype. Using an antisense RNA approach, we also demonstrated that the increased cell proliferation is CSF-1 specific. Concomitant overexpression of CSF-1 and c-fms further results in increased cell proliferation (sixfold), rapid anchorage-independent growth, and aggressive tumor formation.

CONCLUSION

CSF-1 is capable of inducing its own receptor, and, similarly, the CSF-1 receptor, c-fms, can also induce its growth factor ligand. These studies also demonstrate the interdependent role of these genes in transformation of normal ovarian granulosa cells to a tumorigenic phenotype and suggest the possibility of a similar role for these genes in progression of ovarian cancer.

Opium alkaloid noscapine is an antitumor agent that arrests metaphase and induces apoptosis in dividing cells

An alkaloid from opium, noscapine, is used as an antitussive drug and has low toxicity in humans and mice. We show that noscapine binds stoichiometrically to tubulin, alters its conformation, affects microtubule assembly, and arrests mammalian cells in mitosis. Furthermore, noscapine causes apoptosis in many cell types and has potent antitumor activity against solid murine lymphoid tumors (even when the drug was administered orally) and against human breast and bladder tumors implanted in nude mice. Because noscapine is water-soluble and absorbed after oral administration, its chemotherapeutic potential in human cancer merits thorough evaluation.

Role of MMTV integration locus cellular genes in breast cancer

Mouse mammary tumorigenesis as a result of mouse mammary tumor virus (MMTV) integrations has helped to identify a wide variety of interesting genes that play a role in mammary development and tumorigenesis. Several such genes int1/wnt1, wnt3, wnt 10B, int2/fgf3, fgf4, int3/notch and int6 have been shown to be genetically altered in naturally formed mammary tumors as a consequence of MMTV integration. Some of these genes have been well characterised and examined in in vivo breast cancer transgenic models for their potential for tumorigenesis. Overexpression of one or more of these genes have resulted in a striking proliferation of mammary gland epithelium of both female and male transgenic mice. Our own studies have demonstrated overexpression of int5/aromatase in mammary glands of virgin and postlactational females leads to the induction of various preneoplastic and neoplastic changes that are similar to early breast cancer, that may, in turn, increase the risks for developing breast cancer. Therefore, further understanding of these genes should provide new insights to their involvement and mechanism of action in breast cancer.

A novel in vitro and in vivo breast cancer model for testing inhibitors of estrogen biosynthesis and its action using mammary tumor cells with an activated int-5/aromatase gene

We recently showed that the cellular gene int-5/aromatase in BALB/c mammary alveolar hyperplastic nodule (D2 HAN/D2 tumor cells) is activated as a result of mouse mammary tumor virus integration within the 3' untranslated region of the aromatase gene. In the present study, we evaluated the effect of various aromatase inhibitors on androstenedione-mediated tumor cell growth. Also, we compared the effect of the non-steroidal aromatase inhibitor (CGS 16949A) on the inhibition of tumor growth. Our results show that D2 tumor cells respond well to various aromatase inhibitors and antiestrogens. We examined the usefulness of this model by using D2 tumor cells to simulate postmenopausal breast cancer employing both in vitro cell culture and in vivo ovariectomized (OVX) nude mouse. Unlike DMBA-induced tumors or other models, D2 tumor cells form very rapid tumors within a few days in intact mice or OVX nude mice with androstenedione supplementation and respond well to an aromatase inhibitor. This model with its known mechanism of aromatase activation should be useful for studying the role of intra-tumoral estrogen in mammary cancer, for evaluating the effects of aromatase inhibitors and antiestrogens, and for comparing breast cancer treatments.

Regulation of rat granulosa cell alpha-inhibin expression by luteinizing hormone, estradiol, and progesterone

OBJECTIVE

Our purpose was to assess the effects of follicle-stimulating hormone, luteinizing hormone, forskolin (an adenylyl cyclase activator), estradiol, and progesterone on alpha-inhibin promoter activity in an in vitro fusion gene-transfection system.

STUDY DESIGN

A fusion gene consisting of the alpha-inhibin 5' flanking and promoter regions linked to the chloramphenicol acetyl transferase reporter gene was constructed. A granulosa cell line originally derived from an inbred strain of Berlin Duckrey rats was transiently transfected with the fusion gene. Fusion gene activity was determined by measuring chloramphenicol acetyl transferase activity in transfected cells.

RESULTS

Both follicle-stimulating hormone and luteinizing hormone activated the alpha-inhibin promoter. Activity in response to combined luteinizing hormone-forskolin treatment was greater than the summation of the activities of the two treatments individually, suggesting that the effects of luteinizing hormone might be partially mediated by second messengers other than cyclic adenosine monophosphate. Gonadotropin-stimulated activity was diminished by estradiol and combined estradiol-progesterone treatments.

CONCLUSIONS

The stimulatory effects of follicle-stimulating hormone and luteinizing hormone on alpha-inhibin production are mediated at least in part by stimulation of the alpha-inhibin promoter. The stimulatory effects are blunted by estradiol-progesterone. These observations may partially explain how alpha-inhibin is down-regulated in vivo in response to the preovulatory luteinizing hormone surge.