Abstract P4-01-07: A comprehensive liquid biopsy in patients undergoing neoadjuvant therapy

Background: Precision medicine is revolutionizing breast cancer (BC) care. Comprehensive liquid biopsies are a tool for personalized care in patients with locally advanced breast cancer (LABC). Identifying robust biomarkers as part of a comprehensive liquid biopsy to predict response to treatment is of immense clinical interest.

Methods: After obtaining IRB approval, serial blood samples were collected from patients with LABC undergoing neoadjuvant therapy. Paired biopsies were collected prior to treatment and were sent to Foundation Medicine for next-generation sequencing (NGS). We used a sized-base microfilter technology to capture circulating tumor cells (CTCs) and circulating cancer associated fibroblasts (cCAFs). Patients with one or more CTCs or cCAFs were deemed positive for these tests. Additionally, in collaboration with Foundation Medicine, we extracted circulating tumor DNA (ctDNA) and we analyzed it using the FoundationACT platform. Patients with a detectable genomic alteration in their plasma were considered as having a positive ctDNA test. Our primary objective is to determine if a comprehensive liquid biopsy can serve as a prognostic marker of pathologic complete response (pCR).

Results: For this analysis we describe our findings in the initial blood draw of the first 18 patients enrolled. The mean age is 54 years (38-70). All patients who had their tumors sequenced had a detectable mutation. Consistent with the findings of others, we found TP53 mutations to be the most prevalent at 83.3%. We found that 44% of patients had ctDNA, 68.4% had cCAFs and 78.9% had CTCs. Many patients also had clusters of cells, consisting of one cell type, or co-clusters, consisting of both. 38.9% had CTC clusters, 16.7% had cCAF clusters and 16.7% had co-clusters (CTCs and cCAFs together). Some patients with CTCs did not have cCAFs and vice versa. The number of CTCs and cCAFS did not correlate with stage of disease or receptor status.

Conclusions: We describe a comprehensive liquid biopsy combining a sized-based microfilter technology for CTC and cCAFs identification and the FoundationACT platform for ctDNA analysis is feasible and these biomarkers can be detected in patients with LABC prior to the initiation of neoadjuvant therapy. Our study is accruing rapidly, and we will update our results with the longitudinal collection and the prognostic value of a comprehensive liquid biopsy at the time of the meeting.

Citation Format: Sandoval Leon AC, Medina Saenz K, Miller P, Benson A, Calfa C, Mahtani R, Slingerland J, Perez A, Vogel C, Valdes-Albini F, El-Ashry D, Lippman M. A comprehensive liquid biopsy in patients undergoing neoadjuvant therapy [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 P4-01-07.

Abstract P4-15-06: Results of a randomized double blind trial of neoadjuvant anastrozole plus placebo vs anastrozole plus saracatinib for ER+ postmenopausal breast cancer

Antiestrogen mediated cell cycle arrest requires the CDK inhibitor, p27. Src kinase mediates p27 loss and antiestrogen resistance in ER+ breast cancer lines in vitro. In ER+ xenografts, the Src inhibitor, saracatinib, restored antiestrogen responses in resistant tumors. This led to a Phase I/randomized double-blind Phase II trial to test effects of saracatinib with anastrozole for ER+ and/or PR+ postmenopausal breast cancer.

Phase I accrued 12 subjects and showed 175 mg po saracatinib is safely given with 1 mg po daily anastrozole with good PK . In Phase II, postmenopausal women with new ER+ and/or PR+, HER2- breast cancers ≥ 2 cm were randomized 2:1 to either neoadjuvant anastrozole with saracatinib or anastrozole/placebo over 6 months. Response was assayed by clinical 2D measurements each cycle and by MRI pre-study, at 10 weeks and prior to surgery. The Phase II primary endpoint was to test if tumor volume decrease (from 2D clinical measures) with dual therapy (dual) exceeded that of monotherapy (mono) by >20%. Secondary endpoints included tumor response by 3D MRI measures and by RECIST, PK and toxicity, and molecular predictors of drug efficacy in pre-/ post-therapy tumors. Of 58 subjects, 15% were Black, 5% Asian and 79% White. 61% were Hispanic. Dual therapy was well tolerated, with the following grade 1 toxicities: flu-like syndrome 20%, non-pruritic rash 48% (17% for mono), self-limited diarrhea in 55% (33% mono). Transaminasemia with dual therapy was 52.5% and 17% with mono. 6/59 stopped dual due to drug related AEs: 2 had gr 3 hepatitis, one gr 3 anemia, 3 had grade 3 urticarial rash. Dual Rx increased mean anastrozole levels to 50 ng/ml vs 38 ng/ml for mono (T test p= 5.45201 E-05). Mean saracatinib level, 269 ng/ml, was similar to prior studies. All of 50 evaluable subjects showed clinical and MRI tumor responses. 17% in both groups progressed, usually after 16 weeks. Mean tumor vol (calculated from 2D clinic measures) declined more rapidly (by 63% in dual vs 55% in mono at 8 weeks), but both groups showed an 89% mean tumor volume decrease by 20 weeks. Clinical RECIST showed size reductions of 61% in dual and 62% after monotherapy. Tumor volumes based on 3D MRI show a non-significant trend to greater response to dual therapy, with mean volume decreased by 64% vs 45% at the end of dual vs monotherapy. RECIST response by MRI also showed a trend to greater % decrease tumor size post treatment by 34% vs 25% in dual vs mono. Thus, clinical volumetric assessment of response to this neoadjuvant endocrine therapy may overestimate response compared to volumes calculated by MRI, while RECIST may underestimate it. Pathologic responses based on initial and residual tumor burden calculated from initial and final tumor volumes and % cellularity in biopsy and surgical specimens will be presented.

Citation Format: Slingerland JM, Mark P, Hurley J, Net J, Collado-Mesa F, Lippman M, Avisar E, Yepes M, Jorda M, Gomez C. Results of a randomized double blind trial of neoadjuvant anastrozole plus placebo vs anastrozole plus saracatinib for ER+ postmenopausal 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 P4-15-06.

Abstract PD9-10: Circulating CAF/cancer stem cell co-clusters bolster breast cancer metastasis

Background: Metastatic disease is the primary cause of breast cancer (BC) mortality. Cancer associated fibroblasts (CAFs) are the majority of stroma in BC and critical players in BC malignancy. For example, CAFs are the main source of SDF-1, a prominent chemokine in the tumor microenvironment (TME) that also imparts stem cell-like characteristics to BC cells. Metastasis occurs due to the transport of circulating tumor cells (CTC) and clusters of CTCs through the vasculature. Stem-like CTCs and clusters have a greater propensity to establish metastasis. We recently identified circulating CAFs (cCAFs) in blood from patients with BC and in spontaneous, syngeneic, and xenograft mouse models of BC. cCAFs not only circulate individually, but are also found in clusters with CTCs. In this study, we examine the role of CAFs in promoting egress of stem-like CTCs (cCSCs), determine the capacity of stem-like CTCs to cluster with CAFs, and evaluate the involvement of CTC/cCAF clustering in augmenting BC metastasis.

Methods: Our model employs NSG mice with orthotopic xenograft implantation of BC cells, primary CAF cell lines, or co-implantation of BC and CAF cell lines. We used two different BC cell lines: the non-metastatic BC cell line, MCF-7, and the highly metastatic primary BC cell line, DT28. We also employed the MMTV-PyMT spontaneous model of BC metastasis, and we used BALB/c mice injected with syngeneic 4T1 or 67nR cells to evaluate cCAFs, CTCs, and cluster egress in preclinical models. Mice were sacrificed at specific time points, and cardiac blood was collected. Blood was filtered using the faCTChecker microfluidic filtration instrument (Circulogix). Filters were stained for IF and cCAFs, CTCs, cCSCs, and clusters were enumerated. Tumors from CAF co-injected mice were evaluated for their stem cell-like phenotype and re-implanted in mice to evaluate tumorigenicity and metastasis.

Results: In spontaneous, syngeneic, and orthotopic xenograft models of BC, cCAFs, CTCs, and cCAF/CTCs co-clusters appear early in tumor development. cCAF/CTC clusters increase in correlation with tumor burden and metastasis. Co-inoculation of CAFs with BC cells resulted in a significant increase in tumor progression, metastasis, and in a substantially higher number of both individual cells and clusters in circulation. Dissociated tumor cells from CAF co-injected tumors had a higher proportion of CD44+stem cell-like cells (CSCs), enhanced ALDH-1 expression, and enhanced mammosphere formation. CD44+ CSCs, individually and in clusters, are found early on in the circulation of mice injected with dissociated tumor cells from CAF co-injected tumors. Upon re-implantation of CAF co-injected dissociated tumor cells without CAFs, dissociated tumor cells showed enhanced tumorigenicity and malignancy.

Conclusion: CAFs are highly motile and cCAFs precede CTCs into circulation and can do so independently of tumor cells. CAFs sustain egress of tumor cells by augmenting malignancy and stemness of BC cells. cCAF clusters with the highly metastatic stem cell-like subset of CTCs bolster metastatic colonization. Targeting primary CAF function and/or cCAF/cCSC co-clusters may provide novel avenues to abrogate BC metastasis.

Citation Format: Sharma U, Miller P, Medina Saenz K, Picon-Ruiz M, Morata-Tarifa C, Spartz A, Troness B, Park DN, Seagroves TN, Slingerland JM, Lippman ME, El-Ashry D. Circulating CAF/cancer stem cell co-clusters bolster breast cancer metastasis [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 PD9-10.

Abstract P6-05-01: Interactions between adipocytes and breast cancer cells stimulate cytokine production and drive Src/SOX2/miR-302b mediated malignant progression

Consequences of the obesity epidemic on cancer morbidity and mortality are not fully appreciated. Obesity is a risk factor for many cancers, but the mechanisms by which it contributes to cancer development and patient outcome have yet to be fully elucidated. Here, we examined the effects of coculturing human-derived adipocytes with established and primary breast cancer cells on tumorigenic potential. We found that the interaction between adipocytes and cancer cells increased the secretion of proinflammatory cytokines. Prolonged culture of cancer cells with adipocytes or cytokines increased the proportion of mammosphere-forming cells and of cells expressing stem-like markers in vitro. Furthermore, contact with immature adipocytes increased the abundance of cancer cells with tumor-forming and metastatic potential in vivo. Mechanistic investigations demonstrated that cancer cells cultured with immature adipocytes or cytokines activated Src, thus promoting Sox2, c-Myc, and Nanog upregulation. Moreover, Sox2-dependent induction of miR-302b further stimulated cMYC and SOX2 expression and potentiated the cytokine-induced cancer stem cell-like properties. Finally, we found that Src inhibitors decreased cytokine production after coculture, indicating that Src is not only activated by adipocyte or cytokine exposures, but is also required to sustain cytokine induction. These data support a model in which cancer cell invasion into local fat would establish feed-forward loops to activate Src, maintain proinflammatory cytokine production, and increase tumor-initiating cell abundance and metastatic progression. Collectively, our findings reveal new insights underlying increased breast cancer mortality in obese individuals and provide a novel preclinical rationale to test the efficacy of Src inhibitors for breast cancer treatment.

Citation Format: Picon-Ruiz M, Pan C, Drewes-Elger K, Jang K, Besser A, Zaho D, Morata-Tarifa C, Kim M, Ince TA, Azzam D, Wander S, Cote RJ, Guy HA, El-Ashry D, Torne-Poyatos P, Marchal JA, Slingerland JM. Interactions between adipocytes and breast cancer cells stimulate cytokine production and drive Src/SOX2/miR-302b mediated malignant progression [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 P6-05-01.

Abstract P2-01-10: Circulating CAF/CTC complexes and breast cancer metastasis

Background: Metastatic disease in breast cancer (BC) is the leading cause of cancer-related mortality among women worldwide. Synergy between cancer cells and non-cancer cells of the tumor microenvironment (TME) are vital for disease progression. Cancer associated fibroblasts (CAFs) are the major cell type in the stroma of BC and are critical mediators of tumor progression and metastasis. Transport of circulating tumor cells (CTCs) and CTC clusters through the vasculature seeds metastasis and clinical and preclinical studies demonstrate that CTC clusters have a higher metastatic potential than individual CTCs. More recently, circulating cancer stem cells (cCSCs) have been implicated as more metastatic than non-CSC CTCs. In our lab, we have demonstrated that CAFs also circulate (cCAFs). We have observed cCAFs in peripheral blood from breast cancer patients and in murine models of breast cancer. Furthermore, we have observed that cCAFs are present in circulation as both individual cells and as well as in complexes with CTCs. Given the integral role of CAFs in BC metastasis, we hypothesize that cCAFs complex with CTCs/cCSCs to bolster BC metastasis.

Methods: cCAF/CTC clusters were identified and enumerated from peripheral blood of patients with BC, and associations with clinical features and disease outcomes were evaluated. Blood was collected by cardiac puncture from PyMT mice from 4 weeks through to the presence of metastases (10 weeks) and cCAF/CTC clusters enumerated. We co-injected CAFs with MCF-7 cellsl into NSG mice, blood collected by cardiac puncture, and cCAF/CTC clusters were enumerated. At time of final sacrifice, tumors were removed and assessed for presence of CSCs. Using our established model of cCAF/CTC clustering in vitro we interrogated cCAF/CTC complexing with both metastatic and poorly metastatic BC cells.

Results: Circulating cCAFs/CTCs clusters are significantly increased in the blood of patients with advanced stage BC and associate not only with severity of disease but also with poorer clinical outcomes. In the spontaneous PyMT mouse model, the appearance of circulating cCAF/CTC clusters increased significantly as tumors grew but prior to metastasis. We demonstrate that metastatic BC cells form clusters with CAFs in vitro while non-metastatic BC cells do not form complexes with CAFs in vitro. Enriching for stem cells from MCF7 mammospheres, resulted in CAF/CSC clusters in vitro. In mice that were co-injected with non-metastatic MCF7 cells and CAFs from a TNBC/Basal-like BC (CAF23) we observed disease metastasis, an enrichment for cancer stem cell (CSC)-like CTCs, and the presence of circulating cCAF/MCF7-CSC clusters.

Conclusions: Circulating clusters of CTCs and cCAFs are characteristic, and potentially causative, of BC metastasis. Observations of cCAF/CTC clusters from preclinical and clinical samples are corroborated by our determination that the ability of BC cells to form complexes with CAFs in vitro is related to the intrinsic metastatic ability of the breast cancer cells. Both in vitro and in circulation, the BC cells in cCAF/cBC clusters are CSCs, so cCAF/cCSC clusters. Disrupting the formation of cCAF/CTC complexes may be a potential strategy to reduce treat or prevent breast cancer metastasis.

Citation Format: Miller P, Sharma U, Medina-Saenz K, Yeasky T, Picon-Ruiz M, Morata-Tarifa C, Seagroves T, Slingerland J, Lippman M, El-Ashry D. Circulating CAF/CTC complexes and breast cancer metastasis [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 P2-01-10.

Abstract P6-08-08: GATA3 inhibits breast basal-like tumorigenesis

BACKGROUND: Breast cancer can be broadly categorized into two groups depending on the cell type affected. Luminal-type tumors are typically estrogen receptor (ER) positive that are associated with better survival and respond to hormone therapies whereas basal-like tumors are ER negative, more aggressive, and associated with a poor prognosis. GATA3 is a transcription factor well studied for its role as a master regulator of cellular differentiation and stem cell self renewal. Loss of Gata3 in mouse mammary glands blocks luminal cell differentiation and induces growth defects, and low levels of GATA3 are associated with basal-like and metastatic human breast cancers with epithelial-to-mesenchymal transition (EMT). Importantly, luminal cells have been shown to be the origin of some basal-like breast cancers. Due to the proliferation defects caused by GATA3 deficiency, it remains elusive how loss of function of GATA3 contributes to breast cancers development and progression.

METHODS: We previously demonstrated that p18Ink4c (p18), a cell cycle inhibitor, is a downstream target of GATA3 in regulating mammary luminal cell proliferation and loss of p18 leads to luminal type tumorigenesis. To test the role of Gata3 deficiency in tumorigenesis, we generated p18-/-;Gata3+/- mice. Mammary gland development and tumorigenesis were characterized in vivo using a panel of cellular and molecular assays. Results were further confirmed in vitro with well established cell lines.

RESULTS: Loss of p18 rescued mammary growth defects caused by Gata3 heterozygosity. Gata3 heterozygosity impaired luminal, but promoted basal gene expression in mammary epithelial cells. Gata3 heterozygosity in p18 null mice accelerated spontaneous mammary tumorigenesis, reducing the average latency of tumor onset. More importantly, Gata3 heterozygosity transformed the luminal type tumors of p18 null mice into heterogeneous basal-like breast cancers with activated EMT. Conversely, reintroduction of GATA3 inhibited tumor growth and reduced expression of EMT markers in basal-like tumor xenografts. We discovered that expression of GATA3 and Vimentin, an EMT marker, is inversely related in human breast cancers.

CONCLUSION: Our data indicates that GATA3 promotes luminal but suppresses basal cell differentiation in the mammary gland and in tumor development.

Mechanisms underlying the role of GATA3 in suppressing basal-like tumor development are under investigation.BACKGROUND: Breast cancer can be broadly categorized into two groups depending on the cell type affected. Luminal-type tumors are typically estrogen receptor (ER) positive that are associated with better survival and respond to hormone therapies whereas basal-like tumors are ER negative, more aggressive, and associated with a poor prognosis. GATA3 is a transcription factor well studied for its role as a master regulator of cellular differentiation and stem cell self renewal. Loss of Gata3 in mouse mammary glands blocks luminal cell differentiation and induces growth defects, and low levels of GATA3 are associated with basal-like and metastatic human breast cancers with epithelial-to-mesenchymal transition (EMT). Importantly, luminal cells have been shown to be the origin of some basal-like breast cancers. Due to the proliferation defects caused by GATA3 deficiency, it remains elusive how loss of function of GATA3 contributes to breast cancers development and progression.

METHODS: We previously demonstrated that p18Ink4c (p18), a cell cycle inhibitor, is a downstream target of GATA3 in regulating mammary luminal cell proliferation and loss of p18 leads to luminal type tumorigenesis. To test the role of Gata3 deficiency in tumorigenesis, we generated p18-/-;Gata3+/- mice. Mammary gland development and tumorigenesis were characterized in vivo using a panel of cellular and molecular assays. Results were further confirmed in vitro with well established cell lines.

RESULTS: Loss of p18 rescued mammary growth defects caused by Gata3 heterozygosity. Gata3 heterozygosity impaired luminal, but promoted basal gene expression in mammary epithelial cells. Gata3 heterozygosity in p18 null mice accelerated spontaneous mammary tumorigenesis, reducing the average latency of tumor onset. More importantly, Gata3 heterozygosity transformed the luminal type tumors of p18 null mice into heterogeneous basal-like breast cancers with activated EMT. Conversely, reintroduction of GATA3 inhibited tumor growth and reduced expression of EMT markers in basal-like tumor xenografts. We discovered that expression of GATA3 and Vimentin, an EMT marker, is inversely related in human breast cancers.

CONCLUSION: Our data indicates that GATA3 promotes luminal but suppresses basal cell differentiation in the mammary gland and in tumor development.

Mechanisms underlying the role of GATA3 in suppressing basal-like tumor development are under investigation.

Citation Format: Pei X-H, Chan HL, Liu S, Scott A, Pimentel E, Slingerland J, Robbins D, Capobianco A, Bai F. GATA3 inhibits breast basal-like tumorigenesis [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 P6-08-08.

Abstract P6-03-02: Chronic CXCL12 exposure induces a metastatic phenotype in ER-positive breast cancer cells through transcriptional reprogramming

The chemokine CXCL12 is transcriptionally activated by estrogen in estrogen receptor (ER)-positive breast cancer cells. We have found that CXCL12 signaling is essential to maintain the long-term growth of ER-positive breast cancer cells and promotes cancer cell growth in the absence of estrogen. Chronic blockade of CXCL12 signaling with AMD3100, an inhibitor of CXCL12 receptor CXCR4, causes cell death in these cells. Chronic exposure to CXCL12 reprograms ER-positive breast cancer cells through genome-wide transcriptional changes and activates numerous signaling pathways including EMT and the inflammatory response. Many ER target genes are activated in CXCL12-reprogrammed cells even in the absence of estrogen which leads to the diminished estrogen modulated transcription in these cells. These cells also show enhanced signaling via TGFb, EGFR and Rac1 pathways, rendering these cells more sensitive to the CDK7 inhibitor, THZ1, and to drug combinations of THZ1 with the EGFR inhibitor Gefitinib or the RAC1 inhibitor EHT 1864. Furthermore, CXCL12-reprogrammed ER-positive breast cancer cells become more motile in vitro and display a metastatic phenotype in a mouse model. The lung-tropic phenotype of CXCL12-reprogramed MCF-7 cells could be explained by increased expression of integrins and pro-inflammatory signaling molecules. Our novel finding of chronic CXCL12 action on ER-positive breast cancer cells suggests a mechanism by which the interaction between stromal and tumor cells leads to increased breast tumor metastatic potential.

Citation Format: Sun J, Slingerland JM, Lippman ME. Chronic CXCL12 exposure induces a metastatic phenotype in ER-positive breast cancer cells through transcriptional reprogramming [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 P6-03-02.

Abstract P3-06-01: Therapeutic targeting of RAGE in the tumor and tumor microenvironment inhibits breast progression and metastasis

Background: The Receptor for Advanced-Glycation End-products (RAGE) is highly expressed in various cancers and its expression is correlated with poorer outcomes in breast cancer. We have previously implicated RAGE in breast cancer, but whether RAGE drives breast cancer progression and metastasis either through tumor cell intrinsic effects, non-tumor cells of the tumor microenvironment, or both, is not fully understood. More importantly, studies are lacking that target RAGE therapeutically in cancer, and may therefore represent a novel treatment for breast cancer metastasis.

Methods: Using multiple human and murine breast cancer models we dissected the tumor intrinsic versus tumor microenvironment role of RAGE in metastasis. RAGE was targeted in tumor cells using multiple shRNAs, in non-tumor cells by global gene knockout in mice, and both by therapeutically targeting with the novel RAGE inhibitor FPS-ZM1. In vivo orthotopic models included the NSG (NOD-SCID-gamma) xenograft mouse model (with MDA-MB-231 cells; herein 231), BALBc (4T-1 and 67NR), and C57BL6 wild-type and RAGE knockout (RAGE -/-) mice (with MMTV-PyMT spontaneous breast cancer derived AT-3 cells).

Results: We first tested how RAGE impacts tumor cell intrinsic mechanisms using either RAGE shRNAs or FPS-ZM1 in 231, 4175 (231 isogenic highly metastatic cells) and 4T-1 cells. RAGE shRNA and FPS-ZM1 both decreased RAGE MAP-kinase signaling, transwell invasion and soft agar colony formation, without affecting proliferation. In vivo, RAGE shRNA knockdown in 231 cells did not affect tumor growth, but inhibited metastasis to lung and liver. RAGE shRNA knockdown in 4175 cells, decreased orthotopic tumor growth, and reduced tumor angiogenesis and tumor recruitment of leukocyte / macrophages. Furthermore, RAGE shRNA knockdown dramatically decreased metastasis of 4175 cells to lung and liver in a time and sized matched manner compared to shRNA controls. Similarly, RAGE knockdown in 4T-1 cells reduced cell invasion and colony formation, and inhibited lung metastasis from the orthotopic site in BALBc immunocompetent mice.

To test the non-tumor cell microenvironment role of RAGE, we performed syngeneic studies with orthotopically injected AT-3 cells in RAGE +/+ and RAGE -/- C57BL6 mice. RAGE -/- mice displayed striking impairment of tumor cell growth compared to RAGE +/+ mice, along with decreased MAP-kinase signaling, tumor angiogenesis and inflammatory cell recruitment.

Finally, to test the combined inhibition of RAGE in both tumor cell intrinsic and non-tumor cells of the microenvironment, we performed in vivo treatment of 4175 tumors with FPS-ZM1 (1mg/kg, twice per week). Compared to vehicle, FPS-ZM1 inhibited primary tumor growth, inhibited tumor angiogenesis and inflammatory cell recruitment, and most importantly prevented metastasis to lung and liver.

Conclusion: These data clearly demonstrate a role for RAGE in breast cancer progression and metastasis through distinct effects in the tumor cell and non-tumor cells of the tumor microenvironment. Furthermore, our data from drug inhibitor studies highlight the combined targeting of RAGE in the tumor and tumor microenvironment, and as a viable therapeutic means for breast and other metastatic cancers.

Citation Format: Kwak T, Drews-Elger K, Ergonul A, Braley A, Hwang GH, El-Ashry D, Slingerland JM, Lippman ME, Hudson BI. Therapeutic targeting of RAGE in the tumor and tumor microenvironment inhibits breast progression and metastasis [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 P3-06-01.

Abstract P2-05-07: RAGE-ligand signaling drives breast cancer metastasis through affecting cells of the tumor and microenvironment

Breast cancer is most common malignant state in women, with 20% of these patients developing metastasis during the course of their disease. Further understanding is needed of the process and mechanisms of metastasis. Our lab and others have been shown that Receptor of Advanced-Glycation End-products (RAGE) plays a role in tumorigenesis and metastasis. RAGE is highly expressed in various cancers including breast cancer and its protein levels correlate with poor patient outcome in breast cancer and other cancers. Activation of RAGE results in increased proliferation, migration and invasion of cancer cells. Further studies in mice have shown it may be a therapeutic target to reduce tumor growth and the resulting metastasis. Further understanding is needed of the role of RAGE in driving metastasis through affecting cells of both the tumor and tumor stroma to design novel therapeutics. Using the breast cancer cell model (MDA-MB-231) and its organotropic sister cells lines selected in vivo for increased metastasis to lung (4175) and bone (1833), we tested the role of RAGE in driving tumor metastasis in vitro and in vivo with xenograft mouse models. To test the role of RAGE in the tumor microenvironment we used the AT-3 syngeneic breast cancer cell model in C57BL6 wild-type and RAGE knockout mice. We demonstrated that the highly metastatic variant of 231 cells (4175 and 1833) have increased expression level of RAGE compared to MDA-MB-231 parental cells. Ectopic over-expression of RAGE in parental 231 cells led to increased migratory and invasive properties compared to vector control cells, without affecting cell proliferation or viability. RAGE knockdown by shRNA in 4175 and 231 parental cells showed decreased cell invasion in transwell assays compared to control scramble shRNA. To validate our data in vivo, we performed mammary fat pad injection of 4175 cells (RAGE and scr shRNA) in NOD SCID gamma mice. Tumor growth and weight was impaired in RAGE gene knockdown 4175 cells compared to scramble (scr) controls. Analysis of lung and liver tissue retrieved from mice revealed RAGE knockdown in 4175 cells prevented metastasis compared to 4175 scr control cells. To test the role of RAGE on non-tumor cells of the breast stroma we next performed syngeneic studies with AT-3 cells (MMTV-PyMT spontaneous BC cell model), by injection into the mammary fat pad of wild-type and RAGE knockout C57BL6 immunocompetent mice. RAGE knockout mice (RAGE -/-) displayed striking impairment of tumor cell growth compared to wild-type (RAGE +/+) mice. We are currently testing whether novel RAGE inhibitors impact breast cancer progression and metastasis.

These data highlight RAGE drives breast cancer progression and metastasis through affecting both tumor cell intrinsic and non-tumor cell microenvironment effects. Future studies will demonstrate the potential of RAGE inhibition as a novel therapeutic approach for preventing and treating metastatic disease in breast and other cancers.

Citation Format: Kwak T, Drews-Elger K, Ergonul A, Zhao D, Besser A, Slingerland JM, Lippman ME, Hudson BI. RAGE-ligand signaling drives breast cancer metastasis through affecting cells of the tumor and microenvironment. [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 P2-05-07.

Abstract P1-03-02: Estrogens contribute to cytokine upregulation and cancer stem cell recruitment upon breast cancer contact with mature human mammary adipocytes: Effects of estrogen type and adipocyte donor weight

Consequences of the obesity epidemic on cancer morbidity and mortality are not fully appreciated. While obesity confers increased cancer risk and worse outcome, mechanisms thereof are not fully known. We show prolonged co-culture of fat cells (human adipocyte stem cells, differentiated adipocytes or mature adipocytes) from breast tissue together with breast cancer lines or cultured primary dissociated human breast tumor cells increases secretion of six different pro-inflammatory cytokines, each of which contributes to tumor progression through cancer stem cell recruitment. Prolonged exposure to fat cells or to each cytokine increases the proportion of cells that form mammosphere and express ALDH1 activity in vitro and that can initiate primary orthotopic tumors and metastasis in vivo. Adipocyte and cytokine exposures activate Src, and Src family kinase activity leads to induction of embryonic transcription factors that upregulate miR302b. miR302b induction is Sox2-dependent, promotes cytokine-driven sphere formation, and in turn, stimulates cMYC and SOX2 expression. Src is not only activated by adipocyte or cytokine exposures, it is also required to sustain cytokine induction, since Src inhibitors decrease cytokine production after co-culture. Cytokine upregulation was much greater after co-culture of ER+ breast cancer cells with mature, aromatase positive, adipocytes than with adipocyte stem cells. Cytokine induction was estrogen regulated. The mechanisms of cytokine induction, ER-coactivation and effects of different estrogenic ligands will be presented.

Present data illuminate the increased risk of breast cancer after menopause, particularly in obese women and the increased breast cancer mortality with obesity: cancer cell invasion into local fat, in the presence of high local aromatase and intracellular estrogen would establish feed-forward loops to activate Src, maintain pro-inflammatory cytokine production and increase tumor initiating cell abundance, tumor growth and metastasis. These data link obesity related pro-inflammatory cytokines to Src activation and cancer initiating cell abundance, and provide a novel rationale for Src inhibitors together with endocrine therapy for breast cancer.

Citation Format: Slingerland J, Picon-Ruiz M, Jang K, Morata-Tarifa C, Pan C, Besser A, Kim M, Ince TA, Howard GA, El-Ashry D. Estrogens contribute to cytokine upregulation and cancer stem cell recruitment upon breast cancer contact with mature human mammary adipocytes: Effects of estrogen type and adipocyte donor weight. [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 P1-03-02.

Abstract AS31: MEK inhibition reverses antiestrogen resistance in ovarian cancer (OVCA) via alteration of cell cycle pathways and MAPK/estrogen regulated gene expression

BACKGROUND: It is estimated that 67% of epithelial OVCAs are estrogen receptor (ER) positive. However, the response to anti-estrogen therapy in OVCA remains marginal. The Ras/Raf/MEK/MAPK pathway is hyperactivated in 40% of OVCAs. We have previously shown that estrogens further activate kinases such as Src, ER and Src kinase binding in the cytoplasm suggesting a non-genomic role or ER in OVCA. We postulated that estrogens further activate MAPK signaling and combination ER blockade with MEK inhibition would block cross-talk and increase the efficacy of ER blockade.

METHODS: The effects of treatment with MEK inhibitor (AZD6244) and anti-estrogen (Fulvestrant), each alone or together, on cell cycle and cell survival were evaluated in ER+ OVCA lines in vitro. Drug effects on xenograft tumor growth were assayed in vivo in NOD/SCIDs. Reverse phase protein lysate array (RPPA) analysis and gene expression analysis (GEA) were performed to evaluate biomarkers of drug response. Finally, a previously reported MAPK gene signature identified in breast cancer was analyzed in the OVCA lines treated with AZD6244 and combination treatment. And using alteration of gene expression upon MEKi treatment as suggestive of MAPK regulation, we define a MAPK gene signature originating from ovarian cancer cells.

RESULTS: RPPA analysis of high grade serous tumors from the TCGA (n=408) demonstrates that over 70% of tumors have phosphorylated MEK and MAPK, and patients with ER+ cancers and high pMAPK or pMEK (top50%), have a worse overall survival than those with low pMAPK or pMEK. Estrogen (E2) increases phosphorylation of MEK in ER+ OVCA cells. Fulvestrant caused minimal growth arrest after treatment demonstrating intrinsic resistance. AZD6244 caused loss of pMAPK, partial G1 cell cycle arrest and a modest increase in p27 levels in a dose dependent manner after treatment. However, responsiveness of OVCA cells to fulvestrant increased by addition of AZD6244 in vitro, with synergistic cell cycle arrest mediated by p27 binding to Cyclin E/cdk2 and much greater inhibition of MAPK activity. Gene enrichment analysis showed an increase in the ERB4/MAPK gene set with Fulv alone and the addition of AZD6244 showed that the top 20 gene sets downregulated were all related to replication and cell cycle (ie FOXM1, CyclinE). RPPA confirmed that combination was more effective in decreasing cell cycle promoting proteins (ie FOXM1, Cyclin B1) and upregulating p27. AZD6244 treatment of OVCA lines resulted in differential expression of about ¼ of the breast cancer defined MAPK gene expression signature, and of these, fulvestrant addition to MEK inhibition (MEKi) differentially affected 19 genes, reflective of these being E2 regulated genes. Similarly, of the total MEKi affected genes, a subset were differentially regulated by the addition of fulvestrant indicating putative E2 regulation underlying these genes. Xenograft data showed the greatest decrease in tumor volume with the drug combination compared to either drug alone.

CONCLUSION: Given the majority of primary OVCAs express high MEK/MAPK activity may underlie failure of anti-estrogen therapy. MEK inhibition reverses anti-estrogen resistance in our OVCA models. These data support further pre-clinical and clinical evaluation of combined fulvestrant and MEK inhibition in OVCA.

Citation Format: K. Hew, P. Miller, J. Sun, Z. Wei, G. Zhang, Y. Lu, G. Mills, J. Slingerland, MD, PhD, D. El-Ashry, F. Simpkins. MEK inhibition reverses antiestrogen resistance in ovarian cancer (OVCA) via alteration of cell cycle pathways and MAPK/estrogen regulated gene expression [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr AS31.

Cytoplasmic p27 promotes epithelial-mesenchymal transition and tumor metastasis via STAT3-mediated Twist1 upregulation

p27 restrains normal cell growth, but PI3K-dependent C-terminal phosphorylation of p27 at threonine 157 (T157) and T198 promotes cancer cell invasion. Here, we describe an oncogenic feedforward loop in which p27pT157pT198 binds Janus kinase 2 (JAK2) promoting STAT3 (signal transducer and activator of transcription 3) recruitment and activation. STAT3 induces TWIST1 to drive a p27-dependent epithelial-mesenchymal transition (EMT) and further activates AKT contributing to acquisition and maintenance of metastatic potential. p27 knockdown in highly metastatic PI3K-activated cells reduces STAT3 binding to the TWIST1 promoter, TWIST1 promoter activity and TWIST1 expression, reverts EMT and impairs metastasis, whereas activated STAT3 rescues p27 knockdown. Cell cycle-defective phosphomimetic p27T157DT198D (p27CK-DD) activates STAT3 to induce a TWIST1-dependent EMT in human mammary epithelial cells and increases breast and bladder cancer invasion and metastasis. Data support a mechanism in which PI3K-deregulated p27 binds JAK2, to drive STAT3 activation and EMT through STAT3-mediated TWIST1 induction. Furthermore, STAT3, once activated, feeds forward to further activate AKT.

Phase 2 study of neoadjuvant treatment with NOV-002 in combination with doxorubicin and cyclophosphamide followed by docetaxel in patients with HER-2 negative clinical stage II-IIIc breast cancer

NOV-002 (a formulation of disodium glutathione disulfide) modulates signaling pathways involved in tumor cell proliferation and metastasis and enhances anti-tumor immune responsiveness in tumor models. The addition of NOV-002 to chemotherapy has been shown to increase anti-tumor efficacy in animal models and some early phase oncology trials. We evaluated the clinical effects of NOV-002 in primary breast cancer, whether adding NOV-002 to standard preoperative chemotherapy increased pathologic complete response rates (pCR) at surgery, and determined whether NOV-002 mitigated hematologic toxicities of chemotherapy and whether levels of myeloid derived suppressor cells (MDSC) were predictive of response. Forty-one women with newly diagnosed stages II-IIIc HER-2 negative breast cancer received doxorubicin-cyclophosphamide followed by docetaxel (AC → T) every 3 weeks and concurrent daily NOV-002 injections. The trial was powered to detect a doubling of pCR rate from 16 to 32% with NOV-002 plus AC → T (α = 0.05, β = 80%). Weekly complete blood counts were obtained as well as circulating MDSC levels on day 1 of each cycle were quantified. Of 39 patients with 40 evaluable tumors, 15 achieved a pCR (38%), meeting the primary endpoint of the trial. Concurrent NOV-002 resulted in pCR rates for AC → T chemotherapy higher than previously reported. Patients with lower levels of circulating MDSCs at baseline and on the last cycle of chemotherapy had significantly higher probability of a pCR (P = 0.02). Further evaluation of NOV-002 in a randomized study is warranted.

Abstract P3-11-09: Body Mass Index (BMI) and Survival: A Retrospective Review of Women with Triple Negative Breast Cancer (An Update)

Body Mass Index (BMI) has been reported as a risk factor for recurrence and decreased survival in women with breast cancer. At the Inter-American Breast Cancer Conference we presented data showing the effect BMI has on overall survival in women with triple negative breast cancer (TNBC). Here we present an update of this data which to our knowledge is the only study addressing the effect BMI has on outcomes in TNBC. We conducted a retrospective review of 170 patients with TNBC seen at the University of Miami Sylvester Comprehensive Cancer Center and Jackson Memorial Hospital between December of 1999 and April 2010. Charts were reviewed looking at BMI at the time of diagnosis and overall survival defined as date of last contact or date of death when known. 163 patients were included in the study. BMI was defined as normal (BMI 18.5-24.9) and overweight or obese (25 or greater). The average age at diagnosis was 50.96 years with a mean OS of 44.67 months. 21 patients (13%) had stage I disease, 61 (37.4%) had stage II disease, 81 (49.6%) had stage III disease. In patients with stage I disease 33% had a normal BMI with a mean OS of 51.7 months. 67% were overweight or obese with a mean OS of 60.2 months. In patients with stage II disease 33% had a normal BMI with a mean OS of 30.8 months. 67% were overweight or obese with a mean OS of 48.4 months. In patients with stage III disease 28% had a normal BMI with a mean OS of 37.2 months. 72% were overweight or obese with a mean OS of 43.1 months.

Survival in patients with TNBC does not appear to be negatively impacted by the patients BMI at diagnosis. While not statistically significant (p=0.274) patients with stage I TNBC that were overweight or obese tended to have an increased OS compared to those with a normal BMI. In patients with stage II disease there was a statistically significant (p=0.010) increase in OS in overweight or obese patients compared to those with a normal BMI. In the patients with stage III disease there was no significant difference in the OS (p=0.458) between patients with a normal BMI and those that were overweight or obese.

Our study shows that increased BMI at the time of diagnosis may have a positive impact on OS in patients with TNBC. Overweight and obese patients with stage I and II TNBC have an increased OS compared to those with a normal BMI. In those with stage II disease the difference was statistically significant. Although this study was limited by small sample size, if confirmed, it might suggest a relationship between obesity and survival in TNBC. Further studies are needed to evaluate these findings.

Abstract P1-11-05: Phase 2 Study of Neoadjuvant Treatment with Cellular Redox Modulator NOV-002 in Combination with Doxorubicin and Cyclophosphamide Followed by Docetaxel (AC→T) in Patients with Stage II-III HER-2 (-) Breast Cancer

Background: NOV-002 (a formulation of disodium glutathione disulfide) modulates signaling pathways involved in tumor cell proliferation and metastasis and enhances anti-tumor immune responsiveness in tumor models. The addition of NOV-002 to a range of cytotoxic chemotherapeutic regimens has been shown to increase their anti-tumor efficacy in several early phase oncology trials and in animal models. Pathological complete response (pCR) has been demonstrated to be associated with favorable overall survival in primary breast cancer, and neoadjuvant treatment of early breast cancer aims at achieving high rates of pCR. In patients with HER-2 (-) breast cancer pCR rates with anthracycline and taxane combinations have been reported to be approximately 10-20% depending on hormone receptor status. We conducted a clinical trial in HER-2 negative patients (pts) combining daily N0V-002 with AC→T. Methods: Women with newly diagnosed stages II-III HER-2 (-) breast cancer received AC x 4 [60/600 mg/m2] followed by T [100 mg/m2] x 4 every 3 weeks in conjunction with daily N0V-002 [60mg IV day 1 and subcutaneously days 2-21 of each cycle]. The primary endpoint is pCR, defined as: (i) ypN0, and (ii) ypT0 or presence of invasive tumor <10mm.

Sample size (n=46 total patients) was calculated using a Simon 2-stage optimal design assuming a doubling of the historical pCR rate with the addition of NOV-002 to AC→T from a p0 of 0.16 to a p1 of 0.32. If a total of 12 or more patients experience a pCR by the end of the trial, then the treatment regimen will be declared active. The calculation assumes an alpha of 0.05 and 80% power.

Results: A total of 39 pts have been enrolled to date across three study sites, with 31 patients having completed chemotherapy and undergone surgery. One patient dropped out during cycle 1 and was not assessable for response; 5 are currently receiving chemotherapy; and 2 patients have completed all chemotherapy, but have not yet undergone surgery. A total of 292 chemotherapy cycles have been administered, with 92% of all patients being able to complete all 8 cycles of planned chemotherapy. Of the 31 evaluable patients, 12 achieved a pCR (39%), meeting the primary endpoint of the trial. In patients with residual invasive primary breast tumor <10mm and ypN0 (19%) mean residual tumor size was 4.4 mm. Interestingly, of the 17 patients with biopsy-proven axillary involvement, 4 (23%) had no residual invasive tumor in axillary nodes at time of surgery. In 26 patients with estrogen positive breast cancer, which is least sensitive to chemotherapy, 42% achieved a pCR. The most common toxicities included: nausea, sensory neuropathy, emesis, fatigue, and hand-foot syndrome. Conclusions: The addition of NOV-002 has to date resulted in a doubling of previously published pCR rates with AC→T in HER-2 (-) breast cancer patients. Subsequent investigation of NOV-002 in conjunction with neoadjuvant chemotherapy in breast cancer is warranted. Updated clinical data on all 39 patients as well as immunologic correlative markers will be presented.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-11-05.

Abstract P2-19-03: Src Kinase Inhibition with AZD0530 Plus Anastrozole in Postmenopausal Hormone Receptor Positive (HR+) Metastatic Breast Cancer (MBC)

Background: p27 is a negative regulator of cell cycle that is frequently decreased in primary human breast cancer (BC) due to accelerated proteolysis. In HR+ BC, p27 function is required to promote G1 arrest following anti-estrogen treatment. cSrc is overexpressed/activated in up to 70% of BC. Src kinase phosphorylates p27 reducing its inhibitory function toward cyclin E-Cdk2, thereby facilitating p27 degradation. AZD0530 is a potent, orally available dual inhibitor of Abl and Src family kinases. Preclinical data indicate AZD0530 cooperates with anastrozole to inhibit BC cell growth in vitro and in vivo (Chen, et al., Clin Cancer Res 2009). We hypothesized that Src inhibition would augment p27 to promote antiproliferative effects of anastrozole in HR+ BC. Methods: This is an NCI funded investigator-initiated, open label phase IB clinical trial conducted under an investigator IND. Target population: postmenopausal HR+ relapsed or MBC who are candidates for aromatase inhibitor therapy. Key Inclusion: postmenopausal females, age ≥18, advanced or locally relapsed unresectable HR+ measurable/evaluable (RECIST) disease, ECOG 0-2, informed consent. Cohorts of 3 patients were initiated with AZD0530 175mg PO/day in combination with anastrozole 1mg PO daily in a planned dose de-escalation study design with subsequent cohort expansion to 12 subjects for PK assessment (both AZD0530 and anastrozole) performed at 6, 12, 24, 48, and 72 hours, 8, 15 and 22 days.

Results: Among 12 patients enrolled, AZD0530 plus anastrozole was well tolerated (no dose limiting toxicities) without need for dose de-escalation. Drug related adverse events: grade 3 lymphopenia (N=3), neutropenia (N=2), anemia (N=1) and reversible grade 1/2 transaminase elevation (N=9). Serious adverse events were observed in 2 patients (urosepsis and CNS hemorrhage due to CNS metastasis), neither considered drug-related. Interstitial pneumonitis was not observed. PK assessment: mean day 21 serum concentration = 298±38.4 ng/ml for AZD0530 and 51±5.6 ng/ml for anastrozole, indicating no evidence for drug-drug interaction between the 2 agents. Clinical efficacy: There were no RECIST clinical responses in this heavily pretreated population. However, notably patients with bone metastasis reported improvement in bone pain, and 2 patients had prolonged disease stability (>7 and 10 months with improvement of PET and bone scans) despite prior hormone refractory disease. Conclusions: Src kinase inhibition with AZD0530 combined with anastrozole was well tolerated without significant PK interaction. The recommended phase II dose is AZD0530 175mg PO plus anastrozole 1mg PO daily. A randomized phase II study of this combination is currently underway in the neoadjuvant setting including complete PK/PD assessment and molecular correlative studies to evaluate predictors of response. Supported by NIH 1R21CA133884-01A1

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-19-03.

Dose-dense docetaxel, carboplatinum and trastuzumab (ddTCH) as neoadjuvant therapy for human epidermal receptor 2 (HER2) positive breast cancer

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Background: Docetaxel, cisplatin, and trastuzumab given every 21 days in Her 2-postitive breast cancer demonstrates a pathologic complete response (pCR) rate of 23%. Decreasing the interval between doses of chemotherapy has lead to improvement in survival in the adjuvant setting. In one study dose dense chemotherapy improved response only in patients whose tumors overexpressed her-2. We conducted a phase II trial to evaluate the efficacy and safety of neoadjuvant dose-dense TCH for HER 2-positive breast cancer. Methods: Patients with T2–4 N0–3 M0 HER-2 positive (by FISH) breast cancers were eligible. Neoadjuvant therapy consisted of carboplatinum (AUC 6) Day 1,15,29,43, docetaxel (75mg/m2) Day 1,15,29, 43 and weekly trastuzumab for 10 weeks 4mg/kg Day 1 then 2mg/kg Day 8,15,22,29,36,43,50,57,64, Pegfilgastrim Day 2,16,30,44. The primary end point was the rate of pCR. Results: Twenty patients are evaluable for response. The median age was 51.5 years (range 29–73). Mean tumor size was 5.6 cm. Patients had stage IIA (30%), IIB (15%), IIIA (45%), IIIB (5%), and IIIC (5%). Estrogen receptors were positive in 36% of tumors. No grade 4 or 5 toxicity occurred. The most frequent toxicity was hand-foot syndrome (Grade I 15%, Grade II 10%, Grade III 15%). Neutropenia occurred in 5 patients (Grade II 10%, Grade III 15%) There were no episodes of febrile neutropenia or hospitalizations. Grade I cardiotoxicity was seen in 30%. The rate of pCR was 40% in the breast and 35% in both breast and axilla. 16/20 patients (80%) had pathologically negative lymph nodes. Conclusions: Changing the scheduling of TCH from every 21 days to every 14 days improves the pCR rate from 23 to 40%. The regimen was well tolerated.

No significant financial relationships to disclose.

Split, low-dose docetaxel (D) and low-dose capecitabine (C) is an active regimen in metastatic breast cancer with minimal toxicity

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Background: Successful therapeutic regimens in metastatic breast cancer must balance efficacy and tolerability. D and C is an active and commonly used doublet in this setting. D upregulates thymidine phosphorylase and thus potentiates the anti-tumor effects of C. A schedule with split, low-dose D in combination with low dose C could improve the therapeutic index of this regimen without compromising its clinical activity. Methods: Patients with previously untreated her2-neu negative metastatic breast cancer were included. A Simon 2-stage Phase II clinical trial was designed to assess the response rate (primary end-point), and toxicity of docetaxel 25 mg/m2 on days 1 and 8 in combination with capecitabine 750 mg/m2 bid on days 1–14 of a 21-day cycle. RECIST criteria were used for response assessment, which was performed every 2 cycles. Results: Thirty-one women have been enrolled. Median age was 55. Twenty patients had hormone receptor positive disease. Sites of metastasis were as follows: bone, 24 patients; liver, 14; lungs or pleura 14. A total of 189 cycles have been delivered (median: 4 cycles, range 1–33). Grade 3 and 4 toxicities were as follows: peripheral neuropathy, 2 patients; edema, 1 patient; skin, 1 patient. Two women had fever without neutropenia. Another patient had a gastric perforation but recovered without sequela. Twenty-two patients are available for response evaluation. One patient with a single bone metastasis had a complete response after chemotherapy followed by radiation. Partial responses were seen in 10 patients, for an overall response rate of 50% (95% CI, 30 to 70). Four women had stable disease and 7 had progressed at the time of first assessment. With a median follow-up of 15 months (range 1–26), the median time to treatment failure (all patients) was 7 months (range 1–26+). Median survival has not yet been reached. Out of 8 patients older than 65, seven were evaluable and 4 had a partial response. Conclusions: Split, low-dose Docetaxel and low-dose Capecitabine is an effective combination in the first-line treatment of patients with metastatic breast cancer. Toxicity with this schedule was minimal, making it an attractive regimen for further study.

[Table: see text]

p27 deregulation in breast cancer: prognostic significance and implications for therapy

p27 is a key regulator of G1-to-S phase progression. It prevents premature activation of cyclin E-cdk2 in G1 and promotes the assembly and activation of D-type cyclin-cdks. While the p27 gene is rarely mutated in human cancers, the action of p27 is impaired in breast and other human cancers through accelerated p27 proteolysis, sequestration by cyclin D-cdks, and by p27 mislocalization in tumor cell cytoplasm. Reduced p27 protein is strongly associated with high histopathologic tumor grade, reflecting a lack of tumor differentiation. Loss of p27 is also an indicator of poor patient outcome in a majority of breast cancer studies, including node negative disease. The broad application of p27 in the clinical evaluation of breast cancer prognosis will require a consensus on methods of tumor fixation, staining, and scoring. This review will focus on mechanisms of p27 regulation in normal cells and how deregulation of p27 may arise in breast and other human cancers. The prognostic significance of p27 in human breast cancer and the possible therapeutic implications of these findings will also be reviewed.

Constitutive MEK/MAPK activation leads to p27(Kip1) deregulation and antiestrogen resistance in human breast cancer cells

Antiestrogens, such as the drug tamoxifen, inhibit breast cancer growth by inducing cell cycle arrest. Antiestrogens require action of the cell cycle inhibitor p27(Kip1) to mediate G1 arrest in estrogen receptor-positive breast cancer cells. We report that constitutive activation of the mitogen-activated protein kinase (MAPK) pathway alters p27 phosphorylation, reduces p27 protein levels, reduces the cdk2 inhibitory activity of the remaining p27, and contributes to antiestrogen resistance. In two antiestrogen-resistant cell lines that showed increased MAPK activation, inhibition of the MAPK kinase (MEK) by addition of U0126 changed p27 phosphorylation and restored p27 inhibitory function and sensitivity to antiestrogens. Using antisense p27 oligonucleotides, we demonstrated that this restoration of antiestrogen-mediated cell cycle arrest required p27 function. These data suggest that oncogene-mediated MAPK activation, frequently observed in human breast cancers, contributes to antiestrogen resistance through p27 deregulation.

Skp2 is oncogenic and overexpressed in human cancers

Skp2 is a member of the F-box family of substrate-recognition subunits of SCF ubiquitin-protein ligase complexes that has been implicated in the ubiquitin-mediated degradation of several key regulators of mammalian G(1) progression, including the cyclin-dependent kinase inhibitor p27, a dosage-dependent tumor suppressor protein. In this study, we examined Skp2 and p27 protein expression by immunohistochemistry in normal oral epithelium and in different stages of malignant oral cancer progression, including dysplasia and oral squamous cell carcinoma. We found that increased levels of Skp2 protein are associated with reduced p27 in a subset of oral epithelial dysplasias and carcinomas compared with normal epithelial controls. Tumors with high Skp2 (>20% positive cells) expression invariably showed reduced or absent p27 and tumors with high p27 (>20% positive cells) expression rarely showed Skp2 positivity. Increased Skp2 protein levels were not always correlated with increased cell proliferation (assayed by Ki-67 staining), suggesting that alterations of Skp2 may contribute to the malignant phenotype without affecting proliferation. Skp2 protein overexpression may lead to accelerated p27 proteolysis and contribute to malignant progression from dysplasia to oral epithelial carcinoma. Moreover, we also demonstrate that Skp2 has oncogenic potential by showing that Skp2 cooperates with H-Ras(G12V) to malignantly transform primary rodent fibroblasts as scored by colony formation in soft agar and tumor formation in nude mice. The observations that Skp2 can mediate transformation and is up-regulated during oral epithelial carcinogenesis support a role for Skp2 as a protooncogene in human tumors.

Deregulation of the cell cycle in cancer

Mitogenic and growth-inhibitory signals influence cell-cycle progression through their action on a family of cyclin-dependent kinases (cdks). The activity of cdk complexes is regulated in part by the association of a cyclin partner that acts as a positive effector and by two families of cdk inhibitors, the kinase inhibitor proteins (KIP) and the inhibitors of cdk4 (INK4), which act as negative effectors. In human malignancies, increased expression of cyclins is frequently observed. Cyclin D1 and E are frequently overexpressed in breast cancers, and cyclin E overexpression has been correlated with a poor prognostic outcome. The abrogated expression or the acquisition of mutations that render cdk inhibitors functionally inactive have similarly been found in human malignancies. The p16 gene is frequently deleted or mutated in cancers. Although normal epithelial cells express high levels of p27 protein, reduced levels of p27 have been observed in several human cancers, and this has been consistently correlated with a poor prognostic outcome. In this review, we will provide a brief overview of the cell cycle regulators and then discuss their deregulation in cancers.

PTEN deficiency: a role in mammary carcinogenesis

The PTEN gene is often mutated in primary human tumors and cell lines, but the low rate of somatic PTEN mutation in human breast cancer has led to debate over the role of this tumor suppressor in this disease. The involvement of PTEN in human mammary oncogenesis has been implicated from studies showing that germline PTEN mutation in Cowden disease predisposes to breast cancer, the frequent loss of heterozygosity at the PTEN locus, and reduced PTEN protein levels in sporadic breast cancers. To assay the potential contribution of PTEN loss in breast tumor promotion, Li et al. [1] crossed Pten heterozygous mice with mouse mammary tumor virus-Wnt-1 transgenic (Wnt-1 TG, Pten+/-) mice. Mammary ductal carcinoma developed earlier in Wnt-1 TG, Pten+/- mice than in mice bearing either genetic change alone, and showed frequent loss of the remaining wild-type PTEN allele. These data indicate a role for PTEN in breast tumorigenesis in an in vivo model.

Germline BRCA1/2 mutations and p27(Kip1) protein levels independently predict outcome after breast cancer

PURPOSE

Decreased levels of the cyclin-dependent kinase inhibitor p27(Kip1) in breast cancer are associated with a poor outcome. The prognostic significance of BRCA1/2 mutations is less clear, and the relationship between BRCA1/2 mutation status, p27(Kip1) protein levels, and outcome has not been studied.

PATIENTS AND METHODS

Pathology blocks from 202 consecutive Ashkenazi Jewish women with primary invasive breast cancer were studied. Tumor DNA was tested for the three common BRCA1/2 founder mutations present in Ashkenazi Jews, and p27(Kip1) expression was evaluated by immunohistochemistry. The median follow-up was 6.4 years.

RESULTS

Thirty-two tumors (16%) were positive for a BRCA1/2 mutation. Low p27(Kip1) expression was seen in 110 tumors (63%) and was significantly associated with BRCA1/2 mutations (odds ratio, 4.0; 95% confidence interval [CI], 1.4 to 11.1; P =.009). BRCA1/2 mutation carriers had a significantly worse 5-year distant disease-free survival (DDFS) compared with women without BRCA1/2 mutations (58% v 82%; P =.003). Similar results were seen for women whose tumors expressed low levels of p27(Kip1), compared with those with high levels (5-year DDFS, 68% v 93%; P<.0001). In a multivariate analysis, both BRCA1/2 mutation and low p27(Kip1) expression were associated with a shorter DDFS (relative risk [RR], 2.1; 95% CI, 1.0 to 4.3; P =.05; and RR, 3.9; 95% CI, 1.4 to 11.1; P =.01, respectively).

CONCLUSION

In this study, we showed that BRCA1/2 mutations were associated with low levels of p27(Kip1) in breast cancer. Both BRCA1/2 and p27(Kip1) status were identified as independent prognostic factors.

Reduction of Cdc25A contributes to cyclin E1-Cdk2 inhibition at senescence in human mammary epithelial cells

Replicative senescence may be an important tumor suppressive mechanism for human cells. We investigated the mechanism of cell cycle arrest at senescence in human mammary epithelial cells (HMECs) that have undergone a period of 'self-selection', and as a consequence exhibit diminished p16INK4A levels. As HMECs approached senescence, the proportion of cells with a 2N DNA content increased and that in S phase decreased progressively. Cyclin D1-cdk4, cyclin E-cdk2 and cyclin A-cdk2 activities were not abruptly inhibited, but rather diminished steadily with increasing population age. In contrast to observations in fibroblast, p21Cip1 was not increased at senescence in HMECs. There was no increase in p27Kip1 levels nor in KIP association with targets cdks. While p15INK4B and its binding to both cdk4 and cdk6 increased with increasing passage, some cyclin D1-bound cdk4 and cdk6 persisted in senescent cells, whose inhibition could not be attributed to p15INK4B. The inhibition of cyclin E-cdk2 in senescent HMECs was accompanied by increased inhibitory phosphorylation of cdk2, in association with a progressive loss of Cdc25A. Recombinant Cdc25A strongly reactivated cyclin E-cdk2 from senescent HMECs suggesting that reduction of Cdc25A contributes to cyclin E-cdk2 inhibition and G1 arrest at senescence. Although ectopic expression of Cdc25A failed to extend the lifespan of HMECs, the exogenous Cdc25A appeared to lack activity in these cells, since it neither shortened the G1-to-S phase interval nor activated cyclin E-cdk2. In contrast, in the breast cancer-derived MCF-7 line, Cdc25A overexpression increased both cyclin E-cdk2 activity and the S phase fraction. Thus, mechanisms leading to HMEC immortalization may involve not only the re-induction of Cdc25A expression, but also activation of this phosphatase.

UVB induced cell cycle checkpoints in an early stage human melanoma line, WM35

The activation of cell cycle checkpoints in response to genotoxic stressors is essential for the maintenance of genomic integrity. Although most prior studies of cell cycle effects of UV irradiation have used UVC, this UV range does not penetrate the earth's atmosphere. Thus, we have investigated the mechanisms of ultraviolet B (UVB) irradiation-induced cell cycle arrest in a biologically relevant target cell type, the early stage human melanoma cell line, WM35. Irradiation of WM35 cells with UVB resulted in arrests throughout the cell cycle: at the G1/S transition, in S phase and in G2. G1 arrest was accompanied by increased association of p21 with cyclin E/cdk2 and cyclin A/cdk2, increased binding of p27 to cyclin E/cdk2 and inhibition of these kinases. A loss of Cdc25A expression was associated with an increased inhibitory phosphotyrosine content of cyclin E- and cyclin A-associated cdk2 and may also contribute to G1 arrest following UVB irradiation. The association of Cdc25A with 14-3-3 was increased by UVB. Reduced cyclin D1 protein and increased binding of p21 and p27 to cyclin D1/cdk4 complexes were also observed. The loss of cyclin D1 could not be attributed to inhibition of either MAPK or PI3K/PKB pathways, since both were activated by UVB. Cdc25B levels fell and the remaining protein showed an increased association with 14-3-3 in response to UVB. Losses in cyclin B1 expression and an increased binding of p21 to cyclin B1/cdk1 complexes also contributed to inhibition of this kinase activity, and G2/M arrest. Oncogene (2000) 19, 4480 - 4490.

Down-regulation of p21WAF1/CIP1 or p27Kip1 abrogates antiestrogen-mediated cell cycle arrest in human breast cancer cells

Estrogens and antiestrogens influence the G(1) phase of the cell cycle. In MCF-7 breast cancer cells, estrogen stimulated cell cycle progression through loss of the kinase inhibitor proteins (KIPs) p27 and p21 and through G(1) cyclin-dependent kinase (cdk) activation. Treatment with antiestrogen drugs, Tamoxifen or ICI 182780, caused cell cycle arrest, with up-regulation of both p21 and p27 levels, an increase in their binding to cyclin E-cdk2, and kinase inhibition. The requirement for these KIPs in the arrests induced by estradiol depletion or by antiestrogens was investigated with antisense. Antisense inhibition of p21 or p27 expression in estradiol-depleted or antiestrogenarrested MCF-7 led to abrogation of cell cycle arrest, with loss of cyclin E-associated KIPs, activation of cyclin E-cdk2, and S phase entrance. These data demonstrate that depletion of either p21 or p27 can mimic estrogen-stimulated cell cycle activation and indicate that both of these KIPs are critical mediators of the therapeutic effects of antiestrogens in breast cancer.

p16INK4A mediates cyclin dependent kinase 4 and 6 inhibition in senescent prostatic epithelial cells

The senescence checkpoint constrains the proliferative potential of normal cells in culture to a finite number of cell doublings. In this study, we investigated the mechanism of cyclin dependent kinase (cdk) inhibition in senescent human prostatic epithelial cells (HPECs). Progression of HPECs from early passage to senescence was accompanied by a gradual loss of cells in S phase and an accumulation of cells containing 2N DNA. Furthermore, G1-S phase-associated kinase activities progressively diminished with increasing cell passage. In senescent HPECs, cdk4 and cyclin E1- and A-associated kinases were catalytically inactive. In contrast to observations in senescent fibroblasts, levels of the kinase inhibitor protein (KIP) inhibitor p21CIP1 diminished over the proliferative life span of HPECs. p27KIP1 levels fell as cells approached senescence, and the association of both p21CIP1 and p27KIP1 with cdk4/6 complexes was decreased. However, the level of cyclin E1-associated KIP molecules was unaltered as cells progressed into senescence. Progression to senescence was accompanied by a progressive increase in both the level of p16(INK4A) and in its association with cdk4 and cdk6. As HPECs approached senescence, cdk4- and cdk6-bound p16(INK4A) showed a shift to a slower mobility due to a change in its phosphorylation profile. As p16(INK4A) increased in cdk4 and cdk6 complexes, there was a loss of cyclin D1 binding. The altered phosphorylation of p16(INK4A) in senescent prostatic epithelial cells may facilitate its association with cdk4 and cdk6 and play a role in the inactivation of these kinases.

Stem cell factor inhibits erythroid differentiation by modulating the activity of G1-cyclin-dependent kinase complexes: a role for p27 in erythroid differentiation coupled G1 arrest

Terminal erythroid differentiation is accompanied by decreased expression of c-Kit and decreased proliferation of erythroid progenitor cells. Using a newly established erythroleukemia cell line HB60-5, which proliferates in response to erythropoietin (Epo) and stem cell factor (SCF) and differentiates when stimulated with Epo alone, we characterized several events associated with the cell cycle during erythroid differentiation. Forty-eight h after SCF withdrawal and Epo stimulation, there was strong inhibition of cyclin-dependent kinase (cdk) 4 and cdk6 activities, associated with an increase in the binding of p27 and p15 to cdk6. A significant increase in the binding of p27 to cyclin E- and cyclin A-associated cdk2 correlated with the inhibition of these kinases. In addition, the expression of c-Myc and its downstream transcriptional target Cdc25A were found to be down-regulated during Epo-induced terminal differentiation of HB60-5 cells. The loss of Cdc25A was associated with an increase in the phosphotyrosylation of cyclin E-associated cdk2, which may contribute to cell cycle arrest during differentiation. Although overexpression of p27 in HB60-5 cells caused G1 arrest, it did not promote terminal erythroid differentiation. Thus, the cell cycle arrest that involves p27 is part of a broader molecular program during HB60-5 erythroid differentiation. Moreover, we suggest that SCF stimulation of erythroblasts, in addition to inhibiting erythroid differentiation, activates parallel or sequential signals responsible for maintaining cyclin/cdk activity.

Regulation of the cdk inhibitor p27 and its deregulation in cancer

p27 is a cell cycle inhibitor whose cellular abundance increases in response to many antimitogenic stimuli. In this review, we summarize the current knowledge on p27 function and its regulation by synthesis and by ubiquitin-mediated degradation. Importantly, p27 degradation is enhanced in many aggressive human tumors. The frequency with which this is observed suggests that loss of p27 may confer a growth advantage to these cancers. From a practical point of view, immunodetection of p27 in tumors may prove to be useful in the assessment of prognosis and may ultimately influence the therapy of this disease.

Regulation of the cdk inhibitor p27 and its deregulation in cancer

p27 is a cell cycle inhibitor whose cellular abundance increases in response to many antimitogenic stimuli. In this review, we summarize the current knowledge on p27 function and its regulation by synthesis and by ubiquitin-mediated degradation. Importantly, p27 degradation is enhanced in many aggressive human tumors. The frequency with which this is observed suggests that loss of p27 may confer a growth advantage to these cancers. From a practical point of view, immunodetection of p27 in tumors may prove to be useful in the assessment of prognosis and may ultimately influence the therapy of this disease.

Regulation of the cdk inhibitor p27 and its deregulation in cancer

p27 is a cell cycle inhibitor whose cellular abundance increases in response to many antimitogenic stimuli. In this review, we summarize the current knowledge on p27 function and its regulation by synthesis and by ubiquitin-mediated degradation. Importantly, p27 degradation is enhanced in many aggressive human tumors. The frequency with which this is observed suggests that loss of p27 may confer a growth advantage to these cancers. From a practical point of view, immunodetection of p27 in tumors may prove to be useful in the assessment of prognosis and may ultimately influence the therapy of this disease.

Involvement of p27Kip1 in G1 arrest by high dose 5 alpha-dihydrotestosterone in LNCaP human prostate cancer cells

The cell cycle is governed by cyclin dependent kinases (cdks), which are activated by binding of cyclins, inhibited by cdk inhibitors and regulated by phosphorylation and dephosphorylation. Exposure to high dose dihydrotestosterone (DHT) inhibits population growth of the human prostate carcinoma cell line, LNCaP. To determine the mechanism of growth arrest by high dose DHT, we assayed the changes in cell cycle profile and the cell cycle regulators that mediate these effects. Treatment of asynchronously growing LNCaP cells with 100 nM DHT caused a G1 arrest. The proportion of cells in S phase fell from 22 to 2%, while the G1 fraction rose from 74 to 92% by 24 h. Loss of phosphorylation of the retinoblastoma protein was noted and cdk4 and cyclin E/ cdk2 activities fell. Inhibition of these G1 cyclin dependent kinases was not due to loss of either cyclin or cdk proteins nor to increases in the cdk inhibitors p16INK4A and p21CiP1. p21Cip1 protein levels remained constant, and cyclin E-associated p21CiP1 fell, suggesting that p21CiP1 is not relevant to this form of cyclin E/cdk2 inhibition. Of note, total p27KiP1 levels and cyclin E-associated p27Kip1 increased as cells arrested and the amount of the CAK activated cdk2 bound to cyclin E decreased. p27KiP1 immunodepletion experiments demonstrated that the DHT-mediated increase in p27Kip1 was sufficient to fully saturate and inhibit target cyclin E/ cdk2. The inhibition of cyclin E/cdk2 by p27Kip1 contributes to G1 arrest of LNCaP following high dose DHT. p27KiP1 may be a key effector of androgen dependent growth modulation in prostate cancer cells.

The prognostic significance of altered cyclin-dependent kinase inhibitors in human cancer

Progression through the cell cycle is governed by cyclin-dependent kinases (cdks), whose activity is inhibited by the cdk inhibitors. Cyclins, cdks, and cdk inhibitors are frequently deregulated in cancers. This chapter reviews the prognostic significance of alterations in cdk inhibitors. Loss of p27 protein provides independent prognostic information in breast, prostate, colon, and gastric carcinomas, and immunohistochemical (IHC) staining for p27 may eventually become part of routine histopathologic processing of cancers. Loss of IHC staining for p21 may be prognostic in certain cancers but conflicting results are reported in breast cancer. Reports on homozygous deletion of p16 and p15 genes suggest the value of larger, prospective studies with standardized treatment protocols to definitively establish the prognostic utility of p15/p16 deletions in acute leukemias. Larger trials and the development of a consensus on methods for deletion analysis, IHC staining, and tumor scoring will be needed to move these molecular assays from bench to bedside.

Prognostic implications of expression of the cell cycle inhibitor protein p27Kip1

Mitogenic and growth inhibitory signals influence the activity of a family of cyclin dependent kinases (cdks). p27 is an important cdk inhibitor, acting in G1 to inhibit cyclin-cdks. As negative growth regulators, the cdk inhibitors may function as tumor suppressors. While the p16 gene plays a tumor suppressor role in cancers, p27 gene mutations have been identified only rarely. While high levels of p27 protein are expressed in normal human mammary epithelium, loss of p27 is frequent and is of independent prognostic significance in breast cancers. Low p27 is also a poor prognostic factor in colon, gastric, esophageal, lung, and prostate carcinomas, and enhanced proteasomal degradation may underlie loss of p27 in tumor cells. Loss of p27 has not been significantly correlated with tumor proliferation in a number of studies and may reflect alterations in differentiation and adhesion-dependent growth regulation germane to oncogenesis and tumor progression. Efforts to confirm the prognostic value of p27 are under way in a number of large breast cancer studies. These studies may also indicate whether loss of p27 in association with other traditional or novel markers has greater prognostic potential than each factor alone. p27 immunostaining is inexpensive and reliable and may become part of the routine histopathologic processing of tumors in the near future. Widespread application of p27 in prognostic testing will require greater uniformity in scoring techniques and determination of the cut off levels which distinguish individuals at high and low risk of cancer recurrence and death. Finally, the greatest utility of p27 may lie in the information it sheds on the biology of aberrant growth regulation in breast cancer and the potential to use this in the generation of novel therapeutic strategies.

Reduced expression of the cell cycle inhibitor p27Kip1 in non-small cell lung carcinoma: a prognostic factor independent of Ras

Levels of p27 have been found to have independent prognostic significance in a variety of tumors including breast, colon, prostate, ovary, and gastric carcinomas. We investigated p27 levels and determined ras mutational status in 136 non-small cell lung cancers. We found reduced levels of p27 in 86% of cases and showed a statistically significant inverse correlation between p27 levels and tumor grade. ras mutations were found exclusively in adenocarcinomas and showed no relationship to p27 levels. Clinical data on a subset of the patients studied indicated that all 16 patients who died of disease and 21 of 22 patients who relapsed had low p27 levels, whereas all patients with high p27 levels were alive at last follow up. These findings suggest that alteration in p27 levels plays an important role in lung tumor progression and that p27 levels may have independent prognostic significance in non-small cell lung cancer.

Interleukin-6 dependent induction of the cyclin dependent kinase inhibitor p21WAF1/CIP1 is lost during progression of human malignant melanoma

Human melanoma cell lines derived from early stage primary tumors are particularly sensitive to growth arrest induced by interleukin-6 (IL-6). This response is lost in cell lines derived from advanced lesions, a phenomenon which may contribute to tumor aggressiveness. We sought to determine whether resistance to growth inhibition by IL-6 can be explained by oncogenic alterations in cell cycle regulators or relevant components of intracellular signaling. Our results show that IL-6 treatment of early stage melanoma cell lines caused G1 arrest, which could not be explained by changes in levels of G1 cyclins (D1, E), cdks (cdk4, cdk2) or by loss of cyclin/cdk complex formation. Instead, IL-6 caused a marked induction of the cdk inhibitor p21WAF1/CIP1 in three different IL-6 sensitive cell lines, two of which also showed a marked accumulation of the cdk inhibitor p27Kip1. In contrast, IL-6 failed to induce p21WAF1/CIP1 transcript and did not increase p21WAF1/CIP1 or p27kip1 proteins in any of the resistant lines. In fact, of five IL-6 resistant cell lines, only two expressed detectable levels of p21WAF1/CIP1 mRNA and protein, while in three other lines, p21WAF1/CIP1 was undetectable. IL-6 dependent upregulation of p21WAF1/CIP1 was associated with binding of both STAT3 and STAT1 to the p21WAF1/CIP1 promoter. Surprisingly, however, IL-6 stimulated STAT binding to this promoter in both sensitive and resistant cell lines (with one exception), suggesting that gross deregulation of this event is not the unifying cause of the defect in p21WAF1/CIP1 induction in IL-6 resistant cells. In somatic cell hybrids of IL-6 sensitive and resistant cell lines, the resistant phenotype was dominant and IL-6 failed to induce p21WAF1/CIP1. Thus, our results suggest that in early stage human melanoma cells, IL-6 induced growth inhibition involves induction of p21WAF1/CIP1 which is lost in the course of tumor progression presumably as a result of a dominant oncogenic event.

Cyclin E2: a novel CDK2 partner in the late G1 and S phases of the mammalian cell cycle

We report here the cloning and characterization of human and mouse cyclin E2, which define a new subfamily within the vertebrate E-type cyclins, while all previously identified family-members belong to the cyclin El subfamily. Cyclin E2/CKD2 and cyclin E/CDK2 complexes phosphorylate histone H1 in vitro with similar specific activities and both are inhibited by p27Kip1. Cyclin E2 mRNA levels in human cells oscillate throughout the cell cycle and peak at the G1/S boundary, in parallel with the cyclin E mRNA. In cells, cyclin E2 is complexed with CDK2, p27 and p21. Like cyclin E, cyclin E2 is an unstable protein in vivo and is stabilized by proteasome inhibitors. Cyclin E2-associated kinase activity rises in late G1 and peaks very close to cyclin E activity. In two malignantly transformed cell lines, cyclin E2 activity is sustained throughout S phase, while cyclin E activity has already declined and cyclin A activity is only beginning to rise. We speculate that cyclin E2 is not simply redundant with cyclin E, but may regulate distinct rate-limiting pathway(s) in G1-S control.

E-Cadherin-dependent growth suppression is mediated by the cyclin-dependent kinase inhibitor p27(KIP1)

Recent studies have demonstrated the importance of E-cadherin, a homophilic cell-cell adhesion molecule, in contact inhibition of growth of normal epithelial cells. Many tumor cells also maintain strong intercellular adhesion, and are growth-inhibited by cell- cell contact, especially when grown in three-dimensional culture. To determine if E-cadherin could mediate contact-dependent growth inhibition of nonadherent EMT/6 mouse mammary carcinoma cells that lack E-cadherin, we transfected these cells with an exogenous E-cadherin expression vector. E-cadherin expression in EMT/6 cells resulted in tighter adhesion of multicellular spheroids and a reduced proliferative fraction in three-dimensional culture. In addition to increased cell-cell adhesion, E-cadherin expression also resulted in dephosphorylation of the retinoblastoma protein, an increase in the level of the cyclin-dependent kinase inhibitor p27(kip1) and a late reduction in cyclin D1 protein. Tightly adherent spheroids also showed increased levels of p27 bound to the cyclin E-cdk2 complex, and a reduction in cyclin E-cdk2 activity. Exposure to E-cadherin-neutralizing antibodies in three-dimensional culture simultaneously prevented adhesion and stimulated proliferation of E-cadherin transfectants as well as a panel of human colon, breast, and lung carcinoma cell lines that express functional E-cadherin. To test the importance of p27 in E-cadherin-dependent growth inhibition, we engineered E-cadherin-positive cells to express inducible p27. By forcing expression of p27 levels similar to those observed in aggregated cells, the stimulatory effect of E-cadherin-neutralizing antibodies on proliferation could be inhibited. This study demonstrates that E-cadherin, classically described as an invasion suppressor, is also a major growth suppressor, and its ability to inhibit proliferation involves upregulation of the cyclin-dependent kinase inhibitor p27.

Protein expression of the cell-cycle inhibitor p27Kip1 in malignant melanoma: inverse correlation with disease-free survival

In the present study we analyzed, by immunohistochemistry, a panel of human melanomas for protein expression of the cyclin-dependent kinase (cdk) inhibitor p27Kip1 and evaluated whether deregulated expression correlates with clinical outcome for this type of cancer. We found that p27Kip1 was strongly expressed by normal melanocytes and benign nevi, whereas in malignant melanoma, a heterogeneous expression pattern was observed. In the case of nodular melanomas, the level of p27Kip1 was found to correlate significantly with the thickness of the tumor, with less protein expressed in thicker lesions. We also found that patients having tumors with fewer than 5% p27Kip1-staining cells had a significantly higher risk of early relapse of their disease compared with those expressing moderate or high levels. In contrast, the level of p27Kip1 did not correlate with tumor thickness or disease-free survival in patients with superficial spreading melanomas, suggesting that p27Kip1 may play different roles in these two major pathological subgroups of malignant melanoma. Furthermore, p27Kip1 did not appear to have an influence on overall survival for either subgroup. When we examined the combined effect of p21WAF1/CIP1 (another cdk inhibitor) and p27Kip1 on clinical outcome, we found that analysis of these two cdk inhibitors together may have greater prognostic potential than either alone. In conclusion, our results suggest that virtually complete loss of p27Kip1 protein expression has potential importance as a prognostic indicator of early relapse in patients with nodular melanoma The results, furthermore, underscore the value of analyzing multiple cell cycle regulatory proteins to obtain the most reliable indication of prognosis.

Telomerase activity in prostate cancer, prostatic intraepithelial neoplasia, and benign prostatic epithelium

Telomerase is a ribonucleoprotein that synthesizes telomeric DNA on chromosomal ends. Telomerase activation has been seen in many immortal cell lines and cancers. Telomerase activity was analyzed in prostate carcinoma; in coexistent prostatic intraepithelial neoplasia (PIN), benign prostatic hyperplasia (BPH), atrophy and normal tissue; and in benign prostate glands. Telomerase activity was detected in 80 of 87 (92%) prostate cancers. Forty-one matched samples (from a total of 32 cases) were available for comparative analysis. The presence of telomerase activity in adjacent PIN, BPH, and normal tissue was correlated with telomerase activity in the malignant epithelium. In these adjacent tissues, telomerase activity was found in 11 of 15 (73%) PINs, 13 of 26 (50%) BPHs, and 1 of 6 (16%) atrophy and 4 of 11 (36%) normal tissues. In contrast to the BPH tissue from cancer-bearing glands, all 16 BPH specimens from patients only diagnosed with BPH were telomerase activity negative. In cancer samples, there was no correlation between telomerase activity and Gleason grade or preoperation prostate-specific antigen level. Our data indicate that telomerase activity is present in most prostate cancers. The high rate of telomerase activity in the benign-appearing areas of these glands may be attributed either to the presence of occult cancer cells or to early molecular alterations of cancer that were histologically inapparent.