Preclinical in vitro and in vivo activity of the RAF/MEK clamp avutometinib in combination with FAK inhibition in uterine carcinosarcomas

OBJECTIVES

Uterine carcinosarcomas (UCS) are rare, biologically aggressive tumors. Since UCS may harbor mutations in RAS/MAPK pathway genes we evaluated the preclinical in vitro and in vivo efficacy of the RAF/MEK clamp avutometinib in combination with the focal adhesion kinase (FAK) inhibitors defactinib or VS-4718 against multiple primary UCS cell lines and xenografts.

METHODS

Whole-exome-sequencing (WES) was used to evaluate the genetic landscape of 5 primary UCS cell lines. The in vitro activity of avutometinib ± FAK inhibitor was evaluated using cell viability and cell cycle assays against primary UCS cell lines. Mechanistic studies were performed using western blot assays while in vivo experiments were completed in UCS tumor bearing mice treated with avutometinib ± FAK inhibitor by oral gavage.

RESULTS

WES results demonstrated multiple UCS cell lines harbor genetic alterations including KRAS, PTK2, BRAF, MAP2K, and MAP2K1, potentially sensitizing to FAK and RAF/MEK inhibition. Four out of five of the UCS cell lines demonstrated in vitro sensitivity to FAK and/or RAF/MEK inhibition when used alone or in combination. By western blot assays, exposure of UCS cell lines to the combination of defactinib/avutometinib demonstrated decreased phosphorylated (p)-FAK as well as decreased p-ERK. In vivo, the combination of avutometinib/VS-4718 demonstrated superior tumor growth inhibition and longer survival compared to single agent treatment and controls starting at day 10 (p < 0.002) in UCS xenografts.

CONCLUSION

The combination of avutometinib and defactinib demonstrates promising in vitro and in vivo anti-tumor activity against primary UCS cell lines and xenografts.

Integrated mutational landscape analysis of poorly differentiated high-grade neuroendocrine carcinoma of the uterine cervix

High-grade neuroendocrine cervical cancers (NETc) are exceedingly rare, highly aggressive tumors. We analyzed 64 NETc tumor samples by whole-exome sequencing (WES). Human papillomavirus DNA was detected in 65.6% (42/64) of the tumors. Recurrent mutations were identified in PIK3CA, KMT2D/MLL2, K-RAS, ARID1A, NOTCH2, and RPL10. The top mutated genes included RB1, ARID1A, PTEN, KMT2D/MLL2, and WDFY3, a gene not yet implicated in NETc. Somatic CNV analysis identified two copy number gains (3q27.1 and 19q13.12) and five copy number losses (1p36.21/5q31.3/6p22.2/9q21.11/11p15.5). Also, gene fusions affecting the ACLY-CRHR1 and PVT1-MYC genes were identified in one of the eight samples subjected to RNA sequencing. To resolve evolutionary history, multiregion WES in NETc admixed with adenocarcinoma cells was performed (i.e., mixed-NETc). Phylogenetic analysis of mixed-NETc demonstrated that adenocarcinoma and neuroendocrine elements derive from a common precursor with mutations typical of adenocarcinomas. Over one-third (22/64) of NETc demonstrated a mutator phenotype of C > T at CpG consistent with deficiencies in MBD4, a member of the base excision repair (BER) pathway. Mutations in the PI3K/AMPK pathways were identified in 49/64 samples. We used two patient-derived-xenografts (PDX) (i.e., NET19 and NET21) to evaluate the activity of pan-HER (afatinib), PIK3CA (copanlisib), and ATR (elimusertib) inhibitors, alone and in combination. PDXs harboring alterations in the ERBB2/PI3K/AKT/mTOR/ATR pathway were sensitive to afatinib, copanlisib, and elimusertib (P < 0.001 vs. controls). However, combinations of copanlisib/afatinib and copanlisib/elimusertib were significantly more effective in controlling NETc tumor growth. These findings define the genetic landscape of NETc and suggest that a large subset of these highly lethal malignancies might benefit from existing targeted therapies.

Preclinical efficacy of RAF/MEK clamp avutometinib in combination with FAK inhibition in low grade serous ovarian cancer

OBJECTIVES

Low-grade-serous-ovarian-carcinoma (LGSOC) is characterized by a high recurrence rate and limited therapeutic options. About one-third of LGSOC contains mutations in MAPK pathway genes such as KRAS/NRAS/BRAF. Avutometinib is a dual RAF/MEK inhibitor while defactinib and VS-4718 are focal-adhesion-kinase-inhibitors (FAKi). We determined the preclinical efficacy of avutometinib±VS-4718 in LGSOC patient-derived-tumor-xenografts (PDX).

METHODS

Whole-exome-sequencing (WES) was used to evaluate the genetic fingerprint of 3 patient-derived LGSOC (OVA(K)250, PERIT(M)17 and A(PE)148). OVA(K)250 tissue was successfully xenografted as PDX into female CB17/lcrHsd-Prkdc/SCID-mice. Animals were treated with either control, avutometinib, VS-4718, or avutometinib/ VS-4718 once daily five days on and two days off through oral gavage. Mechanistic studies were performed ex vivo using avutometinib±defactinib treated LGSOC tumor samples by western blot.

RESULTS

WES results demonstrated wild-type KRAS in all 3 LGSOC. OVA(K)250 PDX showed gain-of-function mutations (GOF) in PTK2 and PTK2B genes, and loss-of-heterozygosity in ADRB2, potentially sensitizing to FAK and RAF/MEK inhibition. The combination of avutometinib/ VS-4718 demonstrated strong tumor-growth inhibition compared to controls starting at day 9 (p < 0.002) in OVA(K)250PDX. By 60 days, mice treated with avutometinib alone and avutometinib/VS-4718 were still alive; compared to median survival of 20 days in control-treated mice and of 35 days in VS-4718-treated mice (p < 0.0001). By western-blot assays exposure of OVA(K)250 to avutometinib, FAKi defactinib and their combination demonstrated decreased phosphorylated FAK (p-FAK) as well as decreased p-ERK.

CONCLUSION

Avutometinib, and to a larger extent its combination with FAK inhibitor VS-4718, demonstrated promising in vivo activity against a KRAS wild-type LGSOC-PDX. These data support the ongoing registration-directed study (RAMP201/NCT04625270).

Harnessing small extracellular vesicles for pro-oxidant delivery: novel approach for drug-sensitive and resistant cancer therapy

Multidrug resistance (MDR) is an inevitable clinical problem in chemotherapy due to the activation of abundant P-glycoprotein (P-gp) that can efflux drugs. Limitations of current cancer therapy highlight the need for the development of a comprehensive cancer treatment strategy, including drug-resistant cancers. Small extracellular vesicles (sEVs) possess significant potential in surmounting drug resistance as they can effectively evade the efflux mechanism and transport small molecules directly to MDR cancer cells. One mechanism mediating MDR in cancer cells is sustaining increased levels of reactive oxygen species (ROS) and maintenance of the redox balance with antioxidants, including glutathione (GSH). Herein, we developed GSH-depleting benzoyloxy dibenzyl carbonate (B2C)-encapsulated sEVs (BsEVs), which overcome the efflux system to exert highly potent anticancer activity against human MDR ovarian cancer cells (OVCAR-8/MDR) by depleting GSH to induce oxidative stress and, in turn, apoptotic cell death in both OVCAR-8/MDR and OVCAR-8 cancer cells. BsEVs restore drug responsiveness by inhibiting ATP production through the oxidation of nicotinamide adenine dinucleotide with hydrogen (NADH) and inducing mitochondrial dysfunction, leading to the dysfunction of efflux pumps responsible for drug resistance. In vivo studies showed that BsEV treatment significantly inhibited the growth of OVCAR-8/MDR and OVCAR-8 tumors. Additionally, OVCAR-8/MDR tumors showed a trend towards a greater sensitivity to BsEVs compared to OVCAR tumors. In summary, this study demonstrates that BsEVs hold tremendous potential for cancer treatment, especially against MDR cancer cells.

In Vivo and In Vitro Efficacy of Trastuzumab Deruxtecan in Uterine Serous Carcinoma

Uterine serous carcinoma (USC) is a rare, biologically aggressive variant of endometrial cancer with a high recurrence rate and poor prognosis. HER2 overexpression (3+ positivity) by IHC and/or FISH ERBB2 gene amplification is detected in approximately one-third of patients with USC. Clinical trials incorporating trastuzumab with standard chemotherapy have recently demonstrated improved progression-free and overall survival in advanced-stage or recurrent USC that overexpresses HER2. However, a large number of patients with USC eventually developed resistance to trastuzumab. Trastuzumab deruxtecan (T-DXd) is a novel HER2-directed antibody-drug conjugate with a topoisomerase I inhibitor payload recently approved by the Food and Drug Administration (FDA) for multiple tumor indications. Here, we investigated the in vitro and in vivo efficacy of T-DXd in primary USC cell lines and xenografts with different HER2 expression. T-DXd-induced cell growth suppression in HER2-overexpressing cell lines in vitro, increased early and late apoptosis as assessed by annexin and propidium iodide staining, and, similarly to trastuzumab, T-DXd-induced significant antibody-dependent cellular cytotoxicity in the presence of peripheral blood lymphocytes. While negligible activity was detected against USC cell lines with low HER2 expression, T-DXd demonstrated significant bystander killing against USC tumors with low/negligible HER2 when such cells were admixed with HER2 3+ tumor cells in vitro. T-DXd showed tumor growth suppression in in vivo USC PDX models that overexpress HER2 at 3+ levels, prolonging survival when compared with controls, with minimal toxicity. Future clinical trials are warranted in patients with USC failing trastuzumab treatment.

Monitoring Treatment Response, Early Recurrence, and Survival in Uterine Serous Carcinoma and Carcinosarcoma Patients Using Personalized Circulating Tumor DNA Biomarkers

Uterine serous carcinoma (USC) and carcinosarcomas (CSs) are rare, highly aggressive variants of endometrial cancer. No reliable tumor biomarkers are currently available to guide response to treatment or detection of early recurrence in USC/CS patients. Circulating tumor DNA (ctDNA) identified using ultrasensitive technology such as droplet digital polymerase chain reaction (ddPCR) may represent a novel platform for the identification of occult disease. We explored the use of personalized ctDNA markers for monitoring USC and CS patients. Tumor and plasma samples from USC/CS patients were collected at the time of surgery and/or during the treatment course for assessment of tumor-specific somatic structural variants (SSVs) by a clinical-grade next-generation sequencing (NGS) platform (i.e., Foundation Medicine) and a droplet digital PCR instrument (Raindance, ddPCR). The level of ctDNA was quantified by droplet digital PCR in plasma samples and correlated to clinical findings, including CA-125 serum and/or computed tomography (CT) scanning results. The genomic-profiling-based assay identified mutated "driver" target genes for ctDNA analysis in all USC/CS patients. In multiple patients, longitudinal ctDNA testing was able to detect the presence of cancer cells before the recurrent tumor was clinically detectable by either CA-125 or CT scanning. Persistent undetectable levels of ctDNA following initial treatment were associated with prolonged progression-free and overall survival. In a USC patient, CA-125 and TP53 mutations but not PIK3CA mutations become undetectable in the plasma at the time of recurrence, suggesting that more than one customized probe should be used for monitoring ctDNA. Longitudinal ctDNA testing using tumor-informed assays may identify the presence of residual tumors, predict responses to treatment, and identify early recurrences in USC/CS patients. Recognition of disease persistence and/or recurrence through ctDNA surveillance may allow earlier treatment of recurrent disease and has the potential to change clinical practice in the management of USC and CS patients. CtDNA validation studies in USC/CS patients prospectively enrolled in treatment trials are warranted.

Uterine leiomyosarcomas harboring MAP2K4 gene amplification are sensitive in vivo to PLX8725, a novel MAP2K4 inhibitor

INTRODUCTION

Uterine leiomyosarcomas (uLMS) are rare, highly aggressive tumors. Up to 30% of uLMS may harbor gain of function (GOF) in the MAP2K4 gene, important for tumor cell proliferation, differentiation and metastasis. We investigated the in vivo activity of a novel MAP2K4 inhibitor, PLX8725, against uLMS harboring MAP2K4 gene-amplification.

METHODS

Two fully characterized uLMS (i.e., LEY-11 and LEY-16) were grafted into female CB-17/SCID mice. Treatments with control vehicle or PLX8725 (50 mg/kg) were given via oral gavage daily on weekdays for up to 60 days. Tumor volume differences were calculated with two-way ANOVA. Pharmacokinetic (PK) and mechanistic studies of PLX8725 in uLMS PDX models were also performed.

RESULTS

Both uLMS tumors evaluated demonstrated GOF in MAP2K4 (i.e., 3 CNV in both LEY-11 and LEY-16). Tumor growth inhibition was significantly greater in both PDX LEY-11 and PDX LEY-16 treated with PLX8725 when compared to controls (p < 0.001). Median overall survival was also significantly longer in both PDX LEY-11 (p = 0.0047) and PDX LEY-16 (p = 0.0058) treatment cohorts when compared to controls. PLX8725 oral treatment was well tolerated, and PK studies demonstrated that oral PLX8725 gives extended exposure in mice. Ex vivo tumor samples after PLX8725 exposure decreased phosphorylated-ATR, JNK and p38, and increased expression of apoptotic molecules on western blot.

CONCLUSION

PLX8725 demonstrates promising in vivo activity against PDX models of uLMS harboring GOF alterations in the MAP2K4 gene with tolerable toxicity. Phase I trials of PLX8725 in advanced, recurrent, chemotherapy-resistant uLMS patients are warranted.

Trastuzumab deruxtecan (DS-8201a), a HER2-targeting antibody-drug conjugate with topoisomerase I inhibitor payload, shows antitumor activity in uterine and ovarian carcinosarcoma with HER2/neu expression

OBJECTIVES

Carcinosarcomas are highly aggressive gynecologic malignancies containing both carcinomatous and sarcomatous elements with heterogeneous HER2/neu expression and limited therapeutic options. We compared the efficacy of trastuzumab deruxtecan (DS-8201a), a novel HER2/neu-targeting antibody-drug conjugate (ADC) to an ADC isotype control (MAAA-9199) against primary uterine and ovarian carcinosarcomas in vitro and in vivo.

METHODS

Twelve primary carcinosarcoma (CS) cell lines were evaluated for HER2/neu surface expression by immunohistochemistry (IHC) and by flow cytometry, and gene amplification by fluorescence in situ hybridization (FISH) assays. The in vitro experiments included cytotoxicity and bystander killing effect assays on three cell lines of variable HER2/neu expression. In vivo activity was studied in a mouse CS xenograft model of 3+ HER2/neu uterine CS.

RESULTS

In vitro studies showed that DS-8201a was highly effective against uterine and ovarian CS cell lines demonstrating 3+ HER2/neu expression compared to MAAA-9199 control; there was no significant improvement in the 0 HER2/neu CS cell line. However, DS-8201a induced efficient bystander killing of 0 HER2/neu tumor cells when admixed with 3+ HER2/neu cells. In vivo studies confirmed that DS-8201a was more effective than MAAA-9199 in 3+ HER2/neu-expressing CS xenografts.

CONCLUSION

DS-8201a may represent a novel and highly effective ADC against HER2/neu-expressing CS.

The Poly (ADP-ribose) polymerase inhibitor olaparib and pan-ErbB inhibitor neratinib are highly synergistic in HER2 overexpressing epithelial ovarian carcinoma in vitro and in vivo

INTRODUCTION

Ovarian cancer (OC) is associated with the highest gynecologic cancer mortality. The development of novel, effective combinations of targeted therapeutics remains an unmet medical need. We evaluated the preclinical efficacy of the Poly (ADP-ribose) polymerase (PARP) inhibitor (olaparib) and the pan-ErbB inhibitor (neratinib) as single agents and in combination in ovarian cancer cell lines and xenografts with variable HER2 expression.

METHODS

In vitro cell viability with olaparib, neratinib, and their combination was assessed using flow-cytometry based assays against a panel of OC primary cell lines with variable HER2 expression. Immunoblotting experiments were performed to elucidate the mechanism of activity and synergism. The in vivo antitumor activity of the olaparib/neratinib combination versus single agents was tested in HER2 positive xenograft OC models.

RESULTS

HER2 + OC cell lines demonstrated higher sensitivity to olaparib and neratinib when compared to HER2 negative tumors (i.e., IC50: 2.06 ± 0.33 μM vs. 39.28 ± 30.51 μM, p = 0.0035 for olaparib and 19.42 ± 2.63 nM vs. 235.0 ± 165.0 nM, p = 0.0035 for neratinib). The combination of olaparib with neratinib was more potent when compared to single-agent olaparib or neratinib both in vitro and in vivo, and demonstrated synergy in all primary HER2 + OC models. Western blot experiments showed neratinib decreased pHER2/neu while increased Poly(ADP-ribose) (PAR) enzymatic activity; olaparib increased pHER2/Neu expression and blocked PAR activatio. Olaparib/neratinib in combination decreased both pHER2/Neu as well as PAR activation.

CONCLUSION

The combination of olaparib and neratinib is synergistic and endowed with remarkable preclinical activity against HER2+ ovarian cancers. This combination may represent a novel therapeutic option for ovarian cancer patients with HER2+, homologous recombination-proficient tumors resistant to chemotherapy.

NRF2 controls iron homeostasis and ferroptosis through HERC2 and VAMP8

Enhancing the intracellular labile iron pool (LIP) represents a powerful, yet untapped strategy for driving ferroptotic death of cancer cells. Here, we show that NRF2 maintains iron homeostasis by controlling HERC2 (E3 ubiquitin ligase for NCOA4 and FBXL5) and VAMP8 (mediates autophagosome-lysosome fusion). NFE2L2/NRF2 knockout cells have low HERC2 expression, leading to a simultaneous increase in ferritin and NCOA4 and recruitment of apoferritin into the autophagosome. NFE2L2/NRF2 knockout cells also have low VAMP8 expression, which leads to ferritinophagy blockage. Therefore, deletion of NFE2L2/NRF2 results in apoferritin accumulation in the autophagosome, an elevated LIP, and enhanced sensitivity to ferroptosis. Concordantly, NRF2 levels correlate with HERC2 and VAMP8 in human ovarian cancer tissues, as well as ferroptosis resistance in a panel of ovarian cancer cell lines. Last, the feasibility of inhibiting NRF2 to increase the LIP and kill cancer cells via ferroptosis was demonstrated in preclinical models, signifying the impact of NRF2 inhibition in cancer treatment.

Ovarian and uterine carcinosarcomas are sensitive in vitro and in vivo to elimusertib, a novel ataxia-telangiectasia and Rad3-related (ATR) kinase inhibitor

BACKGROUND

Carcinosarcoma of the ovary (OCS) and uterus (UCS) are rare highly aggressive malignancies. Ataxia-telangiectasia-and-Rad3-related (ATR) kinase and homologous recombination play a pivotal role in DNA damage repair. Homologous recombination deficiency (HRD) has been demonstrated in >30% of OCS/UCS. We investigated the preclinical activity of elimusertib, a selective ATR kinase inhibitor, against carcinosarcoma (CS) cell lines and xenografts.

METHODS

Sensitivity to elimusertib was evaluated in vitro against nine whole exome-sequenced (WES) primary CS cell lines and in vivo against HRD CS xenografts. Western blots were performed to determine baseline ATR and p-ATR protein expression in CS, and ATR pathway downstream effectors and apoptosis markers in CS HRD cell lines after Elimusertib treatment.

RESULTS

Out of the 9 CS cell lines, 3 harbored HRD and 6 homologous recombination proficient (HRP) features. Most of CS (i.e., 7/9 = 85%) were found to be sensitive to Elimusertib in vitro. Among the 5 primary CS cell lines with a high-grade pure serous epithelial component, HRD cell lines were more sensitive to elimusertib than HRP tumors (mean IC50 ± SEM HRD CS = 61.3 nM ±15.2 vs HRP = 361.6 nM ±24.4 (p = 0.01)). Baseline ATR and p-ATR protein expression was higher in HRD CS cell lines. Elimusertib showed tumor growth inhibition in HRD CS xenografts (p < 0.0001) and increased overall animal survival (p < 0.0001). Western blot demonstrated dose-dependent inhibition of ATR, p-ATR and its downstream effector p-CHK1, and a dose-dependent increase in caspase-3 expression.

CONCLUSIONS

Elimusertib is preclinically active in vitro and in vivo against primary CS cell lines and xenografts, respectively. CS models harboring HRD or with pure/mixed endometrioid histology demonstrated higher sensitivity to ATR inhibition. Clinical trials with elimusertib in CS patients are warranted.

Elimusertib (BAY1895344), a novel ATR inhibitor, demonstrates in vivo activity in ATRX mutated models of uterine leiomyosarcoma

INTRODUCTION

Uterine leiomyosarcoma (uLMS) is a rare, highly aggressive malignancy. Recent data suggest 50% of uLMS may harbor alterations in the ATRX gene and such mutations may confer sensitivity to ataxia-telangiectasia-and-Rad3-related (ATR) kinase inhibitors. We sought to investigate the in vivo activity of Elimusertib (BAY1895344), a novel ATR-inhibitor, against ATRX-mutated uLMS patient-derived xenografts (PDXs).

METHODS

Two fully characterized uLMS (i.e., LEY-11 and LEY-16) were grafted into female CB-17/SCID mice. Treatments with control vehicle or BAY1895344 (20 mg/kg dosed twice daily 3 days on 4 days off) were given via oral gavage and tumor measurements as well as weights obtained twice weekly. Tumor volume differences were calculated with a two-way ANOVA. Mechanistic studies were performed ex vivo using BAY1895344 treated uLMS tumor samples by western blot analysis.

RESULTS

Both PDX LEY-11 and PDX LEY-16 harboring ATRX gene mutations demonstrated an aggressive behavior in vivo (i.e., control mice were euthanized on average at day 12.5 for PDX LEY-11 and at day 33 for PDX LEY-16). In both tumor models BAY1895344 20 mg/kg dosed with an intermittent oral schedule was able to induce significant growth inhibition compared to vehicle control treatment (p < 0.001 for both LEY-11 and LEY-16) and prolong median overall survival [PDX LEY-11 (12.5 vs. 42 days, p < 0.001) and PDX LEY-16 (33 vs. 60 days, p < 0.001)]. There were not significant changes in weight between treatment and controls. By western blot assays BAY1895344 exposure decreased phosphorylated-ATR and increased expression of apoptotic molecules in LMS PDXs.

CONCLUSIONS

BAY1895344 demonstrates promising in vivo activity against biologically aggressive PDX models of uLMS harboring ATRX mutations, with no significant toxicity. Clinical trials of BAY1895344 in uLMS patients are warranted.

A Benzenesulfonamide-Based Mitochondrial Uncoupler Induces Endoplasmic Reticulum Stress and Immunogenic Cell Death in Epithelial Ovarian Cancer

Epithelial ovarian cancer (EOC) is the leading cause of death from gynecologic malignancies and requires new therapeutic strategies to improve clinical outcomes. EOC metastasizes in the abdominal cavity through dissemination in the peritoneal fluid and ascites, efficiently adapt to the nutrient-deprived microenvironment, and resist current chemotherapeutic agents. Accumulating evidence suggests that mitochondrial oxidative phosphorylation is critical for the adaptation of EOC cells to this otherwise hostile microenvironment. Although chemical mitochondrial uncouplers can impair mitochondrial functions and thereby target multiple, essential pathways for cancer cell proliferation, traditional mitochondria uncouplers often cause toxicity that precludes their clinical application. In this study, we demonstrated that a mitochondrial uncoupler, specifically 2,5-dichloro-N-(4-nitronaphthalen-1-yl)benzenesulfonamide, hereinafter named Y3, was an antineoplastic agent in ovarian cancer models. Y3 treatment activated AMP-activated protein kinase and resulted in the activation of endoplasmic reticulum stress sensors as well as growth inhibition and apoptosis in ovarian cancer cells in vitro Y3 was well tolerated in vivo and effectively suppressed tumor progression in three mouse models of EOC, and Y3 also induced immunogenic cell death of cancer cells that involved the release of damage-associated molecular patterns and the activation of antitumor adaptive immune responses. These findings suggest that mitochondrial uncouplers hold promise in developing new anticancer therapies that delay tumor progression and protect patients with ovarian cancer against relapse.

Effect of exercise on peritoneal microenvironment and progression of ovarian cancer

Ovarian cancer is one of the deadliest gynecological malignancies and lacks treatments that do not significantly impact patient health-related quality of life. Exercise has been associated with reduced cancer risk and improved clinical outcomes; however the underlying molecular mechanisms are unknown. In this study, we utilized a treadmill-running exercise model to investigate the effects of exercise on high-grade serous ovarian carcinoma (HGSOC) progression and chemotherapy outcomes. We found that treadmill-running suppressed peritoneal colonization of tumors in a syngeneic mouse ovarian cancer model. Acute exercise stimulated the production of CCL2 and IL-15 in the peritoneal microenvironment while downregulating CCL22, VEGF, and CCL12. Using a co-culture model, we demonstrated the role of CCL2 in mediating the activity of peritoneal cells to inhibit cancer cell viability. We showed that the activation of M1 macrophages may contribute to the exercise-induced changes in the peritoneal microenvironment. We identified that chronic exercise modulates gene expression of intraperitoneal fat tissues related to lipid formation, thermogenesis, browning, and inflammation, which can contribute to inhibiting the colonization of metastatic ovarian cancer. Treadmill running also lowered blood urea nitrogen levels and reduced incidence of neutropenia and thrombocytopenia during chemotherapy in a mouse model, suggesting the potential beneficial effects of exercise in improving chemotherapy outcomes. Our data provided new insights into the acute and chronic effects of physical activity on ovarian cancer at the molecular and in vivo levels.

Personalized models of heterogeneous 3D epithelial tumor microenvironments: Ovarian cancer as a model

Intractable human diseases such as cancers, are context dependent, unique to both the individual patient and to the specific tumor microenvironment. However, conventional cancer treatments are often nonspecific, targeting global similarities rather than unique drivers. This limits treatment efficacy across heterogeneous patient populations and even at different tumor locations within the same patient. Ultimately, this poor efficacy can lead to adverse clinical outcomes and the development of treatment-resistant relapse. To prevent this and improve outcomes, it is necessary to be selective when choosing a patient's optimal adjuvant treatment. In this review, we posit the use of personalized, tumor-specific models (TSM) as tools to achieve this remarkable feat. First, using ovarian cancer as a model disease, we outline the heterogeneity and complexity of both the cellular and extracellular components in the tumor microenvironment. Then we examine the advantages and disadvantages of contemporary cancer models and the rationale for personalized TSM. We discuss how to generate precision 3D models through careful and detailed analysis of patient biopsies. Finally, we provide clinically relevant applications of these versatile personalized cancer models to highlight their potential impact. These models are ideal for a myriad of fundamental cancer biology and translational studies. Importantly, these approaches can be extended to other carcinomas, facilitating the discovery of new therapeutics that more effectively target the unique aspects of each individual patient's TME. STATEMENT OF SIGNIFICANCE: In this article, we have presented the case for the application of biomaterials in developing personalized models of complex diseases such as cancers. TSM could bring about breakthroughs in the promise of precision medicine. The critical components of the diverse tumor microenvironments, that lead to treatment failures, include cellular- and extracellular matrix- heterogeneity, and biophysical signals to the cells. Therefore, we have described these dynamic components of the tumor microenvironments, and have highlighted how contemporary biomaterials can be utilized to create personalized in vitro models of cancers. We have also described the application of the TSM to predict the dynamic patterns of disease progression, and predict effective therapies that can produce durable responses, limit relapses, and treat any minimal residual disease.

Abstract B49: Effects of exercise on ovarian cancer initiation and progression

Epidemiology studies support a strong association between physical activity and lower risk of cancer. Exercise is a promising nonpharmacologic strategy in preventing cancer and mitigating adverse effects of cancer and anticancer therapies. However, we have not been able to optimize the efficacy of exercise training as an anticancer intervention due to the lack of knowledge regarding the biologic mechanisms of action, the effective doses, and the biomarkers for predicting and monitoring responses of exercise-based intervention. Our objective is to utilize mouse models to determine the effects and underlying mechanisms of exercise on ovarian cancer initiation and progression. C57BL/6 mice ran on a treadmill for 45min daily to mimic human exercise activity. The control groups were placed on treadmill for 45min daily. After a month of this exercise regiment, both groups were injected with cancer cells derived from ovarian tumors of Dicer-/-; Pten-/-; Tp53R172H mice. Tumor progression was monitored through IVIS imaging system. Blood and peritoneal fluid samples were tested for cytokine levels. Tissue samples were collected and gene expression levels were quantified via qPCR. Peritoneal macrophages were isolated after acute exercise and were used in flow cytometry analysis or cocultured with cancer cells. Our model resembled the biologic changes of exercise in human. Eight-week treadmill-running exercise suppressed early tumor formation and tumor spreading. Exercise altered visceral fat tissue gene expression profile, which may inhibit cancer-induced cachexia and metabolic imbalance. In addition, one-hour exercise induced the acute proinflammatory activation of peritoneal macrophages. Coculture of peritoneal macrophages and PBMC (peripheral blood mononuclear cells) or NK (natural killer) cells from the exercise group and cancer cells reduced survival of cancer cells. Chronic and acute exercise can both suppress ovarian cancer tumorigenesis in mouse models. The underlying mechanisms involve enhancing anticancer immune system responses and adjusting metabolic balance. More research is needed to determine the specific mechanisms by which chronic and acute exercise affects ovarian cancer.

Citation Format: Fangfang Bi, Madeline Morrisson, Sarah Cady, Alexandra Cerchia, Kevin Yang, Ivy Ling, Yang Yang-Hartwich. Effects of exercise on ovarian cancer initiation and progression [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr B49.

In vivo modeling of metastatic human high-grade serous ovarian cancer in mice

Metastasis is responsible for 90% of human cancer mortality, yet it remains a challenge to model human cancer metastasis in vivo. Here we describe mouse models of high-grade serous ovarian cancer, also known as high-grade serous carcinoma (HGSC), the most common and deadliest human ovarian cancer type. Mice genetically engineered to harbor Dicer1 and Pten inactivation and mutant p53 robustly replicate the peritoneal metastases of human HGSC with complete penetrance. Arising from the fallopian tube, tumors spread to the ovary and metastasize throughout the pelvic and peritoneal cavities, invariably inducing hemorrhagic ascites. Widespread and abundant peritoneal metastases ultimately cause mouse deaths (100%). Besides the phenotypic and histopathological similarities, mouse HGSCs also display marked chromosomal instability, impaired DNA repair, and chemosensitivity. Faithfully recapitulating the clinical metastases as well as molecular and genomic features of human HGSC, this murine model will be valuable for elucidating the mechanisms underlying the development and progression of metastatic ovarian cancer and also for evaluating potential therapies.

Rarely does an experimental model fully replicate the clinical metastases of a human malignancy. Faithfully representing the clinical metastases of human high-grade serous ovarian cancer with complete penetrance, coupled with histopathological, molecular, and genomic similarities, these mouse models, particularly one harboring mutant p53, will be vital to elucidating the underlying pathogenesis of human ovarian cancer. In-depth understanding of the development and progression of ovarian cancer is crucial to medical advances in the early detection, effective treatment, and prevention of ovarian cancer. Also, these robust mouse models, as well as cell lines established from the mouse primary and metastatic tumors, will serve as useful preclinical tools to evaluate therapeutic target genes and new therapies in ovarian cancer.

An Underlying Mechanism of Dual Wnt Inhibition and AMPK Activation: Mitochondrial Uncouplers Masquerading as Wnt Inhibitors

The importance of upregulated Wnt signaling in colorectal cancers led to efforts to develop inhibitors that target β-catenin in this pathway. We now report that several "Wnt inhibitors" that allegedly target β-catenin actually function as mitochondrial proton uncouplers that independently activate AMPK and concomitantly inhibit Wnt signaling. As expected for a process in which mitochondrial uncoupling diminishes ATP production, a mitochondrial proton uncoupler, FCCP, and a glucose metabolic inhibitor, 2-DG, activated AMPK and inhibited Wnt signaling. Also consistent with these findings, a well-known "Wnt inhibitor", FH535, functioned as a proton uncoupler, and in support of this finding, the N-methylated analog, 2,5-dichloro-N-methyl-N-(2-methyl-4-nitrophenyl)benzenesulfonamide (FH535-M), was inactive as an uncoupler and Wnt inhibitor. Apart from suggesting an opportunity to develop dual Wnt inhibitors and AMPK activators, these findings provide a cautionary tale that claims for Wnt inhibition alone require scrutiny as possible mitochondrial proton uncouplers or inhibitors of the electron transport chain.

Abstract TMIM-084: PKCα INDUCES TWIST1 PHOSPHORYLATION AT SERINE 144 AND PROMOTES EMT IN OVARIAN CANCER CELLS

PURPOSE: Metastasis and carcinomatosis remains a major problem in ovarian cancer. Metastasis requires a process known as Epithelial-to-Mesenchymal Transition (EMT), where by epithelial cancer cells undergo dynamic changes to acquire a mesenchymal and invasive phenotype. Twist1 is a transcription factor with a central role in EMT. We previously showed that in epithelial ovarian cancer (EOC), Twist1 is constitutively ubiquitinated and targeted for proteasomal degradation and inhibition of Twist degradation is associated with mesenchymal phenotype and chemoresistance. Accordingly, identification of mechanisms that promote EMT by inhibiting the active degradation of Twist1 is critical for prevention of carcinomatosis. In this study, we report the identification of PKCα as a central regulator of Twist1. We identified 11 possible PKCα phosphorylation sites on Twist1. We show that Twist1 is a novel substrate of the kinase PKCα and that PKCα-induced Twist1 phosphorylation abrogates Twist1 ubiquitination leading to its stabilization and consequently EMT.

METHODS: The following cell lines were used: (1) ovarian cancer cells lines OVCAR3 and OVCA432; (2) in-house developed cultures of ovarian cancer cells, R182 and R2615; and (3) HEK293T cells. The effect of constitutively active (PKCαCAT), dominant negative (PKCαDN), and wild-type (wt-PKCα) PKCα on levels of Twist1 were determined by transient transfection using qRT-PCT and western blot analysis. Levels of phosphorylated Twist1 were measured in Twist1 immunoprecipitate-complex using anti-phospho-serine/threonine/tyrosine antibody. The phospho-deficient mutant Twist1 S144A was constructed using QuickChange Site-directed Mutagenesis Kit. PKCα was knocked-out in ovarian cancer cells using CRISPR/Cas9. EMT was induced by treatment with 10 ng/ml TGFβ1 and confirmed molecularly (i.e. loss of epithelial markers E-cadherin, Ck18, Claudin 3 and gain of mesenchymal markers Twist1, N-cadherin, and vimentin). Intra-peritoneal tumors were established by injecting 10 million ovarian cancer cells in athymic nude mice.

RESULTS: Transfection with PKCαCAT(active) resulted in a significant increase in Twist1 protein levels compared to PKCαDN(inactive) or empty vector control in EOC and HEK293T cells. This was not a transcriptional effect (no increase in Twist1 mRNA) but due to increase in the levels of phospho-serine/threonine/tyrosine on Twist1. We identified S144 as the putative PKCα phosphorylation site on Twist1 protein. Whereas wt-Twist1 was readily ubiquitinated when transfected in ovarian cancer cells and HEK293T, the phosphomimic S144D Twist1 demonstrated significantly less ubiquitination. Furthermore, we identified TGFβ1 as an activator of the endogenous PKCα-Twist1 axis in ovarian cancer cells. TGFβ1 is able to: (1) activate PKCα; (2) increase Twist1 protein levels; (3) and induce EMT (spheroid formation). Knock-out of PKCα in ovarian cancer cells abrogated TGFβ1-induced EMT in vitro and inhibit carcinomatosis in vivo in athymic nude mice model.

CONCLUSION: We demonstrate for the first time a TGFβ1-PKCα-Twist1 signaling pathway that specifically targets Twist1 protein for phosphorylation and stabilization. This is a non-classical pathway of TGFβ1 induced EMT. Moreover, we identify S144 on Twist1 as novel and direct PKCα-phosphorylation site that can control Twist1 stability. Given the pleiotropic nature of TGFβ1 signaling, the identification of PKCα as a novel target may aid in the development of better therapeutic modalities that can prevent EMT and curtail metastasis formation in ovarian cancer.

Citation Format: Roslyn Tedja, Cai Roberts, Carlos Cardenas, Ayesha B. Alvero, Mary Pitruzzello, Yang Yang-Hartwich, Carlotta Glackin and Gil G. Mor. PKCα INDUCES TWIST1 PHOSPHORYLATION AT SERINE 144 AND PROMOTES EMT IN OVARIAN CANCER CELLS [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr TMIM-084.

Abstract NT-116: TARGETING UNFOLDED PROTEIN RESPONSE FOR OVARIAN CANCER THERAPY

Standard paclitaxel-platinum-based chemotherapies often lead to relapses and chemoresistant diseases. New therapeutic strategies are urgently needed for improving the clinical outcomes of ovarian caner patients. Our goal is to identify dysfunctional cellular pathways that are critical for tumor progression and drug resistance and to design novel therapeutic interventions that affect these altered cellular functions.

The dysregulation of unfolded protein response (UPR) pathway is often found in cancer cells and contributes to cancer cell survival and their resistance to stress caused by chemotherapies, hypoxia, and nutrition deprivation. The objective of our research is to develop new therapeutic agents to target UPR in ovarian cancer cells in order to overcome chemoresistance.

Sulfonamides (SFs) have been used to synthesize antibacterial drugs. We have recently discovered a family of new SFs with anticancer activity. Based on preliminary study, we hypothesize that these new SFs induce apoptosis in ovarian cancer cells through targeting UPR.

Using one of the SFs, namely SF-Y3, we compared its effects on epithelial ovarian cancer (EOC) cell lines and immortalized normal fallopian tube (FT) cell lines by performing luminescent CellTiter assay. Phospho-S6 ribosomal protein (P-S6) staining and Annexin V-FITC/PI staining assays were performed to evaluate the effects of SF-Y3 on cell health. Human transcriptome array (HTA) was used to identify the gene expression changes in SF-Y3-treated EOC cells, which results were confirmed by quantitative real-time PCR (qPCR). Western blot and XBP1 RNA splicing PCR were performed to assess the activation of proteins in UPR pathway. Using 4u8c, an inhibitor of the ER transmembrane protein IRE1, we determined whether inhibiting UPR could rescue cancer cells from the SF-Y3-induced apoptosis. Co-immunoprecipitation (co-PI) was used to determine the effects of SF-Y3 on the ER membrane protein-protein interaction. Moreover, we encapsulated SF-Y3 with nanoparticle to improve its bioavailability for evaluating the in vivo efficacy in EOC mouse model as a single treatment and in combination with platinum-based chemotherapy.

The cell viability data demonstrated that SF-Y3 significantly reduced the viability of EOC cells expressing high levels of Bip1, a key chaperone protein in the endoplasmic. SF-Y3 was less effective in EOC cells with low levels of Bip1 and has no effects on normal FT cells. P-S6 and Annexin V staining assays demonstrated that SF-Y3 inhibited EOC cell proliferation and induced apoptosis. HTA and qPCR data showed that the UPR genes were unregulated by SF-Y3. Western blot and XBP1 RNA splicing PCR results indicated that SF-Y3 activated proteins in the UPR pathway, including ATF6, PERK, eIF2α, XBP1, and CHOP. SF-Y3 interrupted the interaction between Bip1 and three ER membrane-associated sensors, supporting that Bip1 is a possible target of SF-Y3. UPR inhibitor 4u8c partially rescued the apoptosis induced by SF-Y3. These data support that SF-Y3 has anticancer activity in EOC models possibly through inhibiting Bip1 and inducing UPR-induced apoptosis. Further investigation of how SFs interact with Bip1 and UPR pathway in vitro and in vivo may lead to new approaches to overcome drug resistance and a significant therapeutic advance for EOC.

Citation Format: Wonmin Park, Tobias MP. Hartwich, Kay Y. Chong, Chunming Liu, David S. Watt, Dongin Kim, Yang Yang-Hartwich. TARGETING UNFOLDED PROTEIN RESPONSE FOR OVARIAN CANCER THERAPY [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr NT-116.

Abstract TMIM-075: MUTANT P53 PROMOTES THE INITIATION OF HIGH-GRADE SEROUS OVARIAN CARCINOMA FROM FALLOPIAN TUBE TUMOR PRECURSORS THROUGH ENHANCING TYROSINE RECEPTOR KINASE B SIGNALING

Lesions in the fallopian tube (FT) fimbriae are hypothesized to be the precursors of high-grade serous ovarian carcinomas (HGSOC). Immunohistalchemical and sequencing analyses demonstrated that FT lesions shared the same TP53 mutation as the surrounding carcinomas. Analyses of mutations and chromosomal alterations in FT lesions, ovarian cancers, and metastases also revealed that the mutation of TP53 is an early event that might drive tumor initiation. Our study focuses on understanding the molecular mechanisms of mutant p53 promoting tumor initiation from the FT.

Our previous data showed that the FT epithelial cells expressed TrkB. The ligand of TrkB, brain-derived neurotrophic factor (BDNF), is secreted by the ovary, omental adipocytes, peritoneal visceral epithelial cells, and immune cells in the omentum and peritoneum. BDNF suppresses anoikis, the apoptosis induced by lack of proper cell to extra-cellular matrix (ECM) attachment. BDNF/TrkB signaling has been associated to tumor progression. We hypothesize that mutant p53 enhances tyrosine receptor kinase B (TrkB) signaling in FT tumor precursors, which promotes tumor precursors to spread towards the ovary and peritoneal sites.

We used two immortalized human FT cell lines, in which p53 was knocked down by shRNA. Mutant p53 or a control vector were introduced to these cell lines via a lentiviral expression system. The expression level of TrkB protein in FT cells expressing mutant p53 or a control vector was evaluated using Western blot and flow cytometry. CellTiter luminescent cell viability assays were performed to assess the effects of BDNF on the survival of FT cells with or without p53 mutation in 3D culture. Cellmate hydrogel was used as scaffold to support FT cells. And the cells migrated outside the hydrogel were quantified using CellTiter assay. Collagen I-coated beads were used in a 3D cell adhesion model to quantify the ability of FT cells to adhere to ECM and evaluate the effects of BDNF on the cell adhesion. The activation of TrkB downstream proteins was assessed using western blot.

Our data demonstrated that the protein level of TrkB was higher in FT cells expressing mutant p53 (R175H, R248W, and R273H) compared to the control FT cells. Mutant p53 significantly enhanced the survival of FT cells in the serum-free 3D culture condition in the presence of BDNF. BDNF increased the ability of FT cells to migrate outside the hydrogel, and mutant p53 further enhance their migration. Mutant p53 also accelerated the BDNF-mediated attachment of FT cells to collagen I-coated beads. Western blot results showed that the BDNF-activated phosphorylations of TrkB, AKT, ERK, PLC-gamma1 CREB were all increased in the FT cells expressing mutant p53 comparing to the control cells without mutant p53.

These results suggest the role of mutant p53 in promoting the initiation of HGSOC from FT tumor precursors. Through enhancing BDNF/TrkB signaling, mutant p53 can enhance the ability of FT tumor precursors to overcome anoikis and spread towards the ovary, peritoneum, and omentum. A better understanding of the underlying mechanisms will contribute to the development of new treatment and detection markers for HGSOC initiated from the FT.

Citation Format: Min Kang, Kay Y. Chong, Tobias MP. Hartwich, Sarah Cady, Jonah Ncci, Yang Yang-Hartwich. MUTANT P53 PROMOTES THE INITIATION OF HIGH-GRADE SEROUS OVARIAN CARCINOMA FROM FALLOPIAN TUBE TUMOR PRECURSORS THROUGH ENHANCING TYROSINE RECEPTOR KINASE B SIGNALING [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr TMIM-075.

Tumor microenvironment and immunology of ovarian cancer: 12th Biennial Rivkin Center Ovarian Cancer Research Symposium

The 12th Biennial Ovarian Cancer Research Symposium organized by the Rivkin Center for Ovarian Cancer and the American Association for Cancer Research held on September 13-15, 2018 covered cutting edge and relevant research topics in ovarian cancer biology and therapy. Sessions included detection and prevention, genomics and molecular mechanisms, tumor microenvironment and immunology, novel therapeutics, and an education session. In this article we provide an overview of the key findings presented in the tumor microenvironment and immunology session.

Protein kinase Cα-mediated phosphorylation of Twist1 at Ser-144 prevents Twist1 ubiquitination and stabilizes it

Twist1 is a basic helix-loop-helix transcription factor that plays a key role in embryonic development, and its expression is down-regulated in adult cells. However, Twist1 is highly expressed during cancer development, conferring a proliferative, migratory, and invasive phenotype to malignant cells. Twist1 expression can be regulated post-translationally by phosphorylation or ubiquitination events. We report in this study a previously unknown and relevant Twist1 phosphorylation site that controls its stability. To identify candidate phosphorylation sites in Twist1, we first conducted an in silico analysis of the Twist1 protein, which yielded several potential sites. Because most of these sites were predicted to be phosphorylated by protein kinase C (PKC), we overexpressed PKCα in several cell lines and found that it phosphorylates Twist1 on Ser-144. Using a combination of immunoblotting, immunoprecipitation, protein overexpression, and CRISPR/Cas9-mediated PKCα knockout experiments, we observed that PKCα-mediated Twist1 phosphorylation at Ser-144 inhibits Twist1 ubiquitination and consequently stabilizes it. These results provide evidence for a direct association between PKCα and Twist1 and yield critical insights into the PKCα/Twist1 signaling axis that governs cancer aggressiveness.

p53-Pirh2 Complex Promotes Twist1 Degradation and Inhibits EMT

Epithelial-mesenchymal transition (EMT) is a critical process involved in cancer metastasis and chemoresistance. Twist1 is a key EMT-inducing transcription factor, which is upregulated in multiple types of cancers and has been shown to promote tumor cell invasiveness and support tumor progression. Conversely, p53 is a tumor suppressor gene that is frequently mutated in cancers. This study demonstrates the ability of wild-type (WT) p53 to promote the degradation of Twist1 protein. By forming a complex with Twist1 and the E3 ligase Pirh2, WT p53 promotes the ubiquitination and proteasomal degradation of Twist1, thus inhibiting EMT and maintaining the epithelial phenotype. The ability of p53 to induce Twist1 degradation is abrogated when p53 is mutated. Consequently, the loss of p53-induced Twist1 degradation leads to EMT and the acquisition of a more invasive cancer phenotype.Implication: These data provide new insight into the metastatic process at the molecular level and suggest a signaling pathway that can potentially be used to develop new prognostic markers and therapeutic targets to curtail cancer progression.

Abstract A46: Hsp90 regulates Twist1 expression through STAT3 to induce epithelial-mesenchymal transition in ovarian cancer

Background: Metastatic disease is the leading cause of death from ovarian cancer and its underlying mechanisms are poorly understood. Twist1 is a key driver of epithelial-mesenchymal transition (EMT) and metastasis. Understanding the function and regulation of Twist1 is a vital step in the development of effective treatments for metastatic ovarian cancer. Heat shock protein 90 (Hsp90) is a molecular chaperone that modulates multiple signaling networks, and recent studies have highlighted the roles of extracellular Hsp90 in promoting metastasis in cancer. The roles of Hsp90 in regulating intracellular pathways leading to EMT and metastasis remain largely unknown.

Objective: In our study, we tested the hypothesis that Hsp90 promotes EMT in ovarian cancer through the regulation of Twist1 at the transcriptional level.

Methods: We treated A2780 and SKOV3 with a Hsp90-specific inhibitor, 17-allylamino-17 demethoxygeldanamycin (17-AAG). The effects of Hsp90 inhibition on Twist1 mRNA expression and promoter activity were measured using quantitative PCR and luciferase reporter assays, respectively. Proximity ligation assays were performed to visualize the effects of 17-AAG on the interaction between Hsp90 and transcription factors, followed by chromatin immunoprecipitation to measure the binding of transcription factors to the Twist1 promoter.

Results: Treatment with 17-AAG significantly downregulated Twist1 expression at the mRNA level in A2780, SKOV3, and three ovarian cancer patient-derived cell lines. Hsp90 overexpression substantially induced Twist1 promoter activity while treatment with 17-AAG significantly decreased the activity. Western blotting and immunofluorescent staining revealed the presence of 4 transcription factors known to be clients of Hsp90 and regulators of Twist1, which are β-catenin, signal transducer and activator of transcription 3 (STAT3), hypoxia-inducible factor 1-alpha (HIF-1α), and HIF-1β. We identified that Hsp90 interacts with β-catenin, STAT3, and HIF-1α in our cell lines. We observed that 17-AAG treatment dramatically impaired Hsp90-STAT3 interaction and the binding of STAT3 to the Twist1 promoter. Inhibition of Hsp90 was also shown to block interleukin-6 (IL-6) and transforming growth factor beta (TGF-β)-induced EMT.

Conclusion: Taken together, our findings reveal that STAT3 is dependent on Hsp90 to activate Twist1 expression. Hsp90 plays a critical role in enabling STAT3 to bind to the Twist1 promoter and promote Twist1 transcription leading to EMT. We uncovered a previously unrecognized role of Hsp90, which cooperates with STAT3 in the transcriptional regulation of Twist1 in ovarian cancer cells. Inhibiting Hsp90 using small-molecule inhibitors such as 17-AAG may have potential as a therapeutic strategy to prevent EMT and metastasis in ovarian cancer.

Citation Format: Kay Yi Chong, Francesca Garofalo, Oluwagbemisola Madarikan, Nicholas Pitruzzello, Cheng-Hsiu Tsai, Jamie Bingham, Yang Yang-Hartwich. Hsp90 regulates Twist1 expression through STAT3 to induce epithelial-mesenchymal transition in ovarian cancer. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr A46.

Abstract 5220: The role of brain-derived neurotrophic factor in ovarian cancer initiation and progression

Ovarian cancer is one of the most devastating cancers in women. A fundamental step toward improving detection and treatment of this lethal disease is to understand the mechanism of its initiation and progression. In this study we demonstrated the role of brain-derived neurotrophic factor (BDNF) in ovarian cancer initiation and progression, particularly, the high-grade serous ovarian carcinoma (HGSOC). BDNF was discovered in the brain as a growth factor and chemoattractant inducing the migration, survival, and differentiation of neurons. It is also secreted by the ovary into the follicular fluid and by the adipocytes in the omentum and peritoneum. BDNF suppresses anoikis, the apoptosis induced by lack of proper cell to extra-cellular matrix (ECM) attachment. BDNF has been associated with tumor progression in colon, breast, lung, and gastric cancers. In ovarian tumors both BDNF and its receptor tropomyosin receptor kinase B (TrkB) are expressed. Their overexpression is associated with poor survival. Fallopian tube epithelial cells (FTEs) are hypothesized to be the cell of origin of HGSOC. We used 3 immortalized human normal FTE cell lines to demonstrate the effects of BDNF on the survival, mobility, and adhesion of FTEs in vitro. CellTiter luminescent cell viability assays were conducted to evaluate the effects of BDNF on the short-term and long-term survival of FTEs in 3D culture conditions. Caspase-3 activity assays were used to quantify the extent of which BDNF inhibited anoikis in FTEs. Trans-well and 3D bioprinting migration assays were used to determine whether BDNF could promote the mobility of FTEs. The ECM-coated beads were co-cultured with FTEs in a 3D model and their attachment to ECM was quantified in order to evaluate the effects of BDNF on the cell adhesion. The BDNF-activated intracellular pathways were identified using Western blots, RNA microarray, RT-QPCR analyses. Our data demonstrated that TrkB was expressed by the FTEs in human and mouse fallopian tubes. BDNF significantly enhanced the survival of FTE cell lines in the serum-free 3D culture condition. Their enhanced survival was also evidenced by the decreased caspase-3 activity indicating the inhibition of anoikis. BDNF increased the ability of FTEs to migrate in the migrations assays. The BDNF-treated FTEs attached to the ECM-coated beads faster than the untreated cells. Western blots showed that BDNF activated the phosphorylation of TrkB, AKT, ERK, PLC-gamma1, and CREB. RNA microarray and QPCR data suggest that epithelial-mesenchymal transition (EMT), anti-oxidative stress, and ECM-related pathways were activated by BDNF leading to the enhanced survival, migration, and cell adhesion. These results revealed the potential role of BDNF to promote ovarian cancer initiation. Understanding this molecular pathway will lead to the development of more specific markers for early detection and better prevention and treatment strategies.

Citation Format: Min Kang, Kay Y. Chong, Tobias M. Hartwich, Oluwagbemisola O. Madarikan, Jonah Nucci, Sarah L. Cady, Yang Yang-Hartwich. The role of brain-derived neurotrophic factor in ovarian cancer initiation and progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5220.

Abstract 1969: PKCα-induced Twist1 phosphorylation is a novel regulator of Twist1 stabilization

Background:

Epithelial - mesenchymal transition (EMT) is a pre-requisite for cancer metastasis. Twist-1 is a transcription factor with a central role in the process of EMT and therefore metastasis formation. Using ovarian cancer models, our group has previously shown that although the stationary epithelial phenotype express Twist1 mRNA, this phenotype is enforced by mechanisms that constitutively ubiquitinates and degrades the Twist1 protein. The objective of this study is to identify molecular mechanisms that promote Twist1 protein stabilization and therefore confer a mesenchymal and mobile phenotype.

Materials and methods:

Novel phosphorylation sites on Twist1 protein, which are adjacent to ubiquitination sites, were identified using NetPhosK and Ubpred. Further analysis demonstrates that most of these sites contain the consensus sequence for PKCα. Constitutively active PKCα (PKCαcat) was ectopically expressed in HEK293T cells and patient-derived epithelial ovarian cancer cell lines. Protein expression and phosphorylation status were determined using western blot analysis using either whole cell lysates or cellular fractions. Protein-protein interaction was determined by immunoprecipiation. The specific Twist1 domain required for PKCα interaction was determined by co-transfection with Twist1 deletion mutants.

Results:

Ectopic expression of PKCαcat in HEK293T cells and ovarian cancer cells resulted in increased levels of Twist1 protein compared to empty vector control. In ovarian cancer cells, PKCcat-induced upregulation of Twist1 protein is not associated with an increase in Twist1 mRNA but instead is associated with Twist1 phosphorylation, decreased ubiquitination, and enhanced stabilization. We identify the twist box (WR) domain of Twist1 as a pre-requisite for PKCα binding and PKCαcat-induced Twist1 stabilization. Moreover, we identify TGFβ1 as a potent activator of endogenous PKCα in epithelial ovarian cancer cells. TGFβ1 (1 ng/ml) is able to: promote the activation and membranal translocation of PKCα; increase Twist1 protein levels; and induce spheroid formation and EMT in epithelial ovarian cancer cells. Interestingly, TGFβ1 had no effect on Twist1 mRNA suggesting that this mechanism is independent of the classical TGFβ-Smad pathway.

Conclusions:

We demonstrate for the first time a novel TGFβ-PKCα signaling pathway that specifically targets Twist1 protein for phosphorylation and stabilization resulting in EMT. This mechanism is independent of the classical TGFβ-Smad pathway that controls EMT via transcriptional regulation. Since TGFβ is a pleiotropic cytokine that can affect multiple cell types, the identification of PKCα as a novel target in ovarian cancer cells may aid in the development of better therapeutic modalities that can prevent EMT and curtail metastasis formation.

Citation Format: Roslyn Tedja, Ayesha B. Alvero, Carlos Cardenas, Mary Pitruzzello, Gang Yin, Yang Yang-Hartwich, Cai Roberts, Carlotta Glackin, Gil G. Mor. PKCα-induced Twist1 phosphorylation is a novel regulator of Twist1 stabilization [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1969. doi:10.1158/1538-7445.AM2017-1969

Abstract AP16: THE CRITICAL ROLE OF P53–TWIST1 AXIS IN OVARIAN CANCER METASTASIS

BACKGROUND: Tumor metastasis is the primary cause of mortality in patients with advanced ovarian cancer. The molecular mechanism underlying metastasis is still not clear. Twist1 is a transcriptional factor that promotes epithelial-mesenchymal transition (EMT) and enhances the migration and tumor-initiation of ovarian cancer cells. It also has been associated with cancer stem cells and chemoresistance. The purpose of our study is to better understand the regulation of Twist1 and to identify molecular pathways that can be targeted in order to control metastatic diseases. Previous studies have shown an interaction between Twist1 and the tumor suppressor p53. We hypothesize that through their interaction, p53 promotes the proteasomedependent degradation of Twist1 and consequently inhibits EMT in epithelial ovarian cancer cells. p53 mutations, which are common in advanced ovarian cancer patients, may impair p53's ability to inhibit Twist1, leading to enhanced EMT and metastasis.

METHOD: In ubiquitin assay p53, Twist1, Pirh2, and Ubiquitin were overexpressed in HEK293T or epithelial ovarian cancer (EOC) cells by transfection. Coimmunoprecipitation and western blotting were used to detect protein interaction and ubiquitination. Protein lysate were prepared from 25 tumor samples (12 ovarian tumor, 10 ovarian tumor metastases, and 2 fallopian tube tumors) for western blotting. Plasmid constructs containing different Twist1 mutants were created to select the degradation resistant mutation. ΔC-Twist1 (C-terminal deletion) was used in in vivo study.

RESULT: 1) In EOC cells, proteasome-dependent degradation suppressed Twist1 protein. During in vitro EMT, Twist1 and p53 protein levels negatively correlated. In ovarian cancer cells, wild type p53 overexpression reduced Twist1 protein level and enhances the ubiquitination of Twist1 without affecting Twist1 mRNA level. Mutant p53 (R175H, R148W, and R273H) failed to enhance Twist1 degradation. E3 ligase, Pirh2, formed complex with p53 and Twist1 to induce Twist1 degradation. 2) ΔC-Twist1 was resistant to p53-regulated degradation. In xenograft mouse model, EOC cells overexpressing ΔC-Twist1 could form more aggressive tumors with increased numbers of metastatic lesions than wild type Twist1 group. 3) In 25 ovarian tumor samples, 11 tumors with high levels of Twist1 had either a p53 mutation or very low levels of wild type p53. Nine samples with high levels of wild type p53 all showed low or no Twist1 expression.

CONCLUSION: Our data revealed a mechanism by which Twist1 is regulated through p53-promoted proteasome-dependent degradation. p53 facilitates the formation of a Twist1-p53-Pirh2 complex and the Pirh2-mediated Twist1 degradation. Our data also demonstrated that three hotspot p53 mutants failed to promote Twist1 degradation, leading to the stabilization of Twist1 and the induction of EMT. This mechanism may be critical for controlling metastasis of ovarian tumors. The newly discovered role of Pirh2 as an E3 ligase in mediating Twist1 ubiquitination and degradation has expanded the known spectrum of Pirh2 function. In addition to providing new insights into metastatic process at the molecular and cellular levels, our data suggest a signaling pathway that can potentially be used to develop new prognostic markers and therapeutic targets to inhibit Twist1 and control ovarian cancer metastasis.

Citation Format: Yang Yang-Hartwich, Roslyn Tedja, Jamie Bingham, Marta Gurrea Soteras, Ayesha B. Alvero, Gil Mor. THE CRITICAL ROLE OF P53–TWIST1 AXIS IN OVARIAN CANCER METASTASIS [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr AP16.

Abstract 4201: Targeting tumor-associated neovasculature for delivery of optical enhancers detects ovarian cancer micrometastasis

Background: Patients with epithelial ovarian cancer have the best overall survival when maximal surgical effort is accomplished. While identification and removal of large metastases do not pose a challenge, micrometastases are impossible to distinguish intra-operatively and contribute to the high mortality. Our objective is to develop specific tumor-targeting optical enhancers that can aid surgeons in the performance of microscopic tumor debulking with the goal of minimizing microscopic residual disease. We hypothesize that we can utilize overexpressed αVβ3 integrins in the tumor-associated neovasculature. Specific targeting is achieved by encapsulating fluorescent probes in FDA-approved PLGA-based nanoparticle (NP) coated with the peptide sequence arginine-glycine-aspartate (RGD), which binds with high affinity to these integrins.

Materials and methods:

Ovarian cancer xenograft is established intra- peritoneally (i.p.) in nude mice using cancer cells that stably express mCherry fluorescent protein. The following formulations were tested: soluble deep infrared dye (DIR), DIR encapsulated in naked NP (DIR-NP), and DIR encapsulated in RGD-coated NP (DIR-RGD-NP). Formulations were delivered i.p. and colocalization of fluorescent signals were determined ex vivo. Staining of micrometastasis was visualized using fluorescent dissection microscope.

Results: The best colocalization was observed in mice administered DIR-RGD-NP. We observed 75% colocalization in this group compared to 26% and 0% in DIR-NP and DIR groups, respectively. Ex vivo analysis of DIR intensity in tumors less than 2 mm showed mean fluorescent intensity (MFI) of 1209 in DIR-RGD-NP group versus 155 MFI DIR-NP group. Based on DIR staining, we can locate 81% of mCherry+ micrometastasis in animals administered DIR-RGD-NP. In these animals, tumors less than 1 mm were detected due to a halo of DIR staining around each micrometastatic lesion. In these foci, DIR signal was observed to stain the vasculature surrounding the small tumor implants especially those in the mesentery and diaphragm. In contrast, we were able to detect only 18% of the mCherry+ micrometastasis in animals administered DIR-NP.

Conclusion:

We demonstrate that we can utilize the specific phenotype of tumor-associated neovasculature to target optical enhancers to locate and delineate micrometastasis. RGD-coated nanoparticles are able to carry probes to the tumor microenvironment leading to optimal staining of micrometastasis. Our results highlight the use of this nanotechnology platform in microscopic surgical debulking to assure maximal surgical effort, minimize residual disease, and improve patient survival.

Citation Format: Ayesha B. Alvero, Eydis Lima, Dongin Kim, Sean Orton, Natalia Sumi, Mary Pitruzzello, Yang Yang-Hartwich, Dan-Arin Silasi, Tarek Fahmy, Gil Mor. Targeting tumor-associated neovasculature for delivery of optical enhancers detects ovarian cancer micrometastasis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4201.

Abstract LB-352: p53-promoted Twist1 degradation inhibits EMT in ovarian cancer cells

Background: Tumor metastasis is the primary cause of mortality in patients with advanced ovarian cancer. The molecular mechanism behind ovarian cancer metastasis is still not clear. Twist1 is associated with the increased ability of migration and tumor-initiation of ovarian cancer cells; therefore, understanding the regulation of Twist is critical for the prevention of metastatic disease. Previous studies have shown an interaction between Twist1 and the tumor suppressor p53. We propose that p53 functions as a normal inhibitor of Twist1. We hypothesize that through their interaction, p53 promotes the proteasome-dependent degradation of Twist1 and consequently inhibits epithelial-mesenchymal transition (EMT) in epithelial ovarian cancer cells. p53 mutations, which are common in advanced ovarian cancer patients, may impair p53's ability to inhibit Twist1, leading to enhanced EMT and metastasis.

Method: p53, Twist1, Pirh2, and Ubiquitin were overexpressed in HEK293T or epithelial ovarian cancer (EOC) cells by transfection. Co-immunoprecipitation and western blotting were used to detect protein interaction and ubiquitination. Protein lysate were prepared from 25 tumor samples (12 ovarian tumor, 10 ovarian tumor metastases, and 2 fallopian tube tumors) for western blotting.

Result: Wild type p53 overexpression reduces Twist1 protein level and enhances the ubiquitination of Twist1 without affecting Twist1 mRNA level. Mutant p53 (R175H, R148W, and R273H) failed to regulate Twist1 degradation. E3 ligase, Pirh2, forms complex with p53 and Twist1 to induce Twist1 degradation. In EOC cells, Twist1 is suppressed by proteasome-dependent degradation. During in vitro EMT, Twist1 and p53 protein levels negatively correlated. In 25 ovarian tumor samples, 11 tumors with high levels of Twist1 had either a p53 mutation or very low levels of wild type p53. The 9 samples with high levels of wild type p53 all showed low or no Twist1 expression.

Conclusion: Our data revealed a mechanism by which a crucial EMT inducer, Twist1, is regulated by wild type p53 through enhancing its proteasome-dependent degradation. p53 promotes the formation of a Twist1-p53-Pirh2 complex and facilitates Pirh2-mediated Twist1 degradation. Our data also demonstrated that three hotspot p53 mutants failed to promote Twist1 degradation, leading to the stabilization of Twist1 and the induction of EMT. This mechanism may be critical for controlling metastasis of ovarian tumors. The newly discovered role of Pirh2 as an E3 ligase in mediating Twist1 ubiquitination and degradation has expanded the known spectrum of Pirh2 function. In addition to providing new insights into metastatic process at the molecular and cellular levels, our data suggest a signaling pathway that can potentially be used to develop new prognostic markers and therapeutic targets to inhibit Twist1 and control ovarian cancer metastasis.

Citation Format: Yang Yang-Hartwich, Roslyn Tedja, Jamie Bingham, Marta Gurrea Soteras, Ayesha B. Alvero, Gil Mor. p53-promoted Twist1 degradation inhibits EMT in ovarian cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-352.

TRX-E-002-1 Induces c-Jun-Dependent Apoptosis in Ovarian Cancer Stem Cells and Prevents Recurrence In Vivo

Chemoresistance is a major hurdle in the management of patients with epithelial ovarian cancer and is responsible for its high mortality. Studies have shown that chemoresistance is due to the presence of a subgroup of cancer cells with stemness properties and a high capacity for tumor repair. We have developed a library of super-benzopyran analogues to generate potent compounds that can induce cell death in chemoresistant cancer stem cells. TRX-E-002-1 is identified as the most potent analogue and can induce cell death in all chemoresistant CD44(+)/MyD88(+) ovarian cancer stem cells tested (IC50 = 50 nmol/L). TRX-E-002-1 is also potent against spheroid cultures formed from cancer stem cells, chemosensitive CD44(-)/MyD88(-) ovarian cancer cells, and heterogeneous cultures of ovarian cancer cells. Cell death was associated with the phosphorylation and increased levels of c-Jun and induction of caspases. In vivo, TRX-E-002-1 given as daily intraperitoneal monotherapy at 100 mg/kg significantly decreased intraperitoneal tumor burden compared with vehicle control. When given in combination with cisplatin, animals receiving the combination of cisplatin and TRX-E-002-1 showed decreased tumor burden compared with each monotherapy. Finally, TRX-E-002-1 given as maintenance treatment after paclitaxel significantly delayed disease recurrence. Our results suggest that TRX-E-002-1 may fill the current need for better therapeutic options in the control and management of recurrent ovarian cancer and may help improve patient survival. Mol Cancer Ther; 15(6); 1279-90. ©2016 AACR.

Abstract A62: TRX-1 targets chemoresistant tumor-initiating cells and prolongs survival in a recurrent ovarian cancer animal model

Background: Ovarian cancer is the leading cause of mortality from gynecologic cancers due to the high incidence of chemoresistance and disease recurrence. Disease recurrence is thought to occur due to the presence of residual disease following first-line standard of care (i.e. optimal debulking and chemotherapy). Residual disease post chemotherapy is composed of a unique population of chemoresistant cancer cells with stemness properties and a high capacity for tumor repair. Currently, there are no available options that can target these cells. The objective of this study was to develop a new therapeutic modality that will target chemoresistant ovarian cancer stem cells (OCSC) and consequently prevent recurrence and improve survival. To achieve this objective we developed a library of super-benzopyran (SBP) analogues and identified TRX-1 as the most potent analogue able to induce OCSC cell death in a short period of time. Moreover, in contrast to Cisplatin and Paclitaxel, TRX-1 is able to induce a persistent growth inhibitory effect both in vitro and in vivo thus improving overall survival in a mouse model of recurrent ovarian cancer.

Materials and methods: A panel of SBP analogues were generated and activity was determined by testing against pure clones of CD44+/MyD88+ OCSC. In vitro efficacy was assessed using the IncucyteTM kinetic imaging platform complemented by CelltoxTM dye labeling. In vivo efficacy was tested using an intra-peritoneal (i.p.) a mouse model of recurrent ovarian cancer1.

Results: TRX-1 was the most potent analogue identified and is able to induce cell death in all OCSC clones tested (IC50 of 136 nM). We observed that 2h in vitro exposure to 2μM TRX-1 was sufficient to induce a sustained growth inhibitory effect in OCSC, hence the cells were not able to recover growth potential even after removal of the drug. In contrast, OCSC exposed for up to 24h with the same dose of Cisplatin or Paclitaxel were able to recover. In vivo, animals bearing residual tumors after Paclitaxel treatment demonstrated tumor progression when further maintained with vehicle or Paclitaxel indicating Paclitaxel resistance. In contrast, maintenance with TRX-1 was able to effectively decrease tumor burden (p = 0.02) and prevent recurrence. In addition, combination treatment with TRX-1 and Cisplatin was able to significantly improve survival (p&lt;0.001) compared to Cisplatin alone.

Conclusion: We describe the in vitro and in vivo anti-tumoral effect of a novel compound, TRX-1, which exhibits significant efficacy against chemoresistant OCSC and is able to prevent recurrence in a chemoresistant in vivo model. Recurrence characterized by chemoresistance is the main cause of mortality in ovarian cancer patients. Previous studies from our laboratory have shown that conventional chemotherapy is not effective against OCSC and cannot prevent recurrence. Our finding that TRX-1, by targeting OCSC can prevent recurrence in vivo as maintenance therapy or in combination with chemotherapy provides a new opportunity for developing new therapeutic strategies that can improve survival in ovarian cancer patients.

Citation Format: Ayesha Alvero, Eydis Lima, Mary Pitruzzello, Yang Yang-Hartwich, David Brown, Andrew Heaton, Gil Mor. TRX-1 targets chemoresistant tumor-initiating cells and prolongs survival in a recurrent ovarian cancer animal model. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr A62.

Abstract AS16: Ovulation and extraovarian origin of ovarian cancer

High grade serous ovarian carcinoma (HGSOC) accounts for 70% of the approximately 26,000 diagnosed epithelial ovarian cancer cases every year. The majority of HGSOC patients are diagnosed at advanced stage when tumors have metastasized. The efforts of improving the prognosis and survival rate are hindered by our limited knowledge about the origin of ovarian cancer. Recent studies have revealed that the fallopian tube epithelial cells are the origin of HGSOC. Pre-malignant precursor lesions have been found in the fallopian tubes. Studies of genetically engineered mouse models supported the fallopian tube origin theory. However, one of the main questions that arise is how the malignant fallopian tube cells form tumors inside the ovary. In our study, we sought to identify the key factors and related pathways that can promote the extraovarian malignant cells to migrate toward the ovary and establish ovarian tumors.

In the ovary, the rupture and repair process during menstrual cycles repeatedly creates a local inflammatory microenvironment, in which chemokines, cytokines, and growth factors are produced. During ovulation, the ovary is a plausible source of chemotactic factors that can attract the movement of extraovarian malignant cells towards the ovary. Inside the ovary, the post-ovulatory inflammatory and pro-repair environment can provide tumorigenic factors that support malignant transformation or maintain malignant cell survival.

We utilized in vitro, ex vivo, xenograft, and allograft mouse models to recreate the process of extraovarian malignant cells migrating to the ovary to form tumors. Using in vitro migration assay, we demonstrated that SDF-1 secreated by ovarian granulosa cell attracts the migration of ovarian cancer cells. In the ex vivo organ culture model, we cocultured fluorescence-labeled ovarian cancer cells with mouse ovaries and observed the adhesion of cancer cells to the ovulatory wound areas. We further proved that ovarian stromal cell extracellular matrix provides better support to the adhesion of cancer cells than the ovarian surface epithelial cells. We also demonstrate that in mice the intra-vaginally injected extraovarian malignant cells can travel through the reproductive tract to the ovary and form ovarian tumors. With the superovulation model in mice, we showed that ovulation promoted the migration and adhesion of malignant cells to the ovary by disrupting the ovarian surface epithelium and releasing chemokines/cytokines. The exposure of collagen IV-enriched ovarian stroma at ovulatory wounds provides scaffold supporting the adhesion of malignant cells. These ovulation-associated factors contribute to ovarian tumor formation.

We conclude that during ovulation the ovary-secreted chemotactic factors can attract the movement of malignant cells towards the ovary. The unique microenvironment in the ovary supports the survival of cancer cells and triggers the progression of tumors. Our findings revealed the molecular mechanism behind the initiation of ovarian cancer and the association between increased ovulation and the risk of ovarian cancer in the epidemiological studies.

Citation Format: Yang Yang-Hartwich. Ovulation and extraovarian origin of ovarian cancer [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 AS16.

Abstract LB-014: Targeting p53 aggregation in ovarian cancer chemoresistant cells

Background: About half of patients diagnosed with ovarian cancer develop chemoresistance and succumb to the disease. The underlying mechanisms that lead to the development of chemoresistance are poorly understood. We previously demonstrated that p53 protein aggregation inhibited p53 pro-apoptotic activities consequently leading to platinum resistance in ovarian cancer cells with cancer stem cell properties. Since heat shock protein 90 (HSP90), a molecular chaperone, can sustain the accumulation of protein aggregates, the purpose of this study is to determine if HSP90 inhibitors can inhibit the accumulation of p53 aggregates, reactivate p53 pro-apoptotic function, and sensitize ovarian cancer stem cells (OCSCs) to carboplatin.

Method: Chemoresistant CD44+/MyD88+ OCSCs were treated with the HSP90 inhibitor, 17-AAG, carboplatin, or the combination of 17-AAG and carboplatin. Cell viability was monitored by IncuCyte ZOOM live-cell imaging system. Caspase activation was determined by Caspase-Glo assay. p53 aggregation was detected by non-denaturing gel and western blot. The interaction between p53 and HSP90 proteins was determined by co-immunoprecipitation (co-IP). Chromatin immunoprecipitation (CHIP) of p53 and RT-QPCR of p53 targets (PUMA, BAX, et al.) were performed to demonstrate p53 transcriptional activation.

Result: OCSCs were resistant to single treatment with Carboplatin. In line with results from our previous studies, carboplatin neither decreased cell viability nor induced caspase activation in these cells. Interestingly, carboplatin enhanced the levels of aggregated p53 and hence failed to upregulate the expression of p53-related pro-apoptotic genes. Co-IP results demonstrated that 17-AAG blocked the interaction between p53 and HSP90. More importantly, 17-AAG was able to sensitize OCSCs to carboplatin. The combination therapy effectively induced the transcriptional activity of p53, upregulated pro-apoptotic genes, and stimulated caspase activity and cell death in the carboplatin-resistant OCSCs.

Conclusion: The HSP90 inhibitor, 17-AAG can inhibit the formation of p53 aggregates by blocking the interaction between p53 and HSP90. By releasing p53 from the aggregates, 17-AAG reactivates the ability of p53 to bind to DNA and to upregulate the expression of target genes, which leads to the apoptosis of OCSCs. 17-AAG sensitizes chemoresistant OCSCs to carboplatin treatment. Using HSP90 inhibitors to target p53 aggregation and sensitize chemoresistant cells with protein aggregates may significantly improve the response of ovarian cancer to conventional chemotherapies.

Citation Format: Yang Yang-Hartwich, Carlos Cardenas, Mary Pitruzzello, Eydis Lima, Ayesha B. Alvero, Gil Mor. Targeting p53 aggregation in ovarian cancer chemoresistant cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-014. doi:10.1158/1538-7445.AM2015-LB-014

Abstract 1519: Cantrixil targets ovarian cancer stem cells and prevents recurrence in a cisplatin-resistant animal model

Background: Chemoresistance is a major hurdle in the management of patients with epithelial ovarian cancer (EOC) and is associated with high mortality. Growing evidence suggests that chemoresistance is due to the presence of a subgroup of cancer cells with stemness properties and a high capacity for tumor repair. Current modalities are not able to target these cancer stem cells (CSC), thus there is a need to develop novel treatment approaches. We developed a library of super-benzopyran (SBP) analogues to generate potent compounds that can induce cell death in the chemoresistant CSC. We report the anti-tumoral in vivo efficacy of Cantrixil in a cisplatin-resistant animal model as monotherapy, and in combination with cisplatin. Furthermore, Cantrixil as salvage therapy prevents recurrence following paclitaxel treatment and significantly prolongs survival.

Materials and methods: A panel of SPB analogues were generated and activity was determined by testing against pure clones of CD44+/MyD88+ EOC stem cells. In vitro efficacy was screened using the IncucyteTM kinetic imaging platform complemented by CelltoxTM dye labelling. In vivo efficacy and toxicology was tested using an intra-peritoneal (i.p.) cisplatin-resistant ovarian cancer xenograft model 1.

Results: Cantrixil was the most potent analogue, inducing cell death in all EOC stem cell clones tested (IC50 of 136 nM). Cell death was associated with the activation of the JNK pathway, loss of mitochondrial membrane potential, and caspase activation. In vivo, Cantrixil, as mono-therapy, significantly decreased i.p. tumor burden compared to vehicle control (p = 0.0001 n = 10) while cisplatin had no effect(p = 0.8). Furthermore, the combination of Cantrixil and cisplatin significantly decreases tumor burden compared to ciplatin alone or control (p = 0.002 and p = 0.004) In addition, using an in vivo recurrent EOC model, maintenance treatment with Cantrixil given post a Paclitaxel regimen prevented recurrent disease and significantly decreased metastatic tumor burden compared to maintenance with Paclitaxel (p = 0.002).

Conclusion: We described the in vivo anti-tumoral effect of a novel compound, Cantrixil, which exhibits significant efficacy against chemoresistant EOC stem cells and is able to prevent recurrence in a cisplatin-resistant in vivo model. Recurrence characterized by chemoresistance is the main cause of mortality in ovarian cancer patients. Previous studies from our laboratory have shown that conventional chemotherapy is not effective on EOC stem cells and can not prevent recurrence. Our finding that Cantrixil, by targeting CSCs, can prevent recurrence in vivo as maintenance therapy or in combination with chemotherapy, provides a new opportunity for developing a new therapeutic strategy that can help ovarian cancer patients.

1. Craveiro V, et al. Cancer Medicine. 2013;2: 751-762.

Citation Format: Gil G. Mor, Eydis Lima, Natalia Sumi, Mary Pitruzzello, Yang Yang-Hartwich, David Brown, Andrew Heaton, Ayesha B. Alvero. Cantrixil targets ovarian cancer stem cells and prevents recurrence in a cisplatin-resistant animal model. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1519. doi:10.1158/1538-7445.AM2015-1519

Detection of p53 protein transcriptional activity by chromatin immunoprecipitation

p53 is a key transcriptional mediator that controls the expression of hundreds of target genes necessary to maintain cellular homeostasis and genome integrity. An important cellular function that is dependent on p53 transcriptional activity is apoptosis or programmed cell death. Indeed, inhibition of p53 transcriptional activity is often observed in cancers as a result of mutations within its DNA-binding domain. In this chapter, we describe the use of chromatin immunoprecipitation and real-time quantitative polymerase chain reaction to detect p53 transcriptional activity in cancer cells and tumor tissues. This technique enables the determination of the ability of p53 to bind to the promoter region of apoptotic genes and to evaluate the transcription-dependent activity of p53-induced apoptosis.

Detection of p53 protein aggregation in cancer cell lines and tumor samples

The p53 protein plays a central role in regulating apoptosis. The loss of functional p53 is common in many cancers. In cancer cells, the dysfunctional p53 protein often maintains a misfolded, inactive conformation due to genetic mutations or posttranslational deregulation. The misfolded p53 protein can aggregate and form amyloid-like oligomers and fibrils, which abrogate the pro-apoptotic functions of p53. Therefore, the aggregation of p53 may be a crucial factor in carcinogenesis, tumor progression, and the response of cancer cells to apoptotic signals. In this chapter, we provide details on various methods for detecting p53 aggregation in cancer cell lines and tumor samples.

Murine model for non-invasive imaging to detect and monitor ovarian cancer recurrence

Epithelial ovarian cancer is the most lethal gynecologic malignancy in the United States. Although patients initially respond to the current standard of care consisting of surgical debulking and combination chemotherapy consisting of platinum and taxane compounds, almost 90% of patients recur within a few years. In these patients the development of chemoresistant disease limits the efficacy of currently available chemotherapy agents and therefore contributes to the high mortality. To discover novel therapy options that can target recurrent disease, appropriate animal models that closely mimic the clinical profile of patients with recurrent ovarian cancer are required. The challenge in monitoring intra-peritoneal (i.p.) disease limits the use of i.p. models and thus most xenografts are established subcutaneously. We have developed a sensitive optical imaging platform that allows the detection and anatomical location of i.p. tumor mass. The platform includes the use of optical reporters that extend from the visible light range to near infrared, which in combination with 2-dimensional X-ray co-registration can provide anatomical location of molecular signals. Detection is significantly improved by the use of a rotation system that drives the animal to multiple angular positions for 360 degree imaging, allowing the identification of tumors that are not visible in single orientation. This platform provides a unique model to non-invasively monitor tumor growth and evaluate the efficacy of new therapies for the prevention or treatment of recurrent ovarian cancer.

Abstract 1974: Ovulatory wound: the site of origin for ovarian serous carcinoma

Background: New clinical and molecular studies suggest that HGSOC originates from the neighboring fallopian tubes, rather than the surface epithelial layer of the ovary. However, very little is known about the process of tubal malignant cells migrating and implanting into ovary. Our research focuses on understanding how the extraovarian malignant cells implant into the ovary and how ovulation affects the process of their migration and implantation.

Method: Tumor initiating cells (TICs) isolated from human HGSOC were labeled by red fluorescent protein (RFP)-expressing lentivirus and subcutaneously or intrauterine injected to immunocompromised mice. Hormones (PMS and HCG) were interperitoneally injected to induce superovulation in mice. In the in vitro models, TICs were cultured with the granulosa cell conditional medium and the extra cellular matrix (ECM) extracted from ovarian stroma cells to evaluate their effects on the migration and attachment of TICs

Result: Superovulation increased the ovarian tumor-forming rate from 38% (15/39 in control group) to 100% (24/24 in supervolation group). The increased frequency of ovulation enhances the formation of ovarian tumors in mouse models. In the intrauterine injection model, we were able to trace the migration of TICs towards ovaries and capture the early implantation of TICs inside ovaries in 5-10 days after the injection. We detected stage I ovarian tumors in mice. The tumors are encapsulated in the ovary and covered by the intact surface epithelial layer. These tumor cells closely interacted with the stroma of ovary, particularly the structure of corpus luteum. The granulosa cells secreted stromal cell-derived factor 1 (SDF-1, also known as CXCL12). SDF-1 attracts TICs that express CXCR4 (the receptor of SDF-1) to ovulatory wounds. Upon ovulation the ovulatory wounds expose the stroma of ovary, which provides a collagen enriched ECM for TICs to attach.

Conclusion: The unique ovulatory wound microenvironment attracts the malignant cells to migrate towards the ovary and creates access for the malignant cells to implant in the collagen-enriched ECM in the stroma of ovary. The new mechanisms revealed by our data may explain why increased ovulation is associated with epithelial ovarian cancer. Our findings support the “extra-ovarian origin” theory and will help us better understand the initiation and progression of HGSOC.

Citation Format: Yang Yang-Hartwich, Marta Gurrea, Natalia Sumi, Jennie Holmberg, Vinicius Craveiro, Ayesha Alvero, Gil Mor. Ovulatory wound: the site of origin for ovarian serous carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1974. doi:10.1158/1538-7445.AM2014-1974

Ovulation and extra-ovarian origin of ovarian cancer

The mortality rate of ovarian cancer remains high due to late diagnosis and recurrence. A fundamental step toward improving detection and treatment of this lethal disease is to understand its origin. A growing number of studies have revealed that ovarian cancer can develop from multiple extra-ovarian origins, including fallopian tube, gastrointestinal tract, cervix and endometriosis. However, the mechanism leading to their ovarian localization is not understood. We utilized in vitro, ex vivo, and in vivo models to recapitulate the process of extra-ovarian malignant cells migrating to the ovaries and forming tumors. We provided experimental evidence to support that ovulation, by disrupting the ovarian surface epithelium and releasing chemokines/cytokines, promotes the migration and adhesion of malignant cells to the ovary. We identified the granulosa cell-secreted SDF-1 as a main chemoattractant that recruits malignant cells towards the ovary. Our findings revealed a potential molecular mechanism of how the extra-ovarian cells can be attracted by the ovary, migrate to and form tumors in the ovary. Our data also supports the association between increased ovulation and the risk of ovarian cancer. Understanding this association will lead us to the development of more specific markers for early detection and better prevention strategies.

Phenotypic modifications in ovarian cancer stem cells following Paclitaxel treatment

Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy. Despite initial responsiveness, 80% of EOC patients recur and present with chemoresistant and a more aggressive disease. This suggests an underlying biology that results in a modified recurrent disease, which is distinct from the primary tumor. Unfortunately, the management of recurrent EOC is similar to primary disease and does not parallel the molecular changes that may have occurred during the process of rebuilding the tumor. We describe the characterization of unique in vitro and in vivo ovarian cancer models to study the process of recurrence. The in vitro model consists of GFP+/CD44+/MyD88+ EOC stem cells and mCherry+/CD44-/MyD88- EOC cells. The in vivo model consists of mCherry+/CD44+/MyD88+ EOC cells injected intraperitoneally. Animals received four doses of Paclitaxel and response to treatment was monitored by in vivo imaging. Phenotype of primary and recurrent disease was characterized by quantitative polymerase chain reaction (qPCR) and Western blot analysis. Using the in vivo and in vitro models, we confirmed that chemotherapy enriched for CD44+/MyD88+ EOC stem cells. However, we observed that the surviving CD44+/MyD88+ EOC stem cells acquire a more aggressive phenotype characterized by chemoresistance and migratory potential. Our results highlight the mechanisms that may explain the phenotypic heterogeneity of recurrent EOC and emphasize the significant plasticity of ovarian cancer stem cells. The significance of our findings is the possibility of developing new venues to target the surviving CD44+/MyD88+ EOC stem cells as part of maintenance therapy and therefore preventing recurrence and metastasis, which are the main causes of mortality in patients with ovarian cancer.

Abstract LB-286: ME-344 delays tumor kinetics in an ovarian cancer in vivo recurrence model

Background: Epithelial ovarian cancer (EOC) is the most lethal of all gynecologic malignancies. Despite initial responsiveness to first-line standard of care, consisting of surgical debulking and chemotherapy, 8 out of 10 patients recur. In the recurrence setting, the presentation of widespread micrometastasis, which limits the usefulness of surgery, is complicated by concurrent presentation of chemoresistance. Currently, no adequate therapy is able to prevent or treat recurrence. Consequently, therapies directed against control of tumor burden can improve prognosis in EOC patients.

Recently we reported the characterization of CD44+/MyD88+ EOC cells with tumor-initiating properties and inherent chemoresistance. In addition, we have identified ME-344, a novel isoflavone derivate, with potent capacity to induce cell death in these cells. Furthermore, we have developed an intra-peritoneal (i.p.) in vivo model of EOC recurrence based on the capacity of these cells to survive chemotherapy and renew the tumor. Using this model, we show the potential efficacy of ME-344 in delaying carcinomatosis and decreasing tumor burden.

Methods: CD44+/MyD88+/mCherry+ EOC stem cells are injected i.p. in nude mice. Tumors are detected and consequently followed by live in vivo imaging using In Vivo FX System. Once tumors are detected, mice received 4 doses of 12 mg/kg i.p. Paclitaxel q3d or until the animals are free of disease. Mice were then randomized to maintenance with Vehicle or ME-344 (100 mg/kg i.p. q3d) and further monitored for recurrence. Recurrence is defined as appearance of tumors with ROI interior area &gt; 2000. Tumor growth delay is defined as the difference in days when treated and control groups reach the maximal tumor burden set at ROI interior area = 10,000.

Results: Mice exhibited recurrence with an average time of 6 days in the Vehicle group and 7 days in the ME-344 group. However, a significant delay in tumor kinetics was observed in the group maintained with ME-344. Maximal tumor burden, defined as ROI interior area = 10,000, was reached in the control group within 24 days and in the ME-344 group within 39 days. Thus, tumor growth was delayed for 15 days.

Conclusion: Maintenance with ME-344 is able to decrease tumor burden in this very aggressive in vivo model of EOC recurrence. In this study, we show a significant delay in tumor kinetics in mice that were maintained with ME-344 following initial response to Paclitaxel. Decreasing and delaying metastatic load will allow more optimal surgical debulking and may improve survival in EOC patients. These results suggest the potential value of ME-344 therapy after 1st line standard of care in EOC patients.

Citation Format: Ayesha B. Alvero, Natalia Sumi, Vinicius Craveiro, Won Duk Joo, Yang Yang-Hartwich, Gil Mor. ME-344 delays tumor kinetics in an ovarian cancer in vivo recurrence model. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-286. doi:10.1158/1538-7445.AM2013-LB-286

TLR2 enhances ovarian cancer stem cell self-renewal and promotes tumor repair and recurrence

Primary ovarian cancer is responsive to treatment, but chemoresistant recurrent disease ensues in majority of patients. Recent compelling evidence demonstrates that a specific population of cancer cells, the cancer stem cells, initiates and sustains tumors. It is therefore possible that this cell population is also responsible for recurrence. We have shown previously that CD44+/MyD88+ epithelial ovarian cancer stem cells (CD44+/MyD88+ EOC stem cells) are responsible for tumor initiation. In this study, we demonstrate that this population drives tumor repair following surgery- and chemotherapy-induced tumor injury. Using in vivo and in vitro models, we also demonstrate that during the process of tumor repair, CD44+/MyD88+ EOC stem cells undergo self-renewal as evidenced by upregulation of stemness-associated genes. More importantly, we show that a pro-inflammatory microenvironment created by the TLR2-MyD88-NFκB pathway supports EOC stem cell-driven repair and self-renewal. Overall, our findings point to a specific cancer cell population, the CD44+/MyD88+ EOC stem cells and a specific pro-inflammatory pathway, the TLR2-MyD88-NFκB pathway, as two of the required players promoting tumor repair, which is associated with enhanced cancer stem cell load. Identification of these key players is the first step in elucidating the steps necessary to prevent recurrence in EOC patients.