Immune Modulation of Innate and Adaptive Responses Restores Immune Surveillance and Establishes Antitumor Immunologic Memory

Current immunotherapies have proven effective in strengthening antitumor immune responses, but constant opposing signals from tumor cells and the surrounding microenvironment eventually lead to immune escape. We hypothesized that in situ release of antigens and regulation of both the innate and adaptive arms of the immune system would provide a robust and long-term antitumor effect by creating immunologic memory against tumors. To achieve this, we developed CARG-2020, a genetically modified virus-like vesicle (VLV) that is a self-amplifying RNA with oncolytic capacity and encodes immune regulatory genes. CARG-2020 carries three immune modulators: (i) the pleiotropic antitumor cytokine IL12, in which the subunits (p35 and p40) are tethered together; (ii) the extracellular domain (ECD) of the protumor IL17RA, which serves as a dominant-negative antagonist; and (iii) a shRNA targeting PD-L1. Using a mouse model of ovarian cancer, we demonstrated the oncolytic effect and immune-modulatory capacities of CARG-2020. By enhancing IL12 and blocking IL17 and PD-L1, CARG-2020 successfully reactivated immune surveillance by promoting M1, instead of M2, macrophage differentiation, inhibiting MDSC expansion and establishing a potent CD8+ T cell-mediated antitumoral response. Furthermore, we demonstrated that this therapeutic approach provided tumor-specific and long-term protection against the establishment of new tumors. Our results provide a rationale for the further development of this platform as a therapeutic modality for ovarian cancer patients to enhance antitumor responses and prevent a recurrence.

An Ex Vivo Model of Ovarian Cancer Peritoneal Metastasis Using Human Omentum

Ovarian cancer is the deadliest gynecologic malignancy. The omentum plays a key role in providing a supportive microenvironment to metastatic ovarian cancer cells as well as immune modulatory signals that allow tumor tolerance. However, we have limited models that closely mimic the interaction between ovarian cancer cells and adipose-rich tissues. To further understand the cellular and molecular mechanisms by which the omentum provides a pro-tumoral microenvironment, we developed a unique 3D ex vivo model of cancer cell-omentum interaction. Using human omentum, we are able to grow ovarian cancer cells within this adipose-rich microenvironment and monitor the factors responsible for tumor growth and immune regulation. In addition to providing a platform for the study of this adipose-rich tumor microenvironment, the model provides an excellent platform for the development and evaluation of novel therapeutic approaches to target metastatic cancer cells in this niche. The proposed model is easy to generate, inexpensive, and applicable to translational investigations.

Adipose-derived exosomal miR-421 targets CBX7 and promotes metastatic potential in ovarian cancer cells

BACKGROUND

Chromobox protein homolog 7 (CBX7), a member of the Polycomb repressor complex, is a potent epigenetic regulator and gene silencer. Our group has previously reported that CBX7 functions as a tumor suppressor in ovarian cancer cells and its loss accelerated formation of carcinomatosis and drove tumor progression in an ovarian cancer mouse model. The goal of this study is to identify specific signaling pathways in the ovarian tumor microenvironment that down-regulate CBX7. Given that adipocytes are an integral component of the peritoneal cavity and the ovarian tumor microenvironment, we hypothesize that the adipose microenvironment is an important regulator of CBX7 expression.

RESULTS

Using conditioned media from human omental explants, we found that adipose-derived exosomes mediate CBX7 downregulation and enhance migratory potential of human ovarian cancer cells. Further, we identified adipose-derived exosomal miR-421 as a novel regulator of CBX7 expression and the main effector that downregulates CBX7.

CONCLUSION

In this study, we identified miR-421 as a specific signaling pathway in the ovarian tumor microenvironment that can downregulate CBX7 to induce epigenetic change in OC cells, which can drive disease progression. These findings suggest that targeting exosomal miR-421 may curtail ovarian cancer progression.

Adipose-derived exosomal miR-421 targets CBX7 and promotes metastatic potential in ovarian cancer cells

Background

Chromobox protein homolog 7 (CBX7), a member of the Polycomb repressor complex, is a potent epigenetic regulator and gene silencer. Our group has previously reported that CBX7 functions as a tumor suppressor in ovarian cancer cells and its loss accelerated formation of carcinomatosis and drove tumor progression in an ovarian cancer mouse model. The goal of this study is to identify specific signaling pathways in the ovarian tumor microenvironment that down-regulate CBX7. Given that adipocytes are an integral component of the peritoneal cavity and the ovarian tumor microenvironment, we hypothesize that the adipose microenvironment is an important regulator of CBX7 expression.

Results

Using conditioned media from human omental explants, we found that adipose-derived exosomes mediate CBX7 downregulation and enhance migratory potential of human ovarian cancer cells. Further, we identified adipose-derived exosomal miR-421 as a novel regulator of CBX7 expression and the main effector that downregulates CBX7.

Conclusion

In this study, we identified miR-421 as a specific signaling pathway in the ovarian tumor microenvironment that can downregulate CBX7 to induce epigenetic change in OC cells, which can drive disease progression. These findings suggest that targeting exosomal miR-421 may curtail ovarian cancer progression.

A Novel Role of Connective Tissue Growth Factor in the Regulation of the Epithelial Phenotype

BACKGROUND

Epithelial-mesenchymal transition (EMT) is a biological process where epithelial cells lose their adhesive properties and gain invasive, metastatic, and mesenchymal properties. Maintaining the balance between the epithelial and mesenchymal stage is essential for tissue homeostasis. Many of the genes promoting mesenchymal transformation have been identified; however, our understanding of the genes responsible for maintaining the epithelial phenotype is limited. Our objective was to identify the genes responsible for maintaining the epithelial phenotype and inhibiting EMT.

METHODS

RNA seq was performed using an vitro model of EMT. CTGF expression was determined via qPCR and Western blot analysis. The knockout of CTGF was completed using the CTGF sgRNA CRISPR/CAS9. The tumorigenic potential was determined using NCG mice.

RESULTS

The knockout of CTGF in epithelial ovarian cancer cells leads to the acquisition of functional characteristics associated with the mesenchymal phenotype such as anoikis resistance, cytoskeleton remodeling, increased cell stiffness, and the acquisition of invasion and tumorigenic capacity.

CONCLUSIONS

We identified CTGF is an important regulator of the epithelial phenotype, and its loss is associated with the early cellular modifications required for EMT. We describe a novel role for CTGF, regulating cytoskeleton and the extracellular matrix interactions necessary for the conservation of epithelial structure and function. These findings provide a new window into understanding the early stages of mesenchymal transformation.

Immune modulation of innate and adaptive responses restores immune surveillance and establishes anti-tumor immunological memory

Current immunotherapies have proven effective in strengthening anti-tumor immune responses but constant opposing signals from tumor cells and surrounding microenvironment eventually lead to immune escape. We hypothesize that in situ release of antigens and regulation of both the innate and adaptive arms of the immune system will provide a robust and long-term anti-tumor effect by creating immunological memory against the tumor. To achieve this, we developed CARG-2020, a virus-like-vesicle (VLV). It is a genetically modified and self-amplifying RNA with oncolytic capacity and encodes immune regulatory genes. CARG-2020 carries three transgenes: 1 ) the pleiotropic antitumor cytokine IL-12 in which the subunits (p35 and p40) are tethered together; 2) the extracellular domain (ECD) of the pro- tumor IL-17RA, which can serve as a dominant negative antagonist; and 3) shRNA for PD-L1. Using a mouse model of ovarian cancer, we demonstrate the oncolytic effect and immune modulatory capacities of CARG-2020. By enhancing IL-12 and blocking IL-17 and PD-L1, CARG-2020 successfully reactivates immune surveillance by promoting M1 instead of M2 macrophage differentiation, inhibiting MDSC expansion, and establishing a potent CD8+ T cell mediated anti-tumoral response. Furthermore, we demonstrate that this therapeutic approach provides tumor-specific and long-term protection preventing the establishment of new tumors. Our results provide rationale for the further development of this platform as a therapeutic modality for ovarian cancer patients to enhance the anti-tumor response and to prevent recurrence.

Immunological modifications following chemotherapy are associated with delayed recurrence of ovarian cancer

Introduction

Ovarian cancer recurs in most High Grade Serous Ovarian Cancer (HGSOC) patients, including initial responders, after standard of care. To improve patient survival, we need to identify and understand the factors contributing to early or late recurrence and therapeutically target these mechanisms. We hypothesized that in HGSOC, the response to chemotherapy is associated with a specific gene expression signature determined by the tumor microenvironment. In this study, we sought to determine the differences in gene expression and the tumor immune microenvironment between patients who show early recurrence (within 6 months) compared to those who show late recurrence following chemotherapy.

Methods

Paired tumor samples were obtained before and after Carboplatin and Taxol chemotherapy from 24 patients with HGSOC. Bioinformatic transcriptomic analysis was performed on the tumor samples to determine the gene expression signature associated with differences in recurrence pattern. Gene Ontology and Pathway analysis was performed using AdvaitaBio's iPathwayGuide software. Tumor immune cell fractions were imputed using CIBERSORTx. Results were compared between late recurrence and early recurrence patients, and between paired pre-chemotherapy and post-chemotherapy samples.

Results

There was no statistically significant difference between early recurrence or late recurrence ovarian tumors pre-chemotherapy. However, chemotherapy induced significant immunological changes in tumors from late recurrence patients but had no impact on tumors from early recurrence patients. The key immunological change induced by chemotherapy in late recurrence patients was the reversal of pro-tumor immune signature.

Discussion

We report for the first time, the association between immunological modifications in response to chemotherapy and the time of recurrence. Our findings provide novel opportunities to ultimately improve ovarian cancer patient survival.

Generation of Stable Epithelial-Mesenchymal Hybrid Cancer Cells with Tumorigenic Potential

PURPOSE

Cancer progression, invasiveness, and metastatic potential have been associated with the activation of the cellular development program known as epithelial-to-mesenchymal transition (EMT). This process is known to yield not only mesenchymal cells, but instead an array of cells with different degrees of epithelial and mesenchymal phenotypes with high plasticity, usually referred to as E/M hybrid cells. The characteristics of E/M hybrid cells, their importance in tumor progression, and the key regulators in the tumor microenvironment that support this phenotype are still poorly understood.

METHODS

In this study, we established an in vitro model of EMT and characterized the different stages of differentiation, allowing us to identify the main genomic signature associated with the E/M hybrid state.

RESULTS

We report that once the cells enter the E/M hybrid state, they acquire stable anoikis resistance, invasive capacity, and tumorigenic potential. We identified the hepatocyte growth factor (HGF)/c-MET pathway as a major driver that pushes cells in the E/M hybrid state.

CONCLUSIONS

Herein, we provide a detailed characterization of the signaling pathway(s) promoting and the genes associated with the E/M hybrid state.

MNRR1 is a driver of ovarian cancer progression

Cancer progression requires the acquisition of mechanisms that support proliferative potential and metastatic capacity. MNRR1 (also CHCHD2, PARK22, AAG10) is a bi-organellar protein that in the mitochondria can bind to Bcl-xL to enhance its anti-apoptotic function, or to respiratory chain complex IV (COX IV) to increase mitochondrial respiration. In the nucleus, it can act as a transcription factor and promote the expression of genes involved in mitochondrial biogenesis, migration, and cellular stress response. Given that MNRR1 can regulate both apoptosis and mitochondrial respiration, as well as migration, we hypothesize that it can modulate metastatic spread. Using ovarian cancer models, we show heterogeneous protein expression levels of MNRR1 across samples tested and cell-dependent control of its stability and binding partners. In addition to its anti-apoptotic and bioenergetic functions, MNRR1 is both necessary and sufficient for a focal adhesion and ECM repertoire that can support spheroid formation. Its ectopic expression is sufficient to induce the adhesive glycoprotein THBS4 and the type 1 collagen, COL1A1. Conversely, its deletion leads to significant downregulation of these genes. Furthermore, loss of MNRR1 leads to delay in tumor growth, curtailed carcinomatosis, and improved survival in a syngeneic ovarian cancer mouse model. These results suggest targeting MNRR1 may improve survival in ovarian cancer patients.

TWIST1 induces proteasomal degradation of β-catenin during the differentiation of ovarian cancer stem-like cells

Ovarian cancer (OC) is one of the leading gynecologic cancers worldwide. Cancer stem-like cells are correlated with relapse and resistance to chemotherapy. Twist1, which is involved in ovarian cancer stem-like cell differentiation, is positively correlated with CTNNB1 in different differentiation stages of ovarian cancer cells: primary epithelial ovarian cancer cells (primary EOC cells), mesenchymal spheroid-forming cells (MSFCs) and secondary epithelial ovarian cancer cells (sEOC cells). However, the expression of β-catenin is inversed compared to CTNNB1 in these 3 cell states. We further demonstrated that β-catenin is regulated by the protein degradation system in MSFCs and secondary EOC but not in primary EOC cells. The differentiation process from primary EOC cells to MSFCs and sEOC cells might be due to the downregulation of β-catenin protein levels. Finally, we found that TWIST1 can enhance β-catenin degradation by upregulating Axin2.

Regulatory Role of the Adipose Microenvironment on Ovarian Cancer Progression

Simple Summary

Adipocytes or fat cells are integral part of the ovarian tumor microenvironment. Secreted factors from adipocytes, as well as direct cell-to-cell interaction with ovarian cancer cells have been shown to directly support ovarian tumor progression. Elucidating the molecular pathways involved is crucial in the identification of relevant targets.

Abstract

The tumor microenvironment of ovarian cancer is the peritoneal cavity wherein adipose tissue is a major component. The role of the adipose tissue in support of ovarian cancer progression has been elucidated in several studies from the past decades. The adipocytes, in particular, are a major source of factors, which regulate all facets of ovarian cancer progression such as acquisition of chemoresistance, enhanced metastatic potential, and metabolic reprogramming. In this review, we summarize the relevant studies, which highlight the role of adipocytes in ovarian cancer progression and offer insights into unanswered questions and possible future directions of research.

Abstract 2333: EMT programs ovarian cancer cells to survive the adipocyte-rich microenvironment

Background: Metabolic pathways are non-canonical targets of the EMT program. The relevance of re-programming metabolism during the metastasis cascade is underscored in ovarian cancer cells, which primarily metastasizes to the adipocyte-rich omentum. Ovarian cancer-adipocyte interaction has been shown to promote fatty acid (FA) uptake into the cancer cells. These FA are then catabolized via β-oxidation thus providing the energy required for rapid tumor growth. β-oxidation of FA requires efficient mitochondria and oxygen processing. The objective of this study is to determine if E/M status determine adaptation and survival in adipocyte-rich microenvironment.

Materials and Methods: RNA seq was performed in Ck18+/Twist- epithelial and Ck18-/Twist+ mesenchymal human ovarian cancer cells. Pathway and Gene Ontology analyses were performed on differentially expressed (DEX) genes (FC>2 and p<0.05) using iPathway Guide. Protein levels were determined by western blot. Oxygen consumption rate was measured using Seahorse XF Analyzer. Cell viability was quantified using CelltoxTM Green viability dye.

Results: Pathway analysis of DEX genes with focus on metabolic pathways showed the following DEX pathways: glycolysis/gluconeogenesis (p=0.008); pyruvate metabolism (0.019); fatty acid degradation (p=0.01); fatty acid elongation (0.008). Gene ontology analysis showed significant difference in GO:0006979: response to oxidative stress (p=0.007). Further analysis of DEX genes within these pathways showed upregulation in mesenchymal cancer cells of both pyruvate dehydrogenase subunits, PDHA1 (p = 0.011) and PDHB (p=0.014) and upregulation of carnitine palmitoyltransferase (CPT1; p=0.011), the rate limiting enzyme in FA β-oxidation. The upregulation of these genes was validated at the protein level by western blot analysis, which also showed increased levels of COX-IV in mesenchymal cancer cells compared to epithelial cancer cells. Moreover, mesenchymal cells exhibited enhanced maximal respiration and enhanced spare respiratory capacity. Finally, viability studies conclusively demonstrate the metabolic flexibility in mesenchymal cancer cells, which maintained viability upon nutrient deprivation suggesting metabolic plasticity. In contrast, cell death was observed epithelial cancer cells upon nutrient deprivation, which was rescued by the addition of glucose but not the FA, oleic acid.

Conclusion: Ovarian cancer cells acquire enhanced pyruvate shuttling to the TCA cycle, a more efficient FA β-oxidation machinery, as well as more efficient oxygen processing during EMT. These phenotypes are relevant in supporting survival in the adipocyte microenvironment. Further elucidation of EMT related pathways that re-program lipid metabolism may lead to better control of carcinomatosis in ovarian cancer patients.

Citation Format: Hussein Chehade, Alexandra Fox, Roslyn Tedja, Radhika Gogoi, Gil Mor, Ayesha B. Alvero. EMT programs ovarian cancer cells to survive the adipocyte-rich microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2333.

Abstract 1150: CARG-2020 artificial oncolytic virus delivering three immune-modulators prevents tumor recurrence in a syngeneic model of ovarian cancer

Background: Ovarian cancer is the most lethal of all gynecologic malignancies with a grim 5-year survival rate of ~47%. Mortality occurs in the setting of recurrent disease wherein the co-presentation of chemoresistance and carcinomatosis limits the value of standard of care. It is therefore imperative to develop approaches that can prevent recurrent ovarian cancer. Oncolytic viruses are genetically modified replication competent viruses that can selectively infect cancer cells to induce cell lysis and death. This approach has proven to be clinically safe making it a promising approach to complement standard of care. The objective of this study is to evaluate the efficacy of CARG-2020, a virus-like vesicles (VLV) delivering three immune-modulators including IL-12, IL-17 antagonist and shRNA-PD-L1 in preventing recurrent disease in a syngeneic mouse model of recurrent ovarian cancer.

Materials and Methods: In vitro: Triple knockout (TKO; p53LSL-R172H/Dicerflox/flox/Ptenflox/flox) mouse ovarian cancer cells were seeded in 96-well plates and treated with different doses of CARG-2020. Cell death was determined using the Incucyte imaging system. In vivo: TKO ovarian cancer cells stably expressing the mCherry fluorescent protein were injected i.p. in C57bl/6 mice (day 0) to mimic the establishment of recurrent disease. Treatment commenced on day 3 with the treatment group receiving three doses of 1x10^8 PFU of CARG-2020 given every other day (n=5). Control group received PBS (n=5). Both treatments were given i.p. Tumor growth was monitored by live imaging using mCherry fluorescence ROI area. Progression-free survival (PFS) was defined as the day ROI area reached 2,000.

Results: CARG-2020 (1x10^5 PFU) demonstrated cytolytic effect in vitro and induced 100% cell death within 24h. In vivo, CARG-2020 induced significant decrease in i.p. tumor growth (p = 0.0128) compared to PBS control. Treatment with CARG-2020 completely delayed the establishment of recurrent disease (PFS, p = 0.0003). Whereas PBS control group demonstrated median PFS of 20 days, mice in the CARG-2020 group remained disease-free until day 60.

Conclusion: CARG-2020 is able to prevent the establishment of recurrent disease in a syngeneic mouse model of recurrent ovarian cancer. Our results provide rationale for the further development of this platform as a therapeutic modality for ovarian cancer patients.

Citation Format: Ayesha B. Alvero, Alexandra Fox, Bhaskara Madina, Valerian Nakaar, Timur Yarovinsky, Marie Krady, Bijan Almassian, Gil Mor. CARG-2020 artificial oncolytic virus delivering three immune-modulators prevents tumor recurrence in a syngeneic model of ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1150.

Ovarian cancer modulates the immunosuppressive function of CD11b+Gr1+ myeloid cells via glutamine metabolism

Objective

Immature CD11b ⁺ Gr1⁺ myeloid cells that acquire immunosuppressive capability, also known as myeloid-derived suppressor cells (MDSCs), are a heterogeneous population of cells that regulate immune responses. Our study's objective was to elucidate the role of ovarian cancer microenvironment in regulating the immunosuppressive function of CD11b⁺Gr1⁺ myeloid cells.

Methods

All studies were performed using the intraperitoneal ID8 syngeneic epithelial ovarian cancer mouse model. Myeloid cell depletion and immunotherapy were carried out using anti-Gr1 mAb, gemcitabine treatments, and/or anti-PD1 mAb. The treatment effect was assessed by a survival curve, in situ luciferase-guided imaging, and histopathologic evaluation. Adoptive transfer assays were carried out between congenic CD45.2 and CD45.1 mice. Immune surface and intracellular markers were assessed by flow cytometry. ELISA, western blot, and RT-PCR techniques were employed to assess the protein and RNA expression of various markers. Bone marrow-derived myeloid cells were used for ex-vivo studies.

Results

The depletion of Gr1⁺ immunosuppressive myeloid cells alone and in combination with anti-PD1 immunotherapy inhibited ovarian cancer growth. In addition to the adoptive transfer studies, these findings validate the role of immunosuppressive CD11b⁺Gr1⁺ myeloid cells in promoting ovarian cancer. Mechanistic investigations showed that ID8 tumor cells and their microenvironments produced recruitment and regulatory factors for immunosuppressive CD11b⁺Gr1⁺ myeloid cells. CD11b⁺Gr1⁺ myeloid cells primed by ID8 tumors showed increased immunosuppressive marker expression and acquired an energetic metabolic phenotype promoted primarily by increased oxidative phosphorylation fueled by glutamine. Inhibiting the glutamine metabolic pathway reduced the increased oxidative phosphorylation and decreased immunosuppressive markers’ expression and function. Dihydrolipoamide succinyl transferase (DLST), a subunit of α-KGDC in the TCA cycle, was found to be the most significantly elevated gene in tumor-primed myeloid cells. The inhibition of DLST reduced oxidative phosphorylation, immunosuppressive marker expression and function in myeloid cells.

Conclusion

Our study shows that the ovarian cancer microenvironment can regulate the metabolism and function of immunosuppressive CD11b ⁺ Gr1⁺ myeloid cells and modulate its immune microenvironment. Targeting glutamine metabolism via DLST in immunosuppressive myeloid cells decreased their activity, leading to a reduction in the immunosuppressive tumor microenvironment. Thus, targeting glutamine metabolism has the potential to enhance the success of immunotherapy in ovarian cancer.

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Ovarian cancer microenvironment increases the immunosuppressive ability of myeloid cells.

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Ovarian cancer microenvironment can induce metabolic reprogramming in the immunosuppressive myeloid cells.

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Immunosuppressive myeloid cells upsurge their oxidative metabolism fueled by glutamine in ovarian cancer.

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DLST, a component of alpha-ketoglutarate dehydrogenase complex plays a key role in the immunometabolic regulation of immunosuppressive myeloid cells in ovarian cancer.

Automated Assay of a Four-Protein Biomarker Panel for Improved Detection of Ovarian Cancer

Simple Summary

The survival of patients diagnosed with ovarian cancer depends largely on the extent of the disease upon diagnosis. When confined to the ovaries, patients’ 10-year survival is more than 70%. This drastically drops to less than 5% when patients are diagnosed with far-advanced disease. Unfortunately, more than 80% of patients are diagnosed at advanced stage due to the lack of test for early detection. We report the development of a blood test measuring four proteins (macrophage migration inhibitory factor, osteopontin, prolactin and cancer antigen 125), which can distinguish ovarian cancer samples, even early-stage disease, from healthy samples in the population tested. This study is another step towards the application of a useful test for early detection of ovarian cancer that is both highly accurate and specific.

Abstract

Background: Mortality from ovarian cancer remains high due to the lack of methods for early detection. The difficulty lies in the low prevalence of the disease necessitating a significantly high specificity and positive-predictive value (PPV) to avoid unneeded and invasive intervention. Currently, cancer antigen- 125 (CA-125) is the most commonly used biomarker for the early detection of ovarian cancer. In this study we determine the value of combining macrophage migration inhibitory factor (MIF), osteopontin (OPN), and prolactin (PROL) with CA-125 in the detection of ovarian cancer serum samples from healthy controls. Materials and Methods: A total of 432 serum samples were included in this study. 153 samples were from ovarian cancer patients and 279 samples were from age-matched healthy controls. The four proteins were quantified using a fully automated, multi-analyte immunoassay. The serum samples were divided into training and testing datasets and analyzed using four classification models to calculate accuracy, sensitivity, specificity, PPV, negative predictive value (NPV), and area under the receiver operating characteristic curve (AUC). Results: The four-protein biomarker panel yielded an average accuracy of 91% compared to 85% using CA-125 alone across four classification models (p = 3.224 × 10⁻⁹). Further, in our cohort, the four-protein biomarker panel demonstrated a higher sensitivity (median of 76%), specificity (median of 98%), PPV (median of 91.5%), and NPV (median of 92%), compared to CA-125 alone. The performance of the four-protein biomarker remained better than CA-125 alone even in experiments comparing early stage (Stage I and Stage II) ovarian cancer to healthy controls. Conclusions: Combining MIF, OPN, PROL, and CA-125 can better differentiate ovarian cancer from healthy controls compared to CA-125 alone.

Subcellular Fractionation to Demonstrate Activation of Intrinsic Apoptotic Pathway

Within the cell, proteins are segregated into different organelles depending on their function and activation status. In response to stimulus, posttranslational modifications or loss of organelle membrane integrity lead to the movement of proteins from one compartment to another. This movement of proteins or protein translocation, exerts a significant effect on protein function. This is clearly demonstrated in the context of apoptosis wherein the cytoplasmic translocation of the mitochondrial resident protein, cytochrome C, initiates the activation of the intrinsic arm of the apoptotic pathway. Experimentally, protein translocation can be demonstrated by subcellular fractionation and subsequent western blot analysis of the isolated fractions. This chapter describes the step-by-step procedure in obtaining mitochondrial and cytoplasmic fractions from cell pellets and determining their purity and integrity.

Determination of Caspase Activation by Western Blot

Apoptosis is a type of programmed cell death induced by a cascade of biochemical events, which leads to distinct morphological changes characterized by cell shrinkage, membrane blebbing, chromatin condensation, and DNA fragmentation. Apoptosis is executed by a class of cysteine proteases called caspases. Caspases are synthesized as inactive pro-caspases and activated by a series of cleavage reactions. Active caspases cleave cellular substrates and are thus the main effectors of the apoptotic cell death pathway. Detection of caspase cleavage by western blot analysis is a conventional method to demonstrate the induction of apoptosis. In the context of apoptosis, the proper analysis of western blot results depends on the understanding of the mechanisms and outcomes of caspase processing during the course of its activation. In this chapter, we describe the step-by-step methodology in the western blot analysis of caspase cleavage during apoptosis. We detail protocols for protein extraction, quantitation, casting, and running gel electrophoresis and western blot analysis of caspase -8 and caspase -9 activation. The described methods can be applied to any particular protein of interest.

Abstract A02: CBX7 binds TWIST-1’s E-box to inhibit TWIST-1 function and curtail tumorigenecity and metastatic potential in ovarian cancer

Introduction: Ovarian cancer metastasizes via the transcoelomic route and yields overwhelmingly numerous micrometastases. This clinical presentation limits the value of standard of care and contributes to patient mortality. Whereas EMT is required in the acquisition of a migratory phenotype, MET has been shown to occur on secondary sites leading to the establishment of metastasis. The nature of the ovarian cancer cells that result after MET is, however, yet to be fully characterized. Whether these secondary epithelial ovarian cancer cells (sEOC) are required to repeat EMT in order to generate additional metastatic sites is not known. The objectives of this study are twofold: to determine if full MET occurs on secondary sites, and to determine mechanisms that confer to disseminated ovarian cancer cells the ability to rapidly spread and form the characteristic micrometastatic disease.

Materials and Methods: Ovarian cancer spheroids were derived from three epithelial ovarian cancer (EOC) cell lines (OVCAR3, R182, R2615). sEOC were derived from the spheroids by plating in tissue culture-treated plates. Gene signature pattern was determined by RNAseq. mRNA and protein levels were quantified by RT-qPCR and Western blot, respectively. TWIST-1 activity was measured by a luciferase reporter system. Promoter binding was determined by anti-CBX7 chromatin IP followed by PCR. CBX7 was knocked out (KO) using CRISPR-Cas9. Tumorigenic potential was quantified by measuring resulting intraperitoneal burden (g) in nude mice.

Results: PCA and clustering analysis of RNA-seq data showed sEOC do not fully recapitulate the molecular signature of the primary EOC cells from which they are derived. Despite displaying an epithelial morphology, sEOC maintain a high expression of the classical mesenchymal effector, TWIST-1. TWIST-1 is, however, transcriptionally inactive in these cells as it is inhibited by the PcG protein, CBX7. KO of CBX7 in sEOC was sufficient to promote a mesenchymal morphology, significantly promote TWIST-1-induced transcription of mir-199A (p = 0.004, wt vs. CBX7KO), and induce higher protein levels of FOXC2. CBX7 precludes TWIST-1 from accessing its promoter by binding at or near the E box. Finally, KO of CBX7 was able to significantly enhance tumorigenicity and increase tumor load and metastatic potential in vivo (p=0.033, wt vs CBX7 KO).

Conclusion: We demonstrate that full MET does not occur in ovarian cancer cells at secondary metastatic sites. Although sEOC display an epithelial morphology, they do not achieve the full molecular signature of the primary EOC cells from which they are derived. sEOC maintain high levels of TWIST-1 whose activity is inhibited by CBX7. This regulation allows secondary tumors to achieve an epithelial morphology while conferring the advantage to achieve a prompt reversal to a mesenchymal morphology and gain in tumorigenic potential upon perturbation of CBX7. This may explain ovarian cancer’s rapid progression and characteristic micrometastatic disease.

Citation Format: Juanni Li, Ayesha B Alvero, Sudhakar Nuti, Roslyn Tedja, Cai M. Roberts, Mary Pitruzzello, Yimin Li, Qing Xiao, Sai Zhang, Yaqi Gan, Gil Mor, Gang Yin. CBX7 binds TWIST-1’s E-box to inhibit TWIST-1 function and curtail tumorigenecity and metastatic potential in ovarian cancer [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 A02.

Abstract A01: Specific targeting of adipose tissue-associated metastasis using bile salt nanoparticles

Purpose: Mortality in ovarian cancer occurs in the setting of recurrent disease. Recurrent disease is known to arise from residual disease, which persists after the conclusion of standard of care, consequently rebuilding the tumor. Adipose tissue provides cancer cells with a unique microenvironment that can enhance survival by upregulating antiapoptosis genes or by decreasing drug bioavailability. Indeed, adipose-rich organs such as the omentum are not only preferential sites for metastasis but also main sites of residual disease in ovarian cancer. We hypothesized that targeting adipose-rich tissues could limit residual disease and prevent recurrence. Thus, the objective of this study was to develop effective drug delivery platforms that can specifically target residual disease in adipose-rich tissues.

Methods: The delivery system is a nanoparticle platform composed of polymerized ursodeoxycholic acid (PUDCA) synthesized by esterification of UDCA monomer. Paclitaxel (PTX) or deep-infrared FL dye (DIR) was encapsulated to a final concentration of 24 ug or 5 mg per mg PUDCA, respectively. In vitro dose response studies were performed using mCherry+ human OCSC1-F2 ovarian cancer cells for 72 h. DMSO-resuspended PTX (DMSO-PTX) was used as control. In vivo studies were performed in athymic nude mice bearing i.p. tumors from mCherry+ OCSC1-F2 cells. For biodistribution studies, DIR-PUDCA was administered as one-time i.p. injection of 1.3 mg of DIR-PUDCA followed by ex vivo measurement of FL intensity after 14 days. DMSO-resuspended DIR (DMSO-DIR) was used as control. For efficacy studies, the groups were: (1) vehicle control; (2) taxol (PTX in Cremaphor; 12mg/kg) + DMSO-PTX (31.2 ug PTX); and (3) taxol + PUDCA-PTX. Treatment was administered i.p. twice a week for a total of 4 doses. Tumor burden and residual disease were determined by quantification of mCherry ROI FL area.

Results: PUDCA-PTX demonstrated significantly improved efficacy both in vitro and in vivo. PUDCA-PTX demonstrated a six-fold reduction in in vitro GI50 compared to DMSO-PTX (23.04 nM PUDCA-PTX vs. 137.2 nM DMSO-PTX). Biodistribution studies showed delivery of DIR specifically to adipose-rich tissues (DIR mean FL intensity (MFI) for greater and lesser omentum = 76570±17808 vs. mesentery MFI = 22326±2956; p = 0.0297). Efficacy studies showed that PUDCA-PTX was significantly more effective in inhibiting tumor progression (p = 0.0191) and, more importantly, in preventing recurrent disease compared to DMSO-PTX. Finally, PUDCA-PTX was able to significantly reduce omental-residual disease compared to DMSO-PTX (p=0.049).

Conclusion: We demonstrate for the first time that PUDCA is able to target residual disease localized in adipocyte-rich tissues and that this significantly delays tumor progression and prevents recurrence. These results underscore the value of i.p.-delivered PUDCA as a drug delivery platform for enhanced targeting of cancer cells within adipose-rich tissues and its value in the management of ovarian cancer patients.

Citation Format: Roslyn Tedja, Ayesha B. Alvero, Jung Seok Lee, Mary Pitruzzello, Tarek Fahmy, Gil G. Mor. Specific targeting of adipose tissue-associated metastasis using bile salt nanoparticles [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 A01.

Transimmunization restores immune surveillance and prevents recurrence in a syngeneic mouse model of ovarian cancer

Ovarian cancer accounts for most deaths from gynecologic malignancies. Although more than 80% of patients respond to first-line standard of care, most of these responders present with recurrence and eventually succumb to carcinomatosis and chemotherapy-resistant disease. To improve patient survival, new modalities must, therefore, target or prevent recurrent disease. Here we describe for the first time a novel syngeneic mouse model of recurrent high-grade serous ovarian cancer (HGSOC), which allows immunotherapeutic interventions in a time course relevant to human carcinomatosis and disease course. Using this model, we demonstrate the efficacy of Transimmunization (TI), a dendritic cell (DC) vaccination strategy that uses autologous and physiologically derived DC loaded with autologous whole tumor antigens. TI has been proven successful in the treatment of human cutaneous T cell lymphoma and we report for the first time its in vivo efficacy against an intra-peritoneal solid tumor. Given as a single therapy, TI is able to elicit an effective anti-tumor immune response and inhibit immune-suppressive crosstalks with sufficient power to curtail tumor progression and establishment of carcinomatosis and recurrent disease. Specifically, TI is able to inhibit the expansion of tumor-associated macrophages as well as myeloid-derived suppressive cells consequently restoring T cell immune-surveillance. These results demonstrate the possible value of TI in the management of ovarian cancer and other intra-peritoneal tumors.

CBX7 binds the E-box to inhibit TWIST-1 function and inhibit tumorigenicity and metastatic potential

Deaths from ovarian cancer usually occur when patients succumb to overwhelmingly numerous and widespread micrometastasis. Whereas epithelial-mesenchymal transition is required for epithelial ovarian cancer cells to acquire metastatic potential, the cellular phenotype at secondary sites and the mechanisms required for the establishment of metastatic tumors are not fully determined. Using in vitro and in vivo models we show that secondary epithelial ovarian cancer cells (sEOC) do not fully reacquire the molecular signature of the primary epithelial ovarian cancer cells from which they are derived. Despite displaying an epithelial morphology, sEOC maintains a high expression of the mesenchymal effector, TWIST-1. TWIST-1 is however transcriptionally nonfunctional in these cells as it is precluded from binding its E-box by the PcG protein, CBX7. Deletion of CBX7 in sEOC was sufficient to reactivate TWIST-1-induced transcription, prompt mesenchymal transformation, and enhanced tumorigenicity in vivo. This regulation allows secondary tumors to achieve an epithelial morphology while conferring the advantage of prompt reversal to a mesenchymal phenotype upon perturbation of CBX7. We also describe a subclassification of ovarian tumors based on CBX7 and TWIST-1 expression, which predicts clinical outcomes and patient prognosis.

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 3188: Transimmunization prevents recurrence and reprograms the immune milieu in a mouse model of ovarian cancer

Introduction: Targeting recurrent disease is vital in the improvement of survival in ovarian cancer patients. Transimmunization (TI) is a modification of extracorporeal photochemotherapy, which is a dendritic cell (DC)-based vaccination, currently used in cutaneous T cell lymphoma but has never been tested in gynecologic tumors. The objective of this study is to determine if TI can induce a tumor-specific immune response capable of preventing recurrence in ovarian cancer.

Methods of study: Ovarian cancer cells expressing mCherry fluorescent protein were injected i.p. in C57bl/6 mice to mimic the establishment of recurrent disease. These cells (TKO cancer cells) were isolated from spontaneously formed ovarian tumors from p53LSL-R172H/+Dicerflox/floxPtenflox/flox Amhr2cre/+ mice. Tumor burden was quantified using mCherry fluorescence ROI area. TI vaccination was conducted as follows: (1) cancer cells were treated with 8-MOP and exposed to UVA to induce apoptosis; (2) PBMCs were collected from tumor-bearing mice, mixed with apoptotic cancer cells, and circulated through the TI chamber to induce functional DC from monocytes; (3) cells collected were incubated overnight to facilitate antigen uptake and presentation and injected i.p. Treatment groups were as follows: (1) PBS control, n = 20 ; (2) TI TKO, n =10 (i.e. using apoptotic TKO cells); and (3) TI YUMM, n = 10 (using apoptotic mouse melanoma YUMM1.7 cells as antigen-unrelated control). Immune milieu was characterized by IHC on tumors and FACS analysis using cells isolated from peritoneal lavage.

Results: Eighty percent of mice in the TI TKO group were disease free compared to 35% in the PBS control group and 40% in the TI YUMM group. In addition, TI TKO vaccination (p < 0.0001), but not TI YUMM vaccination (p = 0.1079) induced a statistically significant decrease in tumor kinetics compared to PBS control. IHC analysis showed significantly higher levels of infiltrating CD8+ (p = 0.0037) and CD4+ T cells (p = 0.0079) in TI TKO group compared to PBS group. Similarly, mice in the TI TKO group have higher i.p. levels of CD8+/CD44+/CD62L+ central memory T cells (p = 0.004), higher levels of CD8+/CD44+/CD62L- effector memory T cells (p = 0.03), lower levels of CD8+/CD44-/CD62L+ naïve T cells (p = 0.02), and lower levels of CD11b+/Gr-1high myeloid-derived suppressor cells (p = 0.01) compared to PBS control group. Levels of these cells in TI YUMM group were not significantly different from the PBS control.

Conclusion: We demonstrate for the first time that TI vaccination with autologous cancer cells can prevent recurrence and modify the immune phenotype in ovarian cancer. TI efficacy depends on the tumor antigen source, confirming TI as an antigen-specific DC-based immunotherapy. Our results highlight the value of TI in ovarian cancer and its potential application to other i.p. cancers.

Citation Format: Ayesha B. Alvero, Douglas Hanlon, Mary Pitruzzello, Renata Filler, Eve Robinson, Olga Sobolev, Roslyn Tedja, Alessandra Ventura, Richard L. Edelson, Gil Mor. Transimmunization prevents recurrence and reprograms the immune milieu in a mouse model of ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3188.

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 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 1995: The omentum promotes ovarian cancer cell survival by increasing cell cycle duration and chemoresistance

Background:

Ovarian cancer is the most lethal of all gynecologic cancers. It is characterized by the presence of carcinomatosis at time of presentation and chemoresistant micrometastatic seedings at the time of recurrence. The omentum, an adipocyte-rich organ, is a frequent site of ovarian cancer metastasis in patients and the most common site of post-chemotherapy residual disease in animal models. Whereas previous studies have shown how the adipocyte microenvironment can induce metabolic re-programming in cancer cells, it is not clear if it can regulate pathways that affect chemoresponse. The objective of this study is to determine the effect of the adipocyte microenvironment on pathways that control cell cycle and apoptosis.

Methods:

In vitro: Patient-derived epithelial ovarian cancer cell lines were cultured in the presence of absence of omentum conditioned-media. Cell growth was determined by measuring culture confluence using IncucyteTM. Protein expression was determined by western blot analysis, and flow cytometry. In vivo: Human ovarian cancer xenografts were established intra-peritoneally in nude mice. Tumor implants from adipocyte-rich organs such as the omentum, pelvic fat, and mesentery and tumor implants from non-adipocyte-rich organs such as liver, ovaries, and GI tract were collected and analyzed independently.

Results:

Compared to cells cultured in growth media, epithelial ovarian cancer cells cultured in omentum CM demonstrated a more fibroblastic morphology characterized by elongated shape and bipolarity, significantly slower growth kinetics (p < 0.0001) accompanied by upregulation of the cell cycle inhibitor, p27, and enhanced secretion of the pro-angiogenic factor, VEGF. More importantly, these cells express higher levels of the anti-apoptotic proteins Bclxl and Mcl-1. Consequently, ovarian cancer cells in growth media treated with Carboplatin had a IC50 of 14.5 μg/ml. In contrast, cells cultured in omentum CM demonstrated enhanced resistance to carboplatin with IC50 of > 50 μg/ml.

Analysis of tumor implants in vivo showed similar results as observed in vitro. Thus, tumor implants isolated from adipocyte-rich organs express higher levels of p27, Bclxl, and Mcl-1.

Conclusion:

We demonstrate in this study that the adipocyte microenvironment induces major changes in the phenotype of ovarian cancer cells characterized by morphological changes chemoresistance and growth rate. These findings highlight the importance of the adipocyte microenvironment in the progression of ovarian cancer. Further studies that can identify specific therapeutic targets in the adipocyte-educated chemoresistant ovarian cancer cells may aid in the development of novel therapies and improve patient survival.

Citation Format: Carlos Cardenas, Ayesha B. Alvero, Mary Pitruzzello, Roslyn Tedja, Gil G. Mor. The omentum promotes ovarian cancer cell survival by increasing cell cycle duration and chemoresistance [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 1995. doi:10.1158/1538-7445.AM2017-1995

The unique immunological and microbial aspects of pregnancy

The comparison of the immunological state of pregnancy to an immunosuppressed host-graft model continues to lead research and clinical practice to ill-defined approaches. This Review discusses recent evidence that supports the idea that immunological responses at the receptive maternal-fetal interface are not simply suppressed but are instead highly dynamic. We discuss the crucial role of trophoblast cells in shaping not only the way in which immune cells respond to the invading blastocyst but also how they collectively react to external stimuli. We also discuss the role of the microbiota in promoting a tolerogenic maternal immune system and highlight how subclinical viral infections can disrupt this status quo, leading to pregnancy complications.

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.

Redefining the origin and evolution of ovarian cancer: a hormonal connection

Ovarian cancer has the highest mortality of all female reproductive cancers. Late diagnosis, tumour heterogeneity and the development of chemoresistance contribute to this statistic and work against patient survival. Current studies have revealed novel concepts that impact our view on how ovarian cancer develops. The greatest impact is on our understanding that, as a disease, ovarian cancer has multiple cellular origins and that these malignant precursors are mostly derived from outside of the ovaries. In this review, we propose a new concept of a step-wise developmental process that may underwrite ovarian tumorigenesis and progression: (1) migration/recruitment to the ovaries; (2) seeding and establishment in the ovaries; (3) induction of a dormant cancer stage; and (4) expansion and tumor progression. We will discuss the relationship of each step with the changing ovarian function and milieu during the reproductive age and the subsequent occurrence of menopause. The realization that ovarian cancer development and progression occurs in distinct steps is critical for the search of adequate markers for early detection that will offer personalized strategies for prevention and therapy.

Telomerase Prolongs the Lifespan of Normal Human Ovarian Surface Epithelial Cells Without Inducing Neoplastic Phenotype

OBJECTIVE

The aim of this study was to determine the effects of exogenous expression of the catalytic subunit of telomerase (hTERT) on the lifespan, growth characteristics, and tumorigenicity of normal human ovarian surface epithelial (OSE) cells.

METHODS

Low-passage primary cultures of normal human OSE cells were transfected with hTERT and the resulting cell lines were characterized.

RESULTS

The ectopic expression of hTERT stabilized the telomeres of the OSE cultures above 8 kb. The hTERT-transfected OSE cell lines grew beyond the normal lifespan seen in OSE cells and propagated in culture for more than 40 passages before senescing. Moreover, the hTERT-transfected cells demonstrated extensive proliferative capacity as evidenced by their ability to continuously grow even when seeded at low dilutions. The morphologic features and normal differentiation patterns seen in normal OSE cells were likewise retained by the hTERT-transfected cells. In addition, the cultures remained responsive to physiologic concentrations of epidermal growth factor and transforming growth factor-beta. Changes associated with neoplastic transformation like anchorage-independent growth, tumorigencity and karyotypic instability were not observed.

CONCLUSIONS

We were able to show that the ectopic expression of hTERT in normal human OSE: 1) resulted in cultures with greater growth potential and longer lifespan and 2) did not induce a transformed phenotype previously seen in viral oncogene-transfected OSE cells. The established cell lines would not only provide sufficient material for comprehensive studies to investigate the normal physiology of OSE cells, but could also help in the understanding of the early steps of ovarian carcinogenesis.

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 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

Multiple blocks in the engagement of oxidative phosphorylation in putative ovarian cancer stem cells: implication for maintenance therapy with glycolysis inhibitors

Survival rate in ovarian cancer has not improved since chemotherapy was introduced a few decades ago. The dismal prognosis is mostly due to disease recurrence where majority of the patients succumb to the disease. The demonstration that tumors are comprised of subfractions of cancer cells displaying heterogeneity in stemness potential, chemoresistance, and tumor repair capacity suggests that recurrence may be driven by the chemoresistant cancer stem cells. Thus to improve patient survival, novel therapies should eradicate this cancer cell population. We show that in contrast to the more differentiated ovarian cancer cells, the putative CD44+/MyD88+ ovarian cancer stem cells express lower levels of pyruvate dehydrogenase, Cox–I, Cox-II, and Cox–IV, and higher levels of UCP2. Together, this molecular phenotype establishes a bioenergetic profile that prefers the use of glycolysis over oxidative phosphorylation to generate ATP. This bioenergetic profile is conserved in vivo and therefore a maintenance regimen of 2-deoxyglucose administered after Paclitaxel treatment is able to delay the progression of recurrent tumors and decrease tumor burden in mice. Our findings strongly suggest the value of maintenance with glycolysis inhibitors with the goal of improving survival in ovarian cancer patients.

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.

Abstract 4319: Inability of putative ovarian cancer stem cells to engage OXPHOS confer 2-deoxyglucose-mediated prevention of in vivo recurrence

Background:

Mortality in ovarian cancer does not usually occur at primary diagnosis but rather in the recurrent setting where patients present with chemoresistance and carcinomatosis. Prevention of recurrence can therefore have an impact on patient survival. Due to its inherent chemoresistance, cancer stem cells that are left after surgery are thought to drive recurrent disease owing to its tumor-initiating properties and enhanced capacity for repair. We demonstrate that the putative epithelial ovarian cancer (EOC) stem cells have a unique bioenergetic profile that can be targeted with the goal of delaying and/or preventing recurrent disease.

Methods:

In vitro: Pure clones of CD44+/MyD88+ and CD44-/MyD88- EOC cells were treated with 20 mM 2-DG, 5 μM Oligomycin, or 1 mM dinitrophenol (DNP). ATP levels were quantified using Celltiter Glo. Mitochondrial content and membrane potential (MMP) were measured using Mitotracker Green and Red, respectively. In vivo: CD44+/MyD88+/mCherry+ EOC stem cells were injected i.p. in nude mice. Mice received four doses of 12 mg/kg Paclitaxel q3d and then randomized to maintenance with 2-DG (500 mg/kg every MWF) or maintenance with saline. All treatments were given i.p. Tumors were monitored by live in vivo imaging using In Vivo FX System and quantified using the region of interest (ROI) tool based on mCherry fluorescent area.

Results:

Treatment with Oligomycin or DNP did not affect viability nor ATP content in CD44+/MyD88+ EOC stem cells but 2-DG induced rapid decline in ATP and death, which was not rescued with Succinate co-treatment. In contrast, in CD44-/MyD88- EOC cells, treatment with Oligomycin, DNP, or 2-DG only slightly decreased ATP without inducing cell death. Despite having more mitochondria, EOC stem cells have: (1) lower levels of Cox- I, -II, and -IV; (2) undetectable levels of pyruvate dehydrogenase; (3) and higher levels of UCP2 compared to CD44-/MyD88- EOC cells. Administration of 2-DG, as maintenance treatment post-chemotherapy, significantly delayed progression of recurrent disease and decreased i.p. tumor burden in the xenograft model. All mice maintained in saline recurred with average time-to-recurrence of 11 days. In contrast, only 25% of the mice maintained in 2-DG demonstrated recurrence with average time-to-recurrence of 19 days. Finally, analysis of tumors post-mortem show high levels of the autophagic markers p-AMPK and cleaved LC3 in the 2-DG maintained group compared to control.

Conclusion:

We demonstrate that the exclusive reliance of EOC stem cells to glycolysis to meet its ATP requirement and its inability to engage OXPHOS even under stress conditions can be exploited to target these otherwise chemoresistant cancer cells for the prevention of recurrence. Our results show the potential of maintenance treatment with glycolysis inhibitors, administered following standard chemotherapy, in improving survival in patients with ovarian cancer.

Citation Format: Ayesha B. Alvero, Michele Montagna, Natalia J. Sumi, Won Duk Joo, Vinicius Craveiro, Emma Graham, Gil Mor. Inability of putative ovarian cancer stem cells to engage OXPHOS confer 2-deoxyglucose-mediated prevention of in vivo recurrence. [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 4319. doi:10.1158/1538-7445.AM2014-4319

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 > 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.

Abstract 3471: Paclitaxel selects and enriches for CD44+/MyD88+ ovarian cancer stem cells

Background: Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy. The current standard of care in the treatment of EOC patients is surgical debulking and combination chemotherapy usually with Carboplatin and Paclitaxel. Although effective in majority of the cases, more than 20% of patients do not respond. Moreover, more than 80% of patients present with recurrent disease within 5 years. Therefore, there is an underlying biology that results in the differential response to treatment as well as the occurrence of recurrent disease. Tumors are heterogeneous and consist of multiple types of cancer cells, which exhibit different chemoresponsiveness. Our group previously described the characterization of CD44+/MyD88+ EOC stem cells and demonstrated their tumor-initiating properties. An important characteristic of these cells, which differentiate them from the CD44-/MyD88- EOC cells, is the presence of a functional TLR4-MyD88-NFkB pathway. This pathway confers Paclitaxel resistance to these cells. We hypothesize that a cause for recurrence following Paclitaxel treatment is the selective survival of cancer stem cells capable to recreate the tumor. In this study, we demonstrate that Paclitaxel enriches for the CD44+/MyD88+ EOC stem cells thus promoting recurrence. Methods: In vitro model: co-culture system consisting of (50%:50%) GFP+ CD44+/MyD88+ and RFP+ CD44-/MyD88- cells treated with 0.2 uM Paclitaxel. In vivo model: Ovarian tumors implanted s.c in Nude mice treated with 10 mg/kg Paclitaxel q3d for 21 days. Levels of GFP+ and CD44+ cells were determined by flow cytometry. Klf-4, Nanog, MyD88, and ALDH1 were determined by qPCR or western blot. Results: Control co-cultures were characterized by overgrowth of CD44-/MyD88- EOC cells while the Paclitaxel treated co-cultures had mainly CD44+/MyD88+ EOC stem cells. Similarly in vivo results show enrichment in CD44+ cells with Paclitaxel (49% CD44+ in control vs 88% CD44+ with treatment). Analysis of genes associated with stemness showed upregulation of Klf-4, Nanog ALDH1, and MyD88 in the cultures treated with Paclitaxel compared to control. Conclusion: We demonstrate that Paclitaxel selectively induce cell death in CD44-/MyD88- EOC cells but has a pro-survival effect and enhances self-renewal in the pleuripotent and chemoresistant CD44+/MyD88+ EOC stem cells. Based on these data, we propose that the mode of management for EOC patients should take into consideration the tumor's molecular phenotype. Our results highlight the need to identify patients that should not receive Paclitaxel - not only because they are resistant, but more importantly, because it can enrich for the more aggressive cancer stem cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3471. doi:1538-7445.AM2012-3471

Constitutive proteasomal degradation of TWIST-1 in epithelial-ovarian cancer stem cells impacts differentiation and metastatic potential

Epithelial-mesenchymal transition (EMT) is a critical process for embryogenesis but is abnormally activated during cancer metastasis and recurrence. This process enables epithelial cancer cells to acquire mobility and traits associated with stemness. It is unknown whether epithelial stem cells or epithelial cancer stem cells are able to undergo EMT, and what molecular mechanism regulates this process in these specific cell types. We found that Epithelial Ovarian Cancer Stem cells (EOC stem cells) are the source of metastatic progenitor cells through a differentiation process involving EMT and Mesenchymal-Epithelial Transition (MET). We demonstrate both in vivo and in vitro the differentiation of EOC stem cells into mesenchymal spheroid-forming cells (MSFCs) and their capacity to initiate an active carcinomatosis. Furthermore, we demonstrate that human EOC stem cells injected i.p in mice are able to form ovarian tumors, suggesting that the EOC stem cells have the ability to “home” to the ovaries and establish tumors. Most interestingly, we found that TWIST1 is constitutively degraded in EOC stem cells, and that the acquisition of TWIST1 requires additional signals that will trigger the differentiation process. These findings are relevant for understanding the differentiation and metastasis process in EOC stem cells.

Distinct subpopulations of epithelial ovarian cancer cells can differentially induce macrophages and T regulatory cells toward a pro-tumor phenotype

PROBLEM

Presence of immune infiltrates in the tumor does not always correlate with an anti-tumoral immune response. We previously identified two subpopulations of epithelial ovarian cancer (EOC) cells with differential cytokine profile. We hypothesize that these two subpopulations of EOC cells may differentially regulate the immune phenotype in the tumor microenvironment and therefore affect the immune response.

METHOD OF STUDY

Macrophages derived from CD14+ monocytes and naive CD4+T cells were treated with conditioned media from two subpopulations of EOC cells. Differentiation markers and phagocytic activity were measured by western blot analysis and flow cytometry. Cytokine levels were quantified using xMAP technology.

RESULTS

Type I EOC cells are able to enhance macrophages' capacity for tumor repair and renewal by enhancing expression of scavenger receptors and by promoting the secretion of cytokines associated with tissue repair. On the other hand, type II EOC cells are able to create a tolerant microenvironment and prevent an immune response by inducing macrophages' to secrete IL-10 and by promoting the generation of T regs.

CONCLUSION

We demonstrate that each ovarian cancer cell subpopulation can induce a unique phenotype of macrophages and T cells, both associated with tumor-supportive function.

Modulation and recruitment of inducible regulatory T cells by first trimester trophoblast cells

PROBLEM  The specialized regulatory T-cells (Treg) population, essential for maternal tolerance of the fetus, performs its suppressive actions in the critical peri-implantation phase of pregnancy. In the present work, we investigated whether trophoblast cells are able to induce Treg recruitment, differentiation, and whether these mechanisms are modified by a bacterial or viral infection. METHOD OF STUDY  Human T-regulatory cells were differentiated from naïve CD45RA(+) CCR7(+) cells obtained from peripheral blood mononuclear cells cultured with IL-2 and TGFβ over 5 days. Induction of iTregs (CD4(+)  Foxp3(+) cells) was evaluated using low serum conditioned media (LSCM), obtained from two first trimester trophoblast cell lines, Swan-71 and HTR8. Coculture experiments were carried out using transwell assays where trophoblast cells were in the absence or presence of PGN, LPS, or Poly [I:C]. Cytokine production was measured by multiplex analysis. RESULTS  Trophoblast cells constitutively secrete high levels of TGFβ and induced a significant increase of Foxp3 expression accompanied by a specific T-reg cytokine profile. Moreover, trophoblast cells were able to recruit iTregs in a specific manner. CONCLUSION  We demonstrate that trophoblast cells have an active role on the recruitment and differentiation of iTregs, therefore, contributing to the process of immune regulation at the placental-maternal interface.

Inhibition of Aurora-A kinase induces cell cycle arrest in epithelial ovarian cancer stem cells by affecting NFĸB pathway

Recurrent ovarian cancer is resistant to conventional chemotherapy. A sub-population of ovarian cancer cells, the epithelial ovarian cancer stem cells (EOC stem cells) have stemness properties, constitutive NFκB activity, and represent the chemoresistant population. Currently, there is no effective treatment that targets these cells. Aurora-A kinase (Aurora-A) is associated with tumor initiation and progression and is overexpressed in numerous malignancies. The aim of this study is to determine the effect of Aurora-A inhibition in EOC stem cells. EOC stem cells were treated with the Aurora-A inhibitor, MK-5108. Cell growth was monitored by Incucyte real-time imaging system, cell viability was measured using the Celltiter 96 assay and cytokine levels were quantified using xMAP technology. The intracellular changes associated with MK-5108 treatment are: (1) polyploidy and cell cycle arrest; (2) inhibition of NFκB activity; (3) decreased cytokine production; and (4) nuclear accumulation of IκBα. Thus, inhibition of Aurora-A decreases cell proliferation in the EOC stem cells by inducing cell cycle arrest and affecting the NFκB pathway. As EOC stem cells represent a source of recurrence and chemoresistance, these results suggest that Aurora-A inhibition may effectively target the cancer stem cell population in ovarian cancer.