Ovarian Cancer Tumor Microenvironment Research Articles

Exploring the clinical value of tumor microenvironment in platinum-resistant ovarian cancer.

Platinum resistance in epithelial ovarian cancer (OvCa) is rising at an alarming rate, with recurrence of chemo-resistant high grade serous OvCa (HGSC) in roughly 75 % of all patients. Additionally, HGSC has an abysmal five-year survival rate, standing at 39 % and 17 % for FIGO stages III and IV, respectively. Herein we review the crucial cellular interactions between HGSC cells and the cellular and non-cellular components of the unique peritoneal tumor microenvironment (TME). We highlight the role of the extracellular matrix (ECM), ascitic fluid as well as the mesothelial cells, tumor associated macrophages, neutrophils, adipocytes and fibroblasts in platinum-resistance. Moreover, we underscore the importance of other immune-cell players in conferring resistance, including natural killer cells, myeloid-derived suppressive cells (MDSCs) and T-regulatory cells. We show the clinical relevance of the key platinum-resistant markers and their correlation with the major pathways perturbed in OvCa. In parallel, we discuss the effect of immunotherapies in re-sensitizing platinum-resistant patients to platinum-based drugs. Through detailed analysis of platinum-resistance in HGSC, we hope to advance the development of more effective therapy options for this aggressive disease.

Possible Role of Metformin as an Immune Modulator in the Tumor Microenvironment of Ovarian Cancer.

Growing evidence suggests that the immune component of the tumor microenvironment (TME) may be highly involved in the progression of high-grade serous ovarian cancer (HGSOC), as an immunosuppressive TME is associated with worse patient outcomes. Due to the poor prognosis of HGSOC, new therapeutic strategies targeting the TME may provide a potential path forward for preventing disease progression to improve patient survival. One such postulated approach is the repurposing of the type 2 diabetes medication, metformin, which has shown promise in reducing HGSOC tumor progression in retrospective epidemiological analyses and through numerous preclinical studies. Despite its potential utility in treating HGSOC, and that the immune TME is considered as a key factor in the disease’s progression, little data has definitively shown the ability of metformin to target this component of the TME. In this brief review, we provide a summary of the current understanding of the effects of metformin on leukocyte function in ovarian cancer and, coupled with data from other related disease states, posit the potential mechanisms by which the drug may enhance the anti-tumorigenic effects of immune cells to improve HGSOC patient survival.

IL-10 Signaling in the Tumor Microenvironment of Ovarian Cancer.

Unlike other malignancies, ovarian cancer (OC) creates a complex tumor microenvironment with distinctive peritoneal ascites consisting of a mixture of several immunosuppressive cells which impair the ability of the patient's immune system to fight the disease. The poor survival rates observed in advanced stage OC patients and the lack of effective conventional therapeutic options have been attributed in large part to the immature dendritic cells (DCs), IL-10 secreting regulatory T cells, tumor-associated macrophages, myeloid-derived suppressor cells, and cancer stem cells that secrete inhibitory cytokines. This review highlights the critical role played by the intraperitoneal presence of IL-10 in the generation of an immunosuppressive tumor microenvironment. Further, the effect of antibody neutralization of IL-10 on the efficacy of DC and chimeric antigen receptor T-cell vaccines will be discussed. Moreover, we will review the influence of IL-10 in the promotion of cancer stemness in concert with the NF-κB signaling pathway with regard to OC progression. Finally, understanding the role of IL-10 and its crosstalk with various cells in the ascitic fluid may contribute to the development of novel immunotherapeutic approaches with the potential to kill drug-resistant OC cells while minimizing toxic side effects.

Modeling the Early Steps of Ovarian Cancer Dissemination in an Organotypic Culture of the Human Peritoneal Cavity.

The majority of ovarian cancer patients present clinically with wide-spread metastases throughout the peritoneal cavity, metastasizing to the mesothelium-lined peritoneum and visceral adipose depots within the abdomen. This unique metastatic tumor microenvironment is comprised of multiple cell types, including mesothelial cells, fibroblasts, adipocytes, macrophages, neutrophils, and T lymphocytes. Modeling advancements, including complex 3D systems and organoids, coupled with 2D cocultures, in vivo mouse models, and ex vivo human tissue cultures have greatly enhanced our understanding of the tumor-stroma interactions that are required for successful metastasis of ovarian cancer cells. However, advanced multifaceted model systems that incorporate frequency and spatial distribution of all cell types present in the tumor microenvironment of ovarian cancer are needed to enhance our knowledge of ovarian cancer biology in order to identify methods for preventing and treating metastatic disease. This review highlights the utility of recently developed modeling approaches, summarizes some of the resulting progress using these techniques, and suggests how these strategies may be implemented to elucidate signaling processes among cell types of the tumor microenvironment that promote ovarian cancer metastasis.

How Autophagy Shapes the Tumor Microenvironment in Ovarian Cancer.

Ovarian cancer (OC) is characterized by a high mortality rate due to the late diagnosis and the elevated metastatic potential. Autophagy, a lysosomal-driven catabolic process, contributes to the macromolecular turnover, cell homeostasis, and survival, and as such, it represents a pathway targetable for anti-cancer therapies. It is now recognized that the vascularization and the cellular composition of the tumor microenvironment influence the development and progression of OC by controlling the availability of nutrients, oxygen, growth factors, and inflammatory and immune-regulatory soluble factors that ultimately impinge on autophagy regulation in cancer cells. An increasing body of evidence indicates that OC carcinogenesis is associated, at least in the early stages, to insufficient autophagy. On the other hand, when the tumor is already established, autophagy activation provides a survival advantage to the cancer cells that face metabolic stress and protects from the macromolecules and organelles damages induced by chemo- and radiotherapy. Additionally, upregulation of autophagy may lead cancer cells to a non-proliferative dormant state that protects the cells from toxic injuries while preserving their stem-like properties. Further to complicate the picture, autophagy is deregulated also in stromal cells. Thus, changes in the tumor microenvironment reflect on the metabolic crosstalk between cancer and stromal cells impacting on their autophagy levels and, consequently, on cancer progression. Here, we present a brief overview of the role of autophagy in OC hallmarks, including tumor dormancy, chemoresistance, metastasis, and cell metabolism, with an emphasis on the bidirectional metabolic crosstalk between cancer cells and stromal cells in shaping the OC microenvironment.

Tumor derived UBR5 promotes ovarian cancer growth and metastasis through inducing immunosuppressive macrophages

Immunosuppressive tumor microenvironment (TME) and ascites-derived spheroids in ovarian cancer (OC) facilitate tumor growth and progression, and also pose major obstacles for cancer therapy. The molecular pathways involved in the OC-TME interactions, how the crosstalk impinges on OC aggression and chemoresistance are not well-characterized. Here, we demonstrate that tumor-derived UBR5, an E3 ligase overexpressed in human OC associated with poor prognosis, is essential for OC progression principally by promoting tumor-associated macrophage recruitment and activation via key chemokines and cytokines. UBR5 is also required to sustain cell-intrinsic β-catenin-mediated signaling to promote cellular adhesion/colonization and organoid formation by controlling the p53 protein level. OC-specific targeting of UBR5 strongly augments the survival benefit of conventional chemotherapy and immunotherapies. This work provides mechanistic insights into the novel oncogene-like functions of UBR5 in regulating the OC-TME crosstalk and suggests that UBR5 is a potential therapeutic target in OC treatment for modulating the TME and cancer stemness.

The Capacity of the Ovarian Cancer Tumor Microenvironment to Integrate Inflammation Signaling Conveys a Shorter Disease-free Interval.

Ovarian cancer has one of the highest deaths to incidence ratios across all cancers. Initial chemotherapy is effective, but most patients develop chemoresistant disease. Mechanisms driving clinical chemo-response or -resistance are not well-understood. However, achieving optimal surgical cytoreduction improves survival, and cytoreduction is improved by neoadjuvant chemotherapy (NACT). NACT offers a window to profile pre- versus post-NACT tumors, which we used to identify chemotherapy-induced changes to the tumor microenvironment. We obtained matched pre- and post-NACT archival tumor tissues from patients with high-grade serous ovarian cancer (patient, n = 6). We measured mRNA levels of 770 genes (756 genes/14 housekeeping genes, NanoString Technologies), and performed reverse phase protein array (RPPA) on a subset of matched tumors. We examined cytokine levels in pre-NACT ascites samples (n = 39) by ELISAs. A tissue microarray with 128 annotated ovarian tumors expanded the transcriptional, RPPA, and cytokine data by multispectral IHC. The most upregulated gene post-NACT was IL6 (16.79-fold). RPPA data were concordant with mRNA, consistent with elevated immune infiltration. Elevated IL6 in pre-NACT ascites specimens correlated with a shorter time to recurrence. Integrating NanoString (n = 12), RPPA (n = 4), and cytokine (n = 39) studies identified an activated inflammatory signaling network and induced IL6 and IER3 (immediate early response 3) post-NACT, associated with poor chemo-response and time to recurrence. Multiomics profiling of ovarian tumor samples pre- and post-NACT provides unique insight into chemo-induced changes to the tumor microenvironment. We identified a novel IL6/IER3 signaling axis that may drive chemoresistance and disease recurrence.

Manipulating the Wnt/β-catenin signaling pathway to promote anti-tumor immune infiltration into the TME to sensitize ovarian cancer to ICB therapy

ObjectiveImmune checkpoint blockade (ICB) therapy shows limited efficacy in ovarian cancers due to the “cold” immune phenotype surrounding these tumors. Previous studies have shown that in ovarian cancer Wnt/β-catenin pathway activation contributes to this immune phenotype. Here, we evaluated the anti-tumor and immune-enhancing properties of the Wnt inhibitor, CGX-1321, used alone or in combination with either DKN-01 or anti-PD-1 therapy, in pre-clinical ovarian cancer models. MethodsThe parental ID8 murine ovarian cancer model harboring a knock-out of p53 (ID8p53−/−) and MISIIR-Tag spontaneous ovarian cancer models were used to test the effects of CGX-1321 alone or in combination therapies on tumor burden and immune cell landscape in the tumor microenvironment (TME). Flow cytometry and NanoString analyses were used to characterize the changes in tumor-intrinsic signaling and immune-related profiles in the TME of ovarian cancer in response to treatments. ResultsCGX-1321 significantly reduced tumor burden and constrained tumor progression in the ID8p53−/− and MISIIR-Tag models. Furthermore, CGX-1321 increased infiltrating CD8+ T cells in the TME. Combining CGX-1321 with either DKN-01 or anti-PD-1 therapy also decreased tumor burden and increased CD8+ T cell infiltration in the omentum TME but did not do so to a greater extent that CGX-1321 monotherapy. ConclusionsCGX-1321 significantly reduced tumor burden and enhanced CD8+ T cell levels in ovarian cancer, nevertheless the addition of DKN-01 or anti-PD-1 therapies did not enhance these effects of CGX-1321. Further investigation is needed to determine if CGX-1321 + DKN-01 combination treatment sensitizes pre-clinical ovarian cancer to ICB therapy.

Distribution of novel immune-checkpoint targets in ovarian cancer tumor microenvironment: A dynamic landscape.

BackgroundThe disappointing activity of single agent immune-checkpoint inhibitors in epitherlial ovarian cancer (EOC) has been attributed in part to its unique tumor microenvironment (TME). IDO, PDL1, LAG3 and TIM3 have been implicated in the immunotolerance of EOC. We investigated the expression of these co-regulators, their change with neoadjuvant chemotherapy (NACT), and their association with outcome. MethodWe identified 98 patients with EOC treated with NACT and performed IDO, PDL1, LAG3 and TIM3 immunohistochemistry on samples obtained before and after NACT. The cut-off threshold to consider a positive sample was set at 5%. ResultsIn our cohort, TIM3 was the most prevalent co-regulator, with more than 75% of the samples being TIM3 positive. In comparison, only 22%, 28% and 17% of the samples were considered IDO, PDL1 and LAG3 positive. More than half of ovarian tumors expressed 2, 3 or even all 4 co-inhibitory molecules. However, biomarkers were not correlated with each other. NACT had a marked impact on immune co-regulator expression with over 70% of patients showing a change in biomarker status from negative to positive or vice versa. There was no significant difference in the pattern of co-regulator expression between platinum-sensitive and resistant patients. Co-expression of multiple inhibitory molecules did not appear to affect overall and progression-free survival. ConclusionTIM3 is the most abundant co-inhibitory molecule in OC and may represent an attractive target. In addition, OC frequently co-expressed 2 or more markers supporting ICI combinatorial approaches. Finally, NACT significantly altered the expression of immunosuppressive molecules suggesting that the choice of ICI combinations should be adapted to the composition of the post-NACT immune TME.

Modulation of Immune Infiltration of Ovarian Cancer Tumor Microenvironment by Specific Subpopulations of Fibroblasts.

Simple SummaryThe ovarian cancer tumor microenvironment is made up of ovarian cancer cells along with a milieu of proteins and normal cells, including fibroblasts, immune cells, endothelial cells, pericytes and adipocytes. The noncancer components also play an important role in determining the fate of the tumor and exhibit a lot of heterogeneity. In this study, we have used a deconvolution algorithm to identify four different fibroblast subpopulations and multiple immune cell types, from bulk RNA-seq data of ovarian cancer primary tumors, metastases and normal omentum. We report the prevalence of specific fibroblast subtypes that determine the tumor-immune microenvironment. Our study can potentially help provide a template for identification of potential combination therapies to enhance the efficacy of ovarian cancer immunotherapies.Tumor immune infiltration plays a key role in the progression of solid tumors, including ovarian cancer, and immunotherapies are rapidly emerging as effective treatment modalities. However, the role of cancer-associated fibroblasts (CAFs), a predominant stromal constituent, in determining the tumor-immune microenvironment and modulating efficacy of immunotherapies remains poorly understood. We have conducted an extensive bioinformatic analysis of our and other publicly available ovarian cancer datasets (GSE137237, GSE132289 and GSE71340), to determine the correlation of fibroblast subtypes within the tumor microenvironment (TME) with the characteristics of tumor-immune infiltration. We identified (1) four functional modules of CAFs in ovarian cancer that are associated with the TME and metastasis of ovarian cancer, (2) immune-suppressive function of the collagen 1,3,5-expressing CAFs in primary ovarian cancer and omental metastases, and (3) consistent positive correlations between the functional modules of CAFs with anti-immune response genes and negative correlation with pro-immune response genes. Our study identifies a specific fibroblast subtype, fibroblast functional module (FFM)2, in the ovarian cancer tumor microenvironment that can potentially modulate a tumor-promoting immune microenvironment, which may be detrimental toward the effectiveness of ovarian cancer immunotherapies.

Nanoparticles in precision medicine for ovarian cancer: From chemotherapy to immunotherapy.

Ovarian cancer is the most common cause of death among gynecological malignancies globally. Ovarian cancer treatment integrates debulking surgery and systemic therapy. Genomic and proteomic analyses have shown that ovarian cancer is heterogeneous with unique molecular characteristics that may facilitate the development of systemic targeted chemotherapeutic and immunotherapeutic precision medicines. However, despite their advantages, these therapies have some limitations. Chemotherapy has drawbacks such as drug resistance and high toxicity due to nonspecific tumor targeting; the targeted versions have limited utility and off-target side effects. Immunotherapy has a low response rate due to the intrinsically immunosuppressive tumor microenvironment in ovarian cancer. Nanotechnology-based drug delivery systems have the potential to overcome such limitations. Various nanoparticles have been developed for controlled drug delivery to ovarian cancer. In this review, we summarize the application of nanotechnology in ovarian cancer systemic therapy including nanoformulations in the market and in clinical trials, as well as the recent nanoparticle research therapeutic strategies. The potential and challenges of nanoparticles in ovarian cancer treatment are also discussed.

Investigating the impact of neuropillin-1 on the interaction of carcinoma-associated mesenchymal stem cells and the immune tumor microenvironment in ovarian cancer

Objective: Ovarian cancer exists within a complex tumor microenvironment critical to supporting tumor survival, growth, and metastasis. Within the tumor microenvironment, tumor-stromal-immune cell interactions create an immunosuppressive environment and facilitate treatment resistance. Antitumor T cells are associated with improved patient survival, while immunosuppressive cells T regulatory cells (Tregs) are associated with decreased survival. Previous data demonstrate that Tregs within ovarian cancers have increased neuropilin-1 (NRP-1), a cell surface protein that enhances Treg function and stability.

Three Genes Predict Prognosis in Microenvironment of Ovarian Cancer.

Ovarian cancer (OC) is the deadliest gynecological cancer in women. Immune cell infiltration has a critical role in regulating carcinogenesis and prognosis in OC. To identify prognostic genes relevant to the tumor microenvironment in OC, we investigated the association between OC and gene expression profiles. Results obtained with the ESTIMATE R tool showed that immune score and stromal score were correlated with lymphatic invasion, and high immune score predicted a favorable prognosis. A total of 342 common differentially expressed genes were identified according to the two scores; these genes were mainly involved in immune response, extracellular region, and serine-type endopeptidase activity. Three immune-related prognostic genes were selected by univariate and multivariate Cox regression analysis. We further established a prognostic model and validated the prognostic value of three hub genes in different databases; our results showed that this model could accurately predict survival and evaluate prognosis independent of clinical characteristics. Three hub genes have prognostic value in OC. TIMER analysis revealed that the three genes were correlated with different immune cells. Low levels of macrophage infiltration and high levels of CD4+ T cell infiltration were associated with favorable survival outcomes. Arm-level gain of GYPC was correlated with neutrophils and dendritic cells. These findings indicate that CXCR4, GYPC, and MMP12 modulate prognosis via effects on the infiltration of immune cells. Thus, these genes represent potential targets for immune therapy in OC.

Characterizing the Tumor Microenvironment of Metastatic Ovarian Cancer by Single Cell Transcriptomics

Epithelial ovarian cancer is a highly heterogenous, metastatic and lethal disease. The presence of CD8+ T cells within ovarian tumors is positively associated with overall patient survival. Determining if a patient has T cells that respond to immunotherapies, their characteristics and how they can be manipulated to target cancer cells is an area of intense investigation in cancer therapy. This study determines the cellular composition and the transcriptional state of immune cells in solid metastatic ovarian cancer tumor samples from patients using single cell RNA sequencing (scRNA-seq). Hierarchical clustering stratified our patient samples into 2 main groups: 1) a high T cell infiltration (high Tinf ) group and 2) a low T cell infiltration (low Tinf) group. To assess the immune response in these patient samples, we performed an unsupervised clustering of the T cell population in each group. The T cell population clustered into 4 and 3 subpopulations in the high Tinf and low Tinf group respectively. A granulysin-expressing T cell cluster was identified and unique to the High Tinf group. Interestingly, although both groups had resident memory CD8+ T (CD8+ Trm) cells, only the CD8+ Trm cells in the high Tinf group expressed TOX , a recently described transcription factor that confers longevity to T cells within immunosuppressive environments such as cancer. Along with TOX+ CD8+ Trm cells, we found a unique plasmablast cluster and an IRF8+ macrophage cluster unique to the high Tinf group. Our comprehensive scRNA-seq study provides important insights in elucidating the immune response within ovarian tumors.

Tumor Microenvironment in Ovarian Cancer: Function and Therapeutic Strategy.

Ovarian cancer is one of the leading causes of death in patients with gynecological malignancy. Despite optimal cytoreductive surgery and platinum-based chemotherapy, ovarian cancer disseminates and relapses frequently, with poor prognosis. Hence, it is urgent to find new targeted therapies for ovarian cancer. Recently, the tumor microenvironment has been reported to play a vital role in the tumorigenesis of ovarian cancer, especially with discoveries from genome-, transcriptome- and proteome-wide studies; thus tumor microenvironment may present potential therapeutic target for ovarian cancer. Here, we review the interactions between the tumor microenvironment and ovarian cancer and various therapies targeting the tumor environment.

Carcinoma-Associated Mesenchymal Stem Cells Promote Chemoresistance in Ovarian Cancer Stem Cells via PDGF Signaling.

Within the ovarian cancer tumor microenvironment, cancer stem-like cells (CSC) interact with carcinoma associated mesenchymal stem/stromal cells (CA-MSC) through multiple secreted cytokines and growth factors. These paracrine interactions have been revealed to cause enrichment of CSC and their chemoprotection; however, it is still not known if platelet-derived growth factor (PDGF) signaling is involved in facilitating these responses. In order to probe this undiscovered bidirectional communication, we created a model of ovarian malignant ascites in the three-dimensional (3D) hanging drop heterospheroid array, with CSC and CA-MSC. We hypothesized that PDGF secretion by CA-MSC increases self-renewal, migration, epithelial to mesenchymal transition (EMT) and chemoresistance in ovarian CSC. Our results indicate that PDGF signaling in the CSC-MSC heterospheroids significantly increased stemness, metastatic potential and chemoresistance of CSC. Knockdown of PDGFB in MSC resulted in abrogation of these phenotypes in the heterospheroids. Our studies also reveal a cross-talk between PDGF and Hedgehog signaling in ovarian cancer. Overall, our data suggest that when the stromal signaling via PDGF to ovarian CSC is blocked in addition to chemotherapy pressure, the tumor cells are significantly more sensitive to chemotherapy. Our results emphasize the importance of disrupting the signals from the microenvironment to the tumor cells, in order to improve response rates. These findings may lead to the development of combination therapies targeting stromal signaling (such as PDGF and Hedgehog) that can abrogate the tumorigenic, metastatic and platinum resistant phenotypes of ovarian CSC through additional investigations.

Abstract IA15: Modeling the tumor microenvironment of high-grade serous ovarian cancer

Abstract Using biopsies of metastatic high-grade serous ovarian cancer (HGSOC) that ranged from minimal to extensive disease, we defined RNA and protein profiles that evolved with changes in cellularity, architecture, and tissue modulus. This gave new insights into host response to cancer as well as leukocyte, cytokine, and matrisome regulation in the tumor microenvironment (TME). Although we had studied a single metastatic site, we identified an extracellular matrix (ECM) gene expression signature, which we named the matrix index, that significantly associated with increased stiffness and disease score. High matrix index distinguished patients with a shorter overall survival in ovarian and twelve other primary cancers, suggesting a common matrix response to human cancer. We used this “deconstruction” analysis of a human TME to build 3D multicellular cultures of human HGSOC cells, primary omental fibroblasts, mesothelial cells, and adipocytes. These cultures reproduce the prognostic matrix index signature, as confirmed by RNAseq and immunofluorescence, of the human cancer biopsies. Using these 3D models, we can study regulation of the matrisome and cancer cell invasion. Similarly, we have conducted multilevel analysis of orthotopic mouse models of HGSOC metastases with relevant oncogenic mutations. This analysis identified significant correlations between the transcriptome, host cell infiltrates, immune response, matrisome, vasculature, and tissue modulus of mouse and human TMEs, with several stromal and malignant cell targets in common. However, each mouse model showed distinct differences and potential vulnerabilities that enabled us to predict response to chemotherapy and an anti-IL-6 antibody. The transcriptional profiles of the mouse tumors that differed in chemotherapy response were able to classify chemotherapy-sensitive and -refractory patient tumors. We believe that these 3D human and mouse models provide useful preclinical tools and may help identify subgroups of HGSOC patients most likely to respond to specific therapies. Citation Format: Frances Balkwill. Modeling the tumor microenvironment of high-grade serous 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 IA15.

Abstract B71: Investigating the role of PAX8 in modulating the tumor microenvironment of high-grade serous ovarian cancer

Abstract High-grade serous ovarian cancer (HGSOC), the most common and lethal form of ovarian cancer, is a highly heterogeneous disease. HGSOC is rarely detected early, and likely arises from the fimbriated end of the fallopian tube epithelium (FTE), and in some cases, the ovarian surface epithelium (OSE). PAX8 is a commonly used biomarker for ovarian serous tumors and is expressed in 80-96% of HGSOC. Although the OSE does not express PAX8, murine models of HGSOC derived from the OSE acquire PAX8, suggesting that it is not only a marker of Müllerian origin, but also an essential part of HGSOC progression, potentially from both the OSE and FTE. Previously, we showed that PAX8 deletion by CRISPR and shRNA in HGSOC cell lines caused apoptosis and reduced cell migration and invasion. We performed secretome analysis of PAX8 deleted cells and found a reduction of the extracellular matrix (ECM) component fibronectin. This finding was validated by immunoblotting and immunofluorescence in PAX8 deleted HGSOC cells. We have generated several murine FTE-derived tumor models (PTEN/KRAS/p53 alterations) and knocked down PAX8 in these models. These syngeneic fallopian tube-derived tumor models will be allografted into immune intact FVB mice and the tumors will be used to determine if PAX8 loss impacts immune cell infiltration via changes in ECM. Additionally, we are using a novel high-throughput screening (HTS) assay to identify small molecules that can function to inhibit PAX8 promoter activation and lead to reduced PAX8 expression. We have generated a stable cell line using murine FTE cells expressing the PAX8 promoter-luciferase reporter, which will be used to screen a library of FDA-approved drugs (Prestwick Library, ca. 1,200 members). Overall, this study would help us to validate PAX8 as a regulator of ECM deposition in the tumor microenvironment and identify an effective drug for treatment of ovarian cancers derived from both the FTE and OSE. Citation Format: Amrita Salvi, Laura Hardy, Samantha Watry, Melissa Pergande, Stephanie M. Cologna, Joanna E. Burdette. Investigating the role of PAX8 in modulating the tumor microenvironment of high-grade serous 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 B71.

Abstract IA21: MUC16-directed immunotherapy for ovarian cancer

Abstract Despite recent setbacks in the clinical development of immunotherapy for gynecologic malignancies, the promise of durable responses with this form of treatment has led to a redoubling of our efforts to understand and develop new immunotherapeutic modalities. Some of the reasons behind the relative lack of success of immunotherapy in ovarian cancer include low tumor antigenic burden; a hostile tumor microenvironment (TME) consisting of physical barriers to immune infiltration; suppressive ligands, cytokines, chemokines, and other immunosuppressive cellular elements. There are ongoing efforts to overcome many of these limitations simultaneously. For instance, several clinical trials are exploring the combination of immune checkpoint blockade with chemotherapy, poly (ADP-ribose) polymerase (PARP) inhibitors, or both in an attempt to increase tumor antigenic burden. Other approaches are centered around targeting known tumor-associated antigens such as MUC16. MUC16 is amplified in 5-10% of ovarian cancers. The predominant extracellular portion of MUC16 is cleaved and secreted (referred to as CA-125), although a significant portion of the antigen is retained on the surface of the tumor (referred to as MUC16ecto). We have developed a variety of MUC16ecto- directed therapies, including chimeric antigen receptor (CAR) T-cells and bispecific T-cell engager cells (BiTEs). Targeting MUC16ecto solves the problem of low tumor mutational burden in ovarian cancer, but further optimizations are required to overcome the immunosuppressive TME. For our CAR T-cell therapy, we devised and evaluated three separate approaches to overcome the TME in ovarian cancer. MUC16ecto-directed CAR T-cells modified to secrete interleukin-12 (IL-12) showed superior efficacy in advanced syngeneic and xenograft murine models of metastatic ovarian cancer. We found that autocrine and paracrine activity of IL-12 potentiated the activity of these CAR T-cells and mediated resistance to PD-L1 suppression. Furthermore, we found that secretion of IL-12 in the TME promoted differentiation of proinflammatory tumor-associated macrophages and led to the deletion of other suppressive macrophages in the TME. Similarly, MUC16ecto-directed CAR T-cells modified to secrete interleukin-18 (IL-18) significantly improved survival in low and high tumor burden syngeneic models of metastatic ovarian cancer. We also evaluated CAR T-cells engineered to secrete anti-PD-1 blocking single-chain variable fragments (scFv) and showed that this approach significantly improved efficacy in relevant preclinical models of metastatic ovarian cancer. Furthermore, this approach fostered CAR T-cell persistence leading to resistance to tumor rechallenge. Unsurprisingly, using CAR T-cells as a delivery vehicle for delivery of immune checkpoint blockade promoted bystander effects on endogenous immune cells and mitigated systemic anti-PD-1 leak. We next evaluated MUC16ecto-specific BITEs and found a significant reduction in tumor burden in xenogeneic models of metastatic ovarian cancer. Adjunctive therapies to augment our MUC16ecto-specific BiTEs are currently in testing, along with other MUC16-directed immunotherapeutic strategies. Citation Format: Oladapo O. Yeku, Sarwish Rafiq, Mythili Koneru, Terence J. Purdon, Mei Song, Pei Wang, Ronald Hendrickson, Renier J. Brentjens, David Spriggs. MUC16-directed immunotherapy for 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 IA21.

Signaling within the epithelial ovarian cancer tumor microenvironment: the challenge of tumor heterogeneity.

Epithelial ovarian cancer (EOC) is a leading cause of cancer death in women. Standard of care treatment has remained platinum-containing cytotoxic chemotherapy for over three decades. Among the central challenges in treating ovarian CA are disease recurrence and the development of chemoresistance. Survival is uniformly poor for patients with chemoresistant recurrent disease and effective therapeutic options are limited. As such, delineating the mechanisms of chemoresistance and developing targeted therapies to prevent chemoresistance from occurring are of vital importance to improving survival for patients with EOC. Attempts to characterize mechanisms of chemoresistance have implicated numerous cellular pathways, but a rift remains between pre-clinical findings and translation to improving patient survival. More recently, the interplay among different cell types within the tumor microenvironment has become central to understanding how chemoresistance may develop and may be sustained. An improved understanding of how tumor cell-intrinsic and -extrinsic pathways converge during the development of chemoresistance may improve the likelihood of successful clinical translation. This review focuses on the roles of the EOC tumor microenvironment and tumor cell heterogeneity in the development of chemoresistance. We review recent studies into mechanisms of chemoresistance as they relate to tumor microenvironment and development of novel therapeutic approaches that exploit these mechanisms to prevent or reverse chemoresistance. This review attempts to cast these latest discoveries in a clinical context by summarizing trends in ongoing clinical trials for patients with EOC.