Barbara C. Vanderhyden

Cancer genetics and response to oncolytic virus treatment for ovarian cancer

Ovarian cancers (OCs) are often defined as poorly immunogenic tumors that have low response rates to current immunotherapies and frequently develop resistance to chemotherapies. Oncolytic viruses (OVs) are an emerging therapeutic approach that is favored due to its multifactorial mechanism of action; OVs aim to enhance immune cell recovery and infiltration into the tumor, in addition to assisting the immune system to identify and target evasive tumors. While many different OVs have been studied, this review focuses on the four that have been extensively tested in preclinical models and clinical trials with OC patients: vaccinia viruses, vesicular stomatitis virus, herpes simplex 1, and adenoviruses. We will first explore how these viruses have been developed, modified and tested as monotherapies in OCs, with limited success. The various combinatorial approaches involving OVs that are currently being investigated to improve the outcomes for OC patients will then be addressed. Attention will be given to how the genetics of OC cells may influence response to OVs and how that has led to genetic modifications of OVs that improve the cancer specificity and efficacy of these therapies.

Specific Genetic Mutations Impact Chemotherapy Resistance and Therapeutic Efficacy of Oncolytic Viruses in Ovarian Cancer

Abstract Epithelial ovarian cancer (EOC) is the most lethal gynecologic cancer, and those affected are in urgent need of new therapeutic strategies. Standard treatment is surgery followed by taxane- and platinum-based chemotherapy. However, the rate of relapse is high, and the 5-year survival is only 45%. Oncolytic viruses (OV) are a promising approach to EOC therapy through remodeling the immune composition of the tumor microenvironment. Treatment response in EOC tumors can differ based on the presence of key tumorigenic mutations. This study evaluated the impact of specific tumor mutations on the response to the current standard-of-care carboplatin, two promising OV candidates VSVΔM51 and MG1, an infected cell vaccine (ICV-MG1) regimen, and the antiangiogenic drug Fc3TSR. Mice with tumors harboring constitutive K-Ras activation showed an enhanced response to carboplatin and VSVΔM51 treatment. Additionally, VSVΔM51 treatment prolonged survival of syngeneic mice bearing tumors with mutations in Pten and Kras, Pten and Trp53, or Trp53 and Brca2 with increased activation of CD4+ and CD8+ T lymphocytes in the peritoneal tumor microenvironment. To enhance OV potency, an MG1-based infected cell vaccine inducing the expression of IL21 or IL15 + IL21 was developed and found to enable strong and long-lasting antitumoral immunity in two carboplatin-refractory syngeneic models, ID8-Trp53−/− and STOSE. VSVΔM51 combined with the antiangiogenic Fc3TSR enhanced efficacy in the ID8 model. In summary, OV-based immunotherapy has shown promise in diverse murine models of EOC-bearing clinically relevant mutations, thus laying the foundation for developing new OV-based strategies to target a large spectrum of EOC genotypes.

Loss of LATS1 and LATS2 promotes ovarian tumor formation by enhancing AKT activity and PD-L1 expression

High-grade serous ovarian cancer (HGSOC) is the deadliest and most common subtype of ovarian cancer. Unfortunately, most patients develop recurrence and, ultimately, resistance to standard platinum chemotherapy. Large tumor suppressors LATS1 and LATS2, the core Hippo signaling kinases, have been implicated in various cancer types, including ovarian cancer. The mechanism by which LATS1/2 suppresses ovarian cancer progression is currently elusive, but the expression of LATS1/2 is frequently reduced or lost in these cancers. In this study, we demonstrate that the inactivation of LATS1/2 is sufficient to transform normal mouse ovarian epithelium into tumorigenic cells associated with increased cell proliferation, invasion, and stemness and epithelial-mesenchymal transition (EMT) characteristics. The knockout of Lats1/2 in the epithelial cells also leads to higher expression levels of the immune checkpoint molecule PD-L1, suggesting a regulatory role of LATS1/2 in modulating immune responses and immune evasion. In addition to the loss of LATS1/2 activating the downstream transcriptional coactivators YAP and TAZ, PI3K-AKT activity was also increased, likely contributing to enhanced tumor proliferation and survival. The stimulatory effect of Lats1/2 knockout on cell proliferation can be partially reversed by treatment with the AKT inhibitor MK2206. Treatment with verteporfin, a potent inhibitor of YAP/TAZ, decreases ovarian tumor progression and reduces the activated AKT in the tumors. In summary, this study uncovers several biological mechanisms for the initiation of HGSOC and identifies LATS1/2 as potential prognostic indicators and therapeutic targets.

Mesenchymal ovarian cancer cells promote CD8+ T cell exhaustion through the LGALS3-LAG3 axis

AbstractCancer cells often metastasize by undergoing an epithelial-mesenchymal transition (EMT). Although abundance of CD8+ T-cells in the tumor microenvironment correlates with improved survival, mesenchymal cancer cells acquire greater resistance to antitumor immunity in some cancers. We hypothesized the EMT modulates the immune response to ovarian cancer. Here we show that cancer cells from infiltrated/inflamed tumors possess more mesenchymal cells, than excluded and desert tumors. We also noted high expression of LGALS3 is associated with EMT in vivo, a finding validated with in vitro EMT models. Dissecting the cellular communications among populations in the tumor revealed that mesenchymal cancer cells in infiltrated tumors communicate through LGALS3 to LAG3 receptor expressed by CD8+ T cells. We found CD8+ T cells express high levels of LAG3, a marker of T cell exhaustion. The results indicate that EMT in ovarian cancer cells promotes interactions between cancer cells and T cells through the LGALS3 - LAG3 axis, which could increase T cell exhaustion in infiltrated tumors, dampening antitumor immunity.

LY75 Suppression in Mesenchymal Epithelial Ovarian Cancer Cells Generates a Stable Hybrid EOC Cellular Phenotype, Associated with Enhanced Tumor Initiation, Spreading and Resistance to Treatment in Orthotopic Xenograft Mouse Model

The implications of the epithelial–mesenchymal transition (EMT) mechanisms in the initiation and progression of epithelial ovarian cancer (EOC) remain poorly understood. We have previously shown that suppression of the antigen receptor LY75 directs mesenchymal–epithelial transition (MET) in EOC cell lines with the mesenchymal phenotype, associated with the loss of Wnt/β-catenin signaling activity. In the present study, we used the LY75-mediated modulation of EMT in EOC cells as a model in order to investigate in vivo the specific role of EOC cells, with an epithelial (E), mesenchymal (M) or mixed epithelial plus mesenchymal (E+M) phenotype, in EOC initiation, dissemination and treatment response, following intra-bursal (IB) injections of SKOV3-M (control), SKOV3-E (Ly75KD) and a mixed population of SKOV3-E+M cells, into severe combined immunodeficiency (SCID) mice. We found that the IB-injected SKOV3-E cells displayed considerably higher metastatic potential and resistance to treatment as compared to the SKOV3-M cells, due to the acquisition of a Ly75KD-mediated hybrid phenotype and stemness characteristics. We also confirmed in vivo that the LY75 depletion directs suppression of the Wnt/β-catenin pathway in EOC cells, suggestive of a protective role of this pathway in EOC etiology. Moreover, our data raise concerns regarding the use of LY75-targeted vaccines for dendritic-cell EOC immunotherapy, due to the possible occurrence of undesirable side effects.

Metformin Abrogates Age-Associated Ovarian Fibrosis

Abstract Purpose: The ovarian cancer risk factors of age and ovulation are curious because ovarian cancer incidence increases in postmenopausal women, long after ovulations have ceased. To determine how age and ovulation underlie ovarian cancer risk, we assessed the effects of these risk factors on the ovarian microenvironment. Experimental Design: Aged C57/lcrfa mice (0–33 months old) were generated to assess the aged ovarian microenvironment. To expand our findings into human aging, we assembled a cohort of normal human ovaries (n = 18, 21–71 years old). To validate our findings, an independent cohort of normal human ovaries was assembled (n = 9, 41–82 years old). Results: We first validated the presence of age-associated murine ovarian fibrosis. Using interdisciplinary methodologies, we provide novel evidence that ovarian fibrosis also develops in human postmenopausal ovaries across two independent cohorts (n = 27). Fibrotic ovaries have an increased CD206+:CD68+ cell ratio, CD8+ T-cell infiltration, and profibrotic DPP4+αSMA+ fibroblasts. Metformin use was associated with attenuated CD8+ T-cell infiltration and reduced CD206+:CD68+ cell ratio. Conclusions: These data support a novel hypothesis that unifies the primary nonhereditary ovarian cancer risk factors through the development of ovarian fibrosis and the formation of a premetastatic niche, and suggests a potential use for metformin in ovarian cancer prophylaxis. See related commentary by Madariaga et al., p. 523

The Tumor Immune Profile of Murine Ovarian Cancer Models: An Essential Tool for Ovarian Cancer Immunotherapy Research

Epithelial ovarian cancer (EOC) is the most lethal gynecologic cancer with an imperative need for new treatments. Immunotherapy has had marked success in some cancer types; however, clinical trials studying the efficacy of immune checkpoint inhibitors for the treatment of EOC benefited less than 15% of patients. Given that EOC develops from multiple tissues in the reproductive system and metastasizes widely throughout the peritoneal cavity, responses to immunotherapy are likely hindered by heterogeneous tumor microenvironments (TME) containing a variety of immune profiles. To fully characterize and compare syngeneic model systems that may reflect this diversity, we determined the immunogenicity of six ovarian tumor models in vivo, the T and myeloid profile of orthotopic tumors and the immune composition and cytokine profile of ascites, by single-cell RNA sequencing, flow cytometry, and IHC. The selected models reflect the different cellular origins of EOC (ovarian and fallopian tube epithelium) and harbor mutations relevant to human disease, including Tp53 mutation, PTEN suppression, and constitutive KRAS activation. ID8-p53−/− and ID8-C3 tumors were most highly infiltrated by T cells, whereas STOSE and MOE-PTEN/KRAS tumors were primarily infiltrated by tumor-associated macrophages and were unique in MHC class I and II expression. MOE-PTEN/KRAS tumors were capable of forming T-cell clusters. This panel of well-defined murine EOC models reflects some of the heterogeneity found in human disease and can serve as a valuable resource for studies that aim to test immunotherapies, explore the mechanisms of immune response to therapy, and guide selection of treatments for patient populations. Significance: This study highlights the main differences in the immunogenicity and immune composition found in six different models of orthotopic ovarian cancer as an essential tool for future preclinical investigations of cancer immunotherapy.

Comparative analysis of syngeneic mouse models of high-grade serous ovarian cancer

Abstract Ovarian cancers exhibit high rates of recurrence and poor treatment response. Preclinical models that recapitulate human disease are critical to develop new therapeutic approaches. Syngeneic mouse models allow for the generation of tumours comprising the full repertoire of non-malignant cell types but have expanded in number, varying in the cell type of origin, method for transformation, and ultimately, the properties of the tumours they produce. Here we have performed a comparative analysis of high-grade serous ovarian cancer models based on transcriptomic profiling of 22 cell line models, and intrabursal and intraperitoneal tumours from 12. Among cell lines, we identify distinct signalling activity, such as elevated inflammatory signalling in STOSE and OVE16 models, and MAPK/ERK signalling in ID8 and OVE4 models; metabolic differences, such as reduced glycolysis-associated expression in several engineered ID8 subclones; and relevant functional properties, including differences in EMT activation, PD-L1 and MHC class I expression, and predicted chemosensitivity. Among tumour samples, we observe increased variability and stromal content among intrabursal tumours. Finally, we predict differences in the microenvironment of ID8 models engineered with clinically relevant mutations. We anticipate that this work will serve as a valuable resource, providing new insight to help select models for specific experimental objectives.