Karthikeyan Mythreye

Activin levels correlate with lymphocytic infiltration in epithelial ovarian cancer

AbstractObjectiveThe TGF‐β superfamily member activin, a dimer of the gene products of INHBA and/or INHBB, has been implicated in immune cell maturation and recruitment, but its immune impact within epithelial ovarian cancer (EOC) is not well characterized. We sought to explore differences in activin (INHBA/ Inhibin‐βA and INHBB/ Inhibin‐βB) between malignant and ovarian tissues at the RNA and protein level and assess the relationship between activin and immune cells in EOC.MethodsPublicly available RNA sequencing data were accessed from GEO (#GSE143897) with normalization and quantification performed via DESeq2. Immune gene expression profile was further explored within the TCGA‐OV cohort derived from The Cancer Genome Atlas (TCGA). Immunohistochemical analysis was performed to evaluate activin A and T‐cell markers CD8 and FoxP3 at the protein level. ELISA to activin‐A was used to assess levels in the ascites of advanced EOC patients. Kaplan–Meier curves were generated to visualize survival outcomes.ResultsGene expression levels of components of the activin signaling pathway were elevated within EOC when compared to a benign cohort, with differences in activin type I/II receptor gene profiles identified. Additionally, INHBA gene expression was linked to lymphocytic immune markers in EOC samples. Immunohistochemistry analysis revealed a positive correlation of CD8 and FOXP3 staining with activin A at the protein level in both primary and metastatic epithelial ovarian cancer samples. Furthermore, Activin‐A (inhibin‐βA) is significantly elevated in EOC patient ascites.ConclusionINHBA expression is elevated within EOC, correlating with worse survival, with activin protein levels correlating with specific immune infiltration. Our findings suggest that activin‐A may play a role in suppressing anti‐tumor immunity in EOC, highlighting its potential as a therapeutic target.

HCK Promotes High-Grade Serous Ovarian Cancer Tumorigenesis through CD44 and NOTCH3 Signaling

Abstract High-grade serous ovarian cancer (HGSOC) is a highly aggressive and lethal subtype of ovarian cancer. While most patients initially respond to standard-of-care treatment, the majority will eventually relapse and succumb to their disease. Despite significant advances in our understanding of this disease, the mechanisms that govern the distinctions between HGSOC with good and poor prognosis remain unclear. In this study, we implemented a proteogenomic approach to analyze gene expression, proteomic and phosphoproteomic profiles of HGSOC tumor samples to identify molecular pathways that distinguish HGSOC tumors relative to clinical outcome. Our analyses identify significant upregulation of hematopoietic cell kinase (HCK) expression and signaling in poor prognostic HGSOC patient samples. Analyses of independent gene expression datasets and IHC of patient samples confirmed increased HCK signaling in tumors relative to normal fallopian or ovarian samples and demonstrated aberrant expression in tumor epithelial cells. Consistent with the association between HCK expression and tumor aggressiveness in patient samples, in vitro phenotypic studies showed that HCK can, in part, promote cell proliferation, colony formation, and invasive capacity of cell lines. Mechanistically, HCK mediates these phenotypes, partly through CD44 and NOTCH3-dependent signaling, and inhibiting CD44 or NOTCH3 activity, either genetically or through gamma-secretase inhibitors, can revert HCK-driven phenotypes. Implications: Collectively, these studies establish that HCK acts as an oncogenic driver of HGSOC through aberrant activation of CD44 and NOTCH3 signaling and identifies this network as a potential therapeutic opportunity in a subset of patients with aggressive and recurrent HGSOC.

Evolving roles of activins and inhibins in ovarian cancer pathophysiology

Activins and inhibins are unique members of the transforming growth factor-β (TGFβ) family of growth factors, with the ability to exert autocrine, endocrine, and paracrine effects in a wide range of complex physiologic and pathologic processes. Although first isolated within the pituitary, emerging evidence suggests broader influence beyond reproductive development and function. Known roles of activin and inhibin in angiogenesis and immunity along with correlations between gene expression and cancer prognosis suggest potential roles in tumorigenesis. Here, we present a review of the current understanding of the biological role of activins and inhibins as it relates to ovarian cancers, summarizing the underlying signaling mechanisms and physiologic influence, followed by detailing their roles in cancer progression, diagnosis, and treatment.

TGFβ signaling networks in ovarian cancer progression and plasticity

AbstractEpithelial ovarian cancer (EOC) is a leading cause of cancer-related death in women. Late-stage diagnosis with significant tumor burden, accompanied by recurrence and chemotherapy resistance, contributes to this poor prognosis. These morbidities are known to be tied to events associated with epithelial-mesenchymal transition (EMT) in cancer. During EMT, localized tumor cells alter their polarity, cell–cell junctions, cell–matrix interactions, acquire motility and invasiveness and an exaggerated potential for metastatic spread. Key triggers for EMT include the Transforming Growth Factor-β (TGFβ) family of growth factors which are actively produced by a wide array of cell types within a specific tumor and metastatic environment. Although TGFβ can act as either a tumor suppressor or promoter in cancer, TGFβ exhibits its pro-tumorigenic functions at least in part via EMT. TGFβ regulates EMT both at the transcriptional and post-transcriptional levels as outlined here. Despite recent advances in TGFβ based therapeutics, limited progress has been seen for ovarian cancers that are in much need of new therapeutic strategies. Here, we summarize and discuss several recent insights into the underlying signaling mechanisms of the TGFβ isoforms in EMT in the unique metastatic environment of EOCs and the current therapeutic interventions that may be relevant.

PVT1 is a stress-responsive lncRNA that drives ovarian cancer metastasis and chemoresistance

Metastatic growth of ovarian cancer cells into the peritoneal cavity requires adaptation to various cellular stress factors to facilitate cell survival and growth. Here, we demonstrate the role of PVT1, one such stress induced long non-coding RNA, in ovarian cancer growth and metastasis. PVT1 is an amplified and overexpressed lncRNA in ovarian cancer with strong predictive value for survival and response to targeted therapeutics. We find that expression of PVT1 is regulated by tumor cells in response to cellular stress, particularly loss of cell–cell contacts and changes in matrix rigidity occurring in a YAP1-dependent manner. Induction of PVT1 promotes tumor cell survival, growth, and migration. Conversely, reducing PVT1 levels robustly abrogates metastatic behavior and tumor cell dissemination in cell lines and syngeneic transplantation models in vivo. We find that reducing PVT1 causes widespread changes in the transcriptome leading to alterations in cellular stress response and metabolic pathways including doxorubicin metabolism, which impacts chemosensitivity. Together, these findings implicate PVT1 as a promising therapeutic target to suppress metastasis and chemoresistance in ovarian cancer.

Loss of Predicted Cell Adhesion Molecule MPZL3 Promotes EMT in Ovarian Cancer

Abstract Myelin protein zero-like 3 (MPZL3) is an immunoglobulin-containing transmembrane protein with predicted cell adhesion molecule function. Loss of 11q23, in which the MPZL3 gene resides, is frequently observed in cancer. Yet the role and consequences of altered MPZL3 expression have not been explored in tumor development and progression. We addressed this in ovarian cancer, in which both MPZL3 amplification and deletions are observed in respective subsets of high-grade serous specimens. Whereas high and low MPZL3-expressing populations are similarly observed in primary ovarian tumors from an independent patient cohort, metastatic omental tumors largely display decreased MPZL3 expression, suggesting that MPZL3 loss is associated with metastatic progression. MPZL3 knockdown leads to an increase in EMT gene expression in OVCAR4 and OVCA433 cell lines, a transcript signature that is associated with poor patient outcomes. MPZL3 promotes homotypic cancer cell adhesion, and decreasing MPZL3 expression enhances invasion and clearance of mesothelial cell monolayers. Conversely, MPZL3 loss abrogates cell-cycle progression and proliferation, with cells adopting senescence features. This was associated with decreased sensitivity to cisplatin and reduced DNA damage and apoptosis in response to treatment in OVCAR4 cells. Our study suggests that decreased expression of the predicted adhesion molecule MPZL3 is associated with low proliferation but increased metastatic potential during ovarian cancer tumor progression. Significance: This work presents novel findings that decreased expression of the potential cell adhesion molecule MPZL3 is a phenotype of ovarian cancer progression and metastasis.

Drp1 splice variants regulate ovarian cancer mitochondrial dynamics and tumor progression

Abstract Aberrant mitochondrial fission/fusion dynamics are frequently associated with pathologies, including cancer. We show that alternative splice variants of the fission protein Drp1 ( DNM1L ) contribute to the complexity of mitochondrial fission/fusion regulation in tumor cells. High tumor expression of the Drp1 alternative splice variant lacking exon 16 relative to other transcripts is associated with poor outcome in ovarian cancer patients. Lack of exon 16 results in Drp1 localization to microtubules and decreased association with mitochondrial fission sites, culminating in fused mitochondrial networks, enhanced respiration, changes in metabolism, and enhanced pro-tumorigenic phenotypes in vitro and in vivo. These effects are inhibited by siRNAs designed to specifically target the endogenously expressed transcript lacking exon 16. Moreover, lack of exon 16 abrogates mitochondrial fission in response to pro-apoptotic stimuli and leads to decreased sensitivity to chemotherapeutics. These data emphasize the pathophysiological importance of Drp1 alternative splicing, highlight the divergent functions and consequences of changing the relative expression of Drp1 splice variants in tumor cells, and strongly warrant consideration of alternative splicing in future studies focused on Drp1.