Although initial treatment of ovarian cancer is successful, tumors typically relapse and become resistant to treatment. Because of poor infiltration of effector T cells, patients are mostly unresponsive to immunotherapy. Plasma gelsolin (pGSN) is transported by exosomes (small extracellular vesicle, sEV) and plays a key role in ovarian cancer chemoresistance, yet little is known about its role in immunosurveillance. Here, we report the immunomodulatory roles of sEV-pGSN in ovarian cancer chemoresistance. In chemosensitive conditions, secretion of sEV-pGSN was low, allowing for optimal CD8+ T-cell function. This resulted in increased T-cell secretion of IFNγ, which reduced intracellular glutathione (GSH) production and sensitized chemosensitive cells to cis-diaminedichloroplatinum (CDDP)-induced apoptosis. In chemoresistant conditions, increased secretion of sEV-pGSN by ovarian cancer cells induced apoptosis in CD8+ T cells. IFNγ secretion was therefore reduced, resulting in high GSH production and resistance to CDDP-induced death in ovarian cancer cells. These findings support our hypothesis that sEV-pGSN attenuates immunosurveillance and regulates GSH biosynthesis, a phenomenon that contributes to chemoresistance in ovarian cancer. Significance: These findings provide new insight into pGSN-mediated immune cell dysfunction in ovarian cancer chemoresistance and demonstrate how this dysfunction can be exploited to enhance immunotherapy.

Ovarian cancer (OC) is the most deadly gynecological malignancy, with unmet clinical need for new therapeutic approaches. The relaxin peptide is a pleiotropic hormone with reproductive functions in the ovary. Relaxin induces cell growth in several types of cancer, but the role of relaxin in OC is poorly understood. Here, using cell lines and xenograft models, we demonstrate that relaxin and its associated GPCR RXFP1 form an autocrine signaling loop essential for OC in vivo tumorigenesis, cell proliferation, and viability. We determined that relaxin signaling activates expression of prooncogenic pathways, including RHO, MAPK, Wnt, and Notch. We found that relaxin is detectable in patient-derived OC tumors, ascites, and serum. Further, inflammatory cytokines IL-6 and TNF-α activated transcription of relaxin via recruitment of STAT3 and NF-κB to the proximal promoter, initiating an autocrine feedback loop that potentiated expression. Inhibition of RXFP1 or relaxin increased cisplatin sensitivity of OC cell lines and abrogated in vivo tumor formation. Finally, we demonstrate that a relaxin-neutralizing antibody reduced OC cell viability and sensitized cells to cisplatin. Collectively, these data identify the relaxin/RXFP1 autocrine loop as a therapeutic vulnerability in OC.

During tubo-ovarian high-grade serous carcinoma (HGSC) progression, tumoral cells undergo phenotypic changes in their epithelial marker profiles, which are essential for dissemination processes. Here, we set out to determine whether standard epithelial markers can predict HGSC patient prognosis. Levels of E-CADH, KRT7, KRT18, KRT19 were quantified in 18 HGSC cell lines by Western blot and in a Discovery cohort tissue microarray (TMA) (n = 101 patients) using immunofluorescence. E-CADH and KRT7 levels were subsequently analyzed in the TMA of the Canadian Ovarian Experimental Unified Resource cohort (COEUR, n = 1158 patients) and in public datasets. Epithelial marker expression was highly variable in HGSC cell lines and tissues. In the Discovery cohort, high levels of KRT7 and KRT19 were associated with an unfavorable prognosis, whereas high E-CADH expression indicated a better outcome. Expression of KRT7 and E-CADH gave a robust combination to predict overall survival (OS, p = 0.004) and progression free survival (PFS, p = 5.5 × 10⁻⁴) by Kaplan–Meier analysis. In the COEUR cohort, the E-CADH-KRT7 signature was a strong independent prognostic biomarker (OS, HR = 1.6, p = 2.9 × 10⁻⁴; PFS, HR = 1.3, p = 0.008) and predicted a poor patient response to chemotherapy (p = 1.3 × 10⁻⁴). Our results identify a combination of two epithelial markers as highly significant indicators of HGSC patient prognosis and treatment response.

Background: New predictive biomarkers are needed to accurately predict metastasis-free survival (MFS) and cancer-specific survival (CSS) in localized prostate cancer (PC). Keratin-7 (KRT7) overexpression has been associated with poor prognosis in several cancers and is described as a novel prostate progenitor marker in the mouse prostate. Methods: KRT7 expression was evaluated in prostatic cell lines and in human tissue by immunohistochemistry (IHC, on advanced PC, n = 91) and immunofluorescence (IF, on localized PC, n = 285). The KRT7 mean fluorescence intensity (MFI) was quantified in different compartments by digital analysis and correlated to clinical endpoints in the localized PC cohort. Results: KRT7 is expressed in prostatic cell lines and found in the basal and supra-basal compartment from healthy prostatic glands and benign peri-tumoral glands from localized PC. The KRT7 staining is lost in luminal cells from localized tumors and found as an aberrant sporadic staining (2.2%) in advanced PC. In the localized PC cohort, high KRT7 MFI above the 80th percentile in the basal compartment was significantly and independently correlated with MFS and CSS, and with hypertrophic basal cell phenotype. Conclusion: High KRT7 expression in benign glands is an independent biomarker of MFS and CSS, and its expression is lost in tumoral cells. These results require further validation on larger cohorts.

Background: High grade serous cancer (HGSC) remains a highly fatal malignancy with less than 50% of patients surviving 5 years after diagnosis. Despite its high mutational burden, HGSC is relatively refractory to checkpoint immunotherapy, suggesting that additional features of the cancer and its interactions with the immune system remain to be understood. Natural killer (NK) cells may contribute to HGSC control, but the role(s) of this population or its subsets in this disease are poorly understood. Methods: We used a TMA containing duplicate treatment-naïve tumors from 1145 patients with HGSC and a custom staining panel to simultaneously measure macrophages, T cells and NK cells, separating NK cells based on CD16a expression. Using pathologist-validated digital pathology, machine learning, computational analysis and Pearson’s correlations, we quantitated infiltrating immune cell density, co-infiltration and co-localization with spatial resolution to tumor region. We compared the prognostic value of innate, general, and adaptive immune cell “neighborhoods” to define characteristics of HGSC tumors predictive for progression-free survival and used flow cytometry to define additional features of the CD16a ^dim NK cell subset. Results: NK cells were observed in >95% of tumor cores. Intrastromal localization of CD16a ^low and CD16a ^high NK cells was associated with shorter and longer progression-free survival, respectively. CD16a ^high NK cells most frequently co-localized with T cells and macrophages; their proximity was termed an “adaptive” neighborhood. We find that tumors with more area represented by adaptive immune cell neighborhoods corresponded to superior progression free survival. In contrast, CD16a ^low NK cells did not co-infiltrate with other immune cell types, and expressed the ectonucleotidases, CD39 and CD73, which have been previously associated with poor prognosis in patients with HGSC. Conclusions: Progression-free survival for patients with HGSC may be predicted by the subset of NK cells within the tumor infiltrate (i.e. CD16a ^high vs. CD16a ^low ). NK cell subtypes were associated predictable co-infiltrating and co-localizing leukocyte subsets, suggesting that their presence and activity may influence, or be influenced by the tumor microenvironment. Our data suggest that immunotherapeutic strategies for HGSC should consider the constitution of NK cell subsets and may benefit from mobilizing and activating CD16 ^high NK cells.