Abstract B071: Mesothelial cell motility and contractility promote ovarian cancer metastatic potential through a PKA-dependent mechanism

Abstract Ovarian cancer is the leading cause of death among gynecological cancers, and metastasis to the peritoneum occurs in over 60% of patients. To form these metastatic implants, disseminated cancer cells attach and invade through the mesothelial barrier that lines the peritoneal organs in the abdominal cavity. A better understanding of cancer-mesothelial interactions will lead to identification of mesothelial-specific prognostic markers and the discovery of therapeutic targets to limit ovarian cancer metastatic spread. The goal of our studies is to dissect how mesothelial cell contractility and barrier integrity impact the metastatic potential of high-grade serous ovarian cancer. We developed an imaging-based live cell assay that assesses the rate at which the ovarian cancer spheroids transmigrate across mesothelial monolayers (we termed this process “clearance”) and preconditioned the mesothelial monolayer with different pharmacologic agents. We discovered that treatment with forskolin, a cAMP activator, significantly reduced the number of clearing spheroids compared to the control untreated condition. Inhibition of protein kinase A (PKA) in mesothelial cells that were treated with forskolin reversed the anti-metastatic effects and restored clearance rates to baseline levels. Next, we analyzed mesothelial cell-cell junctions, cytoskeletal organization, traction forces and cell motility patterns. Compared to the control condition, forskolin treated mesothelial cells exhibited higher expression levels of ZO-1 and β-catenin junctions, as well as reduction in actin stress fibers. Consistent with these results, we found that forskolin reduced traction forces and mesothelial cell migration was assessed through a wound healing assay. To evaluate the impact of increasing mesothelial contractility, we treated mesothelial cells with calyculin A, a potent phosphatase inhibitor that elevated expression of phospho-myosin to promote traction forces and increase spheroid clearance rates. Transcriptomic and proteomic studies of mesothelial monolayers treated with forskolin revealed a role for the c-Jun pathway. c-Jun is known to regulate cell migration and response to environmental stress, and thus presents a promising candidate for enhancing mesothelial barrier function and protecting against ovarian cancer spheroid invasion. Our findings suggest that normalizing mesothelial cell contractility via a PKA-dependent mechanism enhances barrier integrity and limits the invasive potential of ovarian cancer spheroids. A better understanding of cancer-mesothelial paracrine signaling and environmental stressors in the peritoneal cavity that lead to mesothelial barrier dysfunction hold promise for the discovery of mesothelial-targeted therapies to reduce ovarian cancer metastatic dissemination. Citation Format: Dorota Jazwinska, Youngbin Cho, Ioannis Zervantonakis. Mesothelial cell motility and contractility promote ovarian cancer metastatic potential through a PKA-dependent mechanism abstract. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84 (5 Suppl₂): Abstract nr B071.