Ovarian cancer (OvCa) is frequently accompanied by accumulation of intraperitoneal ascites fluid early in disease progression. This fluid is rich in soluble and cellular components including tumor cells and multicellular aggregates (MCAs) of 150-300 um diameter shed from the primary tumor. In addition to chemical cues, ascites fluid buildup can also alter the force environment in the peritoneal cavity, thereby impacting the primary tumor, disseminating cells and MCAs, and host peritoneal tissues. Whereas the intraperitoneal pressure (IPP) of the normal peritoneal cavity is subatmospheric (-5 mmHg), the IPP measured in ovarian cancer patients with tense ascites is reported to be 24 mmHg. The potential effect of ascites-induced changes in peritoneal mechanobiology on tumor cells and host structures has not been investigated due to a lack of appropriate model systems. As a first approximation, we have begun preliminary investigations into the response of tumor and host structures to compressive and strain (stretching) forces. Our initial experiments used MCAs sealed in nonadherent cell culture bags placed into a temperature-controlled stainless-steel pressure vessel and subjected to a compressive force of 22-24 mmHg using an Instron system. While this approach is feasible for short-term experiments, longer-term compression experiments require a system with gas exchange to maintain cell viability. Thus, we fabricated a mold designed to fit within a Flexcell-400C Compression system Biopress+ Bioflex 6-well plate. This mold was used to produce porous hydrogels containing defined void areas so as to encapsulate MCAs within the hydrogel carrier and thereby ensure a more uniform encounter with the Flexcell compression plate. Our initial experiments investigated the effects of MCA compression on gene expression associated with epithelial-to-mesenchymal transition (EMT). Data indicate that short-term static compression (6h) downregulates CDH2 (N-cadherin, Ncad) with cell line-dependent inhibition of EMT regulators including SNAI1, SNAI2, and TWIST. In contrast, long-term compression (24h) upregulated expression of mesenchymal genes including CDH2, MMP14, Wnt5a, ROR1, and ROR2. To examine the impact of strain on receptivity of host peritoneal tissues to metastatic implantation, we used control or strained ex vivo explants of murine peritoneal tissue immobilized on silastic resin. Strained peritoneal tissue exhibited a 3-fold increase in stiffness as determined by atomic force microscopy. Concomitantly, adhesion of ovarian cancer cells to strained peritoneum increased by 4.5-fold. Together these data provide support for a more detailed investigation of the complex role of peritoneal mechanobiology as an important microenvironmental regulator of ovarian cancer metastatic success.

Citation Format: Yuliya Klymenko, Rebecca Wates, Yueying LIu, Rachel Lombard, Holly Weiss-Bilka, Leigh Campbell, Diane Wagner, Matthew J. Ravosa, M. Sharon Stack. Modeling ascites-induced changes in peritoneal mechanobiology and ovarian cancer metastatic success. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr A38.