Abstract 1551: miR-625-3p enhances chemosensitivity in ovarian cancer cells through exosomal export of cisplatin and paclitaxel
Authors: Yeung Chi Lam Au , Tsuruga Tetsushi , Yip Kay-Pong , Ferri-Borgogno Sammy , Mok Samuel 
Published: June 2022

Abstract
Although a majority of women with high-grade serous ovarian cancer (HGSC) achieve a complete response to first-line platinum- and paclitaxel-based chemotherapy, around thirty percent of patients are identified as incomplete responders. Their diseases typically either does not respond or progresses during treatment (refractory) or recurs within 6 months of completing treatment (resistant), suggesting the inherit or intrinsic characteristics of the tumor. Currently, there are no biomarkers that can predict intrinsic resistance, which can avoid unnecessary treatment and toxicity. MicroRNAs (miRNAs) provide a novel master layer of regulation of gene expression. However, the molecular mechanisms by which miRNAs confer a chemoresistant phenotype in ovarian cancer have not been elucidated. To identify miRNAs that are associated with intrinsic chemoresistance in HGSC, Ion Torrent next-generation sequencing analysis of miRNAs was performed on microdissected chemosensitive and chemorefractory primary HGSC cases. Amongst all the miRNAs that were significantly down-regulated in chemorefractory cases, lower miR-625-3p expression was found to be associated with poorer overall and progression-free survivals. Further functional studies showed that overexpression of miR-625-3p significantly decreased cisplatin and paclitaxel resistance in ovarian cancer cells in vitro and in vivo. Online target prediction algorithms together with transcriptome profiling of HGSC cells transfected with miR-625-3p mimics or control mimics identified SSX2IP as a direct target of miR-625-3p, suggesting that SSX2IP may play a role in conferring cisplatin/paclitaxel resistance in HGSC by mediating the effect of miR-625-3p. SSX2IP is a microtubule anchoring and centriolar satellite protein, which plays a critical role in controlling microtubule length and orientation, and centrosome maturation. We demonstrated that HGSC cells transfected with SSX2IP had marked increases in microtubule masses, intracellular multivesicular body trafficking and exosomal cisplatin level; and a decrease in intracellular cisplatin level. In conclusion, down-regulation of miR-625-3p confers cisplatin/paclitaxel resistance in ovarian cancer cells via its novel direct target SSX2IP. SSX2IP alters the microtubule dynamics and subsequently mediates inter-organelle crosstalks between microtubules and multivesicular bodies, which facilitate exosomal export of cisplatin and paclitaxel of HGSC cells. This study is crucial for developing new predictive biomarkers for intrinsic chemoresistance, and new treatment strategies for HGSC based on upregulating miR-625-3p or downregulating SSX2IP expression in ovarian cancer cells, which will enhance cisplatin and paclitaxel sensitivity, and improve patient survival rates.
Citation Format: Chi Lam Au Yeung, Tetsushi Tsuruga, Kay-Pong Yip, Sammy Ferri-Borgogno, Samuel Mok. miR-625-3p enhances chemosensitivity in ovarian cancer cells through exosomal export of cisplatin and paclitaxel [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1551.