Ovarian cancer is the most lethal gynecological cancer, which affects one in 70 females in the United States during their lifetime. While cisplatin is the frontline treatment for ovarian cancer, chemoresistance severely limits the treatment success. The goal of this study is to identify novel therapeutic targets to overcome cisplatin resistance. We recently identified Collagen type XI alpha 1 (COL11A1) as a novel biomarker associated with cisplatin resistance in ovarian cancer. COL11A1 is a component of the tumor stroma and its expression is restricted to cancer-associated fibroblasts (CAFs) adjacent to tumor cells. We further showed that COL11A1 protects ovarian cancer cells from cisplatin-induced apoptosis, yet the underlying mechanism is largely unknown. To understand the molecular mechanism by which COL11A1 protects cancer cells from cisplatin-induced apoptosis, we overexpressed COL11A1 in ovarian cancer cells and performed RNA-Seq. Our RNA-Seq data revealed that COL11A1 did not change the levels of genes involved in cisplatin transport, inactivation, and DNA repair pathways in cancer cells, which are well-established mechanisms to confer cisplatin resistance. Rather, COL11A1 enhances the expression of the Inhibitors of Apoptosis Proteins (IAPs), including XIAP, BIRC2 (c-IAP1) and BIRC3 (c-IAP2). Using a full-length COL11A1 protein, genetic manipulation, and co-culture method, we confirmed that COL11A1 significantly increases the expression of IAPs upon cisplatin treatment. The inhibition of XIAP, BIRC2 and BIRC3 with an IAP antagonist BV6 attenuated the ability of COL11A1 to inhibit cisplatin-mediated apoptosis. Our data indicates that COL11A1 activates Akt, and Akt is known to phosphorylate XIAP at serine-87, which protects it from ubiquitination and degradation in response to cisplatin. Collectively, our data identify IAP as a mediator of COL11A1’s action in blocking cisplatin-induced apoptosis.

Note: This abstract was not presented at the meeting.

Citation Format: Miran Rada, Jennifer Cha, Jessica Sage, Sandra Orsulic, Dong-Joo Cheon. Collagen type XI alpha 1 confers cisplatin chemoresistance in ovarian cancer through inhibitor of apoptosis proteins (IAPs) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2975. doi:10.1158/1538-7445.AM2017-2975