Abstract 1935: Gene expression analysis reveals distinct pathways of resistance to antiangiogenic therapy in ovarian cancer

Abstract

Abstract Purpose: The rapid development of resistance after an initial response phase is a major challenge of antiangiogenic therapies. The molecular mechanisms underlying clinical resistance to antiangiogenic therapies are not yet well understood. We aimed to identify potential mediators of resistance to antiangiogenic therapy, with a view toward eventually developing therapeutic approaches to improve antiangiogenic therapies. Methods: We developed preclinical in vivo phenotypic resistance models of antiangiogenic therapy using human ovarian carcinoma cells. We used two representative anti-VEGF agents to block VEGF (bevacizumab, 10 mg/kg BIW, IP) or its receptor (sorafenib, 30 mg/kg daily, PO). The treatment was given until tumors showed a long-term trend toward continued progression after an initial response (resistant tumor). Whereas treatment-sensitive tumors were defined by a long-term trend toward stable disease or regression. We conducted next generation sequencing to compare changes in the gene expression in resistant and sensitive tumors, distinguishing their origin (tumor vs stroma cells). To get a more detailed perspective of the overall changes in gene expression, Gene Set Enrichment Analysis (GSEA) was performed by pair-wise comparison according to treatment outcome (resistant vs sensitive) with respect to bevacizumab and sorafenib, of which the entire MSigDB collections were compared to. Further, significantly enriched pathways were validated with clinical gene expression profiling studies of various tumor types deposited in GEO and ArrayExpress. Results: Our GSEA analysis revealed significant differences (FDR<0.25) in enrichment of various pathways between sensitive and resistant tumors. We observed ERK, P38 MAPK, ATP dependent helicase activity, and phosphatidylinositide 3-kinases pathways are differentially enriched between sensitive and resistant phenotypes of bevacizumab-treated group. In sorafenib-resistant group, six pathways were enriched including E2F1, KRAS and PDGF regulated pathways. Conclusions: Here, we report distinct pathways of response to bevacizumab and sorafenib in preclinical ovarian cancer models, which may provide critical insights into ovarian tumor's adaption during anti-VEGF blockade. These pathways may also provide important clues for identifying synergistic therapeutic strategies to overcome or delay resistance to antiangiogenic agents. Citation Format: Bharat Kumar Devapatla, Pharavee Jaiprasart, Sukyung Woo. Gene expression analysis reveals distinct pathways of resistance to antiangiogenic therapy in ovarian cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1935. doi:10.1158/1538-7445.AM2015-1935