Characterization Of Microrna Expression During The Development Of Resistance To A Mtor-Inhibitor In Renal Cell Carcinoma

Introduction: Second line therapy of metastatic renal cell carcinoma (RCC) using the mTOR inhibitor RAD001 (everolimus) is hampered by the appearance of drug resistance. The cellular mechanisms leading to drug resistance are not yet clarified. Although the influence of miRNAs is proven for other systemic treatments, their impact on mTOR inhibitors is not investigated. Therefore, we analyzed miRNA alterations in correlation to development of resistance to RAD001 in RCC cell culture models. Material and Methods: The RCC cell line 786-O was treated with 1μM RAD001 for up to 20 passages after developing sunitinib resistance. TotalRNA was isolated at defined intervals. Resistance-development as well as drug efficacy during the treatment was monitored by proliferation assays. MiRNA Microarrays (Agilent Technologies) were performed using RAD001 sensitive and RAD001 resistant cells to identify differently expressed miRNAs. Results were validated by qRT PCR. Functional analyses are performed after transfection of RAD001 sensitive cells with miRNA candidates. Results: The Microarray analyses revealed a miRNA signature including 9 differently expressed miRNAs in RAD001 resistant cells compared to sensitive cells. QRT-PCR results showed that especially miR-302e was strongly up-regulated by the factor of four. At present, functional analyses of miR-302e are ongoing. Conclusion: To our knowledge this is the first study analyzing miRNA alterations during the development of resistance to mTOR inhibitors. We have shown that miR-302e expression is associated with RAD001 resistance in RCC cells. Since miR-302e is a known tumor suppressor modulating radio sensitivity and drug sensitivity in several tumors we are proving now if miR-302e can regulate the mTOR inhibitor resistance of RCC. Citation Format: Joana Heinzelmann, Franziska Bauer, Gerhard Unteregger, Darja Schendel, Anne Weiland, Michael Stockle, Kerstin Junker. Characterization of MicroRNA Expression during the Development of Resistance to a mTOR-Inhibitor in renal cell carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1961.