Sunitinib-Resistant Ccrcc Cell Lines Subjected To Tki/Mtor Inhibitors As A Model For Sequence Therapy

Introduction: Treatment of advanced renal cell carcinoma (RCC) by tyrosine kinase inhibitors like Sunitinib (SUN) is hampered by the appearance of drug resistance. Sequence therapy using different TKIs as well as inhibitors attacking the mTOR pathway offers a promising tool to overcome this lack in ccRCC therapy. Material and Methods: CAKI-1/2, A-498 and 786-O cell lines were treated with different SUN-concentrations to obtain the corresponding IC50-values. Using sub-lethal SUNI-concentrations they were cultivated for up to 20 passages. At defined intervals total RNA was isolated. Microarray analysis was performed for a global miRNA expression profiling, SUN-resistant cell lines were subjected to an ongoing sequence therapy using TKI 258 (Novartis) and RAD001 as a mTOR inhibitor. Resistance-development as well as drug efficacy during sequence therapy was monitored by sequential quantification of the growth behavior and changes in drug-sensitivity by proliferation-assays. Results: Growth behavior of all ccRCC cell lines during SUN-application is reduced down to 10-60% depending on cell number and cell type. Long term application (10-20 passages) of SUN at concentrations near the IC50 value results in a constantly increasing drug resistance and the cells acquire a growth rate of 60-90% compared to the untreated long term control. Accordingly to these phenomenon we observed characteristic changes in miRNA expression. Starting sequence therapy SUN-resistant cell lines (CAKI-1 and 786-0) offer initially an increase in drug resistance to TKI 258 in pretreated CAKI-1 cells. In contrast long term SUN-application had no influence in the sensitivity to RAD001 as compared to untreated controls in both cell lines. Conclusion: Understanding the molecular changes during drug resistance in ccRCC provides an indispensable prerequisite to create new therapeutic strategies in the treatment of metastatic renal cell carcinoma. The results indicate a complex mechanism in drug resistance depending on therapeutic protocol and cell type. However, drug-resistant cell lines offer a promising tool to elucidate the molecular mechanism responsible for drug-resistance as well as to simulate the benefit of a sequence therapy. Since miRNAs represent an important tool in gene regulation the observed patterns may help to elucidate new genes involved in drug resistance in ccRCC. Citation Format: Gerhard Unteregger, Darja Schendel, Joana Heinzelmann, Anne Weiland, Simone Ernst, Michael Stoeckle, Kerstin Junker. Sunitinib-resistant ccRCC cell lines subjected to TKI/mTOR inhibitors as a model for sequence therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1712. doi:10.1158/1538-7445.AM2014-1712