Abstract 811: Histological Heterogeneity Contributes to Sunitinib Resistance in Clear Cell Renal Cell Carcinoma

Abstract Introduction: The receptor tyrosine kinase (RTK) inhibitor sunitinib is the first line treatment for advanced clear cell renal cell carcinoma (ccRCC). Sunitinib inhibits angiogenesis via blocking signaling through VEGFR. About 80% of patients develop resistance after a drug-sensitive period. Molecular changes early in treatment may impact drug resistance, but are poorly understood. Experimental Procedures: ACHN, 786-O and Renca cell lines were treated with 1 µM sunitinib. NSG mice were s.c. xenografted with the model cell lines and were treated with sunitinib at 40 mg/kg/day dose. mRNA expression was screened using Illumina HT-12 bead chip array and miRNA expression was assessed by Nanostring nCounter assay. R statistical packages were used for data processing. Reactome and miRPath softwares were used for downstream analysis. Results: Sunitinib treatment of ccRCC xenografts led to several early changes in tumor histology, such as the emergence of live tumor areas within the necrotic spaces. These areas showed membranous staining for E-cadherin, and β-catenin, while the rest of the tumor and vehicle-treated tumors were negative. In vitro model cell lines developed cancer spheroids when treated with sunitinib. Cancer spheroids were highly tumorigenic and metastatic, and expressed several established cancer stem cell markers. ccRCC cancer spheres, but not the 2D adherent cells, showed membranous staining for E-cadherin and β-catenin; similarly to the live tumor areas observed in in vivo sunitinib treatment. In vitro inhibition of E-cadherin by EGTA or by siRNA, interfered with viability of sunitinib treated ccRCC cell lines. Conclusions: Sunitinib treatment causes early phenotypic changes of the tumor in vivo and in vitro. The formation of highly metastatic and tumorigenic cancer spheres in model cell lines is the most prominent effect in vitro. We provide preliminary evidence that sunitinib induced in vitro cancer spheres and the live tumor areas that survive within necrotic patches of the sunitinib-treated xenografts, are related. Finally, membranous expression of E-cadherin enhances the survival of ccRCC cell lines under sunitinib treatment. Citation Format: Zsuzsanna Lichner, Rola Saleeb, Henriett Butz, Roy Nofech-Mozes, Sara Riad, Mina Farag, Andras Kapus, George Yousef. Histological heterogeneity contributes to sunitinib resistance in clear cell renal cell carcinoma [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 811. doi:10.1158/1538-7445.AM2017-811