Abstract 1903: In vitro and in vivo characterization of sunitinib resistance in renal cancer models
Authors: Serova Maria , Santos Celia Dos , Tijeras-Raballand Annemilai , Riveiro Maria-Eugenia , de Gramont Armand , Raymond Eric , Faivre Sandrine 
Published: August 2012

Abstract
Background. Resistance to TK inhibitors such as sunitinib and sorafenib can rapidly develop through multiple mechanisms, including angiogenic growth factors redundancy or switches in signaling pathways, leading to an acceleration of tumor growth after treatment failure and an increased aggressiveness. The aim of the present study was to investigate, in vitro and in vivo, the molecular mechanisms of acquired resistance to sunitinib in renal cell carcinoma (RCC) models. Materials and Methods: CAKI1 (VHL+) and 786-0 (VHL-) renal carcinoma cells were exposed to stepwise increasing doses of sunitinib for &gt;6 months. Invasiveness of cells was determined by Matrigel invasion assay. Genes and protein expressions were assessed by qRT-PCR and western blot. For in vivo experiments, CAKI1 cells were xenografted in nude mice and treated continuously with 60 mg/kg oral sunitinib until progression. Results. CAKI-Suni and 786-Suni cells treated for an extensive period of time displayed a 2-fold IC50 increase compared to parental cells. Several changes in gene expressions were detected in these cells Protracted exposure to sunitinib led to a &gt;3-fold increase of ErbB3 and CDH1 mRNA expression in CAKI-Suni and 786-Suni cells compared to the parental CAKI1 and 786-0 cells. Resistance to sunitinib was also associated with AKT and ERK activation. In addition, CAKI-Suni cell line was at least 3 times more invasive than its parental counterpart. To compare these in vitro modifications to the ones observed after the development of an in vivo resistance to sunitinib, nude mice bearing CAKI1 xenografts were treated with 60 mg/kg/day oral sunitinib until progression. Sunitinib induced a significant tumor growth retardation with a median PFS of 59 days in the sunitinib arm compare to 22 days in the placebo arm (p&lt;0.0001). After 35 days of treatment several tumors became progressive under sunitinib. IHC analysis of tumor tissues revealed a decrease in necrosis and an increase in the number of blood vessels in the sunitinib-resistant tumors compared to the sunitinib-controlled tumors. In the relapsed tumors, we observed a 2-fold increase in mRNA expression of VEGFA, CXCR4, CA-IX and HIF1A and a 4-fold decrease expression of E-cadherin (CDH1). Resistance to sunitinib was also associated with an increase in CXCR4, vimentin and ErbB3 protein levels. Conclusions. Long term exposure to sunitinib induced significant changes in gene expression, invasion properties and survival signaling pathways in RCC tumors. Both in vitro and in vivo data suggest a possible role of the epithelial-to-mesenchymal transition in the relapse in RCC tumors treated by sunitinib.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1903. doi:1538-7445.AM2012-1903