Abstract 366: Changes in gene expression profiles in human breast & liver cancer cells and xenografts acquiring resistance to sunitinib
Authors: Albert Sebastien , Serova Maria , Bousquet Guilhem , Varna Mariana , Sablin Marie-Paule , Bieche Ivan , Astorgues-Xerri Lucile , Janin Anne , Raymond Eric , Faivre Sandrine 
Published: February 2011

Abstract
Background: Deciphering acquired mechanisms of resistance to sunitinib, a multitarget receptor tyrosine kinase inhibitors blocking VEGFR, PDGFR, KIT, and RET, remains a major clinical challenge for developing a second generation of compounds, simultaneous and sequential combination strategies. This study aimed characterizing molecular changes associated with acquired cellular resistance to sunitinib in two human cancer models.
Materials and Methods: Parental MCF7 breast carcinoma and SK-HEP1 hepatocellular carcinoma cells primarily sensitive to sunitinib were exposed to stepwise increasing doses of sunitinib for &gt;4 months and &gt;7 months, respectively. MCF7-suni and SK-HEP1-suni were shown to grow in the presence of 3-fold IC50 concentrations as compared to parental cells. Mouse xenograft bearing MCF7 were treated with subtoxic doses of sunitinib 2-20mg/kg/day. mRNA levels of a panel of 75 selected genes were evaluated in sensitive and resistant cell lines using q-RT-PCR. Protein phoshorylation (p) was assessed by western-blot analysis.
Results: MCF-7 cells expressed PDGFRA and SK-HEP1 cells expressed PDGFRB, both having low/no baseline levels of VEGFR1-3 and RET mRNA expression. Exposure to 48-hour sunitinib led to IC50s of 5.5µM and 4.5µM in MCF-7 and SK-HEP1, respectively. In SK-HEP1 cells, exposure to sunitinib was associated with a decreased p-AKTS473, p-70S6KT389 and p-ERKT202/Y204. IC50s of sunitinib were 10µM in MCF7-suni and 11 µM in SK-HEP1-suni. Sustained exposure to sunitinib led to &gt;3-fold increased mRNA expression of VEGFC, VEGFR1, VEGFR3, Neuropilin-1, CXCL12, CXCR4, HIF1-alpha, PDGFRA, endothelin-1, RET, and in a lesser extend EG-VEGF in MCF7-suni as compared to parental MCF7. Protracted exposure to sunitinib in SK-HEP1-suni led to a &gt;3-fold increase mRNA expression of VEGFA-D, VEGFR3, CXCL12, CXCR4, PDGFRA, and RET as compared to parental SK-HEP1 cells. At IC50 concentration, p-ERKT202/Y204 was decreased in SK-HEP1-suni cells. To mimic acquired resistance to sunitinib in human, mice bearing MCF7 xenografts were treated using continuous daily dosing of sunitinib until occurrence of tumor progression under therapy occurring around day 20. mRNA expressions were compared in tumors at baseline and at the time of progression. Increased &gt;3-fold mRNA expressions of CXCR4, CXCL12, PDGFRA were observed in progressive xenograft as compared to untreated control tumors.
Conclusions: Our results suggest that acquired in vitro & in vivo resistance of human cancer cells to sunitinib may involve the increased expression of several known targets of sunitinib as well as the expression of other family of receptor involved in tumor angiogenesis, invasion, and metastasis. Further works shall focus in understanding the intriguing role of CXCR4/CXCL12 (SDF-1) in the development of resistance to sunitinib.
Partially granted by FNAB.
Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 366.