Abstract 3508: Inhibition of EZH2 overcomes resistance to sunitinib in clear cell renal cell carcinoma models
Authors: Adelaiye-Ogala Remi M. , Chintala Sreenivasulu , Shen Li , Orillion Ashley , Ciamporcero Eric , Elbanna May , Miles Kiersten Marie , Gillard Bryan , Buck Michael , Pili Roberto 
Published: August 2015

Abstract
Background: Alterations in epigenetic mechanisms including histone modification and hyper-methylation at gene promoter regions have been implicated as mechanisms of drug resistance in cancer. Alternation of epigenetic regulators such histone methyltransferase, EZH2, has been reported in numerous cancer types including advanced renal cell carcinoma (RCC). Previous studies suggest that sunitinib may have a direct anti-tumor effect and that acquired sunitinib resistance may be induced in tumor cells rather than just in endothelial cells. In our study, we investigated the role of EZH2 in sunitinib resistance in clear cell renal cell carcinoma. Methods: Human RCC cell lines 786-0 were treated and exposed to increasing concentrations of sunitinib to develop a resistant cell line, 786-0R. Parental and resistant cell lines were treat with either sunitinib, GSK126 (EZH2 inhibitor) or both. In parallel, EZH2 was knocked down in 786-0 cells and exposed to increasing concentrations of sunitinib. Cell viability was quantitated by absorbance of crystal violet stained cells using a spectrometer at 570nm. In a second set of experiments, control and treated cells were collected for western analysis. Mice bearing human ccRCC patient derived xenograft (PDXs); RP-R-01, RP-R-02 and RP-R-02LM (a metastatic ccRCC model established from RP-R-02) were implanted into SCID mice either subcutaneously or orthotopic in the kidney (sub-renal). When tumors reached an average volume of 50mm3, mice were randomly grouped into 2 arms; control and sunitinib treatment (40mg/kg, 5days/week). Tumors volumes and body weight were assessed once per week. Tumor tissues and lungs were collected for immunohistochemistry analysis. All assessments and quantification were done blindly. Results: Our in vitro and in vivo data showed an increased expression of EZH2 with resistance to sunitinib. Furthermore, inhibition of EZH2 in our in vitro studies correlated with a significant decrease in the anti-tumor effect of sunitinib in both parental and resistant cell lines. Conclusion: Overall our data suggest the potential role of epigenetic alterations, specifically EZH2 overexpression and its association with resistance to sunitinib. We are currently assessing the effect of EZH2 inhibition with sunitinib resistance in our in vivo system using metastatic ccRCC PDX models.
Citation Format: Remi M. Adelaiye-Ogala, Sreenivasulu Chintala, Li Shen, Ashley Orillion, Eric Ciamporcero, May Elbanna, Kiersten Marie Miles, Bryan Gillard, Michael Buck, Roberto Pili. Inhibition of EZH2 overcomes resistance to sunitinib in clear cell renal cell carcinoma models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3508. doi:10.1158/1538-7445.AM2015-3508