Abstract 2045: Exploring the potential of cellular thermal shift assay (CETSA) to study drug resistance during cancer therapy

Abstract

Abstract The aim of this project is to understand the various mechanisms contributing to drug resistance development in cancer therapy. The efficacy of therapeutics is dependent on a drug binding to its target. We have developed a method that allows for the first time to directly evaluate drug binding to target proteins in cells and tissue samples the cellular thermal shift assay (CETSA) (Martinez Molina et al. Science, 341:84). CETSA is based on the biophysical principle of ligand-induced thermal stabilization of target proteins. By monitoring the drug occupancy in the target protein, CETSA can be used to study processes of drug transport and metabolism in cancer cells. We have used CETSA to study the acquired drug resistance of, antifolate and fluropyrimidine drugs in pairs of parental and resistant cell lines. CETSA shifts and isothermal dose response fingerprint (ITDRF) were used to study the relative drug target engagement in these cells. Quantitative mass spectrometry was used to monitor differences in protein expression levels across the cell lines. Based on the CETSA measurements, resistant cells clearly showed a higher drug dose threshold as compared to the parent cell lines, typically requiring 8-50 times higher dose to establish similar target engagement. Several potential mechanism for drug resistant emerged - we, for example, observed up-regulation of thymidylate synthase and down regulation of reduced folate carrier (RFC) protein associated with antifolate transport, in some resistant cell lines. The data supports that CETSA is a potential valuable tool to dissect various mechanisms those contribute to resistant development in cancer cells. Citation Format: Lekshmy Kunjamma Usha Sreekumar, Yan Ting Lim, Saranya Veerappan, Par Nordlund. Exploring the potential of cellular thermal shift assay (CETSA) to study drug resistance during cancer therapy [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 2045. doi:10.1158/1538-7445.AM2017-2045