Abstract 3814: Overcoming multidrug resistance (MDR) in colorectal cancer by modulating exosome-mediated transfer of MDR transporter regulatory machineries
Authors: To Kenneth KW , Tong Christy WS , Wu Mia MX , Yan Wei 
Published: August 2019

Abstract
Aim: The study aims to investigate the circumvention of multidrug resistance (MDR) in colorectal cancer by modulating exosome-mediated transfer of MDR transporter regulatory machineries from resistant to sensitive cells. Background: Colorectal cancer is a leading cause of cancer related death worldwide. MDR is a major unresolved obstacle to successful cancer chemotherapy in colorectal cancer. It is most commonly associated with an increased efflux of anticancer drugs by MDR transporters including ABCG2. Exosomes are a unique form of extracellular lipid vesicles, which are released upon the fusion of multivesicular bodies with plasma membranes on cell surface. Tumor-derived exosomes are emerging as important cell-to-cell couriers of oncogenic materials through the horizontal transfer of mRNAs, microRNAs or proteins during tumorigenesis. Recently, tumor-derived exosomes have been reported to mediate the transfer of the drug resistance phenotype. We hypothesize that regulatory machineries of MDR transporters may be transferred via exosomes from drug resistant donor cells to sensitive recipient cells, thereby conferring spread of MDR. Method: Exosome-mediated transfer of selected regulatory mediators from ABCG2-overexpressing resistant S1M180 cells to the parental S1 colorectal cancer cell line was evaluated. Exosomes were isolated from S1M180 cells-conditioned medium by the standard differential centrifugation method. The secretion of ABCG2-regulatory microRNAs into exosomes by S1M180 was studied by microRNA microarray. The uptake of fluorescence-labeled exosome from S1M180 cells by S1 cells was visualized by fluorescence microscopy. The alteration of a newly identified miR-203-DNMT3b-ABCG2 regulatory pathway in the recipient sensitive cells after incubation with exosomes derived from the resistant cells was examined by qPCR and Western blot analysis. Result: Exosomes were successfully isolated from ABCG2-overexpressing S1M180 cells and confirmed by the expression of exosomal markers CD63 and HSP70. S1M180-derived exosomes increased the viability of the parental S1 cells upon treatment with SN38 or 5-fluorouracil. After incubation with S1M180-derived exosomes, remarkably higher expression of miR-203 but lower expression of DNMT3b was found in the parental S1 cells, presumably leading to the induction of ABCG2 to mediate the transferred resistance phenotype. Inhibition of exosome uptake by a putative inhibitor dynasore was found to prevent ABCG2 induction and re-sensitize the exosome-treated parental cells to SN38 treatment.Conclusion: MDR cells-derived exosomes may spread the drug resistance phenotype by transferring the miR-203-DNMT3b-ABCG2 regulatory machinery to sensitive cells. Inhibition of this exosomal transfer of regulatory materials may prevent the spread of MDR and sensitize cancer cells to chemotherapy.
Citation Format: Kenneth KW To, Christy WS Tong, Mia MX Wu, Wei Yan. Overcoming multidrug resistance (MDR) in colorectal cancer by modulating exosome-mediated transfer of MDR transporter regulatory machineries [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3814.