Abstract 3075: Analysis of microRNA profiles involved in the resistance to trifluridine

Abstract

Abstract Background: Trifluridine (FTD) is a key component of the novel oral antitumor drug trifluridine/tipiracil, which was approved for the treatment of patients with metastatic colorectal cancer refractory to standard chemotherapies. A comprehensive analysis of miRNA profiles was performed in cell lines resistant to FTD established by ourselves, in order to explore the underlying mechanisms of resistance to the drug. Method: We established subline resistance to FTD through continuous administration and increasing dose of the drug for 5 months using the colorectal cancer cell line DLD-1. Total RNA was extracted at intervals whilst establishing FTD resistant sublines, and miRNA expression was analyzed by microarray. The expression of miRNA that was significantly downregulated in the FTD resistant subline was knocked down to test its involvement in resistance to FTD. Cell viability was evaluated by crystal violet cytotoxicity test. Results: The established FTD-resistant sublines showed more than 22-fold higher resistance to FTD and no cross-resistance to 5-FU. miRNA and mRNA clustered in the genome locus located in chromosome 9, 9p22.32 were downregulated in the FTD-resistant cell line, one of which was the miRNA let-7d-5p, which is one of the let-7 family and is known to target oncogenes and several key components of the cell cycle and cell proliferation. Anti-let-7d-5p treated DLD-1 was less sensitive to FTD than compared to control. The IC50 values of FTD were 16.8 µM and 7.6 µM for the anti-let-7d-5p treated cells and control respectively. On the other hand, overexpression of let-7d-5p in DLD-1 using let-7d-5p mimic increased the sensitivity to FTD compared to control. The IC50 values of FTD were 3.7 µM and 13.9 µM in the let-7d-5p overexpression cells and control respectively. 5FU sensitivity was only altered slightly in anti- let-7d-5p treated or let-7d-5p mimic treated cells. These data suggest that let-7d-5p is more relevant to sensitivity for FTD than that of 5FU. Conclusion: Let-7d-5p expression level influenced FTD sensitivity more effectively than 5FU. It suggests that the let-7d-5p is a potential predictive marker for trifluridine/tipiracil treatment in the clinical setting. Citation Format: Kenta Tsunekuni, Jun Koseki, Masamitsu Konno, Ayumu Asai, Norihiro Nishida, Hugh Colvin, Koichi Kawamoto, Yuichiro Doki, Masaki Mori, Hideshi Ishii. Analysis of microRNA profiles involved in the resistance to trifluridine [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 3075. doi:10.1158/1538-7445.AM2017-3075