Abstract 2588: Restoring downregulated microRNAs miR-195-5p and miR-497-5p increases sensitivity to chemotherapy in colorectal cancer cells
Authors: Boyd Lenka N. , Poel Dennis , Schelfhorst Tim , Pham Thang V. , Piersma Sander R. , Knol Jaco C. , Jimenez Connie R. , Verheul Henk M. , Buffart Tineke E. 
Published: August 2019

Abstract
Background: Patients with advanced colorectal cancer (CRC) are commonly treated with systemic combination therapy, however the success of treatment is hampered by drug resistance. MicroRNAs (miRNAs) have recently emerged as important players in therapy resistance in CRC. The aim of this study was to improve therapy efficacy by sensitizing CRC cells to the chemotherapeutics currently used in clinical practice for patients with advanced CRC by restoring downregulated miR-195-5p and miR-497-5p.
Methods: Sensitivity to 5FU, oxaliplatin (OHP) and irinotecan before and after transfection with miR-195-5p and miR-497-5p mimics was analyzed using tetrazolium reduction and clonogenic assays in CRC cell lines HCT116, RKO, DLD1 and SW480. Transfection with cel-miR-39-3p and untransfected cells were used as controls. Proteomic analyses of transfected and untransfected cells were implemented to identify possible targets involved in sensitivity to chemotherapy. Group comparisons by beta-binomial statistics were performed to analyze significantly altered peptides after restoring miRNA expression.
Results: After transfection with miR-195-5p and miR-497-5p mimics, RKO showed an increased sensitivity to OHP (IC50 decreased from 1100 nM to 900 nM and 800 nM, respectively) and HCT116 showed increased sensitivity to OHP (IC50 decreased from 600 nM to 200 nM and 180 nM, respectively) and 5FU (IC50 decreased from 3500 nM to 2900 nM and 2800 nM, respectively). No increased sensitivity to irinotecan was observed. Clonogenic assay revealed that HCT116 formed 20% and 50% less colonies when treated with 5FU after transfection with miR-195-5p and miR-497-5p mimics, respectively, and 60% less colonies when treated with OHP after transfection with either mimic. RKO showed a 20% decrease in colonies when treated with OHP after transfection with miR-497-5p mimic. No differences in sensitivity to OHP, 5FU or irinotecan were found in transfected SW480 and DLD1. Unsupervised clustering of the proteome showed that HCT116 and RKO cells transfected with miR-195-5p and miR-497-5p mimics could be distinguished from the cells transfected with a control mimic and the untransfected cells. Transfected and control SW480 and DLD1 could not be distinguished based on the proteome profiles. In the combined analyses of HCT116 and RKO 12 peptides showed significantly altered expression (FDR&lt;0.1) after transfection. No significantly altered peptides were detected in transfected SW480 and DLD1 cell lines.
Conclusion: Restoring miR-195-5p and miR-497-5p expression enhanced sensitivity to OHP in HCT116 and RKO cells and to 5FU in HCT116 cells. Proteomics revealed 12 peptides with significantly altered expression after restoring expression of these miRNAs. Treatment with miRNA mimics to sensitize tumor cells to chemotherapy could be an alternative systemic treatment strategy for patients with advanced CRC.
Citation Format: Lenka N. Boyd, Dennis Poel, Tim Schelfhorst, Thang V. Pham, Sander R. Piersma, Jaco C. Knol, Connie R. Jimenez, Henk M. Verheul, Tineke E. Buffart. Restoring downregulated microRNAs miR-195-5p and miR-497-5p increases sensitivity to chemotherapy in colorectal cancer cells [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 2588.