miR-145 restoration overcomes oxaliplatin resistance via ABCC1 in colorectal cancer.

Abstract

BACKGROUND: Drug resistance limits effectiveness of chemotherapy in colorectal cancer (CRC). Consequently, finding appropriate strategies for re-sensitizing chemo-resistant cells is crucial. Our present study aimed at taking advantage of chemotherapy and gene therapy by restoring microRNA-145 expression in oxaliplatin resistant CRC cells. METHODS: Bioinformatic analysis of clinical CRC datasets demonstrated significantly reduced miR-145 expression in tumor tissues compared with normal samples. Oxaliplatin-resistant SW-480 cells were generated and transfected with a pCMV-miR-145 expression vector. The MTT assay was used to assess cell viability following miR-145 restoration, oxaliplatin treatment, or their combination. Apoptosis was measured via flow cytometry. Gene expression levels of ABCC1, MDR1, K-RAS, MMP-13, Bcl-2, CASP3, CASP8, and CASP9 were analyzed using qRT-PCR, and ABCC1 protein expression was evaluated by western blotting. Cell migration was assessed using a wound-healing assay. RESULTS: Co-treatment with miR-145 and Oxaliplatin significantly reduced cell viability, proliferation, and migration and increased apoptosis compared to the either treatments. Restoring miR-145 expression downregulated reduced the drug-resistance genes ABCC1 and MDR1, and reduced decreased expression of oncogenes including K-RAS and Bcl-2, while increasing expression of apoptosis-related genes (CASP3, CASP8, and CASP9). CONCLUSION: miR-145 restoration via decreasing the drug resistance biomarkers ABBCC1 and MDR1, along with other oncogenes like K-Ras and Bcl2, and increasing apoptosis conductors could sensitize oxaliplatin-resistant cells to chemotherapy. This proposes a novel and clinically translatable strategy to control drug resistance in CRC, finding new ways to increasing chemotherapeutic efficacy.