Abstract:

Objective To evaluate the effect of miR-140-5p on the 5-FU sensitivity of SW480 cells and 5-FU-resistant SW480 cells，and to explore whether the effects of miR-140-5p involve Nrf2. Methods We constructed the 5-FU-resistant cell line SW480/5-FU from SW480 colon cancer cells. Expression of miR-140-5p was detected using qRT-PCR，and sensitivity of the two cell lines to 5-FU was measured using the CCK-8 and cell colony formation assays. Possible relationships between miR-140-5p and Nrf2 expression were explored using qRT-PCR，Western blotting and a dual-luciferase reporter gene assay. The involvement of Nrf2 in regulation of 5-FU-resistance by miR-140-5p was tested in CCK-8 and cell colony formation assays. Results SW480/5-FU cells showed strong 5-FU resistance，which qRT-PCR linked to much lower miR-140-5p expression. CCK-8 and cell colony formation assays showed that miR-140-5p expression correlated with significantly higher 5-FU sensitivity in SW480/5-FU cells. The combination of qRT-PCR，Western blotting and dual-luciferase reporter gene assays suggested that miR-140-5p binds directly to Nrf2 and inhibits it. Overexpression of Nrf2 in SW480/5-FU cells rescued 5-FU sensitivity，based on CCK-8 and cell colony formation assays. Conclusion It appears that miR-140-5p expression is associated with higher 5-FU sensitivity in SW480 cells，and that miR-140-5p sensitizes cells by binding and inhibiting Nrf2.

Key words: Colon neoplasms, miR-140-5p, Nrf2, 5-FU, Resistant