MicroRNA 494 increases chemosensitivity to doxorubicin in gastric cancer cells by targeting phosphodiesterases 4D.

Acquired drug resistance is one of the main limitations in pharmacological therapy of malignancies including gastric cancer. MicroRNAs (miRNAs) are a class of small noncoding RNAs that suppress their targets by binding to the 3'UTR region of genes. In this study, we explored investigate the target gene of miR-494 and its roles in chemoresistance of gastric cancer. We found that miR-494 was significantly down-regulated in gastric cancer cells lines compared to the normal gastric epithelial cell line. Exogenous overexpression of miR-494 increased the chemosensitivity of gastric cancer cells to doxorubicin. Moreover, miR-494 expression was reduced in a doxorubicin-resistant gastric cancer cells (AGS/dox) compared with the parental cells. MTT assay showed that AGS/dox cells exhibited an elevated viability compared with the parental cells. Enforced expression of miR-494 inhibited AGS/dox cell viability and colony formation ability. In addition, we demonstrated that elevated expression of miR-494 inhibited the mRNA and protein expression of phosphodiesterases 4D (PDE4D) in gastric cancer cell. Luciferase assay showed that miR-494 directly targeted the 3'UTR region of PDE4D. Furthermore, restoration of PDE4D recovered the chemoresistance in miR-494-overexpressed gastric cancer cells. Taken together, this study demonstrated that miR-494 enhanced doxorubicin sensitivity via regulation of PDE4D expression, suggesting a novel therapeutic strategy for anti-chemoresistance in gastric cancer.