ABSTRACT
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.
