miR-145 mediates the antiproliferative and gene regulatory effects of vitamin D3 by directly targeting E2F3 in gastric cancer cells

VitaminD3 signaling is involved in inhibiting the development and progression of gastric cancer (GC), while the active vitamin D metabolite 1-alpha,25-dihydroxyvitamin D3 (1,25(OH)₂D₃)-mediated gene regulatory mechanisms in GC remain unclear. We found that miR-145 is induced by 1,25(OH)₂D₃ in a dose- and vitamin D receptor (VDR)- dependent manner in GC cells. Inhibition of miR-145 reverses the antiproliferative effect of 1,25(OH)₂D₃. Furthermore, miR-145 expression was lower in tumors compared with matched normal samples and correlated with increased the E2F3 transcription factor protein staining. Overexpression of miR-145 inhibited colony formation, cell viability and induced cell arrest in S-phase in GC cells by targeting E2F3 and CDK6. miR-145 inhibition consistently abrogates the 1,25(OH)₂D₃-mediated suppression of E2F3, CDK6, CDK2 and CCNA2 genes. Altogether, our results indicate that miR-145 mediates the antiproliferative and gene regulatory effects of vitamin D3 in GC cells and might hold promise for prognosis and therapeutic strategies for GC treatment.