Effects of MDM4 Gene Regulation by miR-34a on LOVO Cell Proliferation

This study aims to investigate the effects of regulation of murine double minute protein4 (MDM4) expression by microRNA (miR)-34a on the proliferation of colorectal cancer LOVO cells. Prediction results obtained using a gene microarray showed that MDM4 is a specific miR-34a target gene. The interaction between miR-34a and the 3'-untranslated region (UTR) of MDM4 was detected using a luciferase reporter system. The effect of miR-34a on MDM4 protein expression was detected by Western blotting, and the effect of miR-34a transfection on LOVO cell proliferation was detected using an MTT (3[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay and flow cytometry. The luciferase activity in LOVO cells after addition of pmirGLO-UTR+miR-34a mimic was only 44% of that obtained with pmirGLO-UTR+miR-34a (p<0.01), and the luciferase activity in LOVO cells after addition of pmirGLO-mutUTR+miR-34a was 94% of that observed after pmirGLO-UTR+miR-34a addition (p=0.57). These results indicated that miR-34a interacted with the 3'-UTR of MDM4. Results of Western blotting revealed that MDM4 protein expression level in LOVO cells after addition of miR-34a mimic was 29% that of non-treated LOVO cells (p<0.05), indicating that miR-34a negatively regulates MDM4 protein expression. The growth rate of LOVO cells with miR-34a overexpression was significantly reduced compared with that of non-treated LOVO cells (p<0.05), indicating that miR-34a overexpression inhibits LOVO cell proliferation. miR-34a negatively regulates MDM4 gene expression to inhibit LOVO cell proliferation.