Tu1900 MiR-1246 and Mir-302 Are Novel Targets of Epigenetic Therapy With Dznep and SAHA in Human Cancer Cells

Abstract

Introduction Epigenetic therapy with DNA methylation inhibitors and histone deacetylase (HDAC) inhibitors holds clinical promise for the treatment of human malignancies. MicroRNAs (miRNAs) are small non-coding RNAs that function as endogenous silencers of various target genes and play critical roles in cancer. We have proposed that epigenetic activation of tumor suppressor miRNAs can be a novel therapeutic approach for human cancers (Cancer Cell 9: 435, 2006). Recently, 3-deazaneplanocin A (DZNep) was discovered to inhibit a polycomb group protein, enhancer of zeste homologue 2 (EZH2), which has activity for trimethylation of histone H3K27. To investigate the molecular mechanisms underlying the effect of epigenetic therapy with DZNep and the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) against human cancer, miRNA expression profiles were analyzed. Materials and Methods AGS human gastric cancer cells and HepG2 human liver cancer cells were treated with DZNep and SAHA. MiRNA expression profiles were analyzed by microarray analysis and TaqMan quantitative RT-PCR. Cell proliferation was analyzed by cell counting, and target genes of miRNAs were analyzed by Western blotting. Levels of apoptosis and the cell cycle were analyzed by flow cytometry. Results The results of microarray and quantitative RT-PCR analyses revealed that miR-1246 was up-regulated by treatment with DZNep in both AGS and HepG2 cells, and that miR-302 was up-regulated by treatment with SAHA in AGS cells. Treatment with DZNep or SAHA reduced the cell proliferation activity of both AGS and HepG2 cells, and this reduction was more marked when both drugs were used in combination. The anti-apoptotic factor DYRK1A, which was recently identified as one of the targets of miR-1246, was significantly suppressed by treatment with DZNep and SAHA, resulting in apoptosis of AGS andHepG2 cells. In addition, treatment of AGS cells with DZNep and SAHA suppressed CDK2 and BMI-1, which were recently identified as the targets of miR-302, inducing cell cycle (G1/S) arrest of AGS cells. Conclusions These findings suggest that DZNep is a promising drug for the treatment of gastric and liver cancers via activation of miR-1246. DZNep and SAHA may synergistically suppress the proliferation of gastric cancer cells via activation of miR-1246 and miR-302. MiR-1246 and miR-302 are novel targets of epigenetic therapy with DZNep and SAHA in human cancer cells.