The shSUV39H1 group showed a significantly reduced tumor size, as compared to the control, as shown by the bioluminescence and gross tumor size of the excised livers (Fig. 5B and Supporting Fig. 3). Most important, SUV39H1 knockdown abolished pulmonary and lymph node metastasis of HCC cells, as shown by the bioluminescence of the excised tissues and histological analysis (Fig. 5C, D). Our in vivo data were consistent with the in vitro data and further strengthened the biological importance
of SUV39H1 in liver cancer development. Increasing findings demonstrated that dysregulation of miRNA accounts for aberrant gene expression in human cancers. Therefore, we explored the possible relationship between miRNA deregulation and SUV39H1 up-regulation in human HCC. In silico analysis by TargetScan, Pictar, and Miranda miRNA target prediction algorithms revealed that the 3′ UTR sequence of SUV39H1 contains putative binding sites for multiple Ensartinib molecular weight miRNAs (Supporting Fig. 4). Among the predicted miRNAs, miR-125b is the only miRNA that is significantly down-regulated
in human HCC (Supporting Fig. 5).22,23 The complementary binding between miR-125b and SUV39H1 3′ UTR is kinetically stable and evolutionarily conserved, as illustrated by the diagram of RNA hybrid and sequence alignment among various animal species, respectively (Fig. 6A). Hence, selleck kinase inhibitor we hypothesized that up-regulation of SUV39H1 in HCC may attribute to the loss of miR-125b. To confirm the binding between miR-125b and SUV39H1 3′ UTR, the luciferase reporter assay was performed using the WT or mutated
SUV39H1 3′-UTR-coupled luciferase reporter (Fig. 6B). We found that ectopic expression of miR-125b precursor significantly decreased the luciferase signal of WT SUV39H1 3′ UTR, as compared to the empty vector control. This suppressive effect was abolished when the putative miR-125b-binding site was mutated (Fig. 6C). Furthermore, miR-125b-overexpressing HCC cells showed a profound reduction of endogenous SUV39H1 expression at both messenger RNA (mRNA) and protein levels (Fig. 6D, E). Consistent results were obtained from BEL7402 and Huh-7 cells, which confirmed the negative regulation of SUV39H1 by miR-125b. Most important, expressions of PIK-5 SUV39H1 and miR-125b were inversely correlated in our clinical HCC and non-tumorous liver samples (R = −0.364, P = 0.001; Fig. 6F). Taken together, our data suggested that SUV39H1 up-regulation is contributed by the underexpression of miR-125b in HCC. Epigenetic dysregulation is one of the most common abnormalities observed in human cancers. Some well-characterized examples of cancer epigenetic changes include DNA hypermethylation on the promoter regions of tumor suppressors and global changes in histone modifications. Histone modifications are known to have profound effects on chromosome stability and gene transcription. Yet, the underlying mechanism of these epigenetic alterations remains largely unknown.