G alpha(12) gep oncogene deregulation of p53-responsive microRNAs promotes epithelial-mesenchymal transition of hepatocellular carcinoma

Abstract

Hepatocellular carcinoma (HCC) has a poor prognosis owing to aggressive phenotype. G alpha(12) gep oncogene product couples to G-protein-coupled receptors, whose ligand levels are frequently increased in tumor microenvironments. Here, we report G alpha(12) overexpression in human HCC and the resultant induction of zinc-finger E-box-binding homeobox 1 (ZEB1) as mediated by microRNA deregulation. G alpha(12) expression was higher in HCC than surrounding non-tumorous tissue. Transfection of Huh7 cell with an activated mutant of G alpha(12) (G alpha(12)QL) deregulated microRNA (miRNA or miR)-200b/a/429, -194-2/192 and -194-1/215 clusters in the miRNome. cDNA microarray analyses disclosed the targets affected by G alpha(12) gene knockout. An integrative network of miRNAs and mRNA changes enabled us to predict ZEB1 as a key molecule governed by G alpha(12). Decreases of miR-200a/b, -192 and -215 by G alpha(12) caused ZEB1 induction. The ability of G alpha(12) to decrease p53 levels, as a result of activating protein-1 (AP-1)/c-Jun-mediated mouse double minute 2 homolog induction, contributed to transcriptional deregulation of the miRNAs. G alpha(12)QL induced ZEB1 and other epithelial-mesenchymal transition markers with fibroblastoid phenotype change. Consistently, transfection with miR-200b, -192 or -215 mimic prevented the ability of G alpha(12)QL to increase tumor cell migration/invasion. In xenograft studies, sustained knockdown of G alpha(12) decreased the overall growth rate and average volume of tumors derived from SK-Hep1 cell (mesenchymal-typed). In HCC patients, miR-192, -215 and/or -200a were deregulated with microvascular invasion or growth advantage. In the HCC samples with higher G alpha(12) level, a correlation existed in the comparison of relative changes of G alpha(12) and ZEB1. In conclusion, G alpha(12) overexpressed in HCC causes ZEB1 induction by deregulating p53-responsive miRNAs, which may facilitate epithelial-mesenchymal transition and growth of liver tumor. These findings highlight the significance of G alpha(12) upregulation in liver tumor progression, implicating G alpha(12) as an attractive therapeutic target.