Gastroenterology

Gastroenterology

Volume 133, Issue 2, August 2007, Pages 647-658
Gastroenterology

Basic–liver, pancreas, and biliary tract
MicroRNA-21 Regulates Expression of the PTEN Tumor Suppressor Gene in Human Hepatocellular Cancer

https://doi.org/10.1053/j.gastro.2007.05.022Get rights and content

Background & Aims: microRNAs (miRNAs) are short noncoding RNAs that regulate gene expression negatively. Although a role for aberrant miRNA expression in cancer has been postulated, the pathophysiologic role and relevance of aberrantly expressed miRNA to tumor biology has not been established. Methods: We evaluated the expression of miRNA in human hepatocellular cancer (HCC) by expression profiling, and defined a target gene and biologically functional effect of an up-regulated miRNA. Results: miR-21 was noted to be highly overexpressed in HCC tumors and cell lines in expression profiling studies using a miRNA microarray. Inhibition of miR-21 in cultured HCC cells increased expression of the phosphatase and tensin homolog (PTEN) tumor suppressor, and decreased tumor cell proliferation, migration, and invasion. In contrast-enhanced miR-21 expression by transfection with precursor miR-21 increased tumor cell proliferation, migration, and invasion. Moreover, an increase in cell migration was observed in normal human hepatocytes transfected with precursor miR-21. PTEN was shown to be a direct target of miR-21, and to contribute to miR-21 effects on cell invasion. Modulation of miR-21 altered focal adhesion kinase phosphorylation and expression of matrix metalloproteases 2 and 9, both downstream mediators of PTEN involved in cell migration and invasion. Conclusions: Aberrant expression of miR-21 can contribute to HCC growth and spread by modulating PTEN expression and PTEN-dependent pathways involved in mediating phenotypic characteristics of cancer cells such as cell growth, migration, and invasion.

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Cell Lines, Cultures, and HCC Tumor Tissues

Malignant hepatocyte cell lines were obtained from the American Type Culture Collection (Manassas, VA) and cultured as recommended by the supplier. Normal human hepatocytes were obtained from Sciencell (San Diego, CA). For miRNA profiling, total RNA from normal human liver tissue and from HCC was obtained from BioChain Institute, Inc. (Hayward, CA). For miR-21 expression, RNA was obtained from tumor samples with histologic evidence of HCC, and nontumoral samples from adjacent liver without

Expression of miRNAs in HCC

We first isolated and compared the miRNA expression profile from normal liver and HCC tumor tissue (Figure 1). Eight microarray hybridization studies were performed on 3 different pairs of tumor and normal human liver–derived RNA. The miRNAs that are overexpressed differentially in HCC included miR-21, miR-34a, miR-221, miR-213, miR-376a, miR-222, miR-373, miR-210, and miR-294 (Table 1). Of the miRNAs that had decreased expression, the greatest changes were noted for miR-92-1 and miR-199a-1. A

Discussion

Although a role for miRNAs in cancer has been proposed, the molecular mechanisms by which miRNA can modulate tumor growth or metastases are unknown. We show that miR-21 expression is increased in malignant hepatocytes, and in human HCC compared with matching nontumoral tissue. Moreover, we show that miR-21 promotes cell invasion, migration, and growth via repression of PTEN expression and downstream effects involving the phosphorylation of FAK and Akt, and the expression of MMP-2 and MMP-9. The

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    Supported by the Scott and White Hospital Foundation, and by grants DK069370 and CA122694 from the National Institutes of Health.

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