The Expression Patterns and Clinical Significance of microRNAs in Liver Diseases and Hepatocellular Carcinoma

MicroRNAs (miRNAs) are approximately 22-nucleotide noncoding RNAs that constitute silencers of target gene expression and have emerged as key regulatory molecules of mammalian cell functions. Aberrant miRNA expression promotes pathologic conditions including hepatocellular carcinoma (HCC) and a variety of precancerous liver diseases, especially chronic hepatitis B and C, and liver cirrhosis. miRNAs may contribute to HCC development by acting as oncogenes or tumor suppressors. Specific alterations of miRNA expression have also been related to clinical features of HCC, such as stage, differentiation, prognosis, and response to adjuvant therapy. miRNA signatures may help define molecular profiles of liver diseases as biomarkers, and allow classification of different stages of cirrhosis and HCC progression. Either miRNAs, or anti-miRNA oligonucleotides (antagomirs) could be used for in vivo modulation of miRNA actions, and thus have significant potential in molecularly targeted therapy.