Recent advances of miRNA involvement in hepatocellular carcinoma and cholangiocarcinoma

MicroRNAs (miRNAs), which are a class of highly evolutionarily conserved non-coding RNAs, modulate gene expression and are regulated by specific genes. Several studies have shown that the expression of miRNAs is deregulated in Hepatitis C virus (HCV) & Hepatitis B virus (HBV) infection, liver cancer progression, tumor invasion and metastasis. There are a number of high-quality review articles relative to the general role of miRNA alterations in carcinogenesis and specific reviews dealing with the miRNA changes in hepatocellular carcinoma (HCC) and cholangio-carcinoma (CCA). Since primary liver cancer is predominantly comprised of HCC and intrahepatic cholangiocarcinoma (ICC), in the present review we specifically focus on recent advances of miRNAs related to tumorigenesis, invasion and metastasis of primary liver cancer, with special emphasis on their relationships to their target genes. HCV & HBV are major causes of liver disease, including acute and chronic hepatitis, liver cirrhosis, and HCC, while HCV infection is a risk factor for ICC. We also discuss the mi-RNA alterations involved in HCV & HBV infection. We briefly describe advances in molecular signaling of miRNAs in liver cancers and present insights into new therapeutic clues that target liver cancer.