MicroRNA and hepatocellular carcinoma: biology and prognostic significance

Hepatocellular carcinoma (HCC) is the most common primary liver cancer and the third most common cause of cancer-related death worldwide. In 90% of cases, HCC arises on a background of cirrhosis which, in turns, results from hepatitis (HBV and HCV) infections, alcohol abuse, metabolic disorders including NASH, and genetic metabolic diseases, autoimmune hepatitis, primary biliary cirrhosis and exposure to environmental carcinogens. The molecular mechanisms underlying HCC development are still only partially known. Despite a high molecular variability, the deregulation of definite oncogenic pathways has been confirmed as a common finding in HCC. Among these, the molecular ways controlling proliferation, apoptosis and migration play a major role. In recent years, a new class of regulatory RNAs, the microRNAs, has been discovered and their deregulated expression has been linked to the molecular pathogenesis of many cancers because of their ability to strongly impact on the expression of crucial messenger RNAs. This review focuses on some of the most relevant evidence concerning the contribution of microRNA aberrant expression to HCC development.