MicroRNA expression in hepatitis C virus-related malignancies: A brief review

Not only is chronic hepatitis C virus (HCV) infection a major public health problem, but also it can cause hepatocellular carcinoma and, more rarely, non-Hodgkin's lymphoma. These characteristics mean that HCV is the only virus infecting humans that is able to cause two different cancers. The fine pathogenetic and molecular mechanisms by which HCV induces these two malignancies are not completely clear. In the last decade, it has been shown that microRNAs (miRNAs), a class of 21-23-nucleotide molecules modulating post-transcriptional gene expression, make an important contribution to the pathogenesis of several cancers and are also considered highly promising biomarkers. Here, we briefly describe the current knowledge about microRNAs' involvement in HCV-related molecular oncogenesis. We decided to focus our attention on studies fully conducted on ex vivo samples with this specific etiology, and on cultured cell lines partially or completely expressing the HCV genome. Some of the results reported in this review are controversial, possibly because of methodological issues, differences in sampling size and features, and ethnicity of patients. What is certain is that miRNAs play a remarkable role in regulating gene expression during oncogenetic processes and in viral infection. A clear understanding of their effects is fundamental to elucidating the mechanisms underlying virus-induced malignancies.