Analysis of sequence variations in 59 microRNAs in hepatocellular carcinomas.

It is well demonstrated that mutations in protein-coding genes play a key role during carcinogenesis. Whether sequence variations in microRNA genes are also associated with tumorigenesis is still unknown and thus require extensive investigations. In the present study, genomic sequences coding for the precursors of 59 microRNA genes were analyzed in both hepatocellular carcinoma (HCC) tissues and liver cancer derived cell lines. In total, four variations in three microRNAs, including miR-106b, miR-192 and let-7a-2, were found in four out of 96 HCC tissues. Further investigation in the corresponding adjacent non-cancerous tissues identified the same sequence variations, suggesting the possibility of germline mutations or natural polymorphisms. Moreover, no variation was found in eight liver cancer derived cell lines. Among four sequence alterations observed in this study, two were located in miR-106b and identified as known single nucleotide polymorphisms, while the other two found in miR-192 and let-7a-2 had not been reported before. In conclusion, our data suggest that mutation of microRNA is a rare event in HCC and thus may not represent a main mechanism underlying hepatocarcinogenesis.