The loss of miR–198 is crucial for development and progression of hepatocellular carcinoma

Aims: miRNA are small, non-coding RNA molecules regulating gene expression post-transcriptionally. Recently, we have demonstrated that miRNA–198 (miR–198) is significantly down regulated in HCV-positive hepatocellular carcinoma (HCC), affecting markedly cell growth of hepatoma cells. Methods: In order to identify potential pathways of miR–198 function, we transfected hepatoma cells (Huh7) with miR–198. Subsequently, we performed a comprehensive analysis of expression profiles in miR–198 over expressing hepatoma cells using hybridisation microarrays from Affymetrix (San Diego, USA). For bioinformatic interpretation and validation of the array hybridisation results, we used different Spotfire based software programs followed by Real-Time PCR quantification of selected transcripts. Promising miR–198 target transcripts were cloned and, analyzed by reporter assays. Additionally, immunoblot analyses and cell monolayer scratching assays were carried out in order to show the miR–198 influence on migration. Results: Extensive analyses of expression profiles in hepatoma cells, treated with miR–198, revealed a prominent impact of miR–198 on various pathways such as, the insulin growth factor signalling pathway, the transforming-growth factor-β pathway, and the Wnt signalling pathway. Further bioinformatic investigation pointed out that miR–198 may affect cell growth, differentiation, angiogenesis, and cell migration. In agreement with these data, we were able to demonstrate that the loss of miR–198 was involved in the repression of the cellular adherence protein E-cadherin, resulting in increased capabilities of hepatocellular carcinoma cells to migrate. Conclusion: In silico and in vitro experiments revealed that miR–198 is a crucial tumor suppressor miRNA, inhibiting hepatocarcinoma cell growth and migration by its influence on central signalling pathways.