MicroRNA-125b Functions As A Tumor Suppressor In Hepatocellular Carcinoma Cells

MicroRNAs (miRNAs) are small, about20-24nucleotide and non-codingRNAs found in various tissue and have a broad impact on gene expression throughpost-transcriptional suppression or translational repression. miRNAs have beenfound to play important roles in multiple biological processes, such as development,cellular proliferation, differentiation and divers diseases. Recent studies showed thatdsyregulation of miRNAs was currently linked to tumorigenesis and indicated thatmiRNAs could work as tumor suppressors and oncogenes. Therefore, it is of greatimportance to focus on the expression and function of miRNAs, associated withtumor formation and progression.Hepatocellular carcinoma (HCC) is the most common malignancy of liver withhigh rates in all over the worldwide, which is a complex disease involvingchromosomal instability and expression abnormalities of both coding andnon-coding genes. MiRNAs is a kind of noncoding genes and abnormal expressionof miRNA is often associated with hepatocarcinogenesis. Northern Blot analysiswas performed to analyze the expression of a few potential miRNAs in HCC tissuesand HCC cell lines. We found that miR-125b, located at chromosome11,remarkably down-regulated in HCC.To inspect the expression of miR-125b in HCC, a Northern blot analysis of6pairs of HCC patient tissues was conducted. The expression of miR-125b was remarkably lower in HCCs compared with matched normal tissues. Furthermore,another Northern blot was performed to analyze miR-125b expression in3differentHCC cell lines (HepG2, SMMC7721and Huh7) showed that expression ofmiR-125b was also down-regulated in all cell lines. Therefore, we infer from theseresults that decrease of miR-125b expression is a frequent event in human HCC andmight be work as a common and typical anti-onco-miRNA in tumor formation andprogression. To analyze the function of miR-125b in hepatocarcinogenesis, we builta cell module of over-express miR-125b by transfecting miR-125b mimic. Theresults showed that over-expression of miR-125b significantly suppressedproliferation and cell cycle of HepG2and SMMC7721, which indicated that themiR-125b might tend to restrain HCC cell growth. Potential targets of miR-125bwere predicted and confirmed by bioinformatics tools and dual reporter gene assay.Then, we certify that Mcl-1and IL6R, high express in hepatocarcinogenesis, wastwo of the targets of miR-125b in HCC. We reasoned that miR-125b play as ananti-onco-miRNA in HCC proliferation and cell cycle by targeting Mcl-1and IL6Rdirectly.To demonstrate the conjecture, rescued assay was adopted to illuminate it.After transfecting expression vector of Mcl-1and IL6R in HepG2cell treated withmiR-125b mimic previously, we found that the expression of Mcl-1and IL6R showgreat increase. Meanwhile, S phase cell was observed grow in number. The resultsindicate that miR-125b indeed play as a anti-onco-miRNA in cell proliferation andcell cycle of HCC through suppressing the expression of Mcl-1and IL6R.Taken together, these results suggest that miR-125b and its targets constitute agreat complex regulatory network, which play very important roles in Occurrenceand development of HCC. We can propose that suppression of mir-125b may be anovel approach for the treatment of HCC.