Aberrantly Expressed MicroRNAs Involved In Hepatocellular Carcinoma And Their Function, Targets And Therapeutic Potential

Objective Hepatocellular carcinoma (HCC) is a worldwide human malignancy with high morbidity and mortality but lack of effective targeted therapies. Current diagnosis biomarkers of HCC are maily depend on alpha-fetoportien (AFP), but 20%to 40%HCC patients'AFP was negative or low positive. Up to now, surgical resection or liver transplantation remains the first choice for the treatment of HCC; however, only about 20% of patients with HCC are eligible for surgical intervention at the time of diagnosis. Moreover, patients who underwent curative resection often have a high frequency of relapse, and postoperative 5-year survival is only 30%-40%. The outcomes of HCC patients are still so dismal due to our limited knowledge in its molecular pathogenesis, the difficulty in detecting the disease at its early stages and the lack of effective therapeutics. Therefore, studies aimed at the definition of the mechanisms associated with hepatocarcinogenesis, identification of new biomarkers for early diagnosis and development of more effective therapeutic interventions are urgently needed. MiRNAs are evolutionarily conserved, small noncoding RNAs that are believed to play fundamental roles in various biological processes through regulation of gene expression at the level of post-transcription. Alterations in miRNA expression can modulate key cellular processes involved in tumorigenesis; so systematic evaluation of changes in global miRNA expression in phenotypically defined tumors could provide insight into basic mechanisms of tumor formation and progression. In this report, we systematically studied the aberrantly expressed miRNAs involved in HCC through the comparison of miRNA expression profiling in cancerous hepatocytes with that in normal primary human hepatocytes and emphasized the functions, targets and therapeutic potential of these aberrantly expressed miRNAs.Methods The expression profiles containing 723 human miRNAs were determined in 7 liver cancer cell lines and 3 cases of normal primary human hepatocytes (PHHC) using Agilent human miRNA array (Version 2). MiRNA expression profiles of cancerous hepatocytes were compared with that of normal hepatocytes to indentify the aberrantly expressed miRNAs. These results were further confirmed by TaqMan qRT-PCR. To assess the role of dysregulated miRNAs in hepatocarcinogenesis, hepatoma cell lines were transfected with pre-miRNAs, anti-miRNAs or their matched negative control and further tested by cell proliferation, cell cycle and apoptosis, clonogenicity, cell migration and invasion assaies. The putative miRNA targets were predicted by using algorithms miRBase, TargetScan and PicTar and verfied by SYBR Green qRT-PCR, Western Blot Analysis and Luciferase Assay. The model of hepatoma xenografts in nude mice was established to explore the therapeutic potential of antisense-mediated inhibition of oncogenic miRNAs or replacement therapy of tumor suppressor miRNAs for HCC.Results we reported a previously unrecognized paradigm for identifying aberrantly expressed miRNAs involved in HCC through the comparision of miRNA expression profiling in cancerous hepatocytes with that in normal hepatocytes.37 dysregulated miRNAs were screened out by 2-fold change with a significant difference (P< 0.05). Furthermore, we demonstrated that both up-regulated miR-221 and down-regulated miR-375 were involved in hepatocarcinogenesis by modulating cell cycle, proliferation, apoptosis, invasion and clone formation. Mir-221 targets three tumor suppressors-BMF, BBC3, ANGPTL2, and functions as an oncogene, while miR-375 targets two oncogenes-LAMC1, PDGFC, and functions as a tumor suppressor. Therapeutic modulation by lentivirus-mediated-anti-miR-221 or cholesterol modified miR-375 mimics can significantly suppress the growth of hepatoma xenografts in nude mice.Conclusions We emphasized that HCC-related miRNAs identified by comparison of the expression profiling of miRNAs in liver cancer cell lines versus normal hepatocytes could be more representative and informative in hepatocarcinogenesis. Furthermore, our findings highlight the therapeutic potential of lentivirus-mediated-anti-miR-221 and cholesterol modified miR-375 for HCC. With all these results, we believe that the field of microRNA based diagnosis and therapeutics has incredible promise in the fight against HCC.