Background:Recently, microRNAs in cancer development have attracted much attention, but their roles in tumorigenesis are still largely unknown. In this study, a functional role of miR-22 in hepatocellular carcinoma (HCC) development has been identified.Methods:Quantitative real-time PCR was used to determine the level of miR-22 transcript in HCC clinical samples, and its correlation with disease-free survival was determined using Kaplan–Meier method. Restoration of miR-22 expression was carried out in HCC cell lines to assess its influence on HCC cell proliferation and tumourigenicity.Results:In the 160 paired HCC tissue samples, miR-22 expression was downregulated in HCC, and low miR-22 expression in HCC was predictive of poor survival in HCC patients. Functional studies indicated that ectopic expression of miR-22 significantly inhibits HCC cell proliferation and tumourigenicity. Furthermore, histone deacetylase 4 (HDAC4), known to have critical roles in cancer development, was proved to be directly targeted and regulated by miR-22. Furthermore, HDAC4 was upregulated in miR-22-downregulated HCC tissues, suggesting that downregulation of miR-22 might participate in HCC carcinogenesis and progression through potentiation of HDAC4 expression. In addition, cell proliferation was also suppressed by knockdown of HDAC4 or treatment with HDAC inhibitor trichostatin A in HCC cell lines.Conclusion:miR-22, downregulated in HCC, has an anti-proliferative effect on HCC cells both in vitro and in vivo. Furthermore, miR-22 may have considerable potential in identification of the prognosis and application of cancer therapy for HCC patients.

Growing evidence indicates that the aberrant expression of microRNAs (miRNAs) contributes to tumor development; however, the function of miRNAs in human hepatocellular carcinoma (HCC) remains largely undefined. In this study, we report that microRNA-422a (miR-422a) is significantly down-regulated in HCC tumor samples and cell lines compared with normal controls, and its expression level is negatively correlated with pathological grading, recurrence, and metastasis. The restoration of miR-422a expression in HCC tumor cells significantly inhibited cell proliferation and migration in vitro. At the same time, the overexpression of miR-422a in HCC tumor cells significantly inhibits tumor growth and liver metastasis in xenograft tumor models. A mechanistic study identified three genes, forkhead box G1 (FOXG1), FOXQ1, and FOXE1, as miR-422a targets in the regulation of HCC development. We also investigated the function of the three targets themselves in HCC tumorigenesis using RNAi manipulation and demonstrated that the knockdown of these targets led to significant inhibition of tumor cell proliferation and migration both in vitro and in vivo. More interestingly, a potential miR-422a promoter region was identified. Both the promoter activity and miR-422a expression were negatively regulated by the three targets, indicating that a double-negative feedback loop exists between miR-422a and its targets. Moreover, we explored the therapeutic potential of miR-422a in HCC treatment and found that the therapeutic delivery of miR-422a significantly inhibited tumor development in a xenograft tumor model and a diethylnitrosamine-induced primary HCC model. Conclusion: Our findings show the critical roles of miR-422a and its targets-FOXG1, FOXQ1, and FOXE1-in the regulation of HCC development and provide new potential candidates for HCC therapy. (HEPATOLOGY 2015;61:561-573) H epatocellular carcinoma (HCC) is the fifth most common malignancy and the second leading cause of cancer-related mortality worldwide, resulting in almost 0.7 million deaths each year. Currently, the therapeutic options are limited largely to liver transplantation and surgical resection.HCC mortality has decreased with advances in surgical resection; however, the long-term prognosis of this treatment is still unsatisfactory. The 5-year survival rate is less than 30% in HCC patients after surgical resection, mainly because of the high recurrence and metastasis rate.1 A strong need for more effectiveAbbreviations: 3 0 UTR, 3 terminal untranslated regions; DEN, diethylnitrosamine; FOXE1, forkhead box E1; FOXG1, forkhead box G1; FOXQ1, forkhead box Q1; HCC, hepatocellular carcinoma; MiR-422A, microRNA-422a; NAT, noncancerous adjacent tissues; qPCR, real-time quantitative PCR.From the

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Tumor size did not independently affect long-term survival and recurrence after curative resection of solitary HCC without macroscopic vascular invasion. Therefore, there is no size limit that precludes hepatic resection for solitary HCC, provided the tumor is resectable.