The Research Of Molecular Mechanism Of Mitofusin-2 In Hepatocellular Carcinoma

At present, liver cancer is one of common malignant tumor and the second cause of death of malignant tumors in our country. Liver cancer was mostly detected at middle-late stage for early HCC with no specific symptoms and signs. Besides the hepatectomy, there are still lacks of other effective treatments for liver cancer. The developing trends and hot issues of treatments for HCC focus on intervening the activation and proliferation of tumor cells. Cancer formation is associated with uncontrolled cell hyperplasia. To develop and maintain tissue homeostasis in multicellular organisms, apoptosis plays a key role during such pathological hyperplasia.Hyperplasia suppressor gene (HSG), a novel gene associated with hypertension, was also called mitofusin 2 (MFN2) for its relation to mitochondrion fusion. MFN2 had been confirmed to suppress cells proliferation mediated by inhibiting the activation of Ras-Erk passageway, up-regulating P27 and P21Cipl, down-regulating PCNA and arresting the cells at G1/G0 phase, which implied that MFN2 was closely related to tumors development.Part ⅠMicroRNA-761 is upregulated in hepatocellular carcinoma and regulates tumorigenesis by targeting Mitofusin-2Aims:Mitofusin-2 (MFN2), anchored on the outer mitochondrial membrane, participates in mitochondrial fusion and contributes to the maintenance of the mitochondrial network. The fate of a cell is determined by the balance between the processes of fission and fusion that constantly occur in the mitochondria of cells. The function of Mitofusin-2 has been studied extensively. Here, we aim to evaluate the mechanisms underlying the post-transcriptional regulation of MFN2.Methods:We employed the luciferase assay to test the possible microRNA of MFN2. We measured the expression of miR-761 in 50 pairs of HCC tissue samples and their corresponding control liver tissues using RT-qPCR. The microRNA expression of tumor tissues and adjacent normal tissues was analyzed by QRT-PCR. The impact of microRNA on cells apoptosis, cell proliferation, cell migration and invasion, mitochondrial membrane potential (Δψm) and intracellular reactive oxygen species (ROS) were analysed. We established the in vivo orthotopic HCC model to determine the effect of the microRNA on HCC tumor growth in vivo.Results:We demonstrated that Mitofusin-2 is a direct target of miR-761, which was found to be upregulated in HCC tissues. The high level of miR-761 was significantly associated with low level of MFN2. Further, a miR-761 inhibitor impairs mitochondrial function by upregulating Mitofusin-2 and effectively repressed tumor growth and metastasis both in vivo and vitro.Conclusions:This study reveals that miR-761 is upregulated in HCC tissues and can affect mitochondrial function and inhibit cell proliferation, migration, and invasion in vivo and in vitro by targeting MFN2. This may represent a novel approach for the treatment of HCC in future studies.Part ⅡLow expression of the MFN2-related gene NAV3 is associated with poor survival in hepatocellular carcinomaAims:Little is known mechanistically about the exact role of MFN2 in HCC. Here, we investigated the changes in gene expression associated with MFN2, and identified the low expression of the MFN2-related gene NAV3 in patients with HCC. Additionally, the prognostic and functional relevance of NAV3 in HCC was explored.Methods:The global mRNA expression profile was obtained using mRNA microarray. Expression of NAV3 was evaluated by Immunohistochemistry in 90 HCC tissue samples and in adjacent normal tissues. The impact of NAV3 overexpression on cell proliferation, migration, invasion, and apoptosis was evaluated in vitro and in vivo.Results:Microarray analysis revealed that NAV3 expression is related to that of MFN2. Immunohistochemical analysis showed that low expression of NAV3 was strongly correlated with poor prognosis, tumor size, tumor differentiation, and AJCC stage. Combination analysis of NAV3 and MFN2 provided increased prognostic value. Overexpression of NAV3 in HCC cell lines significantly reduced cellular proliferation, migration, and invasion, and enhanced cellular apoptosis. Up-regulation of NAV3 by lentivirus also significantly suppressed the growth of tumor in node mice in vivo.Conclusions:NAV3 expression, which is related to that of MFN2, plays a significant role in HCC. Low expression of NAV3 indicated poor prognosis, suggesting that NAV3 may be a potentially useful predictive biomarker in HCC, as well as a potential novel target for therapy.