| Objective: Hepatocellular Carcinoma (HCC) is one of the most common malignacyin the world, especially in China. It often follows an aggressive course with frequentrelapse and metastasis. In this article we investigate how osteopontin (OPN), a moleculeclosely associated with malignancy, plays a key role in the metastasis of HCC andinterpret its pro-metastatic mechanism.Methods: Short hairpin RNA constructs targeting OPN or lentivirus encoding OPNcDNA was employed to interfere or overexpress OPN gene. The relationship betweenOPN and MET was investigated both morphologically and at transcriptional andtranslational level. Localization of OPN was detected by immunohistochemical methodand confocal microscopy. We used antibody blocking assays to evaluate the effect ofsecreted OPN. A series of siRNA and microRNA mimics and inhibitor was applied toexamine the downstream pathway. The interaction of OPN and HIF2a was demonstratedby co-immunoprecipitation assays, and chromatin immunoprecipitation (CHIP) assaywas further applied to explore the interaction of HIF2a and AKT1promoter, and toinvestigate the effect of OPN on the interaction. In vivo studies were used to determinethe occurrence of MET in metastatic procedure and the influences of OPN on MET andmetastasis.Results: We are the first to establish that nuclear OPN can induce MET in hepatomacell lines, and for the first time we investigate the mechanism of this phenomenon thatnuclear OPN can directly interact with Hif2a and impact the downstream cascade,AKT1/miR-429pathway. In vivo assays show that the progress of metastasis isaccompanied by MET and the overexpression of intracellular OPN, and that OPNdeficiency cannot induce the occurrence of MET, resulting in reduced tumor metastasis.Moreover we are the first to reveal the nuclear presence of OPN in tumor cell lines,opening up a new direction for the study of HCC metastasis.Conclusions: Nuclear OPN facilitates HCC metastatic colonization by inducingMET. |
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