The Impact Of Caveolin-1 Knockout On Core Fucosylation In Mice With Chemical-induced Hepatocarcinoma

Background: Caveolin-1,Cav-1,is a major structural and functional component of caveolae,and involved in the regulation of important biological processes,which include cholesterol transport,endocytosis,signal transduction and tumor metastasis.It has been controversial that Cav-1 plays a tumor suppressor or tumor promoter.Primary hepatic carcinoma is one of the most common malignant tumors in China and leads the third highest death rate in the global cancer.It has been reported that Cav-1 can promote the invasion and metastasis of Hepatocarcinoma cells.The core fucosylation is one of the important protein post-translational modifications,which was mainly catalyzed by fucosyltransferase 8(?1,6-fucosyltransferase,FUT8/Fut8)to form ?1-6 linked bond between fucose and Nacetylglucosamine(Glc NAc).Abnormally high expression of core fucosylation occurs in the development process of liver cancer and other malignant tumors,but the related molecular mechanism is still under investigation.Wnt/?-catenin signaling pathway plays an important role in the physiological process of cell differentiation,apoptosis and tumor invasion.Wnt/?-catenin signaling activation may promote transcription of target gene through ?-catenin/TCF/LEF complex binding to transcription factor TCF/LEF binding site.Bioinformatics analysis indicated the existence of TCF/LEF binding sites in the promoter region of Fut8 gene,suggesting that the Wnt signaling pathway may mediate ?1-6 fucose glycosylation by targeting Fut8 gene expression.Previous studies in our laboratory and others showed that overexpression of Cav-1 involved in the activation of Wnt/?-catenin signaling pathway by ways of leading to accumulation of ?-catenin in the cytoplasm in hepatocarcinoma cells,activating the transcriptional activity of Fut8,and promoting the core fucosylation levels.However,it is still unclear if Cav-1 expression promotes Fut8 expression and core fucosylation via Wnt/?-catenin signaling pathway in vivo.Objective: Our aim to investigate the impact of Caveolin-1 knockout on Core Fucosylation in mice with chemical-induced Hepatic Carcinoma.Method: Hepatocarcinoma was induced by injecting Diethylnitrosamine and by gavage of carbon tetrachloride/ethyl alcohol into the wild type and Caveolin-1 knockout C57BL/6J mice for up to 24 weeks.At indicated time points,Hepatocarcinoma and its adjacent tissues were harvested and confirmed by pathological diagnosis,followed by q PCR,western-blot,lectin-blot and MALDI-TOF/TOF MS analyses of the protein and m RNA of Fut8 and core fucosylation level in tissue and in serum.Results:1)At 0 week,Fut8 and the core fucosylation level in liver tissue and serum is significantly reduced in Cav-1 KO mice,compared with that in WT mice.2)Both in WT and KO mice,the expression level of Fut8,?-catenin and the core fucosylation in liver tissue and/or in serum were significantly higher at 24 weeks than that at 0 week.3)During Hepatocarcinogenesis(0-24 weeks),expression of Cav-1,?-catenin and N-cadherin gradually increased significantly,but E-cadherin which is a classical marker of epithelial–mesenchymal transition gradually declined significantly in WT mice.However,expression of these proteins was significantly lower in KO mice than that in WT mice.These results suggested that Cav-1 promoted the accumulation of ?-catenin through EMT process,which up-regulated Fut8 gene expression and core fucosylation level during Hepatocarcinogenesis.Conclusion: This study presented evidences in vivo to support that deletion of Cav-1 down-regulates Fut8 gene expression and core fucosylation level during chemical-induced Hepatocarcinogenesis in mice,which mechanism is associated with EMT and Wnt/?-catenin signaling pathway.