Identification And Validation Of Glycosyltransferase Gene Related Prognostic Signature And Key Gene ST6GAL1 In Colorectal Cancer

Background: Abnormal glycosyltransferase(GT)gene expression has been universally regarded as a hallmark of malignant cancer.The anomaly of GT gene in cancer cells might act as a new bio-marker that plays an important role in the development as well as progression of colorectal cancer(CRC).However,its effect on the prognosis and treatment of CRC patients and its specific mechanism are not clear.Therefore,the purpose of this study is to identify the characteristics of GT gene,clarify the relationship between glycosylation and the prognosis of CRC patients,and explore the potential mechanism.Methods: The glycosylation-related genes were obtained from the GSEA websites.The limma R package was used to screen the differential glycosylationrelated genes(DEGs)in CRC from The Gene Expression Omnibus(GEO)dataset.The Consensus Cluster was performed based on the gene expression.The least absolute shrinkage and selection operator(LASSO)was to establish the 32-gene prognostic signature.The survival and receiver operating characteristic(ROC)curves were illustrated to evaluate the predictive effect of the signature.Besides,downstream functional enrichment and immune feature were analyzed.Moreover,all these conclusions were verified by clinical samples and cellular experiments.The expression differences,prognostic differences,and immune cell infiltration levels were verified by immunohistochemistry(IHC).The function of the glycogene ST6GAL1 was verified by cellular models,specifically by means of SNA-Lectin pulldown,Co-Immunoprecipitation(CO-IP),Western bloting,CCK-8,transwell,clone formation and other analyses.Results: Four prognosis-related GT genes model(COG7,GBF1,RPN2,ST6GAL1)were developed to predict the prognosis of CRC patients by Lasso analysis.Immune correlation analysis showed a significant difference in the proportion of immune cells in CRC patients between the high-and low-risk groups.In CRC clinical samples,high expression of ST6GAL1 was associated with poor prognosis and correlated with more neutrophil infiltration levels.In the CRC cell model,ST6GAL1 promotes the malignant progression of CRC tumor cells.In addition,ST6 GAL induced the N-terminal glycosylation modification of PD-L1 and maintained the stability of PD-L1 protein as well.Conclusions: Our study identified a novel gene set consisting of 4 GT genes,which can be used for prognostic typing of CRC patients.The ST6GAL1 gene from this model expressed at significantly higher levels in tumor tissue than in normal tissue and was shown to be a potential biomarker for poor prognosis.The up regulation of its expression may be related to the increased infiltration level of neutrophil activation marker CD66 b.