Roles And Molecular Mechanisms Of Sialyltransferase ST8SIA1 In The Development Of Bladder Cancer

Background: The bladder cancer is the 10 th most common cancer worldwide,with an estimated 549,000 new cases and 200,000 deaths per year.It is more common in men than women,with morbidity and mortality rates four times higher in men than in women.Bladder cancer is characterized by poor prognosis and easy recurrence.Protein glycosylation is a common post-translational modification that plays a key role in many biological processes of tumors.Sialylation is one of the important ways of glycosylation modification,and sialyltransferase is the key enzyme to catalyze this process,and ST8SIA1 is one of the members of sialyltransferase family.Studies have shown that the abnormal expression of ST8SIA1 has an effect on the metastasis of breast cancer,but its role in bladder cancer is still unknown.Objective: To study the expression of ST8SIA1 in bladder cancer and its clinical significance.To investigate the effect of up-regulated expression of ST8SIA1 on the proliferation,migration and invasion of bladder cancer cells.To analyze the molecular mechanism of bladder cancer cells mediated by ST8SIA1 and to explore the correlation between JAK/STAT pathway and bladder cancer cells.Methods:(1)Glycosyltransferase genes with different expression in bladder cancer and normal bladder urothelial tissues were screened according to TCGA database.The GEPIA statistical method was used to select the sialyltransferase gene from the differential genes.Differences in the expression of two genes were compared in the high-low risk group.Immunohistochemistry and Western blot were used to verify the differences in the expression of sialyltransferase ST8SIA1 in bladder cancer tissues and normal bladder urothelium.(2)The expression of m RNA in different bladder cancer cell lines was detected by Real-time PCR,the expression of ST8SIA1 in different bladder cancer cell lines and normal bladder urothelial cells was detected by Western blot,T24 and 5637 monoclonal cell lines stably up-regulated by ST8SIA1 were obtained by molecular cloning,and the expression of ST8SIA1 in T24 and 5637 cells was identified by Western-blot and Real-time PCR.(3)The effect of sialyltransferase ST8SIA1 on the proliferation,migration and invasion of bladder cancer cells was detected by CCK8,plate cloning,flow cytometry,scratch and transwell.(4)The KEGG analysis of ST8SIA1 related genes showed that they were enriched in five pathways,and the key proteins were screened.Western blot was used to study the molecular mechanism of the effect of ST8SIA1 on bladder cancer cells.Results:(1)45 glycosyltransferases with differential expression were screened from 408 bladder cancer cases.It was found that the higher the pathological grade and the degree of invasion of bladder cancer,the lower the expression of ST8SIA1 by immunohistochemistry.Compared with normal bladder epithelial tissue,the m RNA and protein level of ST8SIA1 in bladder cancer tissue was down-regulated in varying degrees by Western blot.(2)The m RNA and protein levels in bladder cancer tissue were analyzed by Real-time PCR and Western blot,and the bladder cancer cell lines T24 and 5637 with stable overexpression of ST8SIA1 were successfully constructed.(3)It was found that the proliferation,migration and invasion of bladder cancer cells were significantly inhibited after up-regulation of ST8SIA1 by CCK8,plate cloning,flow cytometry,scratch and transwell analysis.(4)It was found that up-regulation of ST8SIA1 could inhibit the expression of JAK2,STAT3,MMP9,PCNA and Bcl2,and promote the expression of BAX by Western blot test.After adding pathway inhibitors,the expression levels of JAK2,STAT3,MMP9,PCNA and Bcl2 were lower.Conclusion:(1)The expression level of ST8SIA1 in bladder cancer tissue is significantly lower compared with normal bladder urothelial tissue,and its down-regulation is closely related to the pathological grade and degree of invasion of bladder cancer;(2)Overexpression of ST8SIA1 can inhibit the proliferation,migration and invasion of T24 and 5637 cells;(3)Up-regulation of ST8SIA1 expression in bladder cancer cells can inhibit JAK/STAT signal pathway.