Identification Of Glycogene-type And Validation Of ST3GAL6 As A Biomarker In Urinary Bladder Cancer

Urinary bladder cancer(UBC)is one of the most common causes of morbidity and mortality worldwide characterized by a high risk of invasion and metastasis.However,the molecular classification biomarkers and underlying molecular mechanisms for UBC patient stratification on clinical outcome were poorly investigated.Abnormal glycosylation has an important role in key pathological steps of tumor development and progression.Major targets have been modified by glycans in cancer cell signaling,cell invasion,cell-matrix communication,angiogenesis,cancer distant metastasis and immune response.Aberrant glycosylation is often involved in cancer hallmarks,but this hallmark is lack from both the original and the next generation of emerging cancer hallmarks.As one of glycosylation biosynthesis pathways,sialylation is accomplished by sialyltransferases which add sialic acids to the terminal of specific substrate proteins or lipids.This process can be reversed by sialidases that function to remove sialic acids from substrates.Sialylations of cell surface glycoproteins and glycolipids that play important role involved in embryonic development,oncogenic transformation and immune response.Serum total sialic acids levels and several sialylated glycoproteins,such as prostate-specific antigen(PSA)and thyroglobulin,Sialyl Lewis A(SLe A;also named as CA19-9)and Sialyl Lewis X(SLe X)have been subsequently recognized as potential markers for cancer diagnosis.The changes in one of the sialic acid,the activity of sialidase and sialyltransferase(ST)or sialotargets will result in the alteration of sialylation.Moreover,these variations will lead to diseases and thus serve as an important biomarker for diagnosis and clinical application.A systematic transcriptomic analysis of 185 glycogenes in the public UBC datasets with survival information and clinicopathological factors were performed using unsupervised hierarchical clustering.The gene signature for glycogene-type classification was identified using Limma package in R language,and correlated to 8known molecular features by Gene Set Variation Analysis(GSVA).The clinical relevance and function of one key glycogene was characterized by immunohistochemistry in UBC patient samples,and quantitative RT-PCR,Western blotting,promoter activity,MAL II blotting,immunofluorescence staining,wound healing,and transwell assays in UBC cells.A 14-glycogene signature for glycogenetype classification was identified.ST3GAL6,a glycotransferase to transfer sialic acid to 3'-hydroxyl group of a galactose residue,showed a significant negative association with the subtype with luminal feature in UBC patients(n = 2,130 in total).Increased ST3GAL6 was positively correlated to tumor stage,grade,and survival in UBCs from public datasets or our cohort(n = 52).Transcription factor GATA3,a luminal-specific marker for UBC,was further identified as a direct upstream regulator of ST3GAL6 to negatively regulate its transactivation.ST3GAL6 depletion decreased MAL II level,cell invasion and migration in 5637 and J82 UBC cells.ST3GAL6 could reverse the effects of GATA3 on global sialylation and cell invasion in SW780 cells.Herein,we successfully identified a novel 14-gene signature for glycogene-type classification of UBC patients.ST3GAL6 gene,from this signature,was demonstrated as a potential biomarker for poor outcomes and cell invasion in UBCs.