Abstract： This study was designed to explore the transcription level,genome alteration,potential abnormal expression mechanism,prognostic value and the association with immune cells of the tetraspan MS4A6A(membrane-spanning 4A(MS4A)subfamily protein 6A)in pan-cancer.Public databases,such as UCSC Xena,cBioPortal and Timer2,were used to collect relative data,and thenbioinformatic approaches were used to analyze the correlation of MS4A6A genome and MS4A6A expression with immune infiltration,tumor mutation burden(TMB),microsatellite instability(MSI)etc.TMB and MSI were further calculated by R package maftools.Immune score,stromal score and ESTIMATE score were calculated by R package ESTIMATE.The correlation between immune score and MS4A6A expression was conducted based on Spearman correlation coefficient.Data showed that DNA methylation of MS4A6A in most cancer tissues was negatively correlated with its expression level,suggesting the possible relation of differential MS4A6A expression to the methylation level of its promoter region.Univariate Cox analysis revealed that high expression of MS4A6A was the risk factor for LGG,TGCT,UVM and THYM;MS4A6A expression was positively correlated with the immune score in 32 types of cancer;MS4A6A expression was positively correlated with the infiltration levels of various immune cells,such as tumor associated fibroblasts(CAF),regulatory T cells(Treg),B cells,neutrophils,macrophages,monocytes,and CD8+T cells.In conclusion,MS4A6A may participate in the development of cancer,suggesting it is a potential new biomarker for cancer treatment and prevention.