Abstract: Objective The study focuses on the prognostic value of SMYD3 in pan cancer, and analyze the influence of SMYD3 on tumor tissue immune infiltration. Methods The gene expression and protein density data were collected from TCGA, GTEx and HPA databases. Kaplan-Meier(KM) algorithm was used to evaluate the impact of SMYD3 on the prognosis of patients with different kinds of tumor. The ESTIMATE algorithm and Timer database were applied to investigate the relationship between SMYD3 and immune microenvironment. And the results were verified in B16 cell line by knockout SMYD3. Results Higher expression of SMYD3 was observed in tumor tissue than normal tissue in both mRNA and protein level. And SMYD3 was thought to be associated with worse outcomes of patients(P<0.05) and less immune cells inflation in tumor tissue(P<0.05). Knockout Smyd3 in B16 cell line increased the expression of antigen present genes(P<0.05). Conclusions Smyd3 is an important gene related to the prognosis of patients and the antigen presentation function of tumor cells. Smyd3 can inhibit the infiltration of immune cell by down-regulation of antigen-present genes, which induces the immune escape.

Key words: SMYD3, pan-cancer, immune infiltration, immune escape, MHC class Ⅰ molecule