SELP can affect the immune microenvironment of gastric cancer and is associated with poor prognosis.

The tumor microenvironment (TME) plays a crucial role in the occurrence and progression of gastric cancer. Yet, we still don't understand how immune and stromal components of TMEs are modulated. In this study, we applied the ESTIMATE algorithm to calculate the number of immune and stromal components in 410 STAD cases in the Cancer Genome Atlas (TCGA) database. COX regression analysis and protein-protein interaction (PPI) network construction were used to analyze differentially expressed genes (DEGs). Then, P-selectin (SELP) was identified as a predictor by cross-analysis of univariate COX and PPI. After verifying the clinical significance of SELP for study, we performed an immune infiltration analysis and identified 54 immunomodulators associated with SELP through public data. Immunomodulation associated with gastric cancer prognosis was then confirmed by LASSO regression, and the previous results were further validated with single-cell data. Finally, we verified that SELP can promote EMT on gastric cancer cells. In conclusion, we validated that SELP may affect the biological phenotype of gastric cancer with the immune microenvironment alteration of gastric cancer.