Progesterone receptor gene serves as a prognostic biomarker associated with immune infiltration in gastric cancer: a bioinformatics analysis

Background: Gastric cancer (GC) is one of the most prevalent cancers globally with a poor prognosis. The progesterone receptor gene (PGR), which encodes the progesterone receptor (PR), can modulate the immune response in many cancers, but its correlation with prognosis and immune infiltration in GC remains unclear. We aimed to investigate the relationship between PGR expression and prognosis in GC patients. Methods: The expression profile was obtained and the relationship between PGR expression and cancer prognosis was analyzed by Oncomine, Tumor Immune Estimation Resource (TIMER), Kaplan-Meier plotter, the PrognoScan database and Gene Expression Profiling Interactive Analysis (GEPIA) database using the minimum P value approach and log-rank method for prognosis analysis. Next, the correlation between the expression level of PGR and immune cell infiltration by the Spearman method using TIMER and GEPIA. Results: A correlation of elevated PGR expression with poorer prognosis in GC was observed, with overall survival (OS) hazard ratio (HR) was 1.74 [95% confidence interval (CI): 1.4-2.17, P value =6.2e-7] and progression-free survival (PFS) HR was 2.09 (95% CI: 1.58-2.78, P value =1.6e-7). Also, high expression of PGR was related to worse OS and PFS in patients of each N stage in GC, with the highest OS and PFS HR values in stage N1. PGR expression in stomach adenocarcinoma (STAD) was significantly correlated with levels of B cells, CD8+T cells, CD4+T cells, macrophages, neutrophils and dendritic cells. It was also observed that PGR expression was related to a variety of immune cell markers. Conclusions: PGR expression correlated with prognosis and immune cell infiltration in GC, indicating PGR is a potential prognostic biomarker in GC patients.