Single-cell and bulk RNA sequencing demonstrate the critical function of the regulatory T cell-associated gene SIRPG in the prognosis and tumor microenvironment of esophageal squamous cell carcinoma

Immunosuppression by regulatory T cells (Tregs) significantly contributes to poor prognosis of esophageal squamous cell carcinoma (ESCC), although the specific regulatory genes and mechanisms involved are not well understood. We analyzed single-cell RNA sequencing and bulk transcriptomic data from TCGA and GEO for ESCC, screening key Treg-associated genes through WGCNA, differential expression analysis, and immune infiltration analysis. Gene functions were validated through in vitro experiments (siRNA knockdown, CCK-8 assay, Transwell assay, 3D tumor spheroid model). SIRPG was identified as a key gene specifically overexpressed in Tregs of ESCC. It was strongly associated with a bad outcome for individuals with ESCC and was highly expressed in several cohorts. SIRPG overexpression modified the immune microenvironment by enhancing Treg infiltration, increasing immune checkpoint molecules (PD-1, CTLA-4, PD-L1), and enriching pathways such as T cell receptor, IL-17, and PI3K-Akt. Functional experiments demonstrated that reducing SIRPG expression markedly inhibited the proliferation, migration, and invasion of ESCC cells. SIRPG was a key Treg-associated oncogene in ESCC that promotes tumor progression by regulating the immune microenvironment and multiple signaling pathways, which exhibited great clinical potential for ESCC patients.