Pan-Cancer Single-Cell Expression Characteristics of GSTP1 and Its Prognostic and Immune Significance

Background: Glutathione S-transferase P1 (GSTP1) plays a critical role in cellular detoxification and stress response, and its dysregulation is implicated in various malignancies. However, a comprehensive understanding of its expression landscape at the single-cell level and its immunological significance across a broad spectrum of cancers is lacking. This study aimed to systematically characterize GSTP1 expression and investigate its associations with patient prognosis and the tumor immune microenvironment to determine its clinical value. Methods: First, public single-cell RNA sequencing (scRNA-seq) data from the Gene Expression Omnibus (GEO) were analyzed to define the cell-type–specific expression of GSTP1 within the tumor microenvironment and identify its primary cellular sources. Subsequently, pan-cancer transcriptomic profiles and clinical data were obtained from The Cancer Genome Atlas (TCGA) and the Genotype-Tissue Expression (GTEx) project to compare GSTP1 expression between tumor and normal tissues across multiple cancer types. Kaplan–Meier survival analysis and univariate Cox regression were conducted to assess the associations between GSTP1 expression and overall survival (OS), disease-specific survival (DSS), disease-free interval (DFI), and progression-free interval (PFI). Finally, immune scores were calculated using the ESTIMATE algorithm to evaluate the correlation between GSTP1 expression and tumor immune microenvironment characteristics. Results: Single-cell analysis revealed that GSTP1 is predominantly expressed in tumor epithelial cells. Pan-cancer analysis indicated that GSTP1 expression is significantly upregulated in multiple tumor tissues compared to corresponding normal tissues (P < 0.05), a finding further supported by proteomic data from CPTAC. Survival analysis demonstrated that high GSTP1 expression is significantly associated with unfavorable prognosis in various cancer types. Furthermore, GSTP1 expression exhibited heterogeneous correlations with immune and stromal scores across different tumor types. Conclusion: GSTP1 is aberrantly upregulated across pan-cancer, and its expression level is closely associated with patient prognosis and the tumor immune microenvironment, suggesting its potential value as a diagnostic and therapeutic targe.