Mining the prognostic significance and immune infiltration of STAT family members in human breast cancer by bioinformatics analysis

Background: Growing evidence proved that signal transducer and activators of transcription (STAT) proteins are cytoplasmic transcription factors known to play key roles in many cellular biological processes and may be prognostic predictors of some cancers. However, the role of each STAT family members in breast cancer (BRCA) is diverse and controversial. This study aimed to systematic mine the prognostic significance and immune infiltration of STAT family member in human BRCA. Methods: Based on The Cancer Genome Atlas (TCGA) database, we used the Oncomine, Gene Expression Profiling Interactive Analysis (GEPIA) and The Human Protein Atlas to analyze the expression of STAT family members in normal human breast and tumor tissues. The Kaplan-Meier Plotter, GEPIA and PrognoScan were utilized to assess the prognostic value of different STATs in BRCA. Then we used the cBioPortal, STRING, GeneMANIA and Metascape to make further mutation analysis, protein-protein interaction (PPI) analysis and subsequent functional enrichment analysis. Finally, the "ESTIMATE" and "ggcorrplot" package of R 17 software were used for immune infiltration analysis. Results: STAT2 [P<0.01, hazard ratio (HR) =1.23, 95% confidence interval (CI): 1.07-1.42] and STAT3 (P=0.018, HR =0.69, 95% CI: 0.51-0.94) could be an independent risk factor for predicting overall survival (OS). STAT4 could be used as an independent predictor of distant metastasis-free survival in BRCA based on both GSE19615 (P=0.021, HR =0.21, 95% CI: 0.06-0.79) and GSE2034 (P=0.015, HR =0.57, 95% CI: 0.37-0.90) datasets. Meanwhile, STAT5A, STAT5B and STAT6 also have been shown to independently predict the prognosis of BRCA. Additionally, the functional mechanisms of STAT4 co-expressed genes were mainly focused on immune-related pathways and its expression was associated with immune checkpoint associated genes and immunomodulators in BRCA. Conclusions: Our study mined the prognostic significance of STAT family members in BRCA and their correlation with immune infiltration. The results suggest that individual STATs, except STAT1, may act as a prognostic biomarker for BRCA and provide a reference for further potential immunotherapies.