CDC42SE1 as a novel prognostic biomarker with immunomodulatory associations in breast invasive carcinoma

This study aims to investigate the expression pattern, prognostic significance, and immune-related role of CDC42SE1 in breast invasive carcinoma (BRCA). RNA sequencing and clinical data from TCGA-BRCA and GEO datasets (GSE42568, GSE10810) were analyzed. CDC42SE1 expression was compared between tumor and normal tissues. Survival analyses, univariate and multivariate Cox regression, immune infiltration estimation (ssGSEA), and functional enrichment analyses were performed. A nomogram was constructed to predict patient survival. CDC42SE1 was significantly upregulated in BRCA tissues compared to normal controls (p < 0.001; AUC = 0.757), with validation in two independent GEO cohorts and at the protein level (CPTAC). High CDC42SE1 expression correlated with reduced overall survival (p = 0.014; HR = 1.43) and was identified as an independent prognostic factor in multivariate analysis (HR = 1.43, p = 0.033). Immune infiltration analysis revealed moderate positive associations with Tcm (R = 0.335), Th2, and Th17 cells, and negative associations with pDCs and cytotoxic cells. Functional enrichment linked CDC42SE1 to histone modification, ubiquitin-mediated proteolysis, and mRNA surveillance pathways. A nomogram incorporating CDC42SE1 showed moderate accuracy in predicting 1-, 3-, and 5-year survival (AUC: 0.580–0.585). CDC42SE1 is overexpressed in BRCA and associated with poor prognosis and altered immune infiltration, suggesting its potential as a prognostic biomarker with immunomodulatory relevance. Further mechanistic studies are warranted.