RESUMO
INTRODUCTION: Due to its lack of conventional surface receptors, triple-negative breast cancer (TNBC) is inherently resistant to most targeted therapies. MAL2 overexpression prompts endocytosis, conferring resistance to novel therapeutics. This study explores the role of MAL2 and PD-L1 in TNBC patients' prognosis. METHODS: We performed immunohistochemical analysis on 111 TNBC samples collected from 76 patients and evaluated the expression of MAL2 and PD-1. We expanded the study by including The Cancer Genome Atlas (TCGA) cohort. RESULTS: MAL2 expression did not correlate with stage, grade, tumor size, lymph node invasion, metastasis, and PD-1 expression. Patients with high MAL2 had significantly lower 5-year survival rates (71.33% vs. 89.59%, p = 0.0224). In the tissue microarray cohort (TMA), node invasions, size, recurrence, and low MAL2 (HR 0.29 [CI 95% 0.087-0.95]; p < 0.05) predicted longer patients' survival. In the TCGA cohort, patients with low MAL2 had significantly longer overall survival and disease-specific survival than patients with high MAL2. Older age and high MAL2 expression were the only independent predictors of shorter patient survival in the BRCA TCGA cohort. CONCLUSION: High MAL2 predicts unfavorable prognosis in triple-negative breast cancer, and its expression is independent of PD-1 levels and clinicopathological features of TNBC.