Expression of multidrug-resistant proteins in breast carcinoma and their relationship with clinical - pathological...

Breast cancer is a molecularly heterogeneous disease in which conventional prognostic factors do not fully predict clinical outcome or therapeutic response. Proteins associated with multidrug resistance (MDR) may contribute to tumor progression and treatment failure. This study evaluated the prognostic relevance of p53, glutathione S-transferase P1 (GSTP1), and P-glycoprotein (P-gp) in invasive breast carcinoma.

Immunohistochemical expression of p53, GSTP1, and P-gp was assessed in formalin-fixed, paraffin-embedded samples of invasive breast carcinomas and compared with normal breast tissue. Associations between protein expression and clinicopathological parameters were statistically analyzed.

Normal breast tissue was negative for p53 expression, whereas overexpression of dysfunctional p53 was detected in 24% of carcinomas. p53 positivity was significantly associated with higher histological grade and HER2 positivity (p < 0.05), indicating a correlation with aggressive tumor phenotype. GSTP1 expression was observed in 58% of carcinomas, while all normal tissues were GSTP1-positive. In some tumors, both cytoplasmic and nuclear GSTP1 staining was detected, possibly reflecting adaptive survival mechanisms. However, GSTP1 expression was not significantly associated with standard clinicopathological parameters. P-gp positivity was identified in 42% of carcinomas, and all normal tissues expressed P-gp. Despite its established role in drug efflux, P-gp expression did not correlate significantly with established prognostic factors.

Among the evaluated MDR-associated proteins, only p53 expression demonstrated a significant association with adverse clinicopathological features, suggesting potential prognostic relevance. The roles of GSTP1 and P-gp remain uncertain and require validation in larger prospective clinical studies.