Expressional analysis of MLH1 and MSH2 in breast cancer

Mismatch repair proteins are ubiquitous keys in diverse cellular functions and protects the genome by correcting mismatch as post replication error correction machinery. Mismatch repair deficiency was associated with tumor development and progression therefore, current study was aimed to investigate MLH1 and MSH2 expression in breast cancer and correlate patients' clinicopathological factors with status of mismatch repair genes.

Breast cancer tissues with adjacent normal tissue along with clinical details were collected during surgery from 80 cases. Immunohistochemistry was performed with primary and secondary antibodies for expressional analysis. Results were analyzed using SPSS version 24.

Immunohistochemical analysis revealed that both MLH1 and MSH2 were crucial in maintaining DNA repair system and loss of these 2 mismatch repair proteins may lead to adverse outcomes in breast cancer. Statistically significant association was found between loss of MLH1 (P = 0.0004; odds ratio 13.8; 95% confidence interval 4.6-41.1), MSH2 (P = 0.0002; odds ratio 14.0; 95% confidence interval 4.7-42.2) and breast cancer. Statistical analysis demonstrated that MLH1 and MSH2 deficiency may lead breast cancer progression to advanced stage, correlated with tumor focality (MLH1 P = 0.001; MSH2 P = 0.002) and chemotherapy (MLH1 P = 0.01; MSH2 P = 0.04). Presence of CK7, GATA 3, and E cadherin tends to increase in mismatch repair deficient breast cancer. Whereas, no association of mismatch repair deficiency was observed with age, tumor grade, positive lymph nodes, menopause, and ER and/or PR status.

Loss of mismatch repair proteins in breast cancer highlights its potential role in DNA repair mechanisms and helps tumor cells to become resistant against chemotherapeutic drugs. Therefore, mismatch repair deficiency may contribute to breast cancer progression.