MLH1 expression predicts the response to preoperative therapy and is associated with PD‑L1 expression in esophageal cancer.

Programmed death‑ligand 1 (PD‑1/PD‑L1) inhibition therapy demonstrates potential as a future treatment for esophageal cancer. Mismatch repair status and tumor PD‑L1 expression are the candidate predictive biomarkers for response to this therapy. In colorectal cancer, mismatch repair‑deficient tumors are associated with improved survival, although they are not sensitive to 5‑fluorouracil‑based chemotherapy. The purpose of the present study was to investigate the association between MutL homolog 1 (MLH1) expression and prognosis, response to therapy and PD‑L1 expression in esophageal cancer. Immunohistochemistry was used to evaluate MLH1 and PD‑L1 expression in 251 resected specimens. Of the specimens, 30.3% exhibited low MLH1 expression and 15.5% exhibited high PD‑L1 expression. The 5‑year overall survival rates for the high MLH1 expression group and the low MLH1 expression group were 51.3 and 55.6%, respectively (P=0.5260). The responder ratio was 45.7% in the high MLH1 expression group and 15.4% in the low MLH1 expression group (P<0.0001). The frequency of high PD‑L1 expression was 11.4% in the high MLH1 expression group (P=0.0064) and 25.0% in the low MLH1 expression group. MLH1 expression may be a predictive factor for the response to preoperative therapy in esophageal cancer, and esophageal cancer with low MLH1 expression may have a mechanism that assists in promoting tumor PD‑L1 expression. [ABSTRACT FROM AUTHOR]