Human MLH1 status can potentially predict cisplatin sensitivity but not microsatellite instability in head and neck squamous cell carcinoma cells.

Resistance to platinum-based chemotherapy frequently poses a serious problem in the treatment of head and neck squamous cell carcinoma. In this study, we isolated cisplatin-resistant cells from a head and neck squamous cell carcinoma cell line. The mismatch repair (MMR) system is known as one of the cisplatin-resistant mechanisms. When the expression levels of hMLH1 and hMSH2, a mismatch repair gene and its gene product, were analyzed, the hMLH1 mRNA and protein expression levels were significantly decreased in the cisplatin-resistant cell lines compared with a cisplatin-sensitive cell line. In addition, the microsatellite instability (MSI) phenotype was examined for the absence of MMR. Our data support the hypothesis that hMLH1 mRNA and protein expression levels are predictors of cisplatin sensitivity, but MSI was not involved in cisplatin resistance. The status of hMLH1 predicts the sensitivity of head and neck squamous cell carcinoma to platinum-based chemotherapy.