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

Abstract

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.

Figure 1.

Sensitivities of head and neck squamous cell carcinoma and resistant cell lines to cisplatin. UM-SCC 23, UM-SCC 81B and UM-SCC 23 C/R cells were treated with cisplatin for 24 h, and the cytotoxicity was analyzed using a colony-formation assay. Each data point is the mean of three independent experiments. Vertical bars represent standard deviations.

Figure 2.

mRNA expression levels of hMLH1 and hMSH2. UM-SCC 23, UM-SCC 81B and UM-SCC 23 C/R cells were analyzed using real-time RT-PCR. Each data point is the mean of three independent experiments. Vertical bars represent standard deviations.

Figure 3.

Expression levels of hMLH1 and hMSH2 mismatch repair proteins. UM-SCC 23, UM-SCC 81B and UM-SCC 23 C/R cells were examined by Western blot analysis.

Figure 4.

Changes in the microsatellite sequence. Microsatellite sequence changes were detected with Gene Scan. Results in D9S171 for UM-SCC 81B are shown. The upper column shows results noted in 59 of 61 samples, the lower column shows microsatellite sequence changes in 2 of 61 samples. The red lines indicate base size marker and the black lines indicate the samples. The arrow shows 100 bases.