Predictive value of CHFR and MLH1 methylation in human gastric cancer

Abstract

Background: Gastric carcinoma (GC) has one of the highest mortality rates of cancer diseases and has a high incidence rate in China. Palliative chemotherapy is the main treatment for advanced gastric cancer. It is necessary to compare the effectiveness and toxicities of different regimens. This study explores the possibility of methylation of DNA damage repair genes serving as a prognostic and chemo-sensitive marker in human gastric cancer.

Methods: The methylation status of five DNA damage repair genes (CHFR, FANCF, MGMT, MLH1, and RASSF1A) was detected by nested methylation-specific PCR in 102 paraffin-embedded gastric cancer samples. Chi-square or Fisher's exact tests were used to evaluate the association of methylation status and clinic-pathological factors. The Kaplan-Meier method and Cox proportional hazards models were employed to analyze the association of methylation status and chemo-sensitivity.

Results: The results indicate that CHFR, MLH1, RASSF1A, MGMT, and FANCF were methylated in 34.3% (35/102), 21.6% (22/102), 12.7% (13/102), 9.8% (10/102), and 0% (0/102) of samples, respectively. No association was found between methylation of CHFR, MLH1, RASSF1A, MGMT, or FANCF with gender, age, tumor size, tumor differentiation, lymph node metastasis, and TNM stage. In docetaxel-treated gastric cancer patients, resistance to docetaxel was found in CHFR unmethylated patients by Cox proportional hazards model (HR 0.243, 95% CI, 0.069-0.859, p = 0.028), and overall survival is longer in the CHFR methylated group compared with the CHFR unmethylated group (log-rank, p = 0.036). In oxaliplatin-treated gastric cancer patients, resistance to oxaliplatin was found in MLH1 methylated patients (HR 2.988, 95% CI, 1.064-8.394, p = 0.038), and overall survival was longer in the MLH1 unmethylated group compared with the MLH1 methylated group (log-rank, p = 0.046).

Conclusions: CHFR is frequently methylated in human gastric cancer, and CHFR methylation may serve as a docetaxel-sensitive marker. MLH1 methylation was related to oxaliplatin resistance in gastric cancer patients.

Fig. 1

Methylation of five DNA damage repair genes in gastric cancer tissues. a Methylation-specific PCR (MSP) results of CHFR. b MSP results of MLH1. c MSP results of RASSF1A. d MSP results of MGMT. e MSP results of FANCF. H₂O negative control to confirm the specificity of MSP, IVD positive control to confirm the specificity of MSP, M presence of methylated alleles, U presence of unmethylated alleles, 1–7 gastric cancer samples

Fig. 2

Association of gene methylation and overall survival in gastric cancer patients. Kaplan–Meier survival curves were constructed according to the presence of gene methylation in gastric cancer. a In the docetaxel-treated group, overall survival is longer in the CHFR methylated group than in the CHFR unmethylated group. b In the oxaliplatin-treated group, overall survival is longer in the MLH1 unmethylated group than in the MLH1 methylated group

Fig. 3

Association of gene methylation and overall survival in gastric cancer patients. Kaplan–Meier survival curves were constructed according to the presence of gene methylation in gastric cancer. a In the oxaliplatin-treated group, there is no significant difference in overall survival between the CHFR methylated group and the unmethylated group. b In the docetaxel-treated group, there is no statistical difference in overall survival between the MLH1 methylation group and the unmethylated group