The hMLH1 promoter polymorphisms and cancer susceptibility in Asian populations: a meta-analysis

Single nucleotide polymorphisms in MLH1 predict poor prognosis of hepatocellular carcinoma in a Chinese population

Hepatocellular carcinoma (HCC) is a malignant cancer causing deleterious health effect worldwide, especially in China. So far clinical cure rate and long-term survival rate of HCC remains low. Most HCC patients after cancer resection have recurrence or metastasis within 5 years. This study aims to explore the genetic association of mutL homolog 1 (MLH1) polymorphisms with HCC risk and prognosis. Four candidate MLH1 polymorphisms, rs1800734, rs10849, rs3774343 and rs1540354 were studied from a hospital-based case-control study including 1,036 cases (HCC patients) and 1,036 controls (non-HCC patients) in Guangxi, China. All these SNPs interacted with environmental risk factors, such as HBV infection, alcohol intake and smoking in the pathogenesis of HCC. However, only rs1800734 had significant difference between cases and controls. Compared to the AA genotype, patients with AG, GG and AG/GG genotype of rs1800734 had an increased risk of HCC [ORs (95% CI) = 1.217 (1.074∼1.536), 1.745 (1.301∼2.591) and 1.291 (1.126∼1.687)] and a decreased survival time [co-dominant, HR (95% CI) = 1.553 (1.257∼1.920); dominant, HR (95% CI) = 2.207 (1.572∼3.100)]. Furthermore, we found that tumor number, tumor staging, metastasis and rs1800734 were associated with the overall survival of HCC patients by multivariate COX regression analysis. No significant difference was found between the other three MLH1 polymorphisms with HCC risk and prognosis. Our study suggests MLH1 SNP, rs1800734 as a new predictor for poor prognosis of HCC patients.

Prognostic value of MLH1 promoter methylation in male patients with esophageal squamous cell carcinoma

The DNA mismatch repair (MMR) gene MutL homolog 1 (MLH1) is critical for the maintenance of genomic integrity. Methylation of the MLH1 gene promoter was identified as a prognostic marker for numerous types of cancer including glioblastoma, colorectal, ovarian and gastric cancer. The present study aimed to determine whether MLH1 promoter methylation was associated with survival in male patients with esophageal squamous cell carcinoma (ESCC). Formalin-fixed, paraffin-embedded ESCC tissues were collected from 87 male patients. MLH1 promoter methylation was assessed using the methylation-specific polymerase chain reaction approach. Kaplan-Meier survival curves and log-rank tests were used to evaluate the association between MLH1 promoter methylation and overall survival (OS) in patients with ESCC. Cox regression analysis was used to obtain crude and multivariate hazard ratios (HR), and 95% confidence intervals (CI). The present study revealed that MLH1 promoter methylation was observed in 53/87 (60.9%) of male patients with ESCC. Kaplan-Meier survival analysis demonstrated that MLH1 promoter hypermethylation was significantly associated with poorer prognosis in patients with ESCC (P=0.048). Multivariate survival analysis revealed that MLH1 promoter hypermethylation was an independent predictor of poor OS in male patients with ESCC (HR=1.716; 95% CI=1.008-2.921). Therefore, MLH1 promoter hypermethylation may be a predictor of prognosis in male patients with ESCC.

Mismatch repair gene polymorphisms and association with lung cancer development

hMLH1 and hMSH2 are two of the main members of the mismatch repair (MMR) genes family. Polymorphism of MMR genes is associated with a risk of developing sporadic and hereditary tumors. In the present case-control study, we investigated the promoter polymorphisms of selected mismatch repair genes: hMLH1 (rs1800734) and hMSH2 (rs2303425), and the risk they present regarding the development of lung cancer in the Slovak population. The study included 422 lung cancer cases, 511 controls for hMLH1 gene and 486 controls for hMSH2 gene. Polymorphism was investigated by a PCR-RFLP method. The risk of cancer development was evaluated in both dominant and recessive genetic models. The evaluation of rs1800734 polymorphism in patients in the dominant model showed a significantly decreased risk of lung cancer in the presence of at least one variant allele A (genotype GA and AA) (OR=1.40; 95% CI=1.08-1.82; p=0.01). These findings were equally strong expressed in women (OR=2.00; 95% CI=1.23-3.25; p=0.006). The results for rs2303425 polymorphism revealed an increased risk of lung cancer for variant genotype CC (OR=2.28; 95% CI=1.12-4.63; p=0.024) in the recessive model. A combination of rs1800734 and rs2303425 polymorphisms was shown to be risky for genotype GGCC; OR=3.08; 95% CI=1.09-8.72; p=0.03. The risk appeared even greater in female gender; (OR=11.56; 95% CI=1.33-100.36, 1.26-94.66; p=0.005. We conclude that the genotype of mismatch repair genes underscores the risk of lung cancer development in the Slovak population.