Methylenetetrahydrofolate reductase C677T polymorphism and predisposition towards esophageal squamous cell carcinoma in a German Caucasian and a northern Chinese population.

PURPOSE: Folate deficiency is considered to increase the risk of developing esophageal cancer. Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme involved in folate metabolism. A single C --> T substitution at nucleotide 677 of the MTHFR cDNA influences enzyme activity. The purpose of this study is to compare the association of the MTHFR C677T polymorphism with susceptibility to esophageal squamous cell carcinoma (ESCC). METHODS: Using real-time PCR and melting curve analysis, the MTHFR C677T genotypes were determined in 430 patients with ESCC (241 German Caucasians and 189 northern Chinese) and 397 unrelated healthy controls (256 German Caucasians and 141 northern Chinese). RESULTS: A significant difference in MTHFR C677T genotype distribution was observed between German Caucasian controls (C/C, 41.8%, C/T, 44.9%, T/T, 13.3%) and northern Chinese controls (C/C, 17.7%, C/T, 38.3%, T/T, 44.0%) (chi(2)=52.19, P<0.001). The distribution of the MTHFR C677T genotypes among German ESCC patients (C/C, 39.0%, C/T, 48.1%, T/T, 12.9%) was not significantly different from that among healthy controls (chi(2)=0.531, P=0.767). In contrast, the frequency of the C/C genotype among Chinese ESCC patients (8.5%) was significantly lower than among Chinese healthy controls (17.7%) (chi(2)=6.37, P=0.012). The C/C genotype was correlated with a significantly reduced risk for the development of ESCC as compared to the combination of C/T and T/T genotypes (adjusted OR=0.38, 95% CI=0.16-0.88). CONCLUSIONS: Our results suggest that, in contrast to German Caucasians, the MTHFR 677CC homozygous wild-type plays a protective role in the development of ESCC in the northern Chinese population.

Hypermethylation of tumor suppressor genes (p16INK4A, p14ARF and APC) in adenocarcinomas of the upper gastrointestinal tract.

Aberrant promoter methylation is an important mechanism for gene silencing. In the present study, 50 Barrett's esophagus-associated esophageal adenocarcinomas (ADC), 50 cardiac ADC and 50 gastric ADC were investigated by means of methylation-specific real-time PCR for hypermethylation in the tumor suppressor genes APC, p16(INk4A) and p14(ARF). Additionally, expression of p16(INK4A) protein in the carcinomas was assessed using immunohistochemistry. Marked differences in hypermethylation were found between esophageal, cardiac and gastric ADC in the APC gene (78% vs. 32% vs. 84%) and in the p16(INK4A) gene (54% vs. 36% vs. 10%). Hypermethylation of p14(ARF) was absent from esophageal ADC and present infrequently in cardiac (2%) and gastric ADC (10%). Complete loss of p16(INK4A) protein expression was detectable in 45% of all tumors and was significantly associated with hypermethylation of the p16(INK4A) gene (p<0.0001, chi(2)-test). Our results suggest that hypermethylation of p16(INK4A) and APC are frequent findings in esophageal, cardiac and gastric ADC. Additionally, the data point to a tumor specific methylation pattern in upper gastrointestinal ADC.

Association between NAD(P)H: quinone oxidoreductase 1 (NQ01) inactivating C609T polymorphism and adenocarcinoma of the upper gastrointestinal tract.

NQO1 is an antioxidant enzyme, important in the detoxification of environmental carcinogens. A single nucleotide polymorphism (C-->T) at position 609 of the NQO1 cDNA has been associated with susceptibility to tumours induced by chemical carcinogens. In our case-control study, we determined the prevalence of the C609T NQO1 polymorphism by PCR-RFLP analysis in Caucasian patients with oesophageal adenocarcinoma (OAC; n=61), cardiac adenocarcinoma (CAC; n=120) or gastric adenocarcinoma (GAC; n=203) vs. a control group that consisted of 252 healthy blood donors. Additionally, NQO1 mRNA expression and NQO1 protein expression were determined by RT-PCR and immunohistochemistry in a subset of cases. The NQO1 C609T genotype distribution was significantly different among controls (C/C, 73.4%; C/T, 25.0%; T/T, 1.6%) as compared to OAC patients (C/C, 49.2%; C/T, 47.5%; T/T, 3.3%; p=0.0004), CAC patients (C/C, 55.8%; C/T, 40.0%; T/T, 4.2%; p=0.0005) and with GAC patients (C/C, 65.5%; C/T; 30.6%, T/T; 3.9%; p=0.0377). The 609T allele overall frequency was 0.141 in controls, 0.270 in OAC patients, 0.241 in CAC patients and 0.192 in GAC patients. Individuals carrying 1 or 2 609T alleles had a 2.85-fold higher risk (95% CI: 1.61-5.07; p=0.0003) for the development of OAC and a 2.18-fold higher risk (95% CI: 1.38-3.44; p=0.0007) for the development of CAC than wild-type gene homozygotes. Immunohistochemical analysis showed NQO1 protein expression in 133 carcinomas, whereas 17 carcinomas were negative. Negativity for NQO1 protein expression correlated strongly with the NQO1 genotype being present in 3.9% of cases with C/C, 13.9% of cases with C/T and 62.5% of cases with T/T genotype (p<0.001). In contrast, NQO1 mRNA expression was detectable irrespective of underlying genotype. In conclusion, determination of the NQO1 genotype may gain importance as a stratification marker in future prevention trials for adenocarcinoma of upper gastrointestinal tract.