Colorectal Cancer Carcinogenesis: a Multivariate Genetic Model in a Cohort of Romanian Population.

Background: The molecular mechanism of carcinogenesis of sporadic colorectal cancer (CRC) involves genes with roles in folate metabolism, genes involved in metabolization of carcinogenic compounds from diet and tobacco smoke, and genes related to the DNA repair process. The aim of the study was to examine whether the MTHFRC677T, MTHFR- A1298C, TS-2rpt/3rpt, TS-1494del6bp, NAT2*5C-C481T, NAT2*5A-T341C, NAT2*6B-G590A, NAT2*7B-G857A, NAT2*18-A845C, GSTM1-null, XRCC1-Arg399Gln, XRCC3-Thr241Met, XPD-Lys751Gln genetic variations are associated with CRC prognosis, in the presence of environmental and demographic factors.

Methods: We genotyped 150 patients diagnosed with sporadic CRC using PCR-RFLP and sequencing methods. The performance of the final model was quantified using Nagelkerke's coefficient, the Hosmer-Lemeshow test, C statistics, and Somers' (D) index, capable of describing the model's goodness-of-fit and discrimination.

Results: Multiple logistic regression analysis established a significant independent association of NAT2*18-A845C, MTHFR-C677T, XRCC3-Thr241Met, NAT2*7B-G857A, XPD-Lys751Gln, XRCC1-Arg399Gln and NAT2*6BG590A with an increased prevalence of sporadic CRC, regardless of the presence/absence of colonic tumors. After an adjustment for other polymorphisms and environmental risk factors, the risk to develop sporadic CRC was 2.25 (p = 0.011) and 2.31 (p = 0.01) in association with the NAT2*18-A845C and MTHFR-C677T genetic variants, respectively. The risk increased to 3.22 (p = 0.0005) and 3.69 (p = 0.0009) in association with the XRCC3Thr241Met and NAT2*7B-G857A polymorphisms. Also, patients carrying the XPD-Lys751Gln, XRCC1Arg399Gln, and NAT2*6B-G590A polymorphisms had a 4.16 (p < 0.0001), 5.16 (p < 0.0001), and 5.46-fold (p < 0.0001) increased risk for sporadic CRC, under the dominant genetic comparison model. In addition, we found an interaction between gender and alcohol, the effect of alcohol consumption on the risk of developing sporadic CRC being different in female and male patients.

Conclusions: Our study confirmed the predictive role of some polymorphisms associated with DNA methylation and procarcinogen transformation into carcinogenic compounds in sporadic CRC risk and, also, the influence of environmental risk factors such as diet, smoking, and alcohol consumption on this association.