A Nested Case-control Study Of N-acetyltransferase2, NAD (P) Hi Quinone Oxidoreductase 1 And Methylenetetrahydrofolate Reductase Polymorphisms And The Risk Of Retal Adenoma Recurrence

Background and aims:The archetypal pathogenic pathway, the adenoma-carcinoma sequence, was first described and most common pathway for tumorgenesis of colorectal cancer. During 1977-1980, we have conducted a population-based mass screening for rectal cancer with proctoscope in Haining City. All polyps to be detected in mass screening have been removed under endoscopy. In addition, a six times periodical endoscopy following up program has been performed among those 4076 cases with history of polyps (including adenoma and non-adenoma polyps) during 1980 to 1998. According to cancer registry hi Haining city, both incidence and mortality of rectal cancer have been reduced among target population during the past 20 years. This results addressed the hypothesis that colorectal polyps resection would block the progress of tumorgenesis hi rectal cancer. However, we also observed that each individual with history of polyps had variety recurrence potential. It is indicated that those high-risk population had variety susceptibility of rectal cancer due to different genetic and environmental background. Therefore, It would be great helpful for strategy making for cancer prevention of colon and rectum to observe the polymorphism of metabolizing enzyme gene interacting with potential high risk factors and explore its relationship with colorectal cancer genetic susceptibility.Material and MethodsWe have established a 4076 case of cohort population who had rectal adenomas and polyps in a population-based mass screening during 1977-1980. A periodical endoscopy following up program has been performed among those participants during the past 20 years. This is a nested case-control study. Of 52 cases were identified as recurrence group who were diagnosed as adenoma at mass screening program and were 2 or more times recurrence in 5 or 6 times endoscopy following program. Of 52 controls are randomly selected from the cohort population who were diagnosed as adenoma at mass screening program and were no recurrence hi 5 or 6 times endoscopy following up. Genomic DNA was extracted from the peripheral blood lymphocyte of participants using phenol/chloraform protocol. The PCR-RFLP (Restriction Fragments Length Polymorphism) was employed to detect the polymorphism of NAT2 (N-acetyltransferase 2), NQO1 (NA(P)DH: Quinone Oxidoreductase 1) and MTHFR( Methylenetetrahydrofolate Reductase). The up-stream primer: 5' GGA ACA AAT TGG ACT TGG 3' and down-stream primer: 5' TCT AGC ATG AAT CAC TCT GC 3' were used to amplify the genomic NAT2 gene of participants; And the restriction enzyme of Kpnl Taq I, BamHI and MAPI/AluI were applied to identify the NAT2 polymorphism of Ml, M2, M3 and M4 respectively. For NQO1 gene 609 C->T polymorphism detection, the genomic NQO1 gene was amplified using primers of 5'-TCC TCA GAG TGG CAT TCT GC-3'and 5'-TCT CCT CAT CCT GTA CCT CT-3, and digested with restriction enzyme of Hinf I. MTHFR gene was amplified with primer of 5'-TGA AGO AGA AGO TGT CTG CGG GA -3' and 5'-AGG ACG GTG CGG TGA GAG TG-3', and digested with restriction of Hinf I to detect it's polymorphism as well. The questionnaire of participants was collected through face-to-face interview during 6th endoscopyfollowing up. The database was created with FOXPRO software and analyzed using SPSS 10.0 (Statistical Package for the Social Science).ResultsThe frequency of wild-type NAT2 (Wt/Wt) in control group (17/52, 32.7%) is obviously higher than hi recurred group (8/52,15.4%). Heterogeneity type of NAT2 frequency in recurred group was 40/52(76.9%), and in control group was 30/52(57.7%). Both of them reach the statistical significance, PO.05. Comparing with wild-type NAT2 (Wt/Wt), the Odd Ratio (OR) were 2.96(95%CI: 1.091-8.009) and 2.125(95%CI 0.666-6.781) in Wt/M* and M*/M* genotype respectively. However, our study failed to show the difference of rapid acetylator and slow acetylator between recurrence group and controls. Nevertheless, smoking could interact with NAT2 polymorphism to increase the risk of adenoma recurrence significantly. The...