Association Study Of Polymorphisms In Cytochrome P450 4B1 Gene And Bladder Cancer Risk

Background and ObjectiveBladder cancer is the first common cancer in urology. Bladder cancer is considered a multifactorial disease where environmental factors interact with the individual genetic background resulting in risk modulation as other tumors. Many literatures have reported that CYP1A1 gene was associated with the susceptibility of tumors correlated to smoking. CYP1A2 slow-metabolizing genotype, CYP2C19 EMs, and NAT2 slow-acetylation genotype can increase the risk of bladder cancer significantly. However, there were few and conflict conclusions on study between polymorphism of CYP4B1 gene and bladder cancer. In a case-control study, we detect frequency of genotype and allelic gene of CYP4B1. The potential interactions of these metabolic enzymes with the risk factors such as smoking tobacco, occupational exposure and well-done meat consumption were also explored. The aim of our study is to investigate the relationship between polymorphism of CYP4B1 and the risk of bladder cancer, and elucidate the interaction of the gene polymorphism and environmental factors.Materials and MethodsSubjects The study population consist of a series of bladder cancer patients and non-cancer controls admitted to the department of urology, the first affiliated hospital of Zhengzhou University, from February, 2006 to January, 2007. The study design is approved by the Committee on Human Research of Zhengzhou University. The study subjects give informed consent prior to participation in the study. Patients who are diagnosed as incident bladder cancer cases with histopathological confirmation, and from whom a peripheral blood sample is drawn and selected as cases (n=127). Controls (n=125) who are individuals with no present or previous history of bladder cancer or other tumors, are simultaneously recruited in the same hospital. The two groups are collected from Han ethnic population in Henan province. The rate distribution of age, gender in two groups is equilibrated, and they are comparable with each other.Epidemiological investigation Information on demographic characteristics,education, marital status, family history of bladder cancer in the first and second relatives, occupational exposure history, life style including tobacco smoking, and well-done meat consumption, are collected by trained interviewers using a structured questionnaire.Genotyping Genotyping of CYP4B1 variants is performed by the polymerase chainreaction-based Single-Strand Conformation Polymorphism(PCR-SSCP) method. PCR produts are detected by agarose gel electrophoresis and polyacrylamide gel electrophoresis. Alleles and genotypes are defined by fragments in polyacrylamide gel.Statistical analysis Statistical analysis is conducted using the package SPSS 12.0for Windows. Char-square is used to compare the distribution of genotypes and single alleles in cases and in controls. The association between environmental risk factors and bladder cancer is studied by unconditional logistic regressive analysis. An odds rate (OR) and 95% confidence interveral (95%CI) are also calculated, size of test is 0.05.Results Results of Gnotyping The distribution of the allele frequencies among case andcontrol subjects are in Hardy-Weinberg equilibrium. The distribution frequencies of CYP4B1C517T homozygous wild type (C/C) in cases and control are 39.4% and 56.0%; the frequency of heterozygote (C/T) is 51.2% and 36.8%; the frequency of heterogenesis homozygote (T/T) is 9.4% and 7.2%. The most frequent genotype of CYP4B1 Exon 8 is the homozygous wild type (65.4% in cases VS. 75.6% in controls). The distribution frequencies of CYP4B1 Exon 8 homozygous wild type, Wt/AT881-882del+G993A+C1018T and AT881-882del+G993A+C1018T are 36.2%, 58.3% and 3.1% in cases, respectively and 56.8%, 35.2% and 2.4% in controls, respectively. The Wt/G993A is not detected in cases. The frequencies of CYP4B1C1123T homozygous wild type (C/C) are 40.2% and 64.2% in cases and in controls, respectively. The frequencies of heterozygote (C/T) and heterogenesis homozygote (T/T) are 56.7% and 3.1% in cases, respectively, and 35.2% and 2.4% in controls, respectively.Associaton between genotypes and susceptibility of bladder cancer ForCYP4B1C517T, AT881-882del+G993A+C1018T and C1123T genotypes, significant difference are found between cases and controls (P=0.008, P=0.000, P=0.000). The difference of distribution frequency of G993A genotype is not significant between cases and controls.Genotypes and phymatoloy character of BC. For CYP4B1 C517TAT881-882del+G993A+C1018T G993A and C1123T genotypes, there is no significant difference of genotype frequence distribution among different pathology grade and clinical stage BC. patients.Environmental risk factors and bladder cancer The unconditional logisticregressive analysis suggest that tobacco smoking, occasional exposure and well-done meat consumption are risk factors to susceptibility of bladder cancer (OR=2.541, OR=2.246, OR=2.556, respectively). Moreover, the gender (female) is considered as a protective factor to bladder cancer (OR=0.275, 95%CI: 0.168-0.597). . Interaction of genotypes and risk fators to susceptibility of BladderCancer Tobacco smoking, occasional exposure and well-done meat consumptioncombined with CYP4B1517T, AT881-882del+G993A+C1018T and 1123T genetypes increase the risk of bladder cancer.Conclusions1. Heterogenesis of CYP4B1C517T, AT881-882del+G993A+C1018T andC1123T are associated with the susceptibility to bladder cancer. The individuals with the CYP4B1C517T, AT881-882del+G993A+C1018T and C1123T increase the risk of bladder cancer.2. For CYP4B1C517T. AT881-882del+G993A+C1018T, G993A and C1123Tgenotypes, there is no significant difference of genotype frequence distribution among different pathology grade and clinical stage BC. patients.3. Tobacco smoking, occasional exposure and well-done meat consumption arerisks to susceptibility of bladder cancer. However, the gender (female) is a protective factor to bladder cancer.4. The individuals possessing CYP4B1C517T, AT881-882del+G993A+C1018Tand C1123T mutational genotypes have an increased risk of bladder cancer with exposure to such risk factors as tobacco smoking, occasional exposure and well-done meat consumption.