Molecular epidemiology of bladder cancer

• Project/Area Number: 09671641
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Urology
• Research Institution: Osaka City University
• Principal Investigator: YAMAMOTO Keisuke Medical School, Osaka City University, Associate Professor, 医学部, 助教授 (70137230)
• Co-Investigator(Kenkyū-buntansha): IMAOKA Susumu Medical School, Osaka City University,, 医学部, 助教授 (60145795) ; FUNAE Yoshihiko Medical School, Osaka City University,, 医学部, 教授 (00047268) ; IKEMOTO Shinichi Medical School, Osaka City University,, 医学部, 助手 (90168154)
• Project Period (FY): 1997 – 1998
• Project Status: Completed (Fiscal Year 1998)
• Budget Amount: ¥2,800,000 (Direct Cost: ¥2,800,000); Fiscal Year 1998: ¥1,100,000 (Direct Cost: ¥1,100,000); Fiscal Year 1997: ¥1,700,000 (Direct Cost: ¥1,700,000)
• Keywords: cytochrome P450 / CYP4B1 / bladder tumor / competitive RT-PCR / peripheral lymphocyte / 膀胱癌 / 分子生物学

Research Abstract

Bladder cancer is the common disease in Urology. Etiological risk factors of bladder cancer are occupational exposure to certain carcinogen and sex-difference is present in bladder cancer. Males have high risk for bladder cancer in human and experimental animals. Aromatic amines such as 2-naphthylamine and benzidine are typical carcinogens for bladder which are included in cigarette smoke and in environment as industrial chemicals. Carcinogenic aromatic amines are thought to require activation to electrophilic species before exerting carcinogenic effects. Metabolic activation of several carcinogenic aromatic amines are done by cytochrome P450s. In this study, we identified a P450 isoform responsible for activation of aromatic amines and developed the risk assessment of bladder carcinoma.
First, we investigated mutagenic activation of aromatic amines such as 3,3'- dichlorobenzidine and 2-naphthylamine by 10 purified rat P450s using the umu gene expression system (umu test), which detects DNA damage. CYP4B1 had extensively high activity towards these amines of P450s studied. Immunochemical study indicated this P450 was present in the rat bladder. Furthermore, we found that male rat had higher expression of CYP4B1 mRNA than female and its expression was regulated by testosterone. Like in rat, immunochemical study indicated presence of CYP4B1 in human bladder but we failed to get sex-difference in expression of human CYP4B1 because numbers of sample from female was very small. However, we found that bladder tumor patients had higher expression level of CYP4B1 in their bladders than non-bladder tumor patients. These results suggested that CYP4B1 is an important enzyme in initiation of baldder carcinoma and may account for the mechanism of higher incidence of bladder cancer in male or by smoking. Furthermore, we developed CYP4B1 expression level using peripheral lymphocytes by competitive RT-PCR and obtained the results that bladder tumor patient had high expression levels of CYP4B 1. This approach could be an important tool in the assessment of human bladder cancer risk.