A case-control study on the effects of the genetic polymorphisms of N-acetyltransferase 2 and glutathione S-transferase mu and theta on the risk of bladder cancer

N-Acetyltransferase 2와 glutathione S-transferase mu 및 theta 다형성이 방광암 발생에 미치는 영향에 대한 환자-대조군 연구

Activities of enzymes involved in the metabolism of various carcinogenic xenobiotics is one of the most important host factors for cancer occurrence. N-acetyltransferase (NAT) and glutathione S-transferases (GST) are enzymes which .educe the toxicity of activated carcinogenic metabolites. Slow N-acetylation and lack of GST mu (GSTMI) were reported as risk factors of bladder cancer. GST theta (GSTT1), which is another type of GST, was reported to be deleted at higher proportion among Koreans. Since cause of bladder cancer is not fully explained by single risk factor, many kinds of enzymes would be involved in the metabolism of carcinogens excreted in urine. This study was performed to investigate whether the polymorphisms of NAT2, GSTM1 and GSTT1 are risk factors of bladder cancer and to evaluate the effects of their interaction on bladder cancer development. Sixty-seven bladder cancer and 67 age- and sex-matched non-cancer patients hospitalized in Chungbuk National University Hospital from March to December 1996, are the subjects of this case-control study. Questionnaire interview was done and the genotypes of NAT2, GSTM1 and GSTT1 were identified using PCR methods with DNA extracted from venous blood. The effects of the polymorphism of NAT2 and GSTM1 and their interaction on bladder cancer were statistically tested after controlling the other risk factors. The frequencies of slow, intermediate, and rapid acetylators were 3.0%, 38.8%, and 58.2% to. the cases, and 7.6%, 40.9%, and 51.5% for the controls, respectively. The risk of bladder cancer was not associated with the increase of NAT2 activity($\chi^2_{trend}=1.18$, P-value>0.05). GSTM1 was deleted in 68.7% of the cases and 49.3% of the controls ($\chi^2=5.21$, P-value<0.05), and the odds ratio (95% CI) was 2.23 (1.12 - 4.56). GSTT1 deletion, the .ate of which were 26.9% for the bladder cancer patients and 43.3% for the controls, was a significant protective factor against bladder cancer. Smoking history turned out to be insignificant as a risk factor of bladder cancer (OR=1.85, 95% CI: 0.85 - 4.03), and occupation could not be tested because of the extremely small number of occupational history related to the increase of bladder cancer. In multiple logistic analysis controlling the effects of other risk factors, GSTM1 deletion was the only significant risk factor for bladder cancer (OR: 2.56, 95% CI: 1.22-5.36, P-value<0.05), but slow acetylation and GSTT1 deletion were not. These results suggest that GSTM1 deletion may be a significant risk factor of bladder cancer. Since there have been much debates on causal relationship between slow acetylation and GSTT1 deletion, and bladder cancer, further studies are needed.

1996년 3월부터 1996년 12월까지 충북대학교병원 비뇨기과에 입원하여 치료를 받은 방광암 환자 67명과 암 아닌 다른 질환을 가진 대조군 67명을 대상으로 흡연, 음주, 직업력 등을 포함한 생활 습관과 NAT2와 GSTM1, 그리고 GSTT1 유전자 다형성 양상을 조사하여 다음과 같은 결론을 얻었다. 1. NAT2 다형성 분포는, 환자군이 slow, intermediate, rapid acetylator가 각각 3.0%, 38.8%, 58.2%, 그리고 대조군이 7.6%, 40.9%, 51.5%였으며, NAT2의 활성과 방광암 위험도 사이의 관련성은 유의하지 않았다($\chi^2_{trend}=1.18$, P-value>0.05). 2. GSTM1 결손은 환자군의 68.7%, 대조군의 49.3%에서 확인되었으며, OR(95% 신뢰구간)이 2.23(1.12-4.56)으로, 방광암 발생의 위험인자로 나타났다. 3. GSTT1은 환자군의 26.9%,그리고 대조군의 43.3%에서 결손이 있는 것으로 나타나서, GSTT1 결손은 방광암에 대하여 보호효과가 있는 것으로 관찰되었다(OR: 0.48, 95% 신뢰구간: 0.23-0.99). 4. 흡연 여부는 방광암의 발생에 유의한 영향을 미치지 않는 것으로 나타났는데(OR=1.85, 95% CI: 0.85-4.03), 이는 환자군과 대조군의 흡연률이 모두 높기 때문으로 판단된다. 5. 그 외, 음주력, 직업력, 수혈 여부, 그리고 피임시술의 과거력 등의 요인들은 방광암 발생과 유의한 관련성이 없는 것으로 나타났다.