NAT2 slow acetylation and bladder cancer in workers exposed to benzidine

Area of Science:

• Occupational Health
• Genetics
• Cancer Epidemiology

Background:

• Benzidine exposure is a known risk factor for bladder cancer.
• Genetic polymorphisms, particularly in NAT2, influence individual susceptibility to chemical carcinogens.
• Previous studies suggest a link between NAT2 genotype and bladder cancer risk, but findings vary depending on the specific arylamine exposure.

Purpose of the Study:

• To investigate the association between NAT2, NAT1, and GSTM1 polymorphisms and bladder cancer risk in Chinese male workers occupationally exposed to benzidine.
• To compare these findings with existing meta-analyses on NAT2 acetylation and bladder cancer in Asian populations.

Main Methods:

• Combined analysis of a new cohort (30 cases, 67 controls) with previous data (total 68 cases, 107 controls).
• NAT2 enzymatic activity assessed via urinary caffeine metabolite ratios.
• Genotyping for NAT2, NAT1, and GSTM1 performed using PCR-based methods.
• Statistical adjustments for cumulative benzidine exposure and smoking history.

Main Results:

• A protective association was found for the slow NAT2 genotype (OR = 0.3) against bladder cancer in benzidine-exposed workers.
• Individuals with NAT1wt/*10 and NAT1*10/*10 genotypes showed increased relative risks (OR = 2.8 and OR = 2.2, respectively).
• No association was observed between GSTM1 null genotype and bladder cancer.
• Meta-analysis of Asian populations without occupational arylamine exposure indicated an increased risk for slow acetylators (OR = 1.4).

Conclusions:

• The slow NAT2 genotype appears protective against bladder cancer specifically in the context of benzidine exposure.
• This contrasts with the role of slow acetylation as a risk factor for bladder cancer in populations exposed to other arylamines like 2-naphthylamine and 4-aminobiphenyl.
• Findings suggest distinct metabolic pathways and carcinogenic mechanisms for mono- and diarylamines.