| 摘要: | Aim: To investigate the colorectal cancer risk associated with polymorphic glutathione S transferase (GST) mu 1 (GSTM1), GST theta 1 (GSTT1) and GST pi 1 (GSTP1) and the effect of diet and smoking. Methods: With consent, genotypes of the genes were determined using polymerase chain reaction methods for 727 cases and 736 sex and age-matched healthy controls recruited at a medical centre (Chang Gung Memorial Hospital) in the Northern Taiwan. Nurses who were blind to the study hypothesis conducted interviews with study participants for information on socio-demographic variables, diet and smoking. Results: There was no significant association between GSTM1 genotypes and the disease. Men, not women, with GSTT1 null genotype were at significant risk of colorectal cancer, but limited to rectal tumour, and in men aged 60 years and less. The corresponding association with the GSTP1 with G allele compared to GSTP1 A/A genotype was at borderline significance. Compared to men with GSTT1 present and GSTP1 A/A combined, men with both GSTT1 null and GSTP1 with G allele genotypes were at significant risk (odds ratio, OR=1.91, 95% confidence interval, CI=1.21-3.02), also limited to the rectal tumour and younger men. The beneficial effects of vegetable/fruit intake on colorectal cancer were much higher for men with GSTT1 present (OR=0.32, 95% CI=0.20-0.50) or GSTP1 A/A genotypes (OR=0.40, 95% CI=0.25-0.64). These effects remained significant for women. But, the greatest protective effect from vegetable/fruit intake for women was observed in those with GSTT1 null or GSTP1 with G allele genotypes. In addition, non-smoking men benefitted significantly from combined effect of higher vegetable/fruit intake and GSTT1 present or GSTP1 A/A genotypes with OR=0.17 and 0.21, respectively. Conclusion: This study suggests that the GSTT1 gene can modulate the colorectal cancer risk and vegetable/fruit-related colorectal cancer risk, particularly in men with no history of smoking. |
