We analyzed 20 germline polymorphisms in 10 genes (TS, MTHFR, ERCC1, XPD, XRCC1, ABCC2, AGXT, GSTP1, GSTT1 and GSTM1) from prospectively enrolled 292 Korean patients treated with adjuvant oxaliplatin plus leucovorin plus 5-fluorouracil (FOLFOX) for colon cancer.
The combined GSTM1 null and GSTP1 114Val allele also revealed an increased risk for either colon cancer (OR=4.69; 95% CI, 0.84-23.87) or rectal cancer (OR=5.68; 95% CI, 1.79-22.16).
Having GSTM1 present, a CYP1A1 variant allele, and the rapid-acetylator NAT2 imputed phenotype was associated with increased risk of colon cancer (odds ratio = 1.7, 95% confidence interval: 1.2, 2.3).
If pooling studies were based on the genotyping method, the overall odds ratio of colon cancer risk associated with the GSTM1 deficiency showed no difference.
However, among individuals with both GSTM1 and T1 null genotypes, we observed a 57% reduction in risk among high versus low consumers of ITC (OR 0.43, 95% CI 0.20-0.96), in particular for colon cancer (OR 0.31, 0.12-0.84).
Among younger individuals who were GSTM-1 present (relative to those with GSTM-1 null), we observed an inverse association with colon cancer regardless of level of cruciferous vegetable intake (OR 0.74 95% CI 0.30-1.79 for no intake; OR 0.44 95% CI 0.21-0.92 for <4 servings/week; and OR 0.
Epidemiological studies have linked consumption of broccoli to a reduced risk of colon cancer in individuals with the glutathione S-transferase M1 (GSTM1) null genotype.
Neither NAT2 nor GSTM-1 polymorphisms were significantly associated with colon cancer, except among older women, in whom the intermediate/rapid imputed phenotype was associated with increased risk of colon cancer [odds ratio (OR) = 1.4, 95% confidence interval (CI) = 1.0-1.81.
Current cigarette smokers with GSTM1 null genotype were not at an increased risk of colon cancer (OR = 1.2; 95% CI, 0.3-4.2) compared with current smokers without the null genotype; for the GSTT1 null genotype this OR was 1.1 = 95% CI (0.3-4.7).
Some studies have reported an association of the GSTM1-null genotype with the risk of smoking-related cancers, such as lung, bladder, and colon cancer.
Using PCR to identify the GSTM1 genotype, we found the frequency of GSTM1- in colon cancer (n = 19) and control group (n = 23) was 36.8% and 26.1%, respectively (p > 0.05, chi 2-test).