Associations between genetic polymorphisms of glutathione S-transferase M1 and T1, smoking and susceptibility to colorectal cancer: a case-control study / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To evaluate the associations between genetic polymorphisms of glutathione S-transferase M1 and T1 (GSTM1 and GSTT1), smoking and susceptibility to colorectal cancer.</p><p><b>METHODS</b>A case-control study of 126 patients and 343 healthy controls was conducted to investigate the role of GSTM1 and GSTT1 polymorphisms in colorectal cancer. Genotypes of GSTM1 and GSTT1 polymorphisms were analyzed by multiplex allele-specific polymerase chain reaction (PCR).</p><p><b>RESULTS</b>The frequencies of GSTM1 null and GSTT1 null genotypes were 55.5% and 20.4%, respectively. After adjustment for age and sex, among those with GSTT1 null genotype, the GSTM1 null genotype had a significant increased risk of rectal cancers compared to GSTM1 non-null genotype (OR=9.74, 95% CI, 1.13 - 83.85). A 2.22-fold risk of colon cancers was associated with GSTM1 null genotype compared to GSTM1 non-null genotype among current smokers (P >0.05). Individuals with GSTT1 null genotype and currently smoking had a significant risk of colon cancers (OR = 4.55, 95% CI, 1.14 - 18.17), and rectal cancers (OR = 4.60, 95% CI, 1.11 - 19.11).</p><p><b>CONCLUSION</b>This study suggests that certain null GSTM1 and GSTT1 genotypes may be associated with an elevated risk of colorectal cancer which may be modified by interaction of the two genetic polymorphisms and cigarette smoking.</p>

A case-control study on the polymorphisms of methylenetetrahydrofolate reductases, drinking interaction and susceptibility in colorectal cancer / 中华流行病学杂志

<p><b>OBJECTIVE</b>To investigate the relationship between methylenetetrahydrofolate reductases (MTHFR) polymorphisms and colorectal cancer susceptibility.</p><p><b>METHODS</b>A case-control study of 126 patients and 343 healthy controls was conducted to investigate the roles of MTHFR C677T and A1298C polymorphisms in colorectal cancer development. Genotypes of C677T and A1298C polymorphisms were analyzed by polymerase chain resction-restriction fragment length polymorphism (PCR-RFLP) methods.</p><p><b>RESULTS</b>The frequencies of MTHFR 677T and 1298C allele were 39.7% and 17.1%, respectively. After adjustment for age and sex, the MTHFR 1298C alleles seemed to have reduced association on the risk of colorectal cancer comparing to wild types. Among those with 677T and 1298A alleles, a decreased risk of colorectal cancer was observed: a 4-fold decrease in colorectal cancer risk (OR = 0.552, 95% CI: 0.265 - 1.150) in those with 677T and 1298C alleles. Men who were ex-drinkers and with MTHFR 1298C allele had a 2-fold increase in risk of colorectal cancer (OR = 3.307, 95% CI: 0.521 - 17.698) while no increased risk was seen among those current-drinkers.</p><p><b>CONCLUSIONS</b>This study suggested that certain MTHFR C677T and A1298C might be associated with the risk of colorectal cancer development. The interaction between MTHFR 1298AC polymorphisms and ex-drinking might also serve as a risk factor of colorectal cancer.</p>

Genetic polymorphism in cytochrome P450 2E1, salted food and colorectal cancer susceptibility: a case-control study / 中华预防医学杂志

<p><b>OBJECTIVE</b>To investigate PstI allelic variants of cytochrome P450 2E1 (CYP2E1), the interaction effect on salted food and their role in risk for colorectal cancer.</p><p><b>METHODS</b>The genotypes of CYP2E1 PstI restriction fragment length polymorphism were analyzed in 126 colorectal cancer cases and 343 normal controls. The unconditional logistic regression was applied to estimate the OR and its 95% CI.</p><p><b>RESULTS</b>The CYP2E1 C1/C1, C1/C2 and C2/C2 genotypes were found respectively in 61.8%, 35.8% and 2.4% of normal control, similar to rectal cancer cases. The percentage of PstI variant genotype (54.9%: 52.9% C1/C2 and 2.0% C2/C2) in colon cancer cases was significantly higher than that in controls (adjusted OR1.979, 95% CI 1.090 approximately 3.595). Stratified analysis suggested an interaction between CYP2E1 C2 allele and salted food. The odds ratio (OR) for the CYP2E1 variant genotype, salted food eaten weekly or biweekly and eaten every day or every other day were 1.935, 2.122 and 2.315, respectively, while those of salted food combined with variant genotype eaten weekly or biweekly and eaten every day or every other day were 2.272 and 3.127. The role in risk for rectal cancer was different from that for colon cancer. Whatever the CYP2E1 genotype is, the risk for rectal cancer came to marked when salted food was consumed weekly or biweekly (OR = 2.646 and 2.297, respectively). However, none but the combined effect of variant genotype and salted food eaten every day or every other day had the notably risk for colon cancer and the odds ratio suddenly increased to 4.262 (95% CI 1.395 approximately 13.017), 1.69-fold higher than that of wild genotype (P = 0.072).</p><p><b>CONCLUSION</b>The CYP2E1 C2 allele is a susceptibility factor for colorectal cancer, especially for colon cancer, and there is an apparent gene-environment interaction between the susceptible genotype and salted food.</p>