Glutathione S-transferase mu Gene Variants and Colorectal Cancer Development - Use of Sequence-specific Probes for an Iranian Population

Background: Enzymes of the glutathione S-transferase (GST) family are encoded by a set of polymorphic genes as an important part of cellular chemical defense. The aim of this study was to investigate the possible effect of GSTM1 deletion on susceptibility to developing clinical outcome of colorectal cancer in a group of CRCpatients from Isfahan province, Iran, in comparison to age and gender matched control group.
Methods: DNA was extracted from blood of 140 CRC patients and 90 healthy individuals and a set of sequence specific hybridization probes was used for GSTM1 genotyping by real-time PCR in Light-Cycler instrument. Chi-squared test was used to assess the statistical significance of observed differences between the patient and control subjects of different genders and ages. To estimate the risk for overall and stratified analyses, odds ratios (OR) with 95% confidence intervals (CI) computed with logistic regression.
Results: No difference in GSTM1 null genotype frequency was found in CRC patients and controls stratified by gender (p value=0.14). The data were suggested a trend of increasing risk for GSTM1 null genotype in patients over 60 years old compared with controls (p value=0.05). GSTM1 null genotype carried an increase of the odds of developing CRC in patients over 60 years old (OR=2.7; 95% CI: 1.03-7.05). No significant association was found (P> 0.05) between the GSTM1 null genotype with tumor site (right, left, rectum) or tumor differentiation (well, moderately).
Conclusion: Our findings suggest that the GSTM1 null genotype may contribute to colorectal cancer development in people over 60 years old.