RESUMO
A genetic polymorphism of GSTO2 causes variations in enzyme activity. It was reported that the GSTO2 wild-type (N142) allozyme showed higher levels of expression than the GSTO2 variant (D142) allozyme. Overexpression of GSTO protein has been found in chemo- and radio-resistant cancer cells. In addition, increased GSTO expression in colorectal cancer cells correlated with increased cell invasion and metastasis. Therefore, we investigated the association of GSTO2 polymorphism and prognoses for colorectal-cancer patients. Formalin-fixed, paraffin-embedded cancerous colorectal tissues from 89 patients were used to extract DNA. Gene polymorphism was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results showed that wild-type GSTO2 (N142/N142) was found mainly in patients aged \> 50 years (P=0.014). No significant difference was found between GSTO2 genotype and sex, tumor stage, tumor differentiation, and EGFR. Patients carrying wild-type GSTO2 (N142/N142) had poorer survival rates than those carrying variant GSTO2 (N142/D142+D142/D142) (P=0.015). This finding suggests that a finding of wild-type GSTO2 was related to a poor prognosis. Therefore, GSTO2 polymorphism may be used as a prognostic indicator for appropriate treatment decisions in patients with colorectal cancer. (Thai Cancer J 2010;30:18-23)
RESUMO
Since reports on GSTO2 polymorphism are still limited, therefore, this study was conducted to investigate an association of genetic polymorphism of GSTO2 and survival for colorectal cancer. Formalin-fixed, paraffin-embedded colorectal cancerous tissues from 26 patients who were continuously followed-up, were used to extract DNA and the gene polymorphism was detected by polymerase chain reaction-restriction fragment length polymorphism. Our findings revealed that the patients carried wild-type GSTO2 gene (N142/N142) had poorer survival rate, when compared with those carried variant GSTO2 gene (adjusted hazard ration, 14.02, P=0.08). No association of GSTO2 genotypes with overall survival was noted (P=0.142). However, this study is only a preliminary report of which the number of cases is small. Further study in a larger population is required to achieve high statistical power and consequently clarify this finding.