GSTM1 and GSTT1 Genetic Polymorphisms and Breast Cancer Risk in Selected Filipino Cases

Abstract

Background: The association of genetic polymorphisms with cancer development has been shown to be race- and<br />tumor site-specific. Thus, this study aimed to determine whether polymorphisms in the GSTM1 and GSTT1 genes<br />are associated with breast cancer among selected Filipinos. Methods: A total of 136 histologically confirmed breast<br />cancer cases were age- and sex-matched with 136 clinically healthy controls. Genomic DNA extracted from blood<br />samples of participants were screened for GSTM1 and GSTT1 genetic polymorphisms by multiplex PCR. Results:<br />The frequency of null genotypes among the cases (GSTM1: n=78; 57.4%; GSTT1: n=61; 44.9%) was not significantly<br />different (p>0.05) from the controls (GSTM1: n=93; 68.4%; GSTT1: n=59; 43.4%). It was also demonstrated that risk<br />for breast cancer was increased in passive smokers carrying the GSTM1 null (OR=2.56; 95% CI=1.38-4.75) or GSTT1<br />positive (OR=2.00; 95% CI=1.05-3.83) genotypes. Moreover, risk was decreased in alcohol users carrying the GSTT1<br />null (OR=0.39; 95% CI=0.16-0.97) genotype. Conclusion: This study suggests that variants of GSTM1 and GSTT1<br />may not be risk factors for breast cancer development among Filipinos. However, the risk may be increased when these<br />genotypes were combined with lifestyle or environmental factors.