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