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

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.

XRCC4 c.1394G>T Single Nucleotide Polymorphisms and Breast Cancer Risk among Filipinos

Background: The identification of cancer-associated single nucleotide polymorphisms (SNP) and mutation genes is a promising approach in recognizing individuals who are at risk of developing cancer. Hence, this study was conducted to determine the association between XRCC4 c.1394G>T SNP and breast cancer development among Filipinos. Methods: Genotyping for XRCC4 c.1394G>T SNP was performed on breast cancer patients (n=103) and their age- and sex- matched clinically healthy controls (n=103) by polymerase chain reaction ­ restriction fragment length polymorphism. Results: Significant difference in genotype (p=0.007) and allele (p=0.003) frequencies in XRCC4 c.1394G>T was observed between the breast cancer cases and controls. Carriers of the XRCC4 c.1394 G>T genotype were observed to have significantly higher risk of developing breast cancer compared to individuals with T/T genotype (OR=2.67, 95% CI: 1.36 ­ 5.25). XRCC4 c.1394G>T combined with passive smoking may also significantly increase risk of breast cancer (OR=14.73; 95% CI= 9.88-18.86). Conclusion: XRCC4 c. 1394G>T may be associated with breast cancer development among Filipinos.