Simple tandem repeat (TTTA)n polymorphism in CYP19 (aromatase) gene and breast cancer risk in Nigerian women

BACKGROUND Breast cancer is the most common cancer and the leading cause of cancer related deaths in women worldwide. The incidence of the disease is increasing globally and this increase is occurring at a faster rate in population groups that hirtherto enjoyed low incidence. This study was designed to evaluate the role of a simple tandem repeat polymorphism (STRP) in the aromatase (CYP19) gene in breast cancer susceptibility in Nigerian women, a population of indigenous sub-Saharan African ancestry. METHODS A case-control study recruiting 250 women with breast cancer and 250 women without the disease from four University Teaching Hospitals in Southern Nigeria was carried out between September 2002 and April 2004. Participants were recruited from the surgical outpatient clinics and surgical wards of the Nigerian institutions. A polymerase chain reaction (PCR)-based assay was employed for genotyping and product sizes were detected with an ABI 3730 DNA Analyzer. RESULTS Conditional logistic regression analysis revealed that harboring the putative high risk genotypes conferred a 29% increased risk of breast cancer when all women in the study were considered (Odds ratio [OR] = 1.29, 95% confidence interval [CI] 0.83-2.00), although this association was not statistically significant. Subgroup analysis based on menopausal status showed similar results among premenopausal women (OR = 1.35, 95% CI 0.76-2.41 and postmenopausal women (OR = 1.27, 95% CI 0.64-2.49). The data also demonstrated marked differences in the distribution of (TTTA)n repeats in Nigerian women compared with other populations. CONCLUSION This study has shown that harboring 10 or more repeats of the microsatellite (TTTA)n repeats of the CYY19 gene is associated with a modest increased risk of breast cancer in Nigerian women.