Breast cancer risk and genetic ancestry: a case-control study in Uruguay

Background: Uruguay exhibits one of the highest rates of breast cancer in Latin America, similar to those of developed nations, the reasons for which are not completely understood. In this study we investigated the effect that ancestral background has on breast cancer susceptibility among Uruguayan women. Methods: We carried out a case-control study of 328 (164 cases, 164 controls) women enrolled in public hospitals and private clinics across the country. We estimated ancestral proportions using a panel of nuclear and mitochondrial ancestry informative markers (AIMs) and tested their association with breast cancer risk. Results: Nuclear individual ancestry in cases was (mean +/- SD) 9.8 +/- 7.6% African, 13.2 +/- 10.2% Native American and 77.1 +/- 13.1% European, and in controls 9.1 +/- 7.5% African, 14.7 +/- 11.2% Native American and 76.2 +/- 14.2% European. There was no evidence of a difference in nuclear or mitochondrial ancestry between cases and controls. However, European mitochondrial haplogroup H was associated with breast cancer (OR = 2.0; 95% CI 1.1, 3.5). Conclusions: We have not found evidence that overall genetic ancestry differs between breast cancer patients and controls in Uruguay but we detected an association of the disease with a European mitochondrial lineage, which warrants further investigation.