Dietary and/or environmental factors appear to play a key role in the international variations that exist in @entity0 incidence. The genotoxicity of breast milk extracts is being examined as a possible indicator of in vivo exposure of mammary epithelial cells to DNA-damaging agents. Breast milk samples were obtained from the UK (n = 32), a high risk country, and from Hong Kong (n = 10), India (n = 20) and Singapore (n = 20), countries of lower @entity0 incidence. The abilities of breast milk extracts to induce DNA damage detected as single-strand breaks (SSBs) in the alkaline Comet assay and to induce micronuclei in @entity1 cells and mutations in @entity2491 YG1019 were investigated. In the Comet assay 18 of 32 (56%) UK samples induced significant increases in DNA SSBs compared with 2 of 10 (20%), 5 of 20 (25%) and 8 of 20 (40%) of the samples from Hong Kong, India and Singapore, respectively. The proportion of positive samples was significantly higher in the UK group than in the combined low @entity0 incidence group and significantly higher than in the Indian group (P < 0.05, Fisher's exact test). In the micronucleus assay 9 of 32 (28%) UK samples showed significant activity compared with 0 of 10 (0%), 2 of 20 (10%) and 3 of 20 (15%) of the samples from Hong Kong, India and Singapore, respectively. Extracts of all the aforementioned milk samples were also tested for bacterial mutagenicity. Nine of 32 (28%) UK samples induced significant activity with a dose-response effect. Although activity was detected in samples from the other countries, comparable dose-response data could not be obtained because of a lack of material. This pilot study suggests that genotoxic components occur more frequently in UK breast milk than in milk from some other countries with a lower incidence of @entity5 . More work is required to confirm these initial findings and to examine their relevance to variations in @entity0 incidence.

Genotoxicity of XXXX breast milk from different countries.

@entity1 :: ('9606', 'Species') :: ['MCL-5'] @entity5 :: ('MESH:D009369', 'Disease') :: ['cancer'] @entity2491 :: ('90371', 'Species') :: ['Salmonella typhimurium'] @entity0 :: ('MESH:D001943', 'Disease') :: ['breast cancer']
@entity1 :: (9606,Species) :: ['human']
