Morphological transformation of C3H/M2 mouse fibroblasts by, and genotoxicity of, extracts of human milk

Breast cancer may be initiated by environmental/dietary agents and human mi lk may act as an ex vivo indicator of in vivo exposure of mammary epithelia l cells to genotoxins. Extracts of human milk from UK-resident women (n = 7 ) were tested for their abilities to morphologically transform C3H/M2 mouse fibroblasts. Genotoxicities were assessed in the Salmonella typhimurium re verse-mutation assay in the presence of S9 using strains TA1538 and YG1019, and in metabolically-competent human MCL-5 cells with the micronucleus and with the alkaline single cell gel electrophoresis (comet) assays. Two of t he seven extracts were inactive in the transformation assay both in the pre sence or absence of S9, two appeared to be equally transforming either in t he presence or absence of S9, and two other extracts induced increased tran sformation frequencies in the presence of S9. A seventh extract, tested onl y in the absence of S9, was inactive. Extracts were either active or inacti ve in at least three of the four tests applied. Four extracts were active o r inactive in all four tests. The results suggest that human milk could be used as a resource for investigations of the as-yet-unidentified transformi ng agents previously detected in mammary lipid. (C) 2001 Elsevier Science B .V. All rights reserved.