Activation of genotoxins to DNA-damaging species in exfoliated breast milkcells

Exfoliated cells, isolated from breast milk samples donated by UK-resident women (n=15), were incubated, either immediately or after culture for 7 day s, with one of a series of genotoxins, either in the presence or absence of the DNA-repair inhibitors, hydroxyurea (HU), and cytosine arabinoside (ara -C). The numbers of DNA single-strand breaks induced were then assessed as comet tail length (CTL) (mum) using the alkaline single cell-gel electropho resis ('Comet') assay; cell viability was measured by trypan blue exclusion . The heterocyclic aromatic amines (HAAs) (2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP) (0.4 mM), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indol e (Trp-P-1) (1.67 mM), 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) (1 .77 mM)), a polycyclic aromatic hydrocarbon (benzo[a]pyrene (B[a]P) (0.36 m M)), a nitro-polycyclic aromatic hydrocarbon (l-nitropyrene (1-NP) (1.84 mM )) and aromatic amines (o-toluidine (0.85 mM), p-chloroaniline (0.71 mM)) e ach induced statistically significant (P<0.0001, Mann-Whitney test) increas es in median CTLs in breast milk cells from all the donors examined when in cubated (30 min, 37<degrees>C) in the presence of HU/ara-C. In some cases, these compounds were also active in the absence of the repair inhibitors. T here were marked Variations in comet formation between donors and between g enotoxins. Cell culture appeared to increase the epithelial cell proportion and cultured cells retained their ability to activate genotoxins. The resu lts suggest that breast milli is a valuable source of human mammary cells f or the study of the metabolic activation of possible carcinogens. (C) 2000 Elsevier Science B.V. All rights reserved.