EXFOLIATED DUCTAL EPITHELIAL-CELLS IN HUMAN BREAST-MILK - A SOURCE OFTARGET TISSUE DNA FOR MOLECULAR EPIDEMIOLOGIC STUDIES OF BREAST-CANCER

Studies of biomarkers of putative breast carcinogens, such as DNA addu cts, have been limited by the difficulty in obtaining representative d uctal epithelial cells (DECs) from breast tissue, In this feasibility study, we sought to ascertain if exfoliated DECs in breast milk could be a source of DNA for biomarker studies, Specimens (n = 38) were coll ected over 24 h from nursing women, and a questionnaire was administer ed, Cell pellets were isolated by repeated centrifugation and washing, Pellets were resuspended and incubated for 2 h, with glass adherence used to remove monocytes, resulting in an enrichment of DECs of >80%, Nonadherent cells were removed, washed, and homogenized for DNA isolat ion, Accurate DNA quantification was performed by P-32-postlabeling of normal nucleotides under conditions of excess ATP, Although there was wide variability in the amounts of DNA recovered, DNA yield was signi ficantly associated with the number of weeks postpartum (P < 0.01), wi th optimal yield between 6 and 8 weeks after birth, There were no sign ificant associations (P < 0.05) between the number of cells recovered and milk volume, method of collection, or the number of samples in a 2 4-h period per individual, This study demonstrates that breast milk ca n be used as a source of DECs for biomarker studies of gene-environmen t interaction and that sufficient DNA can be recovered to evaluate car cinogen-DNA adducts and to perform genotyping assays, Using this appro ach, exfoliated DECs may serve as a source of representative cells for studies of breast carcinogenesis and biomarkers of exposure, suscepti bility, and effect.