title: Variability in loss of constitutional heterozygosity across loci and among individuals: association with candidate genes in ductal breast carcinoma.
abstract: Genes involved in the metabolic activation or detoxification of environmental carcinogens may contribute to breast cancer susceptibility by influencing rates of somatic mutation. To examine this hypothesis, we studied the association between loss of constitutional heterozygosity (LOH) in ductal breast tumors and allelic variability in genes that regulate the metabolism of environmental carcinogens. LOH was measured by typing the tumor and normal tissue of 28 breast cancer cases at 33 chromosomal loci by using highly polymorphic tetranucleotide repeat markers. Genotypes in non-tumor tissue were also measured at the cytochrome P450 1A1 (CYP1A1), cytochrome P450 2D6 (CYP2D6), glutathione-s-transferase mu (GSTM), epoxide hydrolase (EH), and NAD(P)H:quinone oxidoreductase (NQO1) loci. The observed proportion of LOH was 11% overall and ranged from 0% to 37% across loci. LOH greater than 20% was observed on chromosomes 1p, 2p, 10q, 11q, 17p, and 18q. The observed proportion of LOH ranged from 0% to 67% among individuals. An elevated proportion of LOH was observed for genotypes at CYP2D6 (17% for the 1/1 and 1/2 genotypes vs 8% for the 2/ 2 genotype), NQO1 (13% for the 1/2 and 2/2 genotypes vs 8% for the 1/1 genotype), and GSTM (15% for the null genotype vs 7% for the wild-type genotype). No elevated proportion of LOH was observed for genotypes at CYP1A1 (12% for the 1/2 genotype vs 10% for the 1/1 genotype) or EH (11% for the 1/1 genotype vs 10% for the 1/2 genotype). There was no correlation of LOH with any other tumor characteristic such as estrogen- or progesterone-receptor status or number of positive lymph nodes. These results suggest that the proportion of LOH varies substantially across loci and among individuals. Interindividual variability in LOH may thus be explained in part by genes that regulate the metabolism of environmental carcinogens.
authors.affiliation: Department of Biostatistics and Epidemiology, University of Pennsylvania School of Medicine, Philadelphia 19104-6021, USA.
authors.forename: T R
authors.initials: TR
authors.lastname: Rebbeck
authors.forename: A K
authors.initials: AK
authors.lastname: Godwin
authors.forename: K H
authors.initials: KH
authors.lastname: Buetow
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000201:enzymology / Q000235:genetics*; D018270:Carcinoma, Ductal, Breast / Q000201:enzymology / Q000235:genetics*; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics; D019389:Cytochrome P-450 CYP2D6 / Q000235:genetics; D004851:Epoxide Hydrolases / Q000235:genetics; D005260:Female; D017353:Gene Deletion; D005838:Genotype; D005982:Glutathione Transferase / Q000235:genetics; D006579:Heterozygote; D006801:Humans; D007206:Individuality; D008875:Middle Aged; D011110:Polymorphism, Genetic; D011808:Quinone Reductases / Q000235:genetics
chemical_list: D019363:Cytochrome P-450 CYP1A1; D019389:Cytochrome P-450 CYP2D6; C041831:NADH dehydrogenase (quinone); D011808:Quinone Reductases; D005982:Glutathione Transferase; D004851:Epoxide Hydrolases