Genetic alterations in 'normal' luminal and myoepithelial cells of the breast.
ABSTRACT Chromosomal loci exhibiting loss of heterozygosity (LOH) at high frequency in invasive breast cancer have been investigated in 'normal' breast tissue from patients with carcinoma and from reduction mammoplasty specimens. Duct-lobular units dissected from paraffin-embedded tissues and 485 'normal' luminal and myoepithelial cell clones were studied. Overall, LOH was found in normal cells in 5/10 breast cancer cases and 1/3 reduction mammoplasty specimens. LOH was identified in normal cells adjacent to and distant from the tumour. In one case, all luminal and myoepithelial samples exhibited loss of the same allele on chromosome 13q. One case in which the patient had a germline truncating mutation in the BRCA1 gene exhibited LOH on 17q in 3/33 normal clones. One of these clones showed loss of wild-type allele indicating gene inactivation. This sample also had LOH at markers on chromosomes 11p and 13q. One of 93 clones from three reduction mammoplasties showed allele loss at a locus on chromosome 13q. The identification of LOH in breast lobules suggests that they may be clonal. The demonstration of genetic alteration in luminal and myoepithelial cells provides evidence for the presence of a common stem cell for the two epithelial cell types. LOH has been demonstrated in normal tissues near and away from the carcinoma, suggesting that genetic alterations are likely to be more heterogeneous and widespread than is currently envisaged, and probably occur very early in breast development. Homozygous deletion of BRCA1 per se does not appear to provide clonal advantage.
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ABSTRACT: The BRCA1 gene on human chromosome 17q21 is responsible for an autosomal dominant syndrome of inherited early onset breast/ovarian cancer. It is estimated that women harboring a germline BRCA1 mutation incur an 85% lifetime risk of breast cancer and a greatly elevated risk of ovarian cancer. The BRCA1 gene has recently been isolated and mutations have been found in the germline of affected individuals in linked families. Previous studies of loss of heterozygosity (LOH) in breast tumors have been carried out on sporadic tumors derived from individuals without known linkage to BRCA1 and on tumors from linked families. Loss of large regions of chromosome 17 has been observed, but these LOH events could not be unequivocally ascribed to BRCA1. We have studied 28 breast and 6 ovarian tumors from families with strong evidence for linkage between breast cancer and genetic markers flanking BRCA1. These tumors were examined for LOH using genetic markers flanking and within BRCA1, including THRA1, D17S856, EDH17B1, EDH17B2, and D17S183. Forty-six percent (16/34) of tumors exhibit LOH which includes BRCA1. In 8 of 16 tumors the parental origin of the deleted allele could be determined by evaluation of haplotypes of associated family members; in 100% of these cases, the wild-type allele was lost. In some of these families germline mutations in BRCA1 have been determined; analyses of tumors with LOH at BRCA1 have revealed that only the disease-related allele of BRCA1 was present. These data strongly support the hypothesis that BRCA1 is a tumor suppressor gene.Clinical Cancer Research 06/1995; 1(5):539-44. · 7.84 Impact Factor
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ABSTRACT: Cell cultures were derived from normal and cancerous breast tissues and from metastases by methods that selected for relatively adherent epithelial aggregates. Karyotypic analyses of first or second passage cultures yielded predominantly normal diploid cells. Nonclonal aberrations were more common in tumor-derived than in normal cultures. Three of the cultures that originated from metastases were characterized by abnormal clones. These results support observations based on DNA content, which indicate that a considerable fraction of breast cancers are composed predominantly of diploid cells. They differ greatly from chromosomal findings in long-term cultures of tumor effusions and thus emphasize the karyotypic diversity that can be found in tumors from a single tissue of origin--the breast.Cancer Genetics and Cytogenetics 04/1985; 16(1):49-64. · 1.93 Impact Factor
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ABSTRACT: Previously, we developed methodology for studying allelic imbalance (AI) in preinvasive breast disease and showed that AI identified at various chromosomal loci in invasive carcinoma is already present in in situ carcinoma and atypical hyperplasia. We now extend this work by looking for Ai in hyperplasia of usual type (HUT), apocrine cysts (AC), and papilloma (Pap) of the breast. HUT, AC, and Pap were identified in formalin-fixed, paraffin-embedded sections of benign breast biopsies and isolated using a microdissection technique. AI was investigated using polymorphic microsatellite markers and PCR. AI was identified in 3/23 (13%) informative cases of HUT at 17q (D17S250), 2/43 (4.7%) at 17p (D17S796), 1/22 (4.5%) at 16q (D16S413), and 0/18 (0%) at 13q (D13S267). No particular histologic feature of HUT predicted the presence of AI. No examples of AC or Pap exhibited AI at any of the markers studied. AI previously identified at various chromosomal loci in invasive carcinoma, in situ carcinoma, and atypical hyperplasia is present at low frequency in HUT in benign breast biopsies but not in AC or Pap. The possibility that AI in the latter could be masked by contamination from stromal and myoepithelial cells cannot, however, be excluded at this stage. At least a proportion of HUT thus appear to be clonal (neoplastic) rather than hyperplastic proliferations as their name suggests. The significance of AI in the pathogenesis of HUT or its subsequent progression to carcinoma is not yet clear and requires further investigation.Laboratory Investigation 02/1996; 74(1):129-35. · 3.96 Impact Factor