Browsing by Author "Fong, KM"

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    Analysis of the FHIT gene and FRA3B region in sporadic breast cancer, preneoplastic lesions, and familial breast cancer probands
    (1997) Ahmadian, M; Wistuba, II; Fong, KM; Behrens, C; Kodagoda, DR; Saboorian, MH; Shay, J; Tomlinson, GE; Blum, J; Minna, JD; Gazdar, AF
    The FHIT gene, which spans the FRA3B fragile site at chromosome 3p14.2 is a candidate tumor suppressor gene in breast and other cancers. We investigated FHIT and FRA3B for loss of heterozygosity (LOH); homozygous deletions; abnormal transcripts; and acquired/germ-line point mutations in breast cancer cell lines (n = 32), breast epithelial and stromal cell cultures (n = 18), microdissected invasive (n = 16) and ductal in situ carcinomas (n = 6), and their accompanying normal and abnormal epithelial foci (n = 14). LOH at 3p14.2, especially at FHIT intragenic marker D3S1300, was found in 6 of 16 microdissected invasive tumors and 3 of 6 ductal in situ carcinomas. In accompanying preneoplastic foci, LOH occurred in two of eight intraductal hyperplasias but not in histologically normal ductal epithelium (n = 6). Three of 32 (9%) breast cancer cell lines demonstrated homozygous deletions of FHIT exon 4 (two cases) and exon 5 (one case), which correlated with exon 4-deleted transcripts and loss of the cDNA transcript containing the coding exons 5-9, respectively. Normal mammary cultures and 31 or 32 tumor cell lines (97%) expressed wild-type coding transcripts as well as a minor exon 5-deleted message. Single-strand conformation polymorphism analysis of the coding exons in the 32 tumor and 18 normal breast cell lines and their sequencing revealed four silent polymorphisms and a germ-line histidine triad point mutation (651 G-->T) in a tumor arising in a 70-year-old woman. This mutation was also present in one of her two thus far unaffected daughters. Analysis of additional DNAs from 280 probands of high-risk breast cancer families for other FHIT exon 8 mutations detected an intronic point mutation 13 bases upstream of exon 8. Thus, we have demonstrated relatively early abnormalities of the FHIT/FRA3B region in breast cancer and discovered two rare FHIT germ-line mutations. The expression of a transcript containing the coding exons in nearly all cell lines, including those with germ-line mutations, suggests the possibility that another gene in the FRA3B region may be involved in the pathogenesis of breast cancer.
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    Molecular damage in the bronchial epithelium of current and former smokers
    (1997) Wistuba, II; Lam, S; Behrens, C; Virmani, AK; Fong, KM; LeRiche, J; Samet, JM; Srivastava, S; Minna, JD; Gazdar, AF
    Background: Most lung cancers are attributed to smoking, These cancers have been associated with multiple genetic alterations and with the presence of preneoplastic bronchial lesions, In view of such associations, we evaluated the status of specific chromosomal loci in histologically normal and abnormal bronchial biopsy specimens from current and former smokers and specimens from nonsmokers, Methods: Multiple biopsy specimens were obtained from 18 current smokers, 24 former smokers, and 21 nonsmokers, Polymerase chain reaction-based assays involving 15 polymorphic microsatellite DNA markers were used to examine eight chromosomal regions for genetic changes (loss of heterozygosity [LOH] and microsatellite alterations), Results: LOH and microsatellite alterations were observed in biopsy specimens from both current and former smokers, but no statistically significant differences were observed between the two groups. Among individuals with a history of smoking, 86% demonstrated LOH in one or more biopsy specimens, and 24% showed LOH in all biopsy specimens, About half of the histologically normal specimens from smokers showed LOH, but the frequency of LOH and the severity of histologic change did not correspond until the carcinoma in situ stage, A subset of biopsy specimens from smokers that exhibited either normal or preneoplastic histology showed LOH at multiple chromosomal sites, a phenomenon frequently observed in carcinoma in situ and invasive cancer, LOH on chromosomes 3p and 9p was more frequent than LOH on chromosomes 5q, 17p (17p13; TP53 gene), and 13q (13q14; retinoblastoma gene), Microsatellite alterations were detected in 64% of the smokers, No genetic alterations were detected in nonsmokers, Conclusions: Genetic changes similar to those found in lung cancers can be detected in the nonmalignant bronchial epithelium of current and former smokers and may persist for many years after smoking cessation.