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  • 1
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 17β-Hydroxysteroid dehydrogenase (17HSD) is one of the key enzymes in estrogen metabolism, catalyzing the reversible reaction between estradiol and the less active estrogen, estrone. The gene encoding this enzyme, EDH17B2, has been mapped to chromosome 17, region q12–q21, in the vicinity of BRCA1, an as yet unidentified gene that appears to be involved in familial breast cancer and in familial ovarian cancer. The possibility that EDH17B2 gene is the same as BRCA1 was tested by screening for mutations in the coding regions of EDH17B2, using a polymerase chain reaction/single-strand conformation polymorphism method. An A→G transition creating a new BstUI site at exon 6 was the only frequent sequence alteration found in the coding region of the gene. This mutation also led to an amino acid substitution of serine to glycine at position 312 (312S→312G) in the 17HSD protein. Since the nucleotide change was detected both in specimens from patients with familial or sporadic cancer and in control samples, and at similar rates, this mutation appears to be of a polymorphic nature. In addition, a rare polymorphism located at intron 5 was detected. This C→T substitution creates a BbvI site and is not thought to have any effect on 17HSD activity. The results indicate that there are no major alterations in the coding areas of EDH17B2 and thus studies testing the hypothesis that EDH17B2 may be the same as BRCA1 should be extended to the promoter and regulatory elements of EDH17B2.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-7217
    Keywords: breast cells ; estrogens ; hydroxysteroid dehydrogenases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 17β‐hydroxysteroid dehydrogenase activity represents a group of several isoenzymes (17HSDs) that catalyze the interconversion between highly active 17β‐hydroxy‐ and low activity 17‐ketosteroids and thereby regulate the biological activity of sex steroids. The present study was carried out to characterize the expression of 17HSD isoenzymes in human mammary epithelial cells and breast tissue. In normal breast tissues 17HSD types 1 and 2 mRNAs were both evenly expressed in glandular epithelium. In two human mammary epithelial cell lines, mRNAs for 17HSD types 1, 2 and 4 were detected. In enzyme activity measurements only oxidative 17HSD activity, corresponding to either type 2 or type 4 enzyme, was present. The role of 17HSD type 4 in estrogen metabolism was further investigated, using several cell lines originating from various tissues. No correlation between the presence of 17HSD type 4 mRNA and 17HSD activity in different cultured cell lines was detected. Instead, oxidative 17HSD activity appeared in cell lines where 17HSD type 2 was expressed and reductive 17HSD activity was present in cells expressing 17HSD type 1. These data strongly suggest that in mammary epithelial cell lines the oxidative activity is due to type 2 17HSD and that oxidation of 17β‐hydroxysteroids is not the primary activity of the 17HSD type 4 enzyme.
    Type of Medium: Electronic Resource
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