title: Upregulation of estradiol C16 alpha-hydroxylation in human breast tissue: a potential biomarker of breast cancer risk.
abstract: BACKGROUND
  The biotransformation of the natural estrogen 17 beta-estradiol (E2) via the C16 alpha-hydroxylation pathway is elevated in patients with breast cancer, in subjects at increased risk for developing breast cancer, and in c-Ha-ras-initiated mouse mammary epithelial cells.
  
  
  OBJECTIVE
  To determine whether differences in the extent of E2 C16 alpha-hydroxylation are related to the risk of developing breast cancer, we examined the extent of biotransformation of E2 via the C16 alpha-hydroxylation pathway in the mammary terminal duct lobular units (TDLUs), epithelial organoids that are a presumptive target site of human breast carcinogenesis, and in nontarget component mammary fat tissue.
  
  
  METHODS
  Noninvolved mammary tissue was obtained from four patients undergoing reduction mammoplasty and from four undergoing mastectomy for breast cancer. A radiometric assay that measures 3H2O formation caused by stoichiometric 3H exchange from [C16 alpha-3H]E2 was utilized to compare the relative extent of C16 alpha-hydroxylation in explant cultures of TDLUs and mammary fat.
  
  
  RESULTS
  The extent of E2 C16 alpha-hydroxylation was 1.83-fold higher (95% confidence interval [CI] = 1.71-1.97) in the TDLUs from reduction mammoplasty (i.e., "low-risk") patients and 7.96-fold higher (95% CI = 6.38-10.55) in the TDLUs from mastectomy (i.e., "high-risk") patients than in the corresponding values observed in the mammary fat. In the TDLUs obtained from the patients undergoing mastectomy for cancer, the extent of this metabolism was 4.56-fold higher (95% CI = 3.97-5.33) than that observed in TDLUs obtained from reduction mammoplasty patients who did not have cancer.
  
  
  CONCLUSIONS
  The increase in the extent of C16 alpha-hydroxylation of E2 in the epithelial organoids of the human breast, TDLUs in particular, may be an important factor for breast cancer induction. This upregulation may represent an endocrine biomarker for the risk of developing breast cancer.
  
  
  CONCLUSIONS
  A larger prospective study is required to confirm the clinical significance of this endocrine biomarker.
authors.affiliation: Strang-Cornell Cancer Research Laboratory, Strand Cancer Prevention Center, New York, N.Y. 10021.
authors.forename: M P
authors.initials: MP
authors.lastname: Osborne
authors.forename: H L
authors.initials: HL
authors.lastname: Bradlow
authors.forename: G Y
authors.initials: GY
authors.lastname: Wong
authors.forename: N T
authors.initials: NT
authors.lastname: Telang
mesh_terms: D000293:Adolescent; D000328:Adult; D001189:Aryl Hydrocarbon Hydroxylases; D014408:Biomarkers, Tumor / Q000378:metabolism; D001943:Breast Neoplasms / Q000201:enzymology* / Q000601:surgery; D046508:Culture Techniques; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D006801:Humans; D006900:Hydroxylation; D016462:Mammaplasty; D008408:Mastectomy; D008875:Middle Aged; D012016:Reference Values; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D014408:Biomarkers, Tumor; D004958:Estradiol; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; D039181:Steroid 16-alpha-Hydroxylase