Structural basis for the selective inhibition of human 3beta-hydroxysteroid dehydrogenase 1 in human breast tumor MCF-7 cells.

Abstract

Human 3beta-hydroxysteroid dehydrogenase/isomerase type 1 (3beta-HSD1) is a critical enzyme in the conversion of DHEA to estradiol in breast tumors and may be a target enzyme for inhibition in the treatment of breast cancer in postmenopausal women. Human 3beta-HSD2 participates in the production of cortisol and aldosterone in the human adrenal gland in this population. In our recombinant human breast tumor MCF-7 Tet-off cells that express either 3beta-HSD1 or 3beta-HSD2, trilostane and epostane inhibit the DHEA-induced proliferation of MCF-7 3beta-HSD1 cells with 12- to 16-fold lower IC(50) values compared to the MCF-7 3beta-HSD2 cells. The compounds also competitively inhibit purified human 3beta-HSD1 with 12- to 16-fold lower K(i) values compared to the noncompetitive K(i) values measured for human 3beta-HSD2. Using our structural model of 3beta-HSD1, trilostane or 17beta-acetoxy-trilostane was docked in the active site of 3beta-HSD1, and Arg195 in 3beta-HSD1 or Pro195 in 3beta-HSD2 was identified as a potentially critical residue (one of 23 non-identical residues in the two isoenzymes). The P195R mutant of 3beta-HSD2 were created, expressed and purified. Kinetic analyses of enzyme inhibition suggest that the high affinity, competitive inhibition of 3beta-HSD1 by trilostane and epostane may be related to the presence of Arg195 in 3beta-HSD1 vs. Pro195 in 3beta-HSD2.

• Authors: James L Thomas, Kevin M Bucholtz, Jingping Sun, Vance L Mack, Balint Kacsoh
• Journal: Molecular and cellular endocrinology (Mol Cell Endocrinol) Vol. 301 Issue 1-2 Pg. 174-82 (Mar 25 2009) ISSN: 0303-7207 [Print] Ireland
• PMID: 18955108 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Aromatase Inhibitors
• Coenzymes
• Enzyme Inhibitors
• Mutant Proteins
• RNA, Messenger
• Dihydrotestosterone
• Estrone
• Dehydroepiandrosterone
• Estradiol
• Arginine
• 3-Hydroxysteroid Dehydrogenases
• trilostane

Topics

• 3-Hydroxysteroid Dehydrogenases (antagonists & inhibitors, chemistry)
• Arginine (metabolism)
• Aromatase Inhibitors (pharmacology)
• Blotting, Western
• Breast Neoplasms (enzymology, genetics)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Coenzymes (metabolism)
• Dehydroepiandrosterone (pharmacology)
• Dihydrotestosterone (analogs & derivatives, pharmacology)
• Enzyme Inhibitors (pharmacology)
• Estradiol (pharmacology)
• Estrone (pharmacology)
• Female
• Gene Expression Regulation, Enzymologic (drug effects)
• Gene Expression Regulation, Neoplastic (drug effects)
• Humans
• Kinetics
• Mutant Proteins (metabolism)
• RNA, Messenger (genetics, metabolism)
• Reverse Transcriptase Polymerase Chain Reaction
• Substrate Specificity (drug effects)