RT Journal Article
SR Electronic
T1 Selective Inhibitors of Vitamin D Metabolism - New Concepts and Perspectives
JF Anticancer Research
JO Anticancer Res
FD International Institute of Anticancer Research
SP 2653
OP 2668
VO 26
IS 4A
A1 INGE SCHUSTER
A1 HELMUT EGGER
A1 GERDA HERZIG
A1 G.SATYANARAYANA REDDY
A1 JOHANNES A. SCHMID
A1 MONIKA SCHÜSSLER
A1 GEORG VORISEK
YR 2006
UL http://ar.iiarjournals.org/content/26/4A/2653.abstract
AB Background: Levels of active vitamin D (VD) are controlled by synthesis via CYP27B1 and self-induced metabolism by CYP24A1. Unbalanced high CYP24A1 expression due to induction by diverse endogenous compounds and xenobiotics, and amplification found in various tumours, might lead to local VD deficiency, thereby causing/reinforcing disorders. Materials and Methods: Using primary human keratinocytes, CYP24A1 expression was examined at the mRNA level by dot-blot and Northern blot hybridization, and at the enzyme activity level by analysing HPLC profiles from incubations with 3H-labelled VD metabolites. Results: We have developed a one-step protocol to screen test compounds for potent inhibition of CYP24A1 along with selectivity over CYP27B1 and adequate metabolic stability. These inhibitors amplified hormone levels and, thereby, its function, indicated by increased CYP24A1 expression. Moreover, they stabilized the expression of a CYP24A1 splice variant, possibly serving as a buffer of VD metabolites. In addition, a low abundant, constitutive 24-hydroxylase, active in the low nanomolar range is described. Conclusion: Selective CYP24A1 inhibitors could herald a new era for vitamin D research, as well as for therapeutic application. Inhibitors may be used as single entities or in combination with low doses of potent analogs to prevent and treat various defects of growth and differentiation, and neuro-immuno-endocrine disorders. Copyright© 2006 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved