title: Mechanism of the anti-proliferative action of 25-hydroxy-19-nor-vitamin D(3) in human prostate cells.
abstract: According to the prevailing paradigm, 1α-hydroxylation of 25-hydroxyvitamin D(3) (25(OH)D(3)) and its analogs is a pre-requisite step for their biological effects. We previously reported that 25-hydroxy-19-nor-vitamin D(3) (25(OH)-19-nor-D(3)) had anti-proliferative activity in a cell line, PZ-HPV-7, which was derived from human non-cancerous prostate tissue, and suggested that 25(OH)-19-nor-D(3) acted after 1α-hydroxylation by vitamin D 1α-hydroxylase (CYP27B1). However, metabolic studies of 25(OH)-19-nor-D(3) using recombinant CYP27B1 revealed that 25(OH)-19-nor-D(3) was rarely subjected to 1α-hydroxylation. Therefore, in this report, we attempted to clarify the mechanism of 25(OH)-19-nor-D(3) action in intact cells using PZ-HPV-7 prostate cells. After incubating the cells with 25(OH)-19-nor-D(3), eight metabolites of 24-hydroxylase (CYP24A1) were detected, whereas no products of CYP27B1 including 1α,25-dihydroxy-19-nor-vitamin D(3) (1α,25(OH)(2)-19-nor-D(3)) were found. Furthermore, the time-dependent nuclear translocation of vitamin D receptor (VDR) and the subsequent transactivation of cyp24A1 gene in the presence of 25(OH)-19-nor-D(3) were almost identical as those induced by 1α,25(OH)(2)-19-nor-D(3). These results strongly suggest that 25(OH)-19-nor-D(3) directly binds to VDR as a ligand and transports VDR into the nucleus to induce transcription of cyp24A1 gene. In addition, knock down of cyp27B1 gene did not affect the anti-proliferative activity of 25(OH)-19-nor-D(3), whereas knock down of VDR attenuated the inhibitory effect. Thus, our results clearly demonstrate that the anti-proliferative activity of 25(OH)-19-nor-D(3) is VDR dependent but 1α-hydroxylation independent, suggesting that 25(OH)D(3) analogs such as 25(OH)-19-nor-D(3) could be attractive candidates for anticancer therapy.
authors.affiliation: Department of Biotechnology, Faculty of Engineering, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Munetsuna
authors.forename: Sachie
authors.initials: S
authors.lastname: Nakabayashi
authors.forename: Rie
authors.initials: R
authors.lastname: Kawanami
authors.forename: Kaori
authors.initials: K
authors.lastname: Yasuda
authors.forename: Miho
authors.initials: M
authors.lastname: Ohta
authors.forename: Midori A
authors.initials: MA
authors.lastname: Arai
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kittaka
authors.forename: Tai C
authors.initials: TC
authors.lastname: Chen
authors.forename: Masaki
authors.initials: M
authors.lastname: Kamakura
authors.forename: Shinichi
authors.initials: S
authors.lastname: Ikushiro
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Sakaki
mesh_terms: D015153:Blotting, Western; D002117:Calcitriol / Q000494:pharmacology*; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002762:Cholecalciferol; D006801:Humans; D021381:Protein Transport / Q000187:drug effects / Q000235:genetics; D034741:RNA, Small Interfering; D018167:Receptors, Calcitriol / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013250:Steroid Hydroxylases / Q000235:genetics / Q000378:metabolism; D065668:Vitamin D3 24-Hydroxylase
chemical_list: D034741:RNA, Small Interfering; D018167:Receptors, Calcitriol; D002762:Cholecalciferol; D013250:Steroid Hydroxylases; C585549:CYP24A1 protein, human; D065668:Vitamin D3 24-Hydroxylase; D002117:Calcitriol