Mechanism of the anti-proliferative action of 25-hydroxy-19-nor-vitamin D(3) in human prostate cells

• Published in: Journal of molecular endocrinology Vol. 47; no. 2; pp. 209 - 218
• Main Authors: Munetsuna, Eiji, Nakabayashi, Sachie, Kawanami, Rie, Yasuda, Kaori, Ohta, Miho, Arai, Midori A, Kittaka, Atsushi, Chen, Tai C, Kamakura, Masaki, Ikushiro, Shinichi, Sakaki, Toshiyuki
• Format: Journal Article
• Language: English
• Published: England 01.10.2011
• Subjects: Blotting, Western; Calcitriol - pharmacology; Cell Line; Cell Proliferation - drug effects; Cholecalciferol; Humans; Protein Transport - drug effects; Protein Transport - genetics; Receptors, Calcitriol - genetics; Receptors, Calcitriol - metabolism; Reverse Transcriptase Polymerase Chain Reaction; RNA, Small Interfering; Steroid Hydroxylases - genetics; Steroid Hydroxylases - metabolism; Vitamin D3 24-Hydroxylase
• ISSN: 1479-6813
• DOI: 10.1530/JME-11-0008

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.