Effect of 25-hydroxyvitamin D3 and 1 α,25 dihydroxyvitamin D3 on differentiation and apoptosis of human osteosarcoma cell lines

Osteosarcoma (OS) is a malignant bone tumor predominantly affecting children and adolescents. OS has a 60% survival rate with current treatments; hence, there is a need to identify novel adjuncts to chemotherapeutic regimens. In this pilot study, we investigated the dose-response to 1a,25-dihdroxyvitamin D3 (1,a 25(OH)2D3) and 25-hydroxyvitamin D3 (25(OH)D3) by human OS cell lines, SaOS-2, and 143B. We hypothesized that 1,a 25(OH)2D3 and 25(OH)D3 would stimulate differentiation and induce apoptosis in OS cells in a dose-dependent manner. Human OS cell lines, SaOS-2, and 143B, were treated with 1,a 25(OH)2D3 or 25(OH)D3 or an ethanol control, respectively, at concentrations ranging from 1 to 1,000?nM. Ki67 (a marker of cellular proliferation) immunocytochemistry revealed no significant changes in the expression of Ki-67 or MIB-1 in 1a,25(OH)2D3 or 25(OH)D3 treated SaOS-2 or 143B cells. Both control and 1a,25(OH)2D3 treated SaOS-2 and 143B cells expressed vitamin D receptor (VDR). Markers of osteoblastic differentiation in 143B cells and SaOS-2 cells were induced by both 25(OH)D3 and 1a,25(OH)2D, and evident by increases in alkaline phosphatase (ALP) activity, osteocalcin (OCN) mRNA expression, and mineralization of extra-cellular matrix (ECM) by alizarin red staining. An increasing trend in apoptosis in response to 25(OH)D3, in both SaOS-2 and 143B cells was detected by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) staining. With 1a,25(OH)2D3 treatment, apoptosis was evident at higher concentrations only. These preliminary findings suggest that OS cells express VDR and respond to 25(OH)D3 and 1a,25(OH)2D3 by undergoing differentiation and apoptosis. (C) 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:831844, 2012