Effect of 25-hydroxyvitamin D 3 and 1 α,25 dihydroxyvitamin D 3 on differentiation and apoptosis of human osteosarcoma cell lines

Abstract

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 1α,25- dihdroxyvitamin D 3 (1,α 25(OH) 2D 3) and 25-hydroxyvitamin D 3 (25(OH)D 3) by human OS cell lines, SaOS-2, and 143B. We hypothesized that 1,α 25(OH) 2D 3 and 25(OH)D 3 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,α 25(OH) 2D 3 or 25(OH)D 3 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 1α,25(OH) 2D 3 or 25(OH)D 3 treated SaOS-2 or 143B cells. Both control and 1α,25(OH) 2D 3 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)D 3 and 1α,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)D 3, in both SaOS-2 and 143B cells was detected by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) staining. With 1α,25(OH) 2D 3 treatment, apoptosis was evident at higher concentrations only. These preliminary findings suggest that OS cells express VDR and respond to 25(OH)D 3 and 1α,25(OH) 2D 3 by undergoing differentiation and apoptosis. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc.