%0 Journal Article
%T In Vitro Characterization of Valproic Acid, ATRA, and Cytarabine Used for Disease-Stabilization in Human Acute Myeloid Leukemia: Antiproliferative Effects of Drugs on Endothelial and Osteoblastic Cells and Altered Release of Angioregulatory Mediators by Endothelial Cells
%A Hilde Kvestad
%A Lasse Evensen
%A James B. Lorens
%A £¿ystein Bruserud
%A Kimberley J. Hatfield
%J Leukemia Research and Treatment
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/143479
%X The combined use of the histone deacetylase inhibitor valproic acid (VPA), the retinoic acid receptor-¦Á agonist all-trans retinoic acid (ATRA), and the deoxyribonucleic acid polymerase-¦Á inhibitor cytarabine (Ara-C) is now considered for disease-stabilizing treatment of acute myeloid leukemia (AML). Leukemogenesis and leukemia cell chemoresistance seem to be supported by neighbouring stromal cells in the bone marrow, and we have therefore investigated the effects of these drugs on primary human endothelial cells and the osteoblastic Cal72 cell line. The results show that VPA and Ara-C have antiproliferative effects, and the antiproliferative/cytotoxic effect of Ara-C was seen at low concentrations corresponding to serum levels found during low-dose in vivo treatment. Furthermore, in functional assays of endothelial migration and tube formation VPA elicited an antiangiogenic effect, whereas ATRA elicited a proangiogenic effect. Finally, VPA and ATRA altered the endothelial cell release of angiogenic mediators; ATRA increased levels of CXCL8, PDGF-AA, and VEGF-D, while VPA decreased VEGF-D and PDGF-AA/BB levels and both drugs reduced MMP-2 levels. Several of these mediators can enhance AML cell proliferation and/or are involved in AML-induced bone marrow angiogenesis, and direct pharmacological effects on stromal cells may thus indirectly contribute to the overall antileukemic activity of this triple drug combination. 1. Introduction Acute myeloid leukemia (AML) is an aggressive bone marrow malignancy and several studies have demonstrated that different types of bone marrow stromal cells support leukemogenesis, including the maintenance of leukemic stem/progenitor cells in osteoblast-containing endosteal niches and in endothelium-containing vascular niches in the bone marrow [1, 2]. Studies of antileukemic drugs mainly focus on the pharmacological effects on the AML cell populations whereas pharmacological effects on the AML-supporting stromal cells are not so well characterized, especially not in studies of the low-toxicity disease-stabilizing therapeutic alternatives [3¨C6]. Several clinical studies have described an AML-stabilizing effect of valproic acid (VPA) in combination with all-trans retinoic acid (ATRA) and eventually cytotoxic drugs (e.g., Ara-C) [6¨C14]. VPA is a short-chain fatty acid that has multiple anticancer actions including HDAC inhibitory activity and can affect AML cell proliferation [15, 16], whereby ATRA is a vitamin A derivative that mainly interferes with regulation of differentiation and apoptosis in AML [17, 18]. Previous
%U http://www.hindawi.com/journals/lrt/2014/143479/