Molecular basis for the regulation of hypoxia-inducible factor-1α levels by 2-deoxy-D-ribose

The angiogenic factor, platelet-derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP), stimulates the chemotaxis of endothelial cells and confers resistance to apoptosis induced by hypoxia. 2-Deoxy-D-ribose, a degradation product of thymidine generated by TP enzymatic activity, inhibits the upregulation of hypoxia-inducible factor (HIF) 1 alpha, BNIP3 and caspase-3 induced by hypoxia. In the present study, we investigated the molecular basis for the suppressive effect of 2-deoxy-D-ribose on the upregulation of HIF-1 alpha. 2-Deoxy-D-ribose enhanced the interaction of HIF-1 alpha and the von Hippel-Lindau (VHL) protein under hypoxic conditions. It did not affect the expression of HIF-1 alpha, prolyl hydroxylase (PHD) 1/2/3 and VHL mRNA under normoxic or hypoxic conditions, but enhanced the interaction of HIF-1 alpha and PHD2 under hypoxic conditions. 2-Deoxy-D-ribose also increased the amount of hydroxy-HIF-1 alpha in the presence of the proteasome inhibitor MG-132. The expression levels of TP are elevated in many types of malignant solid tumors and, thus, 2-deoxy-D-ribose generated by TP in these tumors may play an important role in tumor progression by preventing hypoxia-induced apoptosis.