Cloning and Expression of Human Uridine Phosphorylase

Using a mouse cDNA probe we have identified a human uridine phosphorylase cDNA clone from the cDNA library of a human colorectal tumor cell line, HCT116. The recombinant human uridine phosphorylase expressed in COS-7 cells demonstrated specific enzyme activity with uridine as the substrate; this activity was inhibited by the competitive inhibitor 2,2′-anhydro-5-ethyluridine. Northern blot analysis with the cDNA as a probe demonstrated high levels of mRNA expression in several tumor cell lines but very low level in normal cell, WI-38. The expression of uridine phosphorylase mRNA in HCT-116 cells was further enhanced by treating the cells with vitamin D3 and the inflammatory cytokines: tumor necrosis factor α, interleukin 1α and interferon γ.