CLONING AND EXPRESSION OF HUMAN URIDINE PHOSPHORYLASE

Using a mouse cDNA probe we have identified a human uridine phosphoryl ase 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 cel l lines but very low level in normal cell, WI-38. The expression of ur idine phosphorylase mRNA in HCT-116 cells was further enhanced by trea ting the cells with vitamin D3 and the inflammatory cytokines: tumor n ecrosis factor alpha, interleukin 1 alpha and interferon gamma. (C) 19 95 Academic Press, Inc.