Plasma purine nucleoside phosphorylase in cancer patients

Background: Purine nucleoside phosphorylase (PNP) is the purine salvage enzyme that converts guanosine to guanine and inosine to hypoxanthine. Methods: 279 samples from patients with differing cancers were collected during treatment at both pre- and post-dose stages for plasma PNP activity and compared with a normal population. Results: Normal plasma PNP activity was found to be 3.2 +/- 1.4 U/l (n = 55) as compared with the cancer patients (pre-dose 12.3 +/- 7.4 U/l [n = 215] and post-dose 11.2 +/- 5.9 U/l [n = 64]). Levels of plasma PNP did not differ greatly between the different cancer types but were on average four times greater than that found in the reference population. (C) 2004 Elsevier B.V. All rights reserved.