Purine pathway enzymes in the circulating malignant cells of patients with cutaneous T‐cell lymphoma

Abstract

Activities of 3 purine pathway enzymes, adenosine deaminase (ADA), 5''-nucleotidase (5''N) and purine nucleoside phosphorylase (PNP), were examined in the circulating malignant cells (Sezary cells) of 8 patients with cutaneous T-cell lymphoma (CTCL). Cell lines derived from 2 other patients with CTCL were also studied. These were compared with enzyme activities in peripheral blood T-lymphocytes from 11 normal donors an 6 samples of human thymocytes. ADA activities were similar in the Sezary cells and peripheral blood T-cells (medians 7 and 15 U, P = 0.14), and both of these groups demonstrated significantly lower activity than did the thymocytes (median 100 U, P = 0.002). 5 N activity in the Sezary cells was also similar to that of the T-lymphocytes (median 0.022 and 0.030 U, P > 0.05), and both of these groups had significantly greater activity than did the thymocytes (median 0.002 U, P = 0.001). Median PNP activity in the Sezary cell population was also comparable to that measured in normal T-cells. There is a characteristic purine pathway enzyme pattern in Sezary cells that is similar to that seen in normal T-lymphocytes. This pattern is clearly distinguishable from that of thymocytes and from that previously described in lymphoblasts from patients with T-cell acute lymphoblastic leukemia. Apparently, Sezary cells are well-differentiated with respect to the T-cell axis. Quantitation of purine pathway enzymes may be useful in defining subsets of T-cell malignancy.