Uridine kinase activities in normal and neoplastic lymphoid cells.

Both adult (I) and embryonic (II) forms of uridine kinase have been identified in the transplantable EL-4 leukemia of C57BL/6 mice and in the P815Y mastocytoma of DBA/2 mice. Only Species I is found in primary tumor cells of lymphoid orgin (virus-induced feline lymphosarcoma, human acute and chronic lymphocytic leukemia) and in normal calf thymocytes and porcine peripheral blood lymphocytes; Species I was induced 4-fold upon stimulation of the normal blood lymphocytes with phytohemagglutinin. The level of uridine kinase activity in the feline lymphosarcoma of thymus-dependent lymphocyte orgin and childhood lymphocytic leukemia of possible thymus-dependent lymphocyte or null-cell origin was similar to the induced level in phytohemagglutinin-stimulated normal lymphocytes, i.e., thymus-dependent lymphocytes. In contrast lymphocytes of a patient with chronic lymphocytic leukemia of thymus-independent lymphocyte origin had a level of uridine kinase activity comparable to that of the unstimulated normal lymphocytes or thymocytes. The uridine kinase activity in the EL-4 tumor cells was repressed by acute treatment of the mice with 5-azacytidine.