Induction of Thymidine Kinase Activity and Clonal Growth of Certain Leukemic Cell Lines

Normal polymorphonuclear neutrophils (PMNs) constitutively secrete a mediator designated granulocyte-derived factor (GDF) that can enhance the uptake of 3H-thymidine (3to 20-fold) by the molt-3, CTV-1, and K562 leukemic cell lines in a dose-dependent manner. GDF is heat labile (56°C for 30 minutes) and acid labile (pH 2.0) and is sensitive to treatment with bacterial protease type IV. Our preliminary studies suggest that GDF is non-dialyzable (molecular weight cutoff, 12.000). binds to diethylaminoethyl (DEAE), and has an apparent molecular weight (mol wt) of about 40 Kd. Production of GDF is unaffected by treatment of PMN with activating agents (interferon gamma, OK432, phorbol ester, calcium ionophore, poly I:C) or metabolic inhibitors (actinomycin-D and cyclohexamide), suggesting that GDF is