Activation of ion channels in tumor cells by leukoregulin, a cytostatic lymphokine.

We used the whole-cell patch-clamp recording technique to study the effects of leukoregulin (LR), a cytostatic lymphokine produced by activated human peripheral blood lymphocytes, on the electrical properties of K562 tumor cells. LR induced changes in the membrane excitability in 33 of 55 cells studied. A minute or more after application, LR elicited a complex and reversible electrical response. The response lasted for several more minutes in the continued presence of LR. It consisted of (a) moderate-conductance (50 pS), cation-selective, ion-channel activity, (b) a shift of the zero-current membrane potential close to 0 mV, and (c) a suppression of a depolarization-activated K+ conductance. All of these changes in tumor cell excitability act coordinately to depolarize the tumor cells and may be important in the cytostatic actions of LR.