Tumor-Inhibitory Antibiotic Uptake Facilitated by Leukoregulin: A New Approach to Drug Delivery'

otics by human K562 erythroleukemia cells was examined in the presence of leukoregulin to determine if the lym-phokine's ability to increase the plasma membrane permeability of tumor cells facilitates concurrent entry of pharma-cologically active molecules. K562 cells were exposed to 0.25-2.0 /xg of doxoru-bicin/mL for up to 60 minutes at 37°C. Commencing within 15 minutes, leuko-regulin increased the entry of dox-orubicin approximately twofold and the uptake of mitomycin, mithramycin, and propidium iodide twofold to ten-fold. This finding indicates the poten