title: Rapid killing of actinomycin D-treated tumor cells--cytotoxicity of cell-free monocyte supernatants.
abstract: Human monocytes kill Actinomycin D-treated WEHI 164 sarcoma cells in a 6 h 51Cr release assay (drug dependent cellular cytotoxicity, DDCC). In the present study we have investigated and characterized the human monocyte production of a cytotoxic factor which mediates DDCC. Cell-free supernatants obtained culturing monocytes for 4-5 h kill Actinomycin D-treated WEHI 164 cells but not untreated tumor cells. A series of antiproteases inhibits the cytotoxic activity of cell-free monocyte supernatants, whereas scavengers of reactive oxygen intermediates were ineffective. The lytic activity was destroyed treating supernatants at 100 degrees C for 5 min or by exposure to acid pH or to proteinase K, whereas it was unaffected by heating at 56 degrees C for 30 min. Upon gel filtration on Sephacryl S200, cytolytic activity eluted in the 33,000 molecular weight range.
mesh_terms: D002374:Catalase / Q000494:pharmacology; D002460:Cell Line; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D003609:Dactinomycin / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D009000:Monocytes / Q000166:cytology / Q000276:immunology*; D011480:Protease Inhibitors / Q000494:pharmacology; D012509:Sarcoma; D013482:Superoxide Dismutase / Q000494:pharmacology
chemical_list: D011480:Protease Inhibitors; D003609:Dactinomycin; D002374:Catalase; D013482:Superoxide Dismutase