Human neutrophil-mediated cytotoxicity to tumor cells

The role of human neutrophils as effector cells in host resistance to neoplasia was investigated. Neutrophil cytotoxicity was quantitated in an in vitro assay measuring release of [3H]thymidine from prelabeled human tumor cells. Neutrophils were consistently cytotoxic and cytostatic to the adherent tumor lines T24 (a transitional cell carcinoma of the bladder), LR (melanoma), and simian virus 40-transformed WI-38 VA 13 fibroblasts and to the nonadherent lymphoid tumor lines K562, Raji, and CEM. Maximum cytolysis and cytostasis occurred at 72 hours. Neutrophils were selectively cytotoxic for tumor cells and generally did not kill normal human fibroblasts. Selected protease inhibitors did not inhibit neutrophil cytotoxicity and neutrophil lysates were ineffective in killing tumor targets.