Natural killer cytotoxic factor induction by K562 cells in patients with advanced cancer: correlation with production of interferon.

Advanced cancer patients were studied for their ability to produce natural killer cytotoxic factor (NKCF). Of 23 patients with advanced epithelial cancers, 8 showed deficient natural killer (NK) activity, as measured in a standard 51Cr release assay. Lymphocytes from these patients did not generate NKCF (nonproducers) in the presence of K562 cells. In addition, 7 other patients whose NK activity was in the normal range did not generate NKCF. Thus the deficiency in NKCF production was only partially correlated with the level of NK activity. Supernatants generated for NKCF were also assayed for antiviral activity. Mean interferon (IFN) titer of supernatants generated from peripheral blood lymphocytes (PBL) of cancer patients was significantly lower than that of supernatants generated by PBL from normal donors. Supernatants from 10 of 15 NKCF nonproducers contained no detectable IFN, whereas the remaining 5 contained up to 100 U IFN. NKCF was never generated in the absence of IFN. The defect in NKCF production by PBL from cancer patients could be corrected by the incubation of effector cells with exogenous IFN-alpha or IFN-alpha inducers, such as other tumor cells or viruses. The relationship among NKCF, IFN, and NK activities is discussed.