Natural killer (NK)-resistant human lung cancer cells are lysed by recombinant interleukin-2-activated NK cells

Natural killer (NK) cells are active in host defence against tumors. In order to determine if NK cells have the capacity to lyse human lung cancer cells, we evaluated blood NK cell activity against human lung carcinoma lines representing each of the commonest histological types of lung cancer, NCI-H157 (large cell), LICM107 and NCI-H146 (small cell), NCI-H226 (squamous cell), and LICM26 (adeno), and compared the results to their activity against a standard NK-sensitive target, K562, using a 16-hr 51Cr-release assay. At effector to target (E:T) ratios up to 50:1, NK activity was very low against each of the lung cancer cell lines compared to the K562 cells (NCI-H157 10 +/- 2%, LICM107 12 +/- 2%, NCI-H146 14 +/- 5%, NCI-H226 8 +/- 5%, and LICM26 7 +/- 3%, compared to K562 60 +/- 3%, P less than 0.001, for each compared to K562 cells). Recombinant interleukin 2 (IL-2) produced a dose-dependent augmentation of NK activity against each of the lung cancer cell lines, with doses as low as 0.25 U/ml being effective. The highest level of boosting was seen against NCI-H157 cells where NK activity (E:T, 50:1, IL-2, 250 U/ml) increased from 9 +/- 2 to 56 +/- 7%, P less than 0.001). Only brief exposure to IL-2 was necessary for augmentation to occur, with as little as 5 min being required for activation, although increased exposure times produced increased levels of augmentation. NK cells appeared to be the IL-2-responsive lytic cell population in these experiments as Leu 11b-depleted lymphocytes expressed little IL-2-mediated augmentation of activity against these target cells, and most of this IL-2-mediated augmentation of activity was located in the large granular lymphocyte-enriched fraction of the lymphocyte population. We conclude that normal blood NK cell activity against human lung cancer cell lines is low but that this activity can be markedly augmented by brief exposure of NK cells to low doses of recombinant IL-2, suggesting a potential role for IL-2 in the immunotherapy of human lung cancer.