Effects of endogenous and tobacco-related amines and nitrosamines on cell growth and morphology of a cell line derived from a human neuroendocrine lung cancer.

This report is part of a comprehensive research programme to elucidate the role of physiological functions and pathways of pulmonary neuroendocrine cells in the cascade of events that lead to the development of neuroendocrine lung cancer. In this study, a well differentiated neuroendocrine cell line (NCI-H727) derived from a human lung carcinoid was used to investigate the ability of endogenous and tobacco-related amines to stimulate cell proliferation in neuroendocrine tumour cells. Cell line NCI-H727 was exposed in vitro to the endogenous amine serotonin and its precursor 5-hydroxytryptophan (5-HTP), to the tobacco-related amine nicotine, and the tobacco-related nitrosamines N-nitrosodiethylamine (DEN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). The experiments were conducted in both 8% CO(2)-92% air and in 5% CO(2)-95% air. The effect on growth kinetics and ultrastructure of these conditions were studied. All amines had a dose-dependent stimulating effect on cell growth when tested in 8% CO(2)-92% air with nicotine exerting the strongest effect. No such effect was observed in 5% CO(2)-95% air and the control cells did not grow under these conditions. DEN, 5-HTP, serotonin and NNK all caused dedifferentiation of cytoplasmic organelles. Nicotine caused a change in size and ultrastructure of dense-cored granules suggestive of a change in the nature of stored neuroendocrine material.

Inhibition of N-diethylnitrosamine metabolism by human lung cancer cell lines with features of well differentiated pulmonary endocrine cells.

Cell lines derived from a human pulmonary carcinoid tumor (NCI-H727) and from a human pulmonary large cell carcinoma (NCI-H460) were investigated by transmission electron microscopy. Both cell lines, at early in vitro passage, demonstrated ultrastructural features of well differentiated pulmonary endocrine cells. Line NCI-H727 had more endoplasmic reticulum than line NCI-H460 and demonstrated L-dopa decarboxylase activity as well as production of calcitonin and bombesin. Because of their ultrastructural resemblance with normal pulmonary endocrine cells, these cell lines were used to test the theory derived from experiments in hamsters that human pulmonary endocrine cells can metabolize N-nitrosodiethylamine (DEN). The cells were incubated in vitro with [14C]DEN. Metabolism was assessed by 14CO2 production. Both cell lines metabolized DEN to a much greater extent than previously investigated human lung cancer cell lines of Clara cell and alveolar type II cell morphology. In keeping with its abundant endoplasmic reticulum, line NCI-H727 yielded 14CO2 in the 300 nM range, whereas NCI-H460 was less active. Metabolism was time dependent. Preincubation with various enzyme inhibitors yielded a highly significant inhibition of DEN metabolism with the two inhibitors of the fatty acid cyclooxygenase component of prostaglandin endoperoxide synthetase, aspirin and indomethacin. Inhibitors of cytochrome P-450 (CO, piperoxylbutoxide) did not inhibit DEN metabolism. Preincubation with sinigrin yielded similar negative results as CO and piperonylbutoxide. Our data are in support of the theory that human pulmonary endocrine cells can metabolize nitrosamines. Moreover, the experiments with enzyme inhibitors suggest that in this cell type such metabolism is largely dependent on prostaglandin endoperoxide synthetase.