Protection of hamster lung cultures by L-cysteine or vitamin C against carcinogenic effects of fresh smoke from tobacco or marihuana cigarettes.

Sequential morphological and cytochemical effects of L-cysteine and vitamin C were assessed on hamster lung cultures exposed to smoke from either tobacco or marihuana cigarettes. Hamster lung cultures, when grown in normal media (Eagle-Dulbecco) without L-cysteine (NM), and exposed to fresh smoke from either tobacco or marihuana cigarettes for 1-8 weeks, displayed cytotoxic alterations, loss of lysosomes, and marked abnormalities of cell division and of DNA content of chromosomes, while cultures exposed in the same manner and grown in the same NM, but to which L-cysteine was added, showed increase of lysosomes and significantly less abnormalities in cell division and DNA content of chromosomes (P<0·005). Cultures grown in NM and exposed for 9-24 weeks to smoke (whole smoke or gas vapour phase) disclosed more and more rapid irregular growth of fibroblasts and/or malignant transformation, while cultures grown in NM with L-cysteine and exposed in the same manner to smoke resembled closely those of non-exposed controls. Non-exposed control cultures grown in NM did not show significant differences from those grown in NM+L-cysteine, except that controls with L-cysteine also showed increase of lysosomes, accompanied by a reduced growth rate. Addition of vitamin C to NM had a similar effect on growth of control and smoke exposed cultures as L-cysteine, but the cultures were less regular and grew more rapidly than with L-cystene. There was also occurrence of multinucleated giant cells. Cultures grown in NM which had undergone malignant transformation continued their abnormal growth during the examined period (over 2 years). However, when such transformed cultures were grown for 3 months or longer in NM with L-cysteine or vitamin C, the growth became more and more normal, and the cultures resembled closely those of non-exposed controls. These results suggest that, in hamster lung cultures, addition of L-cysteine or vitamin C to media protects against or reverses abnormal growth and malignant transformation occurring either in aged controls (1-2 years old) or in young cultures (3-6 months old) after repeated exposure to smoke from tobacco or marihuana cigarettes. The increase of lysosomes after L-cysteine or vitamin C also points to the possible importance of lysosomes in protecting the cultures against the enhancement of carcinogenesis by smoke.