The effects of naturally occurring metabolites (L-cysteine, vitamin C) on cultured human cells exposed to smoke of tobacco or marijuana cigarettes.

The effects of vitamin C on the growth of human lung cultures and of vitamin C or L-cysteine on a human breast cancer culture (SK-Br-3) were assessed with and without exposure to fresh smoke from tobacco or marijuana cigarettes. When grown in the presence of vitamin C, lung cultures exposed or not exposed to either type of smoke showed a stimulation of growth and a significant decrease in mitotic abnormalities. However, abnormalities were much more marked in marijuana-exposed cultures than in tobacco-smoke-exposed ones. Nonexposed or tobacco-smoke-exposed breast cancer cultures, when grown in the presence of vitamin C, also showed acceleration of growth of epithelial cells, significant reduction in mitotic abnormalities, and occurrence of pseudoglandular structures, indicating differentiation. These alterations not only disappeared, but the cultures also became fibroblastic when they were returned to media without vitamin C. In contrast, vitamin C did not reduce mitotic abnormalities in marijuana-smoke-exposed breast cancer cultures, but stimulated abnormal growth and dedifferentiation. In nonexposed, tobacco-, or marijuana-smoke-exposed breast cancer cultures. L-cysteine evoked an acceleration of fibroblastic growth, which was not altered when the cultures were returned to media without L-cysteine.