[Effects of beta-carotene on lung cancer]

Beta-carotene at concentration of 6.25 micrograms/ml was shown to inhibit significantly the colony forming efficiency (CFE) of cultured human lung cancer 801 cell line and at 12.5 micrograms/ml was shown to completely inhibit CFE. A 42%-68% (P < 0.01) decrease in spontaneous lung metastasis of LA795 murine pulmonary adenocarcinoma was observed when T739 inbred strain mice were fed a diet with beta-carotene (25mg/100g diet). Ability of DNA and RNA synthesis of lung cancer cells were decreased (P < 0.05) after treating with beta-carotene (25 micrograms/ml) by 24 hours, but the ability for DNA synthesis of human lymphocytes was not effected by the same treatment. Expression of ras oncogene was proved to be inhibited by beta-carotene because the product of ras p21 proteins of cancer cells was decreased after treating by beta-carotene.