Effect of dietary vitamin A or N-acetylcysteine on ethylnitrosourea-induced rat gliomas.

It is our hypothesis that low grade gliomas are the glial counterparts of other precancerous lesions such as colon polyps and, therefore, suitable targets for chemoprevention. Steps in the molecular progression of gliomas have been described, indicating that an accumulation of abnormalities is required for progression to a high grade and interruption of this progression might be possible. An animal model of chemical glial carcinogenesis was used to test this hypothesis. Pregnant rats were injected intravenously with ENU (ethylnitrosourea) on the 18th day of gestation to induce gliomas in the offspring, which were randomized to receive control diet, diet supplemented with vitamin A palmitate, or diet supplemented with N-acetylcysteine. Animals exposed to ENU and receiving a control diet developed brain tumors and had a shortened life expectancy compared with rats unexposed to ENU. The animals treated with NAC showed no statistically significant delay in the time to tumor and no change in the histologic grade of the tumors when compared with animals receiving control diet, but the time to death from any cause of NAC treated animals differed significantly from untreated animals. Animals receiving high dose VA had statistically significantly prolonged time to tumor, survived significantly longer than untreated animals, but had no reduction in the total number of tumors or change in the histologic grade of their tumors. The theoretical basis of these results is likely due to the putative mechanism of action of these agents. These data indicate that glioma chemoprevention is possible and deserves further exploration.