The incidence of
brain tumor and other types of
cancer are markedly increased during the last few decades. There are many etiological and environmental factors involved in the initiation of different types of
cancers including
brain tumors. Mutations in tumor suppressor gene p53 and its expression are associated with shorter survival and higher mortality rate of patients with
brain tumors. Another factor, N-
nitrosamines have received much attention as a potential risk factor for
brain tumor. These compounds are potent
carcinogens and occur widely in the environment, and also can be formed endogenously in the stomach from the interaction of ingested
nitrate or
nitrite with secondary
amines.
Free radicals are another etiological factor of
brain tumor and are removed by cellular
antioxidants in the human body. Brain tissue is vulnerable to the damaging effects of
free radicals as a result of low
antioxidant levels. Interestingly, there is an inverse correlation between the total
antioxidant levels and oxidative DNA damage in
transitional meningioma compared with normal brain tissues. Also, an inverse relationship between
antioxidant levels and grades of
malignancy has been found after histopathological examination of
brain tumors. Moreover, high intake of
vitamin E is correlated with greater survival for all patients diagnosed as Grade III
malignant glioma. Dietary supplementation with
antioxidants [e.g.
vitamins C & E] was found to reduce the incidence of
brain tumors in children whose mothers took these
vitamins throughout pregnancy. On the other hand, decreases in
antioxidant levels were correlated with the severity of
malignancy of
brain tumors, and also with accumulation of considerable amounts of oxidative stress products including
free radicals which damage this tissue. The mechanisms of protection of these
antioxidants against
brain tumors might be due to inhibition of the nitrosation process, decreasing of
tumor necrotic factor, scavenging of
free radicals, inhibition of
telomerase activity which facilitates telomere attrition. It is concluded that administration of
antioxidants could reduce the incidence of
brain tumors and probably other types of
cancer.