Comparative anticancer effects of vaccination and dietary factors on experimentally-induced cancers.

The role of two major factors were analyzed in the prevention of experimentally-induced cancers: a) vaccination of animals with polyclonal IgG generated against the soluble p53 antigen and b) feeding of animals with diets rich with dietary fibers or fat. a) In vaccination, a few attempts have been made to utilize p53 protein as a tumor suppressor. IgG generated against the cytoplasmic, soluble p53 antigen from tumor-bearing rats prevents the carcinogenic effect of 1,2-dimethylhydrazine (DMH) decreasing significantly the number of tumor-bearing rats in vaccinated group compared with non vaccinated controls and preventing benign tumors from becoming malignant. The antitumor effect of vaccination is accompanied by a significant increase in the serum-level of p53 antigen in vaccinated rats compared with non vaccinated controls. The immune response of a host to vaccination activates the lymph components of the spleen, and this activation is manifested by the multiplication of the number of lymphocytes which are generated against specific antigens. This multiplication is achieved by the higher division of the antigen-specific lymphoblasts with their subsequent transformation into plasma cells. These cells synthesize the specific protein (IgG). One such protein is the tumor-associated p53 protein, which is synthesized by rats against rabbit anti-p53 IgG. b) The role of dietary factors in the prevention of chemically induced cancer was reviewed on two models: the role of high fiber diets in prevention of colon cancer, and the role of high fat diets in the prevention of mammary gland cancer. Experiments in colon cancer showed that 20% cellulose decreased significantly tumor incidence caused by DMH. The tumor-preventive effect of a cellulose diet was accompanied by increased enzyme concentrations, such as ornithine decarboxylase, thymidine kinase and beta-glucuronidase. This effect was accompanied by activation of some cellular mechanisms, i.e. apoptosis, proliferating cell nuclear antigen (PCNA) and p53 protein synthesis. Experiments in mammary glands cancer showed that a 15% olive-oil diet reduced significantly the tumor incidence caused by 9,10-dimethyl-1,2-benzanthracene. The antitumor effect of the olive-oil diet was connected to its content of monounsaturated fatty acids, such as oleic and palmitic acids. The promotive tumorigenic effects of other high-fat diets (avocado, soybeans) were associated with high content of some polyunsaturated fatty acids (linoleic and alpha-linolenic). Different diets have different targets. The effect of the same diet depends on its anti-tumor substances content.

CONCLUSIONS

Vaccination and some diets have similar mechanism in their tumor-preventive effects.