TUMOR-SUPPRESSOR EFFECTS OF ANTI-P53 IGG ON CHEMICALLY-INDUCED COLON-CANCER IN RATS

Background - We have shown the suppressive effects of rabbit IgG raise d against p53 tumor-associated antigen an chemically induced colon can cer in rats. Methods - Rabbit anti-p53 IgG was raised against the p53 antigen isolated in the form of soluble protein from the serum of colo n tumor-bearing rats, The induction of colon cancer was achieved by we ekly injections of 1,2-dimethylhydrazine (20 mg/kg) for 7 weeks to Spr ague Dawley rats, Vaccination of rats started 2 weeks after the end of cancer induction and was performed by 4 subcutaneous injections of Ig G (100 mu g/rat) at two-week intervals, The results were evaluated 6 m onths after the start of cancer induction. Results - Vaccination of ra ts with anti-p53 protein showed clear tumor-suppressor effects, The nu mber of tumor-bearing rats in the vaccinated group decreased to 80% co mpared with 100% in the control group The number of malignant tumors i n vaccinated rats was half that in controls: 52% and 100%, respectivel y. The number of rats with metastases decreased from 10% in controls t o 5% in the vaccinated group, The antitumor effect of vaccination was accompanied by a non significant increase in the serum level of p53 an tigen in vaccinated rats compared with non vaccinated controls. Conclu sions - We suggest that the anticancer role of a vaccine generated aga inst p53 protein from benign tumor-bearing rats is related to a wild-t ype p53 protein, Further studies will be performed to confirm this hyp othesis.