IGG GENERATED AGAINST BENIGN TUMOR-ASSOCIATED ANTIGENS PREVENTED THE EFFECTS OF 1,2-DIMETHYLHYDRAZINE IN RATS

We showed the possibility of significant decreasing of the frequency o f chemically induced colon cancer in rats by vaccination with polyclon al rabbit IgG generated against purified tumor-associated antigens (TA A). TAA were isolated from benign rat colon tumors by the method devel oped in our laboratory (Zusman et al 1994) using affinity chromatograp hy columns with gel fiberglass membranes (R. Zusman, 1992) containing anti-tumor IgG. The IgG was isolated from rabbits following their vacc ination with TAA. Sprague Dawley rats were vaccinated with anti-TAA Ig G (100 mu g/rat) suspended in Freunds adjuvant by weekly subcutaneous injections for 5 weeks. The induction of colon cancer was caused by we ekly injections with 1,2-dimethylhydrazine (DMH) (20 mg/kg) for 7 week s and was started one week after the end of the vaccination. The resul ts of experiments were evaluated 6 months after the start of cancer in duction. IgG protected against the carcinogenic effects of DMH. The nu mber of tumor-bearing rats decreased to 64% as compared with 90% in th e control group. In vaccinated rats, the incidence of tumors was almos t 3 times less than of control, i.e. 3.6 and 9.3, respectively. The nu mber of malignant tumors was also significantly smaller in vaccinated rats than in controls, being 24% and 58%, respectively. Metastases wer e found only in controls, 4 of 30 rats. The results of our experiments have shown that anti-TAA IgG not only has anti-tumor effects but also prevents the malignization of benign tumors. As one of the main compo nents of TAA which was isolated from colon cancer rats was soluble p53 antigen (Zusman et al 1994), we suggest that the vaccine which has be en generated in our experiments may be regarded as acting mainly again st p53 antigen, and its antitumor effects should also be considered as effects of p53 antibodies. The further studies will be preformed to c larify this.