The role of the cytoplasmic fraction of p53 protein in the detection and prevention of colon cancer was analyzed by comparing results of the author's studies with data published in the literature. In cancer detection, although immunochemical methods are widely used for diagnostic purposes positive results are not always obtained. Using a new modification of affinity chromatography columns, we isolated the cytoplasmic, soluble form of tumor-associated antigens (TAA) from the serum of colon cancer patients. p53 protein was found to be one of the main components of such TAA. The serum level of p53 antigen was related to tumorigenicity: the correlation and regression coefficients between the serum level of p53 protein and the progress in colon cancer were 0.48 and 0.88, respectively, p<0.01. Thus HPLC-determination of the serum concentration of this protein could serve as a screening tool for cancer detection. The sensitivity and specificity of the method reached 92% and its accuracy was 88%. The method can be used to detect cancer development either as a primary disease or as a recurrent disorder. In cancer prevention, a few attempts have been made to utilize p53 protein as a tumor suppressor. IgG generated against the cytoplasmic p53 antigen from tumor-bearing rats prevents the carcinogenic effect of 1,2-dimethylhydrazine decreasing significantly the number of tumor-bearing rats in vaccinated group compared with non-vaccinated controls. Anti-p53 IgG not only had an antitumor effect but also prevents benign tumors from becoming malignant: the number of malignant tumors in vaccinated rats was half that in controls (29% and 58%, respectively). The antitumor effect of vaccination is accompanied with a significant increase in the serum-level of p53 antigen in vaccinated rats compared with non-vaccinated controls. p53 protein plays an important role in colon cancer: the unique mechanism involved in both cancer development and in cancer prevention appears to include high production of this protein.

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