THE ROLE OF THE SOLUBLE P53 ANTIGEN AND ITS AUTOANTIBODIES AS MARKERSFOR DIAGNOSIS OF COLON-CANCER - A COMPARATIVE-STUDY

The role of various serological tumor markers, p53 soluble antigen and its autoantibodies, was evaluated for the detection of colon cancer i n humans. An HPLC technique was used to measure serum levels of both f orms of p53 protein after their partial isolation on gel fiberglass af finity chromatography columns. Tumor-associated proteins (TAP) in the form of either antigens or autoantibodies were about 4% of the total p rotein isolated from the serum of colon cancer patients. The absolute amount of each of the two types of TAP was also similar: 14.69+/-2.88 and 18.29+/-3.85 mg ml(-1), respectively. The amount of p53 autoantibo dies was higher than those of p53 antigen, but the difference was not significant: 9.35+/-3.48 and 6.19+/-3.87 mg/ml, respectively (p>0.05). A good correlation was found between the total amount of tumor-associ ated antigens (TAA) and the amount of p53 antigen (r=0.69), total amou nt of IgG and the amount of p53 autoantibodies (r=0.46), and between b oth forms of p53 protein (r=0.46). A high coefficient of regression wa s found between the total amount of TAA and the amount of p53 antigen (b=2.4). Relationships between Duke's stage in colon cancer and the se rum levels of p53 protein were weak: 0.33 and -0.32 for p53 antigen an d its autoantibodies, respectively. Serum determination of p53 autoant ibodies has no advantage over the determination of p53 antigen. Both f orms of p53 protein can be isolated with extremely high accuracy for t he pathological diagnosis of cancer (87-93%). Specificity of the metho d was proved using of commercial p53 PAb OD1: the GFG columns with thi s antibody were able to isolate the same proteins which were isolated by GFG columns with anti-p53 IgG. Moreover, the isolation of p53 prote in was performed with higher effectiveness using the GFG columns with entrapped anti-p53 IgG than those columns with commercial DO1 PAb.