The role of the soluble p53 antigen and its autoantibodies as markers for 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 in humans. An HPLC technique was used to measure serum levels of both forms of p53 protein after their partial isolation on gel fiberglass affinity chromatography columns. Tumor-associated proteins (TAP) in the form of either antigens or autoantibodies were about 4% of the total protein 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 autoantibodies 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-associated antigens (TAA) and the amount of p53 antigen (r=0.69), total amount of IgG and the amount of p53 autoantibodies (r=0.46), and between both forms of p53 protein (r=0.46). A high coefficient of regression was 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 serum levels of p53 protein were weak: 0.33 and -0.32 for p53 antigen and its autoantibodies, respectively. Serum determination of p53 autoantibodies has no advantage over the determination of p53 antigen. Both forms of p53 protein can be isolated with extremely high accuracy for the pathological diagnosis of cancer (87-93%). Specificity of the method was proved using of commercial p53 PAb OD1: the GFG columns with this antibody were able to isolate the same proteins which were isolated by GFG columns with anti-p53 IgG. Moreover, the isolation of p53 protein was performed with higher effectiveness using the GFG columns with entrapped anti-p53 IgG than those columns with commercial DO1 PAb.