The role of blood levels of soluble 53 kDa protein and CEA in monitoring colon cancer patients

Background: The usefulness of determining blood levels of the soluble p53 antigen and CEA was evaluated with respect to the monitoring colon cancer patients. Methods: HPLC (high performance liquid chromatography) was used to measure serum levels of the soluble 53 kDa protein (s53) after its partial isolation on gel fiberglass affinity chromatography columns. Results: The blood of cancer patients before tumor removal contained a high amount of s53 protein which did not change significantly over several subsequent months (4.5 and 4.7 mg/ml, respectively). The average serum level of CEA was relatively low but with extremely high deviations (48 ± 128 ng/ml). In patients with recurrent cancer and metastases, the serum concentrations of the s53 protein and CEA remained at high levels and their changes during the period studied were not significant (3.9 ± 3.5 and 6.1 ± 2.9 for s53; 56.5 ± 148.5 and 209.9 ± 867.3 for CEA). Disease progression was accompanied by slight increase in the serum levels of the s53 protein (3.5 ± 2.2 and 7.6 ± 4.6) or CEA (143.3 ± 98.5 and 244.9 ± 873.8). Despite the absence of statistically significant changes in the serum levels of the s53 protein in different groups of patients, on an individual basis such changes could be detected and could be of diagnostic value. Conlusions. Findings suggest that HPLC determinations of blood levels of the s53 protein can be a useful means of monitoring cancer patients only if tumor removal is complete and the patient exhibits a subsequent sharp decrease in the p53 protein serum level. In such cases, a following increase in the serum level of the p53 protein reflects the initiation of a new neoplastic formation which can then be detected a few months earlier than by any other available method. However, if the patient's immune system reacts weakly to the operation and the blood concentration of the s53 protein remains high, neither CEA nor s53 levels can be used for monitoring purposes.