Antibodies to the p53 tumor suppressor gene product quantified in cancer patient serum with a time-resolved immunofluorometric technique.

We have developed new methodology for quantifying antibodies to the p53 tumor suppressor gene product in human serum. The assay involves solid-phase immobilization of a monoclonal anti-p53-specific antibody that is then reacted with a tumor cell line lysate containing mutant p53. The immunopurified p53 antigen acts as an immunosorbent for the serum p53 antibodies that are then detected by reaction with a goat anti-human immunoglobulin G antibody labeled with alkaline phosphatase (ALP). ALP activity is then measured with enzymatically amplified time-resolved fluorometry. The developed assay has many advantages over the radioactively labeled techniques previously used. In a preliminary clinical study involving 790 patient sera, we have identified 16 positive samples (2%). Highest titers were observed in a patient with melanoma and two breast cancer patients. Further studies are needed to improve the sensitivity of this test and to evaluate its possible use for cancer diagnosis, prognosis or monitoring of therapy.