POTENTIAL FALSE-POSITIVE RESULTS WITH ANTIGEN ENHANCEMENT FOR IMMUNOHISTOCHEMISTRY OF THE P53 GENE-PRODUCT IN COLORECTAL NEOPLASMS

Immunohistochemistry (IHC) for intranuclear p53 gene product is a simp le, routine alternative to molecular genetic analysis of the p53 gene, Several methods for antigen enhancement are currently in use for IHC. This study evaluates the effect of extreme antigen enhancement for p5 3, using a monoclonal antibody (DOT) and a polyclonal antibody (CM1), The cases studied were five colorectal carcinomas, two specimens of no rmal colorectal mucosa, and four colorectal carcinomas with genetic al terations which are expected to preclude p53 gene product expression, namely mutation to a STOP codon in the p53 gene detected by denaturing gradient gel electrophoresis with subsequent sequencing and allelic l oss of 17p in the region where p53 is located, detected by restriction fragment length polymorphism analysis, The findings suggest that extr eme antigen enhancement may cause false-positive results with a distin ct nuclear staining pattern when MAb DO7 is used as a primary antibody , It is concluded that all antigen enhancement methods should be thoro ughly tested to evaluate their validity and that there may be a limit to the extent to which antigen enhancement can be applied in IHC for p 53 protein.