Variations in immunohistochemical detection of p53 protein overexpression in cervical carcinomas with different antibodies and methods of detection

Immunocytochemical detection of p53 protein products in paraffin sections is possible with a number of antisera, monoclonal and polyclonal. Few corroborative results amongst different laboratories have been published due to variations in the antibodies, the fixation protocols, and the immunocytochemical methods applied. Antigen unmasking methods employing microwaves or proteolytic enzymes add to the disparity in the percentage of positive cases reported. In this study, paraffin sections of 55 cases of cervical carcinoma were immunostained with monoclonal antibodies p53-DO7 and p53-1801 (a) without section pretreatment, (b) with pronase digestion, and (c) with microwave antigen retrieval in citric acid buffer. Specimens fixed in buffered formalin required antigen unmasking to show positive staining. Pronase digestion caused false-negative immunostaining. Microwave pretreatment with p53-DO7 yielded 100 per cent positivity for p53 proteins but only 7/55 cases with more than 50 per cent positive cells. Monoclonal antibody p53-DO7 detected more positive cases than p53-1801. Immunostaining with antibodies to p53 proteins must be interpreted cautiously as variations in fixation, antibodies, and section pretreatment will significantly affect results.