A MICROWAVE METHOD THAT ENHANCES DETECTION OF ABERRANT P53 EXPRESSIONIN FORMALIN-FIXED, PARAFFIN-EMBEDDED TISSUES

Objective.-Detection of aberrantly accumulated p53 protein by immunohi stochemistry may have prognostic significance in many human neoplasms. We wished to identify a technique applicable to formalin-fixed, paraf fin-embedded sections that would reliably yield results equivalent to frozen-section immunohistochemistry. Design.-We compared the frequency of p53 immunostaining obtained by applying monoclonal antibodies PAb1 801, DO7, or DO1, a 1:1 PAb1801-DO7 cocktail, and a 1:1 PAb1801-DO1 co cktail to fresh-frozen and formalin-fixed, paraffin-embedded tissues f rom 36 lung and upper aerodigestive-tract carcinomas. With the formali n-fixed tissues, we compared pepsin predigestion with microwave irradi ation in citrate buffer as means of enhancing the sensitivity of p53 d etection. Setting and Patients.-All tissues were obtained from surgica l resections of tumors, from patients who underwent surgery at the Min neapolis Department of Veterans Affairs Medical Center between 1990 an d 1992. Main Outcome Measures.-The sensitivity of different paraffin s ection techniques for immunohistochemical detection of accumulated p53 protein was determined in reference to the optimal frozen section met hod (defined as the method that yielded the greatest number of p53-pos itive cases in frozen tissue). Results.-Microwave antigen retrieval ma rkedly enhanced staining with PAb1801 and DO7 in paraffin sections, as compared with pepsin predigestion and no pretreatment. This technique was 100% sensitive relative to the optimal frozen tissue method. In c ontrast, staining with DO1 alone was not enhanced by microwaving. Conc lusions.-Microwave pretreatment in conjunction with the use of either PAb1801 or DO7 is highly efficacious in the immunohistochemical detect ion of aberrant p53 expression in formalin-fixed, paraffin-embedded ti ssues.