EFFECT OF MICROWAVE-OVEN HEATING TIMES ON ANDROGEN RECEPTOR ANTIGEN RETRIEVAL FROM PARAFFIN-EMBEDDED PROSTATIC ADENOCARCINOMA

The aim of this study was to investigate the effect of microwave oven heating for antigen retrieval on the immunoreactivity of human prostat e carcinoma androgen receptor (AR) in tissue sections. Formalin-fixed, paraffin-embedded tissue sections were microwaved at 5-min intervals for a total of 15, 20, 25, 30, 35 minutes at maximum power (700W). The monoclonal antibody E39.4.1 directed against human AR was used at a 1 :10 dilution. Without microwave oven heating, prostatic tissue did not exhibit any AR immunoreactivity. Moderate positivity appeared after t hree 5-minute cycles of microwave heating. The intensity of immunoreac tivity improved progressively with heating times of 20 and 25 min up t o an optimum time of 30 minutes, when nuclear staining was most intens e with, the absence of background staining and without loss of morphol ogical details. While antigen retrieval is effective in restoring anti genicity in a variety of setting, the length of time prostate tissue i s exposed to microwave radiation is critical in order to obtain optima l AR immunostaining. AR immunostaining reliably permitted evaluation o f the distribution. and intensity of positively stained nuclei and the distinction of the various cell types in archival material.