IMMUNOHISTOCHEMICAL DETECTION OF P53 PROTEIN IN ARCHIVAL TISSUES FROMSQUAMOUS-CELL CARCINOMAS OF THE ORAL CAVITY USING WET AUTOCLAVE ANTIGEN RETRIEVAL

Using a panel of four anti-p53 antibodies (CM-1, PAb 1801, DO7, and PA b 240), the phenotypic characteristics of p53 protein overexpression w ere investigated in 22 routinely formalin-fixed and paraffin-embedded squamous cell carcinomas of the oral cavity. Conventional immunohistoc hemical staining without pretreatment for antigen retrieval was compar ed with wet autoclaving (AC) and microwave irradiation (MW). Applying AC or MW, p53 immunoreactivity was demonstrated in 9/22 cases with PAb 1801 and DO7 antibodies and in 8/22 cases with the CM-1 antibody. Imm unostaining with the PAb 240 antibody after AC pretreatment showed p53 positivity in 8/22 tumours, but in only 4/22 following MW pretreatmen t. Immunostaining without pretreatment revealed only 2/22 p53-positive cases using CM-1, 4/22 with PAb 1801, and 3/22 with DO7. Without pret reatment, the PAb 240 antibody was consistently negative. Wet autoclav e pretreatment was significantly superior for all the antibodies used in this study when compared with conventional immunohistochemistry wit hout pretreatment (P<0.005). It yielded better results than microwave irradiation for antigen unmasking in relation to the PAB 240 antibody (P<0.05). Wet autoclave pretreatment is recommended as a reliable and highly reproducible method for p53 antigen retrieval in routinely proc essed archival material. The advantages over microwave pretreatment in clude simple handling and good preservation of morphology.