Methods in pathology. p53 expression in formalin-fixed, paraffin-embedded archival specimens of intrahepatic cholangiocarcinoma: retrieval of p53 antigenicity by microwave oven heating of tissue sections.

Immunohistochemical demonstration of p53 is thought to reflect mutations of the p53 gene. Although p53 expression or mutation has been investigated in a variety of carcinomas, it has not been examined in intrahepatic cholangiocarcinoma (CC). We investigated expression of p53 in formalin-fixed, paraffin-embedded archival specimens of 40 CCs (22 autopsy cases and 18 surgical cases) by immunohistochemistry using four antibodies (PAb1801, DO-7, BP53-12, CM1). We also attempted to enhance p53 expression by pretreatments of tissue sections by pepsin digestion as well as by microwave oven heating. Formalin-fixed, paraffin-embedded archival surgical specimens of 15 colon carcinomas were used as controls. In surgical cases, p53 expression was abolished by pepsin predigestion, although it was greatly enhanced by pretreatment of microwave oven heating in all immunostainings (PAb1801, DO-7, BP53-12, CM1). In surgical cases immunostained with microwave oven heating, DO-7, BP53-12, and CM1 showed frequent p53 expression (22% in CC; 60-67% in colon carcinoma), whereas PAb1801 showed low p53 expression (0% in CC; 13% in colon carcinoma). In contrast to the surgical cases, all 22 CCs of autopsy cases showed no p53 expression by any antibodies as well as by any pretreatments. These results shows that a pretreatment of tissue sections by microwave oven heating is a very good method for demonstrating p53 protein in formalin-fixed, paraffin-embedded archival materials and that DO-7, BP53-12, and CM1 are useful antibodies for detection of p53 in formalin-fixed, paraffin-embedded archival materials. No expression of p53 in autopsy cases of CC suggests that p53 antigenicity is lost during autopsy procedure.(ABSTRACT TRUNCATED AT 250 WORDS)