Immunohistochemical analysis of p53 protein overexpression in liver cell dysplasia and in hepatocellular carcinoma

We analysed p53 protein immunoreactivity in hepatocellular carcinomas (HCCs) and in liver cell dysplasia (LCD) of patients from an area in Northern China, using five anti-p53 protein antibodies recognizing different epitopes of the protein. In HCCs, the overall prevalence of p53 protein immunoreactivity was 78.3%. However, prevalence was strongly influenced by the type of antibody used, ranging from 67.5% for antibody PAb-1801 to only 10.8% for antibodies PAb-421 and DO-7. p53 protein immunoreactivity was not related to type or grade of HCC. In contrast to former reports, p53 protein staining was restricted to nuclei only when using the CM-1 antibody, whereas two other antibodies yielded both, nuclear and cytoplasmic or membrane staining, and no nuclear staining was observed with antibodies PAb-421 and DO-7, the latter two, however, demonstrating cytoplasmic and membrane staining. For LCD, three subtypes were morphologically and karyometrically defined. Nuclei of some LCD cells were p53 immunoreactive, but positivity was restricted to the small cell variant of LCD. Positivity was different for cirrhosis with or without associated HCC, amounting to 18.9% in the former and 39.4% in the latter. Interestingly, p53 protein immunoreactivity also occurred in a set of small hepatocytes not showing the typical features of LCD and therefore classified as simple regenerating liver cells.