IMMUNOHISTOCHEMICAL DEMONSTRATION OF THE P53 TUMOR-SUPPRESSOR GENE-PRODUCT IN CANCER OF THE PANCREAS AND CHRONIC-PANCREATITIS

The p53 tumour suppressor gene and its protein products after point mu tations are currently attracting wide attention in the investigation o f human tumours. In this study we present the findings on percutaneous pancreatic biopsies of 82 cases after routine processing and immunost aining for the polyclonal p53 antibody CM1, an antibody directed again st both wild and mutant forms of p53 protein. There were 51 carcinomas , 5 islet cell tumours, 16 cases of chronic pancreatitis (including on e with atypical ductal epithelium) and seven histologically normal pan creatic biopsy specimens. None of the seven normal cases showed any de finite nuclear immunostaining for p53. Thirty-two (63%) of the pancrea tic adenocarcinomas showed moderate to intense immunoreactivity. Of th e 16 cases of chronic pancreatitis, 11 were negative and three showed equivocal immunostaining. The one case with ductal epithelial atypia s howed mild to moderate immunoreactivity. All islet cell tumours were n egative. The expression of the p53 gene, therefore, appears increased in the majority of pancreatic adenocarcinomas while this is not observ ed in chronic pancreatitis or normal pancreatic tissue. Nuclear immuno reactivity for p53 protein may represent mutant forms because of the s hort half-life of the wild-type protein. The lack of p53 expression in some cases of pancreatic adenocarcinoma may be due to different types of mutant proteins not detectable by the CM1 antibody. Nuclear immuno reactivity to the p53 protein in pancreatic biopsy is more suggestive of a malignant tumour than chronic pancreatitis.