Gastric epithelial dysplasia.
Authors: F Farinati, M Rugge, F Valiante, R Baffa, F Di Mario, R Naccarato
Journal: Gut (1991)

Molecular abnormalities of the p.53 gene in chromosome 1 7p may be among the most commonly observed in human cancer. Their role in gastric carcinogenesis is suggested by their frequent detection in invasive adenocarcinomas. To investigate the chronology with which these abnormalities appear in the gastric carcinogenesis process, the expression of p53 proteins was investigated in late stages of the process, namely dysplasia, and in superficial carcinomas. A polyclonal antibody, CM-i, against both wild-type and mutant proteins was applied to paraffinembedded biopsy and gastrectomy specimens previously fixed in buffered formalin. Positive nuclear stain was obtained in 36.4% of 33 cases of gastric epithelial dysplasia, corresponding to 19% of mild, 27.3% of moderate, and 64.3% of severe dysplasias. Eight of 13 (61.5%) invasive carcinomas showed positive stain. The data indicate an increased incidence of p53 abnormalities in the late stages of gastric carcinogenesis. Introduction Deletions and insertions in the short arm of chromosome 1 7 as well as point mutations of the p53 gene have been reported frequently in human tumors, especially in the lung, breast, stomach, and colon (1-7). The nuclear proteins encoded by the p53 gene are suspected to play a regulatory role in the cell cycle. The normal protein has a short half-life, which makes it invisible in normal tissues by the usual immunohistochemical stains. Overexpression of the wild-type protein may occur abnormally in certain tumors (8). The proteins expressed by mutant p53 genes are more stable and more easily detected by immunochemical methods (9-11). Polycbonal antibody (CM-i) has been developed to detect both wild-type and Received 4/22/92. 1 Performed under the auspices of the R. Farini Foundation for Gastroenterological Research and NIH Grant P01-dA28842. 2 To whom requests for reprints should be addressed, at Department of Pathology, Louisiana State University Medical Center, 1901 Perdido Street, New Orleans, LA 70112. mutant p53 proteins utilizing pure soluble recombinant human p53. The CM-i antibody is able to detect protein in archived formalin-fixed and paraffin-embedded human tissues (12). Positivity of p53 protein by immunochemical methods has been reported in invasive gastric carcinomas and has been correlated with prognosis (13). Our interest has been in the precancerous gastric process, characterized by steps identifiable in tissue sections stained with hematoxylin and eosin. These steps involve atrophy, intestinal metaplasia, and dysplasia of the gastric mucosa (14). Archival material displaying several degrees of dysplasia as well as (predominantly superficial) invasive carcinomas was stained with CM-i polyclonal antibody to p53 proteins in order to investigate the timing of the abnormal expression of p53 proteins. Materials and Methods From a series of Italian patients enrolled in a prospective study of GED,3 24 subjects with a histological diagnosis of GED were selected. Each patient underwent multiple biopsies according to a protocol described in a previous study (15). In two of these patients, a gastrectomy was also performed because of the occurrence of GC. In addition, 9 cases of GED detected in stomachs resected for gastric cancer (8 cases) or for severe dysplasia (1 case) were also studied with extensive sampling of dysplastic and carcinomatous areas. All gastric biopsies as well as the surgical specimens were immediately fixed in buffered formalin (12 h for biopsy specimens, 24 h for resected stomachs). Fivetm-thick sections were stained with hematoxylin and eosin. Serial sections were used in the immunohistochemistry study. They were dewaxed in xylene (twice for 5 mm each) and rehydrated through serial alcohols (i00%, 95%; two changes of 3 mm each) to distilled water (twice for 5 mm each). Polyclonal antibody against both wild-type and mutant p53 protein (CM-i; Signet Laboratories, Inc., MA) (12) were used at a working concentration of 1 :25 at room temperature for 20 mm. Hydrogen peroxide, normal goat blocking serum, biotinylated immunoglobulins, avidin-biotin complex, and 3-amino-9-ethylcarbazole substrate solution were used according to the instruction from a commercial kit (Signet ELITE avidin-biotin detection system; Signet Laboratories, Inc.). Sections received a light Mayer’s hematoxylin counterstain, were mounted with aqueous mounting medium (Crystal/Mount; Biomeda, CA), and were postmounted with Postmounting Crystal/Mount in Permount (Biomeda). Positive control sections from for3 The abbreviations used are: GED, gastric epithelial dysplasia; Gd, gastric carcinoma. American Association for Cancer Research Copyright © 1992 on July 9, 2011 cebp.aacrjournals.org Downloaded from