EXPRESSION OF P53 ANTIGEN IN INFLAMED AND REGENERATED MUCOSA IN ULCERATIVE-COLITIS AND CROHNS-DISEASE

Physiologic overexpression of p53 protein may occur in the G1 stage of the cell cycle to slow down the cell cycle and allow DNA repair in st ressed or injured cells. We questioned whether there is increased expr ession of p53 protein in acutely inflamed mucosa (AI) and regenerated mucosa (RM) in ulcerative colitis (UC) and Crohn's disease (CD). Forma lin-fixed paraffin-embedded sections of resected bowels from eight pat ients with UC and 20 with CD were reviewed, and blocks were selected h aving areas defined as follows: AI = two high-power fields (HPFs) at t he edge of an ulcer, or one HPF with an inflamed crypt in the center; RM = branched or irregular glands with only mild chronic inflammation. Blocks with normal mucosa were available in 20 cases. One case of CD also had dysplasia, adenoma, and invasive carcinoma. p53 was identifie d with PAb1801 antibody using a labeled avidin-biotin immunoperoxidase technique. In each defined area, the positive nuclei were counted and expressed as the number of positive nuclei per 10 HPFs. Data were ana lyzed statistically for comparisons within and between the diseases. I n normal mucosa, only rare cells expressed p53 in two cases of CD. The mean frequency of positive nuclei was 2.24/10 HPFs in AT and 0.30/10 HPFs in RM in CD, and 7.63/10 HPFs in AT and 1.14/10 HPFs in RM in UC. Differences between the means for AI and RM were statistically signif icant in both UC and CD. Although not significant, the frequency of po sitive staining in both AT and RM was greater in UC as compared with C D. The results show that p53 expression is increased in areas of acute inflammation in UC and CD. Decreased expression in RM as compared wit h AI suggests that expression of p53 is reversible and gene regulation in these areas is different.