Expression of p21WAF1/CIP1 in colorectal adenomas and adenocarcinomas and its correlation with p53 protein expression

The expression of p53-Inducible cylln-dependent kinase Inhibitor, p21^WAF1/CIP1 in non-neopiastic mucosa, adenoma and adenocarclnoma of the colorectum was examined by immunohistochemistry and western bootting and Its relation with the expression of p53 protein was analyzed. Non-neoplastic epithelial cells at the surface area showing no proitferative activity expressed p21^WAF1/CIP1.The expression of p21^WAF1/CIP1 was lmmunohistochemlcally detected in 55% (206/377 of the adenomas and 66% (190/289) of the adenocarcinomas, respectively. The lncldence of strongly positive cases was significantly higher In the adenocarcinomas (27%) than In the adenomas (18%) ( P< .05). The incidence of cases wtth strong p21^WAF1/CIP1 expression was higher In stages 0,1 and 2 carcinomas than in stages 3 and 4 carcinomas ( P <0.05). A decrease in the incidence of cases with strong expression was detected in carclnomas Invading deeper than muscularis propria. The influence of strongly positive cases was signiflcantly lower in carcinomas with lymph node metastasis than those without metastasls ( P <0.05). The expression of p21 as well as p53 detected by western blotting was compatlble with the results of lmmunohistochemlstry in most cases examined. However, there was no significant correlatlon between the expression of p21^WAF1/CIP1 and the abnormal accumulation of p53. These findlngs overall suggest that: (i) the physiological expression of p21^WAF1/CIP1 may be associated with cellular senescence of colorectal mucosa; (ii) reduced expression of p21^WAF1/CIP1 participate in the progression of colorectal carcinoma; and (iii) p53-Independent paulway may be considerably Involved In the inductions of p21^WAF1/CIP1.