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[Expression of p21 WAF1/CIP1 protein in colorectal cancers: study of its relation to p53 mutation and Ki67 antigen expression].

Mutations of the p53 gene are the most common genetic alteration in malignant human tumors. A cyclin-dependent kinase inhibitor, p21WAF1/CIP1, is thought to be an important mediator of p53-induced cell cycle arrest. Although numerous studies have reported p53 expression and mutation in colorectal cancer few of them have correlated p53 expression with that of its downstream effector p21 and with the proliferation index as measured by expression of the Ki67 nuclear antigen. We studied p53, p21 and Ki67 expression by immunohistochemistry and molecular biology in 35 colorectal carcinomas. We compared these findings with each other and with clinical factors. Sixty three percent of tumors expressed p53 whereas seventy one percent expressed p21WAF1/CIP1. In adenocarcinomas, p21 staining was heterogeneous: p21-reactive cells were seen in the most differentiated areas. There was no correlation between p21WAF1/CIP1 and p53 expression, p53 mutation, Ki67 expression or clinical factors such as sex or location of the tumor. On the other hand, there was a statistical relationship between p21 expression and survival: our results indicated an association between high p21 expression and lower stages p21WAF1/CIP1 appears to be induced independently of p53 in these tumors and may be associated with differentiation rather than proliferation.