Volume 14, Number 3, September 2002

Expression of p21WAF1/CIP1, p53, and Ki-67 Proteins in Malignant Ameloblastomas and Ameloblastomas

Souichi Yanamoto, Goro Kawasaki, Akio Mizuno
Division of Oral and Maxillofacial Surgery, Department of Developmental and Reconstructive Medicine, Course of Medical and Dental Sciences, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan

Abstract
Objective: The cyclin-dependent kinase inhibitor p21 has been identified as a downstream effector or target of the p53 tumour suppressor gene. The aims of this study were to immunohistochemically assess the proliferative activity and to clarify the possible roles of p21 and p53 genes in oncogenesis of malignant ameloblastoma and ameloblastoma.
Patients and Methods: Expression of p21, p53, and cellular proliferation was investigated using the Ki-67 immunohistochemical labelling index in specimens from 2 patients with malignant ameloblastomas and 10 patients with ameloblastomas.
Results: Expression of p21 was immunohistochemically detected in 50% of malignant ameloblastomas, 0% of ameloblastomas, and 100% of healthy oral mucosa. Expression of p53 was immunohistochemically detected in 100% of the malignant ameloblastomas, 40% of ameloblastomas, and 0% of healthy oral mucosa. The p53-labelling index of malignant ameloblastomas was significantly higher than that of other ameloblastomas. There was no significant difference between Ki-67 antigen reactivity in p53 protein-positive tumours and negative tumours.
Conclusion: These findings suggest that expression of p21 and p53 proteins could be associated with oncogenesis in ameloblastoma. The expression of p53 could be associated with malignant transformation rather than cellular proliferative activity. However, the correlation between p21 and p53 has not yet been sufficiently clarified in malignant ameloblastoma and ameloblastoma.

Key words:
Ameloblastoma, Oncogene protein p21 (ras), protein p53, Ki-67 antigen

Asian J Oral Maxillofac Surg. 2002;14:155-160.
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