KLK4 and MMP20 Immunoexpression in Malign, Benign and Infiltrative Odontogenic Tumors

Objectives: Secreted by ameloblasts, the enzymes MMP20 (enamelisin) and KLK4 (kallikrein 4) play an important role in the enamel matrix degradation during amelogenesis. However, studies have shown that neoplastic cells are able to produce them, what can affect the tumoral infiltrative and metastatic behavior.
Methods: To assess the biological role of these enzymes in the odontogenic tumors their immunoexpression were analysed in the ameloblastoma (AM), adenomatoid odontogenic tumor (AOT), calcifying epithelial odontogenic tumor (CEOT), keratocyst odontogenic tumor with and without recurrence (KOT and KOTr), and odontogenic carcinoma (OC).
Results: Positive results were obtained in all benign lesions, with prevalence of 75 to 100% cells immunolabeled. Usually the patients were young, caucasian, female, with slow-growing tumor located in the mandible, causing asymptomatic swelling. No KLK4 immunoexpression was seen in the carcinomas, and the amount of cells positive to the MMP20 varied widely with percentages between 20 to 80%. Rapid evolution, recurrence, and age above 60 years characterized the malignant nature of these lesions.
Conclusions: The results showed that KLK4 and MMP20 enzymes apparently have little relevance to the tumoral infiltrative property, especially for malign tumors, considering the diversity and peculiarity of the lesions assessed. The high immunoexpression in benign lesions, remarkably the TOA, probably would be correlated to the differentiated tumoral cells that would be able to produce and degradate the enamel matrix-like substances. After all, the odontogenic tumor histogenesis commonly comes from epithelium that recently performed secretory activity in tooth formation. (Financial Support: FAPESP Proc. 2012/11295-9)