Immunohistochemical Expression of Integrins and CD44 in Ameloblastomas

Introduction Odontogenic epithelium is responsible for tooth development under physiologic conditions and can give rise to tumors or cysts in the jaws (1-3). Ameloblastoma is the most frequently encountered tumor arising from odontogenic epithelium and is characterized by a benign but locally invasive behavior with a high tendency to recur (2, 4). Histologically, ameloblastoma shows considerable variation, including follicular, plexiform, acanthomatous, granular cell, basal cell and desmoplastic types (4). Clear cell odontogenic tumor (CCOT) is an unusual intraosseous tumor histologically characterized by odontogenic epithelial cells with clear vacuolated cytoplasm (4, 5). Although the 1992 World Health Organization (WHO) histological classification of odontogenic tumors newly classified CCOT as a benign tumor of the epithelial odontogenic apparatus (4), this tumor has been reported to include both benign and malignant varieties (6). These epithelial odontogenic tumors histologically resemble the epithelial odontogenic apparatus, such as enamel organ or dental lamina, in some respects; however, the detailed mechanisms of oncogenesis and cytodifferentiation remain unknown. Cell-to-cell adhesion is indispensable for the regulation of cellular behavior, and a number of cell adhesion molecules mediating many kinds of adhesion have been identified (7, 8). Integrins are a family of cell surface glycoproteins that mediate cell-cell and cell-extracellular matrix adhesion (9, 10). Each integrin is a heterodimer comprising two non-covalently linked subunits, a and b (7, 10). There are at least 18 a subunits and 8 b subunits, and more than 20 different ab combinations have been identified and classified into several subfamilies sharing a common b subunit (10). Integrins can bind multiple ligands, such as different types of collagens, fibronectins and laminins, and play an important role in regulating cellular interactions during growth, development and differentiation (7, 10-13). Changes in integrin expression have been found in many neoplastic tissues and are implicated in tumor cell invasion and metastasis (11, 1417). CD44 is a family of cell surface glycoproteins that play a role in cell-cell and cell-extracellular matrix adhesion and interactions (18, 19). The CD44 gene contains at least 20 exons (19). The standard form of CD44 (CD44s) Immunohistochemical Expression of Integrins and CD44 in Ameloblastomas