Immunoexpression of Matrilysins in Pleomorphic Adenomas

Objectives:Matrylisins (Matrix metalloproteinase-7 and -26; MMP-7 and -26) constitute the most recent MMP-group that are implied in the normal tissue formation and repair and in the neoplastic transformation and tumoral progression of several human tissues. Although these proteins are mainly expressed by epithelial tissues, the present work is the first to evaluate their concomitant expression in normal and neoplastic human salivary gland tissue. Methods: We evaluated and compared the immunohistochemical expression of MMP-7 and MMP-26 in 3 μ-thickness sections of 12 pleomorphic adenomas from salivary glands and of 11 samples of embryonic (n = 5) and adult (n = 6) human salivary glands. For statistical analysis of the obtained MMPs immunoexpression-scores, the Mann-Whitney and Fisher^xs exact tests were performed (α = 0.05). Results: The expression of MMPs occurred preferentially in forming ducts and in adjacent basement membrane of embryonic glands and only in the ducts of the adult glands. Expression of both MMPs was similar (p = 0.867) between embryonic and adult glands, although, quantitatively, the MMP-7 was more stained in the embryonic and the MMP-26 in the adult glands. When compared with the normal salivary glands, the pleomorphic adenomas exhibit more intense staining to MMPs (p < 0.001) independently of tumoral stroma-type, although MMP-7 was more expressed than MMP-26 (p = 0.045). Furthermore, it observed statistical correlation of the MMP-7 (p < 0.001) and MMP-26 (p < 0.001) scores among studied tissues. Conclusions: We suggest that the matrilysins (MMP-7 and MMP-26) may play specific and important roles the development of salivary gland tissue and in its neoplastic progression to pleomorphic adenoma.