Acta Histochemica 115 (2013) 564–568 Contents lists available at SciVerse ScienceDirect Acta Histochemica j o ur nal hom epage: www.elsevier.de/acthis Immunohistochemical expression of metallothionein in pleomorphic adenoma of minor salivary glands: A role in the control of apoptosis? Alessandra de Castro Miranda Viana a , Daniela Cotta Ribeiro a , Taynara Nunes Guedes Florêncio a , Vanessa Torres Santos a , Alexandre Andrade Sousa b , Maria Cássia Ferreira Aguiar a,∗ a Department of Oral Surgery and Pathology, School of Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil b Instituto Alfa de Gastroenterologia (IAG), Hospital das Clínicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil a r t i c l e i n f o Article history: Received 19 September 2012 Received in revised form 10 December 2012 Accepted 11 December 2012 Keywords: Pleomorphic adenoma Metallothionein Bcl-2 Apoptosis Minor salivary glands Immunohistochemistry a b s t r a c t Pleomorphic adenoma is the most common benign neoplasm of both the major and minor salivary glands. The histological features are diverse and are characterized by the involvement of epithelial–myoepithelial structures. Metallothionein is a cysteine-rich protein present in myoepithelial cells of several benign and malignant neoplasms. The function of metallothionein is associated with DNA protection, oxidative stress and apoptosis. The purpose of this study was to evaluate the expression of metallothionein in pleomorphic adenoma of the minor salivary glands. Additionally, we investigated the association of the clinicopatho- logical features of the lesions with metallothionein, specifically its association with Bcl-2, in an attempt to evaluate the role of metallothionein in the control of apoptosis. Thirty-five cases of pleomorphic adenoma were selected and immunohistochemistry was performed for metallothionein and Bcl-2 proteins. The proteins were quantified by the Quickscore method. The samples showed epidemiological characteristics similar to those described in the literature. We did not find an association between the clinicopathological characteristics of pleomorphic adenomas and the proteins studied, but an association between metallo- thionein and Bcl-2 was demonstrated. The results suggest that metallothionein may have a role in the control of apoptosis in pleomorphic adenoma. © 2012 Elsevier GmbH. All rights reserved. Introduction Metallothionein (MT) is a highly conserved cysteine-rich protein that occurs in 4 isoforms. MTs I and II are the best characterized MTs and are expressed in many tissues, including normal and tumoral epithelial and myoepithelial cells of salivary glands (Sunardhi- Widyaputra et al., 1995; Yamada et al., 2000; Hecht et al., 2002; Alves et al., 2007). Multiple functions have been demonstrated for MT. These proteins are present during the differentiation of human salivary gland tissues (Hecht et al., 2002), however, their exact role in salivary gland tumors is not well known. Pleomorphic adenoma (PA) shows slow growth reflecting a low proliferation index (Alves et al., 2002; Aoki et al., 2004). It is not known if the histological variability of the tumor is associated with its growth speed, however some studies showed that the stroma-rich tumors attained a significantly larger size than the stroma-poor tumors suggesting that the stromal tumors grow at a ∗ Corresponding author at: Universidade Federal de Minas Gerais, Faculdade de Odontologia, Departamento de Clínica, Patologia e Cirurgia Odontológicas, Avenida Antônio Carlos, 6627, Sala 3201, Pampulha, CEP: 31.270-901, Belo Horizonte, Minas Gerais, Brazil. E-mail address: cassiafa@ufmg.br (M.C.F. Aguiar). faster rate (Cesinaro et al., 1994; Alves et al., 2002). The growth rate of a tumor depends on the balance between proliferation and loss of tumor cells. Studies have demonstrated that MT can influence tumor growth by modulating cell proliferation and death, espe- cially apoptosis (Zhang and Takenaka, 1998; Li et al., 2003; Nielsen et al., 2007; Yamasaki et al., 2006). Many other proteins modulate apoptosis, such as Bcl-2, a proto- oncogene that inhibits apoptosis (Abd-Elhamid and Elshafei, 2009). Studies have demonstrated that MT can reduce apoptosis via Bcl-2 (Ambjorn et al., 2008; Pedersen et al., 2009). In the present study, we studied the expression of MT in PA of salivary glands and investigated the association of this pro- tein with Bcl-2. Additionally, we verified the association of MT with clinicopathological features of the tumor and described its immunohistochemical pattern in the normal salivary glands asso- ciated and not associated with the tumor. Materials and methods Tumor samples Formalin-fixed, paraffin-embedded tissue specimens from PAs of the salivary glands were selected from the files of the Oral 0065-1281/$ – see front matter © 2012 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.acthis.2012.12.004