Secretion of collagen I and tenascin is modulated by laminin-111 in 3D culture of human adenoid cystic carcinoma cells

Adenoid cystic carcinoma is a frequently occurring malignant salivary gland neoplasm with high level of recurrence and distant metastasis (Dardick 1996). This tumour is histologically characterized by a sheet or island-like proliferation of round or cuboidal epithelial cells, with scanty cytoplasm and hyperchromatic large oval nuclei (Dardick 1996). Growth patterns are solid, tubular and pseudocystic (Seifert & Sobin 1992; Dardick 1996; Loducca et al. 2000). A prominent feature of adenoid cystic carcinoma is its affinity for basement membrane rich tissues, such as nerves and blood vessels, leading to perineural invasion (Dardick 1996). Electron microscopy of adenoid cystic carcinoma shows both luminal and myoepithelial cells (Dardick 1996). These cells are often separated by extracellular material, such as pools of basal lamina, collagen fibres, elastin and glycosaminoglycans (Dardick 1996). A conspicuous finding in the cribriform variant of adenoid cystic carcinoma is a thickened band of extensively reduplicated basement membrane (Dardick 1996). Immunohistochemical studies have also demonstrated the presence of basement membrane proteins in this neoplasm (Cheng et al. 1992, 1995; Loducca et al. 2000; Raitz et al. 2003). We are interested in studying the regulatory mechanisms underlying the secretion of extracellular matrix (ECM) molecules in this neoplasm. We have previously demonstrated that laminin modulates the phenotype of a human adenoid cystic carcinoma (CAC2) cell line (Freitas & Jaeger 2002; Freitas et al. 2004, 2007a,b). Our results have demonstrated that this protein is a key regulator of different phenotypic aspects of CAC2 cells. Cells grown in a three-dimensional (3D) gel of laminin-111 showed solid, pseudocystic and duct-like structures, hallmarks of the neoplasm in vivo (Freitas & Jaeger 2002). Thus, this molecule would be a good candidate to regulate secretion of ECM molecules in this cell line. We are investigating the role played by laminin-111 (Aumailley et al. 2005) regulating secretion of extracellular molecules in CAC2 cells. This in vitro analysis is justified by the prominent expression of ECM molecules in adenoid cystic carcinoma in vivo (Caselitz et al. 1986; Cheng et al. 1992, 1995; Loducca et al. 2000; Raitz et al. 2003). Light and electron microscopy were carried out in CAC2 cells grown embedded into a 3D gel of laminin-111. Laser scanning confocal microscopy of whole mount preparations was used to detect two ECM proteins, collagen I and tenascin.