Study on the Mechanism Regulating Cell Differentiation in Salivary Gland Tumor

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We investigated integrin expression in salivary gland tumors. Α2, α3 and β1 similarly expressed in normal salivary gland (NSG) and pleomorphic adenoma (PA), mucoepidermoid carcinoma (MC), and adenoid cystic carcinoma (ACC). On the other hand, α6 and β4 expressed at basal surface in NSG, PA and MC, but in scattered pattern in ACC. Therefore, we speculated that α6 β4 might have association with invasiveness of ACC rather than cell differentiation.Secondly, we investigated expression of TGF βs and their receptors which stimulate integrin expression and production of extra-cellular matrix. TGF β3 and TGF β RII expressed similarly, but TGF β1 and TGF β2 did not in MC. The former was observed with different intensity in almost all the salivary epithelial cells, in particular epidermoid cells. On the other hand, they were not detected in mucous cells and clear cells. Similar expression pattern was observed in PA and ACC.We immunohistochemically observed localization of osteopontin (OPN) which is ligand for αv integrin using the self-made antibody. OPN expression was observed in all the NSGs and benign and malignant salivary gland tumors tested. OPN was observed in ductal epithelial cells, but not in mucous cells of all the aboved tissues, which suggests the relationship between OPN expression and cell differentiation of salivary gland.Cell cycle regulators, p53, p21 and cycline E, were differently expressed depending on cell component. However, its diversity was supposed to be due to their proliferative ability. The relationship was observed between telomerase activity and malignancy of salivary gland tumor, but not cell differentiation.