Expression of β-catenin and REG Iα in relation to cell proliferative ability in salivary gland tumors.

β-catenin and its target gene products have been thought to play pivotal roles in the progression of various neoplasias. In the present study, we examined the expression of β-catenin and regenerating gene (REG) Iα in salivary gland tumors and investigated its relationship to their cell proliferative ability. Nineteen patients with pleomorphic adenoma (PA) and 17 patients with malignant salivary gland tumors, including 7 adenoid cystic carcinomas, 7 mucoepidermoid carcinomas and 3 polymorphous low-grade adenocarcinomas, were enrolled. The specimens that had been surgically resected from these patients were examined using immunohistochemistry for β-catenin, REG Iα and Ki67. The relationships between clinicopathological features and β-catenin or REG Iα expression were then analyzed. β-catenin immunoreactivity was positive in 14 PAs (73.3%) and 14 malignant salivary gland tumors (82.4%). Four (28.6%) of the 14 β-catenin-positive PAs showed clear β-catenin immunoreactivity at the plasma membrane (membrane type), while 10 (71.4%) showed diffuse immunoreactivity in the cytoplasm and nucleus but not at the plasma membrane (non-membrane type). Twelve (85.9%) of the 14 malignant salivary gland tumors showed non-membrane-type β-catenin expression. Six (31.6%) of the 19 PAs and 10 (58.8%) of the 17 malignant salivary gland tumors were positive for REG Iα expression. PAs with non-membrane-type β-catenin expression showed a significantly higher Ki67 labeling index than PAs with negative or membrane-type expression. Additionally, PAs that were REG Iα-positive showed a significantly higher Ki67 labeling index than those that were negative. Non-membrane-type β-catenin expression was related to REG Iα positivity in PA lesions. β-catenin and its associated REG Iα protein may play a role as growth-promoting factors in the development of salivary gland tumors.