Localization of the invadopodia-related proteins actinin-1 and cortactin to matrix-contact-side cytoplasm of cancer cells in surgically resected lung adenocarcinomas.

OBJECTIVES Actin-associated proteins at cell-matrix-contact sites form invadopodia in cancer cells and participate in migration, matrix degradation and invasion. We investigated an alteration of subcellular localization of invadopodia-related actin-associated proteins, actinin-1 and cortactin, in lung adenocarcinomas, its clinical significance, and its possible regulatory factors. METHODS Invadopodia-related proteins, actinin-1 and cortactin, were immunohistochemically examined in 90 cases of lung adenocarcinomas. Expression of invadopodia-associated proteins and their possible regulators in lung adenocarcinomas were examined by real-time RT-PCR, database search, and immunohistochemistry. RESULTS Actinin-1 and cortactin showed matrix-contact-side localization in adenocarcinoma cells, but rarely in normal bronchiolar epithelial cells, alveolar cells, or precursor lesion atypical adenomatous hyperplasia cells. Immunoelectron-microscopic examination of adenocarcinoma cells revealed actinin-1 localization to matrix-contact-side cytoplasm with cytoplasmic protrusions. Matrix-contact-side localization of actinin-1 and cortactin was correlated with tumor stages, lymph node metastasis, vascular permeation, and loss of basement membrane. The tumor-specific survival rate was worse for the group in which matrix-contact-side localization of cortactin was high than for the low group. mRNA of the Rho guanine exchange factor epithelial cell transforming sequence-2 (Ect2) tended to be overexpressed in lung adenocarcinomas and cytoplasmic expression of Ect2 tended to be correlated with matrix-contact-side localization of actinin-1. CONCLUSION Matrix-contact-side localization of invadopodia-related proteins in the lung adenocarcinoma cells were correlated with invasion, metastasis, and poor prognosis. Ect2 was a possible regulator of matrix-contact-side localization of invadopodia-related proteins.