Sole Expression of Laminin γhain in Invading Tumor Cells and Its Association with Stromal Fibrosis in Lung Adenocarcinomas

Laminin‐5 (LN‐5), an important basement membrane (BM) protein consisting of laminin α3, β3 and γ2 chains, has been suggested to be involved in tumor cell invasion and tissue repair. In this study, the distribution of the LN‐5 subunits in atypical adenomatous hyperplasia (AAH)and different types of adenocarcinomas of the lung was examined by immunohistochemical analysis. In AAH and non‐sclerosing, well‐differentiated adenocarcinomas, the LN γ2 chain was frequently detected along with the continuous BMs. These BMs were also positive for both LNα3 and β3 chains, suggesting that LN‐5 had been deposited. In contrast, the cytoplasmic staining for the LNγ2 chain was frequently observed in tumor cells of sclerosing, well‐differentiated adenocarcinomas, as well as of moderately and poorly differentiated adenocarcinomas, without any evidence of co‐expression of the LNα3 and β3 chains. This staining pattern of the LNγ2 chain was prominent in carcinoma cells invading into interstitial stroma and was associated with the formation of a central scar in the tumor tissues. These results suggest that the LNγ2 chain monomer could be an important indicator of progression of lung adenocarcinoma.