Sole expression of laminin γ2 chain in invading tumor cells and its association with stromal fibrosis in lung adenocarcinomas

Division of Surgery, Kanagawa Cardiovascular Respiratory Center, 6-16-1 Tomiokahigashi,Kanazawa-ku, Yokohama 236-0051Laminin-5 (LN-5), an important basement membrane (BM) protein consisting of laminin α3, β3and γ2 chains, has been suggested to be involved in tumor cell invasion and tissue repair. In thisstudy, the distribution of the LN-5 subunits in atypical adenomatous hyperplasia (AAH) and differ-ent types of adenocarcinomas of the lung was examined by immunohistochemical analysis. In AAHand non-sclerosing, well-differentiated adenocarcinomas, the LN γ2 chain was frequently detectedalong with the continuous BMs. These BMs were also positive for both LN α3 and β3 chains, sug-gesting that LN-5 had been deposited. In contrast, the cytoplasmic staining for the LN γ2 chainwas frequently observed in tumor cells of sclerosing, well-differentiated adenocarcinomas, as wellas of moderately and poorly differentiated adenocarcinomas, without any evidence of co-expressionof the LN α3 and β3 chains. This staining pattern of the LN γ2 chain was prominent in carcinomacells invading into interstitial stroma and was associated with the formation of a central scar in thetumor tissues. These results suggest that the LN γ2 chain monomer could be an important indica-tor of progression of lung adenocarcinoma.Key words: Laminin-5 — Laminin γ2 chain — Lung adenocarcinoma — Tumor invasion — Immuno-histochemistry