Distribution of basement membrane anchoring molecules in normal and transformed endometrium: altered expression of laminin gamma2 chain and collagen type XVII in endometrial adenocarcinomas.

Basement membranes (BMs) play an important role in anchoring epithelial cells and separating them from the adjacent stroma. Altered composition and assembly of BMs may influence carcinoma cell growth and invasion. Using immunohistochemistry and in situ hybridization, we investigated the expressions of the BMs components laminin-5 (Ln-5) subunits and collagen types IV, VII and XVII in normal endometrium and compared them to the expression pattern in hyperplastic and neoplastic endometrium. Chains of Ln-5 (alpha3beta3gamma2) and types IV, VII and XVII collagens were observed in normal endometrium. In hyperplastic endometrium, laminin gamma2 chain and type XVII collagen showed intensified expression in foci of dispersed epithelial cells. Individual carcinoma cells in adenocarcinomas of low differentiation grade displayed increased laminin gamma2 chain and type XVII collagen immunoreactivity and mRNA synthesis, whereas type VII collagen usually showed decreased expression. Laminin and type IV collagen showed BM disruptions, especially in tumors with low differentiation. Our results indicate that all the BM anchoring molecules investigated are expressed in normal endometrium, but the expression of laminin gamma2 chain and collagen type XVII is altered in endometrial adenocarcinomas, which support their role in malignant growth.