Extracellular matrix proteins and VLA integrins expression in the microenvironment of human lung carcinoma

In order to gain an insight into interactions between human cancer and the surrounding host tissues, surgical samples of lung carcinoma of distinct histological types were examined for the expression of extracellular matrix (ECM) proteins and very late antigen (VLA) integrins, by means of a panel of monoclonal antibodies and immunohistochemistry of frozen tissue sections. It has been found that fibronectin (FN), tenascin (TN) and to a lesser degree collagen IV were abundant in the immediate vicinity of the tumor, but only TN penetrated tumor mass. FN isoforms were scarce or undetectable within the tumor area. The walls of blood vessels in the vicinity of the tumor showed increased an expression of collagen IV and laminin. The latter was occasionally absent within the basal membrane of cancer cells. The expression of EMC proteins was inversely proportional to the intensity of mononuclear tumor infiltrating cells (TIC). VLA integrins were present on both types of the cells: TIC and tumor cells. Percentage of positive TIC varied from 20% to 70%, depending on VLA integrin tested. VLA-3 was demonstrated on most of the cells of squamous carcinoma, but was almost absent on those of anaplastic small cell carcinoma one. In metastatic lymph node, VLA-4 was strongly expressed on tumor cells comparing to lymphoid ones. These data show that VLA integrins and their EMC ligands play apparently an important, but still obscure role in the interactions between lung carcinoma and its host.