Chemotaxis and haptotaxis of human malignant mesothelioma cells: effects of fibronectin, laminin, type IV collagen, and an autocrine motility factor-like substance

Abstract

A human malignant pleural mesothelioma cell line (STAV) was studied with respect to production of the extracellular matrix components laminin, type IV collagen, and fibronectin, and interactions with these proteins in vitro. We also analyzed STAV cell serum-free conditioned medium with respect to the possible presence of "autocrine motility factor-like" substance. Sodium dodecylsulfate-polyacrylamide gel electrophoresis of biosynthetically labeled STAV serum-free conditioned medium showed that STAV cells released several proteins into the medium, including components with molecular weights of 850,000, 540,000 and 440,000. Using Western blotting we identified these proteins as laminin, type IV collagen, and fibronectin, respectively. By immunocytochemistry laminin, type IV collagen, and fibronectin were detected as a matrix surrounding the cells. Plastic culture dishes coated with microgram quantities of laminin, type IV collagen, and fibronectin induced attachment and spreading of STAV cells. Laminin, type IV collagen, and fibronectin stimulated directional (chemotactic) migration of STAV cells in Boyden chambers fitted with 8 microns filters. The same cells also migrated to insoluble step gradients of filter-bound extracellular matrix components (haptotaxis). When STAV serum-free conditioned medium was separated by using fast protein liquid chromatography Superose 6 gel filtration, two motility-inducing protein peaks were detected. The first peak contained proteins with molecular weight > 220,000 that had both chemotactic and haptotactic properties, while the second peak contained material with apparent molecular weights of approximately 67,000 that had chemotactic and chemokinetic (random motility) but not haptotactic properties. Analysis of the M(r) 67,000 material indicated that it was a heat-sensitive and trypsin-digestible protein. The production of both soluble and insoluble extracellular matrix components by human mesothelioma cells and the motile response to these molecules as well as the production of a M(r) 67,000 autocrine motility factor-like substance may be important for the highly invasive motile behavior of this tumor.