ALTERED EXTRACELLULAR MATRICES INFLUENCE CELLULAR PROCESSES AND NUCLEAR MATRIX ORGANIZATIONS OF OVERLYING HUMAN BLADDER UROTHELIAL CELLS

A central issue in tumor biology is the understanding of the interacti ons between tumor cells and their environment. Using normal and ras on cogene transfected rat fibroblast cells, we now demonstrate that the t ransfected cells make altered extracellular matrices (ECM) and that th eir resulting ECM influence the proliferation and genetic regulation o f human bladder cancer EJ cells. Using Western blot analyses, we obser ved that the ras transfected fibroblast cells lacked the ability to pr oduce extracellular matrix component laminin whereas the normal parent al fibroblast cells were able to produce intact laminin. Both transfec ted and nontransfected fibroblast cells were able to synthesize other extracellular matrix molecules such as type IV collagen and fibronecti n. Human bladder tumor EJ cells were grown on ECM derived from normal and transfected rat fibroblast cells, and the proliferation rate and t ype IV collagen mRNA expression of EJ cells were determined. We observ ed that EJ cells, when grown on ECM derived from the ras transfected f ibroblast cells, had a higher growth rate than when grown on ECM deriv ed from the normal fibroblast cells (P < 0.037). Furthermore, EJ cells grown on ECM derived from transfected fibroblast cells showed up-regu lation of type IV collagen mRNA expression when compared with EJ cells grown on ECM derived from nontransfected fibroblast cells. Finally EJ cells grown on purified laminin but not on collagen IV coated flasks showed the same level of type IV collagen mRNA expression as when grow n on ECM derived from nontransfected parental fibroblast cells. Haptot actic/motility assays with EJ cells and ECM derived from ras transfect ed and nontransfected fibroblast cells demonstrated that ECM of ras tr ansfected fibroblast cells, but not the parental fibroblast cells, pro vided a permissive or fertile soil for EJ tumor cell invasion. Finally , two-dimensional gel electrophoresis of S-35-labeled nuclear matrix p roteins of EJ cells cultured on ECM derived from ras transfected fibro blast cells revealed expression of proteins in the molecular weight ra nge of M(r) 35,000-45,000 and isoelectric focusing pH range of 5.5 to 6.0. These proteins were not present in EJ cells cultured on ECM deriv ed from parental nontransfected fibroblast cells. We conclude that ext racellular matrices derived from transformed stroma producing cells ma y influence the proliferation, genetic regulation, and maintenance of the overlying urothelial tumor cells. The mechanism by which the ECM m ay influence cellular behavior and phenotype may be in their ability t o modulate the nuclear matrix proteins of the overlying cell.