β1-integrin expression and function in human bladder cancer cells: Modulation by TNFα

Cytofluorimetric and biochemical analysis in two different grade human bladder cancer cell lines showed that G3 EJ cells exhibited higher levels of α5β1 and α6β1 heterodimers, and the G2 RT112 cell line higher levels of α2β1. Alpha6/beta4 receptor was detected only in RT112 cells. Adhesion assays with extracellular matrix proteins indicated that both cells bound to fibronectin, laminin and collagen 1, the adhesive properties being related to the integrin profile. Inhibition tests revealed that α5β1 mediated adhesion to fibronectin, α3β1 and α6B1 to laminin, and that α2β1 was the main mediator of adhesion to collagen I in both cell lines. In EJ but not in RT112 cells, tumor necrosis factor-α induced the upregulation of α2, which mediated increased adhesion to collagen I. The different effects of TNFα on the two cell lines were not attributable to differences in tumor necrosis factor responsiveness, as both cells expressed comparable levels of tumor necrosis factor receptor-1 and the tumor necrosis factor-inducible intercellular adhesion molecule-1.