Figure 4.

Adhesion-mediated amplification of STAT3 phosphorylation in a complex model of the bone marrow microenvironment requires β₁ integrin. Myeloma cells were either grown in monoculture (M) or in co-culture with patient-derived bone marrow stromal cells (BMSCs). Co-cultured myeloma cells were either separated from BMSCs by transwell inserts that allow soluble factor diffusion (Tw) or adhered to BMSC monolayers (Cx, a). Adhesion to patient-derived BMSCs enhances PYK2, JAK1 and STAT3 phosphorylation in myeloma cells lines (b, c) and patient specimens (d, e). Knockdown of β₁ integrin diminishes the activation of PYK2 induced by adhesion to BMSCs (f, g). All immunoblots are representative of at least three independent experiments. RNA interference data were repeated using three unique constructs per target.