Integrin β4 neoexpression suppresses fibroblast aggregation under anoikis conditions. Formation of fibroblast aggregates under anoikis conditions in (A) the absence or (B) the presence of integrin β4. Fibroblasts (5 × 105) were plated with RSM, MCF7 CM, or MDA-MB-231 CM on poly-HEMA-coated six-well plates and incubated for 24 hours. The formation of cell aggregates was observed with phase microscopy. (C) The scattering of integrin β4-expressing fibroblasts under anoikis conditions was not affected by blocking the laminin-332/integrin interaction. Fibroblasts (2.5 × 104) were plated with RSM, MCF7 CM, or MDA-MB-231 CM on poly-HEMA-coated 96-well plates with blocking antibodies against integrin β1 or β4 (diluted 1:100 with RSM) or MDA-MB-231 CM for 24 hours. (D) Decreased expression of β-catenin may cause reduced fibroblast aggregation. Suspended cells were collected, lysed, and subjected to Western blot analysis of β-catenin expression.