CTTN and rheumatoid arthritis: RA-FLS morphology changed in response to IL-1β with increased cytoplasm volume and reorganization of the actin cytoskeleton; stress fibers of F-actin (phalloidin) filaments (green staining) and cortactin (red dot) increased, and more invadopodia (co-colocalization of F-actin and cortactin) were observed.