MMP9 and pachyonychia congenita: Zhang et al. reported that propranolol is able to suppress PC cell proliferation and invasiveness in vitro and in vivo by inducing apoptosis and inhibiting the expression of factors responsible for invasion, including nuclear factor κB (NFκB), activator protein 1 (AP-1) and cAMP response element binding protein (CREB), as well as the expression of MMP-9, MMP-2 and vascular endothelial growth factor (VEGF) target genes [73,74].