FURIN and neoplasm: Liu et al [421] were the first to introduce and apply a new concept in which replacing the natural furin cleavage site in anthrax PA protein (such cleavage must occur on the cell surface in order to achieve binding and internalization of a catalytic LF and EF) with a sequence recognized by a tumor‐associated protease may confer the recombinant molecule with the ability of targeting the protease overexpressing cells.