CA4 and neoplasm: Based on the local high level of glutathione (GSH) in the tumor tissues, Liu et al. synthesized a novel GSH-responsive polyethylene glycol (PEG)-based poly(alpha lipoic acid) (PALA) nanocarrier, to which CA4 was bonded ot the surface of the nanoparticles via the PEG chain [349, 350].