PPT1 and cancer: Regarding its mode of action, GNS561 was shown to suppress cancer cell growth via the induction of apoptosis resulting from inhibition of palmitoyl-protein thioesterase 1 (PPT1) activity, lysosomal unbound Zn2+ accumulation, impairment of cathepsin activity, blockage of autophagic flux, altered localization of mTOR, lysosomal membrane permeabilization and caspase activation 14.