LAUSR

Alpha‐momorcharin (α‐MMC), a type I ribosome‐inactivating protein, has attracted a great deal of attention because of its antitumor activity. However, the cytotoxicity of α‐MMC is limited due to insufficient cellular internalization in cancer cells. To enhance the cytotoxicity of α‐MMC, a heparin‐binding domain derived from heparin‐binding epidermal growth factor (named heparin‐binding peptide [HBP]) was used as a cell‐penetrating peptide and fused to the C‐terminus of α‐MMC. This novel α‐MMC‐HBP fusion protein was expressed and purified with a Ni2+‐resin. The N‐glycosidase activity and DNase activity assay indicated that the introduction of HBP did not interfere with the intrinsic bioactivities of α‐MMC. HBP was able to efficiently carry α‐MMC into the tested cancer cells and significantly enhance the cytotoxic effects of α‐MMC in a dose‐dependent manner. This enhanced cytotoxic ability occurred due to the higher level of cell apoptosis induced by α‐MMC‐HBP, which was demonstrated in western blot analysis in which α‐MMC‐HBP triggered caspase 8, caspase 9, casapase 3, and PARP more intensely than α‐MMC alone. α‐MMC‐HBP led to an upregulation of cleaved PARP and an increase in the Bax/Bcl‐2 ratio. Our study provided a new practical way to greatly improve the antitumor activity of α‐MMC, which could significantly expand the pharmaceutical applications of α‐MMC.