The Plasmodium Circumsporozoite Protein, a Novel NF-κB Inhibitor, Suppresses the Growth of SW480

The blocking of NF-κB activation is a promising strategy for the treatment of colorectal cancer. The circumsporozoite protein (CSP), a key component of the sporozoite stage of the malaria parasite, was recently reported to block NF-κB activation in hepatocytes. Thus, we investigated the effect of the CSP on the growth of the human colon cancer cell line, SW480. We demonstrated that transfection with a recombinant plasmid expressing CSP inhibited the proliferation of SW480 in a dose-dependent manner and induced the apoptosis of SW480. A NF-κB gene reporter assay showed that both the CSP and its nuclear localization signal (NLS) motif could equally suppress the activation of NF-κB following the stimulation with human recombinant TNF-α in the SW480. Furthermore, western blot analysis indicated that NLS did not affect the phosphorylation and degradation of IκB, but could sharply inhibit the nuclear translocation of NF-κB in TNF-α stimulated SW480. Hence, our data suggest that the CSP might be explored as a new NF-κB inhibitor for the treatment of colorectal cancer.