title: Diphtheria toxin mutant CRM197 possesses weak EF2-ADP-ribosyl activity that potentiates its anti-tumorigenic activity.
abstract: CRM197, a mutated diphtheria toxin (DT), has long been recognized to be a non-toxic protein. Based on its non-toxic feature, this protein has been utilized for various purposes, including as an inhibitor of heparin-binding EGF-like growth factor (HB-EGF) and as an immunological adjuvant for vaccination. Here we show evidence that CRM197 has a weak toxicity. This toxicity was observed in cells over-expressing the DT receptor/proHB-EGF, but not in parental cells, indicating that the toxicity was mediated through DT receptor. CRM197 did not show any toxicity toward DT-resistant cells, which have a mutation in elongation factor 2, and a cell-free assay revealed the existence of weak EF-2-ADP ribosylation activity in fragment A of CRM197. Thus, the present study indicates a requirement for specific care in the use of CRM197 at a high dosage, although the toxicity of CRM197 is about 10(6) times less than that of wild-type DT. We found that a monoclonal antibody to DT inhibited CRM197 toxicity, but did not affect the inhibitory activity of CRM197 toward HB-EGF-induced mitogenic activity. CRM197 strongly inhibits tumour growth in nude mice. The anti-DT monoclonal antibody administered with CRM197 reduced the anti- tumourigenic effect of CRM197, indicating that the toxicity of CRM197 potentiates its anti- tumourigenic effect.
authors.affiliation: Department of Cell Biology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Kageyama
authors.forename: Minako
authors.initials: M
authors.lastname: Ohishi
authors.forename: Shingo
authors.initials: S
authors.lastname: Miyamoto
authors.forename: Hiroto
authors.initials: H
authors.lastname: Mizushima
authors.forename: Ryo
authors.initials: R
authors.lastname: Iwamoto
authors.forename: Eisuke
authors.initials: E
authors.lastname: Mekada
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000970:Antineoplastic Agents / Q000633:toxicity*; D001426:Bacterial Proteins / Q000235:genetics / Q000633:toxicity*; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D004167:Diphtheria Toxin / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D005260:Female; D006493:Heparin / Q000378:metabolism; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008934:Mitogens / Q000378:metabolism; D009154:Mutation; D020652:Peptide Elongation Factor 2 / Q000378:metabolism*; D014709:Vero Cells
chemical_list: D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D001426:Bacterial Proteins; D004167:Diphtheria Toxin; C587884:Hbegf protein, mouse; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D008934:Mitogens; D020652:Peptide Elongation Factor 2; C028581:CRM197 (non-toxic variant of diphtheria toxin); D000246:Adenosine Diphosphate Ribose; D006493:Heparin