title: Identification of diphtheria toxin R domain mutants with enhanced inhibitory activity against HB-EGF.
abstract: Heparin-binding epidermal growth factor-like growth factor (HB-EGF), a ligand of EGF receptor, is involved in the growth and malignant progression of cancers. Cross-reacting material 197, CRM197, a non-toxic mutant of diphtheria toxin (DT), specifically binds to the EGF-like domain of HB-EGF and inhibits its mitogenic activity, thus CRM197 is currently under evaluation in clinical trials for cancer therapy. To develop more potent DT mutants than CRM197, we screened various mutant proteins of R domain of DT, the binding site for HB-EGF. A variety of R-domain mutant proteins fused with maltose-binding protein were produced and their inhibitory activity was evaluated in vitro. We found four R domain mutants that showed much higher inhibitory activity against HB-EGF than wild-type (WT) R domain. These R domain mutants suppressed HB-EGF-dependent cell proliferation more effectively than WT R domain. Surface plasmon resonance revealed their higher affinity to HB-EGF than WT R domain. CRM197(R460H) carrying the newly identified mutation showed increased cell proliferation inhibitory activity and affinity to HB-EGF. These results suggest that CRM197(R460H) or other recombinant proteins carrying newly identified mutation(s) in the R domain are potential therapeutics targeting HB-EGF.
authors.affiliation: Department of Cell Biology and Department of Molecular Bacteriology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan; and Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Department of Cell Biology and Department of Molecular Bacteriology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan; and Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Mizushima
authors.affiliation: Department of Cell Biology and Department of Molecular Bacteriology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan; and Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Abe
authors.affiliation: Department of Cell Biology and Department of Molecular Bacteriology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan; and Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Iwamoto
authors.affiliation: Department of Cell Biology and Department of Molecular Bacteriology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan; and Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Haruki
authors.initials: H
authors.lastname: Nakamura
authors.affiliation: Department of Cell Biology and Department of Molecular Bacteriology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan; and Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan emekada@biken.osaka-u.ac.jp.
authors.forename: Eisuke
authors.initials: E
authors.lastname: Mekada
mesh_terms: D002460:Cell Line; D004167:Diphtheria Toxin / Q000737:chemistry / Q000235:genetics / Q000633:toxicity*; D066257:Heparin-binding EGF-like Growth Factor / Q000378:metabolism*; D006801:Humans; D009154:Mutation
chemical_list: D004167:Diphtheria Toxin; D066257:Heparin-binding EGF-like Growth Factor
keywords: CRM197; EGF receptor; HB-EGF; cancer; diphtheria toxin