title: A novel immunotoxin - rCCK8PE38 targeting of CCK-R overexpressed colon cancers.
abstract: BACKGROUND
  Cholecystokinin (CCK) receptors are overexpressed in numerous human cancers, such as pancreatic, colon and gastric cancers. Previous studies have shown that the specific receptor-binding property of CCK for CCK receptors (CCKRs) can be exploited to produce immunotoxins (ITs) that target cancer cells overexpressing CCK receptors.
  
  
  OBJECTIVE
  Construct a new IT-targeting CCKR-overexpressing colon cancers.
  
  
  METHODS
  To construct the CCKR-targeted IT, a reverse CCK8 peptide was fused with a modified 38-kDa truncated form of the Pseudomonas exotoxin (PE38KDEL). An efficient immunoaffinity purification procedure was used to produce a PE38-based IT. Several analyses, including CCK8 competition and indirect immunofluorescence assays, were performed to confirm the interaction between rCCK8 and CCKR. After cytotoxic assays on several cell lines, the anti-tumor activity of the new IT was detected in nude mice.
  
  
  RESULTS
  The rCCK8PE38 IT showed specific cytotoxicity for two colon cancer cell lines and one gastric cancer cell line. After purification, 18-26 mg of pure rCCK8PE38 per 1 L of culture was obtained. Purified rCCK8PE38 showed high cytotoxicity in colon cancer cell lines with IC50 values of 0.8-3.5 ng/mL. The results of the CCK8 competition and indirect immunofluorescence assays showed that rCCK8 had a specific interaction with CCKR. Nude mice inoculated with HCT-8 tumor xenografts were treated with rCCK8PE38, which efficiently decreased the tumor size in those mice.
  
  
  CONCLUSIONS
  All of these data suggest that rCCK8PE38 has potential as a new immunotherapy agent. Furthermore, the results of this study further support the high value of the immunoaffinity method for IT purification procedures.
authors: Key Laboratory of Zoonosis Research, Ministry of Education, Institute of Zoonosis, Jilin University , Changchun , PR China .
authors: Shiqi
authors: S
authors: Gao
authors: Jie
authors: J
authors: Song
authors: Fengge
authors: F
authors: Chen
authors: Quan
authors: Q
authors: Wang
authors: Xilin
authors: X
authors: Liu
authors: Honglin
authors: H
authors: Ren
authors: Yansong
authors: Y
authors: Li
authors: Xingyu
authors: X
authors: Meng
authors: Yu
authors: Y
authors: Zhou
authors: Shiying
authors: S
authors: Lu
authors: Pan
authors: P
authors: Hu
authors: Weihua
authors: W
authors: Tong
authors: Zengshan
authors: Z
authors: Liu
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002766:Cholecystokinin / Q000008:administration & dosage* / Q000494:pharmacology; D003110:Colonic Neoplasms / Q000276:immunology / Q000628:therapy*; D005098:Exotoxins / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007167:Immunotherapy / Q000379:methods; D000922:Immunotoxins / Q000008:administration & dosage* / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D010446:Peptide Fragments / Q000008:administration & dosage* / Q000494:pharmacology; D011549:Pseudomonas / Q000378:metabolism; D011949:Receptors, Cholecystokinin / Q000235:genetics / Q000378:metabolism*; D013274:Stomach Neoplasms / Q000276:immunology / Q000628:therapy; D023041:Xenograft Model Antitumor Assays
chemical_list: D005098:Exotoxins; D000922:Immunotoxins; D010446:Peptide Fragments; D011949:Receptors, Cholecystokinin; C410885:cholecystokinin 8; D002766:Cholecystokinin
keywords: CCKR; Pseudomonas exotoxin A; colon cancer; rCCK8PE38; recombinant immunotoxin