title: Ability of luteinizing hormone releasing hormone-Pseudomonas aeruginosa exotoxin 40 binding to LHRH receptor on human liver cancer cells.
abstract: OBJECTIVE
  To explore the ability of recombinant toxin luteinizing hormone releasing hormone-Pseudomonas aeruginosa exotoxin 40 (LHRH-PE40) and LHRH binding to LHRH receptor (LHRHR) on the membrane surface of human liver cancer HEPG cells.
  
  
  METHODS
  LHRH was labeled by using (125)I with enzymatic reaction. The affinity and receptor volume of LHRH-PE40 and LHRH binding to LHRHR on the membrane surface of human liver cancer cells were measured with radioligand receptor assay.
  
  
  RESULTS
  The specific activity of LHRH labeled with (125)I was 2.7 x 10(4) kBq/microL, and its radiochemical purity reached to 99.2-99.7%. The binding of (125)I to LHRH was maximal for 240 min in the warm cultivation, and this binding was stabilized. The inhibiting rates of (125)I-LHRH and LHRH on the proliferation of human liver cancer HEPG cells were not significantly different. On the basis of the saturation curve of (125)I-LHRH binding to the membrane LHRHR of HEPG cells, (125)I-LHRH of 1 x 10(5) cpm was selected for radioligand receptor assay. The affinity constants (Kd) of LHRH-PE40 and LHRH binding to the membrane LHRHR of HEPG cells were 0.43+/-0.12 nmol/L and 4.86+/-1.47 nmol/L, respectively, and their receptor volumes were 0.37+/-0.15 micromol/g and 0.42+/-0.13 micromol/g, respectively. The binding of LHRH-PE40 to the membrane protein of normal liver cells was not observed.
  
  
  CONCLUSIONS
  The recombinant toxin LHRH-PE40 binding to the membrane surface of LHRHR of human liver cancer HEPG cells was very strong, while the specific binding of it to normal liver cells was not observed. The results provide an important experimental basis for the clinical application of LHRH-PE.
authors.affiliation: Radiobiology Research Unit of Ministry of Public Health, School of Public Health, Jilin University, Changchun 130021, Jilin Province, China. gongsl@163.com
authors.forename: Shou-Liang
authors.initials: SL
authors.lastname: Gong
authors.forename: Gang
authors.initials: G
authors.lastname: Zhao
authors.forename: Hong-Guang
authors.initials: HG
authors.lastname: Zhao
authors.forename: Wen-Tian
authors.initials: WT
authors.lastname: Lu
authors.forename: Guang-Wei
authors.initials: GW
authors.lastname: Liu
authors.forename: Ping
authors.initials: P
authors.lastname: Zhu
mesh_terms: D036002:ADP Ribose Transferases / Q000493:pharmacokinetics* / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000493:pharmacokinetics* / Q000494:pharmacology; D001427:Bacterial Toxins / Q000493:pharmacokinetics* / Q000494:pharmacology; D001667:Binding, Competitive; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D005098:Exotoxins / Q000493:pharmacokinetics* / Q000494:pharmacology; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology; D011966:Receptors, LHRH / Q000378:metabolism*; D037521:Virulence Factors / Q000493:pharmacokinetics* / Q000494:pharmacology; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D000970:Antineoplastic Agents; D001427:Bacterial Toxins; D005098:Exotoxins; D007987:Gonadotropin-Releasing Hormone; D011966:Receptors, LHRH; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A