title: Recombinant human hexamer-dominant IgM monoclonal antibody to ganglioside GM3 for treatment of melanoma.
abstract: OBJECTIVE
  L612, a human IgM monoclonal antibody produced by an EBV-transformed human B-cell line, binds to ganglioside GM3 and kills GM3-positive human melanoma cells in the presence of complement. It has been shown to be effective in some patients with late-stage melanoma. L612 consists of hexameric IgM (about 20%), pentameric IgM (about 74%), and other minor IgM molecules. Because hexameric IgM activates complement more effectively than pentameric IgM, we developed and evaluated a hexamer-dominant recombinant IgM for clinical applications.
  
  
  METHODS
  Chinese hamster ovary (CHO) cells were transfected with heavy- and light-chain genes of L612, with or without the joining-chain gene. Antitumor effects of the recombinant IgM secreted from CHO cells were evaluated in vitro and in vivo.
  
  
  RESULTS
  Recombinant IgM secreted from CHO cells without the joining chain (designated CA19) was approximately 80% hexameric, whereas recombinant IgM from CHO cells transfected with heavy-, light-, and joining-chain genes (designated CJ45) was about 90% pentameric. Both CA19 and CJ45 recombinant IgMs caused complement-dependent cytotoxicity against human and mouse melanoma cell lines, but the amount of CA19 required for 50% specific cytotoxicity was 5 to 10 times smaller. I.v. injection of CA19 compared with CJ45 or native L612 elicited more profound antitumor activity in nude rats bearing a GM3-positive mouse melanoma xenograft.
  
  
  CONCLUSIONS
  A hexamer-dominant human IgM against GM3 may provide a more potent treatment option for patients with GM3-positive melanoma.
authors.affiliation: Pharmaceutical Research Department III, Kamakura Research Laboratories, Chugai Pharmaceutical Co., Ltd., Kanagawa, Japan.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Azuma
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ishikawa
authors.forename: Shigeto
authors.initials: S
authors.lastname: Kawai
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Tsunenari
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tsunoda
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Igawa
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Iida
authors.forename: Masahiko
authors.initials: M
authors.lastname: Nanami
authors.forename: Masami
authors.initials: M
authors.lastname: Suzuki
authors.forename: Reiko F
authors.initials: RF
authors.lastname: Irie
authors.forename: Masayuki
authors.initials: M
authors.lastname: Tsuchiya
authors.forename: Hisafumi
authors.initials: H
authors.lastname: Yamada-Okabe
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D061067:Antibodies, Monoclonal, Humanized; D016466:CHO Cells; D045744:Cell Line, Tumor; D006224:Cricetinae; D003412:Cricetulus; D005679:G(M3) Ganglioside / Q000276:immunology*; D006801:Humans; D008545:Melanoma / Q000737:chemistry / Q000188:drug therapy* / Q000473:pathology; D011994:Recombinant Proteins / Q000627:therapeutic use; D012878:Skin Neoplasms / Q000737:chemistry / Q000188:drug therapy* / Q000473:pathology
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D005679:G(M3) Ganglioside; C521015:L612 monoclonal antibody; D011994:Recombinant Proteins