title: Human monoclonal antibody GNX-8 directed to extended type 1 chain: Specific binding to human colorectal cancer.
abstract: We observed previously that two carbohydrate epitopes, extended type 1 chain Le(a)-Le(a) and Le(b)-Le(a), are expressed strongly in human gastric or colorectal cancer and cell lines derived therefrom, but their expression in human normal colorectal cells is highly limited. A monoclonal antibody, termed GNX-8, was established through immunization of "KM mice" with colonic cancer cell line Colo205, and with purified Le(b)-Le(a) glycosphingolipid, followed by screening human IgG directed to this antigen. KM mice possess human chromosome fragments and are capable of producing human immunoglobulin. GNX-8 reacted specifically with extended type 1 chain epitope Le(b)-Le(a), bound to all five colonic cancer cell lines so far tested, and displayed strong complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC). The antigens defined by GNX-8, expressed in Colo205 cells, were: (i) glycosphingolipids with epitope Le(b)-Le(a), whose reactivity was abolished upon defucosylation; (ii) glycoproteins with molecular mass range from 32 to >175 kDa, which were depleted in cells cultured in the presence of benzyl-alpha-GalNAc, indicating that these epitopes are O-linked glycans.Immunohistological reactivity of GNX-8 at 1 mug/ml, applied on tissue sections from colorectal and various other types of cancer, was much stronger than that with various normal cells and tissues. GNX-8 reactivity with normal cells required a much higher concentration (150 mug/ml), and this reactivity was based on cross-reaction with non-extended, normal blood group Le(b) antigen. Growth of subcutaneous xenograft of human colonic cancer cells, Colo205 or DLD-1, in nude mice or SCID mice, was strongly inhibited by administration of GNX-8. These observations, taken together, indicate that antibody GNX-8, directed specifically to Le(b)-Le(a) antigen, provides a novel direction of immunotherapy for human colorectal cancer. (c) 2009 UICC.
authors.affiliation: School of Pharmacy, College of Pharmacy, Taipei Medical University, 250 Wu Hsing Street, Taipei 110, Taiwan.
authors.forename: Mei-Chun
authors.initials: MC
authors.lastname: Yang
authors.forename: Feng-Lin
authors.initials: FL
authors.lastname: Hsu
authors.forename: Kazuko
authors.initials: K
authors.lastname: Handa
authors.forename: Senitiroh
authors.initials: S
authors.lastname: Hakomori
authors.forename: Mei-Hsien
authors.initials: MH
authors.lastname: Lee
authors.forename: Liahng-Yirn
authors.initials: LY
authors.lastname: Liu
authors.forename: Shu-Yen
authors.initials: SY
authors.lastname: Chang
authors.forename: Jerry
authors.initials: J
authors.lastname: Ting
authors.forename: Jaw-Yuan
authors.initials: JY
authors.lastname: Wen
authors.forename: Isao
authors.initials: I
authors.lastname: Ishida
authors.forename: Tong-Hsuan
authors.initials: TH
authors.lastname: Chang