title: A murine monoclonal antibody directed against the carboxyl-terminal domain of GRP78 suppresses melanoma growth in mice.
abstract: The HSP70 family member GRP78 is a selective tumor marker upregulated on the surface of many tumor cell types, including melanoma, where it acts as a growth factor receptor-like protein. Receptor-recognized forms of the proteinase inhibitor α2-macroglobulin (α2M*) are the best-characterized ligands for GRP78, but in melanoma and other cancer patients, autoantibodies arise against the NH2-terminal domain of GRP78 that react with tumor cell-surface GRP78. This causes the activation of signaling cascades that are proproliferative and antiapoptotic. Antibodies directed against the COOH-terminal domain of GRP78, however, upregulate p53-mediated proapoptotic signaling, leading to cell death. Here, we describe the binding characteristics, cell signaling properties, and downstream cellular effects of three novel murine monoclonal antibodies. The NH2-terminal domain-reactive antibody, N88, mimics α2M* as a ligand and drives PI 3-kinase-dependent activation of Akt and the subsequent stimulation of cellular proliferation in vitro. The COOH-terminal domain-reactive antibody, C38, acts as an antagonist of both α2M* and N88, whereas another, C107, directly induces apoptosis in vitro. In a murine B16F1 melanoma flank tumor model, we demonstrate the acceleration of tumor growth by treatment with N88, whereas C107 significantly slowed tumor growth whether administered before (P<0.005) or after (P<0.05) tumor implantation.
authors.affiliation: Department of Pathology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Gustaaf G
authors.initials: GG
authors.lastname: de Ridder
authors.forename: Rupa
authors.initials: R
authors.lastname: Ray
authors.forename: Salvatore V
authors.initials: SV
authors.lastname: Pizzo
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000494:pharmacology*; D000915:Antibody Affinity; D000918:Antibody Specificity; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D000091342:Endoplasmic Reticulum Chaperone BiP; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D000939:Epitopes; D005260:Female; D005434:Flow Cytometry; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D006825:Hybridomas; D008546:Melanoma, Experimental / Q000188:drug therapy* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D047368:Tumor Burden
chemical_list: D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D000091342:Endoplasmic Reticulum Chaperone BiP; D000939:Epitopes; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D058539:Phosphatidylinositol 3-Kinase; D051057:Proto-Oncogene Proteins c-akt