title: P-selectin glycoprotein ligand-1 as a potential target for humoral immunotherapy of multiple myeloma.
abstract: Monoclonal antibodies (mAbs), successfully adopted in the treatment of several haematological malignancies, have proved almost ineffective in multiple myeloma (MM), because of the lack of an appropriate antigen for targeting and killing MM cells. Here, we demonstrate that PSGL1, the major ligand of P-Selectin, a marker of plasmacytic differentiation expressed at high levels on normal and neoplastic plasma cells, may represent a novel target for mAb-mediated MM immunotherapy. The primary effectors of mAb-induced cell-death, complement-mediated lysis (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC), were investigated using U266B1 and LP1 cell-lines as models. Along with immunological mechanisms, the induction of apoptosis by PSGL1 cross-linking was assessed. The anti-PSGL1 murine mAb KPL1 induced death of MM cells in a dose- and time-dependent fashion and mediated a significant amount of ADCC. KPL1 alone mediated C1q deposition on target cells but proved unable to induce CDC due to inhibition of the lytic activity of complement by membrane complement regulators (mCRP) expressed on the cell surface. Consistently, CDC was induced by KPL1 upon mCRP blockage. Our results suggest a role for PSGL1 in MM humoral immunotherapy and support further in vivo studies assessing the effects of anti-PSGL1 mAbs on MM growth and interaction with the bone marrow microenvironment.
authors.affiliation: Dipartimento di Patologia Umana, Università degli Studi di Palermo, 90127, Palermo, Italy. tripodo@unipa.it
authors.forename: C
authors.initials: C
authors.lastname: Tripodo
authors.forename: A M
authors.initials: AM
authors.lastname: Florena
authors.forename: P
authors.initials: P
authors.lastname: Macor
authors.forename: A
authors.initials: A
authors.lastname: Di Bernardo
authors.forename: R
authors.initials: R
authors.lastname: Porcasi
authors.forename: C
authors.initials: C
authors.lastname: Guarnotta
authors.forename: S
authors.initials: S
authors.lastname: Ingrao
authors.forename: M
authors.initials: M
authors.lastname: Zerilli
authors.forename: E
authors.initials: E
authors.lastname: Secco
authors.forename: M
authors.initials: M
authors.lastname: Todaro
authors.forename: F
authors.initials: F
authors.lastname: Tedesco
authors.forename: Vito
authors.initials: V
authors.lastname: Franco
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology / Q000627:therapeutic use*; D000920:Antibody-Dependent Cell Cytotoxicity / Q000187:drug effects / Q000276:immunology; D001854:Bone Marrow Cells / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D003167:Complement Activation / Q000187:drug effects / Q000276:immunology; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D016503:Drug Delivery Systems; D004353:Drug Evaluation, Preclinical; D006801:Humans; D008562:Membrane Glycoproteins / Q000276:immunology* / Q000378:metabolism; D009101:Multiple Myeloma / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000628:therapy*
chemical_list: D000911:Antibodies, Monoclonal; D008562:Membrane Glycoproteins; C084882:P-selectin ligand protein