title: Enhanced cytotoxicity of rituximab following genetic and biochemical disruption of glycosylphosphatidylinositol anchored proteins.
abstract: Rituximab, an anti-CD20 monoclonal antibody used to treat B cell lymphoproliferative disorders and autoimmune diseases, kills cells through complement dependent cytotoxicity, antibody-dependent cellular toxicity and apoptosis. A mechanism of resistance to rituximab is upregulation of the complement regulatory proteins, CD59 and CD55. Paroxysmal nocturnal hemoglobinuria (PNH) is a hematopoietic disorder caused by PIGA mutations that lead to a loss of all glycosylphospatidylinositol (GPI)-anchored proteins including, CD55 and CD59. We compared the cytotoxic activity of rituximab against a PNH B cell line, LD -, and the isogenic cell line LD - PIGA + in which GPI-anchor expression was restored by stable transfection of PIGA. The PNH cell line was more sensitive to rituximab-mediated killing than the LD - PIGA + cells. Biochemical disruption of GPI anchors with phosphatidylinositol specific phospholipase C (PIPLC), a phospholipase that cleaves GPI-anchored proteins, also increased rituximab-mediated killing. Thus, genetic and biochemical interruption of GPI anchor proteins augments sensitivity to rituximab.
authors.affiliation: Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD 21231-1000, USA.
authors.forename: Nagaprasad
authors.initials: N
authors.lastname: Nagajothi
authors.forename: William H
authors.initials: WH
authors.lastname: Matsui
authors.forename: Galina L
authors.initials: GL
authors.lastname: Mukhina
authors.forename: Robert A
authors.initials: RA
authors.lastname: Brodsky
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D000970:Antineoplastic Agents / Q000494:pharmacology; D018958:CD55 Antigens; D018957:CD59 Antigens; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D017261:Glycosylphosphatidylinositols / Q000235:genetics / Q000502:physiology*; D006457:Hemoglobinuria, Paroxysmal / Q000188:drug therapy / Q000473:pathology; D006801:Humans; D000069283:Rituximab; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D000970:Antineoplastic Agents; D018958:CD55 Antigens; D018957:CD59 Antigens; D017261:Glycosylphosphatidylinositols; D000069283:Rituximab