title: Identification of an alternative CD20 transcript variant in B-cell malignancies coding for a novel protein associated to rituximab resistance.
abstract: Human CD20 is a B-cell lineage-specific marker expressed by normal and leukemic B cells from the pre-B to the plasma-cell stages and is a target for rituximab (RTX) immunotherapy. A CD20 reverse transcriptase-polymerase chain reaction (PCR) on B-cell lines cDNA yielded a short PCR product (DeltaCD20) corresponding to a spliced mRNA transcript linking the exon 3 and exon 7 ends. We established here that this novel, alternatively spliced CD20 transcript is expressed and detectable at various levels in leukemic B cells, lymphoma B cells, in vivo tonsil- or in vitro CD40L-activated B cells, and Epstein-Barr virus (EBV)-transformed B cells, but not in resting CD19(+)- or CD20(+)-sorted B cells from peripheral blood or bone marrow of healthy donors. The truncated CD20 sequence is within the reading frame, codes a protein of 130 amino acids ( approximately 15-17 kDa) lacking large parts of the 4 transmembrane segments, suggesting that DeltaCD20 is a nonanchored membrane protein. We demonstrated the translation into a DeltaCD20 protein which is associated with the membrane CD20 protein and showed its involvement in RTX resistance. Study of patient samples before and after RTX resistance or escape confirms our in vitro findings.
authors.affiliation: Inserm, Unite Mixte de Recherche (UMR) 645, 25020 Besançon, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Henry
authors.forename: Marina
authors.initials: M
authors.lastname: Deschamps
authors.forename: Pierre-Simon
authors.initials: PS
authors.lastname: Rohrlich
authors.forename: Jean-René
authors.initials: JR
authors.lastname: Pallandre
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Rémy-Martin
authors.forename: Mary
authors.initials: M
authors.lastname: Callanan
authors.forename: Alexandra
authors.initials: A
authors.lastname: Traverse-Glehen
authors.forename: Camille
authors.initials: C
authors.lastname: GrandClément
authors.forename: Francine
authors.initials: F
authors.lastname: Garnache-Ottou
authors.forename: Remy
authors.initials: R
authors.lastname: Gressin
authors.forename: Eric
authors.initials: E
authors.lastname: Deconinck
authors.forename: Gilles
authors.initials: G
authors.lastname: Salles
authors.forename: Eric
authors.initials: E
authors.lastname: Robinet
authors.forename: Pierre
authors.initials: P
authors.lastname: Tiberghien
authors.forename: Christophe
authors.initials: C
authors.lastname: Borg
authors.forename: Christophe
authors.initials: C
authors.lastname: Ferrand
mesh_terms: D017398:Alternative Splicing / Q000502:physiology; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D058846:Antibodies, Monoclonal, Murine-Derived; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001402:B-Lymphocytes / Q000166:cytology / Q000502:physiology; D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D015153:Blotting, Western; D002451:Cell Compartmentation; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D006801:Humans; D015448:Leukemia, B-Cell / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D018365:Neoplasm, Residual / Q000235:genetics / Q000473:pathology; D014066:Palatine Tonsil / Q000166:cytology; D012333:RNA, Messenger / Q000235:genetics; D000069283:Rituximab
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; C424714:MS4A4A protein, human; D008565:Membrane Proteins; D012333:RNA, Messenger; D000069283:Rituximab