Identification of an alternative CD20 transcript variant in B-cell malignancies coding for a novel protein associated to rituximab resistance.
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.
Henry
Carole
C
Inserm, Unite Mixte de Recherche (UMR) 645, 25020 Besançon, France.
Deschamps
Marina
M
Rohrlich
Pierre-Simon
PS
Pallandre
Jean-René
JR
Rémy-Martin
Jean-Paul
JP
Callanan
Mary
M
Traverse-Glehen
Alexandra
A
GrandClément
Camille
C
Garnache-Ottou
Francine
F
Gressin
Remy
R
Deconinck
Eric
E
Salles
Gilles
G
Robinet
Eric
E
Tiberghien
Pierre
P
Borg
Christophe
C
Ferrand
Christophe
C
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
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