Survival response to B-cell receptor ligation is restricted to progressive chronic lymphocytic leukemia cells irrespective of Zap70 expression.
Despite very similar gene expression profiles, the clinical course of B-cell chronic lymphocytic leukemia (B-CLL) is heterogeneous. Immunoglobulin VH (IgVH) mutational status and expression of B-cell receptor (BCR) signaling mediators have been associated with disease progression. However, the consequences of BCR engagement on cell survival and evolution of the disease remain unclear. We show here that B-CLL cell survival is dependent on the threshold of BCR stimulation induced by immobilized antibody, in contrast to soluble anti-mu F(ab)'2 antibody, which leads to apoptosis. Measurement of metabolic activity and apoptotic response discriminated two subgroups. "Nonresponders" showed low metabolic activity and unmodified apoptotic response upon BCR stimulation. In contrast, "responders" exhibited increased metabolic activity and inhibition of spontaneous apoptosis. This survival advantage was associated to a BCR-dependent activation profile leading to induction of cyclin D2/cyclin-dependent kinase 4 (cdk4) expression and G1 cell cycle progression. The ability to respond to BCR ligation correlated with an unfavorable clinical course and allowed to define an additional group of patients among IgVH-mutated cases exhibiting a risk of progression. Remarkably, we show that Zap70 expression was neither mandatory nor sufficient to generate downstream survival signals and cyclin D2/cdk4 up-regulation. In conclusion, BCR engagement has a significant effect on B-CLL cell survival, activation, and G1 progression. Furthermore, our results provide new insights in the physiopathology of progressive IgVH-mutated cases.
Deglesne
Pierre-Antoine
PA
Unite Propre de Recherche de l'Enseignement Superieur EA-3406, Hopital Avicenne Université Paris 13 Bobigny, France.
Chevallier
Nathalie
N
Letestu
Rémi
R
Baran-Marszak
Fanny
F
Beitar
Taoufik
T
Salanoubat
Célia
C
Sanhes
Laurence
L
Nataf
Joelle
J
Roger
Claudine
C
Varin-Blank
Nadine
N
Ajchenbaum-Cymbalista
Florence
F
D000888:Antibodies, Anti-Idiotypic / Q000276:immunology; D002470:Cell Survival / Q000502:physiology; D056742:Cyclin D2; D051358:Cyclin-Dependent Kinase 4 / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D018450:Disease Progression; D016193:G1 Phase / Q000502:physiology; D006801:Humans; D007128:Immunoglobulin Fragments / Q000276:immunology; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000201:enzymology* / Q000276:immunology / Q000473:pathology*; D011947:Receptors, Antigen, B-Cell / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction; D051746:ZAP-70 Protein-Tyrosine Kinase / Q000096:biosynthesis*
D000888:Antibodies, Anti-Idiotypic; C080336:CCND2 protein, human; D056742:Cyclin D2; D016213:Cyclins; D007128:Immunoglobulin Fragments; D011947:Receptors, Antigen, B-Cell; C044203:anti-IgM; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; D051358:Cyclin-Dependent Kinase 4