Early reappearance of intraclonal proliferative subpopulations in ibrutinib-resistant chronic lymphocytic leukemia
Author:
Pozzo FedericoORCID, Forestieri Gabriela, Vit Filippo, Ianna Giulia, Tissino ErikaORCID, Bittolo Tamara, Papotti Robel, Gaglio Annalisa, Terzi di Bergamo Lodovico, Steffan Agostino, Polesel JerryORCID, Bulian Pietro, Laureana Roberta, Tafuri Agostino, Chiarenza Annalisa, Di Raimondo Francesco, Olivieri Jacopo, Zaja Francesco, Laurenti Luca, Del Principe Maria Ilaria, Postorino Massimiliano, Del Poeta Giovanni, Bomben RiccardoORCID, Zucchetto Antonella, Rossi Davide, Gattei ValterORCID
Abstract
AbstractThe Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib represents an effective strategy for treatment of chronic lymphocytic leukemia (CLL), nevertheless about 30% of patients eventually undergo disease progression. Here we investigated by flow cytometry the long-term modulation of the CLL CXCR4dim/CD5bright proliferative fraction (PF), its correlation with therapeutic outcome and emergence of ibrutinib resistance. By longitudinal tracking, the PF, initially suppressed by ibrutinib, reappeared upon early disease progression, without association with lymphocyte count or serum beta-2-microglobulin. Somatic mutations of BTK/PLCG2, detected in 57% of progressing cases, were significantly enriched in PF with a 3-fold greater allele frequency than the non-PF fraction, suggesting a BTK/PLCG2-mutated reservoir resident within the proliferative compartments. PF increase was also present in BTK/PLCG2-unmutated cases at progression, indicating that PF evaluation could represent a marker of CLL progression under ibrutinib. Furthermore, we evidence different transcriptomic profiles of PF at progression in cases with or without BTK/PLCG2 mutations, suggestive of a reactivation of B-cell receptor signaling or the emergence of bypass signaling through MYC and/or Toll-Like-Receptor-9. Clinically, longitudinal monitoring of the CXCR4dim/CD5bright PF by flow cytometry may provide a simple tool helping to intercept CLL progression under ibrutinib therapy.
Publisher
Springer Science and Business Media LLC
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