American Association for Cancer Research
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Supplementary Tables from Decreased NOTCH1 Activation Correlates with Response to Ibrutinib in Chronic Lymphocytic Leukemia

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posted on 2023-03-31, 21:03 authored by Beatrice Del Papa, Stefano Baldoni, Erica Dorillo, Filomena De Falco, Chiara Rompietti, Debora Cecchini, Maria Grazia Cantelmi, Daniele Sorcini, Manuel Nogarotto, Francesco Maria Adamo, Federica Mezzasoma, Estevão Carlos Silva Barcelos, Elisa Albi, Roberta Iacucci Ostini, Ambra Di Tommaso, Andrea Marra, Guido Montanaro, Maria Paola Martelli, Franca Falzetti, Mauro Di Ianni, Emanuela Rosati, Paolo Sportoletti

Tables S1-4

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Assumption University of Thailand

Ministry of Education, University and Research

CAPES

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ARTICLE ABSTRACT

Ibrutinib, a Bruton tyrosine kinase inhibitor (BTKi), has improved the outcomes of chronic lymphocytic leukemia (CLL), but primary resistance or relapse are issues of increasing significance. While the predominant mechanism of action of BTKi is the B-cell receptor (BCR) blockade, many off-target effects are unknown. We investigated potential interactions between BCR pathway and NOTCH1 activity in ibrutinib-treated CLL to identify new mechanisms of therapy resistance and markers to monitor disease response. NOTCH activations was evaluated either in vitro and ex vivo in CLL samples after ibrutinib treatment by Western blotting. Confocal proximity ligation assay (PLA) experiments and analyses of down-targets of NOTCH1 by qRT-PCR were used to investigate the cross-talk between BTK and NOTCH1. In vitro ibrutinib treatment of CLL significantly reduced activated NOTCH1/2 and induced dephosphorylation of eIF4E, a NOTCH target in CLL. BCR stimulation increased the expression of activated NOTCH1 that accumulated in the nucleus leading to HES1, DTX1, and c-MYC transcription. Results of in situ PLA experiments revealed the presence of NOTCH1-ICD/BTK complexes, whose number was reduced after ibrutinib treatment. In ibrutinib-treated CLL patients, leukemic cells showed NOTCH1 activity downregulation that deepened over time. The NOTCH1 signaling was restored at relapse and remained activated in ibrutinib-resistant CLL cells. We demonstrated a strong clinical activity of ibrutinib in a real-life context. The ibrutinib clinical efficacy was associated with NOTCH1 activity downregulation that deepened over time. Our data point to NOTCH1 as a new molecular partner in BCR signaling with potential to further improve CLL-targeted treatments.

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