Arthur, R, Wathen, A, Lemm, EA, Stevenson, FK, Forconi, F, Linley, AJ, Steele, AJ, Packham, G and Valle-Argos, B (2022) BTK-independent regulation of calcium signalling downstream of the B-cell receptor in malignant B-cells. Cellular Signalling, 96. ISSN 0898-6568

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Abstract

BTK inhibitors (BTKi) have dramatically improved outcomes for patients with chronic lymphocytic leukaemia (CLL) and some forms of B-cell lymphoma. However, new strategies are needed to enhance responses. Here we have performed a detailed analysis of the effects of BTKi on B-cell receptor (BCR)-induced signalling using primary malignant cells from CLL patients and B-lymphoma cell lines. Although BTK is considered as a key activator of PLCγ2, BTKi (ibrutinib and acalabrutinib) failed to fully inhibit calcium responses in CLL samples with strong BCR signalling capacity. This BTKi-resistant calcium signalling was sufficient to engage downstream calcium-dependent transcription and suppress CLL cell apoptosis and was entirely independent of BTK and not just its kinase activity as similar results were obtained using a BTK-degrading PROTAC. BTK-independent calcium signalling was also observed in two B-lymphoma cell lines where BTKi had little effect on the initial phase of the calcium response but did accelerate the subsequent decline in intracellular calcium. In contrast to BTKi, calcium responses were completely blocked by inhibition of SYK in CLL and lymphoma cells. Engagement of BTK-independent calcium responses was associated with BTK-independent phosphorylation of PLCγ2 on Y⁷⁵³ and Y⁷⁵⁹ in both CLL and lymphoma cells. Moreover, in CLL samples, inhibition of RAC, which can mediate BTK-independent activation of PLCγ2, cooperated with ibrutinib to suppress calcium responses. BTK-independent calcium signalling may limit the effectiveness of BTKi to suppress BCR signalling responses and our results suggest inhibition of SYK or dual inhibition of BTK and RAC as alternative strategies to strengthen pathway blockade.

Item Type:	Article
Additional Information:	Rachael Arthur, Alexander Wathen, Elizabeth A. Lemm, Freda K. Stevenson, Francesco Forconi, Adam J. Linley, Andrew J. Steele, Graham Packham, Beatriz Valle-Argos, BTK-independent regulation of calcium signalling downstream of the B-cell receptor in malignant B-cells, Cellular Signalling,Volume 96, 2022,110358, ISSN 0898-6568, https://doi.org/10.1016/j.cellsig.2022.110358.
Uncontrolled Keywords:	Humans; Calcium; Pyrazoles; Pyrimidines; Receptors, Antigen, B-Cell; Protein Kinase Inhibitors; Drug Resistance, Neoplasm; Phospholipase C gamma; Leukemia, Lymphocytic, Chronic, B-Cell; Agammaglobulinaemia Tyrosine Kinase; B-cell receptor; BTK; Calcium; Chronic lymphocytic leukaemia; Lymphoma; Agammaglobulinaemia Tyrosine Kinase; Calcium; Drug Resistance, Neoplasm; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Phospholipase C gamma; Protein Kinase Inhibitors; Pyrazoles; Pyrimidines; Receptors, Antigen, B-Cell; 0601 Biochemistry and Cell Biology; 1116 Medical Physiology; Biochemistry & Molecular Biology
Subjects:	R Medicine > RC Internal medicine > RC0254 Neoplasms. Tumors. Oncology (including Cancer) R Medicine > RS Pharmacy and materia medica
Divisions:	Pharmacy & Biomolecular Sciences
Publisher:	Elsevier
SWORD Depositor:	A Symplectic
Date Deposited:	19 Sep 2023 08:55
Last Modified:	09 Oct 2023 16:13
DOI or ID number:	10.1016/j.cellsig.2022.110358
URI:	https://researchonline.ljmu.ac.uk/id/eprint/20309

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