Effects Of Bruton's Tyrosine Kinase Inhibitors Research Articles

The Immunomodulatory Mechanisms of BTK Inhibition in CLL and Beyond.

Bruton's tyrosine kinase (BTK), a cytoplasmic tyrosine kinase, plays a pivotal role in B cell biology and function. As an essential component of the B cell receptor (BCR) signaling pathway, BTK is expressed not only in B cells but also in myeloid cells, including monocytes/macrophages, dendritic cells, neutrophils, and mast cells. BTK inhibitors (BTKis) have revolutionized the treatment of chronic lymphocytic leukemia (CLL) and other B cell malignancies. Besides their well-characterized role in inhibiting BCR signaling, BTKis also exert significant immunological influences outside the tumor cell that extend their therapeutic potential and impact on the immune system in different ways. This work elucidates the immunomodulatory mechanisms associated with BTK inhibition, focusing on CLL and other clinical contexts. We discuss how BTK inhibition affects various immune cells, including B cells, T cells, and macrophages. The effects of BTKis on the profiles of cytokines, also fundamental parts of the tumor microenvironment (TME), are summarized here as well. This review also appraises the implications of these immunomodulatory actions in the management of autoimmune diseases and infections. Summarizing the dual role of BTK inhibition in modulating malignant lymphocyte and immune cell functions, this paper highlights the broader potential clinical use of compounds targeting BTK.

Abstract 6093: Mavorixafor enhances efficacy of Bruton tyrosine kinase inhibitors by overcoming the protective effect of bone marrow stroma on tumor cells in Waldenström’s macroglobulinemia

Abstract Waldenström’s macroglobulinemia (WM) is a rare B-cell malignancy characterized by monoclonal immunoglobulin M (IgM) hypersecretion and invasion of B cells in the bone marrow (BM) and lymphoid tissues. >90% of WM cases show mutations in MYD88 and 30-40% show mutations in the carboxyl terminus of CXCR4.The CXCR4/CXCL12 axis is crucial for the homing/retention of WM cells in the BM. Emerging clinical trial data (NCT04274738; ongoing) suggest that mavorixafor, a CXCR4 antagonist, in combination with ibrutinib results in clinically meaningful changes in levels of IgM and hemoglobin in patients with MYD88L265P CXCR4WHIM WM. However, the effects of mavorixafor with ibrutinib and other Bruton tyrosine kinase (BTK) inhibitors on WM cells harboring only the single mutation (MYD88L265P without CXCR4 mutation) have not been evaluated. This study was designed to test the ability of mavorixafor to sensitize WM cells carrying MYD88L265P CXCR4WT to BTK inhibitors in a WM/BM stromal cell (BMSC) co-culture model. The effects of mavorixafor on Ca2+ mobilization, cell migration, and adhesion to BMSC were also measured. WM cells (MWCL-1 cell line, MYD88L265PCXCR4WT) pretreated with mavorixafor and BTK inhibitors (ibrutinib, zanubrutinib, evobrutinib, LOXO-305, ARQ 531) were co-cultured with established BMSCs (HS27a cells). Cell viability, apoptosis, and IgM release were measured after 72 hours. BTK inhibitors, but not mavorixafor, decreased tumor cell viability and increased apoptosis of WM cells in the absence of BMSCs. Co-culture with BMSCs enhanced CXCR4 expression and protected WM cells from the effects of BTK inhibitors. BMSCs also significantly increased IgM secretion 2- to 5-fold compared with WM cells grown in the absence of BMSCs. Mavorixafor alone inhibited CXCL12-stimulated Ca2+ mobilization and migration of WM cells and disrupted the adhesion of WM cells to BMSCs. Combination of mavorixafor with BTK inhibitors overcame the protective effect of BMSCs on tumor cells, decreasing cell viability and/or increasing apoptosis compared with BTK inhibitors alone. Mavorixafor also reduced IgM secretion, which was further decreased when combined with BTK inhibitors.This study is the first to show in vitro that the protection of WM cells against BTK inhibitors conferred by BMSCs can be overcome by inhibition of the CXCR4/CXCL12 axis. The observations and responses to mavorixafor suggest a contribution of CXCR4WT to the pathogenicity of WM cells carrying only the MYD88L265P mutation. Mavorixafor addition enhanced the efficacy of not only ibrutinib but the other BTK inhibitors tested, supporting the greater potential of this combination therapeutic strategy in WM patients with or without CXCR4WHIM mutations. Further studies using additional WM cell lines and/or primary patient cells are warranted to support these findings. Citation Format: Chi Nguyen, Halenya Monticelli, Tom Kruitwagen, Matteo Tardelli, Barbara Maierhofer, Thalia Martins Rebelo, Sabine Maier-Munsa, Katarina Zmajkovicova, Lukas Dillinger, Adriana Badarau, Arthur G. Taveras. Mavorixafor enhances efficacy of Bruton tyrosine kinase inhibitors by overcoming the protective effect of bone marrow stroma on tumor cells in Waldenström’s macroglobulinemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6093.

Abstract 1396: Non-competitive inhibition of proteasome by kinase inhibitors

Abstract Inhibitors of Bruton's Tyrosine Kinase (BTK) and inhibitors of the proteasome are currently in use for treatment of hematologic malignancies. While the ubiquitin proteasome system is necessary for protein homeostasis in all mammalian cells, BTK is unique to some B cell malignancies. However, BTK inhibitors and LU-102, a specific inhibitor of the β2 site of the proteasome, have previously been shown to synergize in hematologic malignancies which do not express BTK, at a 100-fold higher concentration than is needed for complete inhibition of BTK, suggesting an off-target effect of these BTK inhibitors. Triple Negative Breast Cancer (TNBC), a cancer with poor prognosis and no current targeted therapy, also does not express BTK. We found that LU-102 and a specific BTK inhibitor, CGI-1764, are de-facto synthetically lethal to TNBC cells, and that effect of other BTK inhibitors varied from similar synergy to no synergy. This data further supports the idea that synergy is due to off-target effects of BTK inhibitors.We have now found that CGI-1764 is a non-competitive, allosteric inhibitor of all catalytic subunits of the proteasome 20S proteolytic core and exerts its effect in a unique, dose-dependent manner. RNA sequencing shows that the Unfolded Protein Response pathway is upregulated in TNBC cells response to treatment with the CGI-1746+LU-102 combination. We also found that accumulation of ubiquitin conjugates is synergistic indicating that the combination treatment has a synergistic effect on the inhibition of proteasome activity. These findings may pave the path to the development of more potent allosteric inhibitors of the proteasome and show that kinase inhibitors should be screened for inhibition of the proteasome as potential off-target effect. Citation Format: Alexei F. Kisselev, Olasubomi Akintola, John Smith. Non-competitive inhibition of proteasome by kinase inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1396.

Bruton's Tyrosine Kinase (BTK) Inhibitor (Ibrutinib)-Suppressed Migration and Invasion of Prostate Cancer.

IntroductionBruton’s tyrosine kinase (BTK) inhibitors have long been known in the treatment of B-cell malignancies. Recently, BTK inhibitors have also become promising novel treatment reagents for prostate cancer. The current study was designed to investigate expression of BTK in prostate cancer tissues in comparison with benign hyperplasia and effect of BTK inhibitor on prostate cancer cell proliferation, migration and invasion.MethodsBTK expression was assessed by immunohistochemistry; migration and invasion prostate cancer cell lines (DU145 and PC3) were assessed by Transwell migration and wound-healing assay; cancer cell proliferation was assessed using MTT assay kit; expression of matrix metalloproteinases-2 and -9 (MMP-2 and MMP-9) was assessed by immunoblotting.ResultsStrong expression of BTK was detected in the prostate cancer tissues, especially in the tumors from prostate cancer patients with bone metastasis. BTK inhibitor (Ibrutinib) significantly inhibited cell proliferation, migration and invasion of prostate cancer cells as well as protein synthesis of MMP-2 and MMP-9 by the tumor cells. Overexpressing BTK could partially but significantly block the inhibitory effect of Ibrutinib on cell proliferation, migration and invasion, and protein synthesis of MMP-2 and MMP-9 of the cancer cells.ConclusionThese findings suggested that BTK could serve as not only a biomarker but also a therapeutic target for the prostate cancer and that Ibrutinib may be applied as a therapeutic drug for the prostate cancer.

Abstract 5496: Effect of BTK inhibitors on differentiation of human monocyte-derived dendritic cells

Abstract Dendritic cells (DCs) are primary antigen-presenting cells (APCs), which process tumor antigen and present it on the cell surface to the T cells of the adaptive immune system. However, immature DCs facilitate tolerance toward cancer cells. Bruton's tyrosine kinase (BTK) is highly expressed in B cells, monocytes, macrophages and dendritic cells and plays crucial roles in differentiation and activation of myeloid cells. Dendritic cells in Btk−/− mice were reported to have more mature phenotype and stronger in vitro and in vivo T cell stimulatory ability than wild-type DCs. However, the functions of BTK in human DC differencation and maturation were not well characterized. In this study, we revealed the effect of BTK inhibition with ibrutinib, an FDA approved drug for chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL), in human monocyte derived dendritic cells (moDCs). We show that BTK was expressed in monocytes and moDCs. BTK activity was regulated during moDCs differencation and BTK inhibitors blocked GM-CSF/IL4 induced activation of BTK. LPS instead of CD40L treatment increased BTK phosphorylation. It was noted that the percentage of CD11c+ MHC IIlow subsets, which represented the immature DCs, was significantly reduced upon ibrutinib treatment during moDC differencation. Meanwhile, ibrutinib dose-dependently increased proportion of CD11c+ MHC IIhigh cells, which represent more mature DCs. We also tested BGB-3111, a more selective BTK inhibitor without ITK, TXK, EGFR, HER2 and JAK3 activity in the same assay. We observed increased MHC II level during differentiation of human moDCs with BGB-3111 treatment. These results support combination strategies for BTK inhibitors with other cancer immunotherapy agents. Citation Format: Zhijian Sun, Dongping Zhou, Lusong Luo. Effect of BTK inhibitors on differentiation of human monocyte-derived dendritic cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5496. doi:10.1158/1538-7445.AM2015-5496