Paradoxical activation of chronic lymphocytic leukemia cells by ruxolitinib in vitro and in vivo

David E Spaner; Tina YuXuan Luo; Guizhi Wang; Gideon Schreiber; Daniel Harari; Yonghong Shi

doi:10.3389/fonc.2023.1043694

Paradoxical activation of chronic lymphocytic leukemia cells by ruxolitinib in vitro and in vivo

Front Oncol. 2023 Apr 11:13:1043694. doi: 10.3389/fonc.2023.1043694. eCollection 2023.

Authors

David E Spaner^{1

2

3

4

5}, Tina YuXuan Luo^{1

2}, Guizhi Wang¹, Gideon Schreiber⁶, Daniel Harari⁶, Yonghong Shi¹

Affiliations

¹ Biology Platform, Sunnybrook Research Institute, Toronto, ON, Canada.
² Department of Immunology, University of Toronto, Toronto, ON, Canada.
³ Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada.
⁴ Department of Hematology, Sunnybrook Odette Cancer Center, Toronto, ON, Canada.
⁵ Department of Medicine, University of Toronto, Toronto, ON, Canada.
⁶ Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel.

Abstract

Introduction: Chronic lymphocytic leukemia (CLL) is characterized by an aberrant cytokine network that can support tumor growth by triggering janus kinase (JAK)/STAT pathways. Targeting cytokine-signaling should then be a rational therapeutic strategy but the JAK inhibitor ruxolitinib failed to control and seemingly accelerated the disease in clinical trials.

Methods: The effect of ruxolitinib on primary human CLL cells was studied in vitro and in vivo.

Results: Ruxolitinib increased phosphorylation of IRAK4, an important toll-like receptor (TLR)- signaling intermediate, in circulating CLL cells in vitro. It also enhanced p38 and NFKB1 phosphorylation while lowering STAT3 phosphorylation in CLL cells activated with TLR-7/8 agonists and IL-2. Among the cytokines made by activated CLL cells, high levels of IL-10 contributed strongly to STAT3 phosphorylation and inhibited TLR7 activity. Ruxolitinib limited TLR-mediated IL10 transcription and markedly reduced IL-10 production in vitro. It also decreased blood levels of IL-10 while increasing TNFα along with phospho-p38 expression and gene sets associated with TLR-activation in CLL cells in vivo. The bruton's tyrosine kinase inhibitor ibrutinib decreased IL-10 production in vitro but, in contrast to ruxolitinib, blocked initial IL10 transcription induced by TLR-signaling in vitro, decreased TNFα production, and deactivates CLL cells in vivo.

Discussion: These findings suggest the possible benefits of inhibiting growth factors with JAK inhibitors in CLL are outweighed by negative effects on potential tumor suppressors such as IL-10 that allow unrestrained activation of NFκB by drivers such as TLRs. Specific inhibition of growth-promoting cytokines with blocking antibodies or infusing suppressive cytokines like IL-10 might be better strategies to manipulate cytokines in CLL.

Keywords: Chronic lymphocytic leukemia; IL-10; cancer microenvironment; cytokines; ibrutinib; janus kinases; ruxolitinib; toll-like receptors.

Grants and funding

This work was supported by grants from the Leukemia and Lymphoma Society of Canada (LLSC), CIHR (#153291), IDRC (108594-001), and Novartis Canada.