Ibrutinib inhibits CD20 upregulation on CLL B cells mediated by the CXCR4/SDF-1 axis

Area of Science:

• Oncology
• Immunology
• Molecular Biology

Background:

• Agents targeting Bruton tyrosine kinase (BTK) and phosphatidylinositol 3-kinase can mobilize neoplastic B cells.
• This mobilization is key for combining kinase inhibitors with anti-CD20 monoclonal antibodies for B-cell lymphomas and chronic lymphocytic leukemia (CLL).
• Understanding CD20 expression regulation in CLL is crucial for optimizing these combination therapies.

Purpose of the Study:

• To investigate the mechanisms regulating CD20 expression on CLL cells in the context of microenvironmental interactions.
• To determine the effect of Bruton tyrosine kinase (BTK) inhibitors on CD20 expression in CLL.
• To explore the role of chemokine signaling in modulating CD20 levels on CLL cells.

Main Methods:

• Co-culture of CLL cells with HS-5 stromal cells.
• Administration of ibrutinib (BTK inhibitor) and plerixafor (CXCR4 inhibitor) in vivo and in vitro.
• Flow cytometry analysis to assess CD20, CXCR4, and CD5 expression.
• Measurement of Mcl1 levels in CLL cells.

Main Results:

• Interactions between CLL cells and stromal cells upregulate CD20 expression.
• Ibrutinib downmodulates CD20 expression on CLL cells in vivo.
• Stromal cell-derived factor 1α (SDF-1α, CXCL12) upregulates CD20 expression, an effect blocked by ibrutinib and plerixafor.
• CLL cells recently emigrated from lymph nodes (CXCR4(dim)CD5(bright)) exhibit higher CD20 levels than those longer in circulation (CXCR4(bright)CD5(dim)).
• Ibrutinib also downmodulated Mcl1 levels in CLL cells.

Conclusions:

• Stromal cell interactions and chemokine signaling (SDF-1α) directly regulate CD20 expression on CLL cells.
• BTK inhibition by ibrutinib downmodulates CD20 and Mcl1 expression.
• These findings provide mechanistic insights into CD20 regulation and have implications for microenvironment-targeting therapies in CLL and B-cell lymphomas.