<p>Supplementary Figure S1. Ibrutinib alters the absolute expression of inflammatory cytokines and chemokines in serum from patients with CLL. Supplementary Figure S2. Ibrutinib treatment reduces tumor burden. Supplementary Figure S3. Both CD4+ and CD8+ T cell subsets are decreased on ibrutinib. Supplementary Figure S4. Grading of macrophage interaction with CLL cells in bone marrow specimens. Supplementary Figure S5. Ibrutinib alters the absolute expression of chemokines in bone marrow supernatant from patients with CLL.</p>
ARTICLE ABSTRACT
Purpose: Chronic lymphocytic leukemia (CLL) cells depend on microenvironmental interactions for proliferation and survival that are at least partially mediated through B-cell receptor (BCR) signaling. Ibrutinib, a Bruton tyrosine kinase inhibitor, disrupts BCR signaling and leads to the egress of tumor cells from the microenvironment. Although the on-target effects on CLL cells are well defined, the impact on the microenvironment is less well studied. We therefore sought to characterize the in vivo effects of ibrutinib on the tumor microenvironment.Experimental Design: Patients received single-agent ibrutinib on an investigator-initiated phase II trial. Serial blood and tissue samples were collected pretreatment and during treatment. Changes in cytokine levels, cellular subsets, and microenvironmental interactions were assessed.Results: Serum levels of key chemokines and inflammatory cytokines decreased significantly in patients on ibrutinib. Furthermore, ibrutinib treatment decreased circulating tumor cells and overall T-cell numbers. Most notably, a reduced frequency of the Th17 subset of CD4+ T cells was observed concurrent with reduced expression of activation markers and PD-1 on T cells. Consistent with direct inhibition of T cells, ibrutinib inhibited Th17 differentiation of murine CD4+ T cells in vitro. Finally, in the bone marrow microenvironment, we found that ibrutinib disaggregated the interactions of macrophages and CLL cells, inhibited secretion of CXCL13, and decreased the chemoattraction of CLL cells.Conclusions: In conjunction with inhibition of BCR signaling, these changes in the tumor microenvironment likely contribute to the antitumor activity of ibrutinib and may impact the efficacy of immunotherapeutic strategies in patients with CLL. Clin Cancer Res; 22(7); 1572–82. ©2015 AACR.See related commentary by Bachireddy and Wu, p. 1547
