CD84 regulates PD-1/PD-L1 expression and function in chronic lymphocytic leukemia
Hadas Lewinsky, … , Shirly Becker-Herman, Idit Shachar
Hadas Lewinsky, … , Shirly Becker-Herman, Idit Shachar
Published December 3, 2018; First published October 2, 2018
Citation Information: J Clin Invest. 2018;128(12):5465-5478. https://doi.org/10.1172/JCI96610.
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Research Article Immunology Oncology

CD84 regulates PD-1/PD-L1 expression and function in chronic lymphocytic leukemia

Abstract

Chronic lymphocytic leukemia (CLL) is characterized by clonal proliferation and progressive accumulation of mature B lymphocytes in the peripheral blood, lymphoid tissues, and bone marrow. CLL is characterized by profound immune defects leading to severe infectious complications. T cells are numerically, phenotypically, and functionally highly abnormal in CLL, with only limited ability to exert antitumor immune responses. Exhaustion of T cells has also been suggested to play an important role in antitumor responses. CLL-mediated T cell exhaustion is achieved by the aberrant expression of several inhibitory molecules on CLL cells and their microenvironment, prominently the programmed cell death ligand 1/programmed cell death 1 (PD-L1/PD-1) receptors. Previously, we showed that CD84, a member of the SLAM family of receptors, bridges between CLL cells and their microenvironment. In the current study, we followed CD84 regulation of T cell function. We showed that cell-cell interaction mediated through human and mouse CD84 upregulates PD-L1 expression on CLL cells and in their microenvironment and PD-1 expression on T cells. This resulted in suppression of T cell responses and activity in vitro and in vivo. Thus, our results demonstrate a role for CD84 in the regulation of immune checkpoints by leukemia cells and identify CD84 blockade as a therapeutic strategy to reverse tumor-induced immune suppression.

Authors

Hadas Lewinsky, Avital F. Barak, Victoria Huber, Matthias P. Kramer, Lihi Radomir, Lital Sever, Irit Orr, Vita Mirkin, Nili Dezorella, Mika Shapiro, Yosef Cohen, Lev Shvidel, Martina Seiffert, Yair Herishanu, Shirly Becker-Herman, Idit Shachar

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Figure 2

Activation of cell-surface CD84 elevates PD-L1 levels through the p-AKT/mTOR pathway.

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Activation of cell-surface CD84 elevates PD-L1 levels through the p-AKT/...
(A and B) M210B4 cells (1 × 105) were stimulated with anti-CD84 (4 μg/ml) for 15 minutes, followed by anti-FAB cross-linking for 5 minutes. (A) Cells were lysed, and lysates were separated on 12% (wt/vol) SDS-PAGE and blotted with anti–p-S6, anti–p-AKT, anti–p-ERK, or actin. Blots are representative of 3 independent experiments. (B) Cells were fixed, permeabilized, and subsequently stained with anti–p-AKT and anti–p-S6 antibodies followed by a secondary anti-rabbit allophycocyanin-conjugated (APC-conjugated) antibody. Histograms are representative of 2 independent experiments. (C–E) Primary CLL cells were stimulated with control (IgG) or anti-CD84–activating (5 μg/ml) antibodies for 5 minutes, followed by anti-FAB cross-linking for an additional 5 minutes. Then, the cells were fixed, and p-ERK, p-AKT, and p-S6 levels were analyzed by flow cytometry (n = 3; *P < 0.05 and **P < 0.01, 2-tailed, paired t test). (F and G) CLL cells were incubated with the inhibitors wortmannin and rapamycin (0.1 μM) for 20 minutes. The cells were then stimulated with anti-CD84–activating (5 μg/ml) antibodies, or IgG control. After 48 hours, the cells were analyzed by FACS for PD-L1 cell-surface expression (n = 4; *P < 0.05, 2-tailed, paired t test). (H and I) CLL cells were stimulated with IgG or anti-CD84–activating (5 μg/ml) antibodies for 0, 15, and 30 minutes, followed by anti-FAB cross-linking for 0, 15, and 30 minutes. Cells were then fixed, permeabilized, and stained with IkBα (n = 2) (H), or p-STAT3 (n = 4) (I) antibodies. *P < 0.05, 2-tailed, paired t test.