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 October 2, 2018
Citation Information: J Clin Invest. 2018;128(12):5465-5478. https://doi.org/10.1172/JCI96610.
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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 1

CD84 regulates PD-L1 expression on human and murine CLL cells and cells in their microenvironment.

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CD84 regulates PD-L1 expression on human and murine CLL cells and cells ...
(A and B) CLL cells derived from patients (at different stages of disease: n = 3 Binet A, n = 1 Binet B, n = 1 Rai II, n = 1 Binet C, and n = 1 Rai III) (A) or from Eμ-TCL1 CLL mice (B) were stimulated with anti-CD84 or control IgG (5 μg/ml) antibodies, and PD-L1 mRNA and protein levels were determined by qRT-PCR and flow cytometry, respectively. *P < 0.05, 1-tailed, paired t test (A, right), 2-tailed, paired t test (A, left, and B). n = 3 (A) and n = 4 (B). Representative histograms are shown. (C and D) BM stromal cells derived from human CLL samples (n = 4) and healthy patients (n = 4) (C), or Eμ-TCL1 (n = 5) and healthy (n = 5) mice (D) were analyzed by FACS for PD-L1 expression levels. Representative histograms are shown. IgG is shown in white and anti-CD84 in gray. *P < 0.05, 2-tailed, paired t test (C and D). (E) M210B4 stromal cells were stimulated with IgG or anti-CD84 (4 μg/ml) antibody for 24 or 48 hours. PD-L1 mRNA levels were analyzed by qRT-PCR (n = 5), and protein levels were analyzed by flow cytometry (n = 6). *P < 0.05, 2-tailed, paired t test and **P < 0.01, 1 tailed, paired t test. (F–H) BM stromal cells derived from healthy volunteers or CLL patients (F and G) or human NLCs (H) were stimulated with 4 μg/ml anti-CD84 or control antibodies for 24 hours for mRNA expression or 48 hours for protein expression. PD-L1 mRNA levels were analyzed by qRT-PCR using PSMB as a housekeeping control gene (n = 3), and protein levels were determined by flow cytometry (n = 2). *P < 0.05 and **P < 0.01, 1-way ANOVA with Holm-Sidak–corrected multiple comparisons (F) and 2-tailed, paired t test (H). (I–K) Eμ-TCL1 splenocytes were seeded on near-confluent WT or CD84–/– stroma. Forty-eight hours later, protein levels of CD84 and PD-L1 were measured on TCL1 (gated on CD5+CD19+) cells (I and J) and on stroma before and after addition of TCL1 cells (K). n = 3–4 TCL1 mice. *P < 0.05 and **P < 0.01, 2-tailed, paired t test.