BET bromodomain protein inhibition reverses chimeric antigen receptor extinction and reinvigorates exhausted T cells in chronic lymphocytic leukemia
Weimin Kong, … , Golnaz Vahedi, Joseph A. Fraietta
Weimin Kong, … , Golnaz Vahedi, Joseph A. Fraietta
Published August 16, 2021
Citation Information: J Clin Invest. 2021;131(16):1-16. https://doi.org/10.1172/JCI145459.
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Research Article Immunology Oncology

BET bromodomain protein inhibition reverses chimeric antigen receptor extinction and reinvigorates exhausted T cells in chronic lymphocytic leukemia

Abstract

Chimeric antigen receptor (CAR) T cells have induced remarkable antitumor responses in B cell malignancies. Some patients do not respond because of T cell deficiencies that hamper the expansion, persistence, and effector function of these cells. We used longitudinal immune profiling to identify phenotypic and pharmacodynamic changes in CD19-directed CAR T cells in patients with chronic lymphocytic leukemia (CLL). CAR expression maintenance was also investigated because this can affect response durability. CAR T cell failure was accompanied by preexisting T cell–intrinsic defects or dysfunction acquired after infusion. In a small subset of patients, CAR silencing was observed coincident with leukemia relapse. Using a small molecule inhibitor, we demonstrated that the bromodomain and extra-terminal (BET) family of chromatin adapters plays a role in downregulating CAR expression. BET protein blockade also ameliorated CAR T cell exhaustion as manifested by inhibitory receptor reduction, enhanced metabolic fitness, increased proliferative capacity, and enriched transcriptomic signatures of T cell reinvigoration. BET inhibition decreased levels of the TET2 methylcytosine dioxygenase, and forced expression of the TET2 catalytic domain eliminated the potency-enhancing effects of BET protein targeting in CAR T cells, providing a mechanism linking BET proteins and T cell dysfunction. Thus, modulating BET epigenetic readers may improve the efficacy of cell-based immunotherapies.

Authors

Weimin Kong, Alexander Dimitri, Wenliang Wang, In-Young Jung, Christopher J. Ott, Maria Fasolino, Yan Wang, Irina Kulikovskaya, Minnal Gupta, Todd Yoder, Jamie E. DeNizio, John K. Everett, Erik F. Williams, Jun Xu, John Scholler, Tyler J. Reich, Vijay G. Bhoj, Kathleen M. Haines, Marcela V. Maus, J. Joseph Melenhorst, Regina M. Young, Julie K. Jadlowsky, Katherine T. Marcucci, James E. Bradner, Bruce L. Levine, David L. Porter, Frederic D. Bushman, Rahul M. Kohli, Carl H. June, Megan M. Davis, Simon F. Lacey, Golnaz Vahedi, Joseph A. Fraietta

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Figure 8

Downregulation of TET2 expression by JQ1 treatment contributes to reinvigoration of CAR T cells from patients with CLL.

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Downregulation of TET2 expression by JQ1 treatment contributes to reinvi...
(A) TET2 mRNA reduction in CD19 CAR T cells transduced and expanded in the presence of 150 nM (–)-JQ1 or (+)-JQ1 (n = 8; paired t test). (B) Depiction of the organization of the human (h)TET2 catalytic domain and structures of FLAG-tagged TET2-CS and TET2-HxD with highlighted targets for mutagenesis in red (top left panel). Schematic of the sequential oxidations of 5-mC to 5-hmC and to 5-fC and to 5-caC catalyzed by TET2 is shown (top right panel). Immunoblot of TET2 protein levels in HEK293T cells is depicted. HSP90 was used as a loading control (bottom left panel). Dot blots for 5-mC, 5-hmC, and 5-caC in genomic DNA isolated from the above HEK293T cells transfected with an empty vector, TET2-CS, and TET2-HxD are shown (bottom right panel, blots are representative of 3 independent experiments). (C) OCR, (D) SRC, and (E) MRC of expanded CLL patient CAR T cells transduced with vector alone or TET2-CS and subsequently treated with (–)-JQ1 or (+)-JQ1 for 4 days (n = 3–4; paired t test). (F) Levels of PD-1 expression on CLL patient CD8+ CAR+ T cells transduced with TET2-CS or TET2-HxD (representative histograms, left panel; graphical data summary, right panel; n = 7, paired t test). (G) Frequency of CD8+ PD-1+ CLL patient T cells transduced with vector alone or lentiviral vectors encoding TET2-CS and TET2-HxD followed by treatment with (–)-JQ1 or (+)-JQ1 (n = 6–12, 2-tailed t test). Data are shown as the mean ± SEM. (H) Levels of TNF-α and IL-2 elaborated by CD8+CAR+ T cells transduced with vector alone or TET2-CS and subsequently treated with (–)-JQ1 or (+)-JQ1 and stimulated with irradiated K562CD19 or K562CD19/PD-L1 cells (n = 4, paired t test). *P ≤ 0.05, **P ≤ 0.01, NS, not significant.