Human CAR T cells with cell-intrinsic PD-1 checkpoint blockade resist tumor-mediated inhibition
Leonid Cherkassky, … , Michel Sadelain, Prasad S. Adusumilli
Leonid Cherkassky, … , Michel Sadelain, Prasad S. Adusumilli
Published July 25, 2016
Citation Information: J Clin Invest. 2016;126(8):3130-3144. https://doi.org/10.1172/JCI83092.
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Research Article Oncology

Human CAR T cells with cell-intrinsic PD-1 checkpoint blockade resist tumor-mediated inhibition

Abstract

Following immune attack, solid tumors upregulate coinhibitory ligands that bind to inhibitory receptors on T cells. This adaptive resistance compromises the efficacy of chimeric antigen receptor (CAR) T cell therapies, which redirect T cells to solid tumors. Here, we investigated whether programmed death-1–mediated (PD-1–mediated) T cell exhaustion affects mesothelin-targeted CAR T cells and explored cell-intrinsic strategies to overcome inhibition of CAR T cells. Using an orthotopic mouse model of pleural mesothelioma, we determined that relatively high doses of both CD28- and 4-1BB–based second-generation CAR T cells achieved tumor eradication. CAR-mediated CD28 and 4-1BB costimulation resulted in similar levels of T cell persistence in animals treated with low T cell doses; however, PD-1 upregulation within the tumor microenvironment inhibited T cell function. At lower doses, 4-1BB CAR T cells retained their cytotoxic and cytokine secretion functions longer than CD28 CAR T cells. The prolonged function of 4-1BB CAR T cells correlated with improved survival. PD-1/PD-1 ligand [PD-L1] pathway interference, through PD-1 antibody checkpoint blockade, cell-intrinsic PD-1 shRNA blockade, or a PD-1 dominant negative receptor, restored the effector function of CD28 CAR T cells. These findings provide mechanistic insights into human CAR T cell exhaustion in solid tumors and suggest that PD-1/PD-L1 blockade may be an effective strategy for improving the potency of CAR T cell therapies.

Authors

Leonid Cherkassky, Aurore Morello, Jonathan Villena-Vargas, Yang Feng, Dimiter S. Dimitrov, David R. Jones, Michel Sadelain, Prasad S. Adusumilli

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Figure 2

Mice treated with M28z and MBBz CAR T cells demonstrate tumor eradication at a higher dose, whereas treatment with lower doses results in higher rate of tumor relapse with M28z.

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Mice treated with M28z and MBBz CAR T cells demonstrate tumor eradicatio...
(A) In vivo BLI was used to monitor tumor burden (ffLuc+MSLN+) in NOD/SCID/γcnull mice. Mice with established pleural tumor were treated with a single dose of 1 × 105 (E:T 1:3,000), 8 × 104 (E:T1:3,750), or 5 × 104 (E:T 1:6,000) M28z or MBBz CAR T cells. Daggers indicate the deaths of mice. For A and B, 2 similar experiments with the same donor are combined for the illustration. n = 7–9 mice for each group treated with MSLN-targeted CAR T cells. (B) Mice were treated with 4 × 104 CAR T cells (E:T 1:7,500). The first generation Mz CAR and negative control P28z are included. (C) Kaplan-Meier survival analysis comparing the in vivo efficacy of intrapleural administration of 4 × 104 Mz (n = 13, red), M28z (n = 15, blue), MBBz (n = 8, green), and P28z (n = 3, black) CAR T cells. Two independent experiments performed under similar conditions were combined. Median survival in days following T cell administration. The survival curve was analyzed using the log-rank test. *P < 0.05; **P < 0.01. All data are representative of multiple experiments performed with multiple donors.