ATR kinase inhibitor AZD6738 potentiates CD8+ T cell–dependent antitumor activity following radiation
Frank P. Vendetti, … , Greg M. Delgoffe, Christopher J. Bakkenist
Frank P. Vendetti, … , Greg M. Delgoffe, Christopher J. Bakkenist
Published June 28, 2018
Citation Information: J Clin Invest. 2018;128(9):3926-3940. https://doi.org/10.1172/JCI96519.
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Research Article Immunology Oncology

ATR kinase inhibitor AZD6738 potentiates CD8+ T cell–dependent antitumor activity following radiation

Abstract

DNA-damaging chemotherapy and radiation therapy are integrated into the treatment paradigm of the majority of cancer patients. Recently, immunotherapy that targets the immunosuppressive interaction between programmed death 1 (PD-1) and its ligand PD-L1 has been approved for malignancies including non–small cell lung cancer, melanoma, and head and neck squamous cell carcinoma. ATR is a DNA damage–signaling kinase activated at damaged replication forks, and ATR kinase inhibitors potentiate the cytotoxicity of DNA-damaging chemotherapies. We show here that the ATR kinase inhibitor AZD6738 combines with conformal radiation therapy to attenuate radiation-induced CD8+ T cell exhaustion and potentiate CD8+ T cell activity in mouse models of Kras-mutant cancer. Mechanistically, AZD6738 blocks radiation-induced PD-L1 upregulation on tumor cells and dramatically decreases the number of tumor-infiltrating Tregs. Remarkably, AZD6738 combines with conformal radiation therapy to generate immunologic memory in complete responder mice. Our work raises the possibility that a single pharmacologic agent may enhance the cytotoxic effects of radiation while concurrently potentiating radiation-induced antitumor immune responses.

Authors

Frank P. Vendetti, Pooja Karukonda, David A. Clump, Troy Teo, Ronald Lalonde, Katriana Nugent, Matthew Ballew, Brian F. Kiesel, Jan H. Beumer, Saumendra N. Sarkar, Thomas P. Conrads, Mark J. O’Connor, Robert L. Ferris, Phuoc T. Tran, Greg M. Delgoffe, Christopher J. Bakkenist

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Figure 3

AZD6738 attenuates radiation-induced PD-L1 expression in CT26 tumors.

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AZD6738 attenuates radiation-induced PD-L1 expression in CT26 tumors. (A...
(A) Schematic showing schedules of IR, AZD6738, and time points for tumor PD-L1 expression analyses. Dose and time of administration of AZD6738 were the same as in Figure 1. (B) Representative histograms of PD-L1 expression on CT26 tumor cells at day 5 for the designated treatments and isotype control, and corresponding quantitation of the fold change in PD-L1 median fluorescence intensity (MFI) relative to the average MFI of vehicle controls (within a given experiment). Data from 4 independent experiments (3 for AZD6738), each with 1–4 mice per arm. n = 10 vehicle, 7 AZD6738, 9 IR, 8 AZD6738 + IR. (C) Quantitation of fold change in PD-L1 MFI following treatment in vitro with AZD6738 (300 nM), 6 Gy IR, AZD6738 plus IR, or DMSO control. Data represent 6 independent biological replicates. (D) Quantitation of the percentage of tumor-infiltrating CD8+ T cells expressing IFN-γ or IFN-γ and TNF-α following stimulation with PMA/ionomycin at day 5. Data from 3 independent experiments (1 for AZD6738), each with 1–3 mice per arm. n = 6 vehicle, 3 AZD6738, 5 IR, 5 AZD6738 + IR. (B–D) Mean and SD bars shown. *P < 0.05, **P < 0.01, ****P < 0.0001, ANOVA with Tukey’s multiple-comparisons test. Brackets not shown for comparisons that were not statistically significant.