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 7

AZD6738 attenuates coexpression of CD8+ T cell exhaustion markers and promotes CD8+ T cell effector function in CT26 tumors following radiation.

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AZD6738 attenuates coexpression of CD8+ T cell exhaustion markers and pr...
(A) Representative contour plots depicting PD-1 and LAG-3 expression on splenic and tumor-infiltrating (TIL) CD8+ T cells for the designated treatment groups at day 12. (B) Quantitation of the percentage of TIL CD8+ T cells that coexpress PD-1 and LAG-3 or PD-1 and Tim-3 at day 12. Data from 3 independent experiments per time point, each with 1–3 mice per arm. n at day 12 = 6 per arm (7 IR). (C) Representative contour plots depicting IFN-γ and TNF-α expression by splenic and tumor-infiltrating (TIL) CD8+ T cells for the designated treatment groups following stimulation with PMA/ionomycin at day 12. (D) Quantitation of the percentage of TIL CD8+ T cells that elicit IFN-γ or IFN-γ and TNF-α following stimulation with PMA and ionomycin at days 9 and 12. Day 9 data from 1 experiment with the IR/AZD6738 + IR arms and vehicle/AZD6738 arms staggered and harvested/stained on separate days. n at day 9 = 5 per arm (4 IR). Day 12 data from 3 independent experiments, each with 1–3 mice per arm, with harvesting/staining for all arms performed on the same day within a given experiment. n at day 12 = 5 vehicle, 6 AZD6738, 6 IR, 7 AZD6738 + IR. (B and D) Mean and SD bars shown. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001, ANOVA with Tukey’s multiple-comparisons test. Brackets not shown for comparisons that were not statistically significant.