Type I IFN protects cancer cells from CD8+ T cell–mediated cytotoxicity after radiation
Jianzhou Chen, Yunhong Cao, Bostjan Markelc, Jakob Kaeppler, Jenny A.F. Vermeer, Ruth J. Muschel
Jianzhou Chen, Yunhong Cao, Bostjan Markelc, Jakob Kaeppler, Jenny A.F. Vermeer, Ruth J. Muschel
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Research Article Immunology Oncology

Type I IFN protects cancer cells from CD8+ T cell–mediated cytotoxicity after radiation

Abstract

Treatment of tumors with ionizing radiation stimulates an antitumor immune response partly dependent on induction of IFNs. These IFNs directly enhance dendritic cell and CD8+ T cell activity. Here we show that resistance to an effective antitumor immune response is also a result of IFN signaling in a different cellular compartment of the tumor, the cancer cells themselves. We abolished type I IFN signaling in cancer cells by genetic elimination of its receptor, IFNAR1. Pronounced immune responses were provoked after ionizing radiation of tumors from 4 mouse cancer cell lines with Ifnar1 knockout. This enhanced response depended on CD8+ T cells and was mediated by enhanced susceptibility to T cell–mediated killing. Induction of Serpinb9 proved to be the mechanism underlying control of susceptibility to T cell killing after radiation. Ifnar1-deficient tumors had an augmented response to anti–PD-L1 immunotherapy with or without radiation. We conclude that type I IFN can protect cancer cells from T cell–mediated cytotoxicity through regulation of Serpinb9. This result helps explain why radiation of tumors can stimulate antitumor immunity yet also result in resistance. It further suggests potential targets for intervention to improve therapy and to predict responses.

Authors

Jianzhou Chen, Yunhong Cao, Bostjan Markelc, Jakob Kaeppler, Jenny A.F. Vermeer, Ruth J. Muschel

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Figure 4

Ifnar1-KO MC38 tumor cells are more susceptible to CD8+ T cell–mediated killing.

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Ifnar1-KO MC38 tumor cells are more susceptible to CD8+ T cell–mediated...
WT and Ifnar1-KO MC38 cells were cocultured with CD8+ T cells derived from either WT or Ifnar1-KO MC38 tumors at a ratio of CD8+ T cells/tumor cells of 3:2 for 48 hours. (A) Percentage of cell killing. n = 4. Irradiated MC38 cells (WT or Ifnar1-KO) were cocultured with CD8+ T cells derived from irradiated WT or Ifnar1-KO MC38 tumors at a ratio of 3:2. Cells in medium supplemented with Caspase-3/7 Green detection reagent were imaged with an epifluorescence microscope. (B) The percentage of tumor cells becoming caspase-3/7+ following interaction with CD8+ T cells was evaluated. n = 4. GFP-tagged WT MC38 cells and mCherry-tagged Ifnar1-KO MC38 cells at a ratio of 1:1 were injected subcutaneously into C57BL/6 mice. Established tumors were subjected to 0 Gy or 10 Gy IR on day 0. On days 3 and 5, and 22 for irradiated tumors, the percentages of GFP- and mCherry-positive cells in the CD45-negative population were assessed by flow cytometry (representative plot in C and summary in D). n =4. Tumors formed from a mixture of cells (MC38 WT-GFP + Ifnar1-mCherry, 1:1) were subjected to the following: 0 Gy, 10 Gy (day 0) + isotype control Abs; 10 Gy + anti-CD8 Ab; and 10 Gy + anti-NK1.1 Ab. The distribution of GFP versus mCherry cells in the CD45-negative live population on day 3 was assessed by flow cytometry (representative plot in E and quantification in F). n = 5. Data represent mean ± SD. Comparison of 2 means was performed by the Mann-Whitney U test. Comparison of means of more than 2 groups was performed by 1-way ANOVA with Tukey’s multiple-comparisons test (NS: P ≥ 0.05, *P < 0.05, ***P < 0.001).