Targeting HIF-1α abrogates PD-L1–mediated immune evasion in tumor microenvironment but promotes tolerance in normal tissues
Christopher M. Bailey, Yan Liu, Mingyue Liu, Xuexiang Du, Martin Devenport, Pan Zheng, Yang Liu, Yin Wang
Christopher M. Bailey, Yan Liu, Mingyue Liu, Xuexiang Du, Martin Devenport, Pan Zheng, Yang Liu, Yin Wang
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Research Article

Targeting HIF-1α abrogates PD-L1–mediated immune evasion in tumor microenvironment but promotes tolerance in normal tissues

Abstract

A combination of anti–CTLA-4 plus anti–PD-1/PD-L1 is the most effective cancer immunotherapy but causes high incidence of immune-related adverse events (irAEs). Here we report that targeting of HIF-1α suppressed PD-L1 expression on tumor cells and tumor-infiltrating myeloid cells, but unexpectedly induced PD-L1 in normal tissues by an IFN-γ–dependent mechanism. Targeting the HIF-1α/PD-L1 axis in tumor cells reactivated tumor-infiltrating lymphocytes and caused tumor rejection. The HIF-1α inhibitor echinomycin potentiated the cancer immunotherapeutic effects of anti–CTLA-4 therapy, with efficacy comparable to that of anti–CTLA-4 plus anti–PD-1 antibodies. However, while anti–PD-1 exacerbated irAEs triggered by ipilimumab, echinomycin protected mice against irAEs by increasing PD-L1 levels in normal tissues. Our data suggest that targeting HIF-1α fortifies the immune tolerance function of the PD-1/PD-L1 checkpoint in normal tissues but abrogates its immune evasion function in the tumor microenvironment to achieve safer and more effective immunotherapy.

Authors

Christopher M. Bailey, Yan Liu, Mingyue Liu, Xuexiang Du, Martin Devenport, Pan Zheng, Yang Liu, Yin Wang

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Figure 5

Echinomycin suppresses PD-L1 on tumor cells and tumor-infiltrating myeloid cells and expands the IFN-γ–producing CD8+ and CD4+ T cells with or without anti–CTLA-4 antibodies.

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Echinomycin suppresses PD-L1 on tumor cells and tumor-infiltrating myelo...
C57BL/6 mice received E0771 cells (0.5 × 106/mouse) on day 0 followed by treatment with vehicle, echinomycin (LEM, 0.25 mg/kg/dose), anti–CTLA-4 (9D9, 0.2 mg/mouse/dose), or 9D9 plus LEM on days 6, 8, 10, and 12. On day 14, the tumors were analyzed by flow cytometry. (A–D) PD-L1 expression on tumor and tumor-associated myeloid cells. PD-L1 expression was analyzed on tumor cells (gated on live CD45– singlets) (A), M-MDSCs (gated on live CD45+CD11b+CD11c–Ly6ChiLy6G– singlets) (B), PMN-MDSCs (gated on live CD45+CD11b+CD11c–Ly6CintLy6G+ singlets) (C), or CD11c+ TAMs (gated on live CD45+CD11b+CD11c+ singlets) (D). Upper panels show representative histograms of PD-L1. In the lower panels, dot plots show the PD-L1 MFI for individual mice from 3 independent experiments (n = 5 mice/group/experiment). The data are presented as the mean ± SEM of PD-L1 MFI and were analyzed by 1-way ANOVA with Sidak’s multiple-comparison test (A) or by 2-tailed, unpaired Student’s t test (B–D). (E and F) Frequency of TILs producing IFN-γ. The frequencies of CD8+IFN-γ+ (Tc1) among total CD8+ TILs (E) and CD4+IFN-γ+ (Th1) among total CD4+ TILs (F) are shown. The tumor cell suspensions were cultured for 4 hours in the presence of PMA plus ionomycin and GolgiStop prior to staining. The dot plots show the Tc1 or Th1 cell frequencies for individual mice from 2 independent experiments (n = 5 mice/group/experiment), which were analyzed by 1-way ANOVA with Sidak’s multiple-comparison test. *P < 0.05; **P < 0.01; ***P < 0.001.