Targeting HIF-1α abrogates PD-L1–mediated immune evasion in tumor microenvironment but promotes tolerance in normal tissues
Christopher M. Bailey, … , Yang Liu, Yin Wang
Christopher M. Bailey, … , Yang Liu, Yin Wang
Published March 3, 2022
Citation Information: J Clin Invest. 2022;132(9):e150846. https://doi.org/10.1172/JCI150846.
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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 1

HIF-1α drives PD-L1 expression in tumor cells.

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HIF-1α drives PD-L1 expression in tumor cells. (A) Western blot of HIF-1...
(A) Western blot of HIF-1α protein in murine breast cancer cells. (B) Effect of echinomycin on PD-L1 expression in 4T1 or E0771. Tumor cells were treated with echinomycin (EM, 0.45 nM) or DMSO (vehicle) for 48 hours (1:1000 dilution). Flow cytometry histograms for PD-L1 staining are shown. (C) Effect of CoCl2 on PD-L1 expression in E0771 cells. E0771 cells were cultured as in B with CoCl2 (250 μM) or PBS and PD-L1 was measured by flow cytometry. (D) 4T1-HRE cells were treated for 24 hours with PBS or CoCl2 (250 μM). Flow cytometry histograms for EGFP intensity are shown. (E) BALB/c mice received 1 × 106 4T1-HRE cells (day 0). On day 21, tumors were dissociated and stained for PD-L1. The PD-L1 MFI is plotted for the tumor cells (gated on CD45–EGFP+ singlets) further divided into top/bottom 30th percentiles based on EGFP. The data are pooled from 3 experiments, presented as mean ± SEM, and were analyzed by Student’s t test. (F) 4T1, E0771, or MC38 cells were transplanted into BALB/c or C57BL/6 mice, which received vehicle or liposome-encapsulated echinomycin (LEM, 0.25 mg/kg) every other day for a total of 5 doses. Representative PD-L1 immunofluorescence staining is shown for tumor tissues (2 days after final dose). Blue, DAPI. Scale bars: 20 μm. (G–J) Effects of Hif1a shRNA on PD-L1 expression in E0771 cells in vitro. E0771 cells were transduced with lentivirus packaged with scrambled (sh-Scr) or Hif1a shRNA (sh-Hif1a) and cultured under normoxia for 48 hours with DMSO (–) or echinomycin (EM, 1.35 nM). Flow cytometry histograms of PD-L1 staining are shown, comparing effects of Hif1a knockdown (G) or effects of echinomycin between sh-Scr (H) and sh-Hif1a (I) cells. (J) The data are summarized, expressed as mean ± SEM of PD-L1 MFI for triplicate wells, and were analyzed by 1-way ANOVA with Sidak’s post hoc test. Data are representative of 3 independent experiments. ****P < 0.0001.