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ENO1 promotes antitumor immunity by destabilizing PD-L1 in NSCLC

Cellular & Molecular Immunology volume 18, pages 2045–2047 (2021)Cite this article

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PD-L1 plays an important role in inhibiting T-cell activity and driving tumor cell escape from immune surveillance by binding its ligand, PD-1, on T cells.1 Several intracellular and extracellular factors, such as interferon-γ (IFN-γ), MYC, transforming growth factor β, and miR-200, may modulate PD-L1 expression by transcriptional and posttranscriptional mechanisms.2,3,4,5 Here we discovered that ENO1, a novel protein, is involved in the regulation of PD-L1. ENO1 could destabilize PD-L1 and decrease its expression by promoting PD-L1 ubiquitination and subsequent proteasomal degradation in lung cancer cells. A lung cancer tissue microarray also showed that the expression of ENO1 was negatively correlated with PD-L1. Furthermore, overexpression of ENO1 sensitized tumor cells to specific T-cell killing and increased T-cell-mediated antitumor immunity in syngeneic mouse models.

To determine whether downregulation of the PD-L1 protein by ENO1 occurs at the transcriptional level, real-time PCR was performed. The results showed that ENO1 transfection had no effect on PD-L1 mRNA levels in H1299 cells (Supplementary Fig. S5), indicating that ENO1 regulates PD-L1 expression mainly at the posttranscriptional level. Therefore, we detected the impact of ENO1 on PD-L1 protein stability. As shown in Fig. 1F, G, the half-life of PD-L1 was remarkably shorter in HA-ENO1-transfected H1299 cells but largely extended in ENO1 small interfering RNA-transfected H1299 cells, as shown by a chase experiment with the protein synthesis inhibitor cycloheximide. These results imply that ENO1 could promote the degradation of PD-L1 in vitro. Then, we treated H1299 cells with the proteasome inhibitor MG132 and found that altered PD-L1 levels in cells with ENO1 overexpression or depletion could be restored by incubation with MG132 (Fig. 1H, I), suggesting that ENO1 mediates the proteasomal degradation of PD-L1. Ubiquitination is a key process that leads to the proteasomal degradation of cellular proteins.6 A signal for polyubiquitinated PD-L1 was detected upon ENO1 transfection by ubiquitination ladder assay; moreover, the ubiquitination of PD-L1 was further enhanced in the presence of MG132 (Fig. 1J). These results demonstrate that ENO1 downregulates PD-L1 expression by promoting its ubiquitination and subsequent proteasome-mediated degradation.

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Fig. 1: ENO1 destabilized PD-L1 to sensitize lung cancer cells to T-cell killing and promote antitumor immunity.

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Acknowledgements

This work was supported by the National Natural Science Fund (81972617 and 81772948).

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  1. These authors contributed equally: Chunyi Zhang, Kunpeng Zhang.

Authors and Affiliations

  1. Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai, China

    Chunyi Zhang

  2. Department of Chest Surgery, Zhongshan Hospital, Fudan University, Shanghai, China

    Kunpeng Zhang, Jie Gu & Di Ge

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  1. Chunyi Zhang
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  2. Kunpeng Zhang
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  4. Di Ge
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C.Y.Z. and D.G. designed the experiments and wrote the paper. C.Y.Z., K.P.Z., and J.G. performed the experiments. All authors read and approved the final manuscript.

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Correspondence to Chunyi Zhang or Di Ge.

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Zhang, C., Zhang, K., Gu, J. et al. ENO1 promotes antitumor immunity by destabilizing PD-L1 in NSCLC. Cell Mol Immunol 18, 2045–2047 (2021). https://doi.org/10.1038/s41423-021-00710-y

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