Targeting tumors with IL-21 reshapes the tumor microenvironment by proliferating PD-1intTim-3–CD8+ T cells
Sisi Deng, Zhichen Sun, Jian Qiao, Yong Liang, Longchao Liu, Chunbo Dong, Aijun Shen, Yang Wang, Hong Tang, Yang-Xin Fu, Hua Peng
Sisi Deng, Zhichen Sun, Jian Qiao, Yong Liang, Longchao Liu, Chunbo Dong, Aijun Shen, Yang Wang, Hong Tang, Yang-Xin Fu, Hua Peng
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Research Article Immunology Oncology

Targeting tumors with IL-21 reshapes the tumor microenvironment by proliferating PD-1intTim-3–CD8+ T cells

Abstract

The lack of sufficient functional tumor-infiltrating lymphocytes in the tumor microenvironment (TME) is one of the primary indications for the poor prognosis of patients with cancer. In this study, we developed an Erbitux-based IL-21 tumor-targeting fusion protein (Erb-IL21) to prolong the half-life and improve the antitumor efficacy of IL-21. Compared with Erb-IL2, Erb-IL21 demonstrated much lower toxicity in vivo. Mechanistically, Erb-IL21 selectively expanded functional cytotoxic T lymphocytes but not dysfunctional CD8+ T cells in the TME. We observed that the IL-21–mediated antitumor effect largely depended on the existing intratumoral CD8+ T cells, instead of newly migrated CD8+ T cells. Furthermore, Erb-IL21 overcame checkpoint blockade resistance in mice with advanced tumors. Our study reveals that Erb-IL21 can target IL-21 to tumors and maximize the antitumor potential of checkpoint blockade by expending a subset of tumor antigen–specific CD8+ T cells to achieve effective tumor control.

Authors

Sisi Deng, Zhichen Sun, Jian Qiao, Yong Liang, Longchao Liu, Chunbo Dong, Aijun Shen, Yang Wang, Hong Tang, Yang-Xin Fu, Hua Peng

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Figure 5

IL-21 proliferates PD-1intTim-3– more than PD-1+Tim-3 +CD8 + T cells in tumors.

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IL-21 proliferates PD-1intTim-3– more than PD-1+Tim-3 +CD8 + T cells in ...
(A, B, and E–G) C57BL/6 mice (n = 5-6) were inoculated with 6 × 105 to 8 × 105 MC38-OVA cells and were intratumorally treated with 20 μg hIgG or Erb-IL21 on days 12 and 15. Five days after the first treatment, tumor tissues were analyzed by flow cytometry. (A) MFI of PD-1 on antigen-specific intratumoral CD8+ T cells. MFI is defined as the geometric median fluorescence intensity. (B) Tumor-bearing mice were i.p. treated with 25 μg FTY720 1 day before treatment and every other day 3 times. MFI of PD-1 on antigen-specific (OVA-specific) CD8+ T cells was analyzed. (C) The proliferation of PD-1+ T cells. CFSE-labeled CD8+ T cells from C57BL/6 WT mouse spleen were cocultured with 0.2 μg anti-CD3 and 0.2 μg anti-CD28, with an additional 100 ng Erbitux or Erb-IL21 for 72 hours. Cells treated with hIgG were used as control. The percentage of proliferating PD-1hi and PD-1intCD8+ T cells was analyzed by flow cytometry (n = 3 independent wells). (D) Frequency of PD-1intKi-67+ or PD-1hiKi-67+ in OVA-specific CD8+ T cells. (E) Frequency of PD1intTim-3– and PD-1+Tim-3+ in OVA-specific CD8+ T cells. (F and G) Percentage of PD-1intTim-3– or PD-1+Tim-3+ in CD8+ T cells. (H) Percentage of PD1intTim-3–Ki-67 + or PD-1+Tim-3+Ki-67 +in CD8+ T cells. The mean ± SEM values are shown Unpaired t tests were used to analyze the other data. *P < 0.05, **P < 0.01, ***P < 0.0001, ****P < 0.0001. One of two representative experiments is shown.