Simultaneous blockade of multiple immune system inhibitory checkpoints enhances antitumor activity mediated by interleukin-15 in a murine metastatic colon carcinoma model
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Updated: Jun 8, 2026
Experimental Metastasis and CTL Adoptive Transfer Immunotherapy Mouse Model
Published on: November 26, 2010
Ping Yu1, Jason C Steel, Meili Zhang
1Metabolism Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA.
Purpose:
Interleukin 15 (IL-15) is a promising cytokine for immunotherapy of cancer due to its ability to stimulate the immunity of natural killer, B, and T cells. Its effectiveness, however, may be limited by inhibitory checkpoints and pathways that can attenuate immune responses. Finding strategies to abrogate these negative regulators and enhance the efficacy of IL-15 is a critical challenge.
Experimental Design:
In a preclinical study, we evaluated IL-15 combined with antibodies to block the negative immune regulators cytotoxic T-lymphocyte antigen 4 (CTLA-4) and programmed death ligand 1 (PD-L1) in a metastatic murine CT26 colon carcinoma model.
Results:
IL-15 treatment resulted in a significant prolongation of survival in mice with metastatic tumor. Administration of IL-15, however, also increased expression of PD-1 on the surface of CD8(+) T cells including CD8(+)CD44(high) memory phenotype T cells. Moreover, IL-15 also increased the secretion of the immunosuppressive cytokine, IL-10. Combining IL-15 with anti-PD-L1 and anti-CTLA-4 (multiple immune checkpoint blockade) exhibited greater CTL killing and IFNγ secretion. Moreover, this combination resulted in a significant reduction in surface expression of PD-1 on CD8(+) T cells, a decrease in IL-10 secretion, and led to significantly longer survival of tumor-bearing animals compared with mice treated with IL-15 alone or combined singularly with anti-PD-L1 or anti-CTLA-4.
Conclusions:
Combining the immune stimulatory properties of IL-15 with the simultaneous removal of 2 critical immune system inhibitory checkpoints, we showed enhancement of immune responses leading to increased antitumor activity.
Insights
Combining Interleukin 15 (IL-15) with immune checkpoint blockade targeting CTLA-4 and PD-L1 significantly enhances anti-tumor immunity. This combination therapy improves survival in preclinical cancer models by boosting T cell responses and reducing immunosuppression.
Area of Science:
- Immunology
- Cancer Immunotherapy
- Molecular Biology
Background:
- Interleukin 15 (IL-15) shows promise for cancer immunotherapy by stimulating natural killer, B, and T cells.
- Immune checkpoints like CTLA-4 and PD-L1 can limit the effectiveness of IL-15 by suppressing immune responses.
- Strategies to overcome these inhibitory pathways are crucial for enhancing IL-15 efficacy in cancer treatment.
Purpose of the Study:
- To evaluate the efficacy of combining IL-15 with antibodies against CTLA-4 and PD-L1 in a preclinical cancer model.
- To investigate the impact of this combination therapy on immune cell activity and tumor growth.
Main Methods:
- A preclinical study was conducted using a metastatic murine CT26 colon carcinoma model.
- Mice were treated with IL-15 alone, in combination with anti-CTLA-4, anti-PD-L1, or a combination of both anti-CTLA-4 and anti-PD-L1.
Main Results:
- IL-15 treatment alone prolonged survival but increased PD-1 expression on CD8(+) T cells and IL-10 secretion.
- Combination therapy (IL-15 + anti-PD-L1 + anti-CTLA-4) demonstrated enhanced cytotoxic T lymphocyte (CTL) killing and IFNγ secretion.
- The combination therapy significantly reduced PD-1 expression and IL-10 secretion, leading to superior survival outcomes compared to IL-15 monotherapy or single checkpoint blockade.
Conclusions:
- Simultaneously blocking CTLA-4 and PD-L1 alongside IL-15 stimulation amplifies anti-tumor immune responses.
- This combined approach effectively overcomes immune suppression and enhances antitumor activity.
- The findings support the potential of combining IL-15 with dual immune checkpoint blockade for improved cancer immunotherapy.
