Researchers identify a protein that recharges T cells for long-lasting cancer remission

Researchers discover a novel protein therapy that recharges exhausted T cells, unleashing their power to eradicate tumors and improve cancer treatment outcomes.

In a recent study published in Nature, researchers used an interleukin-4 fusion protein (Fc–IL-4) to target CD8+ T cells and enhance antitumor efficacy in combination with type 1 immunity-centric therapies.

They found that Fc–IL-4 improved the function and metabolic activity of terminally exhausted CD8+ T cells in tumors, leading to durable tumor remission through synergy with type 1 immune responses.

Background

Current cancer immunotherapies like adoptive T cell transfer (ACT) and immune checkpoint blockade (ICB) focus on activating type 1 immunity. However, resistance and relapse still occur due to the exhaustion of cancer-fighting CD8⁺ T cells.

These exhausted cells lose their effectiveness over time, limiting the success of treatments. While type 1 immunity has been the primary focus, emerging evidence shows that type 2 immunity, particularly T helper 2 (T_H2) cells, can also aid in fighting cancer by altering the tumor environment.

The potential to combine type 1 and type 2 immunity for more durable antitumor effects remains underexplored. In the present study, researchers proposed that interleukin-4 (IL-4), a type 2 cytokine known to prolong T and B cell survival, could potentially rejuvenate exhausted tumor-infiltrating T cells, enhancing the effectiveness of cancer immunotherapy.

They created a recombinant fusion protein, Fc–IL-4, which maintained similar bioactivity to native IL-4 but with a significantly extended half-life. They then studied the impact of Fc–IL-4 on antigen-specific CD8+ T cells within tumors.

About the study

In this study, six- to eight-week-old female mice and various transgenic mice were used. In vitro-activated PMEL T cells were transferred to mice with B16F10 melanoma tumors, in combination with Fc–IL-4 (peritumorally administered) or phosphate-buffered saline (PBS) as a control. CD8⁺ tumor-infiltrating lymphocytes (TILs) were analyzed for phenotypic changes, focusing on PD-1⁺TIM-3⁺ TTE cells.

The antigen dependency of TIL expansion was assessed by co-transferring naive PMEL and OT1 T cells. Single-cell RNA sequencing (scRNA-seq) was performed on sorted tumor antigen-specific CD8⁺ TILs from the two treatment conditions to investigate transcriptomic profiles.

Further, researchers examined the effects of Fc–IL-4 on CD8⁺ T central memory T cells (TTE cells). Ex vivo-induced CD8⁺ TTE cells were treated with Fc–IL-4 or PBS. Glut-1 expression and glucose uptake were measured, and extracellular acidification rate (ECAR) after T cell receptor (TCR) stimulation was assessed with a dimeric anti-CD3 antibody.

The metabolomic analysis evaluated changes in 41 metabolites, and single-cell transcriptomic analysis used clustering based on 1,667 Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway genes.

The role of glycolysis was further explored using 2-deoxy-D-glucose (2-DG), and transcription factor binding sites were analyzed through differential motif analysis. Lactate dehydrogenase A (LDHA) knockdown and overexpression experiments were performed to assess the impact on metabolic function.

Results and discussion

The combination of Fc–IL-4 with type 1-centric ACT significantly enhanced the infiltration of CD8⁺ T cells into the tumor microenvironment (TME), particularly enriching the PD-1⁺TIM-3⁺ TTE subset.

The cell counts of these TTE cells increased significantly in both transferred and endogenous CD8⁺ T cells. Fc–IL-4 treatment also boosted granzyme B production and enhanced the polyfunctionality of CD8⁺ TTE cells.

The enrichment of CD8⁺ TTE cells was found to be antigen-dependent. Furthermore, Fc–IL-4 showed a direct effect on CD8⁺ TTE cells by promoting their survival rather than their proliferation.

Fc–IL-4 significantly boosted antitumor immunity in both syngeneic and xenograft tumor models, demonstrating its potential as an effective and safe adjuvant for ACT and ICB therapies. In mouse melanoma and colon cancer models, Fc–IL-4 combined with ACT or ICB therapies led to complete tumor eradication and durable cures in 60-100% of cases, with long-term immune memory.

In human cancer models, hu.Fc–IL-4 enhanced the proliferation and cytotoxicity of CD19-CAR-T (chimeric antigen receptor T) cells, achieving tumor clearance in 75-80% of mice and improved survival in leukemia models.

Fc–IL-4 treatment significantly enhanced Glut-1 expression, glucose uptake, and extracellular lactate levels in CD8+ TTE cells, resulting in elevated ECAR and glycolytic activity, while oxidative phosphorylation remained largely unaffected.

Metabolomic analysis indicated the upregulation of key glycolytic metabolites. Single-cell transcriptomic analysis revealed specific gene clusters enriched in glycolysis-related genes in Fc–IL-4-treated cells. Inhibiting glycolysis with 2-DG negated the effects of Fc–IL-4, emphasizing the importance of glycolysis for metabolic reprogramming.

LDHA was identified as a key enzyme in enhancing glycolysis, with its inhibition or knockdown reducing the response to Fc–IL-4, while overexpression boosted TTE cell function.

Additionally, Fc–IL-4 treatment increased nicotinamide adenine dinucleotide (NAD) levels, crucial for cell survival, with LDHA facilitating NAD⁺–NADH recycling. Supplementation with nicotinamide riboside, a precursor to NAD, further promoted glycolysis and T cell activity.

Conclusion

In conclusion, the study shows that Fc–IL-4 is an effective type 2 cytokine immunotherapy that works well with type 1 immunity to produce lasting anti-cancer responses.

The study reveals how these immune responses can synergize and suggests incorporating type 2 immune factors to enhance the response to cancer immunotherapy, potentially improving outcomes in patients with cancer.

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