While cancer cells acquire malignant traits through epigenetic remodeling, it remains unclear how immune-derived inflammatory factors regulate the epigenetics of colorectal cancer cells. Now, researchers have discovered that the interleukin-26 produced by exhausted T cells can reprogram the cancer cell epigenome, promoting immune evasion. These findings provide new insights into the complex landscape of cancer immunotherapy and highlight potential opportunities to improve future treatment strategies.

Immune checkpoint inhibitors have revolutionized cancer treatment, yet many colorectal tumors remain resistant. Even among patients who initially respond, more than half eventually develop resistance, highlighting the need to better understand how tumors evade immune attack. Although chronic inflammation has long been linked to epigenetic changes in cancer, exactly how inflammatory signals reprogram the cancer-cell epigenome and reshape the tumor microenvironment has remained unclear. Emerging evidence has implicated the inflammatory cytokine interleukin (IL)-26 in tumor-associated inflammation, but its role in driving immune escape and resistance to anti-programmed death protein 1 (PD-1) immunotherapy remained unknown.

In a groundbreaking study published in the journal of Nature Communications on July 17, 2026, a team of researchers led by Assistant Professor Takumi Itoh from the Department of Therapy Development and Innovation for Immune Disorders and Cancers, Graduate School of Medicine, Juntendo University, Japan, along with colleagues, investigated how IL-26-producing type 17 T cells contribute to immune checkpoint inhibitor resistance in colorectal cancer. The team sought to uncover the molecular mechanism by which the immune-derived cytokine IL-26 reprograms tumor cells to evade immune attack.

We identified the immune-derived cytokine IL-26 as an unusual regulator that acts directly on cancer cells, triggering epigenetic reprogramming and reshaping the tumor microenvironment to promote immune escape."

Dr. Takumi Itoh, Assistant Professor, Department of Therapy Development and Innovation for Immune Disorders and Cancers, Graduate School of Medicine, Juntendo University

To uncover this mechanism, the researchers combined single-cell RNA sequencing and transcriptomic analyses of human colorectal cancer samples with human IL-26 transgenic and inflammation-induced mouse models. They complemented these studies with a series of cellular and molecular experiments, including immunofluorescence, chromatin immunoprecipitation sequencing, co-immunoprecipitation, and targeted inhibition of IL-26, signal transducer and activator of transcription 1 (STAT1), bromodomain-containing protein 4 (BRD4), C-X-C motif chemokine ligand (CXCL), and neutrophils, enabling them to trace how IL-26 influences tumor biology from the molecular to the whole-organism level.

The study revealed that IL-26-producing CD8⁺ type 17 T cells accumulated in anti-PD-1-resistant colorectal tumors. Unlike conventional cytokines, IL-26 entered tumor cell nuclei, where it interacted with STAT1 and recruited transcriptional regulators, including nuclear factor kappa B and BRD4. This activated an epigenetic program that increased CXCL1, CXCL2, CXCL3, and CXCL7 expression, attracting immunosuppressive neutrophils. These neutrophils weakened antitumor CD8⁺ T-cell activity, enabling immune evasion and reducing the effectiveness of anti-PD-1 therapy. Importantly, targeting IL-26, BRD4, CXC receptor 2, or neutrophils restored antitumor immunity and improved immunotherapy responses in preclinical models.

Together, these findings reveal that IL-26 fundamentally reshapes the tumor immune landscape by linking inflammation to epigenetic remodeling and immune suppression. Explaining the biological impact of the findings, Dr. Itoh notes, "We identified IL-26 as a rare cytokine capable of inducing epigenetic changes in cancer cells. IL-26 increased the expression of CXCL chemokines by several thousand-fold. This effect was sufficiently powerful to substantially reshape the tumor microenvironment, creating inflammatory conditions that promote immune evasion and tumor progression." Together, the findings identify the IL-26–STAT1–BRD4 axis as a previously unrecognized mechanism linking inflammation, epigenetic remodeling, and immunotherapy resistance, offering a promising target for improving colorectal cancer treatment.

Beyond identifying a new mechanism of immune escape, the findings open new opportunities for overcoming resistance to immune checkpoint blockade. Therapeutic strategies targeting IL-26 or disrupting its downstream epigenetic program could complement existing anti-PD-1 therapies by preventing neutrophil-driven immune suppression and restoring effective antitumor immune responses. "In the future, developing therapeutic strategies blocking IL-26 or preventing the epigenetic changes could potentially improve the effectiveness of immunotherapy in treatment-resistant cancers, leading to new treatments for a wide range of cancers and chronic inflammatory diseases," says Dr. Itoh.

Overall, this study reveals IL-26 as a critical link between immune-cell signaling, epigenetic reprogramming, and tumor immune evasion. By uncovering how an inflammatory cytokine can transform cancer cells into a more immunosuppressive state, the research identifies a promising therapeutic vulnerability and provides a foundation for developing next-generation combination therapies to improve cancer immunotherapy outcomes.

Source:

Journal reference:

Itoh, T., et al. (2026). IL-26-driven epigenetic remodeling promotes immune evasion in colorectal cancer. Nature Communications. DOI: 10.1038/s41467-026-75754-7. https://www.nature.com/articles/s41467-026-75754-7