Orphan Nuclear Receptor Ligands Trigger Ferroptosis and Reshape Immunity in Colon Cancer

Colon cancer remains one of the most common and lethal malignancies worldwide, and despite advances in surgery, chemotherapy, and immunotherapy, many patients still face limited treatment options. A new study published in Cell Death Discovery by researchers at Texas A&M University and the Houston Methodist Research Institute offers a fresh angle of attack. The team, led by Stephen Safe, investigated a family of synthetic molecules that target two poorly understood proteins inside cancer cells, the orphan nuclear receptors NR4A1 and NR4A2, and found that these compounds can simultaneously kill tumor cells through a distinctive form of cell death and reorganize the immune landscape of the tumor to make it more visible to the body’s defenses.

The receptors at the heart of this work belong to the nuclear receptor superfamily, a large group of proteins that act as molecular switches controlling gene expression. Unlike their better-studied cousins such as the estrogen or glucocorticoid receptors, NR4A1 and NR4A2 are called orphan receptors because no natural ligand has been definitively identified for them. In most solid tumors, including colon cancer, both receptors behave as pro-oncogenic factors: they help cancer cells proliferate, resist apoptosis, invade surrounding tissue, and survive metabolic stress. Because they sit at the intersection of so many tumor-promoting pathways, they have long been considered attractive drug targets, but exploiting them therapeutically requires molecules that can bind and modulate their activity in a controlled way.

The Safe laboratory has spent years developing a class of synthetic ligands based on a chemical scaffold known as 1,2-bis(3′-indolyl)-1-(3,5-disubstitutedphenyl)methane, abbreviated DIM-3,5. These compounds are built around two indole rings, the same structural motif found in compounds derived from cruciferous vegetables, connected through a central methane carbon to a substituted phenyl ring. By varying the substituents on that phenyl ring, the chemists can tune how the molecule interacts with NR4A1 and NR4A2. In the new study, the researchers focused on dual NR4A1/2 ligands and asked a specific question: can these compounds push colon cancer cells into ferroptosis, an iron-dependent form of regulated cell death that has attracted enormous interest as a vulnerability in tumors resistant to conventional therapies?

Ferroptosis is mechanistically very different from apoptosis. Instead of the orderly cellular dismantling characteristic of programmed cell death, ferroptosis is driven by catastrophic oxidative damage to cell membranes. When the lipid bilayer is not adequately protected by antioxidant systems, polyunsaturated fatty acids in the membrane undergo peroxidation, generating reactive oxygen species and lipid peroxides that rupture the cell from the outside in. The central guardian against this process is the enzyme glutathione peroxidase 4, or GPX4, which detoxifies lipid hydroperoxides using glutathione as a cofactor. Closely linked to this defense is the cystine/glutamate antiporter SLC7A11, which imports cystine needed to replenish glutathione. Tumor cells, which already operate under high oxidative stress, are often exquisitely dependent on this GPX4-SLC7A11 axis, making it a promising therapeutic chokepoint.

The experimental results reported in the study show that the DIM-3,5 ligands do exactly what a ferroptosis-inducing agent should do. Treatment of colon cancer cells led to a marked enhancement of reactive oxygen species, detected using BODIPY fluorescence, a widely used probe whose signal shifts when lipid peroxidation accumulates in membranes. Consistent with this, the cells produced increased amounts of malondialdehyde, a well-established degradation product of lipid peroxides that serves as a chemical fingerprint of membrane damage. These biochemical changes were accompanied by a characteristic reprogramming of ferroptosis-related gene expression: the transferrin receptor, also known as TFR or CD71, was induced, while GPX4 and SLC7A11 were both decreased. Inducing the transferrin receptor increases iron uptake into the cell, feeding the Fenton chemistry that drives lipid peroxidation, while simultaneously suppressing the two main antioxidant safeguards. The net effect is a convergence of pressure on the membrane lipids from multiple directions at once.

One of the most technically significant contributions of the paper is the molecular dissection of how NR4A receptors control GPX4 expression in the first place. Using knockdown experiments, promoter analysis, and chromatin immunoprecipitation, the team demonstrated that GPX4 transcription is regulated by a partnership between NR4A2 and the transcription factor Sp4. Sp4 binds directly to specific DNA sequences in the GPX4 promoter, and NR4A2 functions as a ligand-dependent cofactor for the DNA-bound Sp4. In other words, NR4A2 does not simply float in the nucleus as an independent regulator; it is recruited to the promoter through its interaction with Sp4, and its activity there depends on the ligand occupying its binding pocket. When the DIM-3,5 ligands engage NR4A2, this cofactor arrangement is disrupted, and the GPX4 gene is no longer efficiently transcribed. This mechanism explains how a single compound can lower the cell’s antioxidant shield and provides a concrete structural and functional rationale for targeting NR4A2 in ferroptosis-based cancer therapy.

Importantly, the researchers did not stop at cell culture experiments. To test whether the compounds could work in a living organism with an intact immune system, they used a syngeneic mouse xenograft model in which CT26 mouse colon cancer cells are implanted into immunocompetent mice. Syngeneic models are particularly valuable because, unlike human tumor cells grown in immunodeficient mice, they allow the full interplay between the tumor and the host immune system to unfold. The team treated the animals with the 3,5-dichloro analog of the DIM-3,5 series, referred to as DIM-3,5-Cl2, at a dose of 2.5 milligrams per kilogram per day. The result was a significant inhibition of colon tumor growth, confirming that the ferroptotic and gene-regulatory effects observed in vitro translate into tangible antitumor activity in vivo.

Perhaps the most striking findings came from the analysis of the tumor-infiltrating lymphocytes and other immune cells within the treated tumors. Flow cytometric profiling revealed that DIM-3,5-Cl2 treatment increased the population of CD8-positive T cells, the cytotoxic lymphocytes that directly kill tumor cells and are the primary mediators of successful cancer immunotherapy. At the same time, the treatment decreased the abundance of granulocytic myeloid-derived suppressor cells, or g-MDSC, a population of immature myeloid cells that potently suppresses antitumor immune responses and is associated with poor prognosis in many cancers. The ratio of M1 to M2 macrophages also shifted favorably, moving away from the immunosuppressive, tumor-promoting M2 phenotype and toward the inflammatory, tumoricidal M1 phenotype. In addition, the percentage of B cells within the tumor microenvironment increased, further supporting enhanced immune surveillance.

This dual mechanism, direct ferroptosis induction combined with immune reprogramming, is what makes the study noteworthy beyond the colon cancer field. Ferroptosis and immunity are increasingly recognized as deeply intertwined processes. When tumor cells die by ferroptosis, they release damage-associated molecular patterns and oxidized lipid mediators that can stimulate dendritic cells and promote cross-presentation of tumor antigens to T cells. Conversely, immunosuppressive myeloid cells within tumors secrete factors that help cancer cells resist lipid peroxidation. By simultaneously weakening the tumor’s antioxidant defenses and dismantling the suppressive immune circuitry that shields it, the DIM-3,5 ligands appear to attack the cancer from two complementary directions, a strategy that mirrors the logic of successful combination immunotherapies but achieves it with a single small molecule.

The work, which was supported by the Syd Kyle Chair Endowment, Texas A&M AgriLife, and the National Institutes of Health, is still at the preclinical stage, and the path from a mouse xenograft model to an approved human therapy is long and uncertain. Dose optimization, pharmacokinetics, toxicity profiling, and testing in additional tumor models will all be necessary before NR4A ligands could enter clinical trials. Nevertheless, the study establishes a clear mechanistic framework: NR4A1 and NR4A2, long appreciated as pro-oncogenic transcriptional regulators, can be pharmacologically exploited to collapse the GPX4-dependent antioxidant defense through the NR4A2-Sp4 cofactor mechanism, thereby triggering ferroptosis, while the same ligands reshape the tumor immune microenvironment in ways that favor immune-mediated tumor control. For a disease as stubborn as colon cancer, a molecule that turns the tumor’s own lipid chemistry against it and simultaneously invites the immune system to the scene represents a genuinely compelling new direction.

Subject of Research: NR4A nuclear receptor ligands as inducers of ferroptosis and immune modulation in colon cancer

Article Title: Orphan nuclear receptor 4A (NR4A) ligands induce ferroptosis and modify immune function in colon cancer

Article References: Oany, A. R., Upadhyay, S., Wright, G. A., Farkas, E., Sivaram, G., Tsui, W. N. T., Hailemariam, A., Chen, S.-H., & Safe, S. (2026). Orphan nuclear receptor 4A (NR4A) ligands induce ferroptosis and modify immune function in colon cancer. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03369-4

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03369-4

Keywords: NR4A1, NR4A2, ferroptosis, colon cancer, GPX4, DIM-3,5 ligands, reactive oxygen species, tumor microenvironment, CD8 T cells, myeloid-derived suppressor cells, immunotherapy, nuclear receptors