Highlights
- Identification of the adipocyte-derived metabolite 12,13-DiHOME as a primary driver of immune evasion in pancreatic ductal adenocarcinoma (PDAC).
- Elucidation of a novel PPARγ-mediated ferritinophagy pathway that sensitizes tumour-associated neutrophils (TANs) to ferroptosis.
- Discovery that ferroptotic TANs release CXCL2, which directly suppresses the recruitment and effector function of CD8+ T cells.
- Validation of targeting the 12,13-DiHOME/CXCR2 axis as a therapeutic strategy to restore anti-tumour immunity in adipocyte-rich PDAC microenvironments.
Background
Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal malignancies, characterized by a dense, desmoplastic stroma and a profoundly immunosuppressive tumour microenvironment (TME). A hallmark of PDAC progression is its frequent invasion into the peripancreatic adipose tissue. While the role of cancer-associated fibroblasts and myeloid-derived suppressor cells (MDSCs) is well-documented, the influence of tumour-infiltrating adipocytes (TIAs) on the TME remains poorly understood.
Adipose tissue is not merely an energy reservoir but a dynamic endocrine organ that secretes adipokines and lipid metabolites. In the context of PDAC, the metabolic dialogue between TIAs and immune cells suggests a complex immunometabolic circuit. Understanding how these interactions subvert CD8+ T cell immunity is critical for developing next-generation immunotherapies, particularly for patients with high visceral adiposity or peripancreatic fat infiltration.
Key Content
The Clinical Significance of Tumour-Infiltrating Adipocytes (TIAs)
Recent evidence from a retrospective cohort of 121 PDAC patients demonstrates that high TIA abundance is a significant independent predictor of poor overall survival. Histological analysis reveals that tumours with high TIA counts are characterized by reduced infiltration of Granzyme B+ and CD8+ T cells, suggesting a localized state of immune exclusion or suppression. These clinical findings were corroborated using the Kras(LSL-G12D/+);Trp53(LSL-R172H/+);Pdx1-Cre (KPC) mouse model, where adipocyte-enriched tumours exhibited accelerated growth and diminished anti-tumour immune responses.
Metabolic Profiling: The Role of 12,13-DiHOME
Integrating tumour metabolomics with bulk and single-cell RNA sequencing (scRNA-seq), researchers identified 12,13-dihydroxy-9Z-octadecenoic acid (12,13-DiHOME) as a key metabolite enriched in TIA-heavy regions. 12,13-DiHOME, a linoleic acid metabolite, was found to be specifically secreted by adipocytes within the TME. Unlike systemic metabolic markers, the local concentration of 12,13-DiHOME serves as a paracrine signal that specifically targets tumour-associated neutrophils (TANs).
Mechanistic Insight: PPARγ-Mediated Ferritinophagy and Ferroptosis
The study utilized neutrophil-specific PPARγ conditional knockout mice (PPARγ(fl/fl)-S100A8(cre)) to demonstrate that 12,13-DiHOME acts as a ligand for PPARγ in TANs. Activation of PPARγ upregulates the expression of NCOA4, a key cargo receptor for ferritinophagy. This process leads to the autophagic degradation of ferritin, releasing intracellular unstable iron (Fe2+).
The resulting iron overload, combined with 12,13-DiHOME-induced lipid peroxidation, triggers TANs to undergo ferroptosis—a form of regulated cell death characterized by iron-dependent lipid peroxide accumulation. Interestingly, this study highlights that TANs in PDAC do not simply disappear; rather, their ferroptotic state is a functional transition that alters the TME chemical landscape.
CXCL2: The Bridge to T Cell Suppression
As TANs undergo 12,13-DiHOME-induced ferroptosis, they significantly increase the secretion of the chemokine CXCL2. While CXCL2 is typically associated with neutrophil recruitment, in the PDAC TME, it functions as a potent inhibitor of CD8+ T cell activity. High levels of CXCL2 create a chemotactic barrier or directly interfere with T cell receptor (TCR) signaling, leading to reduced interferon-gamma (IFN-γ) and TNF-α production by CD8+ T cells. Neutralization of CXCL2 or the use of CXCR2 antagonists (the receptor for CXCL2) successfully restored CD8+ T cell infiltration and attenuated tumour progression in orthotopic models.
Expert Commentary
The identification of the 12,13-DiHOME/PPARγ/TAN axis represents a shift in our understanding of the PDAC microenvironment. Historically, neutrophils were viewed as either N1 (anti-tumour) or N2 (pro-tumour) based on cytokine profiles. This research adds a metabolic layer to this plasticity, suggesting that the “state” of the neutrophil (ferroptotic vs. viable) is a major determinant of its immunomodulatory function.
From a clinical perspective, these findings are particularly relevant given the high prevalence of obesity and metabolic syndrome in PDAC patients. The use of PPARγ antagonists or CXCR2 inhibitors (such as AZD5069, currently in clinical trials) could provide a precision medicine approach for the subset of patients with high peripancreatic fat invasion. However, a significant controversy remains regarding the systemic versus local effects of PPARγ modulation, as PPARγ is also involved in systemic insulin sensitivity and adipocyte differentiation.
Conclusion
This study defines a specific immunometabolic circuit where TIA-derived 12,13-DiHOME subverts CD8+ T cell immunity through a PPARγ-ferritinophagy-TAN ferroptosis pathway. By promoting the release of CXCL2 from dying neutrophils, adipocytes effectively create an “immune-cold” environment. Future research should focus on whether these metabolic pathways can be detected non-invasively via liquid biopsies and if combining CXCR2 inhibitors with standard-of-care chemotherapy can overcome the resistance typically seen in adipocyte-rich PDAC.
References
- Luo Y, et al. Tumour-infiltrating adipocyte-derived 12,13-DiHOME subverts CD8+ T cell immunity in pancreatic ductal adenocarcinoma by promoting PPARγ-mediated ferritinophagy and tumour-associated neutrophil ferroptosis. Gut. 2026; PMID: 42209194.
- Hingorani SR, et al. Trp53R172H and KrasG12D cooperate to promote chromosomal instability and widely metastatic pancreatic ductal adenocarcinoma in mice. Cancer Cell. 2004; PMID: 15144955.
- Stockwell BR, et al. Ferroptosis: A Regulated Cell Death Nexus Linking Metabolism, Redox Biology, and Disease. Cell. 2017; PMID: 28985560.