Dual-faced CXCL5 holds the key to unlocking immunotherapy in obese pancreatic cancer

Abstract

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest malignancies, characterized by a profoundly immunosuppressive tumor microenvironment and resistance to immunotherapy. Obesity, a modifiable risk factor that increases PDAC incidence, exacerbates this immune evasion through metabolic inflammation and adipokine-driven signaling. Recent studies have implicated CXC chemokines, particularly CXCL5, as central mediators in shaping the immune landscape of PDAC. In a pivotal study, Walsh et al delineated a novel mechanism wherein adipocyte-derived cytokines (interleukin-1β and tumor necrosis factor) induce tumor-derived CXCL5 expression, thereby promoting myeloid-driven immunosuppression in obese PDAC models. Their findings demonstrated that CXCL5 ablation enhances CD8⁺ T-cell infiltration yet paradoxically increases monocytic myeloid-derived suppressor cell accumulation and arginase-1 expression, underscoring the complexity of chemokine signaling. Notably, only combinatorial targeting of CXCL5 and programmed cell death protein-1 yields therapeutic benefit, emphasizing the necessity of multiaxis interventions. This commentary synthesizes the mechanistic insights and translational implications of these findings, highlighting CXCL5 as a pivotal node linking metabolic dysfunction to immune resistance and a promising target for combinatorial immunotherapy in PDAC.

Pancreatic ductal adenocarcinoma (PDAC) persists as among the deadliest malignancies, exhibiting a 5-year survival rate consistently under 10%, primarily due to its aggressive biological nature and resistance mechanisms derived from its intricate tumor microenvironment (TME). This immunosuppressive milieu features extensive desmoplasia, inadequate vascularization, myeloid-derived suppressor cells (MDSCs) infiltration, exclusion of effector T lymphocytes, and compromised tumor-associated macrophage function, collectively hampering cytotoxic immune responses and neutralizing immune checkpoint inhibitor efficacy. Obesity, an epidemiologically confirmed and modifiable risk factor, elevates PDAC incidence by 20–50% and intensifies immune evasion through persistent inflammation, metabolic aberrations, and adipokine-mediated oncogenic pathway activation. Components secreted from adipose tissue, including inflammatory cytokines, chemokines, and metabolic byproducts, establish pathological communication networks between tumor cells, stromal elements, and immune populations, thus facilitating therapeutic resistance and disease advancement. Recent research has elucidated the significance of various CXC chemokine signaling pathways, notably CXCL1/2/5-CXCR1/2, in driving pancreatic cancer progression via TME restructuring and diminishing immunotherapeutic efficacy. Nevertheless, the specific mechanisms connecting adipocyte-driven signaling to treatment failure remain inadequately defined.

In this context, the study by Walsh et al¹ makes significant strides in addressing the knowledge gap by investigating the role of tumor-derived CXCL5 in modulating immune infiltration and therapy response in obese PDAC models. Their work not only elucidates a novel chemokine-mediated axis of immune suppression but also proposes an innovative combinatorial therapeutic approach that significantly enhances the efficacy of anti-programmed cell death protein-1 (PD-1) therapy. These findings establish a potential framework for translational advancement in this notoriously treatment-resistant malignancy.

CXCL5 belongs to the CXC chemokine family and is characterized by the conserved glutamic acid-leucine-arginine motif, a structural feature essential for its angiogenic properties and immunomodulatory functions. This chemokine is expressed by diverse cell types including immune cells (macrophages, eosinophils, dendritic cells) and non-immune cells (fibroblasts, mesothelial cells, tumor-associated stromal cells). CXCL5 exerts its biological effects primarily through binding to CXCR1/2, G-protein coupled receptors that activate downstream signaling pathways including PI3K/AKT, NF-κB, and MAPK cascades. The biological consequences of CXCL5-CXCR1/2 signaling are multifaceted, mediating neutrophil and MDSCs recruitment, angiogenesis, and epithelial-mesenchymal transition, all processes that contribute significantly to tumor progression and immune evasion. The overexpression of CXCL5 has been associated with poor prognosis, metastasis, and resistance to therapy in multiple cancer types, including hepatocellular carcinoma, breast cancer, and pancreatic cancer.² Recent studies highlight its dual role in shaping immunosuppressive TME by recruiting CXCR2⁺ neutrophils and MDSCs,^{3 4} while also driving angiogenesis via VEGF-A upregulation.⁵ Emerging therapeutic strategies focusing specifically on CXCL5 include the development of neutralizing monoclonal antibodies against CXCL5, which offer more selective targeting compared with broad receptor antagonism. Such CXCL5-specific approaches may provide distinct therapeutic advantages, as demonstrated by Walsh et al’s findings that CXCL5 depletion alone produces unique immune effects that differ from broader CXCR1/2 inhibition. These CXCL5-targeted strategies position selective chemokine neutralization as a promising approach to modulate specific aspects of the immune microenvironment.

In parallel, broader CXCR1/2 receptor antagonism represents a different therapeutic approach with distinct mechanisms and outcomes. CXCR2 antagonists (eg, SCH-527123) and small molecule inhibitors have shown promise in preclinical models by reducing multiple CXCR1/2 ligands’ effects simultaneously, including CXCL1, CXCL2, CXCL5, and CXCL8.^{6 7} Clinically, CXCR1/2 inhibitors such as Reparixin are under clinical evaluation in combination with chemotherapy or immune checkpoint blockers (NCT02001974), demonstrating the translational potential of receptor-level intervention.⁸ However, broad receptor inhibition may produce different immune outcomes compared with selective ligand targeting, as it simultaneously blocks multiple chemokine pathways that may have distinct or even opposing functions in the TME. The distinction between CXCL5-specific targeting and broader CXCR1/2 inhibition is critical for therapeutic development, as these approaches may yield different efficacy profiles and safety considerations. Understanding these differences will be essential for optimizing treatment strategies and patient selection in future clinical applications.

Walsh et al employ a rigorous translational framework to elucidate the role of CXCL5 in PDAC progression. Using conditioned media from human peripancreatic adipose tissue, the authors demonstrate that adipocyte-derived interleukin (IL)-1β and tumor necrosis factor (TNF) synergistically induce CXCL5 secretion from PDAC cells, a finding corroborated by correlative analyses of patient proteogenomic data from the CPTAC cohort. CRISPR-Cas9-mediated CXCL5 knockout (KO) in murine K8484 PDAC cells enabled orthotopic tumor studies in diet-induced obese mice, a model that recapitulates the metabolic and inflammatory hallmarks of human obesity. Flow cytometry revealed that CXCL5 ablation increased CD8⁺ T-cell infiltration, yet paradoxically amplified immunosuppressive Ly6C^hi monocytic MDSCs and intratumoral arginase-1 expression, a marker of myeloid-mediated immune suppression. While CXCL5-KO tumors alone showed no reduction in growth, combining CXCL5 depletion with anti-PD-1 therapy significantly attenuated tumor burden. These findings position CXCL5 as a dual regulator of immune evasion: it restricts T-cell infiltration while indirectly sustaining an immunosuppressive myeloid landscape, necessitating combinatorial targeting to unlock therapeutic efficacy.

The mechanistic insights from this study advance our understanding of obesity-cancer interactions through several key observations: first, it establishes a direct link between adipose inflammation and tumor chemokine production, showing how IL-1β and TNF from adipocytes stimulate CXCL5 expression in tumor cells, connecting metabolic dysfunction to immune modulation in PDAC. This clarifies how obesity influences tumor chemokine profiles beyond metabolic effects. Second, the research challenges conventional views of CXCR1/2 ligands as strictly protumorigenic. While CXCL5 deletion enhances CD8⁺ T-cell infiltration, it paradoxically increases immunosuppressive MDSCs and arginase-1⁺ cells, suggesting CXCL5 may differentially affect myeloid cell polarization by altering chemokine gradients. This functional specificity implies selective targeting of specific chemokines might produce distinct outcomes compared with broader receptor inhibition. Third, the study highlights chemokine signaling’s context-dependence under obesogenic conditions, where high-fat diets amplify CXCL5’s immunosuppressive effects, explaining why CXCL5-deficient tumors required anti-PD-1 co-therapy for efficacy. Fourth, increased PD-1 expression on CD8⁺ T cells in CXCL5-KO tumors reveals a previously unknown connection between CXCL5 signaling and T-cell exhaustion, providing rationale for combining CXCL5 targeting with checkpoint blockade, as the enhanced T-cell infiltration from CXCL5 ablation may be counteracted by increased exhaustion without PD-1 inhibition.

However, several limitations should be acknowledged. First, the study’s exclusive focus on an obese mouse model limits the ability to extrapolate findings to lean physiological contexts. Obesity induces systemic inflammation and alters myeloid cell differentiation, which may potentiate the immunosuppressive effects of CXCL5. Consequently, it remains unclear whether comparable mechanisms are active in non-obese conditions. Future studies incorporating both lean and obese animal models would provide valuable insights into the obesity-specificity of CXCL5-mediated immune regulation. Second, the use of bulk RNA sequencing and proteomic profiling restricts the resolution needed to capture cellular heterogeneity within the tumor microenvironment. Single-cell transcriptomic approaches would provide greater clarity regarding the cellular origin of CXCL5, distinguishing whether its expression is confined to tumor cells or also contributed by stromal elements such as cancer-associated fibroblasts or adipocytes. Such analyses could also shed light on the dynamic changes in immune cell phenotypes following CXCL5 ablation, potentially revealing transition states between pro-inflammatory and anti-inflammatory myeloid populations. Third, although the study demonstrates increased arginase-1 expression in CXCL5-deficient tumors with enhanced CD8⁺T cell infiltration, the cellular source of arginase-1 requires further clarification. While arginase-1 is predominantly expressed by myeloid cell populations (particularly monocytic MDSCs) in PDAC models, recent evidence suggests that some CD8⁺T cell subsets are also capable of producing arginase-1.^{9 10} Given the increased CD8⁺T cell infiltration in CXCL5-KO tumors, the elevated arginase-1 levels may reflect contributions from both T cells and, more likely, from the expanded myeloid compartment/monocytic MDSCs. This overlap introduces ambiguity into the interpretation of immunophenotyping results. Further studies using lineage-specific reporter systems or single-cell protein profiling would help resolve the cellular sources of arginase-1 and other immune regulatory molecules in the CXCL5-modulated TME. Finally, the clinical relevance of CXCL5 inhibition remains speculative in the absence of translational validation. The lack of human clinical trials or patient-derived xenograft models leaves unresolved questions regarding the feasibility, safety, and therapeutic efficacy of CXCL5-targeted interventions. Development of humanized mouse models incorporating patient-derived PDAC and adipose tissue would provide a more clinically relevant platform for testing CXCL5-directed therapies.

From a clinical perspective, this study positions CXCL5 as a promising therapeutic target for converting immunologically “cold” PDAC tumors into more responsive states for immunotherapy. The requirement for co-administration of CXCL5 depletion with anti-PD-1 therapy parallels observations from other studies on CXCR1/2 ligands, where monotherapies alone frequently fail to reverse T-cell exhaustion, emphasizing the necessity of multimodal therapeutic strategies in PDAC. Several approaches for targeting the CXCL5 axis merit further investigation, including development of monoclonal antibodies specifically targeting CXCL5 to provide a more selective approach compared with receptor antagonism; compounds targeting the signaling pathways responsible for CXCL5 induction (eg, NF-κB or STAT3 inhibitors) to suppress CXCL5 secretion at the source; engineering bispecific antibodies that simultaneously target CXCL5 and other immunosuppressive factors to streamline combination approaches; and metabolic interventions targeting obesity-driven inflammation, as strategies addressing metabolic dysregulation might indirectly modulate CXCL5 expression. Furthermore, the functional crosstalk between CXCL5 and other CXCR2 ligands, including CXCL1 and CXCL8, warrants detailed analysis, as simultaneous targeting may produce synergistic immunomodulatory effects, with the study’s finding of potential heterodimer formation between CXCL1 and CXCL5 particularly intriguing, suggesting a higher-order regulation of chemokine activity that could explain variable results observed with single-ligand targeting strategies.

This study also prompts broader inquiry into the role of obesity in shaping chemokine networks and immunotherapy response. For example, it remains unclear whether adipokines beyond IL-1β and TNF contribute to the regulation of CXCL5 expression. Recent studies have implicated leptin, adiponectin, and various lipid metabolites in modulating tumor immunity, suggesting that the obesity-cancer interface likely involves multiple converging pathways.¹¹ The potential for dietary modification or metabolic interventions to attenuate CXCL5-mediated immunosuppression in obese patients represents an important avenue for future translational research. The study’s findings suggest that lifestyle interventions targeting obesity could potentially modulate the chemokine landscape in PDAC, offering a complementary strategy to pharmacological approaches. Indeed, emerging evidence indicates that dietary restriction and exercise can favorably reshape the immune microenvironment in various tumor types, potentially enhancing responsiveness to immunotherapy.^{12 13} From a biomarker perspective, circulating levels of CXCL5 and related inflammatory mediators might serve as predictive indicators of immunotherapy response in obese patients with PDAC. Longitudinal assessment of these markers during treatment could provide valuable insights into dynamic changes in the tumor immune landscape and guide therapeutic decision-making.

In conclusion, Walsh et al present robust evidence establishing tumor-derived CXCL5 as a pivotal mediator of immune evasion in obesity-associated PDAC. Their work elucidates a mechanistic link between adipose tissue inflammation and chemokine-mediated suppression of antitumor immunity, thereby identifying a novel targetable pathway for augmenting T-cell responses. While key challenges persist, particularly in optimizing CXCL5 inhibition strategies and managing compensatory myeloid cell responses, this research constitutes a meaningful step forward in developing precision immunotherapy approaches for PDAC. Looking ahead, the integration of chemokine pathway modulation with metabolic interventions may yield more sustained and effective therapeutic outcomes for this notoriously treatment-refractory cancer.