Letter to the Editor: Spinal IL-33/ST2 blockade for gallbladder carcinoma pain - balancing central analgesia with systemic tumor immune microenvironment risks

Abstract

Recently, Ge et al published a study in the World Journal of Gastrointestinal Oncology elucidated the critical role of the spinal interleukin-33/suppression of tumorigenicity 2 (ST2) signaling pathway in gallbladder carcinoma (GBC)-induced chronic pain, providing a highly promising non-opioid analgesic target for advanced refractory cancer pain. We highly commend their establishment of a clinically relevant orthotopic GBC pain model and their profound insights into central sensitization mechanisms. However, before advancing this promising target to clinical translation, the complex “double-edged sword” effects of systemic targeted delivery within tumor biology and systemic immunology must be critically evaluated. This letter highlights that the immunodeficient nude mouse model utilized in the original study fundamentally masks the risk of compromising CD8+ T cell-mediated intrinsic anti-tumor immunity caused by systemic interleukin-33/ST2 blockade. Furthermore, the potential impact of targeted interventions on local dense stromal remodeling in GBC, along with the unknown activation of tumor-intrinsic ST2 signaling, could lead to unexpected pro-tumorigenic consequences. Therefore, we strongly recommend that future translational studies be conducted in immunocompetent syngeneic mouse models, performing head-to-head comparisons between intrathecal targeted delivery and systemic administration. Additionally, utilizing spatial transcriptomics or multiplex immunohistochemistry to clarify the precise cellular localization of ST2 is essential to bridge the gap between neurobiological analgesic mechanisms and the global tumor immune microenvironment.

Key Words: Gallbladder carcinoma; Visceral cancer pain; Interleukin-33/suppression of tumorigenicity 2 signaling pathway; Tumor immune microenvironment; Systemic administration; Translational medicine; Intrathecal delivery; Neuroinflammation

Core Tip: This article highlights a critical translational blind spot in targeting the spinal interleukin-33/suppression of tumorigenicity 2 axis for gallbladder carcinoma-induced pain. While local blockade exhibits analgesic efficacy, systemic administration risks impairing CD8+ T cell-mediated intrinsic anti-tumor immunity - a critical risk fundamentally masked by the original study’s use of athymic nude mice. Furthermore, potential tumor-intrinsic suppression of tumorigenicity 2 activation and stromal remodeling necessitate extreme caution. We strongly advocate that future evaluations utilize immunocompetent syngeneic models to compare intrathecal vs systemic delivery, aiming to safely bridge the gap between analgesic mechanisms and the tumor immune microenvironment.

TO THE EDITOR

We read with great interest the insightful study by Ge et al[1] recently published in the World Journal of Gastrointestinal Oncology, which elucidated the impact of interleukin-33 (IL-33)/suppression of tumorigenicity 2 (ST2) signaling activation on gallbladder carcinoma (GBC)-induced chronic pain.

THE URGENT CLINICAL NEED FOR TARGETED NON-OPIOID ANALGESIA

GBC is the most common malignant tumor of the biliary tract. According to the latest GLOBOCAN statistics, there are approximately 115000 new cases and 85000 deaths from GBC annually worldwide, presenting a particularly high disease burden in Asia[2]. Due to its insidious onset and highly aggressive nature, most patients have already lost the opportunity for surgical resection at the time of diagnosis. Epidemiological and clinical data indicate that more than 50% of patients with advanced GBC suffer from severe chronic abdominal pain[3-5], which is often persistent and excruciating. Current clinical pain management primarily relies on the World Health Organization three-step analgesic ladder; however, studies demonstrate that up to 40% to 50% of patients with advanced cancer still fail to achieve adequate pain relief[6].

Furthermore, the long-term, high-dose administration of opioids is frequently accompanied by tolerance, respiratory depression, and severe gastrointestinal adverse effects. Given the high incidence of pain in GBC patients and the inherent limitations of current therapies, identifying precise, non-opioid analgesic targets has emerged as an urgent unmet need in translational oncology. By revealing the critical role of the spinal IL-33/ST2 signaling pathway in pain maintenance, the study by Ge et al[1] not only deepens our mechanistic understanding of visceral cancer pain but also provides a highly promising molecular target for clinical translational therapy.

BREAKTHROUGHS IN ORTHOTOPIC MODELING AND CENTRAL SENSITIZATION

In this regard, Ge et al[1] are to be highly commended for their rigorous and forward-looking study design. The most prominent highlight of their work is the profound introduction of the neuroimmune crosstalk perspective into the mechanistic exploration of visceral cancer pain.

Notably, rather than relying on traditional ectopic subcutaneous models[7], the team successfully established a highly clinically relevant orthotopic GBC pain model. This model maximally recapitulates the local anatomical microenvironment and specific visceral innervation of the gallbladder, thereby conferring exceptionally high pathophysiological fidelity when investigating visceral pain mechanisms.

In terms of mechanistic depth, the study comprehensively delineates the molecular cascade from neuroimmune crosstalk to hyperalgesia. Solid in vivo experiments confirmed that the activation of spinal IL-33/ST2 signaling in the GBC state not only drives the overactivation of astrocytes and microglia but also triggers the subsequent cascaded release of downstream pro-inflammatory mediators[1]. These inflammatory factors profoundly reshape the excitability of nociceptive projection neurons in the spinal dorsal horn, ultimately inducing central sensitization, which serves as the core mechanism mediating persistent hyperalgesia in advanced stages.

From a translational perspective, this complete evidence chain holds significant theoretical guidance value. Currently, interventions targeting the IL-33/ST2 axis have demonstrated favorable safety and druggability in clinical trials for other inflammatory diseases. For instance, monoclonal antibodies targeting IL-33 (e.g., itepekimab) or its receptor ST2 (e.g., astegolimab) have shown positive progress in phase II/III clinical evaluations for diseases such as severe asthma[8]. The findings of Ge et al[1] provide a solid scientific rationale that, by leveraging these existing biologics, targeted blockade of the spinal IL-33/ST2 signaling pathway could emerge as a novel and precise intervention strategy for opioid-refractory pain in advanced GBC, potentially breaking through the bottlenecks of the current three-step analgesic ladder.

THE “DOUBLE-EDGED SWORD” AND BLIND SPOTS OF SYSTEMIC BLOCKADE

Before bringing this promising pain target into the clinic, researchers must draw a hard line between its spinal effects and its broader systemic impact. Inside the spinal cord, turning on IL-33/ST2 fuels neuroinflammation and drives pain sensitization. Outside the spine, however, the exact same pathway shapes the global tumor immune microenvironment (TIME). If we ignore these location-specific differences, we risk completely misjudging the therapy’s true clinical value. Ge et al[1] made a compelling case for local spinal blockade of the IL-33/ST2 pathway to ease cancer pain. The practical challenge, however, lies in drug delivery. In real-world clinical settings, biologic agents targeting this axis are almost always given systemically[1]. When we view this systemic approach through the lens of recent hepatobiliary and gastrointestinal oncology research, a major concern emerges. Moving from local to systemic administration exposes three distinct oncological blind spots that demand immediate investigation.

Firstly, systemic targeted delivery inevitably interferes with the complex interplay of global anti-tumor immunity, a risk that the animal model in the original study fails to effectively evaluate. Indeed, effective central analgesia can reverse stress-induced immunosuppression; however, at the systemic level, IL-33 acts as a crucial anti-tumor “alarmin”. As repeatedly confirmed by multiple immune studies in hepatobiliary tumors (e.g., models of hepatocellular carcinoma), the release of endogenous IL-33 significantly promotes the expansion of CD8+ T cells and their production of interferon-gamma, thereby potently suppressing tumor growth. Systemic blockade of IL-33/ST2 signaling solely for the purpose of analgesia highly risks accelerating tumor immune evasion[9,10]. Unfortunately, the authors utilized immunodeficient nude mice to establish the orthotopic GBC pain model. Because this model congenitally lacks a mature T-cell network, it fundamentally masks the potential disruption of CD8+ T cell-mediated intrinsic anti-tumor immunity caused by IL-33 blockade, making it impossible to evaluate the overall oncological safety of this analgesic strategy.

Secondly, the assessment of local stromal remodeling in the original study is somewhat insufficient. GBC is pathologically characterized by extremely dense desmoplasia. Given the limited direct evidence in GBC-specific models, extrapolating from recent literature on related digestive system tumors suggests that IL-33 may potentially drive the activation of cancer-associated fibroblasts and induce type 2 immunity-mediated stromal remodeling. Whether systemic IL-33/ST2 blockade could potentially attenuate this pro-tumorigenic fibrotic barrier to improve drug penetration, or conversely disrupt the existing stromal physical homeostasis to promote local GBC cell invasion, remains a critical unresolved question in evaluating the overall survival benefit of this therapy[11,12].

Finally, and most crucially, the issue of spatial heterogeneity: We must remain vigilant regarding the activation of tumor-intrinsic ST2 signaling. Do GBC epithelial cells intrinsically express ST2? Taking cholangiocarcinoma - another biliary tract malignancy—as an example, studies by Yangngam et al[13] and recent mechanistic explorations suggest that extracellular IL-33, upon binding to its receptor ST2, might activate downstream nuclear factor kappa-light-chain-enhancer of activated B cells and glycogen synthase kinase-3 beta/mitogen-activated protein kinase signaling pathways, thereby potentially promoting the proliferation and invasion of biliary malignant cells. If GBC cells similarly exhibit high ST2 expression, systemic blockade would achieve the dual benefits of both analgesia and tumor suppression; conversely, if ST2 expression is restricted to protective immune cells, systemic administration would be highly detrimental. Therefore, we strongly recommend that the authors utilize multiplex immunohistochemistry or spatial transcriptomics in future translational studies to elucidate the precise spatial expression profile of ST2 within the primary GBC lesion[14].

A CONSTRUCTIVE FRAMEWORK FOR SAFE TRANSLATIONAL THERAPY

Therefore, to safely and effectively advance this promising analgesic target into the clinic, future translational research urgently needs to conduct targeted supplementary work to address the aforementioned oncological blind spots.

Firstly, to address the immunosuppressive risks potentially induced by systemic administration, future evaluations of orthotopic GBC pain must be conducted in immunocompetent syngeneic models. Based on this intact immune network, we strongly advocate for a head-to-head comparison between intrathecal delivery and conventional systemic administration. Given that macromolecular monoclonal antibodies rarely penetrate the blood-brain/blood-spinal cord barrier, micro-dose intrathecal targeted delivery can not only bypass this pharmacokinetic bottleneck but also elegantly achieve the “spatial decoupling” of central analgesic effects from peripheral innate immune regulation. Synchronous monitoring of the activity changes of effector cells, such as CD8+ T cells, in the systemic circulation and draining lymph nodes under these two administration routes will provide decisive in vivo experimental evidence for the future development of highly efficient delivery vectors targeting the central nervous system (e.g., nano-sustained release systems)[15].

Secondly, to address the lack of assessment regarding target spatial heterogeneity and stromal remodeling, clarifying the precise cellular localization of ST2 receptors in GBC tissues is the key to breaking the bottleneck. We urge researchers to utilize multiplex immunohistochemistry or spatial transcriptomics techniques to comprehensively map the spatial expression profile of ST2 on tumor epithelial cells, cancer-associated fibroblasts, and infiltrating immune cells in both human clinical samples and murine orthotopic models. Simultaneously, we recommend synchronously evaluating the evolution of histological features, such as primary lesion desmoplasia, following targeted intervention. Only by thoroughly elucidating the spatial distribution and stromal remodeling functions of ST2 at the molecular and cellular levels can we accurately predict the overall survival benefit of targeting this pathway[13,16].

Admittedly, this commentary relies heavily on indirect evidence and cross-tumor extrapolation, which is a natural limitation of our analysis. To truly settle this debate, future work must move beyond assumptions. Researchers need to map the precise spatial distribution of ST2 and observe the actual effects of systemic IL-33 blockade on the TIME. Crucially, all of this must be tested directly inside GBC-specific, immunocompetent models.

Despite these necessary next steps, the original findings of Ge et al[1]. Still provide an invaluable neurobiological perspective for the management of advanced visceral cancer pain. If the gap between central analgesic mechanisms and the global TIME can be further bridged in subsequent translational studies, this target will undoubtedly demonstrate a more robust and broader prospect for clinical application.