In the intricate battlefield of cancer immunology, the tumour microenvironment plays a pivotal role in determining the fate of immune responses. Tumours often create a hostile milieu that subverts immune surveillance and facilitates immune escape, posing formidable challenges for effective immunotherapy. Among the myriad of factors shaping this microenvironment, lactic acid accumulation has emerged as a critical driver in promoting tumour immune evasion. Despite its recognized importance, the precise molecular mechanisms by which lactic acid exerts immunosuppressive effects, particularly on T cell subsets, have remained shrouded in mystery—until now.
A groundbreaking study by Xu et al. illuminates the previously elusive pathways underpinning lactic acid–mediated immunosuppression in tumours, revealing the central role of the transcription factor MondoA and its downstream effector, the thioredoxin-interacting protein (TXNIP). Their findings herald a paradigm shift in understanding how metabolic perturbations within the tumour microenvironment dysregulate immune responses, offering novel avenues to reinvigorate anticancer immunity.
At the heart of this discovery lies the observation that both regulatory T (Treg) cells, known for their immunosuppressive function, and cytotoxic CD8+ T cells, which are tasked with tumour cell elimination, respond to lactic acid by upregulating the MondoA-TXNIP axis. MondoA, a glucose-sensing transcription factor, orchestrates cellular metabolic responses, and its induction in response to lactic acid suggests a sophisticated cellular adaptation mechanism. By driving TXNIP transcription, MondoA modulates key metabolic and signaling pathways within these T cells, ultimately influencing their functional fate.
The dichotomous role of MondoA in Tregs versus CD8+ T cells is particularly striking. In Treg cells, MondoA expression augments their already immunosuppressive phenotype, fortifying the tumour’s immune evasion shield. Conversely, in CD8+ T cells, the presence of MondoA in a lactic acid–rich environment undermines their cytotoxic capabilities by impairing glucose uptake and glycolytic activity—metabolic processes essential for effective T cell activation and function.
The researchers demonstrated that genetic ablation of MondoA in Treg cells cripples their immunosuppressive capacity, potentially tipping the balance toward antitumour immunity. More importantly, the loss of MondoA in CD8+ T cells restores their ability to uptake glucose and sustain glycolysis, thereby rescuing their cytotoxic functions even under the metabolic stress imposed by lactic acid accumulation. This metabolic rewiring reactivates CD8+ T cell responses that are typically stifled within the tumour microenvironment, making MondoA an attractive target for therapeutic intervention.
Mechanistic interrogation into how lactic acid signals through the MondoA-TXNIP pathway unveiled the involvement of sentrin/SUMO-specific protease 1 (SENP1). SENP1 appears to be indispensable in mediating lactic acid–driven activation of MondoA and subsequent TXNIP expression. This suggests a tightly regulated post-translational modification axis whereby SUMOylation dynamics modulate transcriptional programs central to T cell metabolism and function. The SENP1-dependent induction of the MondoA-TXNIP axis provides an additional layer of complexity and regulation, underscoring the sophisticated interplay between metabolic cues and immune signaling pathways.
Further analyses revealed that this MondoA-TXNIP axis suppresses T cell receptor (TCR) and CD28 co-stimulatory signals, which are critical for full T cell activation. By impairing these signaling cascades, lactic acid effectively blunts CD8+ T cell immunogenicity. Restoration of glucose metabolism following MondoA inhibition reactivates these essential pathways, paving the way for robust cytotoxic T cell responses capable of tumour eradication.
The translational implications of these findings are profound. Therapeutic targeting of the MondoA-TXNIP axis holds tremendous promise in revitalizing antitumour immunity, particularly in tumours characterized by high lactic acid concentrations. Importantly, the study demonstrated that pharmacologic or genetic disruption of this axis not only enhanced T cell responses but also synergized effectively with immune checkpoint blockade therapy, specifically anti-PD-1 antibodies, to amplify therapeutic efficacy in colorectal cancer models.
This synergy underscores the potential of combinatorial strategies that integrate metabolic modulation with immunotherapy, thus overcoming resistance mechanisms that have plagued many cancers. By dismantling the metabolic barricades erected by lactic acid through MondoA-TXNIP inhibition, the immune system can be re-empowered to mount more vigorous and sustained anticancer responses.
From a broader perspective, the elucidation of the MondoA-TXNIP axis as a metabolic immune checkpoint provides a conceptual framework for future interventions aimed at recalibrating immune cell metabolism in cancer. Beyond Tregs and CD8+ T cells, it is conceivable that similar mechanisms might operate in other immune subsets, further extending the therapeutic reach of targeting metabolic transcriptional networks.
Moreover, the identification of SENP1 as a crucial mediator in this pathway opens new investigative pathways exploring the role of SUMOylation in immune metabolism and function. This could unveil additional targets and regulatory nodes amenable to precise manipulation, enhancing the specificity and efficacy of metabolic immunotherapies.
The study’s relevance extends well beyond colorectal cancer, as the authors demonstrated consistent benefit across multiple cancer types. This suggests that targeting the MondoA-TXNIP axis might represent a universality in overcoming lactic acid–induced immunosuppression, broadening the horizon for impactful therapies across diverse tumour contexts.
In the face of rising clinical challenges posed by the immunosuppressive tumour microenvironment, this research provides a beacon of hope. By intricately dissecting the molecular crosstalk between metabolic stress signals and immune cell programming, it equips the scientific and medical communities with innovative tools to tip the scales in favor of tumor eradication.
As immune-oncology continues to evolve, strategies that integrate metabolic insights with immunotherapeutic approaches will likely transform patient outcomes. The MondoA-TXNIP axis emerges not merely as a molecular target but as a conceptual lynchpin linking metabolism, immune regulation, and cancer therapy.
Future investigations will undoubtedly delve deeper into the nuances of this axis, exploring potential side effects, the dynamics of MondoA-TXNIP modulation in vivo, and the translational feasibility of such interventions. Clinical trials based on these findings could usher in a new era of personalized metabolic immunotherapy, tailoring treatments to the unique metabolic landscapes of individual tumours.
In conclusion, this landmark study elucidates a fundamental mechanism by which lactic acid orchestrates immune suppression in the tumour microenvironment through the MondoA-TXNIP pathway. It reveals therapeutic vulnerabilities that, when exploited, can restore the antitumour potency of immune cells and complement existing immunotherapies to achieve superior clinical benefits. The discovery paves the way for next-generation cancer treatments that reconcile metabolic control with immune activation, charting a promising path forward in the ongoing battle against cancer.
Subject of Research: Tumour immunometabolism; immune evasion mechanisms; T cell metabolic regulation; lactic acid effects in tumour microenvironment
Article Title: Targeting MondoA–TXNIP restores antitumour immunity in lactic-acid-induced immunosuppressive microenvironment
Article References:
Xu, N., Zhu, Y., Han, Y. et al. Targeting MondoA–TXNIP restores antitumour immunity in lactic-acid-induced immunosuppressive microenvironment. Nat Metab (2025). https://doi.org/10.1038/s42255-025-01347-1
Image Credits: AI Generated
