Tumor acidity emerges as a metabolic barrier blocking cancer immunotherapy

Immune evasion remains a major obstacle to cancer immunotherapy and arises from multifaceted mechanisms. A new narrative review published in Cellular Oncology argues that one underappreciated culprit is the acidic tumor microenvironment itself, which the authors describe as a critical physicochemical barrier that orchestrates immunosuppression and undermines the effectiveness of immunotherapy.

According to the review, acidosis in the tumor microenvironment acts on both arms of the immune response. It impairs the immunosurveillance and cytotoxic functions of innate and adaptive effector cells, the very cells responsible for detecting and killing tumor cells. At the same time, it promotes the expansion and suppressive potency of regulatory T cells and myeloid-derived suppressor cells, two populations that actively dampen antitumor immunity. The acidic setting thus remodels the immune landscape in a direction that favors tumor survival, creating a form of immune evasion that arises alongside better-known mechanisms.

The authors report that preclinical studies indicate targeting tumor acidosis can partially restore antitumor immune function and may mitigate resistance to immunotherapy. However, they are explicit about the strength of this evidence: the findings support biological plausibility, but they derive primarily from in vitro systems and murine models, corroborated by in silico analyses. In other words, the case for acidity as a therapeutic target rests largely on laboratory and animal data rather than on demonstrated benefit in patients.

Clinical evidence, the review notes, remains limited to early-phase safety and target-engagement studies, and translation to patients is therefore not yet established. This distinction matters for how the work should be read. The review does not claim that acidosis-targeting treatments work in the clinic; it argues that the strategy is biologically plausible and preclinically supported, and that it warrants rigorous clinical evaluation.

One translational direction the authors highlight is pH imaging, which they describe as an emerging tool for patient selection and pharmacodynamic monitoring of pH-directed interventions. The authors conclude that targeting metabolic acidity is a strategy that should ideally be guided by non-invasive pH measurement as it moves toward clinical testing.

Subject of Research: How tumor microenvironment acidosis suppresses antitumor immunity and may be targeted to improve cancer immunotherapy

Article Title: Acidosis as a metabolic barrier to immunotherapy: mechanisms and therapeutic opportunities

Article References: Li, R., Li, H., Zhang, Y., Dong, X., Yao, X., Chen, W., An, H., & Li, Y. (2026). Acidosis as a metabolic barrier to immunotherapy: mechanisms and therapeutic opportunities. Cellular Oncology. https://doi.org/10.1007/s13402-026-01313-3

Image Credits: AI Generated

DOI: 10.1007/s13402-026-01313-3

Keywords: tumor microenvironment, acidosis, cancer immunotherapy, immune evasion, regulatory T cells, myeloid-derived suppressor cells, preclinical studies, pH imaging, immunosuppression, Cellular Oncology, metabolic, barrier