NMDA receptors belong to the ionotropic glutamate receptor family, a class of proteins best known for mediating excitatory synaptic transmission in the brain. When glutamate and a co-agonist bind, the channel pore opens and permits an influx of calcium and sodium ions into the cell. In neurons, this calcium entry triggers cascades that strengthen or weaken synapses. The review’s central premise is that an analogous logic operates in the immune system: tumor tissues are rich in glutamate and related excitatory amino acids, and myeloid cells patrolling that environment express NMDA receptors capable of translating this extracellular metabolic signal into intracellular calcium flux. The result is a signaling axis that couples the metabolic state of the tumor to the functional identity of its immune infiltrate.

The downstream consequences of this calcium signaling are strikingly specific. According to the review, NMDA receptor activity on myeloid cells promotes M2 macrophage polarization, the alternative activation state characterized by expression of markers such as CD163, CD206, and the mannose receptor Mrc1, along with production of interleukin-10 rather than the inflammatory interleukin-12. M2-polarized tumor-associated macrophages suppress cytotoxic T cell activity, remodel the extracellular matrix, and secrete growth factors that support angiogenesis and metastatic spread. In parallel, NMDA-driven signaling enhances the suppressive capacity of myeloid-derived suppressor cells, or MDSCs, a heterogeneous population that inhibits T cell responses through production of reactive oxygen and nitrogen species, arginase-1-mediated depletion of L-arginine, and indoleamine 2,3-dioxygenase-driven catabolism of tryptophan.

Technically, the calcium influx through NMDA receptors engages several well-characterized intracellular pathways. The review describes activation of the MAPK and ERK cascades, the cAMP response element-binding protein CREB, and the signal transducer and activator of transcription STAT3, each of which has established roles in driving pro-tumor myeloid differentiation. Transcription factors including PPARγ and KLF4, hallmarks of M2 programming, are also implicated. Beyond transcriptional changes, calcium-dependent signaling reshapes myeloid metabolism itself, shifting cells toward fatty acid oxidation and oxidative phosphorylation, the bioenergetic profile typical of immunosuppressive M2 macrophages, and away from the glycolytic, inflammatory program of M1 cells. The kynurenine pathway of tryptophan degradation, with enzymes such as IDO, TDO, KMO, and 3-hydroxyanthranilate 3,4-dioxygenase, emerges as a metabolic bridge connecting glutamate signaling to the generation of immunosuppressive metabolites like quinolinic acid, itself an endogenous NMDA receptor agonist.

This last point hints at a self-reinforcing loop that the authors highlight as particularly consequential for tumor biology. Tumor cells and myeloid cells release glutamate into the extracellular space, and excitatory amino acid transporters and glutamate-metabolizing enzymes such as glutamate carboxypeptidase II, which cleaves N-acetylaspartylglutamate, modulate local ligand availability. Activated myeloid cells then produce kynurenine pathway metabolites, some of which further stimulate NMDA receptors, sustaining calcium signaling and consolidating the suppressive phenotype. In this model, the tumor microenvironment becomes an ecosystem in which ion channel activity, amino acid metabolism, and immune cell differentiation feed one another, progressively locking the infiltrate into a state that tolerates rather than attacks the malignancy.

The review also situates NMDA signaling within the broader landscape of ion channel immunometabolism. Various classes of ion channels, including calcium, sodium, and potassium channels, function as sensors of metabolic cues, converting changes in the extracellular ionic and nutrient milieu into altered immune cell behavior. What distinguishes NMDA receptors is their ligand-gated nature and their exquisite sensitivity to the amino acid composition of the microenvironment, which makes them uniquely positioned to integrate tumor-derived metabolic signals. The authors frame this as an extension of immunometabolism research, arguing that ion influx is not merely a downstream consequence of immune activation but an upstream determinant of cell fate, shaping whether a myeloid cell becomes an antigen-presenting ally of antitumor immunity or a suppressive accomplice of the tumor.

Perhaps the most clinically provocative section of the review concerns immunotherapy. Immune checkpoint inhibitors targeting PD-1 and PD-L1 have transformed treatment for melanoma, lung cancer, and other malignancies, yet many patients either do not respond or eventually relapse, frequently because suppressive myeloid cells dominate the tumor microenvironment. The review compiles recent studies indicating that combining NMDA receptor antagonists, or antagonists of related ionotropic glutamate receptors such as AMPA and kainate receptors, with anti-PD-1 or anti-PD-L1 therapy enhances immunotherapy efficacy in preclinical settings. By blocking calcium-driven myeloid reprogramming, these antagonists appear to soften the immunosuppressive barrier that otherwise blunts checkpoint blockade, allowing cytotoxic CD8-positive T cells, natural killer cells, and antibody-dependent cellular cytotoxicity mechanisms to operate more effectively.

The therapeutic logic extends to other facets of myeloid biology described in the review. Suppressive myeloid cells contribute to resistance through neutrophil extracellular traps, elastase and myeloperoxidase release, expression of checkpoint molecules such as Lag-3 and TIM-3, and secretion of vascular endothelial growth factor and transforming growth factor beta. NMDA receptor signaling intersects with hypoxia-inducible factor 1 alpha-driven adaptation to the hypoxic tumor core and with Notch pathway regulation, adding further layers to the network that ion channel blockade could perturb. The authors also note connections to epithelial-to-mesenchymal transition and matrix remodeling via fibronectin, suggesting that myeloid NMDA signaling may influence not only immune evasion but also invasion and metastatic behavior.

Several caveats temper the enthusiasm. The evidence base is drawn largely from preclinical models and correlative human studies, and the precise expression patterns of NMDA receptor subunits on distinct myeloid subsets in human tumors remain incompletely mapped. Systemic NMDA receptor blockade carries well-known neurological risks, given the receptors’ essential roles in synaptic plasticity, so translating this biology into the clinic will require careful attention to pharmacology, dosing, and possibly tumor-selective delivery strategies. The review, which was funded by Warsaw University of Technology through its Excellence Initiative: Research University program and published open access, is explicit that ion channel signaling represents an attractive target whose therapeutic window must still be defined.

Even so, the synthesis marks a conceptual shift worth attention. For decades, cancer immunology has focused on ligands, cytokines, and checkpoint proteins as the currency of immune regulation. This review argues that ions, and the channels that admit them, deserve equal billing. If calcium entry through NMDA receptors genuinely determines whether macrophages and MDSCs defend the host or defend the tumor, then the glutamate-rich, metabolically warped interior of a cancer is not just background noise but an active instructional signal, one that can be intercepted. As combination strategies pairing ion channel antagonists with checkpoint inhibitors move toward validation, the humble synaptic receptor may find a second career at the front lines of oncology, turning the tumor’s own metabolic language against it.

Subject of Research: The role of NMDA ion channels in calcium-dependent myeloid cell reprogramming within the tumor microenvironment and its impact on cancer immunotherapy

Article Title: N-methyl-D-aspartate (NMDA) ion channels drive calcium-dependent myeloid cell reprogramming to shape cancer immunity and immunotherapy

Article References: Zaremba, D. D., Czarnecka, A. M., & Wińska, P. (2026). N-methyl-D-aspartate (NMDA) ion channels drive calcium-dependent myeloid cell reprogramming to shape cancer immunity and immunotherapy. Cancer Immunology, Immunotherapy. https://doi.org/10.1007/s00262-026-04483-z

Image Credits: AI Generated

DOI: 10.1007/s00262-026-04483-z

Keywords: NMDA receptors, ion channels, calcium signaling, myeloid cells, M2 macrophages, MDSCs, tumor microenvironment, immunometabolism, immune evasion, anti-PD-1/PD-L1, cancer immunotherapy, glutamate signaling