What distinguishes VISTA from checkpoint molecules such as PD-1 and CTLA-4 is where it acts and how it is deployed. In many human malignancies, VISTA is preferentially enriched not on tumor cells themselves but on the innate immune cells that populate the tumor microenvironment, including tumor-associated macrophages, myeloid-derived suppressor cells and dendritic cells. This compartment-specific distribution matters because these myeloid populations orchestrate much of the immune suppression that characterizes so-called cold tumors. When VISTA is abundant on these cells, the result is suppressive myeloid differentiation, impaired antigen presentation, altered inflammatory cytokine programs and, ultimately, T-cell dysfunction and immune exclusion, the physical and functional exclusion of cytotoxic T lymphocytes from the tumor bed.

The structural biology of VISTA helps explain its unusual behavior. Like PD-L1, it belongs to the B7 family of immunoregulatory molecules, but it possesses distinctive features, including an acidic pH-selective binding mode. Landmark work published in Nature in 2019 demonstrated that VISTA functions as an acidic pH-selective ligand for PSGL-1, meaning its suppressive signaling is most active in the hypoxic, lactate-rich, acidic conditions that prevail inside solid tumors. This pH dependence effectively arms VISTA precisely where tumors are most aggressive and where other therapies struggle, and it may underlie the molecule’s contribution to resistance against PD-1 and CTLA-4 blockade in selected settings.

The receptor web surrounding VISTA extends well beyond PSGL-1. Subsequent studies have identified additional binding partners, including VSIG-3, which inhibits human T-cell function upon engagement, galectin-9, which cooperates with VISTA to suppress cytotoxic T lymphocyte activity, and LRIG1, which engages VISTA on dendritic cells and impairs tumor-specific CD8-positive T-cell responses. A recent study also revealed that a four-amino-acid intracellular motif of VISTA can block growth receptor signaling within cancer cells themselves, indicating that the molecule can exert tumor-intrinsic effects in addition to its immunoregulatory ones. Which of these ligand interactions dominates in living tumors remains an open question and one of the key unresolved issues highlighted by the review authors.

Evidence from preclinical models has been particularly revealing about the myeloid dimension. Research published in Cancer Immunol Res showed that VISTA controls antitumor immunity by regulating myeloid cell-mediated inflammation and immunosuppression, while a 2024 study in Cell Reports demonstrated that VISTA promotes the metabolism and differentiation of myeloid-derived suppressor cells through STAT3- and polyamine-dependent mechanisms. Hypoxia itself induces VISTA expression on myeloid-derived suppressor cells, amplifying their suppressive function. Work on tumor-associated macrophages has shown that VISTA drives these cells toward a pro-tumoral phenotype that promotes cancer cell phagocytosis while down-regulating T-cell responses, and that targeting a conserved population of TIM3-positive, VISTA-positive macrophages can overcome resistance to cancer immunotherapy.

The clinical relevance of this biology is increasingly documented across tumor types. In prostate cancer, VISTA expression was found to increase after ipilimumab therapy, positioning it as a mechanism of adaptive resistance. Comparative analyses of melanoma and pancreatic cancer identified VISTA as a potential target in the notoriously immunotherapy-resistant pancreatic setting, and elevated VISTA has been reported in gastric and colorectal carcinomas, oral squamous cell carcinoma, cervical carcinoma and non-small cell lung cancer. In metastatic melanoma, VISTA upregulation has been linked to acquired resistance to anti-PD-1 therapy. Intriguingly, the prognostic picture is not uniform: in triple-negative breast cancer, VISTA expression on immune cells correlated with favorable outcome, underscoring the review’s central argument that cellular source and spatial localization determine the biological and prognostic meaning of VISTA measurements.

Therapeutic strategies targeting VISTA have advanced into early clinical testing. The oral small-molecule inhibitor CA-170, derived from a PD-1 sequence, exhibited preclinical antitumor efficacy, although debate persists about its precise molecular targets. More refined approaches include KVA12123, a highly potent anti-VISTA antibody described as promising against poorly immunogenic tumors and currently in phase 1/2 testing alone and in combination with pembrolizumab in patients with advanced solid tumors, and HMBD-002, an IgG4 monoclonal antibody evaluated in a first-in-human phase 1 trial. A pH-selective antibody termed SNS-101 has been engineered to activate preferentially in the acidic tumor microenvironment, enhancing PD-1 pathway responses while limiting systemic exposure. Rationally designed antibodies that blockade the C-C’ loop region of VISTA have been shown to reverse immune suppression and remodel the immune microenvironment in an Fc-independent manner.

Combination approaches reflect the conviction that VISTA operates in parallel to, rather than downstream of, classical checkpoints. Bifunctional small molecules simultaneously targeting PD-L1 and VISTA have shown favorable pharmacokinetics in preclinical development, dual silencing of tumor-intrinsic VISTA and CTLA-4 has stimulated T-cell mediated responses in breast cancer models, and VISTA blockade has been shown to enhance the efficacy of radiotherapy in murine melanoma and adenocarcinoma models. Nanoparticle-based delivery systems targeting VISTA have induced potent antitumor immunity in preclinical studies, and chemotherapy itself has been shown to induce VISTA expression in tumor cells via HIF-2alpha, suggesting that sequencing VISTA-directed therapy with cytotoxic treatment could be clinically important.

Technological advances are reshaping how researchers interrogate VISTA biology. Spatial transcriptomics, multiplexed imaging platforms such as CODEX and imaging mass cytometry now allow investigators to map VISTA expression at single-cell resolution within intact tissue architecture, addressing precisely the questions of cellular source and spatial localization that the review identifies as central. Such compartment-resolved analysis may improve prognostic interpretation, biomarker development and patient selection for VISTA-directed therapies, moving the field beyond simple expression quantification toward a functional understanding of where, when and in whom the pathway matters.

The reviewers conclude that VISTA should be regarded as a dynamically regulated, myeloid-centered checkpoint axis rather than a redundant inhibitory receptor, with translational relevance concentrated in checkpoint-refractory and immune-excluded tumors. Whether early pharmacodynamic evidence of target engagement will convert into durable clinical benefit remains the decisive unanswered question, but as combination trials mature and spatial profiling sharpens patient stratification, VISTA is emerging as one of the most compelling next-generation targets in cancer immunotherapy, potentially unlocking treatment for the many patients whom PD-1 and CTLA-4 blockade have so far failed.

Subject of Research: VISTA immune checkpoint biology in myeloid cells and its therapeutic targeting in cancer

Article Title: VISTA as a myeloid-centered checkpoint axis in cancer: biology, tumor microenvironment, and therapeutic implications

Article References: Tekiner, S., Karataş, R. B., Alras, Y., Zıkşahna, K., Merdan, S., & Ihlamur, M. (2026). VISTA as a myeloid-centered checkpoint axis in cancer: biology, tumor microenvironment, and therapeutic implications. Medical Oncology, 43(10), Article 280. https://doi.org/10.1007/s12032-026-03416-1

Image Credits: AI Generated

DOI: 10.1007/s12032-026-03416-1

Keywords: VISTA, VSIR, immune checkpoint, myeloid cells, tumor microenvironment, tumor-associated macrophages, myeloid-derived suppressor cells, cancer immunotherapy, checkpoint resistance, PSGL-1, acidic pH, antibody therapy