The central premise of the framework rests on a striking discovery reported earlier this year by Kim and colleagues, who demonstrated that an epigenetic switch in vascular phenotype can dramatically augment anti-tumor immunity. Epigenetic switching refers to reversible changes in gene expression patterns that do not alter the underlying DNA sequence but instead reconfigure which genes are accessible to transcriptional machinery. In endothelial cells, such switching can transform a vessel that is immunologically hostile, one that actively excludes T cells through tight junctions, suppressive signaling molecules and abnormal architecture, into one that actively welcomes them. The letter argues that these switches are not gradual, quantitative changes but rather bistable states, akin to a toggle, meaning that tumor vessels may exist in one of two functionally distinct programs with very different consequences for immunotherapy response.

This binary view of vascular state is supported by a 2022 study published in Cancer Cell, in which Hua and colleagues showed that cancer immunotherapies can transition endothelial cells into high endothelial venules, specialized vessels normally found in lymph nodes that serve as gateways for lymphocyte recirculation. Remarkably, these induced high endothelial venules within tumors generate niches for TCF1-positive T lymphocytes, a stem-like population of T cells that sustains long-term anti-tumor responses, through a feed-forward loop in which the vessels and the immune cells reinforce each other’s beneficial states. The existence of such a self-amplifying circuit suggests that if a tumor’s vasculature can be nudged past a critical threshold, the resulting immune-vessel partnership may become self-sustaining, whereas tumors that never cross this threshold remain refractory to checkpoint blockade regardless of how potent the T cell response is elsewhere in the body.

The vascular-readiness compass is conceived as a way to formalize this threshold concept into a practical orientation tool. According to the authors, the compass would integrate molecular, histological and functional readouts of tumor endothelial state, including markers of high endothelial venule differentiation, expression of adhesion molecules such as those involved in lymphocyte rolling and diapedesis, epigenetic signatures characteristic of permissive versus restrictive vascular programs, and cytokine profiles that either license or suppress T cell extravasation. Rather than treating the tumor vasculature as a passive backdrop, the compass would place vascular state at the center of treatment planning, guiding clinicians toward combinations that first render vessels permissive before deploying T cell-directed therapies such as immune checkpoint inhibitors.

One of the most compelling lines of evidence cited in support of this approach comes from work on cytokine priming. In a 2023 Nature Communications study, Kim, Anandh, Null and colleagues demonstrated that priming a vascular-selective cytokine response permits CD8-positive T cell entry into tumors. The key insight is that cytokines such as those in the interferon family can act directly on endothelial cells, inducing a transcriptional program that makes vessels sticky and permeable to cytotoxic lymphocytes, but this effect is selective and time-dependent. Indiscriminate cytokine administration has historically been limited by systemic toxicity, so the challenge is to direct these signals specifically to the tumor vasculature. The letter argues that a vascular-readiness assessment could identify which patients would benefit from such priming and at what point in the treatment sequence it should occur.

The therapeutic implications extend to gene therapy as well. Ramachandran and colleagues showed in 2023, again in Cancer Cell, that tailoring vascular phenotype through adeno-associated virus, or AAV, therapy promotes anti-tumor immunity in glioma, one of the most immunologically cold and treatment-resistant malignancies in human medicine. By using viral vectors to deliver payloads that remodel endothelial behavior, the researchers were able to convert the immunosuppressive vasculature of brain tumors into a state compatible with immune cell infiltration. That this strategy succeeded in the hostile environment of the central nervous system, where the blood-brain barrier presents an additional obstacle to immune trafficking, underscores the generality of the vascular-reprogramming principle and the potential value of a compass-like framework for deciding when such interventions are warranted.

The commentary also draws on a 2024 review by Cleveland and Fan in Trends in Molecular Medicine, which catalogued the growing arsenal of endothelial reprogramming strategies for cancer immunotherapy. Together with the primary research literature, these sources paint a picture of a field in transition. For roughly two decades, the dominant paradigm in tumor vascular biology was anti-angiogenesis, the idea that starving tumors of their blood supply would restrain growth. That paradigm produced clinical successes but also revealed an unexpected complication: vessels deprived of adequate oxygen tend to reinforce immunosuppression, and in some settings, pruning the vasculature made immune exclusion worse. The new paradigm, sometimes described as vascular normalization or vascular immunomodulation, instead seeks to make tumor vessels behave more like healthy tissue, restoring their capacity to support immune surveillance while maintaining oxygen and nutrient delivery.

What distinguishes the vascular-readiness compass from earlier normalization concepts, the authors contend, is its emphasis on epigenetic memory and switching dynamics. Endothelial cells exposed to inflammatory or angiogenic stimuli can retain chromatin-level marks that persist long after the original stimulus is gone, meaning that a vessel’s history shapes its current responsiveness. This epigenetic memory has practical consequences for treatment sequencing. A tumor whose vessels have been pre-conditioned by radiation, cytokine exposure, or prior immunotherapy may carry chromatin configurations that make a subsequent switch to a permissive state far easier to achieve. Conversely, vessels locked into a deeply angiogenic, VEGF-driven program may resist reprogramming unless the epigenetic barriers are first addressed, potentially with agents that modify chromatin accessibility. The compass framework explicitly incorporates this temporal dimension, treating vascular readiness as something that can be measured, tracked and deliberately engineered over the course of treatment.

The translational promise of this framework is considerable, but the authors are careful to frame it as a research agenda rather than a ready-made clinical test. Defining the precise molecular markers that constitute a “ready” versus “unready” vascular state will require systematic profiling of tumor vasculature across cancer types and treatment contexts. Single-cell transcriptomics and spatial profiling technologies now make it feasible to map endothelial heterogeneity within tumors at unprecedented resolution, and these tools could supply the empirical foundation for the compass. Longitudinal studies tracking vascular state before, during and after immunotherapy would be needed to validate whether vascular readiness truly predicts response, and whether interventions that shift vascular state in humans translate the dramatic effects seen in mouse models. Questions of biopsy accessibility, particularly in tumors of the brain, pancreas and other difficult-to-sample sites, will also need to be addressed, potentially through circulating biomarkers or non-invasive imaging surrogates of vascular phenotype.

The authors of the letter, who received no specific funding for the work and declare no conflicts of interest, hope that their compass metaphor will catalyze a shift in how oncologists and immunotherapy developers think about the tumor microenvironment. If the ongoing wave of clinical trials begins to incorporate vascular-readiness assessments, either through endothelial markers in biopsy specimens, imaging signatures of vessel maturation, or blood-based indicators of endothelial activation, the framework could move from concept to bedside. In an era when only a minority of patients respond durably to checkpoint inhibitors, the identification of a modifiable, measurable gatekeeper controlling immune entry into tumors represents one of the more actionable ideas in contemporary cancer research. The blood vessels of a tumor, long viewed as merely its supply lines, may in fact hold the key to deciding whether the immune system’s most powerful weapons are ever allowed through the gate.

In a stark contrast to physiological angiogenesis, which follows a meticulously orchestrated program involving sprouting and maturation of blood vessels, tumor angiogenesis is profoundly chaotic and disorganized. The review elucidates that the endothelial cells populating the tumor vasculature emanate not only from pre-existing adjacent blood vessels but also from an array of unexpected progenitor sources. Bone marrow-derived endothelial progenitor cells (EPCs) can home to tumor sites and differentiate into functional vascular endothelium, contributing to aberrant vessel formation. Moreover, the startling plasticity of cancer stem cells, capable of transdifferentiating into endothelial-like cells, adds another layer of complexity to the tumor vascular milieu.

Beyond the classical endothelial lineage, the review highlights emerging evidence of transdifferentiation events involving non-endothelial cellular players within the tumor microenvironment. Cancer-associated fibroblasts (CAFs), widely recognized for their roles in matrix remodeling and signaling, exhibit potential to assume endothelial characteristics under hypoxic conditions. Similarly, immature dendritic cells, traditionally considered immune sentinels, may transdifferentiate into endothelial-like cells, further amplifying vascular heterogeneity. These revelations underscore a fundamental deviation in tumor vasculature genesis, emphasizing the plasticity and adaptability of cellular constituents under pathological stimuli.

One of the most formidable barriers to successful vascular-targeted therapies lies in the intrinsic heterogeneity and adaptability of tumor blood vessels. Unlike structurally and functionally stable vessels in normal tissue, tumor blood vessels are irregular, leaky, and structurally aberrant. The review carefully dissects the molecular underpinnings that orchestrate this disarray, particularly how dysregulated signaling pathways influence endothelial cell behavior. The vascular endothelial growth factor (VEGF) family remains a centerpiece in angiogenic signaling; however, the interplay with platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), and the angiopoietin-Tie2 axis creates a signaling network that is both redundant and capable of compensatory activation when targeted therapeutically.

Therapeutic attempts to inhibit tumor angiogenesis, primarily through anti-VEGF agents, have been met with variable and frequently transient success. The review discusses the mechanisms militant tumors employ to circumvent angiogenic blockade. Adaptive angiogenesis enables tumors to activate alternative pro-angiogenic pathways, effectively sidestepping VEGF inhibition. Genetic heterogeneity among tumor endothelial cells fosters a subset of resistant phenotypes that survive therapeutic pressure, sustaining neovascularization. This evolving resistance not only diminishes the efficacy of current anti-angiogenic drugs but also encourages more aggressive tumor behavior, necessitating a paradigm shift in vascular-targeted cancer therapies.

In light of these challenges, the review argues for the urgent development of more nuanced, multi-targeted therapeutic strategies. It advocates focusing on the diverse cellular origins of tumor endothelium and the molecular redundancy of angiogenic signaling pathways. Targeting the bone marrow-derived EPCs alongside local endothelial cells, modulating cancer stem cell plasticity, and intercepting transdifferentiation events stand as promising frontiers. Such approaches could effectively disrupt the vascular support system of tumors, impairing their growth and metastatic potential.

The molecular complexity of signaling in tumor angiogenesis, including VEGF, PDGF, FGF, and angiopoietin/Tie2 systems, serves not only to promote vessel growth but also to regulate vessel stability, permeability, and interaction with perivascular cells. The review elaborates on how alterations in these pathways influence tumor vascular phenotypes and how their differential expression across tumor types and stages complicates treatment. This intricate signaling milieu requires tailored interventions that can simultaneously address multiple signaling nodes to prevent compensatory mechanisms.

Importantly, the article delves into the hypoxic microenvironment typical of solid tumors, which acts as a pivotal driver in vessel formation and endothelial cell origin specification. Hypoxia-inducible factors (HIFs) activate transcriptional programs that not only upregulate VEGF but also modulate the recruitment and differentiation of diverse endothelial progenitors and supporting stromal cells. This hypoxia-induced plasticity and cell lineage flexibility present both challenges and targets for disrupting tumor vascularization.

Moreover, the review accentuates the ecological interplay between tumor cells, stromal constituents, and immune components in shaping the tumor vasculature. This bidirectional communication influences endothelial cell phenotype and function, contributing to the anomalous architecture of tumor arteries and capillaries. It sheds light on how immune cell-derived cytokines and growth factors can potentiate angiogenesis or, under certain contexts, inhibit it, outlining the complexity of immune-vascular crosstalk in cancer.

By integrating recent discoveries in endothelial cell biology and tumor physiology, the article sets a foundation for the future of anti-angiogenic therapy that is both precise and dynamic. Moving beyond the conventional monotherapies, it suggests combination regimens that concurrently target multiple cell populations and signaling pathways, potentially overcoming the formidable challenge of therapeutic resistance and tumor adaptability.

Ultimately, this comprehensive review in Genes & Diseases offers an unprecedented lens through which to view tumor angiogenesis—not simply as aberrant vessel growth but as a multifactorial, highly plastic process involving a mosaic of cellular contributors and intricate signaling networks. It brings hope that unraveling these complexities will catalyze the design of next-generation therapies capable of more effectively starving tumors and mitigating metastatic spread.

As the field advances, the translation of these insights into clinical strategies will depend on continued interdisciplinary research combining molecular biology, oncology, pharmacology, and immunology. Understanding the origins and mechanisms of tumor endothelial cells is no longer a question of curiosity—it is a vital frontier in the war against cancer.

Subject of Research: Tumor angiogenesis and endothelial cell origins
Article Title: Endothelial cell in tumor angiogenesis: Origins, mechanisms, and therapeutic implication
News Publication Date: November 1, 2025
Image Credits: Genes & Diseases
Keywords: Cancer genetics, tumor angiogenesis, endothelial cells, vascular endothelial growth factor, cancer stem cells, bone marrow-derived endothelial progenitor cells, anti-angiogenic therapy, drug resistance, hypoxia, molecular signaling pathways