Michael Boulis

Background: Tumor growth beyond ~1 mm³ induces severe hypoxia, stabilizing HIF‑1α and driving VEGF/PDGF-mediated neovascularization.¹ Under normal oxygen, HIF-1α is hydroxylated by prolyl hydroxylases and degraded, but in hypoxia or pseudohypoxia (e.g., von Hippel–Lindau loss) it stabilizes and drives VEGF transcription.^2-3 Recent studies highlight distinct pro-angiogenic circuits: high circulating angiogenic factors (VEGF, FGF) from hypoxic cells can “steer” vessels and affect tumor perfusion, while chronic pseudohypoxia drives immunosuppression via adenosine and glycolytic metabolism in T cells.^1,4 Identifying hypoxia-related biomarkers (HSP70, iNOS, IL-6, VEGF, etc.) enables tumor stratification and prognosis.⁵

Objective: We review mechanisms of true hypoxia versus pseudohypoxia in tumor angiogenesis, delineate emerging diagnostic markers, and examine therapeutic vulnerabilities, notably vessel “steering” and immune evasion, exploitable to starve tumors.

Methods: A search of PubMed was conducted for peer-reviewed articles published between 2018 and 2025. The following MeSH terms were searched: tumor, HIF‑1, hypoxia, pseudohypoxia, angiogenesis, angiogenic markers, vessel steering, and immune evasion. Peer-reviewed preclinical and clinical studies were selected based on mechanistic insights and translational relevance.

Results: Hypoxic stress (O₂ <10 mmHg¹) upregulates endothelial angiogenic factors and creates gradients guiding anastomoses⁶. Computational models confirm that hypoxia‑driven VEGF gradients largely determine vessel network shape: even with 50% reduced EC proliferation, vessel density can remain unchanged if VEGF gradients persist.⁶ This suggests that exogenous VEGF “decoys” might reroute vasculature away from tumors. Clinically, a panel of hypoxia-inducible markers (iNOS, HSP70, IL-6, VEGF) in glioma patients strongly correlates with tumor grade and survival, underscoring hypoxia’s diagnostic value.⁵ In contrast, pseudohypoxic signaling in hematologic malignancies drives immune escape: CLL-induced pseudohypoxia forces T cells into aerobic glycolysis and adenosine release, impairing cytotoxicity, a state reversible by venetoclax/obinutuzumab that restores T‑cell oxidative phosphorylation.⁴ Similarly, enforced HIF‑1α activation (pseudohypoxia) in hematopoietic progenitors induces dysplastic/MDS phenotypes.⁷ Notably, the interplay of oxygen levels and cell movement implies caution: in a microfluidic co-culture, normoxic (5% O₂) conditions promoted endothelial sprouting toward tumor cells, whereas hypoxic (1% O₂) suppressed angiogenesis, causing cancer cells to migrate toward vessels.⁸ Thus, abruptly relieving hypoxia might inadvertently enhance tumor invasion.⁸

Conclusion: Hypoxia-driven angiogenesis represents both a vulnerability and an adaptive mechanism for tumors. Hypoxic biomarkers consistently mark aggressive disease⁵, and advanced models reveal how oxygen tension governs vessel directionality⁸. Therapeutically, hijacking these signals, for example by elevating VEGF decoys or targeted reoxygenation, could steer new vessel growth away from tumor masses, effectively starving cancer of blood supply. Simultaneously, antagonizing pseudohypoxia (e.g. restoring HIF degradation or blocking adenosine) may reverse local immune suppression. Together, these strategies offer a novel angle to constrain tumor growth by rerouting its lifelines toward healthy tissue.

Works Cited:

1. Li Y, Zhao L, Li XF. Hypoxia and the Tumor Microenvironment. Technology in Cancer Research & Treatment. 2021;20(20):153303382110363. Published 2021 Aug 5. doi: https://doi.org/10.1177/15330338211036304
2. Zhang J, Yao M, Xia S, Zeng F, Liu Q. Systematic and comprehensive insights into HIF-1 stabilization under normoxic conditions: implications for cellular adaptation and therapeutic strategies in cancer. Cellular & Molecular Biology Letters. 2025;30(1). Published 2025 Jan 6. doi:https://doi.org/10.1186/s11658-024-00682-7
3. Chappell JC, Payne LB, Rathmell WK. Hypoxia, angiogenesis, and metabolism in the hereditary kidney cancers. Journal of Clinical Investigation. 2019;129(2):442-451. Published 2019 Jan 7. doi:https://doi.org/10.1172/jci120855
4. Chiara Montironi, Chaja Feige Jacobs, Gaspard Cretenet, et al. T-cell dysfunction by pseudohypoxia and autocrine purinergic signaling in chronic lymphocytic leukemia. Blood advances. 2023;7(21):6540-6552. doi:https://doi.org/10.1182/bloodadvances.2023010305
5. Shrivastava R, Gandhi P, Sorte SK, Shrivastava A. Characterizing the Linkage of Systemic Hypoxia and Angiogenesis in High-Grade Glioma to Define the Changes in Tumor Microenvironment for Predicting Prognosis. Journal of Molecular Neuroscience. 2024;74(3). doi:https://doi.org/10.1007/s12031-024-02240-4  ‌
6. Moreira-Soares M, Coimbra R, Rebelo L, Carvalho J, D. M. Travasso R. Angiogenic Factors produced by Hypoxic Cells are a leading driver of Anastomoses in Sprouting Angiogenesis–a computational study. Scientific Reports. 2018;8(1):8726. doi:https://doi.org/10.1038/s41598-018-27034-8  ‌
7. Hayashi Y, Zhang Y, Yokota A, et al. Pathobiological Pseudohypoxia as a Putative Mechanism Underlying Myelodysplastic Syndromes. Cancer Discovery. 2018;8(11):1438-1457. Published 2018 Nov 1. doi:https://doi.org/10.1158/2159-8290.cd-17-1203
8. Aratake S, Funamoto K. Physiological hypoxia promotes cancer cell migration and attenuates angiogenesis in co-culture using a microfluidic device. Microfluidics and Nanofluidics. 2024;28(10). doi:https://doi.org/10.1007/s10404-024-02768-2