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Updated: Jul 10, 2025
Tumor Hypoxia Assessment: In Vivo 3D Oxygen Imaging Through Electron Paramagnetic Resonance
Published on: February 14, 2025
Longitudinal dynamics of the tumor hypoxia response: From enzyme activity to biological phenotype
Sandy Che-Eun S Lee1,2, Andrea Hye An Pyo1,2, Marianne Koritzinsky1,2,3,4
1Princess Margaret Cancer Center, University Health Network, Toronto, Ontario, Canada.
Abstract:
Poor oxygenation (hypoxia) is a common spatially heterogeneous feature of human tumors. Biological responses to tumor hypoxia are orchestrated by the decreased activity of oxygen-dependent enzymes. The affinity of these enzymes for oxygen positions them along a continuum of oxygen sensing that defines their roles in launching reactive and adaptive cellular responses. These responses encompass regulation of all steps in the central dogma, with rapid perturbation of the metabolome and proteome followed by more persistent reprogramming of the transcriptome and epigenome. Core hypoxia response genes and pathways are commonly regulated at multiple inflection points, fine-tuning the dependencies on oxygen concentration and hypoxia duration. Ultimately, shifts in the activity of oxygen-sensing enzymes directly or indirectly endow cells with intrinsic hypoxia tolerance and drive processes that are associated with aggressive phenotypes in cancer including angiogenesis, migration, invasion, immune evasion, epithelial mesenchymal transition, and stemness.
Insights
Tumor hypoxia, or poor oxygenation, triggers cellular responses via oxygen-sensing enzymes. These adaptations enhance cancer cell survival and promote aggressive traits like migration and immune evasion.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Biology
Background:
- Human tumors frequently exhibit heterogeneous regions of poor oxygenation (hypoxia).
- Biological responses to tumor hypoxia are mediated by oxygen-dependent enzymes.
- The oxygen affinity of these enzymes dictates their role in cellular sensing and response.
Purpose of the Study:
- To elucidate the mechanisms by which tumor hypoxia influences cellular responses.
- To understand how oxygen-sensing enzymes orchestrate adaptive and reactive cellular processes.
- To connect hypoxia-driven cellular changes to aggressive cancer phenotypes.
Main Methods:
- Analysis of oxygen-dependent enzyme activity in hypoxic tumor environments.
- Investigation of cellular and molecular responses to varying oxygen levels.
- Examination of gene and epigenome reprogramming under hypoxic conditions.
- Correlation of hypoxia response pathways with cancer aggressiveness markers.
Main Results:
- Hypoxia triggers rapid changes in cellular metabolome and proteome.
- Persistent reprogramming of transcriptome and epigenome occurs under hypoxia.
- Hypoxia response genes are regulated at multiple levels, adapting to oxygen concentration and duration.
- Hypoxia confers intrinsic tolerance and drives cancer progression hallmarks.
Conclusions:
- Oxygen-sensing enzymes are central regulators of cellular adaptation to tumor hypoxia.
- Hypoxia-induced cellular reprogramming contributes to cancer aggressiveness.
- Understanding these pathways offers potential therapeutic targets for hypoxic tumors.
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