Hypoxic adaptation theory of cancer.

For more than 70 years, the somatic mutation theory (SMT) has dominated cancer biology, conceptualizing carcinogenesis as the cumulative consequence of genetic mutations, However, expanding molecular and microenvironmental evidence reveals important limitations in this mutation-centric framework. The Hypoxic Adaptation Theory (HAT) reframes carcinogenesis not as a purely mutation-driven process, but as the maladaptive culmination of chronic cellular hypoxia. HAT integrates with SMT by situating mutagenesis within a microenvironmental and evolutionary context rather than opposing it, positioning sustained oxygen deprivation as a primary upstream driver of genomic instability and malignant transformation. Carcinogenic exposures-whether physical, chemical, or biological-not only induce direct DNA damage but also converge on a shared pathogenic pathway characterized by cellular injury, chronic inflammation, microvascular disruption, and impaired oxygen delivery. Persistent hypoxia stabilizes hypoxia-inducible factor (HIF), initiating metabolic reprogramming toward glycolysis, pathological angiogenesis, and enhancing cellular plasticity. These adaptive responses may drive phenotypic transitions from hyperplasia to metaplasia, dysplasia, and ultimately neoplasia. Concurrently, chronic hypoxia imposes significant epigenetic pressure, remodeling chromatin accessibility, suppressing DNA repair pathways, and reprogramming transcriptional networks that support survival under low-oxygen conditions. Although initially protective, prolonged HIF activation progressively destabilizes genomic integrity, fosters mutational retention, and reinforces oncogenic behavior. Importantly, HAT situates cancer within a broader continuum of hypoxia-driven chronic diseases, encompassing cardiovascular, metabolic, neurodegenerative, and inflammatory disorders. By shifting emphasis from random mutation to chronic hypoxic stress, HAT offers a unifying model of disease pathogenesis and identifies oxygen homeostasis as both a central biological vulnerability and a promising therapeutic target.