Hypoxia

Hypoxia is highly relevant to cancer biology once abnormal cells or tumors exist. Low oxygen regions inside tumors can activate HIF signaling, angiogenesis, metabolic adaptation, inflammation, invasion, and resistance to radiation or some therapies. Hypoxia is less clearly a standalone initiating cause in healthy tissue. As a Cause record, the most accurate description is indirect contribution: oxygen stress and hypoxic microenvironments may support cancer progression, survival, and treatment resistance, rather than being a conventional direct carcinogen.