Being oxygen deprived.
Cellular hypoxia is a common stress in normal development and numerous pathological conditions, including cancer. By the time a tumor has grown to a detectable size, poor and disordered angiogenesis, leaky vessels, and high interstitial tumor pressure all result in significant tumor hypoxia. Studies in human tumor xenografts reveal a mean pO2 of <5 mmHg 70–80 μm from a vessel wall. Both noninvasive measurements and direct assessment of tumor oxygenation in patients have demonstrated the presence of profound hypoxia in a marked variety of solid tumors, including melanoma, prostate cancer, head and neck cancer, and cervical cancer, as well as in hematological malignancies including myeloma. In one study, using oxygen electrodes to assess breast cancer oxygenation in 36 patients and controls, the average pO2was 30 mmHg in tumors as compared to 65 mmHg in normal breast tissue and 67 mmHg in benign fibrocystic...