Targeting Cancer With Gene Therapy Using Hypoxia as a Stimulus

Tumors are known to have an abnormal and chaotic vascular network, unable to effectively or reliably supply the whole tumor with oxygen and nutrients. Over the past years direct evidence has accumulated showing that reduced oxygen tension (hypoxia) is a common feature of both experimental and human solid tumors (1 ). For example, in a study of human breast cancer, the median tumor oxygen partial pressure (pO₂ ) for all stages of the disease was found to be around 28 mm Hg (3.9% O₂ ), compared with 65 mm Hg (8.7% O₂ ) for normal breast tissue. In the normal breast, pO₂ values less than 2.5 mm Hg (approx 0.3% O₂ ) could not be detected, whereas they were measured in about one-third of the breast cancer cases (2 ). Severe hypoxia has also been reported for head and neck cancer, cervical cancer, and melanomas (3 –5 ).