Targeting hypoxia tolerance in cancer.

Regulation of tissue oxygen homeostasis is critical for cell function, proliferation and survival. Evidence for this continues to accumulate along with our understanding of the complex oxygen-sensing pathways present within cells. Several pathophysiological disorders are associated with a loss in oxygen homeostasis, including heart disease, stroke, and cancer. The microenvironment of tumors in particular is very oxygen heterogeneous, which may explain much of our difficulty in treating cancer effectively. This is true when comparing levels of hypoxia among different patient tumors, but also within individual tumors. Accumulating evidence implicates the biological responses to hypoxia and the alterations in these pathways in cancer as important contributors to overall malignancy and treatment efficacy. This has recently prompted several investigations into the possibility of targeting treatment at the biological responses to hypoxia.