Hypoxia and HIF pathway in cancer and the placenta.

In this review we note that the placenta and cancer both develop in microenvironments in which there are gradients of oxygen availability. Whilst fundamentally different in that placental development is organised and physiological whilst cancer is chaotic and pathological, there are similarities in their respective capacities to proliferate, invade adjacent tissues, generate a blood supply and avoid rejection by the immune system. We provide a brief description of the hypoxia-inducible factor (HIF) pathway and indicate the ways by which HIF activity can be regulated to achieve oxygen homeostasis. We then exemplify the potential role of the HIF pathway in contributing to those functions shared between the placenta and cancer through effects on cellular proliferation, cell death, angiogenesis, blood vessel co-option, vascular mimicry, cell adhesion molecules, secretion of matrix metalloproteinases, antigen presentation mechanisms and immunosuppressive factors. We advocate future studies to explore these similarities and differences in the hope of improving our understanding of both systems and hence treatments of placental disorders and cancer.