What Does Radiotherapy Do to Endothelial Cells?

It has been presumed that the severe gastrointestinal side effects accompanying radiotherapy in cancer patients result from the radiation-induced death of epithelial stem cells in the intestinal crypts. As Folkman and Camphausen explain in their Perspective, this view may change with the findings of Paris et al., who show that the principal gut cells dying in response to radiation are the endothelial cells of the gut microvasculature. Gut epithelial stem cells die because they depend on microvascular endothelial cells for survival, a situation reminiscent of the dependence of tumor cells on endothelial cell proliferation and the growth of new blood vessels.