The cover shows the endothelin-1 (ET-1) immunostaining of tumor co-opted arterioles (bottom panel) and size-matched healthy arterioles (top panel). Using a pressure myograph, the authors report that the observed increased endothelin-1 expression in tumor arterioles leads to the devel-opment of a myogenic tone. This represents an important reserve for vasorelaxation that can be therapeutically exploited: the administration of an ETA receptor antagonist to tumor-bearing mice selectively promotes tumor perfusion and oxygenation and consecutively increases the effec-tiveness of tumor radiotherapy. For details, see the article by Sonveaux et al. on page 3209 of this issue.