Contact of endothelial cells with inhibitors of inhibin and/or the alpha subunit of inhibin can be utilized to modify the activity of endothelial cell expression products including SMAD 1/5. Methods can also include inhibiting Alk1 and/or endoglin as components of inhibin-activated pathway of SMAD 1/5 signaling. Methods can be combined with other anti-angiogenesis therapies such as anti-VEGF therapies. Methods can be utilized in treatment of inhibin-expressing cancers (e.g., ovarian cancer, pancreatic cancer) as well as other pathologies such as preeclampsia and PCOS.