FST and neoplasm: In addition, Follistatin also has effects on tumor-associated angiogenesis, which mostly depends on the inhibition of Activin A. Endothelial cells constitutively express activin receptors and VEGF, and binding of Activin A leads to inhibition of proliferation of cultured endothelial cells by downregulation of p21 and downregulation of VEGF expression19,32.