To identify the receptor operating upstream of Gs in endothelial cells, we performed an siRNA-mediated knock-down of 23 Gs-coupled receptors or orphan receptors which are highly expressed in HUVECs and primary mouse lung endothelial cells (MLECs; Fig. S2 d), and determined endothelial cell proliferation in the absence or presence of MeWo melanoma cells (Fig. 3 a and Fig. S2 e). The gene discussed is APC; the disease is melanoma.