EDN1 and cancer: Figure 4 shows a tumouroid consisting of all three cell types, with cancer cells stained for CK7, endothelial cells stained for CD31, and fibroblasts stained for vimentin. By day 14, the cancer cells induced by ET-1 invaded the stroma both in the area adjacent to the central cancer mass and further into the stroma. Interestingly most of the cancer cells grew mainly at the outer edges of the central cancer compartment (Figure 4).