Using the transwell insert pre-coated with confluent human umbilical vein endothelial cells (HUVECs), we added breast tumor cells on top of the endothelial cells in the insert under four different conditions: (i) control siRNA in endothelial cells, (ii) ICAM1 knockdown in endothelial cells alone, (iii) in tumor cells alone, or (iv) in both tumor cells and endothelial cells (Fig. 4a). Here, ICAM1 is linked to breast neoplasm.