Kinetics of vascular channel formation by breast cancer cells. MDA-MB-231, MDA-MB-435, MCF-7, and ZR-75-1 cells were serum starved overnight, plated on matrigel, and images using phase contrast microscopy were taken at the times indicated. The MDA-MB-231 and MDA-MB-435 cells started to form vascular channels as early as 2 hours after plating on matrigel. Well defined patterned networks were observed by 7 hours. MCF-7 and ZR-75-1 cells failed to form patterned networks.