BMP4 induces a stellate phenotype and reduces the growth of the MDA-MB-231 cells in 3D cell culture. Cells were grown in Matrigel (A-C) or in PEG gel (D-F) supplemented with 100 ng/ml BMP4 or vehicle. Images were taken as indicated in Figure 2 and representative examples from days 7, 10 and 14 for Matrigel and days 7, 11 and 14 for PEG gel are shown. Scale bars 200 μm. (B, E) Cell proliferation and (C, F) area covered by cell clusters were measured and are presented as in Figure 2, *P < 0.05, **P < 0.01.