Many reports have highlighted the ability of BMP4 to suppress cell proliferation, whereas facilitating cell migration and relapse,31, 32, 33 and also have demonstrated the implication of BMPs in promoting cell migration and invasion in breast cancer patients.34 It was recently shown that BMP4 could also inhibit breast cancer metastasis, in particular by affecting surrounding immune cells.35 The effects of BMPs are thus complex to decipher, as they are context-dependent and vary according to organ or cell types, culture conditions, BMPs doses used and receptor availability. This evidence concerns the gene BMP4 and breast cancer.