Gao et al. (2012) showed that lung stromal cells restrict the growth of metastasis by secreting high levels of active BMP. Interestingly, the ability of breast cancer cells to overcome this anti metastatic mechanism was related to secretion of COCO (DAND5) and consequent inhibition of BMP signaling. Ren et al. (2019), in the same study mentioned before, described that TGF-β-induced CAFs activation results in GREM1 (BMP inhibitor) secretion in vitro. This evidence concerns the gene GREM1 and breast cancer.