Similarly, stimulation of WT BMDMs with MDA CM significantly increased the number of OCs (MDA CM: 2.3-fold), and the blockade of Mstn completely inhibited the MDA-mediated stimulation of OC differentiation (Fig. 3D), indicating that human MDA BC cells are also able to influence OC differentiation via the secretion of Mstn. Here, MSTN is linked to breast cancer.