The mechanism of action of ONC201 is currently unknown, and although some data demonstrate that ONC201 causes cytotoxic effects and the mechanism of its action based on TRAIL-mediated apoptotic cell death [2,3,5,6,30,41], there are contrasting data demonstrating that ONC201 is rather cytostatic than cytotoxic and does not induce cell death in some cancer models, particularly in breast cancer cell lines [4,8,33]. Here, TNFSF10 is linked to breast cancer.