Rosano, Sofyali, Dhiman, and colleagues show that epigenetic-related changes occur in endocrine therapy (ET)-induced dormancy in estrogen receptor positive (ER+) breast cancer, as well as in its reawakening. Targeting these epigenetic changes blocks the entrance to dormancy and reduces the persister cancer cell population, enhancing the cytotoxic effects of ET in vitro. See related article by Rosano et al., p. 866 (9).