Both TAM and −E2 triggered a period of putative dormancy after one month of treatment, as shown by live and floating cell counts obtained from intermediate sampling (Fig. 2A; Supplementary Fig. S10A) confirming that endocrine therapies (ET) have a dual cytotoxic and cytostatic impact on ER+ breast cancer cells (2, 26). Here, ESR1 is linked to breast carcinoma.