For a 15-day treatment, these two inhibitors had strong activity against proliferation of MDA-MB231, BT549 (both showing ER−) and MCF-7 (ER+) breast cancer cells expressing relatively high levels of DOT1L (Table 1) [21], with EC50 values of 0.19 – 1.4 μM (Fig. 1b). Here, DOT1L is linked to breast cancer.