However, although we observed that DOC was more effective than DOX when it was administered to ERα+/PR+/HER2− tumor cells (MCF7 and ZR751) with intermediate CIN, it was not effective when administered to ERα+/PR+/HER2+ cells (BT474), where DOC induced an increase in cell proliferation compared to the control. The gene discussed is ESR1; the disease is neoplasm.