Intriguingly, MCF-7/HER2-18 xenograft tumors were more sensitive than BT-474 tumors to the capacity of anti-FASN therapy to restore the tumor’s sensitivity to tamoxifen, an observation with potential clinical importance, as this might suggest that certain subgroups of ER-positive patients who are resistant to endocrine therapy could greatly benefit from adding a FASN blocker to combined treatments with tamoxifen and HER2-targeted therapy. This evidence concerns the gene ESR1 and neoplasm.