Using three different breast cancer cell lines: estrogen-receptor (ER)-positive, Luminal A MCF-7 cells, triple-negative basal-like HCC1806 cells, and triple-negative claudin-low MDA-MB-231 cells, to represent a variety of breast cancer subtypes, we showed that treatment with BenSer reduced glutamine uptake to ~ 65% of control across all three cell lines (Fig. 1a), while leucine uptake was inhibited more strongly to ~ 45% (MCF-7 and MDA-MB-231) and 22% (HCC1806) of control (Fig. 1b). Here, ESR1 is linked to breast cancer.