However, butein inhibition of AKT phosphorylation was uniquely detected in various breast cancer cells including butein-sensitive HCC-1569 (basal A, HER2+), BT-474 (luminal, ER+/PR+/HER2+), and HCC-70 (basal A, TNBC) cells, while it was not found in butein-resistant and luminal HER2+ SKBR-3, HCC-1419 and HCC-2218 cells (Figure 4A and B). Here, ESR1 is linked to breast cancer.