ESR1 and breast cancer: Using immunofluorescence staining, we detected intracellular expression of two oestrogen receptors (ER-α and ER-β) and PR, and membrane expression of HER-2 in MFUM-BrTNBC-1 and the commercial BC CLs MCF-7, MDA-MB-453 and MDA-MB-231 (Figure 3).