Fig. 1
Constant phosphorylation of RARαS77 in human TNBC cells associates with RA-resistance. a Representative picture of RARα (p-Ser77) expression in human TNBC tissues and the neighboring non-tumorous tissues by immunohistochemical (IHC) staining. Scale bar, 50 μm. b Representative staining intensity of breast tumor tissue microarrays classified as four different grades. IHC score is the sum of staining intensity and positive cell rate. Scale bar, 50 μm. TNBC strong signal vs. non-TNBC strong signal, *** p < 0.001. c Western blotting analysis of RARαS77 phosphorylation levels in non-TNBC cell lines (MCF-7, T47D, and SKBR3) and TNBC cell lines (MDA-MB-231, MDA-MB-453 and MDA-MB-436) with or without RARα agonist AM580 for 48 h. d MDA-MB-231 and MDA-MB-436 cells were treated with pan-RARs agonist ATRA, RARα/β agonist AM80, and RARα agonist AM580 for indicated concentrations and time. Cell viability was assessed by MTT analysis and IC50 values were calculated. After treatment of different RARs agonists for indicated concentrations and time, RARα (p-Ser77) and total RARα expression levels were detected by western blotting in (e) MDA-MB-231 and (f) MDA-MB-436 cells