ESR1 and breast cancer: The expression of four representative genes (androgen receptor (AR), Forkhead Box A1 (FOXA1), MYB Proto-Oncogene, Transcription Factor (MYB), Trefoil Factor 1 (TFF1) identified from differential expression analysis with known expression in ER+ BC, was validated in HR+ vs TNBC tumors using qRT-PCR (Fig. 2C).