ESR1 and breast cancer: In this study, through cellular and molecular analyses (including transcriptome analysis and bioinformatics analysis, etc.)on MCF7 and MCF7-TamC3 breast cancer cells, we further found that MCF7-TamC3 cells exhibit characteristics that resemble the “luminal B-ERBB2 positive” (i.e., ER+, ERBB2+, and ERBB2-targeting agent-sensitive) breast tumor subtype.