ESR1 and breast cancer: In a high passage model of MCF-7 cells (MCF-7H), the estrogen-independent and antiestrogen insensitive growth of MCF7H cells led to high levels of Her2/neu, EGFR, and ER-α in breast cancer cells [38], which would explain the increase in ER and Her2/neu transcripts in cells in the context of estrogen depletion.