ESR1 and breast cancer: Intriguingly, higher ERBB3 expression levels correlate with lower relapse-free survival in basal-like/triple-negative (HER2-/ER-/PR-) breast cancer patients, and NRG1/ERBB3/ERBB2 axis was shown to promote anchorage-independent cell growth in basal-like/triple-negative breast cancer cells (10).