ERBB2 and breast cancer: To investigate if EGFR is related to AQP3 in breast cancer, we used three different types of breast cancer cell lines, the estrogen receptor (ER)- and progesterone receptor (PR)-positive cell line, MCF7, the HER2-positive cell line, SkBr3, and the ER-, PR-, and HER2-negative (triple negative) cell line, SUM159PT.