AQP3 and breast cancer: In breast cancer, the highest level of expression of AQP3 was observed in endocrine-sensitive (YS1.2) breast cancer cells, followed by endocrine -resistant (pII) breast cancer cells, and the weakest expression was found in normal breast epithelial cells (MCF10A) [64], implicating that estrogen might act as an upstream regulator of AQP3.