ERBB2 and breast cancer: Within the breast cancer cell lines, which are epithelial cells derived from metastatic sites, MDA-MB-231 cells (basal ER− PR− HER2−), MCF7 (luminal ER+ PR+ HER2−), and T47D (luminal ER+ PR+ HER2−) exhibited a lower expression of mHsp70 compared to EpCAM, whereas SK-BR-3 cells (luminal ER− PR− HER2+) expressed a high expression intensity of both markers, mHsp70 and EpCAM (mHsp70: 95 ± 4%, EpCAM: 96 ± 7%).