ERBB2 and breast cancer: We also enriched BCSCs from MCF7 (ER+PR+HER2−) and SK-BR-3 (ER−PR+HER2+) breast cancer cell lines by sphere formation assay for one generation and observed that VLDLR-I in SK-BR-3 and VLDLR-I and VLDLR-II in MCF7 were increased in sphere-forming cells compared to monolayer cells (2D) (Figure 1D).