Estrogen receptor of breast cancer stem cells depending on the original breast cancers

There has been arguments about the estrogen receptor-α (from this point referred to as ER) of breast cancer stem cells (BrCSCs). Most investigations support the proposition that BrCSCs are ER(-), whereas some other studies indicate that BrCSCs are ER(+). We concluded that the ER expression of BrCSCs in ER(+) breast cancers is positive, while it is negative in ER(-) breast cancers. Therefore, we hypothesize that the ER expression of BrCSCs depends on the original breast cancers. It may provide a novel strategy for the therapy targeting BrCSCs.