A Novel Bystander Effect in Tamoxifen Treatment: PPIB Derived From ER+ Cells Attenuates ER− Cells via Endoplasmic Reticulum Stress-Induced Apoptosis

Markable reductions were observed in tumorigenesis of estrogen receptor (ER)− breast cancer cells by applying both supernatants from Tamoxifen -treated ER+ cells and a transwell co-culture system, validating the presence of a TAM-induced bystander effect.