TGFB1 and breast cancer: It has been shown in one study that tamoxifen- or fulvestrant-induced TGF-β production by BC cells (primarily MCF-7) resulted in the inhibition of immune effector cytotoxic mechanisms specific to CD8+ T lymphocytes (the production of granzyme B, perforin, and FasL), which was associated with an increase in the tumor-promoting immunosuppressive regulatory T cells (Treg) pool [93].