NFKB1 and breast cancer: Given that E1 upregulates NFκB and E2 downregulates NFκB in ER+/HER2- BC cells [38], and that a reciprocal regulatory axis may exist between PEDF/NFκB, we suspect E1-driven p-NFκB-p65 upregulation/activation is responsible, at least in part, for the PEDF downregulation and associated enhanced metastatic potential observed in ER+/HER2- BC cells under post-menopausal oestrogen conditions.