Notes: (Z)-4-hydroxy Tamoxifen is an active metabolite of the estrogen receptor (ER) modulator tamoxifen (Item No. 13258).{31466} It is primarily formed from tamoxifen by the cytochrome P450 (CYP) isoforms CYP2D6 and CYP2B6.{28446} (Z)-4-hydroxy Tamoxifen (10 nM) decreases progesterone receptor (PR) mRNA expression induced by the estrogen steroid 17β-estradiol (Item No. 10006315) in MCF-7 breast cancer cells.{67256} Liposomal administration of (Z)-4-hydroxy tamoxifen (4 mg/kg twice per week) reduces tumor growth in an RPMI-8226 multiple myeloma mouse xenograft model.{67257}