Effect of 17β estradiol on the tamoxifen-related growth suppression of S6B45 MM cells. ER-–positive S6B45 MM cells were cultured for 48 hours in media alone (▪) or 0.5 (▨), 5.0 (▧), and 50 (░) μmol/L of TAM with or without E2 (5.0 and 50 μmol/L).³H-TdR uptake was compared for cells cultured with TAM and E2 versus those cultured in TAM alone.