Fig 3.

Effects of clinically relevant concentrations of tamoxifen and its metabolites on the estrogen-stimulated proliferation of MCF-7 cells. Estrogen-stimulated growth of MCF-7 cells is inhibited minimally by clinically relevant concentrations of tamoxifen and its metabolites (without endoxifen), but growth is blocked completely in the presence of increasing concentrations of endoxifen (1,000 nmol/L). Note that 20 nmol/L endoxifen is observed in poor metabolizers while 100 nmol/L is observed in extensive metabolizers. E2, estradiol; TAM, tamoxifen; 4HT, 4-hydroxytamoxifen; NDT, N-desmethyltamoxifen. Data adapted and modified.⁵