Fig. 4.

G1T48 inhibits ER signaling in models of endocrine therapy resistance in vitro a SKBR3 breast cancer cells were transfected with an estrogen-responsive reporter gene together with ER (wtER, ER-Y537S, or ER- D538G) expression plasmids prior to 18 h of treatment with 17β-estradiol (1.0 nM) and ER antagonists (10^–11–10^–5 M). Firefly and renilla luciferase activity were then assessed using dual luciferase reagent. Error bars indicate the SD of triplicate samples. b G1T48 inhibits cell growth mediated by endocrine refractory ER mutants. MCF7 cells expressing ER variants ER-D538G and ER-Y537S were treated for 7 days with doxycycline plus increasing dose of antiestrogens (10^–12–10^–5 M). Cellular proliferation was assessed by measuring DNA content (Hoechst stain) and is presented as relative fluorescence units. Error bars indicate the SD of triplicate samples. c G1T48 inhibits growth factor-mediated breast cancer cell growth. MCF7 cells were treated for 7 days with insulin (20 nM) plus increasing dose of anti-estrogens (10^–12–10^–7 M). Cellular proliferation was assessed by measuring DNA content (Hoechst stain) and is presented as relative fluorescence units. Error bars indicate the SD of triplicate samples