Table 1.
Estrogen-dependent proliferation of breast cancer cell lines is dependent on IGF-IR
| Cell line | Compound | E2 IC50 (nmol/l) | Δ4A IC20a (nmol/l) | Δ4A IC50 (nmol/l) | Δ4A IC80a (nmol/l) |
| MCF7 3(1) | AEW541 | 150 ± 8 | NA | NA | NA |
| MCF7/Aro | AEW541 | 91 ± 37 | 66 ± 15 | 130 ± 16 | 280 ± 36 |
| Letrozole | NA | 150 ± 8 | 444 ± 89 | 1,160 ± 372 | |
| T47D | AEW541 | 544 ± 133 | NA | NA | NA |
| T47D/Aro | AEW541 | 612 ± 124 | 733 ± 422 | 4,474 ± 2,613 | 31,272 ± 2,300 |
| Letrozole | NA | 9 ± 7 | 67 ± 29 | 2171 ± 502 | |
Steroid-deprived MCF7, MCF7/Aro, T47D, and T47D/Aro cells were treated with either 17β-estradiol (E2) or androstenedione (Δ4A) in the presence of increasing concentrations of letrozole or AEW541 for 6 days. Percentage inhibition of proliferation was determined as described in the text. The average inhibitory concentrations at 20%, 50%, and 80% (IC20, IC50, and IC80, respectively) ± standard deviation was calculated for MCF7 cell lines. aIC25 and IC75 values were calculated for T47D cell lines. IGF-IR, insulin-like growth factor I receptor; NA, not applicable.