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Table 1 Estrogen-dependent proliferation of breast cancer cell lines is dependent on IGF-IR

From: The aromatase inhibitor letrozole and inhibitors of insulin-like growth factor I receptor synergistically induce apoptosis in in vitro models of estrogen-dependent breast cancer

Cell line

Compound

E2 IC50 (nmol/l)

Δ4A IC20 a (nmol/l)

Δ4A IC50 (nmol/l)

Δ4A IC80 a (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

  1. 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.