Figure 1.

Effect of IGF-I and E2 on the induction of DNA-synthesis in the MCF-7 strains. Serum-starved cells grown in 24-wells plates were given no mitogens (-), 20 ng/ml of IGF-I (I₍₂₀₎), 2 ng/ml of IGF-I (I₍₂₎), 2 ng/ml of IGF-I in combination with 1 nM E2 (I₍₂₎E2), or 1 nM E2 (E2) and were harvested after 30 h. ³H-thymidine (2 μCi/ml) was added to the culture 6 h before harvesting. Indicated values are means of triplicate measurements, and were normalized for the incorporation induced by 20 ng/ml of IGF-I (100%).