FIGURE 4.

The effects of IGFBP3 overexpression on growth promotion, IGF-1 induced receptor activation and sensitivity to an IGF-1R inhibitor. A, conditioned medium was collected from EV, miR-21KD, and IGFBP3-overexpressing SJ-G2 (or MT330) cells, added to SJ-G2 cells that were grown in low serum (0.1%) containing medium for 18 h, and cell growth rate was determined. B, serum-deprived EV-, IGFBP3-overexpressing, or miR-21KD SJ-G2 cells transduced with scrambled or shIGFBP3 were treated with recombinant human (rh) IGF-1 (50 ng/ml) for the indicated time, lysed, and immunoblotted for phospho-IGF-1R (pIGF-1R), IGF-1R, or actin. C, serum-deprived SJ-G2 cells were pretreated with varying concentrations of BMS-754807 (BMS) for 2 h and then stimulated with IGF-1 (50 ng/ml) for 1 h. Cells were lysed and immunoblotted for phospho-IGF-1R, IGF-1R, phospho-Akt (pAkt), Akt, or actin. D, EV, IGFBP3-overexpressing, and miR-21KD SJ-G2 cells were grown in the presence or absence of BMS-754807 (2.5 μm), and cell proliferation was determined at daily intervals.