The proliferation inhibition and apoptosis in M12 cells promoted by IGFBP-3 in the presence of low-dose IFN-γ is dependent on the PI-3K/mTOR pathway. A–B: M12 cells were treated with DMSO, 50 nM rapamycin in the absence or the presence of 20 U/ml IFN-γ and/or 5 μg/ml rhIGFBP-1, 5 μg/ml flag-tagged rhIGFBP-3 or 5 μg/ml flag-tagged rhIGFBP-3(GGG) as indicated. The cell lysates were collected 5h (B) or 36h (A) post-treatment and analyzed as described in Fig. 3A. C: M12 cells on 96-well plates were pretreated for one hour with 0.1% (v/v) DMSO, 5 μM LY294002, or 50 nM rapamycin and then treated with either HBSS, 20 U/ml IFN-γ, or 1 μg/ml rhIGFBP-3(GGG) as indicated. Apoptosis in M12 cells at 96 hour post-treatment was measured and the results are expressed relative to control (treated with HBSS/DMSO), which was assigned a value of 1. The data presented here are the mean±SE from three independent experiments performed in triplicates.