FIGURE 2.

SHP-2 mediates PRL enhancement of IGF-IR phosphorylation. A–C, serum-starved MCF-7 cells were pretreated with dimethyl sulfoxide (DMSO) and either 200 μm vanadate (A), 10 μm PTP-1B inhibitor (B, inh.), or 50 μm NSC-87877 (C) for 1 h prior to treatment with vehicle, IGF-I, PRL, or IGF-I/PRL for 15 min. D, MCF-7 cells were transfected with nontargeting (NT) or SHP-2-specific siRNA duplexes and treated with vehicle, IGF-I, PRL, or IGF-I/PRL for 15 min. Cell lysates were immunoblotted with the indicated antibodies. Top panels, representative experiment; bottom panels, quantification of p-IGF-IR signal/total IGF-IR in response to IGF-I alone, compared with IGF-I + PRL, as described under “Experimental Procedures” (means ± S.D., n = 3 (A–C) or n = 4 (D)). The asterisks denote significant differences compared with IGF-I treatment. *, p < 0.05; **, p < 0.01 (two-way ANOVA, Bonferroni post-test (A, C, and D) or paired t test (B)).