Fig. 3.

MK1 is a PDGFR antagonist. (A) Correlation (R² = 0.82) between EC₅₀ for megakaryopoiesis and IC₅₀ for PDGFR inhibition. (B) Absolute number of CD41⁺ cells derived from 1,000 mPB CD34⁺ cells cultured for 10 d in the presence of vehicle (PBS), neutralizing antibodies against PDGF-AA, PDGF-BB, and PDGF-CC (all at 200 μg/mL) or a combination of all three antibodies (each at 200 μg/mL). All combinations have P < 0.01 when related to vehicle. (C) DNA content of mPB CD34⁺ cells cultured for 10 d in the presence or absence of MK1 (0.75 μM) or neutralizing antibodies against PDGF-CC (200 μg/mL). Total CD41⁺ cells and CD41⁺ cells containing 2N, 4N, and >4N are gated. (D) CFU-Mk (red) generated from mPB CD34⁺ cells cultured in the presence or absence of MK1 (0.75 μM) or neutralizing antibodies against PDGF-CC (200 μg/mL) for 8 d. (E) Total CFU-Mk present in 5,000 mPB CD34⁺ cells expanded for 8 d in the presence or absence of MK1 (0.5 μM) or neutralizing antibodies against PDGF-CC (200 μg/mL). Mean and SD are plotted from three individual plates within the same experiment. Data are representative of at least three independent experiments.