Figure 6

Eltrombopag stimulates megakaryopoiesis in CD34+ cells isolated from patients with relapsed multiple myeloma. CD34+ cells isolated from patients with relapsed multiple myeloma (n = 5, A and B) or CD34+ cells from normal controls (n = 4, C and D) were evaluated in CFU-Mk progenitor assays performed in semi-solid MegaCult media in the presence or absence of 0–10 μM eltrombopag or 50 ng/ml rhTPO. CFU-Mk colonies were enumerated after incubation for 11 days. Total CFU-Mk numbers are presented in (A) and (C), and differential colony numbers by their size are presented in (B) and (D). Data are presented as the mean Mk colony number relative to that with 50 ng/ml TPO (mean ± S.E., n = 5 individual patients or n = 4 normal controls with experiments each performed in triplicate). ^* p < 0.02 for all doses tested. ns = not significant. (E) CD34+ cells from normal controls (n = 4 for eltrombopag and n = 2 for rhTPO) were cultured in a serum-free StemSpan liquid medium containing rhSCF (50 ng/ml), rhIL-3 (10 ng/ml), and rhIL-6 (10 ng/ml) in the presence of 10 μM eltrombopag or 100 ng/ml rhTPO for 11 days, and the surface expression of CD41a and CD42b was analyzed by flow cytometry. Each dot plot represents individual donor.