Pharmacologic or genetic inhibition of CDC25A inhibits clonogenic capacities of CD34⁺ cells from JAK2^V617F-positive patients. (A) CD34⁺ cells from BM of HD, JAK2^V617F-positive PV, or ET patients, and a patient with secondary polycythemia (JAK2^WT), were purified and plated at a concentration of 1.5-3.10³ cells/mL in duplicate, in the presence or the absence of the CDC25 inhibitor IRC-083864 and in the presence (left) or the absence (right) of EPO. The erythroid colonies (BFU-E) were scored at day 14. Results are expressed as percentage of control (untreated). (B) CD34⁺ cells from HD, or from JAK2^V617F-positive PV or PMF patients, were purified, cultured overnight, and transfected with control or CDC25A siRNA. Top, siRNA efficiency was evaluated by Western blot 24 hours after transfection. Western blots are representative of results obtained on control and JAK2^V617F samples. Bottom, cells (1.5-3.10³) were plated in duplicate, in the presence (left) or the absence of EPO (right). The erythroid colonies (BFU-E) were scored at day 14. Results are expressed as percentage of control (control siRNA). (C) The growth of cells in erythroid differentiation medium was followed by cell counting after trypan blue staining.