The cell cycle regulator CDC25Ais a target for JAK2 V617F oncogene

The JAK2V617F mutation is present in the majority of patients with polycythemia vera and one-half of those with essential thrombocythemiaandprimarymyelofibrosis. JAK2V617F is a gain-of-function mutation resulting in constitutive JAK2 signaling involved in the pathogenesis of these diseases. JAK2V617F has been shown to promote S-phase entry. Here, we demonstrate that the CDC25A phosphatase, a key regulator of the G1/S cell-cycle transition, is constitutively overexpressed in JAK2V617F-positive cell lines, JAK2mutated patient CD36 progenitors, and in vitro‐differentiated proerythroblasts. Accordingly, CDC25A is overexpressed in BM and spleen of Jak2V617F knock-in mice compared with wild-type littermates. By using murine FDC-P1‐EPOR and human HEL and SET-2 cell lines, we found that JAK2V617F-induced CDC25Aupregulation was caused neither by increased CDC25Atranscription or stability nor by the involvement of its upstream regulators Akt and MAPK. Instead, our results suggest that CDC25A is regulated at the translational level through STAT5 and the translational initiation factor eIF2. CDC25A inhibition reduces the clonogenic and proliferative potential of JAK2V617F-expressing cell lines and erythroid progenitors while moderately affecting normal erythroid differentiation. These results suggest that CDC25A deregulation may be involved in hematopoietic cells expansion in JAK2V617F patients, making this protein an attracting potential therapeutic target. (Blood. 2012; 119(5):1190-1199)