Inhibition of CDK6 using Palbociclib in combination with Ruxolitinib markedly improves myelofibrosis in murine models

Myelofibrosis (MF) is a deadly blood neoplasia that presents the worst prognosis among myeloproliferative neoplasms (MPN). Expression of CDK6 is significantly elevated in MPN/MF hematopoietic progenitor cells. In this study, we investigated the efficacy of CDK4/6 inhibitor Palbociclib alone or in combination with Ruxolitinib in Jak2V617F and MPLW515L murine models of MF. Treatment of Palbociclib alone significantly reduced leukocytosis, splenomegaly and inhibited bone marrow fibrosis in Jak2V617F and MPLW515L mouse models of MF. Combined treatment of Palbociclib and Ruxolitinib resulted in normalization of peripheral blood leukocyte counts, marked reduction of spleen size and abrogation of bone marrow fibrosis in murine models of MF. Mechanistically, we show that Palbociclib treatment or depletion of CDK6 inhibits Aurora kinase, NF-?B and TGF-ß signaling pathways in Jak2V617F mutant hematopoietic cells. Overall, our data suggest that Palbociclib in combination with Ruxolitinib may have therapeutic potential for treatment of MF. Overall design: Examining of effect of palbociclib and ruxolitinib in mice with homozygous JAK2V617F mutation