The JAK2V617F Point Mutation Increases the Osteoclast Forming Ability of Monocytes in Patients with Chronic Myeloproliferative Neoplasms and Makes their Osteoclasts more Susceptible to JAK2 Inhibition

JAK2V617F is a gain of function point mutation that occurs in Myeloproliferative Neoplasm (MPN) patients and deranges their hemopoiesis at cellular level. We speculate that hyperfunctioning JAK2 can modify osteoclast (OCL) homeostasis in MPN patients. We studied 18 newly diagnosed MPN patients and four age-matched normal donors (ND). Osteoclast forming assays started from selected monocytes also and under titrated concentrations of the JAK2 Inhibitor AG-490 (Tyrphostin). Genomic DNA was extracted from the formed osteoclasts, and the JAK2V617F/JAK2WT genomic DNA ratio was calculated. OCLs formed from monocytes derived from heterozygous (Het) for the JAK2V617F mutation MPN patients, were three times more compared to those from JAK2 wild type (WT) MPN patients (p=0,05) and from ND as well (p=0,03). The ratio of JAK2V617F/JAK2WT genomic DNA was increased in OCLs compared to the input monocyte cells showing a survival advantage of the mutated clone. In comparison to ND and JAK2 WT MPN patients, OCLs from patients JAK2V617F (Het) were more susceptible to JAK2 inhibition. These alterations in osteoclast homeostasis, attributed to mutated JAK2, can deregulate the hemopoietic stem cell niche in MPN patients.