The Persistent Survival of MPN Cells to JAK2 Inhibition is Dependent on SHP2 Activity, Which May Provide a Therapeutic Target to Enhance Current Anti-MPN Therapies

Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis, are hematopoietic stem cell disorders that affect about 300,000 people in the U.S. PV and ET can progress to myelofibrosis where patients are susceptible to bone marrow failure, increased incidence of acute leukemia, and poor survival. MPNs are driven by aberrant JAK2 activity that is a consequence of mutations in JAK2, Mpl, or CalR. The JAK1/2 inhibitor ruxolitinib, which is FDA-approved for a subset of MPN patients, is effective in reducing patient symptomology but fails to induce remission, as it has little effect on the neoplastic cell burden. However, a modest increase in survival and decrease of allele burden has been suggested following long-term ruxolitinib treatment. The quality of life benefit afforded by ruxolitinib suggests it will likely remain a mainstay of future MPN therapies. Identifying the mechanism(s) by which cells persistently survive in the presence of ruxolitinib could prove pivotal to improving JAK2 inhibitor therapies in MPN patients.