SOAT1 and myeloproliferative neoplasm: ,40 Activation of the JAK-STAT pathway is especially common in the myeloproliferative neoplasms (MPNs), >90% of which contain driver mutations that activate JAK-STAT signaling.41, 42, 43, 44, 45, 46 JAK inhibitors are used to treat patients with MPN with advanced disease,47 but although these can lead to symptomatic improvement, they rarely reduce the allele burden,48, 49, 50 suggesting that they fail to eradicate malignant HSCs.