MPL and acquired polycythemia vera: And finally, since c-Mpl is the only JAK2-dependent HGF receptor expressed in HSCs; since expression of the oncogene JAK2V617F is responsible for disease in virtually all patients with PV and half with PMF and ET [55]; and since all JAKs must bind to an HGF receptor to function, c-Mpl is again implicated in human MPNs.