Regarding MPNs, our group showed that levels of HGF, IL-11 and tissue inhibitor of metalloprotease 1 (TIMP-1) were high in the serum and bone marrow plasma of PV patients, and that HGF and IL-11 regulated each other’s production using paracrine and autocrinefeed-back loops involving BMSCs and glycophorin A+ (GPA+) erythroblasts (Figure 3B) [15]. The gene discussed is GYPA; the disease is acquired polycythemia vera.