Elevated vascular endothelial growth factor (VEGF) serum levels in idiopathic myelofibrosis.
An increase of angiogenesis has been shown in idiopathic myelofibrosis with myeloid metaplasia (MMM) by microvessel density count method but evaluation of circulating angiogenic factors is still incomplete. In 31 patients affected by MMM and in 12 healthy subjects we evaluated the serum levels of VEGF (vascular endothelial growth factor) and correlated VEGF with clinical and laboratory features of disease. We found that MMM patients had circulating VEGF concentrations much higher than controls (Median 1208 ng/ml vs 138 ng/ml, P < 0.0001). No correlation was found between VEGF and Hb, WBC, PLT, LDH, creatinine, bone marrow cellularity, fibrosis, splenomegaly, hepatomegaly, and therapy. However, in the subgroup of patients with a normal or low VEGF concentration, a direct correlation between VEGF and platelet count (r = 0.90, P = 0.002) was detected. Moreover, patients with a platelet count < 300 x 10(9)/l had VEGF serum levels lower than patients with a higher PLT count (median VEGF 864 vs 1557 pg/ml, P = 0.001). In six patients and in eight controls we also had the opportunity to measure VEGF in the plasma and we calculated that VEGF concentration was much higher in platelet-rich than in platelet-poor plasma and that platetets of MMM patients contained four times more VEGF than those of healthy controls. These results indicate that VEGF is overproduced in MMM, thus confirming an increased angiogenic activity. Platelets are probably a major source of VEGF in MMM but not the only one.