Elevated vascular endothelial growth factor (VEGF) serum levels in idiopathic myelofibrosis

An increase of angiogenesis has been shown in idiopatic myelofibrosis with myeloid metaplasia (MMM) by microvessel density count method but evaluation of circulating angiogenic factors is still incomplete. In 31 patients affe cted by MMM and in 12 healthy subjects we evaluated the serum levels of VEG F (vascular endothelial growth factor) and correlated VEGF with clinical an d laboratory features of disease. We found that MMM patients had circulatin g VEGF concentrations much higher than controls (median 1208 ng/ml vs 138 n g/ml, P < 0.0001). No correlation was found between VEGF and Hb, WBC, PLT, LDH, creatinine, bone marrow cellularity, fibrosis, splenomegaly, hepatomeg aly, 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 PL T 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 an d we calculated that VEGF concentration was much higher in platelet-rich th an in platelet-poor plasma and that platelets of MMM patients contained fou r times more VEGF than those of healthy controls. These results indicate th at VEGF is overproduced in MMM, thus confirming an increased angiogenic act ivity. Platelets are probably a major source of VEGF in MMM but not the onl y one.