Angiogenesis, angiogenic factor expression and hematological malignancies.

Solid tumor growth consists of an avascular and a subsequent vascular phase. Several studies have now shown that, as in solid tumors, angiogenesis also plays a critical role in the progression of hematological malignancies. Monoclonal gammopathy of undetermined significance (MGUS) and non-active to active multiple myeloma (MM) progress when plasma cells induce angiogenesis and this in turn promotes progression. The increased bone marrow neovascularization, increased angiogenic and proteolytic potential of plasma cells may explain the frequent occurrence of extramedullary localization in MM. As observed in active MM, enhanced bone marrow neovascularization is apparent in acute untreated lymphoblastic leukemia. In B-cell non-Hodgkin's lymphomas, angiogenesis is significantly enhanced in relation to progression. Angiostatic molecules, such as thalidomide, could also be considered for the clinical management of hematological tumors.