Targeting the vascular endothelial growth factor in hematologic malignancies

There exists increasing evidence that apart from solid tumors, angiogenic growth factors also play important roles in the development and/or maintenance of hematolymphoid malignancies. Thus, in these cancers, angiogenesis and bone marrow microvessel density often correlate with prognosis and disease burden. Several reports speculated on the role of angiogenesis and the resulting possible therapeutic options in hematologic malignancies. The most prominent angiogenic factor, vascular endothelial growth factor (VEGF), is expressed in a number of established leukemic cell lines as well as in freshly isolated human leukemias and lymphomas, and several human leukemias express VEGF receptor 1 and/or VEGF receptor 2. VEGF/VEGF-receptor interactions are also involved in proliferation, migration, and survival of leukemic cells by autocrine and paracrine mechanisms. As a consequence, a possible drugable effect by inhibiting VEGF signaling in different hematologic malignancies has been discussed. This review focuses on angiogenesis-independent effects of VEGF on survival and proliferation of leukemic or lymphoma cells and on possible therapeutic approaches using anti-VEGF/VEGF-receptor therapies to inhibit proliferation or induce apoptosis of malignant cells in hematologic diseases.