Antiangiogenic therapy in hematologic malignancies

Angiogenesis is defined as the formation of new capillaries from prexisting blood vessels and plays an important role in the progression of solid tumors and hematologic malignancies. Markers of angiogenesis correlate with clinical characteristics in leukemia and non-Hodgkin's-lymphoma, serving as predictors of poor prognosis. Antiangiogenic effects of chemotherapeutics as well as of novel drugs such as farnesyltransferase inhibitors and tyrosine kinase inhibitors such as Gleevec(R) might contribute to their therapeutic potential. Thalidomide which has antiangiogenic effects and direct cytotoxic effects was found to be effective in multiple myeloma and is considered as an established treatment modality for patients with refractory or relapsed multiple myeloma. Thalidomide has a significant therapeutic effect in myelodysplastic syndrome (MDS) by improving cytopenia and achieving independence of transfusion therapy in a subset of patients. Preliminary data indicate activity of specific VEGF receptor tyrosine kinase (RTK) inhibitors in multiple myeloma (MM) and acute myeloid leukemia (AML). The positive correlation between increased levels of angiogenic cytokines and clinical response to VEGF-RTK inhibitors and thalidomide indicates the relevance of detecting angiogenesis markers to identify best candidate patients for specific approaches. Including antiangiogenic drugs into treatment protocols for hematologic malignancies is an important task for future clinical studies.