Angiogenic growth factors: autocrine and paracrine regulation of survival in hematologic malignancies.

Recent research has focused on the role of angiogenic growth factors and their ability to mediate tumor growth and metastases, both in solid tumors and in hematologic malignancies. The bone marrow microenvironment is the setting for a wealth of complex interactions that include cell-to-cell contacts as well as secretion of and response to soluble factors. Abundant evidence supports the role of basic fibroblast growth factor (bFGF) in contributing to the dysregulation of apoptosis that is the hallmark of chronic lymphocytic leukemia (CLL). In fact, CLL cells themselves express bFGF; intracellular levels of this cytokine correlate with clinical CLL stage. Other stromal factors mediate the inhibition of apoptosis in CLL as well, suggesting that strategies to block the responses of CLL cells to these factors may represent effective therapies. More broadly, the class of agents known as angiogenesis inhibitors may offer important advantages with respect to the treatment of numerous types of malignancies. Currently, a number of clinical trials are under way to evaluate the clinical potential of several different angiogenesis inhibitors in several hematologic neoplasms.