Abstract: |
Among the molecular and cellular processes that orchestrate construction of new blood vessels, the distinct contribution of circulating cells has recently become appreciated. The endothelial progenitor cell (EPC) was one of the first identified circulating cell types found to directly contribute to neo-vessels walls. Subsequently, a complex network of signals between EPCs and other circulating bone marrow-derived cell types has been described. Significant temporal and spatial heterogeneity in utilization of circulating progenitor cells exists between tumor types, complicating analysis in both animal models and in patients. A lack of standardized cell surface markers and techniques for quantitation of such rare cells has further complicated such studies. Nonetheless, levels of EPCs and other bone marrow-derived progenitors may hold prognostic significance for cancer patients or may be used in the future to guide therapy and EPCs may themselves represent a valid therapeutic target. © 2008 Springer US. |