Circulating endothelial cells as biomarkers of prostate cancer

Prostate cancer has a wide spectrum of biological aggressiveness, and where an individual tumor lies within this spectrum can be difficult to characterize at diagnosis. The degree of tumor vascularization in prostate cancer correlates with disease progression and, thus, markers of angiogenesis are potential indicators of clinical outcome. Identification of improved prognostic markers would have a substantial effect on patient outcomes. Such markers would also be invaluable in assessments of the effectiveness of experimental chemotherapeutic regimens and antiangiogenic drugs that are currently under investigation. Bone-marrow-derived circulating endothelial progenitors (CEPs) and circulating endothelial cells (CECs) play an integral part in neovascularization and their levels in the circulation correlate with disease progression and therapeutic response in various settings. Although CECs and CEPs are yet to be thoroughly investigated in prostate cancer, the evidence suggests that these markers may be of use in the prostate-cancer setting. We review current understanding of the contributions of CEPs and CECs to tumor progression, and discuss their potential as prognostic markers.