The role of endothelial progenitor cells in tumour vasculogenesis.

Abstract

OBJECTIVE: To review the biological behaviour of endothelial progenitor cells and their role and significance in tumour vasculogenesis. DATA SOURCES: The data in this review were mainly from Medline and PubMed for the relevant articles in English published from March, 1997, to March, 2008. The search terms were 'endothelial progenitor cells' (EPCs) and 'neoplasm'. Articles about the biological behaviour of EPCs and their roles in tumour vasculogenesis were included. RESULTS: EPCs, whose characteristics are similar to those of endothelial cells (ECs) and stem cells, contribute to tumour vasculogenesis during tumour progression. The mobilisation, recruitment, homing and incorporation of EPCs into tumours are multi-step and multi-factor events during tumour vasculogenesis. This complex process requires the participation of many growth factors and cells, such as tumour cells, ECs, stromal cells and EPCs in the tumour microenvironment. However, there is still some debate about EPC distribution, contribution, origin and differentiation in tumour vasculogenesis. CONCLUSIONS: The characterisation of tumour-associated EPCs may provide valuable clues for more specific anti-angiogenesis therapy and/or tumour diagnosis. Many challenges remain in understanding definition, differentiation, mobilisation and recruitment of EPCs.