CD133+ renal progenitor cells contribute to tumor angiogenesis

In the present study, we tested die hypothesis that resident progenitor cells may contribute to tumor vascularization and growth. CD133(+) cells were isolated from 30 human renal carcinomas and characterized as renal resident progenitor cells on the basis of the expression of renal embryonic and mesenchymal stem cell markers. CD133(+) progenitors differentiated into endothelial and epithelial cells as the normal CD133(+) counterpart present in renal tissue. In the presence of tumor-derived growth factors, these cells were committed to differentiate into endothelial cells able to form vessels in vivo in SCID mice. Undifferentiated CD133(+) progenitors were unable to form tumors when transplanted alone in SCID mice. When co-transplanted with renal carcinoma cells' CD133(+) progenitors significantly enhanced tumor development and growth. This effect was not attributable to the tumorigenic nature of CD133(+) progenitor cells because the same results were obtained with CD133(+) cells from normal kidney. CD133(+) progenitors contributed to tumor vascularization as the majority of neoformed vessels present within the transplanted tumors were of human origin and derived from the co-transplanted CD133(+) progenitors. In conclusion, these results indicate the presence of a renal progenitor cell population in renal carcinomas that may differentiate in endothelial cells and favor vascularization and tumor growth.