Biological characteristics of Rh123(high) stem-like cells in a side population of 786-O renal carcinoma cells

The aim of the present study was to investigate the differences in biological characteristics between the rhodamine 123 (Rh123)(high) and Rh123(low) subpopulations of the renal cancer cell line 786-O and to identify evidence for the existence of cancer stem cells in renal cell carcinoma (RCC) cells. In vitro cultured RCC 786-O cells were stained with Rh123, analyzed and sorted with flow cytometry. The differences in proliferative activity, long-term differentiation and radiation sensitivity between the two subpopulations were measured and the oncogenicity of each subpopulation was evaluated according to their neoplastic growth ability in soft agar and tumor-forming ability in NOD/SCID immunodeficient mice. There were two subpopulations in the cultured 786-O cells, Rh123(high) and Rh123(low) cells. Rh123(low) cells were the majority among 786-O renal carcinoma cells and barely formed solid tumors in NOD/SCID mice and colonies in soft agar. By contrast, the Rh123(high) cells were the minority, exhibited high proliferative activity, differentiation ability and resistance to radiation and showed high tumorigenesis potential and colony forming efficiency. The Rh123(high) cells had stem-like characteristics in cultured RCC 786-O cells in vitro.