CTR2 Identifies a Population of Cancer Cells with Stem-Like Features in Patients with Clear Cell Renal Cell Carcinoma

PURPOSE: In clear cell renal cell carcinoma tissue samples we identified and characterized a population of renal cell carcinoma derived CD133+/CD24+ cancer cells. We studied differences between these cells and their nonneoplastic counterpart, tubular adult renal progenitor cells. MATERIALS AND METHODS: CD133+/CD24+ renal cell carcinoma derived cells were isolated from 40 patients. The mesenchymal phenotype and stemness proteomic profile of these renal cell carcinoma derived cells were characterized. Colony forming efficiency and self-renewal ability were tested by limiting dilution. Tumorigenic properties were evaluated in vitro by soft agar assay. The angiogenic response was evaluated in vivo by the chorioallantoic membrane angiogenic assay. Microarray analysis was performed on 6 tubular adult renal progenitor cell and 6 renal cell carcinoma derived cell clones. Membrane protein expression was evaluated by flow cytometry and immunofluorescence staining. RESULTS: CD133+/CD24+ cells were isolated from normal and tumor kidney tissue. Fluorescence activated cell sorting revealed that renal cell carcinoma derived cells did not express mesenchymal stem cell markers. CD133+/CD24+ tumor cells were more undifferentiated than tubular adult renal progenitor cells. Renal cell carcinoma derived cells were clonigenic and could differentiate into adipocytes, epithelial and osteogenic cells. They could also regenerate tumor cells in vitro and induce angiogenesis in vivo. Gene expression profile identified CTR2 as a membrane marker for this neoplastic population. CTR2 was involved in renal cell carcinoma derived cell cisplatin resistance. CONCLUSIONS: Our results indicate the presence of a CD133+/CD24+/CTR2+ cancer cell population in clear cell renal cell carcinoma. These cells have some stem cell-like features, including in vitro self-maintenance and differentiating capabilities, and they can induce an angiogenic response in vivo