PROM1 and clear cell renal carcinoma: In the first study, the authors used cells from two sources: PROM1+ tubular adult renal progenitor cells (tARPC) purified from the healthy parts of kidney cortexes from patients undergoing nephrectomy for renal clear-cell carcinoma, and immortalized human primary renal cells (RPTEC/TERT1) cells that were obtained from a commercial vendor.