For initial characterization of RCC-CSCs candidates preselected cell surface were used and cells were isolated including CD105+ cells13 and CD133+ cells15 from nephrectomy specimens (primary tumor); CD44+ (ALDH1+) cells - from 293T human embryonic kidney cell line10,11; CXCR4+ cells from RCC-26, RCC-53 cell lines17. Here, CD44 is linked to renal cell carcinoma.