PROM1 and nonpapillary renal cell carcinoma: To further study the effect of TNF, we isolated CD133+cells from ccRCC‐(ccRCCCD133+CSCs).21 Isolated cells were strongly positive for CD133 and exhibited a stem‐cell phenotype evidenced by strong immunostaining for SSEA‐4 and Nanog (Figure 1E,F), as previously reported.21 To test whether TNF phosphorylates STAT3 in ccRCC‐CD133+CSCs, cells were treated with wtTNF, R1TNF, and R2TNF or left UT for 30 minutes (37°C).