BMI1 and cancer: These findings are reminiscent of the association between antitumor effect by inhibition of Bmi‐1 self‐renewal protein and reduction in the Bmi1+ CSCs fraction (Kreso et al, 2014), and identify the CXCR4+ CCF in cancer tissue as a possible marker for monitoring metastasis response to T22‐GFP‐H6‐FdU therapy.