ABCG2 and breast neoplasm: This was further confirmed by immunofluorescence, where spheroids were labelled with CD44+/CD24−/low/ABCG2/KI67 for CSCs derived from breast tumors (Fig. 2a and b), and CD133+/CD44+/ABCG2/Ki67 for prostate (Fig. 2c and d) and ovarian tumors (Fig. 2e, f, and g); except for the prostate LnCap CSCs, which were not CD44+ (Fig. 2d).