Although we could not completely rule out that the phenomenon of EMT or MET might have also occurred between the subsets in RCC52 cells, we did not detect any tumor spheroids or spheres in our in vitro studies, as detected in other types of human malignancies, such as breast and colorectal cancers in which the CD44bright/CD24-/dim rather than CD44bright/CD24bright subset are the markers for CSCs or the niche of the CSCs [13, 16]. Here, CD24 is linked to colorectal cancer.