Interestingly, the expression level of CD24, a gene whose absence/lower expression level is used as a CSC marker in breast cancer but whose high expression level is proposed as a CSC marker in colon cancer cells [23, 33, 35, 36, 50–53], is lower in both LS411N-5FU-R and SW620-5FU-R cells than that in LS411N-CD133+ and SW620-CD133+ cells (Figure 4C). Here, CD24 is linked to breast cancer.