To delineate the role of radiation-induced CD44 expression in radioresistant colorectal cancer cells, we isolated both CD44 positive (CD44+) and negative (CD44−) cells in HCT116 and DLD1 cells following irradiation using anti-CD44-FITC antibodies by FACS, and the expression of CD44 in both CD44+ and CD44− cells is shown in Figure 2A. Since the CD44 marker correlated with the features of CSCs in colorectal cancers [19,20], we evaluated the properties of colorectal CSCs including metastatic potential and self-renewal. This evidence concerns the gene CD44 and colorectal cancer.