In conclusion, we showed that hypoxia specifically up-regulated CSC-sphere formation and a size of a subset of the CD44+ CSC subpopulations Through various in vitro studies, we found that hypoxia-induced Wnt/β-catenin signaling increased the occurrence of CSC-like phenotypes and the level of Id2 expression in colorectal- cancer cells. Here, CD44 is linked to colorectal cancer.