For example, tumor-initiating cells isolated from MMTV-Wnt-1 mammary tumors preferentially utilize glycolysis over OXPHOS for energy production, in contrast to non-tumorigenic cancer cells.12 In addition, glycolysis is the preferred metabolic process in radio-resistant sphere-forming cells in nasopharyngeal carcinoma49 and CD133+CD49f+ tumor-initiating cells in hepatocellular carcinoma.50 Metabolic switch from OXPHOS to glycolysis is required for the characteristics of CD44+CD24lowEPCAM+ breast CSCs, due to decreased ROS levels. Here, CD44 is linked to cancer.