Tumor xenografts derived by the injection of purified HCT116- and HT29-CD133+CD44+ cells were digested to isolate CD133−CD44− and CD133+CD44+ cells, and 1 × 103 CD133+CD44+ cells or 5 × 107 CD133−CD44− cells from the first-generation xenografts were subcutaneously transplanted into secondary mice. Here, CD44 is linked to neoplasm.