As cancer stem cell (CSC) has been reported to enhance aggressiveness and metastasis of cancer cells, we used fluorescence activated cell sorter (FACS) analysis to determine the populations of CD44+ cells in docetaxel-resistant PC/DX25 cells and DU/DX50 cells as well as their parental PC-3 and DU-145 cells. This evidence concerns the gene CD44 and cancer.