CD44 and nasopharyngeal carcinoma: CD44+ cells were also found as a subpopulation of the parental C666-1 cells (5.28±1.29%) and three NPC xenografts, xeno-666 (12.31±1.97%), xeno-2117 (9.58±1.80%), and C17 (17.31±1.76%) (Fig. 1D).