CD44 and neoplasm: Infact, Liu et al. found CD44+/CD24– populationswere thrice as invasive as ALDH+ populations in the TNBCcell line SUM149. While ALDH+ populations had significantly higher tumor initiating capacity thanCD44+/CD24– cells in TNBC patient-derivedxenograft (PDX) models. This observationdoes not suggest that M-CSCs are more critical than E-CSCs; rather,it indicates that each cell type possesses distinct functions.