CD44 and neoplasm: The potential nanotherapeutic approaches utilized for targeting CSCs in the past few years include crucial factors required for the survival of CSCs in the tumor microenvironment, such as specific surface biomarkers (CD44, CD133, EpCAM, aldehyde dehydrogenases), drug efflux pumps (ABC transporters) expression, different metabolic pathways, and signaling pathways (Wnt/β-catenin, Notch and Hedgehog) [178,179].