CD44 and neoplasm: Furthermore, identification GSCs targeting specific stem cell-surface biomarkers (e.g. Aldehyde dehydrogenase [ALDHs], CD44, CD90, CD133), and unique signaling pathways (e.g. Wnt/b-catenin, Notch, TGF-β, Hedgehog) are under investigation to successfully eliminate GSCs to prevent tumor metastasis and recurrence (145).