In the different lung cancer cell lines and patient-derived lung cancer cells, an ALDHhi/CD44hi subset manifested the highest attributes of stem cell phenotypes, higher invasion capacities, expression of pluripotency genes, epithelial-mesenchymal transition (EMT) transition genes, and stronger in vivo tumorigenicity than other types of sorted ALDH/CD44 and unsorted cells, indicating the competence of ALDH/CD44 in identifying and maintaining tumor-initiating cells [51]. Here, CD44 is linked to lung cancer.