CD44 and lung cancer: In this study, we have used a range of established and patient-derived lung cancer cell lines (PDCL) to show cells with high ALDH and CD44 co-expression (ALDHhiCD44hi) possessed in vitro and in vivo TIC properties with enhanced tumorigenicity and drug resistance compared to the low-expressing (ALDHloCD44lo) compartment or un-selected cells.