Aldehyde dehydrogenase (ALDH) activity and cell surface CD133 expression were both used as stem cell markers for NSCLC; as previously reported, the tumorigenicity of different cell populations derived from NSCLC cell lines in vivo was evaluated using the following markers: (1) CD133+ALDH- cells (enriched mesenchymal-like CSCs); (2) CD133-ALDH+ cells (enriched epithelial-like CSCs); (3) CD133+ALDH+ cells (epithelial-to-mesenchymal transition-like CSCs); and (4) CD133-ALDH- cells (differentiated tumour cells, bulk tumour cells). The gene discussed is LDHA; the disease is non-small cell lung carcinoma.