To explore the role of ALDH isozymes in ALDH-positive NSCLC stem cells and the mechanism underlying the activity of DSF/Cu, we used specific siRNAs to silence ALDH1A1, ALDH1A3 and ALDH3A1 in NCI-H1299 cells. The gene discussed is ALDH3A1; the disease is non-small cell lung carcinoma.