The human lung adenocarcinoma HCC-827 cells were used to generate the gefitinib-resistant HCC-827/GR cells; the expression of ALDH subtype in either HCC-827 or HCC-827/GR was detected by flow cytometry; The proliferative capacity and sensitivity to gefitinib of hcc-827/GR cells were analyzed by MTT assay before and after treatment with 100 μmol/L diethyllaminaldehyde (DEAB); Real-time quantitative PCR was used to detect the expression of ALDH subtypes at mRNA levels in hcc-827 cells and hcc-827/GR cells. The gene discussed is LDHA; the disease is hepatocellular carcinoma.