['Multidrug resistance protein 4 (MRP4), also known as ATP-cassette binding protein 4 (ABCC4), is a member of the MRP/ABCC subfamily of ATP-binding cassette transporters, which are capable of pumping a wide variety of drugs out of the cell. However, little is known about the function of ABCC4 in the proliferation of lung cancer cells.', 'ABCC4 mRNA and protein levels in lung cancer cell lines were measured by real-time polymerase chain reaction and Western blot, respectively. A lentivirus-mediated RNA interference technique was used to inhibit ABCC4 mRNA expression in A549 and 801D cells. The function of ABCC4 in cell growth was investigated by MTS and colony formation assays. The role of ABCC4 in cell cycle progression was evaluated by flow cytometry and Western blot analysis. ABCC4 mRNA levels in 30 pairs of tumors and corresponding matched adjacent normal tissues from non-small cell lung cancer patients were detected by real-time polymerase chain reaction.', 'ABCC4 was highly expressed in lung cancer cell lines. ABCC4 expression was markedly downregulated in A549 and 801D cells using the RNA interference technique. Suppression of ABCC4 expression inhibited cell growth. The percentage of cells in G1 phase was increased when ABCC4 expression was suppressed. Phosphorylation of retinoblastoma protein was weakened, originating in the downregulation of ABCC4. ABCC4 mRNA was highly expressed in lung cancer tissue and lung cancer cell lines.'] Is aBCC4 required for cell proliferation and tumorigenesis in non-small cell lung cancer?