Lentivirus-mediated knockdown of CTDP1 inhibits lung cancer cell growth in vitro

CTDP1 catalyzes serine phosphorylation and dephosphorylation of the mobile carboxy-terminal domain of the RNA polymerase II. It is conserved among eukarya and is essential for cell growth for its ability in regulation of transcription machinery. However, its function in the process of tumorigenesis is unclear. In the present study, we aim to explore the roles of CTDP1 in the progression of human lung cancer. To our knowledge, this is the first study that reports the functions of CTDP1 in human lung cancer. We first detected the expression level of CTDP1 in four human lung cancer cell lines: H-125, H1299, LTEP-A-2 and NCI-H446 by semiquantitative RT-PCR. We compared the expression level of CTDP1 in lung cancer tissues and paired adjacent normal tissues on 29 pathologically confirmed patients by real-time quantitative PCR. To further explore the effect of CTDP1 on cell proliferation, a lentiviral vector expressing CTDP1 short hairpin RNA (shRNA) was constructed and infected into human lung cell lines H1299. Interference efficiency was determined by western blot analysis and real-time quantitative PCR. The effects of knockdown of CTDP1 on cell growth, cell cycle and apoptosis and cell colony formation were explored by Cellomics, fluorescence-activated cells sorting and fluorescence microscopy, respectively. CTDP1 was expressed in all four human lung cancer cell lines. The expression of CTDP1 in tumor tissues was significantly higher than paired adjacent normal tissues in 29 patients with lung cancer. The expression of CTDP1 was markedly reduced in cells infected with lentivirus delivering shRNA against CTDP1. Inhibition of CTDP1 expression significantly suppressed cell growth, induced G0/G1 phase arrest and repressed cell colony formation. Our results demonstrated that CTDP1 was upregulated in human lung cancer tissues. In addition, it implied that CTDP1 played an important role in cell proliferation and may be a useful therapeutic target in human lung cancer.