Effect of antisense RNA targeting polo-like kinase 1 on cell cycle and proliferation in A549 cells

Background Expression of polo-like kinase 1 ( PIk1) is elevated in lung cancer and has been proposed as having prognostic value and related to resistance to chemotherapy and radiation. In addition, PIk1 has several functions in mitotic progression. In this study, the authors investigated the effect of PIk1 depletion on cell cycle progression and proliferation in A549 cells, a lung cancer cell line. Methods A recombinant plasmid containing antisense RNA targeting PIk1 ( pcDNA3-PIk1) was transfected into A549 cells. Reverse transcription-polymerase chain reaction and Western blot were used to examine PIk1 gene expression. Cell proliferation was evaluated by direct cell counting and bromodeoxyuridine ( BrdU) labelling. Cell cycle and apoptosis were examined by flow cytometry. Expression of a-tubulin was detected by immunofluorescence, and the inhibition rate (IR) by chemotherapeutic agents was determined by 3-(4, 5-dimethylthiazol-2-yl) 2, 5-diphenyl-tetrazolium bromide assay. Results After transfection into A549 cells, pcDNA3-PIk1 reduced PIk1 mRNA by 46.75% for 24 hours and by 61.84% for 48 hours. PIk1 protein was significantly decreased simultaneously ( P < 0.05). Abnormal morphological changes of cells and growth inhibition were observed in pcDNA3-PIk1 transfected groups. The BrdU labelling index was 25.59% 48 hours after transfection, which was significantly lower than that of the control groups ( P < 0.05). Forty-eight hours after transfection, there showed absence of microtubule polymerization and spindle abnormalities in staining for a-tubulin. A549 cells showed a strong G(2)/M arrest and apoptosis 72 hours post transfection. IR of vinorelbine in pcDNA3-PIk1 transfected groups was significantly higher than that of the other groups ( P < 0.05, respectively). Conclusions PIk1 depletion interferes with spindle formation, induces cell cycle arrest and apoptosis, and consequently inhibits cell proliferation in A549 cells. Moreover, it sensitizes lung cancer cells to chemotherapy.