Background: Analysis of biopsies from a recent clinical trial suggested that Depsipeptide FK228 (DP) inhibits Aurora kinase expression in lung cancer cells. The present study was undertaken to confirm and extend these observations.
Results: Aurora A and B mRNA levels in lung cancer cells were considerably higher than levels in normal pulmonary epithelia. DP, TSA and SAHA inhibited Aurora A, Aurora B and survivin expression with kinetics that were remarkably similar within individual cell lines, and appeared to coincide with p53 expression status. These effects were not observed following treatment with geldanamycins. Inhibition of Aurora B transcription coincided with decreased H3K9Ac and H3K4Me2 activation marks, and accumulation of H3K9Me3, as well as MBD1, MBD2 and MBD3 repression marks within the minimal Aurora B promoter. Knockdown of MBD1, -2 or -3 did not reproducibly abrogate inhibition of Aurora or survivin expression by DP or TSA. DP and TSA decreased expression and altered localization of Aurora kinases and survivin, resulting in mitotic catastrophe in lung cancer cells.
Methods: Aurora A, and Aurora B levels in lung cancer cells and normal respiratory epithelia were assessed using quantitative RT-PCR techniques. These methods, as well as as Western blots were used to examine expression of Auroras A/B, and several related genes/proteins in lung cancer cells exposed to DP, TSA, SAHA and geldanamycins. Transient transfection promoter-reporter assays, and chromatin immunoprecipitation (ChIP) techniques were used to examine DP-mediated changes in activity and chromatin structure of the Aurora B promoter. Confocal imaging techniques were used to examine the effects of DP and TSA on mitotic progression in lung cancer cells.
Conclusions: Novel transcriptional regulatory mechanisms involving Aurora kinase and survivin appear to contribute to cytotoxicity mediated by HDAC inhibitors in lung cancer cells.