Histone deacetylase inhibitors mediate a potent growth-inhibitory effect in cancer cells through induction of cell-cycle arrest and apoptosis. Moreover, these agents significantly induce transcriptional activation of nuclear factor κB, as well as p21 regulated by protein kinase C, and are thought to negatively influence the ability of histone deacetylase inhibitor to effectively mediate apoptosis. This study aimed to evaluate the effect of calphostin C (a protein kinase C inhibitor) on trichostatin A (a histone deacetylase inhibitor)-mediated upregulation of nuclear factor κB and p21 promotor transcriptional activity, as well as induction of apoptosis in lung and esophageal cancer cells. Cultured lung and esophageal cancer cells were treated with calphostin C and trichostatin A. Nuclear factor κB transcriptional activity was quantitated by using the nuclear factor κB-luciferase assay. Transcription of p21 gene and p21 protein levels was evaluated by using the p21 promoter-luciferase assay and the p21 enzyme-linked immunoassay, respectively. Apoptosis was evaluated by using the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-based ApoBrdU assay. Levels of expression of nuclear factor κB-dependent antiapoptotic and proapoptotic proteins were evaluated by means of Western blotting. Exposure of lung or esophageal cancer cells to trichostatin A resulted in a dose- and cell-dependent 2-fold to greater than 20-fold increase of nuclear factor κB and p21 transcriptional activity. Treatment with trichostatin A and calphostin C led to a 50% to 90% decrease of trichostatin A- mediated upregulation of nuclear factor κB and p21 activation. Inhibition of nuclear factor κB activity resulted in significant reduction (30% to >99%) of trichostatin A- mediated activation of not only nuclear factor κB transcription but also p21 promotor activity. Importantly, 90% to 96% of thoracic cancer cells under-went apoptosis after exposure to the combination of trichostatin A plus calphostin C. Inhibition of protein kinase C abrogates trichostatin Amediated upregulation of nuclear factor κB transcriptional activity and p21 expression that is associated with profound induction of apoptosis in lung or esophageal cancer cells. Protein kinase C might be a novel target for enhancing the efficacy of histone deacetylase inhibitor in cancer therapy.
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine
- Cardiology and Cardiovascular Medicine