apicidin and Cell-Transformation--Neoplastic

The cellular susceptibility of cancer cells to histone deacetylase (HDAC) inhibitors is increased by the etopic expression of oncogenic Ras. However, the ability of HDAC inhibitors to regulate the apoptotic pathway in human breast cancer cells is still not completely understood. In this study, the anti-proliferative effects of apicidin were compared in H-ras-transformed human breast epithelial (MCF10A-ras) and non-transformed epithelial (MCF10A) cells. MCF10A-ras cells showed a significantly higher growth rate than MCF10A cells. Apicidin significantly increased the levels of acetylated histone H3 and H4 in both cell lines. Western blot analysis and flow cytometry were used to determine if the anti-proliferative effects of apicidin in MCF10A and MCF10A-ras cells could be mediated by modulating the cell cycle. Apicidin attenuated the expression of cyclin E and CDK2 in MCF10A cells, decreased cyclin D1 and cyclin E levels in MCF10A-ras cells, and increased the levels of CDK inhibitors, p21WAF1/Cip1 and p27Kip1, in both cell lines. Notably, the levels of hyperphosphorylation of the Rb protein levels were lower in the MCF10A-ras cells after apicidin treatment. Studies on the regulation of apoptosis showed that apicidin induces the up-regulation of p53 and the downstream activation of ERK in MCF10A-ras cells. The up-regulation of p53 promoted Bax expression leading to activation of caspases-9 and -6, and eventually to apoptosis in MCF10A-ras cells. In addition, apicidin significantly increased the levels of ERK1/2 phosphorylation in MCF10A-ras cells. Therefore, the apicidin-mediated ERK pathway appears to play an important role in modulating the pro-apoptotic pathway in MCF10A-ras cells.

Topics: Acetylation; Apoptosis; Breast; Cell Cycle; Cell Cycle Proteins; Cell Line, Tumor; Cell Transformation, Neoplastic; Enzyme Activation; Enzyme Inhibitors; Epithelial Cells; Female; Histone Deacetylase Inhibitors; Histones; Humans; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Peptides, Cyclic; Proto-Oncogene Proteins p21(ras); Transcription Factor AP-1; Transfection

Cancer metastasis represents the most important cause of cancer death and agents that may inhibit tumor cell invasion have been extensively pursued. In the present study, we have examined the anti-invasive effect of apicidin [cyclo(N-O-methyl-L-tryptophanyl-L-isoleucinyl-D-pipecolinyl -L-2-amin o-8-oxodecanoyl)], a fungal metabolite that was identified as an antiprotozoal agent known to inhibit parasite histone deacetylase (HDAC). We show that apicidin significantly inhibits H-ras-induced invasive phenotype of MCF10A human breast epithelial cells in parallel with a specific downregulation of matrix metalloproteinase (MMP)-2, but not MMP-9. We also show that apicidin induces a morphological reversal and growth inhibition of H-ras MCF10A cells similar to that induced by other HDAC inhibitors. Taken in conjunction with the fact that uncontrolled ras activation is probably the most common genetic defect in human cancer cells, our data showing the anti-invasive and detransforming activities of apicidin in H-ras-transformed MCF10A cells may suggest a potential use of HDAC inhibitors for treatment of cancer.

Topics: Breast; Cell Division; Cell Line, Transformed; Cell Transformation, Neoplastic; Dose-Response Relationship, Drug; Down-Regulation; Enzyme Inhibitors; Epithelial Cells; Genes, ras; Growth Inhibitors; Histone Deacetylase Inhibitors; Humans; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Peptides, Cyclic; Phenotype