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Dichloroacetate induces apoptosis and cell-cycle arrest in colorectal cancer cells.

ABSTRACT: BACKGROUND: Cancer cells are highly dependent on glycolysis. Our aim was to determine if switching metabolism from glycolysis towards mitochondrial respiration would reduce growth preferentially in colorectal cancer cells over normal cells, and to examine the underlying mechanisms. METHODS: Representative colorectal cancer and non-cancerous cell lines were treated with dichloroacetate (DCA), an inhibitor of pyruvate dehydrogenase kinase. RESULTS: Dichloroacetate (20 mM) did not reduce growth of non-cancerous cells but caused significant decrease in cancer cell proliferation (P=0.009), which was associated with apoptosis and G(2) phase cell-cycle arrest. The largest apoptotic effect was evident in metastatic LoVo cells, in which DCA induced up to a ten-fold increase in apoptotic cell counts after 48 h. The most striking G(2) arrest was evident in well-differentiated HT29 cells, in which DCA caused an eight-fold increase in cells in G(2) phase after 48 h. Dichloroacetate reduced lactate levels in growth media and induced dephosphorylation of E1alpha subunit of pyruvate dehydrogenase complex in all cell lines, but the intrinsic mitochondrial membrane potential was reduced in only cancer cells (P=0.04). CONCLUSIONS: Pyruvate dehydrogenase kinase inhibition attenuates glycolysis and facilitates mitochondrial oxidative phosphorylation, leading to reduced growth of colorectal cancer cells but not of non-cancerous cells.

SUBMITTER: Madhok BM

PROVIDER: S-EPMC2883702 | biostudies-other | 2010 Jun

REPOSITORIES: biostudies-other

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Project description:BackgroundThe Securinega-type alkaloids occur in plants belonging to Euphorbiaceae family. One of the most widely distributed alkaloid of this group is securinine, which was identified next to allosecurinine in Phyllanthus glaucus (leafflower). Recently, some Securinega-type alkaloids have paid attention to its antiproliferative potency towards different cancer cells. However, the cytotoxic properties of allosecurinine have not yet been evaluated.MethodsThe cytotoxicity of the extract, alkaloid fraction obtained from P. glaucus, isolated securinine and allosecurinine against HeLa cells was evaluated by real-time xCELLigence system and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was detected by annexin V and 7-amino-actinomycin (7-AAD) staining and confirmed with fluorescent Hoechst 33342 dye. The assessment of mitochondrial membrane potential (MMP), reactive oxygen species (ROS) generation, the level of extracellular signal-regulated protein kinases 1 and 2 (ERK1/2), caspase-3/7 activity and cell cycle analysis were measured by flow cytometry. The enzymatic activity of caspase-9 was assessed by a luminometric assay. The expression of apoptosis associated genes was analyzed by real-time PCR.ResultsThe experimental data revealed that securinine and the alkaloid fraction were significantly potent on HeLa cells growth inhibition with IC50 values of 7.02 ± 0.52 ?g/ml (32.3 ?M) and 25.46 ± 1.79 ?g/ml, respectively. The activity of allosecurinine and Phyllanthus extract were much lower. Furthermore, our study showed that the most active securinine induced apoptosis in a dose-dependent manner in the tested cells, increased the percentage of ROS positive cells and depolarized cells as well as stimulated the activity of ERK1/2, caspase-9 and -3/7. Securinine also induced cell cycle arrest in S phase. Real-time PCR analysis showed high expression of TNFRSF genes in the cells stimulated with securinine.ConclusionsSecurinine induces apoptosis and activates cell cycle checkpoints in HeLa cells which is associated with oxidative stress. The results indicate that the mitochondrial pathway is involved in the programmed cell death.

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Dichloroacetate induces apoptosis and cell-cycle arrest in colorectal cancer cells.

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