Investigation on the mechanism of dichloroacetate (DCA) induced apoptosis in breast cancer.

Sub-category: Pro-Apoptotic Agents
Category: Developmental Therapeutics: Molecular Therapeutics
Meeting: 2009 ASCO Annual Meeting
Citation: J Clin Oncol 27, 2009 (suppl; abstr e14637)
Abstract No: e14637
New this year -- Publication-only abstracts, which are selected to be published in conjunction with the 2009 Annual Meeting but not presented at the Meeting, can be found online only.

The publication-only abstracts are not included in the print or CD versions of the ASCO Annual Meeting Proceedings Part I, but they are citable to this issue of the Journal of Clinical Oncology as a supplement (see citation on left)


Author(s): L. Ko, J. Allalunis-Turner; Cross Cancer Institute, Edmonton, AB, Canada
Abstract:
Background: DCA is a generic, orally available, small molecule metabolic modulator that has an established history in the treatment of mitochondrial diseases and lactic acidosis. DCA inhibits pyruvate dehydrogenase kinase (PDK), an inhibitor of pyruvate dehydrogenase, a key enzyme in glucose metabolism. DCA preferentially shifts glucose metabolism in cancer cells from glycolysis to glucose oxidation, reversing the unique aerobic glycolysis found in solid tumors. DCA induced apoptosis in cancer cells as evidenced by the efflux of cytochrome c and apoptosis-inducing factor from the mitochondria. Recent studies suggested apoptosis induction by DCA in glioblastoma, endometrial, prostate, and non-small cell lung cancers. In this study we attempt to establish a link between DCA and apoptosis in breast cancer cell lines. Methods: Six breast cancer cell lines were investigated (BT474, MCF-7, MDA-MB231, MDA- MB468, SKBR3, T47D). Quantitative real-time polymerase chain reaction (RT-PCR) was performed using Taqman probes to identify increased DNA templates of PDK isoforms 1-4, using DCA concentrations from 0 to 20mM. Western blots were performed to identify increased expression of PDK isoforms and correlate findings with Taqman. MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)- 2-(4-sulfophenyl)-2H-tetrazolium) assays were performed to measure decreased mitochondrial activity and cytotoxicity. Flow cytometry using annexin V and propidium iodide was performed to measure apoptosis and cell death. Results: RT-PCR showed increased DNA expression of all PDK isoforms in MDA-MB231 cells after DCA treatment. The effect was most pronounced at 10mM concentration. 10mM of DCA also increased DNA expression of all PDK isoforms in MCF-7 cells, and PDK1 in T47D cells. MTS assays showed increased cell kill and decreased mitochondrial activity in all six cell lines, with IC50 ranging between 20mM and 30 mM. Flow cytometry showed increased apoptosis induced by DCA at IC50 for BT474 and MCF-7 cell lines. Conclusions: Apoptosis appears to play a role in the mechanism of DCA in breast cancer, with increased PDK isoform expressions, cytotoxicity and decreased mitochondrial activity. Data from flow cytometry suggested DCA-induced apoptosis in two cell lines.