Abstract C156: PKM2 activation sensitizes cancer cells to growth inhibition by 2-deoxyglucose.

Introduction: This study proposes the use 2-deoxyglucose (2DG) with the PKM2 activator, TEPP46 as a novel drug combination for cancer chemotherapy. Pyruvate kinase converts phosphoenolpyruvate to pyruvate in the last step of glycolysis. The M2 isoform of pyruvate kinase, PKM2, is expressed in all cancer cell lines tested so far. PKM2 exists either as a dimer or a more active, tetrameric form. The less active dimer is thought to favor rapid cell division by the diversion of glycolytic intermediates into biosynthetic pathways. Recently, small molecule activators of PKM2 have been shown to inhibit xenograft tumor growth. However, these activators do not inhibit cell growth in culture at physiological conditions and have only been shown to prevent tumor formation in mice. As PKM2 activation accelerates the last step of glycolysis, we hypothesize that activator treatment will also increase overall glucose consumption. 2DG is a glucose analog that acts as a competitive inhibitor of glucose metabolism and is currently in Phase I/II clinical trial for several solid tumors. However, 2DG monotherapy has shown limited efficacy and at high doses, 2DG causes hypoglycemia in patients. The use of 2DG with TEPP46 has the potential of lowering the dose of 2DG needed for therapeutic effects as well as a possible synergistic effect on cancer growth inhibition. Methods: MDA-MB-231, 468, and MCF7 breast cancer cells were grown in DMEM with 25 mM glucose, 4 mM glutamine, and 10% fetal bovine serum. Viability assays were performed using the CellTiter 96 Aqueous One Solution (Promega, WI) in 96-well plates seeded with 2,000 cells per well. 2DG was used at 1 mM in all experiments while TEPP46 was diluted from a 1000x stock in DMSO to a final concentration of 30 μM in cell culture medium. Results: 72 hr post-treatment, cells dosed with TEPP46 alone and 2DG alone demonstrated no appreciable difference in viability compared to DMSO (vehicle) treated cells. However, all three breast cancer cell lines showed a reduced viability, ranging from 56 to 80% of control when treated with a combination of TEPP46 and 2DG. This was most pronounced in the MCF7 cell line that displayed a 55% reduction in viability compared to vehicle treatment. Discussion: PKM2 has recently received much attention as a tumor-specific drug target and small molecule activators such as TEPP46 have been demonstrated to prevent tumor formation in mice. TEPP46 limited efficacy in physiological cell culture conditions and is unlikely to have a therapeutic effect in established tumors. This study is the first to combine a PKM2 activator with another chemotherapeutic, 2DG that is currently in clinical trials. Cell culture studies in three different lines have been encouraging; combination treatment resulted in a reduction of viability that is not evident when either drug is used in isolation. Encouragingly, all studies were performed in cell culture media with a high concentration of glucose and glutamine. The efficacy of this combination is currently be investigated in vivo. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C156. Citation Format: Sui-Seng Tee, Jae Mo Park, Daniel Spielman. PKM2 activation sensitizes cancer cells to growth inhibition by 2-deoxyglucose. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C156.