Abstract 4070: Treatment with the MEK inhibitor U0126 induces increased lactate production in prostate and breast cancer cell lines
Authors: Lodi Alessia , Woods Sarah , Danforth Robert , Ronen Sabrina M. 
Published: July 2012

Abstract
Introduction. In this study we investigated the metabolic consequences of U0126, a highly selective MEK1/2 inhibitor, in human prostate and breast cancer cell lines using 1H and 13C magnetic resonance spectroscopy (MRS) and gene expression data.
Methods. Prostate (PC3 and LNCaP) and breast (MCF7) human cancer cells were treated for 48 h with the IC50 dose of U0126. 1H MRS data were acquired from cell extracts and repeated univariate statistical testing with false discovery rate correction was performed to determine significant changes in metabolite levels. The rate of glycolysis was determined from dynamic studies in live cells using 13C MRS to monitor the metabolism of 1-13C-labeled glucose. Protein and gene expression levels were measured using Western blotting and microarray analysis.
Results and Discussion. The effect of U0126 was confirmed by western blot analysis demonstrating a drop in p-ERK. The univariate statistical analysis revealed that the 48 h drug treatment induced several metabolic changes including depletion of intracellular aspartate, succinate and phosphocholine in the prostate cells. However, one of the most significant metabolic change in all three cell lines was a substantial increase in intracellular lactate levels following treatment, with lactate up 134±16% (p=0.002), 149±20% (p=0.001) and 213±43% (n=2) of control in PC3, LNCaP and MCF7 cells respectively. Dynamic studies in live MCF7 cells were in line with the extract data and showed that the rate of lactate production increased following treatment 169±43% from 260±98 fmol/cell/hour to 439±114 fmol/cell/hour (p=0.03). Preliminary studies in PC3 cells showed a similar trend.
Consistent with the metabolic observations, overexpression of genes associated with glycolysis including PFKFB3, PDK1, HK2, and GLUT1 was observed in PC3 cells pointing to an increase in glycolytic enzymes induced by U0126 treatment. In an effort to explain this observation we assessed the expression of other signaling proteins and found that although U0126 inhibits its target kinase, increased Akt phosphorylation was also observed in the PC3 cells. Importantly Akt activation was previously reported to mediate an increase in glycolysis. We therefore hypothesize that the observed increases in lactate production and its intracellular accumulation following inhibition of MAPK kinase signaling result from activation of the PI3K/Akt pathway observed in our cells.
Conclusion. Deregulation of the MAPK pathway is often involved in oncogenesis, and therefore inhibitors of the pathway are being investigated as targeted cancer therapeutics. Our results highlight the value of MRS in identifying metabolic consequences of treatment that may inform on molecular drug action.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4070. doi:10.1158/1538-7445.AM2011-4070