Abstract 4958: AMPK as a target to overcome hypoxia-induced treatment resistance in tumors.
Authors: Busk Morten , Soerensen Brita S. , Jakobsen Steen , Honoré Bent , Overgaard Jens , Horsman Michael R. 
Published: August 2014

Purpose: AMP-activated protein kinase (AMPK) responds to ATP depletion and orchestrates cell-adaptive responses to energy-restricted conditions like low glucose or hypoxia. AMPK activation stimulates energy producing pathways and inhibits ATP-consuming biosynthesis and controls post-irradiation metabolism. Pharmacological stimulation of AMPK to mimic energetic stress slows tumor growth, possible by inhibition of proliferation.

However, since AMPK is critically involved in cell survival during energy restrictions (a tumor hallmark), inhibition of AMPK may effectively kill treatment resistant hypoxic tumor cells. In this study we investigate the antitumor effect of AMPK targeting using the AMPK inhibitor Compound C (CC).

Methods: Since hypoxia-induced changes in energy-metabolism (e.g., Pasteur effect) is much more pronounced in cells inherently dependent on oxidative phosphorylation than in the typical glycolytic tumor energetic phenotype, cell lines representing both phenotypes were included. Cell viability, proliferation and energy metabolism (glucose consumption/lactate synthesis) was assessed during acute (3h) or chronic (48h) energy-replete (5 mM glucose and 21% O2) or energy-deplete (2 mM glucose and 0% O2) conditions in the absence or presence of CC. Furthermore, CC treated and untreated mice bearing SCCVII tumors were administered with pimonidazole (hypoxia marker) and FDG (glucose analogue) followed by tissue section analysis of the microregional distribution of hypoxia and glucose consumption.

Results: Long-term CC treatment reduced cell viability/proliferation and suppressed glucose consumption and lactate synthesis both under energy replete and deplete conditions, but the relative effects were more pronounced during energy restriction, suggesting that treatment may show specificity towards cells in the hostile tumor microenvironment. Also acute changes in energy metabolism 3h following transition to energy-replete conditions were observed during CC treatment. In accordance, the hypoxia-elicited stimulation of glucose use (the Pasteur effect) was fully suppressed in CC-treated cells, resulting in much more dramatic effects on glycolytic flux in SiHa cells (atypical non-glycolytic phenotype) than in FaDuDD cells (typical glycolytic phenotype). Currently, we are investigating if CC treatment affects the tumor microenvironment in tumor-bearing mice and whether CC treatment sensitize tumors to irradiation.

Conclusions: CC fully suppressed the hypoxia-elicited Pasteur effect which may be responsible for cell death. Metabolic effects were much more pronounced in inherently non-glycolytic than in glycolytic tumor cells. In vivo testing of the efficacy/specificity of CC treatment in tumor bearing mice is ongoing.

Citation Format: Morten Busk, Brita S. Soerensen, Steen Jakobsen, Bent Honoré, Jens Overgaard, Michael R. Horsman. AMPK as a target to overcome hypoxia-induced treatment resistance in tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4958. doi:10.1158/1538-7445.AM2013-4958