Synthesis and biological evaluation of small molecule GLUT inhibitors that cause glucose starvation in cancer

Abstract

Deregulation of cellular metabolism has been well established as one hallmark of cancer. Increased aerobic glycolysis in cancer cells, termed the Warburg effect, is associated with an overexpression of different glucose transporter isoforms, especially GLUT-1 but also GLUT-3. To date, numerous GLUT inhibitors have been reported to induce cell death in cancer, yet improvement of selectivity and potency as well as unspecific toxicity of such inhibitors remain major challenges. The piperazin-2-one compound class was identified in a cancer cell-based screen to potently inhibit the uptake of 2-deoxyglucose (2-DG). Synthesis and testing of structural analogues revealed a conclusive structure-activity relationship with its most active enantiomerically pure analogue Glutor (GLucose Uptake inhibiTOR) that inhibited 2-DG uptake with a low nanomolar efficacy in a GLUT-1, -2, -3-selective manner. Furthermore, Glutor reduced the growth of a wide range of monolayer cultured cancer cell lines (2D) and in physiologically more relevant context (3D) while leaving non-malignant cells unaffected. An observed upregulation of GLUT-1 and GLUT-3 expression upon glucose starvation indicates the necessity of a GLUT-1/-3 selectivity profile of small molecular GLUT inhibitiors in order to fully restrict cellular glucose uptake over time. Furthermore, the metabolic plasticity of cancer led to an increased sensitivity towards glucose uptake restriction upon simultaneous inhibition of other metabolic pathways such as glutaminolysis via glutaminase inhibitor CB-839 or oxidative phosphorylation via complex I inhibitor Aumitin. Hence, combinatorial treatment approaches revealed a promising strategy to restrict cancer cell growth more efficiently. Most results obtained in this thesis with Glutor could be confirmed as universal for small molecule glucose uptake inhibitors, irrespectively of their GLUT isoform selectivity.