Metabolic reprogramming in tumors represents a potential therapeutic target. Herein we used shRNA depletion and a novel lactate dehydrogenase (LDHA) inhibitor, GNE-140, to probe the role of LDHA in tumor growth in vitro and in vivo. In MIA PaCa-2 human pancreatic cells, LDHA inhibition rapidly affected global metabolism, although cell death only occurred after 2 d of continuous LDHA inhibition. Pancreatic cell lines that utilize oxidative phosphorylation (OXPHOS) rather than glycolysis were inherently resistant to GNE-140, but could be resensitized to GNE-140 with the OXPHOS inhibitor phenformin. Acquired resistance to GNE-140 was driven by activation of the AMPK-mTOR-S6K signaling pathway, which led to increased OXPHOS, and inhibitors targeting this pathway could prevent resistance. Thus, combining an LDHA inhibitor with compounds targeting the mitochondrial or AMPK-S6K signaling axis may not only broaden the clinical utility of LDHA inhibitors beyond glycolytically dependent tumors but also reduce the emergence of resistance to LDHA inhibition.

Although glycolysis is substantially elevated in many tumors, therapeutic targeting of glycolysis in cancer patients has not yet been successful, potentially reflecting the metabolic plasticity of tumor cells. In various cancer cells exposed to a continuous glycolytic block, we identified a recurrent reprogramming mechanism involving sustained mTORC1 signaling that underlies escape from glycolytic addiction. Active mTORC1 directs increased glucose flux via the pentose phosphate pathway back into glycolysis, thereby circumventing a glycolysis block and ensuring adequate ATP and biomass production. Combined inhibition of glycolysis and mTORC1 signaling disrupted metabolic reprogramming in tumor cells and inhibited their growth in vitro and in vivo. These findings reveal novel combinatorial therapeutic strategies to realize the potential benefit from targeting the Warburg effect.

Cancer cells harboring MET amplification display striking sensitivity to selective small molecule inhibitors of MET kinase, prompting their clinical evaluation. Similar to the experience with traditional therapeutics, most patients responding to treatment with such molecular targeted therapeutics ultimately relapse with drug-resistant disease. In this study we modeled acquired resistance to experimental MET kinase inhibitor PF2341066 in MET-amplified non-small cell lung carcinoma (NSCLC) cell lines to identify drug resistance mechanisms that may arise in clinic. We found that activation of the epidermal growth factor receptor (EGFR) pathway emerges as a resistance mechanism in MET-amplified cells after prolonged exposure to PF2341066. Whereas combined inhibition of MET and EGFR kinases in MET-dependent NSCLC cells did not enhance their initial sensitivity to PF2341066, this combination dramatically suppressed the eventual emergence of drug-resistant clones after prolonged drug exposure. Conversely, activation of the EGFR pathway increased the yield of PF2341066-resistant clones, confirming the significance of this pathway in conferring resistance. Our findings support an intimate relationship between the EGFR and MET signaling pathways in NSCLC, and they suggest that combination treatment with MET and EGFR kinase inhibitors may be beneficial in MET-amplified NSCLC by reducing selection for drug resistant clones.