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The principal unmet need in BRAFV600E-positive melanoma is lack of an adequate therapeutic strategy capable of overcoming resistance to clinically approved targeted therapies against oncogenic BRAF and/or the downstream MEK1/2 kinases. We previously discovered that copper (Cu) is required for MEK1 and MEK2 activity through a direct Cu–MEK1/2 interaction. Repurposing the clinical Cu chelator tetrathiomolybdate (TTM) is supported by efficacy in BRAFV600E-driven melanoma models, due in part to inhibition of MEK1/2 kinase activity. However, the antineoplastic activity of Cu chelators is cytostatic. Here, we performed high-throughput small-molecule screens to identify bioactive compounds that synergize with TTM in BRAFV600E-driven melanoma cells. Genetic perturbation or pharmacologic inhibition of specific members of the BCL2 family of antiapoptotic proteins (BCL-W, BCL-XL, and MCL1) selectively reduced cell viability when combined with a Cu chelator and induced CASPASE-dependent cell death. Further, in BRAFV600E-positive melanoma cells evolved to be resistant to BRAF and/or MEK1/2 inhibitors, combined treatment with TTM and the clinically evaluated BCL2 inhibitor, ABT-263, restored tumor growth suppression and induced apoptosis. These findings further support Cu chelation as a therapeutic strategy to target oncogene-dependent tumor cell growth and survival by enhancing Cu chelator efficacy with chemical inducers of apoptosis, especially in the context of refractory or relapsed BRAFV600E-driven melanoma. Significance: This study unveils a novel collateral drug sensitivity elicited by combining copper chelators and BH3 mimetics for treatment of BRAFV600E mutation-positive melanoma.

Pancreatic ductal adenocarcinoma (PDA) remains one of the most difficult cancers to effectively treat. Over 90% of PDA are driven by oncogenic KRAS, which leads to metabolic rewiring in the cell, including increased glucose uptake and increased flux through the hexosamine biosynthesis pathway (HBP). The HBP, which branches off from glycolysis at fructose-6-phosphate and also requires glutamine, acetyl-CoA, and uridine triphosphate, is responsible for synthesizing uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), a major substrate for glycosylation in the cell. UDP-GlcNAc can also be generated through recycling of GlcNAc via N-acetylglucosamine kinase (NAGK). Glycans are important for maintaining protein homeostasis and cell signaling. However, while there is increased HBP flux in PDA and glycosylation is elevated in a range of cancers, how this is regulated and the functional significance of increased glycosylation in cancer are not well understood. Because of the multiple metabolic inputs required for UDP-GlcNAc synthesis, the HBP has been proposed as a nutrient sensing pathway. Surprisingly, however, we found that PDA cells robustly maintain both O-GlcNAc and N-glycosylation when exposed to nutrient deprivation. The enzyme N-acetylglucosamine kinase (NAGK) is upregulated under low glutamine conditions, and through stable isotope tracing studies, we demonstrate that PDA cells are able to switch to use of the salvage pathway over the HBP for generation and maintenance of the UDP-GlcNAc pool via NAGK. Together, this work points to a mechanism of metabolic flexibility in generating UDP-GlcNAC that allows PDA cells to grow in a nutrient-poor environment. Citation Format: Sydney L. Campbell, Clementina A. Mesaros, Tiffany Tsang, Michael Noji, Salisa Kruijning, Sophie Trefely, Luke Izzo, Ian A. Blair, Kathryn E. Wellen. Glutamine deprivation triggers hexosamine salvage in pancreatic cancer cells [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr C10.

Despite the high incidence of oncogenic mutations in PIK3CA, the gene encoding the catalytic subunit of phosphoinositide 3-kinase (PI3K), PI3K inhibitors have yielded little clinical benefit for breast cancer patients. Recent epidemiological studies have suggested a therapeutic benefit from aspirin intake in cancers harboring oncogenic PIK3CA. Here we show that mutant PIK3CA-expressing breast cancer cells have greater sensitivity to aspirin-mediated growth suppression than their wild-type counterparts. Aspirin decreased viability and anchorage-independent growth of mutant PIK3CA breast cancer cells independently of its effects on cyclooxygenase-2 (COX-2) and nuclear factor-kappa B (NF-κB). We ascribed the effects of aspirin to AMP-activated protein kinase (AMPK) activation, mammalian target of rapamycin complex 1 (mTORC1) inhibition, and autophagy induction. In vivo, oncogenic PIK3CA-driven mouse mammary tumors treated daily with aspirin resulted in decreased tumor growth kinetics, while combination therapy of aspirin and a PI3K inhibitor further attenuated tumor growth. Our study supports evaluation of aspirin and PI3K pathway inhibitors as combination therapy for targeting breast cancer.