Blockade of glutamine-dependent cell survival augments antitumor efficacy of CPI-613 in head and neck cancer

Abstract

Background Alterations in metabolism are one of the emerging hallmarks of cancer cells and targeting dysregulated cancer metabolism provides a new approach to developing more selective therapeutics. However, insufficient blockade critical metabolic dependencies of cancer allows the development of metabolic bypasses, thus limiting therapeutic benefits. Methods A series of head and neck squamous cell carcinoma (HNSCC) cell lines and animal models were used to determine the efficacy of CPI-613 and CB-839 when given alone or in combination. Glutaminase 1 (GLS1) depletion was achieved by lentiviral shRNAs. Cell viability and apoptosis were determined in HNSCC cells cultured in 2D culture dish and SeedEZ™ 3D scaffold. Molecular alterations were examined by Western blotting and immunohistochemistry. Metabolic changes were assessed by glucose uptake, lactate production, glutathione levels, and oxygen consumption rate. Results We show here that HNSCC cells display strong addiction to glutamine. CPI-613, a novel lipoate analog, redirects cellular activity towards tumor-promoting glutaminolysis, leading to low anticancer efficacy in HNSCC cells. Mechanistically, CPI-613 inhibits the tricarboxylic acid cycle by blocking the enzyme activities of pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, which upregulates GLS1 and eventually promotes the compensatory role of glutaminolysis in cancer cell survival. Most importantly, the addition of a GLS1 inhibitor CB-839 to CPI-613 treatment abrogates the metabolic dependency of HNSCC cells on glutamine, achieving a synergistic anticancer effect in glutamine-addicted HNSCC. Conclusions These findings uncover the critical role of GLS1-mediated glutaminolysis in CPI-613 treatment and suggest that the CB-839 and CPI-613 combination may potentiate synergistic anticancer activity for HNSCC therapeutic gain.

Evidence for a novel, effective approach to targeting carcinoma catabolism exploiting the first-in-class, anti-cancer mitochondrial drug, CPI-613

“…For example, the addition of the clinically well-tolerated glutaminase inhibitor, CB839 (to preempt GDH ETC electron flow) [ 36 ], to a CPI-613 cocktail may prove effective in some cases or tumor types. Newly published in vivo results from others [ 45 ] (below) strongly support this prediction. Further, the tumor selectivity of CPI-613 may be sufficient to make CB839-containing cocktails clinically workable.…”

“…With this series of results in hand, we can productively return to the issue of the concentrations of free monomeric glucose available to xenograft solid tumors (and, thus, likely in the clinical context). Our CPI-613 combination PDAC xenograft results in Figs 6 and 7D and those in clear cell sarcoma [ 18 ] and HNSCC carcinoma [ 45 ] discussed above all show potent TGI without direct targeting of glycolysis. These results collectively indicate that none of these tumors has adequate access to free glucose in vivo to engender glycolysis-dependent rescue from CPI-613.…”

“…During the drafting of this manuscript, the Teng group published two related papers on CPI-613 interaction with cancer metabolism [ 45 , 49 ]. In contrast to the work herein, these authors’ in vitro studies were done in replete conventional media, requiring high drug doses (150–250μM) and prolonged drug exposure (72 hours) to observe robust CPI-613 cell death effects, consistent with our original studies [ 11 , 12 ].…”

“…Second and more importantly, Lang, et al [ 45 ] show that targeting GLN metabolism with the CB839 glutaminase inhibitor under nutrient depleted in vivo conditions strongly sensitizes head and neck squamous cell carcinoma (HNSCC) xenografts to CPI-613. This is in conspicuous contrast to the modest effects of such treatments these authors observe in vitro in nutrient-replete media.…”

α-Ketoglutarate-Mediated DNA Demethylation Sustains T-Acute Lymphoblastic Leukemia upon TCA Cycle Targeting

“…CPI-613, which targets mitochondrial KGDHC and pyruvate dehydrogenase, is an example of the TCA cycle inhibitors currently in clinical trials for treatment of a broad spectrum of cancers, including acute myelogenous leukemia (AML) and pancreatic adenocarcinoma (NCT03374852; NCT01520805; and NCT03504410) [ 29 , 30 ]. However, it has not shown strong efficacy for these cancers as a single agent, possibly due to metabolic rewiring of malignant cells upon treatment [ 31 , 32 ]. Understanding how malignant cells escape pharmacological inhibition of the TCA cycle can facilitate the rational selection of combination therapy for CPI-613 and other TCA cycle inhibitors.…”