Glutaminolysis inhibition as a therapeutic strategy in glutamine-addicted kras mutant colorectal cancer
Refereed conference paper presented and published in conference proceedings

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AbstractIntroduction: Colorectal cancer (CRC) with KRAS mutations represents an unmet clinical need due to the lack of effective therapies. A defining characteristic of oncogenic KRAS-driven cancers is an altered cellular metabolism, in which glucose and glutamine metabolism are extensively rewired satisfy their anabolic needs. In this study, we investigated the metabolic dependencies of KRAS mutant CRC, established the role of glutaminolysis in KRAS-mutant CRC growth and evaluated the synergism between glutaminolysis inhibition and chemotherapy in this subset of CRC. Aims & Methods: Metabolic dependencies of KRAS mutant CRC cell lines were assessed by colony formation and apoptosis assays. Glutamine metabolism in KRAS mutant CRC cells were traced using stable U13C5-glutamine labeling and Ultra-high Performance Liquid Chromatography-Mass Spectrometry (UPLC-MS). Role of glutaminase (GLS1) and the mitochondrial glutamate transporter (SLC25A22) in mediating glutaminolysis was evaluated. Finally, the functional effect of glutaminolysis inhibition (via GLS1 or SLC25A22 blockade) and its synergy with chemotherapeutic agents were tested. Results: Deprivation of glucose, glutamine or their combination in six KRAS mutant CRC (DLD1, HCT116, LOVO, SW480, SW620 and SW1116) and four KRAS wild type CRC cell lines (CACO-2, COLO205, HT29 and SW48) revealed that KRAS mutant CRC cells were profoundly sensitive to glutamine depletion as compared with KRAS wild type CRC cells; whilst exhibiting resistance to glucose depletion. This indicates that supply of glutamine is obligatory for KRAS mutant CRC survival. U13C5-glutamine labeling in DLD1 cells and UPLC-MS revealed that a majority of glutamine was metabolized into glutamate, aspartate and the intermediates of the tricarboxylic acid (TCA) cycle, indicating that glutamine-derived carbons were channeled to the mitochondria for the replenishment of TCA cycle (a process known as glutaminolysis). We further revealed that glutamine was first converted to glutamate by GLS1 at the outer side of inner mitochondrial membrane, which is coupled to SLC25A22 for the import of glutamate into the mitochondrial matrix. Consistent with this model, the silencing of GLS1 or SLC25A22 significantly suppressed cell proliferation in KRAS mutant CRC cells, indicating that their coupled action is indispensable for cell growth. U13C5-glutamine tracing in DLD1 cells with SLC25A22 knockdown showed an attenuated entry of glutamine-derived carbons into the TCA cycle, confirming its involvement in glutaminolysis. Inhibition of SLC25A22-dependent glutaminolysis triggered metabolic stress, suppressed ATP production and promoted oxidative stress. Moreover, a combinatorial approach utilizing SLC25A22- shRNA plus 5-Fluorouracil synergistically suppressed KRAS mutant CRC growth in vitro and in subcutaneous xenograft models. Conclusion: KRAS mutant CRC cells are addicted to glutamine and the blockade of glutaminolysis enzymes GLS1 and SLC25A22 suppressed cell survival. SLC25A22 represents a novel therapeutic target in KRAS mutant CRC and its synergistic effect with chemotherapy warrants further investigation.
All Author(s) ListC.C. Wong, J. Xu, Q. Yun, X. Li, W. Kang, J.J.Y. Sung, Z. Cai, J. Yu.
Name of ConferenceUnited European Gastroenterology (UEG) Week 2016
Start Date of Conference15/10/2016
End Date of Conference19/10/2016
Place of ConferenceVienna
Country/Region of ConferenceAustria
Proceedings TitleUnited European Gastroenterology Journal
Volume Number2
Issue NumberSupple. 1
LanguagesEnglish-United States

Last updated on 2018-18-01 at 08:22