Abstract 2669: Glutaminase alternative splicing controls tumor growth and metabolism

Abstract

Abstract Cancer cells reprogram their metabolism to meet their energetic and biosynthetic needs, with many cancer cells showing increased aerobic glycolysis and glutamine consumption. In addition to providing carbon to the TCA cycle to compensate for the diversion of glucose to lactate, glutamine is an important carbon and nitrogen donor for the synthesis of nucleotides, amino sugars and non-essential amino acids. Glutaminase (GLS) catalyzes the first step of glutamine metabolism, the hydrolysis of glutamine to glutamate, which can then be converted to alpha-ketoglutarate, glutathione or non-essential amino acids. GLS is alternatively spliced to make the KGA or more catalytically active GAC isoforms. Analysis of publicly available TCGA RNA-seq data from primary human tumors shows that GAC is the predominant splice form of GLS in many tumor types. However, the roles played by GAC versus KGA in tumor metabolism and progression are poorly understood. To facilitate the study of GLS alternative splicing, CRISPR/Cas9 mediated deletion of the GAC specific exon was used to convert predominantly GAC-expressing parental cell lines to solely KGA-expressing cell lines (ΔGAC). Despite showing decreased glutamine-derived glutamate and α-ketoglutarate, ΔGAC cells do not show impaired growth in nutrient-replete in vitro conditions compared to parental cells. 13C-isotopic labeling and metabolomics showed that ΔGAC cells have decreased levels of proline and alanine, both of which can be derived from glutamine-derived glutamate. This led us to ask if ΔGAC cells are dependent on exogenous non-essential amino acids. We found that depletion of non-essential amino acids slowed the growth of ΔGAC cells compared with parental cells, rescuable by exogenous proline and alanine. Importantly, the growth of lung (A549) and breast cancer (MDA-MB231) ΔGAC xenograft models was diminished compared with parental tumor xenografts in vivo, which is consistent with a role for GAC in nutrient challenged conditions. In summary, the GAC form of glutaminase fuels tumor growth partly through synthesis of non-essential amino acids, particularly under nutrient limiting conditions. As GLS inhibitors enter the clinic, a more thorough understanding of the role of GLS in tumor metabolism will aid in the development of treatment strategies to best make use of these drugs. Citation Format: Zachary Stine, Zandra E. Walton, Lin Zhang, Teresa MW Fan, Andrew N. Lane, Chi V. Dang. Glutaminase alternative splicing controls tumor growth and metabolism. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2669.