Abstract 2354: Downregulating the glutamine transporter, SLC1A5, significantly reduces cachexia in a PDAC xenograft
Authors: Krishnamachary Balaji , Sivakumar Ishwarya , Mironchik Yelena , Sharma Raj Kumar , Bharti Santosh Kumar , Penet Marie-France , Winnard Paul , Wildes Flonne , Goggins Eibhlin , Maitra Anirban , Goggins Michael G. , Bhujwalla Zaver M. 
Published: July 2021

Abstract
Cachexia occurs with high frequency and severity in pancreatic ductal adenocarcinoma (PDAC) patients [1]. Cachectic patients experience a wide range of symptoms affecting the function of organs such as muscle, liver, brain, and heart, causing significant morbidity [2]. In high-resolution 1H magnetic resonance spectroscopy (MRS) studies of extracts, we previously observed significant perturbation of glutamine in the brain and plasma of mice with a cachexia-inducing PDAC xenograft [3] that prompted us to evaluate the effects of modifying tumor glutamine metabolism on cachexia. We investigated tumors derived from cachexia-inducing Pa04C cells engineered to express shRNA against the glutamine transporter, SLC1A5, glutaminase (GLS) 1, and GLS 2. Patient-derived cachexia-inducing Pa04C cells were stably transduced with virions that expressed shRNA against GLS1 or GLS2 or SLC1A5. Pooled clones were obtained with puromycin selection. Empty vector (EV) cells were also established. Downregulation of target genes was confirmed with mRNA and protein expression characterization. The effects of gene knockdown on tumor growth and weight-loss were determined following subcutaneous inoculation of engineered cells or wild type cells in SCID mice. Longitudinal tumor growth, weights and percent weight changes were determined in 7 wild type (WT), 7 EV, 9 GLS1 downregulated, 9 GLS2 downregulated, and 9 SLC1A5 downregulated tumor bearing mice. Once tumors were ~500 mm3 in volume, tumors were harvested from euthanized mice, and snap frozen for molecular analysis. Protein and mRNA obtained from tumors was validated for downregulation of target genes. Efficient downregulation of SLC1A5, GLS1 and GLS2 mRNA and protein was confirmed in tumors. Downregulating SLC1A5 significantly reduced tumor growth. But, downregulating GLS1 or GLS2 did not reduce tumor growth and, in fact, GLS1 downregulated tumors grew significantly faster than WT or EV tumors. Importantly, for comparable tumor volumes, we found that body weight loss was markedly reduced in mice with SLC1A5 downregulated tumors. Although GLS1 downregulated tumors grew faster than WT tumors, weight loss was attenuated at comparable tumor volumes in these tumors although not to the same extent as in SLC1A5 downregulated tumors. These data highlight potential role of SLC1A5 in PDAC tumor treatment and in the treatment of PDAC-induced cachexia, and support targeting the glutamine/glutamate axis in PDAC to reduce or reverse cachexia.Supported by NIH R35 CA209960 and R01 CA193365. 1. Fearon KC, Baracos VE. Cachexia in pancreatic cancer: new treatment options and measures of success. 2010; 2. Inui A. Cancer anorexia-cachexia syndrome: current issues in research and management. CA Cancer J Clin. 2002; 3. Winnard PT, Jr., et al., Brain metabolites in cholinergic and glutamatergic pathways are altered by pancreatic cancer cachexia. J Cachexia Sarcopenia Muscle. 2020.
Citation Format: Balaji Krishnamachary, Ishwarya Sivakumar, Yelena Mironchik, Raj Kumar Sharma, Santosh Kumar Bharti, Marie-France Penet, Paul Winnard, Flonne Wildes, Eibhlin Goggins, Anirban Maitra, Michael G. Goggins, Zaver M. Bhujwalla. Downregulating the glutamine transporter, SLC1A5, significantly reduces cachexia in a PDAC xenograft [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2354.