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L-Asparaginase and Inhibitors of Glutamine Synthetase Disclose Glutamine Addiction of β-Catenin-Mutated Human Hepatocellular Carcinoma Cells.
MedLine Citation:
PMID:  21834755     Owner:  NLM     Status:  Publisher    
Selected oncogenic mutations support unregulated growth enhancing glutamine availability but increasing the dependence of tumor cells on the amino acid. Data from literature indicate that a subset of HepatoCellular Carcinomas (HCC) is characterized by mutations of β-catenin and overexpression of Glutamine Synthetase (GS). To assess if this phenotype may constitute an example of glutamine addiction, we treated four human HCC lines with the enzyme L-Asparaginase (ASNase), a glutaminolytic drug. ASNase had a significant antiproliferative effect only in the β-catenin mutated HepG2 cells, which were partially rescued by the anaplerotic intermediates pyruvate and α-ketoglutarate. The enzyme severely depleted cell glutamine, caused eIF2α phosphorylation, inhibited mTOR activity, and increased autophagy in both HepG2 and in the β-catenin wild type cell line Huh-7. When used with ASNase, the GS inhibitor methionine sulfoximine (MSO) emptied cell glutamine pool, arresting proliferation in ASNase-insensitive Huh-7 cells and activating caspase-3 and apoptosis in HepG2 cells. Compared with Huh-7 cells, HepG2 cells accumulated much higher levels of glutamine and MSO, due to the higher expression and activity of SNAT2, a concentrative transporter for neutral amino acids, but were much more sensitive to glutamine withdrawal from the medium. In the presence of ASNase, MSO caused a paradoxical maintenance of rapamycin-sensitive mTOR activity in both HepG2 and Huh-7 cells. β-catenin silencing lowered ASNase sensitivity of HepG2 cells and of Huh-6 cells, another β-catenin-mutated cell line, which also exhibited high sensitivity to ASNase. Thus, β-catenin mutated HCC cells are more sensitive to glutamine depletion and accumulate higher levels of GS inhibitors. These results indicate that glutamine deprivation may constitute a targeted therapy for β-catenin-mutated HCC cells addicted to the amino acid.
Saverio Tardito; Martina Chiu; Jacopo Uggeri; Alessandro Zerbini; Francesco Da Ros; Valeria Dall'asta; Gabriele Missale; Ovidio Bussolati
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-8-12
Journal Detail:
Title:  Current cancer drug targets     Volume:  -     ISSN:  1873-5576     ISO Abbreviation:  -     Publication Date:  2011 Aug 
Date Detail:
Created Date:  2011-8-12     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101094211     Medline TA:  Curr Cancer Drug Targets     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Unit of General and Clinical Pathology, Department of Experimental Medicine, Università degli Studi di Parma, Via Volturno 39, Italy.
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