L-asparaginase and inhibitors of glutamine synthetase disclose glutamine addiction of β-catenin-mutated human hepatocellular carcinoma cells

S. Tardito, M. Chiu, J. Uggeri, A. Zerbini, F. da Ros, V. Dall'Asta, G. Missale, O. Bussolati

Research output: Contribution to journalArticle

Abstract

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 LAsparaginase (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.

Original languageEnglish
Pages (from-to)929-943
Number of pages15
JournalCurrent Cancer Drug Targets
Volume11
Issue number8
DOIs
Publication statusPublished - Oct 2011

Keywords

  • β-catenin
  • Cancer metabolism
  • Glutamine
  • Hepatocellular carcinoma
  • L-asparaginase

ASJC Scopus subject areas

  • Drug Discovery
  • Pharmacology
  • Cancer Research

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