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Reduced Leucine Availability Inhibits the Growth of Bone Sarcomas by Stimulating the Fuel Sensing Enzyme AMPK
Author(s) -
Martin Shailer,
Boyer Michael,
Ananieva Elitsa
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.300.4
Subject(s) - leucine , mtorc1 , ampk , protein kinase a , cell growth , amino acid , chemistry , amp activated protein kinase , protein degradation , intracellular , biochemistry , enzyme , cancer research , microbiology and biotechnology , biology , phosphorylation , protein kinase b
Bone sarcomas are tumors that commonly originate from the bone and the cartilage. Although rare, bone sarcomas are associated with high mortality in children and adolescents due to their unresponsiveness to traditional treatments. One novel approach to address this resistance is to explore the role of leucine metabolism in bone sarcoma cellular proliferation and protein synthesis. The essential amino acid, leucine, stimulates protein synthesis via complex 1 of the mammalian target of rapamycin (mTORC1) and is thus important for cell growth and proliferation. The intracellular concentrations of leucine are regulated at the level of leucine degradation. The first step in leucine degradation is the reversible transamination of leucine catalyzed by the mitochondrial (BCATm) and the cytosolic (BCATc) branched chain aminotransferases. The objective of this research was to explore whether changes in leucine availability enforced by inhibition of leucine uptake or leucine degradation would impact the growth and protein synthesis of the human bone sarcoma cell line 143B. We hypothesized that the leucine antagonist, N‐acetyl‐leucine‐amide (NALA), would inhibit the cellular growth and protein synthesis of the bone sarcoma cells, while the BCATc inhibitor, gabapentin, would have an effect opposite to that of NALA, through the inhibition of leucine degradation. To test this hypothesis, we treated 143B cells with different concentrations of NALA (0,12.5, 25, and 50mM) or gabapentin (0, 5, and 50mM) for twenty‐four hours, and measured the following: cellular growth, protein content, and the activation of mTORC1 and the fuel‐sensing enzyme AMP‐activated protein kinase (AMPK). Our results revealed that both NALA and gabapentin inhibited the bone sarcoma cellular growth and protein content in concentration dependent manner. However, while NALA stimulated AMPK, gabapentin inhibited AMPK, as evidenced by changes in the phosphorylation of AMPK. The observed changes in AMPK indicate that leucine may impact the energy status and the growth of bone sarcomas by modulating the activation state of AMPK. Because activation of AMPK inhibits anabolic processes and cancer growth, a therapeutic approach aimed at reducing leucine availability may be one novel solution to treat bone cancer patients. Support or Funding Information IOER ‐startup, Des Moines University (Ananieva, EA)