Abdullah M, Lee SJ. Extracellular Concentration of L-Cystine Determines the Sensitivity to System x
c - Inhibitors.
Biomol Ther (Seoul) 2021;
30:184-190. [PMID:
34667132 PMCID:
PMC8902454 DOI:
10.4062/biomolther.2021.105]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 09/10/2021] [Accepted: 09/16/2021] [Indexed: 11/13/2022] Open
Abstract
Targeting the cystine/glutamate exchange transporter, system xc-, is a promising anticancer strategy that induces ferroptosis, which is a distinct form of cell death mediated by iron-dependent lipid peroxidation. The concentration of L-cystine in culture medium is higher than the physiological level. This study was aimed to evaluate the effects of L-cystine concentration on the efficacy of ferroptosis inducers in hepatocellular carcinoma cells. This study showed that treatment with sulfasalazine or erastin, a system xc- inhibitor, decreased the viability of Huh6 and Huh7 cells in a dose-dependent manner, and the degree of growth inhibition was greater in medium containing a physiological L-cystine concentration of 83 µM than in commercial medium with a concentration of 200 µM L-cystine. However, RSL3, a glutathione peroxidase 4 inhibitor, decreased cell viability to a similar extent in media containing both L-cystine concentrations. Sulfasalazine and erastin significantly increased the percentages of propidium iodide-positive cells in media with 83 µM L-cystine, but not in media with 200 µM L-cystine. Sulfasalazine- or erastin-induced accumulation of lipid peroxidation as monitored by C11-BODIPY probe was higher in media with 83 µM L-cystine than in media with 200 µM L-cystine. In contrast, the changes in the percentages of propidium iodide-positive cells and lipid peroxidation by RSL3 were similar in both media. These results showed that sulfasalazine and erastin, but not RSL3, were efficacious under conditions of physiological L-cystine concentration, suggesting that medium conditions would be crucial for the design of a bioassay for system xc- inhibitors.
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