6-pentadecyl salicylic acid reduces cell proliferation in U373MG glioblastoma cells <i>via</i> glutamine uptake impairment

Glioblastoma cells exhibit a pronounced dependence on glutamine uptake, primarily <i>via</i> the alanine‑serine‑cysteine transporter 2, since its deletion prevents glioma growth, making this transporter an attractive therapeutic target. This study aimed to evaluate 6‑pentadecyl salicylic acid, a natural antineoplastic and immunomodulatory compound, for its ability to impair alanine‑serine‑cysteine transporter 2‑mediated glutamine transport and by these means reduce glioblastoma cells viability. Human U373MG glioma cells and primary chick cerebellar Bergmann glia (non‑malignant control) were exposed to increasing concentrations of 6SA for 24 h. Viability, measured by the MTT assay, declined in a dose‑dependent manner in U373MG cells while Bergmann glia remained largely unaffected (<i>p</i> < 0.001). L-[³H]-glutamine uptake assays revealed that 100 µM 6SA functioned as a potent inhibitor, increasing the Michaelis constant (K_M) more than four-fold (from 7.11 mM to 31.79 mM). This indicates a mixed-type or competitive inhibition mechanism that dramatically reduces the transporter's apparent affinity for glutamine and prevents saturation within the tested substrate range. Additionally, quantitative PCR showed a dose‑dependent down‑regulation of ASCT2 mRNA, suggesting post‑transcriptional control. Blind docking of 6SA onto the cryo‑EM ASCT2 structure identified nine peripheral cavities that could serve as allosteric sites, however, these predictions are computational and require experimental validation; binding to these sites would stabilize a low‑affinity transporter conformation, consistent with the kinetic data. Collectively, 6‑pentadecyl salicylic acid selectively impairs glutamine transport and viability in glioblastoma cells while sparing normal glial cells, supporting its potential as a lead compound for alanine‑serine‑cysteine transporter 2 ‑targeted glioma therapy.