Endogenous protein S100A14 stabilizes glutaminase to render hepatocellular carcinoma resistant to sorafenib

Many cases of advanced hepatocellular carcinoma (HCC) are resistant to the widely used drug sorafenib, which worsens prognosis. While many studies have explored how acquired resistance emerges during drug exposure, the mechanism underlying primary resistance before treatment still remain elusive. Here, we performed single-cell lineage tracing and RNA sequencing to identify sorafenib-resistant lineages in HCC, and demonstrated that high expression of S100A14 was positively associated with primary sorafenib resistance. Knocking down S100A14 rendered xenograft tumors in mice significantly more sensitive to sorafenib. Mechanistic studies indicated that S100A14 binds to glutaminase and blocks its phosphorylation at residues Y308 and S314, which in turn inhibits its ubiquitination and subsequent degradation. This stabilization of glutaminase reduces oxidative stress in HCC cells and thereby antagonizes the ability of sorafenib to induce apoptosis. Inhibiting glutaminase with telaglenastat (CB-839) significantly improved sorafenib efficacy against xenograft tumors in vivo. These results suggest that S100A14 can contribute to primary sorafenib resistance in HCC by stabilizing glutaminase. Thus, analyzing the expression of S100A14 may be useful for predicting primary sorafenib resistance, and inhibiting S100A14 or glutaminase may be effective for preventing or overcoming such resistance.