<scp>ATF4</scp> ‐mediated stress response as a therapeutic vulnerability in chordoma

Chordoma, a rare primary bone malignancy, currently lacks effective targeted therapies. Despite surgical resection and adjuvant radiotherapy, prognosis remains poor. Recent preclinical studies have highlighted potential therapeutic targets, including the transcription factor T-box transcription factor T (TBXT). However, clinical outcomes associated with therapies targeting TBXT remain underexplored or have been modest, warranting further investigation. In this study, we investigated the therapeutic potential of transfer RNA (tRNA) synthetase inhibitors in chordoma treatment. Focused compound screening identified distinct chemotypes targeting human glutamyl-prolyl-tRNA synthetase (EPRS) as being effective in reducing cell viability in chordoma cell lines through a cyclic AMP-dependent transcription factor (ATF4)-mediated stress response rather than through TBXT regulation. Mechanistically significant upregulation of ATF4 and associated stress response genes was identified with consecutive pro-apoptotic DNA damage-inducible transcript 3 protein (DDIT3)-mediated cell death. The prototypic EPRS inhibitor halofuginone demonstrated significant tumour growth inhibition in an in vivo patient-derived xenograft model. These results suggest that targeting metabolic stress pathways via ATF4 activation presents a novel therapeutic approach for chordoma, warranting further clinical investigation.