Our findings show that mitochondrial dysfunction is sensed through the OMA1-DELE1-HRI-eIF2α cascade, which limits cancer cell proliferation (Fig. 5d, g), and that cell lines reliant on OXPHOS for energy production, or those with minimal reserve mitochondrial capacity, are more sensitive to GC7 (Supplementary Figs. 4a, S11a–d). The gene discussed is OMA1; the disease is cancer.