eIF5B drives integrated stress response-dependent translation of PD-L1 in lung cancer

Cancer cells express high levels of programmed death ligand 1 (PD-L1), a ligand of the programmed cell death protein 1 (PD-1) receptor on T cells, allowing tumors to suppress T cell activity. Clinical trials utilizing antibodies that disrupt the PD-1/PD-L1 checkpoint have yielded remarkable results, with anti-PD-1 immunotherapy approved as a first-line therapy for patients with lung cancer. We used CRISPR-based screening to identify regulators of PD-L1 in human lung cancer cells, revealing potent induction of PD-L1 upon disruption of heme biosynthesis. Impairment of heme production activates the integrated stress response, allowing bypass of inhibitory upstream open reading frames in the PD-L1 5′ untranslated region, resulting in enhanced PD-L1 translation and suppression of anti-tumor immunity. We demonstrate that integrated stress-response-dependent PD-L1 translation requires the translation initiation factor eIF5B. eIF5B overexpression, which is frequent in lung adenocarcinomas and associated with poor prognosis, is sufficient to induce PD-L1. These findings illuminate mechanisms of immune checkpoint activation and identify targets for therapeutic intervention. O'Donnell and colleagues report that activation of the integrated stress response in non-small cell lung cancer cells by impairing heme production leads to enhanced PD-L1 translation in an eIF5B-dependent manner.