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The remarkable clinical benefits in cancer patients receiving immunotherapy have ignited the research enthusiasm on cancer immunotherapy.  However, primary resistance to immune checkpoint blockade (ICB) therapy remains one of the major challenges to effective immunotherapy in many patients. A deeper understanding of tumor-intrinsic mechanisms is therefore essential to identify new therapeutic targets and improve ICB outcomes. This project aimed to uncover novel immune regulatory pathways in cancer cells that could enhance PD-1/PD-L1-targeted therapies.

In Paper I, we performed genome-wide CRISPR/Cas9 screens in a tumor-immune co-culture system, and we identified NEDD8 as a key resistance gene to PD-1 blockade in triple-negative breast cancer (TNBC). NEDD8 deletion in cancer cells increased tumor immunogenicity, enhanced antigen presentation (e.g., HLA-DR), and improved responses to anti-PD-1 and anti-PD-L1 therapy. In immunocompetent mice, Nedd8 loss in tumors enhanced PD-1/PD-L1 efficacy, leading to CD8+ T cell-dependent tumor eradication, prolonged survival, and activation of multiple immune pathways.

In Paper II, integrated scRNA-seq and high-resolution spatial transcriptomics revealed that cancer-cell neddylation regulates immune cell infiltration and function. Nedd8 deletion in cancer cells increased inflammatory myeloid cell infiltration and amplified adaptive responses to PD-1 blockade. High-content drug screening showed that protein neddylation sensitized human breast cancer cells to lipid metabolism inhibitors e.g., statin drugs and ferroptosis inducers. These compounds synergize with PD-1 blockade and protected the mice from tumor rechallenge in vivo.

In Paper III, we identified NEDD8 as a myeloid-intrinsic immune checkpoint that restrains innate immune activation. NEDD8 loss in human monocytic THP-1 cancer cells enhanced pro-inflammatory signaling and revealed mTORC1-dependent vulnerabilities. Statin treatment, which drives pathway changes similar to NEDD8-deficient human cells, amplified strong inflammatory responses in human primary CD14+ monocytes through mTOR signaling, and improved early anti-tumor responses in immunocompetent mice.

Altogether, this work uncovers previously unrecognized mechanisms by which NEDD8 regulates tumor and myeloid immunity, providing new avenues to potentiate innate and adaptive anti-tumor responses and improve cancer immunotherapy outcomes.