CREB5 promotes immunotherapy resistance via tumor-intrinsic collagenmatrix deposition
Treatment with immune checkpoint inhibitors induces remarkable clinical responses in several cancer types. However, most cancer patients fail to respond to immunotherapy, and patients who initially respond often exhibit acquired resistance. Understanding the universe of immune evasion strategies will enable design of more effective immunotherapies. Here, we identify genes that drive immune evasion using genome-scale in vivo CRISPR gain-of-function screens in tumors treated with anti-PD-1 antibodies and found that the transcription factor CREB5 drives immune checkpoint blockade resistance. Using transcriptional profiling and functional studies, we show that CREB5 promotes a mesenchymal-like phenotype in melanoma characterized by upregulation of extracellular matrix genes including collagen and collagen-stabilizing factors. Using engineered tumor models and knockout mice, we found that immunotherapy resistance is functionally mediated by tumor-intrinsic collagen deposition. Collagen is the major ligand for the inhibitory receptor LAIR1, broadly expressed on T cells, B cells, NK cells, and myeloid cells. Deletion of LAIR1 in mice or overexpression of the decoy receptor LAIR2 in tumors abrogated the resistance induced by CREB5 overexpression, demonstrating that collagen-LAIR1 inhibitory signaling drives resistance to immune checkpoint inhibitors. These observations define a transcriptional program that remodels the tumor microenvironment to promote immunotherapy resistance via extracellular matrix deposition and indicates that targeting this pathway may enhance immunotherapy efficacy. One-Sentence Summary: In vivo gain-of-function screening in immunotherapy-treated mice reveals a transcription factor, Creb5, that drives the mesenchymal state in melanoma and facilitates immune escape by promoting tumor-intrinsic collagen matrix deposition.