Chuong, C. L. | bioRxiv Science

bioRxiv2025

Sialylated CD43 is a glyco-immune checkpoint for macrophage phagocytosis

Macrophages in the tumor microenvironment exert potent anti-tumorigenic activity through phagocytosis. Yet therapeutics that enhance macrophage phagocytosis have not improved outcomes in clinical trials for patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). To systematically identify regulators of phagocytosis, we performed genome-scale CRISPR knockout screens in human leukemia cells co-cultured with human monocyte-derived macrophages. Surprisingly, we found that whereas the classic "dont eat me" signal CD47 inhibited mouse macrophages, it did not inhibit phagocytosis by human macrophages. In contrast, the O-linked glycosylation and sialylation pathways were strong negative regulators of phagocytosis. In AML, the cell surface O-linked glycoprotein CD43 was the major effector of the O-linked glycosylation and sialylation pathways. Genetic deletion or antibody blockade of CD43 enhanced macrophage phagocytosis. This work highlights the importance of using human platforms to identify immune checkpoints, and nominates CD43 as a glyco-immune regulator of human macrophage phagocytosis.

cancer biology↗

bioRxiv2025

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.

cancer biology↗