In vivo CRISPR screens identify the E3 ligase Cop1 as a modulator of macrophage infiltration and cancer immunotherapy target

Cell. 2021 Oct 14;184(21):5357-5374.e22. doi: 10.1016/j.cell.2021.09.006. Epub 2021 Sep 27.

Abstract

Despite remarkable clinical efficacy of immune checkpoint blockade (ICB) in cancer treatment, ICB benefits for triple-negative breast cancer (TNBC) remain limited. Through pooled in vivo CRISPR knockout (KO) screens in syngeneic TNBC mouse models, we found that deletion of the E3 ubiquitin ligase Cop1 in cancer cells decreases secretion of macrophage-associated chemokines, reduces tumor macrophage infiltration, enhances anti-tumor immunity, and strengthens ICB response. Transcriptomics, epigenomics, and proteomics analyses revealed that Cop1 functions through proteasomal degradation of the C/ebpδ protein. The Cop1 substrate Trib2 functions as a scaffold linking Cop1 and C/ebpδ, which leads to polyubiquitination of C/ebpδ. In addition, deletion of the E3 ubiquitin ligase Cop1 in cancer cells stabilizes C/ebpδ to suppress expression of macrophage chemoattractant genes. Our integrated approach implicates Cop1 as a target for improving cancer immunotherapy efficacy in TNBC by regulating chemokine secretion and macrophage infiltration in the tumor microenvironment.

Keywords: C/ebpδ; CRISPR screening; Cop1; E3 ubiquitin ligase; immunotherapy; triple-negative breast cancer.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CCAAT-Enhancer-Binding Protein-delta / metabolism
  • CRISPR-Associated Protein 9 / metabolism
  • Cell Line, Tumor
  • Chemokines / metabolism
  • Chemotaxis
  • Clustered Regularly Interspaced Short Palindromic Repeats / genetics*
  • Disease Models, Animal
  • Gene Library
  • Humans
  • Immune Evasion
  • Immunotherapy*
  • Macrophages / enzymology*
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Neoplasms / immunology*
  • Neoplasms / therapy*
  • Nuclear Proteins / metabolism*
  • Proteolysis
  • Substrate Specificity
  • Triple Negative Breast Neoplasms / immunology
  • Triple Negative Breast Neoplasms / therapy
  • Ubiquitin-Protein Ligases / metabolism*

Substances

  • Chemokines
  • Nuclear Proteins
  • CCAAT-Enhancer-Binding Protein-delta
  • COP1 protein, mouse
  • Ubiquitin-Protein Ligases
  • CRISPR-Associated Protein 9