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Regulation of myeloid function by LC3-associated phagocytosis promotes tumor immune tolerance

ABSTRACT: Targeting autophagy in cancer cells and in the tumor microenvironment are current goals of cancer therapy. However, components of canonical autophagy play roles in other biological processes, adding complexity to this goal. One such alternative function of autophagy proteins is LC3-associated phagocytosis (LAP), which functions in phagosome maturation and subsequent signaling events. Here we show that impairment of LAP in the myeloid compartment, rather than canonical autophagy, induces control of tumor growth by tumor-associated macrophages (TAM) upon phagocytosis of dying tumor cells. Single cell RNAseq analysis revealed that defects in LAP induce pro-inflammatory gene expression and trigger STING-mediated type I interferon responses in TAM. We found that the anti-tumor effects of LAP impairment require tumor-infiltrating T cells, dependent upon the STING and the type I interferon response. Therefore, autophagy proteins in the myeloid cells of the tumor microenvironment contribute to immune suppression of T lymphocytes by effecting LAP.

ORGANISM(S): Mus musculus

PROVIDER: GSE118019 | GEO | 2018/09/15

REPOSITORIES: GEO

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Project description:Autophagy degrades and recycles intracellular components to sustain metabolism and survival during starvation. Tumor cells upregulate and require autophagy to support their metabolism and enhance their proliferation and malignancy, and host autophagy also promotes tumor growth by providing essential tumor nutrients such as arginine in the circulation or alanine in the local tumor microenvironment. In addition to its metabolic role, autophagy regulates immune cell homeostasis and function, and suppresses inflammation, which may also play a role in cancer. Although host autophagy does not promote a T cell anti-tumor immune response in tumors with low tumor mutational burden (TMB), whether this was the case in tumors with high TMB was not known. Here we show that in contrast to low TMB tumors, host-specific deletion of the essential autophagy gene Atg7 induces a pro-inflammatory cytokine response and limits the growth of high TMB tumors, which is rescued by T-cell depletion. Expression of immune-related genes is increased in tumors from Atg7Δ/Δ hosts in a T-cell dependent manner. Tumors from Atg7Δ/Δ hosts also have decreased T regulatory cells (Tregs), and depletion of Tregs phenocopies the reduced tumor growth observed in Atg7Δ/Δ hosts. Moreover, loss of Stimulator of interferon genes (Sting) or IFNg restores growth of high TMB tumors on Atg7Δ/Δ hosts. Finally, similar to whole-body loss of autophagy, specific loss of autophagy in the liver is sufficient to limit tumor growth. Thus, autophagy, especially in the liver, promotes tumor immune tolerance by limiting STING, T cells, and IFNg, which enables tumor growth. We have designated this: Hepatic Autophagy Immune Tolerance (HAIT). Autophagy thereby promotes tumor growth through both metabolic and immune mechanisms depending on mutational load, and autophagy inhibition is an effective means to promote an anti-tumor T-cell response in high TMB tumors. Genomic DNA Profiling using Agilent SureSelect Mouse All Exon kit and sequencing using Illumina NextSeq550

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Regulation of myeloid function by LC3-associated phagocytosis promotes tumor immune tolerance

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