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Immune sensing of microbial metabolites: Action at the tumor

Timothy L Frankel1, Marina Pasca di Magliano2

  • 1Department of Surgery, University of Michigan, Ann Arbor, 1500 E. Medical Center Drive, Ann Arbor, MI 48109, USA; Rogel Cancer Center, University of Michigan, Ann Arbor, 1500 E. Medical Center Drive, Ann Arbor, MI 48109, USA.

Immunity
|February 9, 2022
PubMed

Insights

Gut microbes transform dietary tryptophan into metabolites that activate the aryl hydrocarbon receptor in myeloid cells. This promotes an immune-suppressive tumor environment, accelerating pancreatic cancer growth.

Area of Science:

  • Microbiome research
  • Immunology
  • Cancer biology

Background:

  • The gut microbiome plays a critical role in cancer development and response to immunotherapy.
  • Dietary components can be metabolized by gut bacteria, influencing host immunity and disease progression.

Purpose of the Study:

  • To investigate how gut microbiota-derived metabolites influence the tumor microenvironment.
  • To understand the mechanisms by which dietary tryptophan metabolism impacts pancreatic ductal adenocarcinoma (PDAC) growth.

Main Methods:

  • Analysis of gut microbiota composition and function.
  • Metabolomic profiling of tryptophan derivatives.
  • Investigating aryl hydrocarbon receptor (AhR) activation in myeloid cells.
  • Assessing the impact on tumor growth in preclinical models.

Main Results:

  • Gut microbiota metabolize dietary tryptophan into specific compounds.
  • These metabolites activate the aryl hydrocarbon receptor (AhR) signaling pathway in myeloid cells within the tumor microenvironment.
  • AhR activation in myeloid cells leads to an immunosuppressive environment.
  • This immunosuppression promotes the growth of pancreatic ductal adenocarcinoma (PDAC).

Conclusions:

  • Microbial metabolism of dietary tryptophan is a key factor in shaping the tumor immune microenvironment.
  • Activation of myeloid cell AhR by these metabolites creates an immunosuppressive state that favors PDAC progression.
  • Targeting microbial tryptophan metabolism or AhR signaling may offer novel therapeutic strategies for pancreatic cancer.

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