Abstract | OBJECTIVE: DESIGN: The effects of L. gallinarum in anti-PD1 response were assessed in syngeneic mouse models and azoxymethane/ dextran sulfate sodium-induced CRC model. The change of immune landscape was identified by multicolour flow cytometry and validated by immunohistochemistry staining and in vitro functional assays. Liquid chromatography-mass spectrometry was performed to identify the functional metabolites. RESULTS: L. gallinarum significantly improved anti-PD1 efficacy in two syngeneic mouse models with different microsatellite instability (MSI) statuses (MSI-high for MC38, MSI-low for CT26). Such effect was confirmed in CRC tumourigenesis model. L. gallinarum synergised with anti-PD1 therapy by reducing Foxp3+ CD25+ regulatory T cell (Treg) intratumoural infiltration, and enhancing effector function of CD8+ T cells. L. gallinarum-derived indole-3-carboxylic acid (ICA) was identified as the functional metabolite. Mechanistically, ICA inhibited indoleamine 2,3-dioxygenase (IDO1) expression, therefore suppressing kynurenine (Kyn) production in tumours. ICA also competed with Kyn for binding site on aryl hydrocarbon receptor (AHR) and antagonised Kyn binding on CD4+ T cells, thereby inhibiting Treg differentiation in vitro. ICA phenocopied L. gallinarum effect and significantly improved anti-PD1 efficacy in vivo, which could be reversed by Kyn supplementation. CONCLUSION: L. gallinarum-derived ICA improved anti-PD1 efficacy in CRC through suppressing CD4+Treg differentiation and enhancing CD8+T cell function by modulating the IDO1/Kyn/AHR axis. L. gallinarum is a potential adjuvant to augment anti-PD1 efficacy against CRC.
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Authors | Winnie Fong, Qing Li, Fenfen Ji, Wei Liang, Harry Cheuk Hay Lau, Xing Kang, Weixin Liu, Kenneth Kin-Wah To, Zhong Zuo, Xiaoxing Li, Xiang Zhang, Joseph Jy Sung, Jun Yu |
Journal | Gut
(Gut)
Vol. 72
Issue 12
Pg. 2272-2285
(Nov 24 2023)
ISSN: 1468-3288 [Electronic] England |
PMID | 37770127
(Publication Type: Journal Article)
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Copyright | © Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ. |
Chemical References |
- Kynurenine
- Receptors, Aryl Hydrocarbon
- Pdcd1 protein, mouse
- Programmed Cell Death 1 Receptor
- Immune Checkpoint Inhibitors
- IDO1 protein, mouse
- Bacterial Lysates
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Topics |
- Animals
- Mice
- CD8-Positive T-Lymphocytes
- Colorectal Neoplasms
(drug therapy)
- Kynurenine
(metabolism)
- Receptors, Aryl Hydrocarbon
(drug effects, metabolism)
- T-Lymphocytes, Regulatory
- Lactobacillus
(chemistry)
- Programmed Cell Death 1 Receptor
(drug effects, immunology)
- Immune Checkpoint Inhibitors
(pharmacology, therapeutic use)
- Bacterial Lysates
(pharmacology, therapeutic use)
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