Lactobacillus gallinarum modulates the gut microbiota and produces anti-cancer metabolites to protect against colorectal tumourigenesis

Naoki Sugimura; Qing Li; Eagle Siu Hong Chu; Harry Cheuk Hay Lau; Winnie Fong; Weixin Liu; Cong Liang; Geicho Nakatsu; Anthony Chin Yang Su; Olabisi Oluwabukola Coker; William Ka Kei Wu; Francis Ka Leung Chan; Jun Yu

doi:10.1136/gutjnl-2020-323951

Lactobacillus gallinarum modulates the gut microbiota and produces anti-cancer metabolites to protect against colorectal tumourigenesis

Gut. 2021 Dec 22;71(10):2011-2021. doi: 10.1136/gutjnl-2020-323951. Online ahead of print.

Authors

Affiliations

¹ Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK-Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China.
² Department of Gastroenterology, Osaka City University Graduate School of Medicine, Osaka, Japan.
³ Department of Anaesthesia and Intensive Care and Peter Hung Pain Research Institute, The Chinese University of Hong Kong, Hong Kong, China.
⁴ Institute of Precision Medicine, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.
⁵ Department of Immunology and Infectious Diseases/Genetics and Complex Disease, Harvard T. H. Chan School of Public Health, Boston, Massachusetts, USA.
⁶ Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK-Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China junyu@cuhk.edu.hk fklchan@cuhk.edu.hk.

Abstract

Objective: Using faecal shotgun metagenomic sequencing, we identified the depletion of Lactobacillus gallinarum in patients with colorectal cancer (CRC). We aimed to determine the potential antitumourigenic role of L. gallinarum in colorectal tumourigenesis.

Design: The tumor-suppressive effect of L. gallinarum was assessed in murine models of CRC. CRC cell lines and organoids derived from patients with CRC were cultured with L. gallinarum or Escherichia coli MG1655 culture-supernatant to evaluate cell proliferation, apoptosis and cell cycle distribution. Gut microbiota was assessed by 16S ribosomal DNA sequencing. Antitumour molecule produced from L. gallinarum was identified by liquid chromatography mass spectrometry (LC-MS/MS) and targeted mass spectrometry.

Results: L. gallinarum significantly reduced intestinal tumour number and size compared with E. coli MG1655 and phosphate-buffered saline in both male and female murine intestinal tumourigenesis models. Faecal microbial profiling revealed enrichment of probiotics and depletion of pathogenic bacteria in L. gallinarum-treated mice. Culturing CRC cells with L. gallinarum culture-supernatant (5%, 10% and 20%) concentration-dependently suppressed cell proliferation and colony formation. L. gallinarum culture-supernatant significantly promoted apoptosis in CRC cells and patient-derived CRC organoids, but not in normal colon epithelial cells. Only L. gallinarum culture-supernatant with fraction size <3 kDa suppressed proliferation in CRC cells. Using LC-MS/MS, enrichments of indole-3-lactic acid (ILA) was identified in both L. gallinarum culture-supernatant and the gut of L. gallinarum-treated mice. ILA displayed anti-CRC growth in vitro and inhibited intestinal tumourigenesis in vivo.

Conclusion: L. gallinarum protects against intestinal tumourigenesis by producing protective metabolites that can promote apoptosis of CRC cells.

Keywords: colorectal cancer; probiotics.