Aspirin Modulation of the Colorectal Cancer-Associated Microbe Fusobacterium nucleatum

Abstract

Aspirin is a chemopreventive agent for colorectal adenoma and cancer (CRC) that, like many drugs inclusive of chemotherapeutics, has been investigated for its effects on bacterial growth and virulence gene expression. Given the evolving recognition of the roles for bacteria in CRC, in this work, we investigate the effects of aspirin with a focus on one oncomicrobe—Fusobacterium nucleatum. We show that aspirin and its primary metabolite salicylic acid alter F. nucleatum strain Fn7-1 growth in culture and that aspirin can effectively kill both actively growing and stationary Fn7-1. We also demonstrate that, at levels that do not inhibit growth, aspirin influences Fn7-1 gene expression. To assess whether aspirin modulation of F. nucleatum may be relevant in vivo, we use the ApcMin/+ mouse intestinal tumor model in which Fn7-1 is orally inoculated daily to reveal that aspirin-supplemented chow is sufficient to inhibit F. nucleatum-potentiated colonic tumorigenesis. We expand our characterization of aspirin sensitivity across other F. nucleatum strains, including those isolated from human CRC tissues, as well as other CRC-associated microbes, enterotoxigenic Bacteroides fragilis, and colibactin-producing Escherichia coli. Finally, we determine that individuals who use aspirin daily have lower fusobacterial abundance in colon adenoma tissues, as determined by quantitative PCR performed on adenoma DNA. Together, our data support that aspirin has direct antibiotic activity against F. nucleatum strains and suggest that consideration of the potential effects of aspirin on the microbiome holds promise in optimizing risk-benefit assessments for use of aspirin in CRC prevention and management. IMPORTANCE There is an increasing understanding of the clinical correlations and potential mechanistic roles of specific members of the gut and tumoral microbiota in colorectal cancer (CRC) initiation, progression, and survival. However, we have yet to parlay this knowledge into better CRC outcomes through microbially informed diagnostic, preventive, or therapeutic approaches. Here, we demonstrate that aspirin, an established CRC chemopreventive, exhibits specific effects on the CRC-associated Fusobacterium nucleatum in culture, an animal model of intestinal tumorigenesis, and in human colonic adenoma tissues. Our work proposes a potential role for aspirin in influencing CRC-associated bacteria to prevent colorectal adenomas and cancer, beyond aspirin’s canonical anti-inflammatory role targeting host tissues. Future research, such as studies investigating the effects of aspirin on fusobacterial load in patients, will help further elucidate the prospect of using aspirin to modulate F. nucleatum in vivo for improving CRC outcomes.

Oral microbiota in human systematic diseases

“… 47 Moreover, the F. nucleatum isolated from the inflammatory intestinal epithelium of patients with IBD is more invasive than the strain isolated from healthy people or healthy intestinal epithelium of patients with IBD. 48 – 50 In addition, Klebsiella pneumoniae from the oral cavity can enter the intestinal tract ectopically, causing an increase in Th1 cells in the intestinal mucosa, thereby inducing IBD. 51 , 52 Clinical studies have also found that more oral-derived microorganisms can be detected in the intestinal mucosa and feces of patients with IBD.…”

Modulation of the Host Cell Transcriptome and Epigenome by Fusobacterium nucleatum

“…PTGS2 ( COX2 ) upregulation is associated with F. nucleatum abundance in colon tumors ( 24 ). Additionally, aspirin, a modulator of PTGS2 , has long been recognized for its chemopreventive effect in the setting of colorectal cancers ( 76 ) and was recently demonstrated to reduce the development of colonic adenomas after F. nucleatum inoculation in the Apc min /+ mouse model ( 77 ). In our data, PTGS2 is among the most strongly differentially expressed genes in HCAE cells but is not differentially expressed in HCE cells, suggesting that the upregulation of PTGS2 and aspirin inhibition may be particularly important in some host cell or tissue contexts.…”

Modulation of the host cell transcriptome and epigenome by Fusobacterium nucleatum

“…PTGS2 (COX2) upregulation is associated with Fn abundance in colon tumors (Kostic et al, 2013). Additionally, aspirin, a modulator of PTGS2, has been recently demonstrated to reduce development of colonic adenomas after Fn inoculation in the Apc min/+ mouse model (Brennan et al, 2021). In our data, PTGS2 is among the most strongly differentially expressed genes in invaded HCAE cells, but is not differentially expressed in HCE cells, suggesting that upregulation of PTGS2 and aspirin inhibition may be particularly important for invasive Fn strains.…”