Gut Bacteria Could Hold Key to Colorectal Cancer Treatment

GUT bacteria could offer a new approach to colorectal cancer (CRC) treatment by altering cholesterol metabolism within tumours, according to new research identifying a microbial metabolite capable of suppressing cancer growth and overcoming resistance to targeted therapies.

The study found that 4-cholesten-3-one (4-C-3), a metabolite produced through microbial cholesterol metabolism, was depleted in faecal and tumour samples from patients with CRC. Restoring this metabolite inhibited tumour growth in laboratory models, while microbiota-based strategies reduced intratumoral cholesterol and induced tumour regression in preclinical experiments.

Linking Gut Microbiota to Cholesterol Metabolism

Cholesterol accumulation within colorectal tumours has been implicated in cancer progression, making cholesterol metabolism an area of interest for developing new therapeutic strategies.

However, systemic cholesterol-lowering approaches have demonstrated limited benefits in this context and may present safety concerns, highlighting the need for more targeted interventions.

Researchers therefore investigated whether gut microorganisms could be used to modify cholesterol metabolism locally and influence tumour growth.

By screening microbial cholesterol metabolites, the team identified 4-C-3 as a potential anticancer compound.

Analysis of samples from patients with CRC revealed reduced levels of 4-C-3 in both faecal and tumour tissue samples, suggesting that alterations in microbial cholesterol metabolism may be associated with the disease.

The researchers subsequently investigated whether restoring this metabolite could influence colorectal tumour growth.

Cholesterol Metabolite Suppresses Cancer Growth

Laboratory experiments demonstrated that 4-C-3 suppressed tumour growth across several preclinical models, including CRC cell lines, patient-derived organoids, and tumour xenografts.

Further mechanistic investigations revealed that the metabolite interfered with two important oncogenic pathways involved in CRC development and progression.

First, 4-C-3 inhibited activation of the epidermal growth factor receptor (EGFR), a signalling pathway involved in regulating cellular proliferation and survival.

Second, the metabolite stabilised mutant oncogenic KRAS in an inactive state, limiting its ability to drive cancer-associated signalling.

Mutations in KRAS are an established mechanism of resistance to anti-EGFR therapies in CRC, restricting the effectiveness of these treatments in patients whose tumours carry relevant mutations.

By suppressing EGFR activation and interfering with mutant KRAS activity, 4-C-3 overcame KRAS-driven resistance to anti-EGFR treatment in the experimental models.

These findings suggest that microbial cholesterol metabolites may influence tumour growth through mechanisms extending beyond cholesterol regulation alone.

Engineered Gut Bacteria Induce Tumour Regression

To investigate whether 4-C-3 could be restored through microbiota-based interventions, researchers evaluated two approaches designed to increase production of the metabolite within the intestine.

The first involved Oscillibacter ruminantium, a naturally occurring bacterial species capable of producing 4-C-3, which researchers found to be reduced in CRC.

The second used a non-pathogenic strain of Escherichia coli genetically engineered to convert intestinal cholesterol into 4-C-3.

Both approaches successfully restored the metabolite in preclinical models, reducing cholesterol accumulation within tumours and inducing tumour regression.

Importantly, these effects were observed without overt toxicity in the experimental models.

The results provide proof-of-concept evidence that modifying the gut microbiota could influence tumour metabolism and potentially provide a more localised approach to targeting cholesterol-associated cancer pathways.

Implications for Future Colorectal Cancer Treatment

The findings highlight a previously identified link between microbial cholesterol metabolism and CRC progression, suggesting that gut bacteria could be harnessed to influence tumour biology.

Unlike systemic cholesterol-lowering strategies, microbiota-based interventions may offer a way to alter cholesterol metabolism within the intestinal environment while targeting pathways involved in tumour growth.

The ability of 4-C-3 to interfere with mutant KRAS signalling is particularly relevant, given the challenges associated with treating CRC characterised by resistance to anti-EGFR therapies.

However, the therapeutic findings remain preclinical. Although reduced 4-C-3 levels were identified in samples from patients with CRC, tumour suppression and regression were demonstrated in laboratory and animal models rather than clinical trials.

Further research will be required to establish the safety, efficacy, and feasibility of microbiota-based delivery approaches in humans, including whether the observed effects can be reproduced in patients with different molecular subtypes of CRC.

Overall, the study identifies microbial cholesterol metabolism as a potential therapeutic avenue in CRC, providing a foundation for future investigations into microbiome engineering and strategies to overcome treatment resistance.

Reference

Wu, J., Li, L., Lai, Y. et al. Microbiota-based modulation of intratumoral cholesterol metabolism for colorectal cancer treatment. Nat Metab (2026). https://doi.org/10.1038/s42255-026-01655-0