Study analysis · Frontiers in Immunology · 2026
A common bacterium found in liver metastases of colorectal cancer might be fueling the spread of the disease, new research suggests.
Scientists discovered that a bacterium called Bacillus is more abundant in liver tumors that have spread from colon cancer, and it appears to make cancer cells grow and move more in lab tests and mice.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
In simple terms
This study looked at samples from people with colon cancer and liver metastasis, and also did experiments in cells and mice. It found some links between a type of bacteria, certain fats, and immune cells, but it cannot prove that the bacteria cause the cancer to spread. It only shows that these things are found together.
What’s the bottom line?
Scientists studied bacteria inside tumors that have spread from colorectal cancer to the liver. They found that a type of bacteria called Bacillus is more common in liver metastases than in the original colon tumors. This bacterium was linked to higher levels of certain tumor markers and fats. In lab tests, substances from Bacillus made cancer cells move and grow more. In mice, Bacillus made liver tumors grow bigger, and antibiotics reduced this effect. They also found special immune cells called APOE+ macrophages that might be involved.
How strong is this study?
The study used several advanced methods to look at bacteria, chemicals, and cells, which is a strength. However, it only looked at a small number of patients at one time, so we can't be sure the findings apply to everyone, and we can't tell what came first. More research is needed to confirm the results.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
23 / 100
- Randomizationnot randomized
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=40)+3.6/20
- Follow-upno follow-up reported
100 / 100
77 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervalsno confidence intervals
- Pre-registration+15/15
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 544 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
This design cannot establish causation — the findings describe an association, not a cause. Cross-sectional design cannot establish temporal sequence; associations may be reverse causation or due to confounding. No randomization in human study. Small sample size. Animal and in vitro results cannot be directly extrapolated to humans.
COI Unknown
Could not determine conflict of interest status
No conflict of interest or funding statement is present in the provided text, so potential conflicts cannot be assessed.
The provided text appears truncated and lacks a COI/funding section; no author affiliations or funding sources are listed. Sequencing was performed by Hangzhou Lianchuan Biotechnology Co., Ltd., but this appears to be a service provider, not a funder. Bacillus strain and mice were obtained from commercial vendors (Beina Biological Fungi and Bacteria Preparation Center, Jiangsu Jicui Yaoke Biotechnology Co., Ltd.).
Key takeaways
- 01
In patients, liver metastases had less diverse bacteria and more Bacillus compared to primary colon tumors.
- 02
Bacillus abundance correlated with tumor markers (r=0.588).
- 03
In lab dishes, Bacillus supernatant increased cancer cell migration (e.g., wound closure 59.1% vs 26.3%) and proliferation.
- 04
In mice, Bacillus increased metastatic tumor growth, and antibiotics reduced it.
- 05
The study did not report absolute risk increases for patients.
- 06
This study is early-stage and does not provide absolute risk numbers for patients.
- 07
It suggests that Bacillus might help colorectal cancer spread to the liver, but it's not proven.
- 08
The findings are based on a small number of patients (20 with liver metastases) and lab experiments.
- 09
Much more research is needed to know if targeting Bacillus could help patients.
Surprising findings
- Bacillus, a genus that includes common probiotics, was enriched in liver metastases and promoted cancer cell migration and proliferation.Bacillus species are often considered beneficial or harmless, so their association with cancer progression is counterintuitive.
- The effect of Bacillus supernatant was non-linear, with maximal effect at MOI 20 but reduced at MOI 50.Usually higher doses lead to stronger effects, but here the highest concentration had less impact, suggesting a complex dose-response.
- Liver metastases had lower microbial diversity than primary tumors.The liver is a filter for bacteria, so one might expect more diverse bacteria to be trapped there, but instead diversity was lower, suggesting selective pressure.
Practical takeaways
There's no direct action for patients yet, but researchers should further investigate Bacillus as a therapeutic target.
This is early-stage research with small sample size and no proof of causation. Absolute risk increases were not reported.
low confidenceIf you're considering probiotics, be aware that Bacillus species are sometimes included, but this study doesn't provide evidence against their general use.
The study didn't test probiotics; it tested a specific Bacillus strain in cancer models.
low confidenceFor scientists: consider targeting intratumoral bacteria and lipid metabolism pathways in future cancer studies.
Findings need validation in larger cohorts.
medium confidenceWhy this study matters
Bacillus Enriched in Liver Metastases
In a study of 40 patients, Bacillus was significantly enriched in colorectal cancer liver metastases compared to paired primary tumors (P=0.0059). Its abundance correlated with tumor markers CEA and CA19-9 (r=0.588, P<0.001).
This suggests a specific bacterium might play a role in metastasis, opening new avenues for treatment.
Bacillus Promotes Cancer Cell Aggressiveness
In lab experiments, Bacillus supernatant increased migration (wound closure 59.1% vs 26.3% at MOI 20) and proliferation of colorectal cancer cell lines.
This provides a potential mechanism for how bacteria could promote metastasis.
Antibiotics Reduced Metastatic Growth in Mice
In a mouse model, Bacillus increased metastatic tumor growth, but antibiotic treatment reduced this effect, suggesting a potential therapeutic strategy.
This hints that antibiotics might be repurposed to fight cancer spread, though with caveats.
Complex Interplay with Lipids and Immune Cells
Single-cell analysis identified APOE+ macrophages as lipid-associated cells with broad communication in the tumor microenvironment, linking bacteria, lipids, and immune cells.
It reveals a complex interplay between microbes, metabolism, and immunity in cancer.
Want the whole report?
Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists studied bacteria inside tumors that have spread from colorectal cancer to the liver. They found that a type of bacteria called Bacillus is more common in liver metastases than in the original colon tumors. This bacterium was linked to higher levels of certain tumor markers and fats. In lab tests, substances from Bacillus made cancer cells move and grow more. In mice, Bacillus made liver tumors grow bigger, and antibiotics reduced this effect. They also found special immune cells called APOE+ macrophages that might be involved.
Research results
In patients, liver metastases had less diverse bacteria and more Bacillus compared to primary colon tumors. Bacillus abundance correlated with tumor markers (r=0.588). In lab dishes, Bacillus supernatant increased cancer cell migration (e.g., wound closure 59.1% vs 26.3%) and proliferation. In mice, Bacillus increased metastatic tumor growth, and antibiotics reduced it. The study did not report absolute risk increases for patients.
What this means - more context
This study is early-stage and does not provide absolute risk numbers for patients. It suggests that Bacillus might help colorectal cancer spread to the liver, but it's not proven. The findings are based on a small number of patients (20 with liver metastases) and lab experiments. Much more research is needed to know if targeting Bacillus could help patients.
To characterize the microbial, metabolic, and immune differences between primary colorectal tumors and paired liver metastases, focusing on the role of intratumoral bacteria in the metastatic niche.
In this cross-sectional study of 20 non-metastatic CRC and 20 CRLM patients, liver metastases had lower microbial diversity and distinct microbial communities compared to primary tumors. Bacillus was enriched in liver metastases and correlated with serum tumor markers CEA and CA19-9 (r=0.588, P<0.001) and lipid-related metabolites. In vitro, Bacillus supernatant increased CRC cell migration and proliferation. In a mouse model, Bacillus increased metastatic tumor growth, and antibiotics reduced this effect. Metabolomics showed lipid accumulation, and single-cell analysis identified APOE+ macrophages. The study is limited by small sample size and correlative design; absolute risk increases were not reported.
Methods Used
5R 16S rDNA sequencing of 120 tissue specimens from 40 patients (20 non-metastatic CRC, 20 CRLM) and paired adjacent tissues; untargeted metabolomics; single-cell RNA sequencing analysis of public dataset GSE178318; in vitro wound healing, transwell, and CCK-8 assays with SW480 and SW620 cells; and an intrasplenic mouse model of CRLM.
Main Finding
Bacillus was enriched in colorectal cancer liver metastases compared to paired primary tumors (P=0.0059). Bacillus abundance positively correlated with CEA and CA19-9 (r=0.588, P<0.001) and with lipid metabolites (P<0.05). Bacillus supernatant increased SW480 and SW620 cell migration (e.g., wound closure 59.1% vs 26.3% at MOI 20) and proliferation. In mice, Bacillus increased metastatic tumor growth, and antibiotics reduced this effect. No absolute risk increases for clinical outcomes were reported. The study cannot establish causality.
Confidence Level
Moderate. The study integrates multiple approaches but is limited by small sample size, lack of species-level identification, and correlative nature. Contamination controls were used, but no independent tissue-processing blank was available.
Study Flags
Red Flags
- •Small sample size (20 patients per group)
- •Correlative design cannot establish causality
- •Bacillus not identified to species level, limiting specificity
Surprising Findings
Bacillus, a genus that includes common probiotics, was enriched in liver metastases and promoted cancer cell migration and proliferation.
Bacillus species are often considered beneficial or harmless, so their association with cancer progression is counterintuitive.
Practical Takeaways
There's no direct action for patients yet, but researchers should further investigate Bacillus as a therapeutic target.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 544 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Human Cross-Sectional
Subject
Moderate probability
on the GRADE evidence scale
This study looked at samples from people with colon cancer and liver metastasis, and also did experiments in cells and mice. It found some links between a type of bacteria, certain fats, and immune cells, but it cannot prove that the bacteria cause the cancer to spread. It only shows that these things are found together.
Strengths
- Multi-omics integration (16S rDNA, metabolomics, single-cell RNA-seq).
- Paired primary and metastatic samples from same patients.
- Functional validation in vitro and in vivo.
Weaknesses
- Cross-sectional human design cannot establish causality.
- Small sample size limits statistical power and generalizability.
- No temporal sequence to infer directionality.
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists studied bacteria inside tumors that have spread from colorectal cancer to the liver. They found that a type of bacteria called Bacillus is more common in liver metastases than in the original colon tumors. This bacterium was linked to higher levels of certain tumor markers and fats. In lab tests, substances from Bacillus made cancer cells move and grow more. In mice, Bacillus made liver tumors grow bigger, and antibiotics reduced this effect. They also found special immune cells called APOE+ macrophages that might be involved.
Research results
In patients, liver metastases had less diverse bacteria and more Bacillus compared to primary colon tumors. Bacillus abundance correlated with tumor markers (r=0.588). In lab dishes, Bacillus supernatant increased cancer cell migration (e.g., wound closure 59.1% vs 26.3%) and proliferation. In mice, Bacillus increased metastatic tumor growth, and antibiotics reduced it. The study did not report absolute risk increases for patients.
What this means - more context
This study is early-stage and does not provide absolute risk numbers for patients. It suggests that Bacillus might help colorectal cancer spread to the liver, but it's not proven. The findings are based on a small number of patients (20 with liver metastases) and lab experiments. Much more research is needed to know if targeting Bacillus could help patients.
To characterize the microbial, metabolic, and immune differences between primary colorectal tumors and paired liver metastases, focusing on the role of intratumoral bacteria in the metastatic niche.
In this cross-sectional study of 20 non-metastatic CRC and 20 CRLM patients, liver metastases had lower microbial diversity and distinct microbial communities compared to primary tumors. Bacillus was enriched in liver metastases and correlated with serum tumor markers CEA and CA19-9 (r=0.588, P<0.001) and lipid-related metabolites. In vitro, Bacillus supernatant increased CRC cell migration and proliferation. In a mouse model, Bacillus increased metastatic tumor growth, and antibiotics reduced this effect. Metabolomics showed lipid accumulation, and single-cell analysis identified APOE+ macrophages. The study is limited by small sample size and correlative design; absolute risk increases were not reported.
Methods Used
5R 16S rDNA sequencing of 120 tissue specimens from 40 patients (20 non-metastatic CRC, 20 CRLM) and paired adjacent tissues; untargeted metabolomics; single-cell RNA sequencing analysis of public dataset GSE178318; in vitro wound healing, transwell, and CCK-8 assays with SW480 and SW620 cells; and an intrasplenic mouse model of CRLM.
Main Finding
Bacillus was enriched in colorectal cancer liver metastases compared to paired primary tumors (P=0.0059). Bacillus abundance positively correlated with CEA and CA19-9 (r=0.588, P<0.001) and with lipid metabolites (P<0.05). Bacillus supernatant increased SW480 and SW620 cell migration (e.g., wound closure 59.1% vs 26.3% at MOI 20) and proliferation. In mice, Bacillus increased metastatic tumor growth, and antibiotics reduced this effect. No absolute risk increases for clinical outcomes were reported. The study cannot establish causality.
Confidence Level
Moderate. The study integrates multiple approaches but is limited by small sample size, lack of species-level identification, and correlative nature. Contamination controls were used, but no independent tissue-processing blank was available.
Study Flags
Red Flags
- •Small sample size (20 patients per group)
- •Correlative design cannot establish causality
- •Bacillus not identified to species level, limiting specificity
Surprising Findings
Bacillus, a genus that includes common probiotics, was enriched in liver metastases and promoted cancer cell migration and proliferation.
Bacillus species are often considered beneficial or harmless, so their association with cancer progression is counterintuitive.
Practical Takeaways
There's no direct action for patients yet, but researchers should further investigate Bacillus as a therapeutic target.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 544 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Human Cross-Sectional
Subject
Moderate probability
on the GRADE evidence scale
This study looked at samples from people with colon cancer and liver metastasis, and also did experiments in cells and mice. It found some links between a type of bacteria, certain fats, and immune cells, but it cannot prove that the bacteria cause the cancer to spread. It only shows that these things are found together.
Strengths
- Multi-omics integration (16S rDNA, metabolomics, single-cell RNA-seq).
- Paired primary and metastatic samples from same patients.
- Functional validation in vitro and in vivo.
Weaknesses
- Cross-sectional human design cannot establish causality.
- Small sample size limits statistical power and generalizability.
- No temporal sequence to infer directionality.
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study used several advanced methods to look at bacteria, chemicals, and cells, which is a strength. However, it only looked at a small number of patients at one time, so we can't be sure the findings apply to everyone, and we can't tell what came first. More research is needed to confirm the results.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
23 / 100
- Randomizationnot randomized
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=40)+3.6/20
- Follow-upno follow-up reported
100 / 100
77 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervalsno confidence intervals
- Pre-registration+15/15
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 544 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
This design cannot establish causation — the findings describe an association, not a cause. Cross-sectional design cannot establish temporal sequence; associations may be reverse causation or due to confounding. No randomization in human study. Small sample size. Animal and in vitro results cannot be directly extrapolated to humans.
COI Unknown
Could not determine conflict of interest status
No conflict of interest or funding statement is present in the provided text, so potential conflicts cannot be assessed.
The provided text appears truncated and lacks a COI/funding section; no author affiliations or funding sources are listed. Sequencing was performed by Hangzhou Lianchuan Biotechnology Co., Ltd., but this appears to be a service provider, not a funder. Bacillus strain and mice were obtained from commercial vendors (Beina Biological Fungi and Bacteria Preparation Center, Jiangsu Jicui Yaoke Biotechnology Co., Ltd.).
Standing
The people behind it
The researchers who wrote the study this analysis is built on.
Authored by
11 researchersIf this is your work, this is how we attribute it on Fit Body Science. Juhang Chu is listed as the lead author.