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Vitamin K2 belongs to a family of compounds known as menaquinones, which differ from one another in the length of their side chain, and this structural variation has practical consequences for how each homologue behaves in the body. The shorter-chain menaquinone-4 and the medium-chain menaquinone-7 evaluated in the study were absorbed into colonic tissue alongside their appearance in faecal matter, whereas the long-chain menaquinone-9 remained largely excluded from the mucosa even though it was abundantly present in the intestinal lumen. This dissociation between luminal presence and tissue uptake is a reminder that a compound’s anti-inflammatory activity does not necessarily depend on systemic absorption; menaquinone-9 retained meaningful effects on cytokine expression despite its poor colonic penetration, which suggests that locally acting mechanisms at the mucosal surface, or indirect effects mediated through the microbiota, may contribute alongside direct tissue-level signalling.

The choice of the azoxymethane/dextran sulphate sodium model is significant for interpreting these findings. This two-step protocol first exposes mice to a genotoxic carcinogen and then subjects them to repeated cycles of colonic epithelial injury and repair, producing tumours that arise on a background of chronic inflammation. That sequence mirrors one of the recognised pathways of human colorectal carcinogenesis, in which persistent inflammatory conditions such as colitis precede and promote malignant transformation. Because inflammation is not merely a by-product but an active driver in this model, interventions that dampen inflammatory signalling can be evaluated for their potential to interrupt the tumour-promoting feed-forward loop between tissue damage, immune activation, and epithelial proliferation.

Interleukin-6 occupies a central position in this loop. Produced by epithelial cells, macrophages, and other immune populations in the gut, it activates signalling pathways that promote epithelial cell survival, proliferation, and resistance to apoptosis, thereby creating conditions favourable for tumour expansion. The observation that menaquinone-7 supplementation and supplementation with the vitamin K2-producing Lactobacillus plantarum strain both reduced interleukin-6 levels therefore points to a plausible mechanistic target. The concurrent improvement in the localisation of interleukin-10, an anti-inflammatory cytokine, suggests a rebalancing of the mucosal immune environment rather than simple global immunosuppression, which would be an undesirable outcome in a cancer context.

The elevated interleukin-10 seen in untreated AOM/DSS-control mice deserves particular attention. Although interleukin-10 is generally regarded as protective and anti-inflammatory, tumours can co-opt immunosuppressive cytokine networks to build a microenvironment that shields malignant cells from effective immune surveillance. The pattern observed in the control animals, with elevated interleukin-10 accompanying chronic mucosal inflammation and glandular distortion, is consistent with the establishment of such an immunosuppressive tumour microenvironment. The shift toward more homeostatic interleukin-10 distribution in the treated groups may therefore reflect a normalisation of immune regulation rather than a simple increase or decrease in any single cytokine.

The nuclear factor kappa B pathway provides a candidate molecular link between the vitamin K2 interventions and the cytokine changes measured in the study. This transcription factor family sits upstream of many inflammatory genes, including those encoding interleukin-6, interleukin-8, and tumour necrosis factor alpha, and its constitutive activation is a well-documented feature of inflammation-associated cancers. Inhibition of this pathway can therefore cascade into coordinated reductions across multiple pro-inflammatory mediators, which is the pattern the authors observed across all vitamin K2 interventions. Confirming this mechanism definitively in vivo would require additional experimentation, but the consistency of the cytokine modulation across homologues with very different absorption profiles lends indirect support to a pathway-level effect.

The microbiological dimension of the study adds a layer of complexity that distinguishes it from simple nutraceutical experiments. By combining next-generation sequencing with classical culture methods, the researchers could track both the overall composition of the gut community and the abundance of specific Lactobacillus species. The finding that menaquinone-9 supplementation markedly increased faecal Lactobacillus abundance despite its poor absorption raises the possibility that this long-chain homologue acts partly as a substrate or selective factor favouring lactobacilli in the lumen. If so, the anti-inflammatory activity of menaquinone-9 could be mediated at least in part through reshaping the microbial community rather than through direct effects on host tissue, an interpretation that would align with the growing recognition that microbiota composition is itself a modifiable determinant of colonic inflammation.

The use of a naturally produced form of vitamin K2, generated by a Lactobacillus plantarum strain rather than supplied as a purified synthetic compound, bridges two research traditions that have largely developed in parallel: probiotic therapy and vitamin-based chemoprevention. Certain intestinal bacteria, lactobacilli among them, are known to synthesise menaquinones, and the study’s design allowed the authors to compare a bacterial source of the vitamin with chemically defined homologues. The comparable anti-inflammatory effects observed with the natural preparation and with menaquinone-7 suggest that the bioactive molecule, rather than the delivery vehicle, drives much of the effect, although the probiotic strain may contribute additional benefits through its own interactions with the mucosal immune system.

Methodologically, the quantification of menaquinones by ultra-pressure liquid chromatography coupled to tandem mass spectrometry with atmospheric pressure chemical ionisation represents an important strength. Vitamin K2 homologues are hydrophobic molecules that differ only subtly in side-chain length, making their separate quantification in complex biological matrices technically demanding. The ability to measure individual homologues in both faeces and colonic homogenates is what made it possible to detect the divergent absorption behaviours of menaquinone-4, -7, and -9, a distinction that would have been invisible if only total vitamin K activity had been assessed. The supplementary detection of menaquinone-5 and menaquinone-6 in these samples further indicates that the analytical method captured intermediate homologues, with menaquinone-5 in the colon falling below the limit of detection in all groups.

The immunofluorescence and western blotting approaches used to profile cytokine expression complement each other in a useful way. Immunofluorescence preserves spatial information, revealing where within the mucosal architecture a given cytokine is being produced, which is essential for interpreting changes in the tumour microenvironment where immune cells, epithelial cells, and stromal components are unevenly distributed. Western blotting provides quantitative protein-level confirmation. Together these methods allowed the authors to describe not just how much of each cytokine was present but how its distribution across the tissue changed with treatment, which is how the improved localisation of interleukin-10 was identified.

It is worth emphasising what the mouse model can and cannot establish. The AOM/DSS protocol reliably reproduces inflammation-driven colonic tumorigenesis and is widely used for preclinical chemoprevention research, but the inflammatory and microbial context of the laboratory mouse differs from that of human patients, whose tumours arise over decades against a backdrop of individual diet, microbiota, and immune history. The BALB/c strain used here is an inbred line, which reduces variability within the experiment but also limits the genetic diversity over which the findings can be generalised. Translating these results into human chemoprevention strategies will require studies that account for human microbiome variability, dietary vitamin K intake, and the pharmacokinetics of menaquinone supplementation in people with existing colonic pathology.

The dosing and formulation details recorded in the supplementary materials, including the composition of the purified diets and the preparation procedures for each homologue, matter for reproducibility and for future comparative work. Because menaquinones are fat-soluble and vary in bioavailability depending on the vehicle and dietary matrix, standardised dietary composition is essential when comparing interventions across laboratories. The documentation of these procedures, together with the semi-quantitative histopathological scoring criteria for mucosal and submucosal damage, provides a framework that other groups can adopt when testing related interventions.

The collaborative structure of the research team reflects the multidisciplinary demands of this kind of study. Microbiologists at Jagiellonian University Medical College handled the bacterial strain characterisation and culture work, veterinary scientists contributed to the animal model, analytical chemists developed the mass spectrometric quantification of menaquinones, oncologists and cancer metabolism researchers contributed expertise on the tumour biology, and pathologists performed the histopathological assessment. This breadth was necessary because the central question, whether a bacterial vitamin can modulate inflammation in a way that alters cancer-relevant biology, spans microbiology, nutrition, immunology, and oncology simultaneously.

Looking forward, several questions follow naturally from these findings. Whether the cytokine modulation observed during the intervention translates into reduced tumour burden or improved survival in longer-term follow-up is a critical next step. Whether the NF-kappa B pathway inhibition is direct or mediated through upstream changes in the microbiota or in epithelial barrier function remains to be resolved. And whether the homologue-specific differences in absorption and microbiota effects persist in animals with more diverse microbial communities, or in humans, will determine which menaquinone, if any, is best suited for chemoprevention trials. The open access publication of this work, funded by the National Science Centre Poland, ensures that these questions can be pursued by any laboratory with the appropriate model systems and analytical capabilities.

Subject of Research: colorectal cancer

Article Title: Anti-inflammatory effects of vitamin K2 and Lactobacillus plantarum in a mouse model of colorectal cancer

Article References: Anti-inflammatory effects of vitamin K2 and Lactobacillus plantarum in a mouse model of colorectal cancer. (n.d.). https://doi.org/10.1186/s12915-026-02742-0

Image Credits: AI Generated

DOI: 10.1186/s12915-026-02742-0

Keywords: vitamin K2, menaquinones, Lactobacillus plantarum, colorectal cancer, gut microbiota, cytokines, NF-κB, mouse model, probiotics, chemoprevention, Anti-inflammatory, effects