The research team, based at Friedrich-Alexander Universität Erlangen-Nürnberg, designed an in vitro model that closely mimics the metabolic environment found in obese patients. In obesity and the metabolic syndrome, hyperlipidemia is a defining feature: free fatty acids released from adipose tissue circulate in the bloodstream, predominantly bound to albumin. To replicate these conditions in the laboratory, the researchers incubated six human colorectal cancer cell lines with oleic acid complexed to bovine serum albumin. The panel included three microsatellite stable lines, HT29, Caco-2 and SW480, and three microsatellite instable lines, SW48, LoVo and HCT116, each with distinct molecular backgrounds and driver mutations. Oleic acid was chosen deliberately, as it represents approximately 80 percent of the circulating monounsaturated fatty acids in human blood, making it a physiologically relevant exposure variable.

The results were striking. Within 48 hours of exposure, the cells accumulated triglycerides in a dose-dependent manner, and oil red O staining revealed the formation of abundant cytosolic lipid droplets. At the same time, the concentration of free fatty acids in the culture supernatant declined over time, confirming that the cancer cells were actively taking up the fatty acids from their surroundings. A key molecular marker of this process was perilipin-2, or PLIN2, a structural protein component of lipid droplets. Both the mRNA and protein levels of PLIN2 rose dose-dependently in the treated cells, and immunofluorescence staining visualised the enhanced formation of lipid droplets in the cytoplasm. Similar findings were observed across all six cell lines, suggesting that this lipid storage response is not restricted to a particular molecular subtype of colorectal cancer and operates independently of microsatellite stability status.

Beneath this visible lipid accumulation, the researchers documented a profound reprogramming of lipid metabolism. When exogenous fatty acids flooded the cells, the expression of enzymes responsible for de novo lipid synthesis declined. ATP citrate lyase, or ACLY, which generates cytosolic acetyl-CoA from citrate to provide building blocks for new fatty acids, showed slightly reduced mRNA expression, and fatty acid synthase, FASN, was downregulated in a dose-dependent manner. Stearoyl-CoA desaturase 1, SCD1, the key enzyme for desaturating saturated fatty acids, was also reduced, fitting with the abundant supply of monounsaturated oleate arriving from outside. In contrast, diacylglycerol-O-acyltransferase 2, DGAT2, a central enzyme of triglyceride synthesis, was increased in HT29 and Caco-2 cells, consistent with the elevated triglyceride levels. The cells, in effect, switched from manufacturing their own fat to importing and storing it.

The study also revealed an upregulation of the machinery for burning fat. Carnitine palmitoyltransferase 1A, CPT1A, the rate-limiting enzyme that shuttles long-chain fatty acids into mitochondria for beta-oxidation, increased dose-dependently at both mRNA and protein levels. Adipose triglyceride lipase, ATGL, which catalyses the first step of intracellular triglyceride hydrolysis, rose in five of the six cell lines, and the lipolytic enzymes HSL and MAGL were also elevated at the mRNA level in HT29 cells. However, functional mitochondrial stress tests painted a more nuanced picture. Oleate treatment produced only slight, statistically non-significant increases in basal respiration, and while the CPT1 inhibitor etomoxir reduced maximal respiration in HT29 cells, Caco-2 cells showed no comparable response. The authors suggest that elevated CPT1A may reflect an enhanced capacity or adaptive readiness for fatty acid oxidation, while most imported fatty acids are actually channelled into storage within lipid droplets rather than immediately combusted.

The most consequential findings concern what this lipid loading does to cancer cell behaviour. Proliferation increased dose-dependently in oleate-stimulated cells, and migratory activity, measured in Boyden chamber assays, was significantly enhanced. At the molecular level, the researchers observed a classic cadherin switch: expression of E-cadherin, the adhesive molecule that stabilises junctions between epithelial cells, was downregulated, while N-cadherin expression rose. This shift is strongly linked to greater migratory and invasive capability, as loss of E-cadherin allows cancer cells to detach from the primary tumour site. The epithelial-mesenchymal transition markers SNAIL and TWIST were also increased in HT29 cells, although these changes were more variable across the other lines. Notably, the proinflammatory cytokine interleukin-8, a marker associated with proliferation, angiogenesis, metastasis and poor outcome in colon carcinoma, increased dose-dependently in four of the six cell lines, hinting that lipid accumulation may fuel inflammatory signalling within the tumour.

To connect these laboratory observations with clinical reality, the team analysed tumour tissue from colorectal cancer patients of normal weight, with body mass index between 20 and 25, and patients with Grade I or II obesity, with BMI between 30 and 40. Obese patients showed a tendency toward higher PLIN2 expression, although the difference did not reach statistical significance in this relatively small cohort. Immunohistochemistry, however, told a clearer story: PLIN2 staining was markedly stronger in tumours from obese patients, and Ki67 staining revealed a higher number of proliferating cells in the tumours of the obese group. In silico analysis of large patient cohorts added a prognostic dimension, showing that high PLIN2 expression correlated with poorer overall and disease-free survival in colorectal carcinoma patients.

Perhaps most intriguing was the significant correlation, observed across 350 human colorectal cancer tissues from The Cancer Genome Atlas, between PLIN2 and CPT1A expression, mirroring the relationship seen in vitro. Patients with high CPT1A expression likewise showed poorer overall and disease-free survival. This association suggests that lipid storage and the capacity for fatty acid oxidation are coordinately regulated in human tumours, consistent with a state of heightened lipid flux. The authors caution that further experiments are needed to establish a causal relationship between the two proteins, and that BMI is only an indirect marker of metabolic status, since it does not directly reflect circulating free fatty acid concentrations. Functional studies and larger, independently validated cohorts incorporating detailed metabolic phenotyping will be required to confirm the clinical relevance of these findings.

The broader implications of this work extend well beyond the culture dish. The study positions exogenous fatty acid uptake as a third route, alongside de novo lipogenesis and lipolysis, by which cancer cells satisfy their high demand for fat, and one that may be particularly important in obesity-associated hyperlipidemia. The findings also resonate with related research across gastrointestinal cancers: recent work in pancreatic ductal adenocarcinoma demonstrated a functional connection between PLIN2 and CPT1A in regulating lipid droplet and mitochondrial interactions, while studies in gastric cancer have linked CPT1A-associated metabolic reprogramming to JAK/STAT3 signalling. Given that CPT1 inhibitors are already being tested for anti-cancer effects, the authors raise the provocative question of whether the efficacy of such strategies, and even of antiangiogenic therapies that induce fatty acid uptake through CD36, might differ between obese and normal-weight patients. If confirmed, the humble lipid droplet, long regarded as a passive fat reservoir, could emerge as both a biomarker and a therapeutic target in the fight against colorectal cancer.

Subject of Research: The role of exogenous fatty acid uptake, lipid droplet formation and PLIN2 expression in promoting the tumorigenic behaviour of colorectal cancer cells

Article Title: Lipid Accumulation Promotes Tumorigenic Behaviour of Colorectal Cancer Cells

Article References: Itzenhäuser, T., Schildt, F. S., Jochem, S., Sommer, J., Stürzl, M., Naschberger, E., Boßerhoff, A. K., & Hellerbrand, C. (2026). Lipid Accumulation Promotes Tumorigenic Behaviour of Colorectal Cancer Cells. Journal of Cellular and Molecular Medicine, 30(19), Article e71393. https://doi.org/10.1111/jcmm.71393

Image Credits: AI Generated

DOI: 10.1111/jcmm.71393

Keywords: colorectal cancer, lipid droplets, fatty acid uptake, obesity, PLIN2, CPT1A, oleic acid, lipid metabolism, beta-oxidation, tumour progression, EMT, interleukin-8

Writing in Nature Microbiology, Tiantian Yu, Shujian Yuan, Yinzhao Wang, Fengping Wang and colleagues report the enrichment of a heat-loving archaeon that appears capable of converting long-chain fatty acids directly into methane without bacterial partners. The organism, provisionally named Candidatus Methanoglobus sphaerolipidus DLY3, belongs to the class Archaeoglobi, a group of thermophilic archaea better known for sulfate reduction than for making methane. Through a combination of selective enrichment, growth experiments, microscopy, stable isotope tracing, metagenomics and metatranscriptomics, the team assembled a case that this single archaeon can ingest fatty substrates such as oleic acid and exhale methane, executing every step of the transformation on its own.

The metabolic itinerary the researchers propose is remarkable in its completeness. Ca. M. sphaerolipidus deploys the beta-oxidation pathway, the same enzymatic assembly line that mitochondria and many bacteria use to clip two-carbon units from fatty acid chains, to break long hydrocarbon tails into smaller fragments. Those fragments are then funneled into the Wood–Ljungdahl pathway, an ancient carbon-fixation route that channels one-carbon compounds toward the central metabolism of the cell. Finally, the reaction is completed by methyl-coenzyme M reductase, or MCR, the nickel-containing enzyme that sits at the heart of all biological methane production, together with methyltransferase complexes that shuffle methyl groups into the methanogenic pipeline. The authors have dubbed this full sequence liparotrophy, from the Greek word for fat.

The mechanistic significance of this finding is hard to overstate. Until recently, the known routes to methane were limited to a handful of well-characterized modes: reduction of carbon dioxide with hydrogen, the acetoclastic split of acetate, methylotrophic fermentation of methylated compounds, methyl reduction, methoxydotrophic use of methoxylated aromatics and, more recently, alkylotrophy, in which archaea activate short-chain alkanes through alkyl-coenzyme M intermediates. Each new mode has expanded the roster of substrates that biology can convert into the most reduced form of carbon. Liparotrophy now adds long-chain fatty acids—abundant, energy-dense molecules that pervade sediments, petroleum reservoirs and anaerobic digesters—to that list, and it does so with a single organism rather than a consortium.

The evidence base for the claim is layered. In enrichment cultures fed oleic acid, methane accumulated while Ca. M. sphaerolipidus rose to dominance in the community, a pattern consistent with the archaeon being the active methane producer. Stable isotope tracing confirmed that carbon from the labeled fatty acid substrate ended up in the methane, directly linking the lipid feedstock to the gaseous product. Microscopy, including hybridization-based fluorescent probing and transmission electron microscopy, revealed the morphology and identity of the enriched archaeal cells. And metagenomic and metatranscriptomic sequencing showed not only that the genome of Ca. M. sphaerolipidus encodes the full beta-oxidation, Wood–Ljungdahl and methanogenesis machinery, but that the relevant genes are actively transcribed when fatty acids are on the menu.

Perhaps equally intriguing is the organism’s dietary flexibility. Beyond oleic acid, the enrichment cultures also produced methane when supplied with methanol, a one-carbon alcohol. That versatility places Ca. M. sphaerolipidus within a growing group of Archaeoglobi that blur the line between canonical methanogens and their metabolically adventurous relatives. Recent years have seen methanogenesis or MCR-linked metabolism documented in unexpected corners of the archaeal domain, from Korarchaeia and Methanonezhaarchaeia in the phylum Thermoproteota to nontraditional MCR-bearing lineages in geothermal springs. The new finding reinforces the emerging picture that methane metabolism is far more phylogenetically widespread, and far more biochemically inventive, than the classical methanogen textbooks implied.

Evolutionarily, liparotrophy adds weight to the hypothesis that archaeal alkane and fatty acid metabolism share deep roots. Comparative work has suggested that methylotrophic methanogenesis may represent an ancient origin of the pathway, with the enzymes that activate and cleave carbon–carbon bonds in hydrocarbons diversifying from related alkyl-coenzyme M chemistry. If Archaeoglobi—one of the earliest diverging archaeal lineages—can strip two-carbon units from fatty acids and terminate them in methane via MCR, then the capacity for anaerobic lipid degradation may be far older and more broadly distributed than the syntrophic bacteria-archaea partnerships that dominate anaerobic environments today. The phylogenomic analyses in the new study, which place the MCR and ACR protein families of Ca. Methanoglobus within the broader family tree of methane-related reductases, will help researchers trace how these enzymatic modules were assembled, shuffled and repurposed across billions of years.

The discovery also carries practical weight. Long-chain fatty acids are notorious bottlenecks in anaerobic digestion, the biotechnology that turns food waste, sewage sludge and lipid-rich dairy effluent into biogas. Because fatty acids inhibit the syntrophic consortia that normally process them, high-lipid feedstocks can destabilize digesters and depress methane yields. A thermophilic archaeon that can directly convert these compounds to methane, without the metabolic hand-offs that make conventional syntrophy fragile, could point toward more robust biogas systems for greasy wastes. The thermophilic nature of the organism is a good fit for the elevated temperatures of industrial digesters, and its capacity to switch between fatty acids and methanol suggests metabolic flexibility that engineers could exploit.

Geologically, the implications reach into the deep subsurface. Fatty acids derived from dead biomass are abundant in anoxic sediments, hydrothermal systems and petroleum-associated environments, and the methanogenic degradation of these compounds has long been invoked to explain methane generation in oil reservoirs and coal beds. If liparotrophic archaea are active players in those settings, the microbial routes and rates of subsurface methane production may need revision, with consequences for models of the global methane budget and for understanding where biogenic natural gas comes from. The Tengchong hot springs that yielded DLY3 are just one terrestrial geothermal system; related Ca. Methanoglobus genomes have now been recovered from various thermal environments, hinting that liparotrophy may be a hidden but common metabolism wherever heat and lipids meet.

As with any single-organism claim emerging from enrichment cultures, confirmation will matter. Ca. M. sphaerolipidus has not yet been isolated in pure culture, and the authors make their cultures available to other researchers under material transfer agreements precisely so the wider community can test, refine and extend the findings. But the convergence of isotope data, gene expression profiles and growth behavior makes a compelling case that the boundaries of methanogenesis have just been redrawn once again. A few years ago, methane was the exclusive business of a specialized few; today, it is increasingly clear that across the archaeal tree, evolution has repeatedly found ways to breathe out this simplest of hydrocarbons—and now, it seems, straight from the fats of the dead into the gas of the future.

Subject of Research: Direct methanogenic conversion of long-chain fatty acids by thermophilic Archaeoglobi

Article Title: Evidence of direct methane production from long-chain fatty acids by thermophilic Archaeoglobi

Article References: Yu, T., Yuan, S., Wang, Y., & Wang, F. (2026). Evidence of direct methane production from long-chain fatty acids by thermophilic Archaeoglobi. Nature Microbiology. https://doi.org/10.1038/s41564-026-02490-5

Image Credits: AI Generated

DOI: 10.1038/s41564-026-02490-5

Keywords: methanogenesis, Archaeoglobi, long-chain fatty acids, liparotrophy, beta-oxidation, Wood–Ljungdahl pathway, methyl-coenzyme M reductase, thermophiles, hot springs, metagenomics, anaerobic digestion, archaea