A preclinical investigation in cancer-associated cachexia has demonstrated that administering fibrinogen-like protein 1, known as FGL1, counteracts severe adipose and skeletal muscle wasting in melanoma-bearing mice by signaling through lymphocyte activation gene-3, or LAG-3. The research, conducted in a murine model inoculated with B16F10 melanoma cells, identified an unexpected upregulation of FGL1 within white adipose tissue during the progressive development of cancer cachexia. Exogenous administration of a recombinant FGL1-Fc fusion protein significantly attenuated tumor-induced loss of total body weight, sustained epididymal adipose depots, and preserved gastrocnemius muscle architecture. Concurrently, the treatment altered the expression profiles of key enzymes governing lipid synthesis and muscle breakdown. Crucially, antibody-mediated blockade of the LAG-3 receptor completely abrogated these protective benefits, establishing that the anti-cachectic properties of FGL1 rely directly upon the intact FGL1-LAG-3 signaling axis. These findings identify an immunometabolic pathway linking tumor presence to peripheral tissue preservation, revealing a specialized molecular mechanism that restrains the destructive wasting syndrome associated with experimental melanoma.
Cancer-associated cachexia is a multifaceted metabolic syndrome defined by involuntary, progressive loss of adipose tissue and skeletal muscle mass, culminating in profound physical frailty and systemic debilitation. Clinically, cachexia affects an estimated fifty to eighty percent of cancer patients, varying by primary tumor classification and diagnostic stage, and accounts directly for approximately twenty percent of all cancer-related deaths. The unrelenting catabolism of muscle and fat severely degrades patient functional independence, reduces tolerance and responsiveness to systemic antineoplastic regimens, and drastically diminishes overall survival. Despite decades of clinical recognition and considerable investigative effort, the United States Food and Drug Administration has approved no pharmacological therapies specifically indicated to treat or reverse cancer-associated cachexia. Emerging pathophysiological models indicate that adipose tissue depletion often emerges prior to the manifestation of classical systemic cachexia markers, suggesting that early functional disturbances in white adipose tissue actively influence disease trajectory rather than merely reflecting passive terminal wasting.
To explore transcriptomic alterations in white adipose tissue during cachectic progression, the study team subjected epididymal fat pads from cachectic mice to unbiased ribonucleic acid sequencing. Comparisons between B16F10 tumor-bearing mice and non-tumor control animals revealed substantial transcriptomic reprogramming, characterized by the statistically significant upregulation of 807 genes and the downregulation of 864 genes within epididymal adipose tissue, while 12,502 transcripts remained unchanged. Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the top enriched pathways were pathways in cancer, coronavirus disease, and human papillomavirus infection, confirming widespread immune-related perturbations within the adipose microenvironment. Fgl1 emerged as one of the most prominently upregulated transcripts. Quantitative reverse transcription polymerase chain reaction and Western blot analyses confirmed elevated Fgl1 messenger RNA and protein levels in epididymal white adipose tissue. Subsequent gene expression screening across spleen, skeletal muscle, kidney, lung, stomach, and intestine detected no significant alterations, demonstrating that pathological Fgl1 induction was strictly localized to white adipose tissue and the liver.
The experimental protocols utilized male C57BL/6J mice aged seven to eight weeks, purchased from Charles River, following a standardized one-week laboratory acclimatization period. Animals were housed in temperature-controlled rooms maintained at twenty-three degrees Celsius with forty to sixty percent relative humidity under an established twelve-hour light and dark cycle, with ad libitum access to water and standard chow. Cultured B16F10 melanoma cells, procured from the National Collection of Authenticated Cell Cultures and maintained in Dulbecco’s Modified Eagle Medium supplemented with ten percent fetal bovine serum and one percent penicillin-streptomycin, were subcutaneously injected into the upper flanks of the test cohort at a concentration of one million cells in one hundred microliters of phosphate-buffered saline. Control mice received identical vehicle injections without tumor cells. Body weights and individual tissue masses were monitored systematically, and any animals exhibiting tumor ulceration or active bleeding were excluded prior to therapeutic testing.
Because FGL1 is known to exert immune-suppressive properties that could inadvertently enhance primary malignancy, the researchers systematically analyzed the therapeutic timing of intraperitoneal FGL1-Fc administration. Administration initiated early on day seven post-inoculation, consisting of six doses of two hundred micrograms per mouse delivered every other day, substantially accelerated primary B16F10 tumor growth compared to controls. Conversely, initiating identical two-hundred-microgram FGL1-Fc dosing at intermediate and late disease stages on day fourteen, delivered every other day for three total doses, exhibited no measurable impact on primary tumor volume or overall tumor growth kinetics. This critical differentiation established an experimental window wherein the direct anti-cachectic actions of FGL1 could be evaluated independently of primary tumor enlargement. The authors concluded that potential therapeutic applications of the FGL1 protein in cachexia are strictly confined to intermediate or advanced stages when antineoplastic immunotherapy has already failed or established drug resistance.
In the mid-to-late stage intervention cohorts, FGL1-Fc treatment produced significant structural and phenotypic preservation across depleted tissues. Mice bearing B16F10 tumors exhibited severe loss of tumor-free body weight, which was markedly mitigated by late FGL1-Fc administration. Nuclear magnetic resonance body composition analysis using a minispec analyzer revealed that FGL1-Fc treatment significantly elevated total body fat percentage and produced an upward trend in total lean mass that did not achieve statistical significance. Anatomical dissection demonstrated that FGL1-Fc administration preserved epididymal white adipose tissue mass and prevented the characteristic shrinkage of unilocular adipocyte lipid droplets visible on hematoxylin and eosin histology. Concurrently, the treatment significantly rescued gastrocnemius muscle weight, increased muscle fiber cross-sectional area, and preserved overall skeletal muscle architecture.
At the biochemical level, FGL1 administration reversed key disturbances in lipid metabolism within the white adipose tissue of cachectic animals. Quantitative analysis of rate-limiting enzymes revealed that the gene expression of fatty acid synthase and stearoyl-CoA desaturase 1 was markedly depressed in the epididymal fat of untreated tumor-bearing mice, whereas FGL1-Fc therapy counteracted this transcriptional decline. In contrast, the expression of diacylglycerol O-acyltransferase 2, an enzyme central to fatty acid storage, was not rescued. Evaluation of hormone-sensitive lipase, the enzyme executing intracellular lipolysis, revealed no alterations in total protein abundance or phosphorylation status across experimental groups. Consistent with the restoration of fatty acid synthetic machinery, the profound reduction in circulating non-esterified fatty acids and glycerol observed in untreated tumor-bearing mice was significantly reversed by FGL1-Fc treatment, confirming a functional restoration of circulating lipid metabolites without abnormal enhancement of baseline lipolytic enzyme activation.
Parallel evaluations in skeletal muscle tissue illuminated the transcriptional pathways through which FGL1-Fc counteracted muscular wasting.
To determine whether the anti-cachectic properties of FGL1 require direct engagement with its recognized physiological receptor, the authors introduced a targeted receptor blockade using a monoclonal anti-LAG-3 antibody. Male mice harboring established B16F10 tumors were administered one hundred micrograms of anti-LAG-3 antibody via intraperitoneal injection on experimental days fourteen and eighteen, alongside FGL1-Fc or control immunoglobulin. Neither the anti-LAG-3 antibody alone nor the combination regimen altered primary tumor growth kinetics during this late-stage window. However, the co-administration of the anti-LAG-3 blocking antibody completely abolished the therapeutic effects of FGL1-Fc. Mice receiving both agents experienced unimpeded wasting of total body weight, rapid depletion of epididymal adipose depots, and severe gastrocnemius muscle atrophy identical to vehicle-treated cachectic controls.
Cellular and systemic immunological analyses uncovered the downstream anti-inflammatory mechanisms responsible for tissue preservation. Flow cytometric profiling of infiltrating immune populations isolated from digested epididymal adipose tissue revealed that FGL1-Fc administration significantly decreased the frequency of interferon-gamma-producing CD8-positive cytotoxic T lymphocytes within fat pads. Systemically, circulating concentrations of interleukin-6, a key proinflammatory driver of cancer-associated cachexia, were elevated in untreated tumor-bearing mice and dropped by nearly forty percent following FGL1-Fc therapy. Additionally, circulating corticosterone, the primary glucocorticoid stimulated by systemic inflammatory stress and hypothalamic-pituitary-adrenal axis activation, was elevated sixfold in untreated tumor-bearing mice but was reduced by thirty percent in mice treated with FGL1-Fc. These immunological shifts confirm that FGL1 suppresses local T-cell activation within adipose depots and alleviates systemic neuroendocrine inflammatory signaling.
The study authors highlighted several critical constraints and translational boundaries that define their findings. A primary therapeutic limitation is that early FGL1 exposure robustly accelerated melanoma progression, meaning the molecule cannot serve as a frontline or preventative intervention while active antineoplastic therapy is underway. Furthermore, when the research team evaluated an independent murine model of cancer cachexia utilizing Lewis lung carcinoma cells, they detected no upregulation of Fgl1 expression, indicating that the activation of the FGL1-LAG-3 pathway represents a disease-specific mechanism that may be restricted to melanoma rather than a universal feature of cancer cachexia. The authors also noted that while LAG-3 is expressed on diverse immune and non-immune lineages, their study evaluated lymphocyte function exclusively within white adipose tissue. Consequently, clinical translation will require identifying precise molecular biomarkers that signal immunotherapy failure, defining the specific clinical window where targeting this pathway can mitigate wasting without compromising survival.
Subject of Research: Preclinical investigation of the FGL1-LAG-3 signaling axis in attenuating cancer-associated adipose and muscle wasting in mice
Article Title: The FGL1-LAG-3 axis attenuates melanoma-induced cachexia in mice
Article References: Liu, W., Wang, L., Jin, S., Liu, T., Qian, Y., & Lin, P. (2026). The FGL1-LAG-3 axis attenuates melanoma-induced cachexia in mice. Cancer & Metabolism, 14(1), Article 2. https://doi.org/10.1186/s40170-025-00418-x
Image Credits: AI Generated
DOI: 10.1186/s40170-025-00418-x
Keywords: Cancer cachexia, FGL1, LAG-3, Melanoma, B16F10 model, Adipose tissue wasting, Skeletal muscle atrophy, White adipose tissue, CD8+ T cells, Interleukin-6, Corticosterone, Fatty acid synthase, SCD1, Mustn1, Gastrocnemius muscle, Epididymal fat, Immunometabolism, Lipid metabolism
