Fgl-1 Emerges as an Oncogenic Driver Fueling Endometrial Cancer Through PI3K/AKT Signaling

Endometrial adenocarcinoma, one of the most prevalent malignancies of the female reproductive tract, has long been studied through the lens of hormonal and genetic risk factors, yet the molecular machinery that drives its progression remains incompletely mapped. A new study published in Medical Oncology now adds a striking piece to that puzzle, identifying fibrinogen-like protein 1, or Fgl-1, as a potent promoter of tumor growth and spread in this disease. The research, led by Wenjing Sun and colleagues at Shandong Provincial Hospital Affiliated to Shandong First Medical University, demonstrates that Fgl-1 is markedly overexpressed in endometrial adenocarcinoma tissues compared with normal endometrium, and that this overexpression fuels cancer cell survival, proliferation, migration and invasion through activation of the PI3K/AKT signaling pathway.

Fgl-1 has attracted growing attention in cancer biology in recent years, largely because of its dual identity. Originally characterized as a hepatokine, a secreted protein produced mainly by the liver with roles in metabolism and inflammation, it was later recognized as an emerging immune checkpoint ligand. When expressed on the surface of tumor cells, Fgl-1 can bind to lymphocyte activation gene 3, known as LAG-3, on T cells, thereby suppressing the immune response against the tumor. In hepatocellular carcinoma, Fgl-1 has been shown to promote the exhaustion of liver-resident memory T cells, helping the tumor evade immune surveillance. But the protein appears to be more than a decoy for immune cells. Prior work in gastric cancer linked Fgl-1 overexpression to invasion, metastasis and poor prognosis, while studies in metabolic disease connected circulating levels of the protein to insulin resistance and obesity. What remained unclear until now was its clinicopathological significance and oncogenic role in endometrial adenocarcinoma specifically.

To address this gap, the Shandong team first examined Fgl-1 expression in human tissue samples using immunohistochemistry, a staining technique that reveals where and how strongly a protein is produced in tissue sections. The results were unambiguous. Fgl-1 was significantly overexpressed in endometrial adenocarcinoma tissues relative to normal endometrial tissue, a difference that reached high statistical significance, and the level of expression correlated positively with tumor grade, meaning that more aggressive, less differentiated tumors tended to produce more of the protein. This grade association hints that Fgl-1 is not merely a passenger marker of malignant transformation but may actively participate in the biological escalation of the disease.

The investigators then turned to cell lines to probe function. Western blotting, which detects specific proteins in cell lysates, confirmed that Fgl-1 was abundantly produced in endometrial adenocarcinoma cell lines, with particularly high levels in two lines, HEC1B and KLE. These became the workhorses of the study. Using lentiviral vectors, short fragments of genetic material delivered by engineered viruses that silence a target gene, the researchers knocked down Fgl-1 expression by roughly 60 percent. The consequences were dramatic. With Fgl-1 suppressed, the cancer cells lost much of their malignancy in vitro: they became less viable, proliferated more slowly, formed fewer cell clones in colony-formation assays, migrated less effectively across scratched wound-healing cultures, and invaded less aggressively through extracellular-matrix-coated membranes.

To understand how a single secreted protein could exert such broad control over cancer cell behavior, the team examined the molecular circuits downstream of Fgl-1, focusing on two well-known hallmarks of malignant progression: the PI3K/AKT pathway and epithelial-mesenchymal transition. The PI3K/AKT cascade is one of the most frequently dysregulated signaling networks in human cancer, functioning as a central conduit for growth factor signals that promote cell survival, growth, metabolism and motility. When phosphoinositide 3-kinase is activated at the cell membrane, it recruits and activates AKT, a kinase that phosphorylates dozens of downstream targets, tipping the balance toward survival and proliferation while blocking programmed cell death. Western blot analysis in the study showed that silencing Fgl-1 inhibited PI3K/AKT signaling in KLE cells, providing direct evidence that Fgl-1 acts upstream of this pathway in endometrial cancer cells.

The second circuit, epithelial-mesenchymal transition, or EMT, is the process by which epithelial cancer cells shed their adhesive, stationary identity and acquire the motile, invasive characteristics of mesenchymal cells. EMT is orchestrated by transcription factors that repress epithelial markers such as E-cadherin and induce mesenchymal markers such as N-cadherin and vimentin, and it is a critical step in a tumor’s ability to invade surrounding tissue and seed metastases. By assessing EMT-associated proteins with Western blotting, the researchers found that suppressing Fgl-1 dampened EMT, explaining, at least in part, the reduced migration and invasion observed in the functional assays. Together, the data sketch a coherent mechanism: Fgl-1 overexpression activates PI3K/AKT signaling, which in turn drives EMT and the aggressive behaviors that accompany it.

The therapeutic implications are considerable, and they cut across two of the most active frontiers in oncology. First, because Fgl-1 functions as an immune checkpoint ligand through its interaction with LAG-3, it sits at the center of a rapidly expanding drug development effort. LAG-3 has emerged as a promising inhibitory immune checkpoint, and clinical trials of LAG-3 inhibitors, including studies combining agents such as ieramilimab with anti-PD-1 antibodies, are already underway in advanced malignancies. Immunotherapy approaches targeting PD-1 and PD-L1 have shown activity in endometrial cancer, and the field is actively searching for additional checkpoint axes that could extend these benefits to more patients. If Fgl-1 is both an immunosuppressive ligand and an intrinsically oncogenic driver in endometrial adenocarcinoma, blocking it could deliver a double blow: releasing the brakes on antitumor immunity while simultaneously strangling the PI3K/AKT-driven growth program inside the tumor cells themselves.

Second, the findings place Fgl-1 within a growing family of proteins that bridge inflammation, metabolism and cancer. Fibrinogen-like protein 1 has been implicated as a biomarker of disease activity in rheumatoid arthritis, as a contributor to T-cell exhaustion in liver cancer, and as a circulating hepatokine altered after bariatric surgery. This pleiotropy raises both opportunities and cautions. A protein that operates across so many physiological contexts may be a valuable drug target precisely because it sits at a hub of disease-relevant signaling, but systemic interference could carry metabolic or inflammatory consequences that will need careful evaluation. The new study does not address those questions directly, and its conclusions rest on correlation in tissue samples and experiments in cell culture rather than animal models or clinical intervention, so translating Fgl-1 blockade into a safe therapy remains a distant goal. Nonetheless, the demonstration that Fgl-1 suppression is sufficient to cripple key malignant behaviors in endometrial cancer cells provides a strong mechanistic rationale for pursuing such strategies.

For patients with endometrial adenocarcinoma, the study’s most immediate significance may lie in biomarker development. Because Fgl-1 expression correlates with tumor grade, it could potentially serve as a pathology-based indicator of aggressiveness, helping clinicians stratify risk and tailor surveillance intensity. The authors suggest that targeting the Fgl-1 pathway represents a promising therapeutic strategy for endometrial adenocarcinoma immunotherapy, and the convergence of their functional data with the broader clinical momentum behind LAG-3 blockade makes that suggestion more than wishful thinking. The research was supported by grants from the Science and Technology Development Program of Jinan, the Shandong Provincial Key Research and Development Program, and the Natural Science Foundation of Shandong Province, and it was conducted with ethics approval and informed consent from all tissue donors. As endometrial cancer incidence continues to rise in many parts of the world, driven in part by rising obesity rates, the discovery that a metabolic, immune-modulating, pro-oncogenic protein sits at the heart of the disease’s progression offers a timely and compelling new target for the next generation of treatments.

Subject of Research: The oncogenic role of fibrinogen-like protein 1 in endometrial adenocarcinoma progression via PI3K/AKT signaling

Article Title: Fgl-1 promotes the progression of endometrial adenocarcinoma through PI3K/AKT signal pathway

Article References: Fgl-1 promotes the progression of endometrial adenocarcinoma through PI3K/AKT signal pathway. (n.d.). https://doi.org/10.1007/s12032-026-03375-7

Image Credits: AI Generated

DOI: 10.1007/s12032-026-03375-7

Keywords: endometrial adenocarcinoma, Fgl-1, fibrinogen-like protein 1, PI3K/AKT signaling, epithelial-mesenchymal transition, immune checkpoint, LAG-3, cancer immunotherapy, tumor progression, oncogenic driver, cell invasion, biomarker