Flavonoid Diosmetin Targets Endothelial Enzyme to Rewire Lung Cancer Immune Defenses

Lung adenocarcinoma, the most common form of lung cancer worldwide, has long been treated as a disease of malignant epithelial cells. Yet a growing body of evidence points to another, less obvious accomplice: the blood vessels that thread through the tumor. Far from being passive plumbing, the tumor endothelium actively builds a fortress around the cancer, secreting molecules that suppress immune cells while feeding the tumor with a fresh blood supply. A new study published in Cancer Immunology, Immunotherapy now identifies a specific molecular switch inside these vessel-lining cells that appears to hold the key to dismantling that fortress, and shows that a humble plant-derived flavonoid may be able to flip it.

The research, led by Dong Cui of Henan Provincial Chest Hospital in Zhengzhou together with colleagues at Shanghai Pulmonary Hospital and Tongji University School of Medicine, centers on CYP3A5, an enzyme belonging to the cytochrome P450 family. Cytochrome P450 enzymes are best known for metabolizing drugs in the liver, but in recent years they have emerged as regulators of endothelial cell behavior within tumors. What remained unexplored until now was whether endothelial CYP3A5 plays a role in shaping the immune landscape of lung adenocarcinoma, and whether it could serve as a druggable target for therapies designed to reawaken the immune system against the cancer.

To answer that question, the team deployed an unusually broad methodological arsenal. They began with bioinformatic screening across large public datasets, including The Cancer Genome Atlas and the Genotype-Tissue Expression project, to pinpoint candidate endothelial targets in lung adenocarcinoma. They then layered on single-cell RNA sequencing and spatial transcriptomics, technologies that allow researchers to see which genes are active in individual cells and where those cells sit within the tumor architecture. This dual lens revealed that CYP3A5 is predominantly expressed in the endothelial cells of minimally invasive lung adenocarcinoma, an early stage of the disease, positioning the enzyme at a critical juncture in tumor evolution.

Having identified CYP3A5 as a candidate, the researchers asked what controls it. Through molecular docking, chromatin immunoprecipitation followed by quantitative PCR, DNA pulldown assays, and luciferase reporter experiments, they demonstrated that the transcription factor GATA6 sits upstream of CYP3A5, regulating its expression in endothelial cells. This established what the authors describe as a novel GATA6/CYP3A5/VEGF axis in the tumor-associated endothelium, a signaling cascade that links a nuclear regulator to an enzyme and ultimately to vascular endothelial growth factor, one of the most potent drivers of angiogenesis and immune suppression in cancer.

The single-cell and spatial analyses added another crucial piece to the puzzle: an enrichment of VEGFA–FLT1 signaling between the epithelial cancer cells and the endothelial compartment. This ligand-receptor conversation between tumor and vessel is a hallmark of the tumor microenvironment’s immunosuppressive wiring. Vascular endothelial growth factor is well known to inhibit T cell function and to promote the infiltration of regulatory T cells, the immune system’s own brakes. By mapping this axis with cellular resolution, the study clarified exactly where a therapeutic intervention could intervene to break the circuit.

Enter diosmetin, a natural flavonoid found in citrus fruits and certain medicinal herbs, which has previously shown anti-tumor properties but whose mechanism of action remained murky. The team’s bioinformatic screen flagged CYP3A5 as a functional target associated with diosmetin response. When the researchers tested this experimentally, they found something subtle and important: diosmetin inhibited the enzymatic activity of CYP3A5 without significantly altering the amount of the enzyme the cells produced. In other words, the flavonoid appears to act on the function of the enzyme rather than its abundance, suggesting that CYP3A5 may serve as a functional mediator of diosmetin’s activity in lung adenocarcinoma. The authors are careful to note that further biochemical studies will be required to confirm a direct physical interaction between diosmetin and CYP3A5, a caveat that reflects the rigor of the work.

The functional consequences of this intervention were striking. When endothelial cells were treated with diosmetin and then co-cultured with lung adenocarcinoma cells, the cancer cells lost much of their capacity to proliferate, migrate, and invade, the three behaviors that make tumors deadly. Enzyme-linked immunosorbent assays and Western blotting revealed that the treated endothelial cells also secreted fewer immunosuppressive cytokines, the chemical signals that tell patrolling immune cells to stand down. The tumor-vessel dialogue, in essence, was being rewritten from a conversation that protects the cancer into one that exposes it.

The story held up in living systems. In a xenograft model, diosmetin suppressed tumor growth and angiogenesis, and the treated tumors showed a measurable shift in their immune microenvironment. Because vascular endothelial growth factor is known to disable T cells and recruit regulatory T cells, the authors argue that suppressing endothelial CYP3A5 activity and the VEGF production it drives effectively disrupts an immune-evasive circuit. The dual action is what makes the finding conceptually exciting: a single intervention aimed at an endothelial enzyme simultaneously starves the tumor of new blood vessels and strips away one of its principal shields against immune attack. The researchers do acknowledge an important limitation, however, noting that further studies are needed to validate the immune-related effects in immune-competent models, since xenografts cannot fully recapitulate a functioning immune system.

The translational implications are considerable. Anti-VEGF therapies such as bevacizumab are already part of the standard arsenal against lung cancer, but they come with vascular toxicities and resistance mechanisms. Targeting CYP3A5 enzymatic activity upstream of VEGF offers a different point of entry into the same pathway, one that could theoretically complement existing angiogenesis inhibitors and immune checkpoint blockade. The fact that CYP3A5 expression was most prominent in minimally invasive adenocarcinoma also raises the intriguing possibility of early intervention, a window in which remodeling the endothelial microenvironment might prevent progression to fully invasive disease. And because diosmetin is a dietary flavonoid with a long history of human exposure, it provides a chemical starting point that is already amenable to medicinal chemistry optimization.

None of this means a diosmetin-based drug will reach patients tomorrow. The study is an early, mechanistic proof of concept, built on cell culture, omics data, and xenografts, and the authors themselves flag the need for direct binding studies and immune-competent validation. But the work does something scientifically valuable: it elevates an overlooked endothelial enzyme into a candidate vulnerability, connects it to a master transcriptional regulator, and traces a complete path from GATA6 through CYP3A5 to VEGF and the immunosuppressive microenvironment it creates. In doing so, it reframes the tumor vasculature not merely as a target for blood supply blockade but as an active immune gatekeeper whose enzymatic machinery can, in principle, be turned against the cancer it serves.

Subject of Research: Targeting endothelial CYP3A5 to remodel the immunosuppressive tumor microenvironment in lung adenocarcinoma

Article Title: Targeting endothelial CYP3A5 in lung adenocarcinoma remodels the immunosuppressive microenvironment via VEGF inhibition: Mechanistic insights from Diosmetin

Article References: Cui, D., Yang, Y., Chen, M., Feng, Y., Zhang, W., Zhou, X., & Qiu, R. (2026). Targeting endothelial CYP3A5 in lung adenocarcinoma remodels the immunosuppressive microenvironment via VEGF inhibition: Mechanistic insights from Diosmetin. Cancer Immunology, Immunotherapy. https://doi.org/10.1007/s00262-026-04538-1

Image Credits: AI Generated

DOI: 10.1007/s00262-026-04538-1

Keywords: CYP3A5, lung adenocarcinoma, diosmetin, tumor endothelium, VEGF, immunosuppressive microenvironment, GATA6, angiogenesis, cytochrome P450, tumor microenvironment, cancer immunotherapy, flavonoid