EZH2–SREBP2 Pathway Drives Cholesterol Production, Revealing a Noncanonical Cancer Vulnerability

Cancer cells may be exploiting a hidden partnership between gene regulation and cholesterol production, according to a study that identifies an unexpected molecular route supporting tumour growth. Researchers report that EZH2, a protein frequently overproduced in cancer, works together with SREBP2, a master regulator of lipid metabolism, to activate genes in the mevalonate pathway—the biochemical network that produces cholesterol and related molecules. The finding gives EZH2 a role beyond its traditionally recognized function in controlling chromatin and gene silencing. It also suggests that tumours may depend on a previously overlooked connection between epigenetic regulation and metabolic reprogramming. The study, published in Nature Cell Biology, describes an EZH2–SREBP2 axis that increases cholesterol biosynthesis and helps sustain tumorigenesis. Because EZH2 is already considered an important cancer target, the newly described mechanism could offer a way to attack malignant cells by disrupting not only the protein itself but also the metabolic programme it helps activate.

EZH2, short for enhancer of zeste homolog 2, is best known as a catalytic component of the Polycomb Repressive Complex 2, or PRC2. In that classical role, EZH2 adds methyl groups to histone H3 at lysine 27, a chemical modification commonly designated H3K27me3. Histones are proteins around which DNA is wrapped, and chemical marks on them can influence whether nearby genes are accessible for transcription. EZH2 is often overexpressed or abnormally activated in cancers, where it has generally been associated with the repression of genes that restrain cell proliferation or promote differentiation. Patients whose tumours contain high levels of EZH2 frequently have poorer clinical outcomes. Yet the exact ways in which excess EZH2 strengthens tumour-forming ability have not been fully explained. The new work expands that picture by showing that EZH2 can participate in a noncanonical, or nontraditional, function: rather than acting only as a chromatin-modifying repressor, it helps stimulate a gene-expression programme connected to lipid metabolism.

The key partner in this process is SREBP2, or sterol regulatory element-binding protein 2. SREBP2 is a transcription factor that monitors and controls cellular cholesterol production. When cells require more cholesterol, SREBP2 can become activated and move into the nucleus, where it binds regulatory DNA sequences near genes involved in cholesterol uptake and synthesis. Among its major targets are genes in the mevalonate pathway, a series of enzymatic reactions that converts acetyl-CoA into cholesterol and other sterol-related products. Cholesterol is not merely a structural component of cell membranes. It also contributes to membrane organization, intracellular signalling and the production of steroid-related molecules. Rapidly dividing cancer cells can place unusually high demands on these systems as they build new membranes and adapt to stressful environments. The study indicates that EZH2 and SREBP2 cooperate to drive high expression of mevalonate-pathway genes, effectively linking an epigenetic cancer-associated protein to a metabolic switch that can increase the supply of cholesterol.

The researchers describe a direct molecular connection between the two proteins and the transcriptional machinery that activates cancer-related genes. According to the study, transcriptional activation domains within EZH2 and SREBP2 bind directly to p300, a well-known coactivator that helps turn genes on. p300 can modify histones and other proteins through acetylation, a process that often promotes a more transcriptionally permissive chromatin environment. In this model, the EZH2–SREBP2 partnership is not simply bringing two regulatory proteins into proximity; it is also recruiting a coactivator capable of strengthening gene activation. The result is a functional complex that supports expression of genes in the mevalonate pathway and activates proto-oncogene programmes. Proto-oncogenes normally contribute to controlled growth and survival, but when inappropriately activated they can promote malignant transformation. This mechanism provides a possible explanation for how high EZH2 levels can support cancer even when its tumour-promoting activity does not fit the classic PRC2-mediated model of gene repression.

The implications are especially striking because cholesterol metabolism has often been viewed as a supporting feature of cancer biology rather than as a central output of EZH2 activity. Tumours rewire metabolism to obtain energy, construct cellular components and survive conditions such as nutrient limitation or low oxygen. Increased cholesterol synthesis may help supply the membrane material required for proliferation, while mevalonate-pathway intermediates can influence signalling and protein modification. The study’s findings place EZH2 near the top of that metabolic control system, where it may help SREBP2 maintain the expression of multiple biosynthetic genes at once. This is different from blocking a single enzyme downstream in the pathway. A regulatory partnership that controls a broad gene set could, in principle, produce a larger effect on tumour biology—but it could also create challenges, because cholesterol production is essential to normal cells. The research therefore points to a vulnerability, not yet a finished treatment strategy, and further work would be needed to determine how selectively the pathway can be disrupted in cancer.

To test whether this noncanonical function could be targeted, the researchers used proteolysis-targeting chimeras, widely known as PROTACs. These are engineered molecules designed to bring a target protein into contact with an E3 ubiquitin ligase, part of the cell’s protein-disposal system. Once recruited, the target can be tagged with ubiquitin and sent to the proteasome, a large molecular machine that breaks down proteins. Unlike conventional inhibitors, which generally occupy a functional pocket and block activity, PROTACs can remove a protein from the cell and may continue acting catalytically as long as the degradation machinery remains available. In the study, independent EZH2-targeting PROTACs degraded EZH2 and, notably, also reduced SREBP2. This dual effect suppressed SREBP2-associated gene-expression programmes, including those linked to cholesterol biosynthesis, and inhibited tumour growth. The result suggests that eliminating EZH2 may dismantle the regulatory partnership more effectively than simply blocking one of its biochemical activities.

The observation that EZH2-targeting PROTACs affect both proteins is central to the study’s therapeutic significance. If EZH2 supports tumour growth through several distinct functions, an agent that removes the protein could potentially block more than a single catalytic activity. Degradation of EZH2 may weaken its association with SREBP2, reduce the availability of the coactivator p300 at relevant genes and collapse the transcriptional programme that sustains the mevalonate pathway. The accompanying loss of SREBP2 would further limit the cell’s ability to activate cholesterol-biosynthesis genes. Together, these effects could explain why the PROTAC strategy inhibited tumour growth in the researchers’ experiments. However, the findings do not establish that such compounds are ready for clinical use, nor do they show that every cancer with high EZH2 depends on the same mechanism. Tumours are genetically and metabolically diverse, and cholesterol production is also vital in healthy tissues. The future challenge will be identifying cancers most reliant on the EZH2–SREBP2 axis while minimizing damage to normal metabolism.

The work ultimately shifts the way scientists may think about EZH2 in cancer. Rather than treating the protein solely as an epigenetic repressor that silences protective genes, the study presents it as a versatile regulator capable of joining a transcriptional complex that actively promotes metabolic and oncogenic programmes. Its partnership with SREBP2 creates a bridge between chromatin biology, gene activation and lipid metabolism, revealing how a cancer-associated protein can influence the supply of molecules needed for tumour expansion. The findings also illustrate why protein degradation strategies are attracting attention: destroying a regulatory protein can expose vulnerabilities created by its interactions, not just those associated with its best-known enzymatic function. By identifying cholesterol biosynthesis as a downstream output of EZH2–SREBP2 cooperation, the researchers offer a new framework for understanding tumour metabolism and a potential route for therapeutic development. The axis is not yet a proven universal weakness, but it may represent a molecular Achilles’ heel in cancers that depend on elevated EZH2 activity and SREBP2-driven cholesterol production.