The study, led by Zhao, Meng, Zhou and colleagues, focuses on a phenomenon that has long frustrated oncologists: tumor dormancy. In many patients with prostate cancer, surgical removal of the prostate or radiation therapy eliminates the detectable tumor, yet microscopic pockets of cancer cells remain in the body. These residual cells can enter a state of deep quiescence, halting their division and effectively hiding from therapies such as chemotherapy and androgen-deprivation treatment, both of which preferentially kill rapidly proliferating cells. Years or even decades later, some of these dormant cells reactivate, seed new lesions, and give rise to incurable metastatic disease. Understanding how dormant cells stay alive during this hidden phase has therefore become one of the most important questions in cancer biology.

The new work identifies glutamine metabolism as a central pillar of that survival strategy. Glutamine is the most abundant amino acid in human blood and serves as a versatile nitrogen donor, a building block for proteins and nucleotides, and a substrate for producing energy and antioxidant molecules. Although many cancer cells are famous for consuming glutamine at enormous rates—a hallmark known as glutamine addiction—the researchers found that dormant prostate cancer cells face the opposite problem. In their quiescent state, with limited access to external nutrients and diminished uptake from the tumor microenvironment, these cells rely on their own internal glutamine production to meet essential metabolic demands.

At the heart of this adaptation is glutamine synthetase, the enzyme that converts glutamate and ammonia into glutamine. The study shows that dormant tumor cells upregulate this synthetic pathway, essentially running the glutamine reaction in reverse compared with the consumption-oriented metabolism of aggressive, proliferating tumors. By manufacturing glutamine internally, the dormant cells maintain nitrogen balance, buffer toxic ammonia that accumulates in their environment, and sustain the synthesis of molecules needed for basic cellular upkeep. When the researchers interfered with this pathway, dormant cells lost their protective capacity: survival during dormancy declined, and the population of cells capable of later reawakening shrank dramatically.

The team used experimental models of prostate cancer designed to capture the biology of tumor dormancy and recurrence. By manipulating the expression of components of the glutamine synthesis pathway and tracking cell fate over time, they were able to link the metabolic program to both phases of the dormancy life cycle. Cells with active glutamine synthesis not only survived longer in a dormant state but also retained the ability to exit quiescence and re-enter the cell cycle, re-establishing proliferative tumors. In other words, the same metabolic adaptation that keeps dormant cells alive also appears to preserve their future potential to relapse.

A particularly striking aspect of the findings is the role of ammonia detoxification. Ammonia is generated continuously by cellular metabolism and, at high concentrations, is poisonous to cells. Proliferating tumors often export waste and draw on abundant blood-borne nutrients, but dormant micrometastases may sit in nutrient-poor niches where waste disposal is inefficient. Glutamine synthetase offers an elegant solution by incorporating ammonia directly into glutamine, converting a toxic byproduct into a usable metabolite. The study suggests that dormant prostate cancer cells exploit this reaction as both a detoxification mechanism and a nitrogen-recycling system, enabling long-term persistence in metabolically hostile territory.

The implications for prostate cancer treatment are considerable. Current adjuvant therapies aim primarily at killing dividing cells or blocking androgen receptor signaling, the main growth engine of prostate adenocarcinoma. Dormant cells, by definition, escape such approaches because they are not dividing and their signaling dependencies differ from those of active tumors. The new results suggest that targeting glutamine synthetase or related metabolic enzymes could specifically undermine the survival machinery of dormant cells, offering a strategy to prevent recurrence rather than simply treat it after the fact. In principle, a drug that disables the glutamine synthesis pathway could be administered after primary treatment to eliminate residual dormant disease before it has the chance to reawaken.

The research also adds to a growing appreciation of metabolic flexibility as a defining feature of cancer progression. Tumors are not metabolically static; they rewire their biochemistry in response to nutrient availability, oxygen levels, and therapeutic pressure. The shift from glutamine consumption to glutamine synthesis observed in this study illustrates how tumor cells can adopt nearly opposite metabolic strategies at different stages of their life cycle. This plasticity complicates the interpretation of imaging and biomarkers that assume uniform tumor metabolism, but it also opens new therapeutic windows, because enzymes that are dispensable in normal proliferating tissues may become vulnerabilities in dormant disease.

Questions remain before these findings can be translated into the clinic. The researchers’ experiments establish a causal role for the glutamine synthesis pathway in models of dormancy and recurrence, but the biology of human prostate cancer dormancy is likely to involve additional metabolic pathways, immune interactions, and niche-specific signals. Glutamine synthetase is also active in normal tissues such as the liver and brain, raising the challenge of achieving therapeutic selectivity. Nonetheless, the identification of a druggable metabolic node that supports dormant cell survival gives researchers a concrete target and a rationale for developing combination strategies that pair androgen-deprivation therapy with anti-metabolic agents.

The broader message of the study is that cancer recurrence is not a random event but the outcome of a programmed survival state with its own biochemical requirements. By revealing that dormant prostate cancer cells depend on making their own glutamine, the work reframes recurrence as a preventable metabolic process. If follow-up studies confirm these mechanisms in patients and lead to effective inhibitors of the dormant-cell survival program, the long tail of prostate cancer relapse could one day be shortened—or cut off entirely.

The finding matters because prostate tumors are unusually dependent on cholesterol metabolism. Cholesterol is not simply a circulating substance associated with cardiovascular disease; inside a rapidly dividing cancer cell, it serves as a structural component of new membranes and as a precursor for steroid hormones. Prostate cancer cells can synthesize cholesterol internally, import it from the surrounding environment or store it in esterified form for later use. These processes are tightly controlled in healthy tissue, but malignant cells often reprogram them to sustain continuous growth. The new study places propionyl-CoA at an important point in that reprogramming. Produced when isoleucine and valine are broken down, propionyl-CoA normally enters pathways involved in energy production and carbon metabolism. In prostate cancer, however, the researchers’ findings indicate that it can influence the expression or activity of cholesterol-related machinery, effectively linking the availability of specific nutrients to the tumor’s capacity to manufacture and manage lipids.

This is a striking example of metabolic flexibility, the ability of cancer cells to change their preferred fuel sources as conditions shift. Tumors exist in environments where oxygen, glucose and other nutrients may fluctuate, so successful cancer cells frequently build alternative routes for obtaining energy and raw materials. Branched-chain amino acids are especially interesting because they are abundant in the diet and participate in several layers of metabolism. After uptake into cells, isoleucine and valine are converted through a series of enzymatic reactions that remove their amino groups and produce acyl-CoA intermediates. Among those intermediates is propionyl-CoA, which can be further processed through pathways connected to the tricarboxylic acid cycle. The study suggests that, in prostate cancer, propionyl-CoA is not merely burned for energy. Instead, it acts as a metabolic signal or substrate that helps push cholesterol metabolism toward a state favorable to tumor expansion.

The mechanism could help explain why nutrient availability sometimes has effects that are invisible when researchers examine only individual metabolites. A metabolite such as propionyl-CoA can influence cells in several ways at once. It may provide carbon for downstream reactions, alter the balance of competing metabolic pathways or affect protein regulation through chemical modifications. Propionyl-CoA is also related to propionylation, a form of lysine acylation that can modify proteins, including proteins associated with gene control. Such modifications have the potential to change the activity of transcriptional programs without altering the underlying DNA sequence. In the context of prostate cancer, this may help activate genes that support cholesterol synthesis, uptake, transport or storage. The paper’s central message is therefore broader than the effect of two amino acids: it reveals how a nutrient-derived CoA metabolite can connect carbon flow to the regulatory systems that determine whether a cancer cell accumulates the lipids needed for proliferation.

The cholesterol connection is particularly relevant to prostate biology because many prostate tumors remain responsive to androgen signaling, even after treatment. Androgens and other steroid hormones are synthesized from cholesterol-derived precursors, while cholesterol itself supports the organization of cell membranes and signaling platforms. Cancer cells can exploit this relationship by increasing cholesterol production or storage, strengthening pathways that maintain growth signals under therapeutic pressure. The study’s findings suggest that isoleucine and valine may reinforce this metabolic environment by increasing propionyl-CoA-dependent cholesterol activity. That does not mean that eating a single food immediately causes prostate cancer, nor does it establish that eliminating these amino acids from the diet would be safe or effective. Isoleucine and valine are essential nutrients involved in normal muscle maintenance, immune function and tissue repair. The significance lies in how malignant cells use them, not in treating the amino acids as inherently harmful.

The research also raises questions about the relationship between systemic nutrition and the tumor microenvironment. Blood concentrations of nutrients are influenced by diet, exercise, liver and muscle metabolism, kidney function and the overall state of health. Inside a tumor, however, nutrient concentrations can differ substantially from those in circulation. Cancer-associated fibroblasts, immune cells and blood vessels all contribute to the local chemical environment, and metabolites can move between these cell populations. If prostate cancer cells are particularly efficient at converting branched-chain amino acids into propionyl-CoA, they may gain a competitive advantage when those nutrients are available. Conversely, metabolic stress could force tumors to rely more heavily on alternative pathways. Mapping this exchange will be important, because the consequences of nutrient metabolism cannot be understood by studying cancer cells in isolation from the tissues around them.

From a therapeutic perspective, the pathway offers several possible intervention points. Researchers might investigate enzymes that break down isoleucine and valine, proteins that generate or consume propionyl-CoA, and the cholesterol-synthesis or cholesterol-transport systems influenced by the metabolite. Drugs that block cholesterol production already exist, and other treatments target androgen signaling or lipid storage. Combining such approaches with inhibitors of branched-chain amino-acid metabolism could, in principle, deprive prostate cancer cells of both the signal and the raw materials needed to maintain their cholesterol program. But the risks are substantial. The same metabolic enzymes operate in healthy organs, especially skeletal muscle, liver and heart, and broad inhibition could cause toxicity or interfere with normal energy balance. Any treatment strategy would therefore need to distinguish cancer-specific metabolic dependencies from the essential functions of these nutrients throughout the body.

The study points toward a future in which cancer metabolism is analyzed with far greater precision than the familiar labels of “sugar-burning” or “fat-burning.” A tumor may use glucose for one purpose, amino acids for another and lipids for a third, while constantly redirecting intermediates among these networks. In prostate cancer, the isoleucine–valine–propionyl-CoA axis may represent one of those hidden connections, allowing dietary nutrients to influence the production and handling of cholesterol. The next steps will be to determine how broadly this mechanism operates across prostate cancer subtypes, whether it changes during treatment or metastasis, and whether patients with distinct metabolic profiles respond differently to interventions aimed at it. For now, the work delivers a vivid biological warning against simplistic nutritional conclusions: the question is not merely what a cancer patient eats, but how a tumor rewires the chemistry of those nutrients to support its own survival.

Subject of Research: Isoleucine- and valine-driven metabolic regulation of cholesterol metabolism and prostate cancer progression

Article Title: Isoleucine and valine promote prostate cancer progression via propionyl-CoA-mediated cholesterol metabolism

Article References: Li, Z., Liu, S., Jin, W. et al. Isoleucine and valine promote prostate cancer progression via propionyl-CoA-mediated cholesterol metabolism. Nature Metabolism 8, 1772–1790 (2026). https://doi.org/10.1038/s42255-026-01583-z

Image Credits: AI Generated

DOI: 10.1038/s42255-026-01583-z

Keywords: prostate cancer, isoleucine, valine, branched-chain amino acids, propionyl-CoA, cholesterol metabolism, cancer metabolism, tumor progression, lipid metabolism, precision oncology