The central player is propionyl-CoA, a molecule generated when cells break down certain branched-chain amino acids, particularly isoleucine and valine. These essential amino acids cannot be produced by the human body and are obtained through food, including meat, fish, dairy products and other protein-rich sources. Under normal conditions, propionyl-CoA is one intermediate in the metabolism of nutrients for energy and cellular construction. The Weill Cornell team found that, in prostate cancer, the molecule can also function as a signal that changes the behavior of a key regulatory protein.

The investigators began by examining human prostate tumors and discovered elevated levels of propionylcarnitine, a closely related metabolite that reflects propionyl-CoA activity. The metabolite was particularly abundant in more aggressive tumors, providing a clue that the pathway might be associated with disease progression. Further experiments in prostate cancer cells revealed that propionyl-CoA chemically modifies a protein called sterol regulatory element-binding protein 2, or SREBP2. This modification, known as propionylation, stabilizes SREBP2 and keeps it active for longer than it normally would be.

SREBP2 is a master regulator of cholesterol metabolism. In healthy cells, it operates as part of a feedback system: when cholesterol levels fall, SREBP2 enters the nucleus and activates genes involved in cholesterol synthesis and uptake. As cholesterol accumulates, the pathway is normally dampened, preventing excessive production. The new findings indicate that propionyl-CoA can interfere with this metabolic brake. By propionylating SREBP2, the cancer cell effectively keeps its cholesterol-making machinery switched on, even when internal cholesterol levels would ordinarily signal that production should stop.

That sustained cholesterol production may be especially valuable to prostate tumors because cholesterol is not merely a component of cell membranes. It can also serve as a precursor for steroid hormones, including androgens such as testosterone. Androgens activate the androgen receptor, a transcription factor that drives the expression of genes supporting prostate cancer growth and survival. Hormone therapies, including androgen-receptor inhibitors such as enzalutamide, are designed to disrupt this signaling system. However, if tumor cells increase their own supply of cholesterol and use it to generate additional male hormones, they may preserve enough androgen signaling to withstand treatment.

The researchers observed that propionyl-CoA levels increased when prostate cancer cells were deprived of male hormones in laboratory models. This suggests that hormone suppression itself may trigger the metabolic adaptation. Rather than simply becoming starved of a growth signal, the cancer cells appear capable of switching their nutrient-processing priorities, converting amino-acid breakdown into a route for restoring cholesterol and steroid production. The result is a feedback loop in which treatment-induced stress activates a pathway that helps rebuild the very hormonal environment therapy is intended to eliminate.

Experiments in mice provided additional evidence that this pathway can influence tumor behavior. Restricting isoleucine and valine slowed tumor growth and reduced the ability of prostate cancer cells to colonize the lungs. Conversely, increasing propionyl-CoA promoted tumor growth and enhanced lung colonization. These results do not establish that dietary manipulation can treat prostate cancer in people, but they suggest that nutrient availability may influence the metabolic flexibility that allows tumors to become more aggressive. The findings also point toward enzymes involved in converting isoleucine and valine into propionyl-CoA as possible drug targets.

The pathway could have implications beyond amino-acid metabolism. Because it ultimately drives cholesterol synthesis, it may help explain why studies of statins, cholesterol-lowering drugs, have produced mixed results in prostate cancer. If only a subset of tumors relies heavily on propionyl-CoA-driven SREBP2 activation, those tumors might be more vulnerable to interventions that block cholesterol production. Measuring metabolites such as propionylcarnitine, or assessing the activity of the associated enzymes and SREBP2 modification, could eventually help identify patients most likely to benefit from cholesterol-lowering strategies combined with hormone therapy.

The researchers caution that the biology is more complicated than simply removing two amino acids from the diet. Isoleucine and valine are required for normal protein synthesis and other physiological processes, while propionyl-CoA can arise from additional sources within the body. Aging, cancer-associated muscle wasting, obesity and diabetes can all alter amino-acid metabolism and circulating nutrient levels. Whether these systemic changes increase propionyl-CoA production inside human tumors remains unknown. Any dietary intervention would therefore require carefully controlled clinical studies to determine safety, nutritional consequences and whether it improves treatment responses.

The study underscores a growing view of cancer metabolism as a communication system rather than a passive source of energy. Nutrients and their breakdown products can act as molecular messages, changing gene regulation and helping malignant cells adapt to therapy. By connecting branched-chain amino acids to SREBP2, cholesterol production and androgen signaling, the Weill Cornell investigators have identified a potential explanation for how prostate tumors evade hormone deprivation. The next steps will be to test drugs that block the pathway, determine whether dietary strategies can safely influence it, and establish whether the mechanism operates in patients with treatment-resistant disease. If confirmed, a metabolic signal generated from ordinary nutrients could become a new vulnerability in one of the most persistent forms of cancer.

Subject of Research: Prostate cancer metabolism, hormone therapy resistance, branched-chain amino acids, propionyl-CoA, cholesterol synthesis and androgen signaling.

News Publication Date: 20-Aug-2026

Web References: https://mediasvc.eurekalert.org/Api/v1/Multimedia/5a01e294-78ba-4b60-93fd-2713d5b5ac91/Rendition/low-res/Content/Public; https://vivo.weill.cornell.edu/display/cwid-job2064; https://vivo.weill.cornell.edu/display/cwid-zhl4003

Image Credits: Zhongchi Li

Keywords: Prostate cancer, prostate tumors, hormone therapy, enzalutamide, androgen receptor, amino acid metabolism, isoleucine, valine, propionyl-CoA, propionylcarnitine, SREBP2, cholesterol metabolism, cancer metastasis, statins, metabolic therapy.

Prostate cancer remains the second most prevalent cancer among men worldwide, with treatment options becoming increasingly limited as the disease advances, especially in forms resistant to conventional hormone therapies. The current mainstay of treatment involves androgen deprivation therapy, which lowers testosterone levels to suppress tumor progression. Unfortunately, many patients develop castration-resistant prostate cancer (CRPC), wherein tumors continue to grow despite reduced androgen signaling. This new study offers hope by identifying an alternative molecular target that could circumvent this resistance.

Central to the research is the thyroid hormone triiodothyronine (T3), which exerts many of its physiological effects by binding to nuclear thyroid hormone receptors such as TRβ. While thyroid hormones are classically known for regulating metabolism, this study uncovers their unexpected influence on the proliferation of prostate cancer cells. In vitro experiments demonstrated that T3 activation induces a marked increase in prostate cancer cell numbers, implicating TRβ as a facilitator of tumor growth.

The research team employed NH-3, a specialized molecular inhibitor of TRβ, to study its effects on prostate cancer models. NH-3 effectively blocks the receptor’s ability to mediate thyroid hormone signals. When applied to cultured cancer cells, NH-3 significantly curtailed their proliferation, indicating that TRβ signaling is not just correlated with but actively contributes to cancer progression. This selective inhibition offers a promising avenue for targeting aggressive prostate tumors.

To extend their findings beyond cell cultures, the researchers conducted in vivo experiments using mouse models implanted with human prostate tumors. Administration of NH-3 led to a pronounced reduction in tumor size and slowed progression compared to untreated controls. These effects were especially prominent in models of castration-resistant disease, which mimic the clinical challenge faced by patients who no longer respond to testosterone-suppressing therapies.

Mechanistically, blocking TRβ disrupted the androgen receptor (AR) signaling cascade, which is ordinarily sustained by testosterone and pivotal for prostate cancer cell survival and growth. By impairing AR signaling through thyroid hormone receptor inhibition, NH-3 indirectly undermines a key growth axis in prostate cancer. This dual blockade strategy could be instrumental in overcoming therapy resistance inherent to advanced prostate cancer.

Supporting the experimental results, the team performed analyses on tissue samples from prostate cancer patients. Elevated levels of TRβ were observed in malignant tissue compared to healthy prostate samples, suggesting upregulation of this receptor is associated with tumorigenesis. Additionally, genetic studies revealed mutations affecting thyroid hormone signaling pathways in a substantial subset of these patients, underscoring the clinical relevance of targeting TRβ.

Despite the promise shown in preclinical models, researchers caution that therapeutically modulating thyroid hormone pathways must be approached with precision. Given the hormone’s systemic roles, unintended disruptions to thyroid function could generate adverse effects. Future investigations will need to define therapeutic windows and explore combinations with existing treatments to maximize efficacy while minimizing risk.

The identification of TRβ as a druggable target heralds a paradigm shift in prostate cancer research, offering a novel molecular foothold against tumors that evade current therapeutic regimens. Continued exploration of thyroid hormone receptor antagonists holds the potential to diversify the arsenal of prostate cancer treatments and improve patient outcomes in what remains a challenging disease landscape.

Beyond prostate cancer, these findings broaden our understanding of hormone-receptor cross-talk in cancer biology, revealing intricate networks that sustain malignancies. The intersection of thyroid hormone and androgen receptor signaling pathways provides new insight into cellular growth regulation and suggests that endocrine factors outside the traditional androgen axis may play pivotal roles in cancer progression.

As the scientific community digests these discoveries, ongoing clinical and translational efforts will be critical to translating them into viable treatments. The journey from bench to bedside, while complex, promises to enrich therapeutic methodologies for what has historically been a difficult-to-manage cancer.

This collaborative research effort exemplifies the power of international and interdisciplinary partnerships in uncovering novel oncological targets. By bridging molecular biology, pharmacology, and clinical oncology, such endeavors accelerate the pace of innovation and offer renewed hope for patients facing resistance to existing therapies.

In summary, the revelation that thyroid hormone receptor beta signaling acts as a critical promoter of prostate cancer growth introduces a new frontier in cancer therapeutics. The targeted inhibition of TRβ could become a key strategy in limiting tumor progression, particularly for cases unresponsive to conventional hormonal treatments, marking a significant step forward in personalized cancer care.

Subject of Research: Human tissue samples

Article Title: Thyroid hormone receptor beta signaling is a targetable driver of prostate cancer growth

News Publication Date: 14-Oct-2025

Web References: 10.1186/s12943-025-02451-2

Image Credits: Medizinische Universität Wien

Keywords: Thyroid hormone receptor beta, TRβ, prostate cancer, triiodothyronine, T3, castration-resistant prostate cancer, androgen receptor, NH-3 inhibitor, hormone signaling, tumor growth, molecular targeted therapy, cancer resistance