Mitochondrial Uncouplers Inhibit Oncogenic E2F1 Activity and Prostate Cancer Growth

2025-02-03 Mon
mitochondrial uncouplers oncogenic E2F1 prostate cancer ATP production AMPK pathway cell cycle targeted therapy
Research Report: Mitochondrial Uncouplers Inhibit E2F1 Activity and Prostate Cancer GrowthBackgroundProstate cancer (PC) is the most common cancer and the second leading cause of cancer-related deaths among men in the United States. In 2024, an estimated 299,010 American men will be diagnosed with prostate cancer, and 35,250 will die from the disease. Despite androgen deprivation therapy (ADT) being the mainstay treatment, many patients develop therapy resistance, leading to castration-resistant prostate cancer (CRPC). Approximately 20%-40% of patients exhibit innate resistance to existing therapies such as enzalutamide and abiraterone, while nearly all initially responsive patients eventually develop resistance.
CRPC progression and survival depend on adenosine triphosphate (ATP) to sustain rapid proliferation, making oxidative phosphorylation (oxphos)—a major source of ATP—a critical metabolic pathway. Mitochondrial uncouplers are known to disrupt oxphos and thus undermine cancer cell energy production. Additionally, the transcription factor E2F1 represents a critical oncogenic pathway in CRPC progression. This study explores the inhibitory effects of mitochondrial uncouplers on E2F1 activity and CRPC cell proliferation, providing a novel cancer treatment strategy.
SourceThis study, titled “Mitochondrial uncouplers inhibit oncogenic E2F1 activity and prostate cancer growth,” was led by Ohuod Hawsawi at the Georgia Cancer Center, Augusta University, and involved collaboration across multiple institutions. It was published in the Cell Reports Medicine journal on January 21, 2025, as an open-access article.
Study ProcessMethods and Experimental Design1. Development of Drug Screening SystemThe research team developed a unique bicistronic reporter platform, which used CRISPR-Cas9 gene-editing technology to insert a firefly luciferase gene (Fluc) downstream of the SKP2 gene’s stop codon. This allowed simultaneous expression with the endogenous SKP2 gene. This innovative method faithfully mimicked the dynamic responses of the SKP2 gene to chemical treatments.
Through high-throughput drug screening (9,298 compounds), the team identified eight molecules that significantly reduced SKP2 expression, with Malonoben (Mal) validated as a potent inhibitor of SKP2 expression.
2. Induction of Energetic Metabolic Disruption via UncouplingMal was confirmed to be a potent mitochondrial uncoupler that significantly reduced mitochondrial membrane potential and ATP yield by dissipating the mitochondrial inner membrane proton gradient. Additionally, other uncouplers, such as FCCP, Nitazoxanide (NTZ), and its active metabolite Tizoxanide (TIZ), effectively reduced SKP2 expression and inhibited CRPC cell proliferation.
3. Biochemical Characterization of TIZAs an FDA-approved anthelmintic drug, NTZ is widely used clinically for diarrhea caused by Cryptosporidium parvum and Giardia intestinalis. Its active metabolite TIZ exhibited significant uncoupling activity at clinically achievable, low-toxicity concentrations. TIZ triggered activation of AMPK (AMP-activated protein kinase) and P38 MAPK signaling pathways, leading to the degradation of the cell cycle regulator Cyclin D1.
4. Functional Validation In VitroFurther experiments validated that TIZ caused G1/S arrest and significantly inhibited DNA synthesis and de novo lipogenesis in CRPC cells. Using E2F1 knockout cell models, the study revealed that TIZ’s inhibitory effects on SKP2 and E2F1 target genes depend on downregulation of the E2F1 oncogenic pathway.
5. In Vivo StudiesThe anti-cancer effects of TIZ were tested in various animal models. In patient-derived Lucap23.1 xenografts and castrated CRPC mouse models, oral administration of NTZ markedly delayed tumor growth and decreased the expression of proliferation markers Ki-67 and SKP2 in tumor tissues.
Results1. Uncouplers Suppress E2F1 ActivityRNA sequencing (RNA-seq) analysis indicated that TIZ significantly downregulated transcription associated with E2F1, particularly genes involved in cell cycle progression (e.g., Cyclin E1, SKP2), DNA synthesis (e.g., MCM2, BRCA1), and lipid metabolism (e.g., FASN, SREBF1).
2. Mechanism of TIZ: AMPK-P38 Pathway ActivationThe study found that TIZ activated AMPK, which subsequently induced P38 phosphorylation, promoting Cyclin D1 phosphorylation at the T286 residue, leading to its proteasomal degradation.
3. Significant In Vivo Anti-Tumor EffectsOral NTZ administration showed no anomalies in the body weight of experimental animals, and histopathological examination revealed no abnormalities in key organs like the heart, liver, and kidney. These results suggest NTZ has excellent safety.
Significance and HighlightsTargeting the E2F1 Pathway: This study is the first to uncover the mechanism by which mitochondrial uncouplers inhibit E2F1 activity via the AMPK-P38 signaling axis.
Clinical Translational Potential: NTZ, as an FDA-approved drug, holds promise for rapid clinical adaptation in prostate cancer therapy, reducing drug development timelines.
Safety Advantages: Compared to traditional respiratory chain inhibitors, NTZ-induced metabolic disruption is milder and specific, avoiding extensive metabolic reprogramming that could lead to resistance.
ConclusionThis study establishes a theoretical basis for the use of mitochondrial uncouplers in CRPC treatment by elucidating their molecular mechanism of interfering with the E2F1 pathway. These findings present a novel therapeutic strategy against CRPC, warranting validation and optimization through further clinical trials.