Molecular Metabolism

Acetate drives ovarian cancer quiescence via ACSS2-mediated acetyl-CoA production

Quiescence is a reversible cell cycle exit traditionally thought to be associated with a metabolically inactive state. Recent work in muscle cells indicates that metabolic reprogramming is associated with quiescence. Whether metabolic changes occur in cancer to drive quiescence is unclear. Using a multi-omics approach, we found that the metabolic enzyme ACSS2, which converts acetate into acetyl-CoA, is both highly upregulated in quiescent ovarian cancer cells and required for their survival. Indeed, quiescent ovarian cancer cells have increased levels of acetate-derived acetyl-CoA, confirming increased ACSS2 activity in these cells. Furthermore, either inducing ACSS2 expression or supplementing cells with acetate was sufficient to induce a reversible quiescent cell cycle exit. RNA-Seq of acetate treated cells confirmed negative enrichment in multiple cell cycle pathways as well as enrichment of genes in a published G0 gene signature. Finally, analysis of patient data showed that ACSS2 expression is upregulated in tumor cells from ascites, which are thought to be more quiescent, compared to matched primary tumors. Additionally, high ACSS2 expression is associated with platinum resistance and worse outcomes. Together, this study points to a previously unrecognized ACSS2-mediated metabolic reprogramming that drives quiescence in ovarian cancer. As chemotherapies to treat ovarian cancer, such as platinum, have increased efficacy in highly proliferative cells, our data give rise to the intriguing question that metabolically-driven quiescence may affect therapeutic response.

DIO3 depletion attenuates ovarian cancer growth via reduced glycolysis and alterations in glutamine metabolism

Metabolic reprogramming emerges as a central driver of therapy resistance and survival disadvantage in ovarian cancer. We recently demonstrated that inhibiting the enzyme Deiodinase type 3 (DIO3) reduces ovarian cancer growth, although the underlying mechanism remains unclear. We studied DIO3 role in metabolism in genetically manipulated ovarian cancer cells using protein expression analysis, integrative proteomics, endogenous and extracellular metabolomics, metabolic assays including lactate and glutamate secretion, reactive oxygen species (ROS) production and the Seahorse Cell Mito Stress test. We reveled that inhibiting DIO3 suppresses glycolysis while enhancing ATP production through oxidative phosphorylation (OXPHOS). We corroborated these findings using two models of ovarian cancer xenografts, demonstrating a marked reduction in glycolytic proteins upon silencing or inhibiting DIO3 using our first in class small molecule. Moreover, altered glutamine metabolism was also documented, favoring urea cycle and TCA cycle engagement over antioxidant production, accompanied by elevated ROS. Intriguingly, DIO3 depletion in fallopian tube cells, the precursor of HGSOC, displayed distinct metabolic adaptations, including enhanced glycolysis and lipid metabolism, suggesting tissue-specific roles for DIO3. These collective findings position DIO3 as a potential regulator of ovarian cancer metabolism, with implications for targeting this enzyme to disrupt tumor energetics as a novel therapeutic approach.

Therapeutic management of PI3Kα inhibitor-induced hyperglycemia with a novel glucokinase activator: Advancing the Frontier of PI3Kα inhibitor therapy

The phosphatidylinositol 3-kinase (PI3K) signaling pathway is a pivotal target in cancer treatment, driving substantial investigation into PI3K inhibitors (PI3Ki). However, the common on-target adverse effect of hyperglycemia presents a substantial challenge to their clinical application. There is an urgent need to discover an anti-hyperglycemic agent that maintains the efficacy of PI3Ki. We conducted a comprehensive study to explore the interaction between exogenous hyperinsulinemia and PI3Ki in SKOV3 and OVCAR3 ovarian cancer cell lines. We used Western blotting, CCK-8, and EdU assays to determine the effect of this interaction on cell proliferation. In addition, we evaluated the anti-hyperglycemic effects of dorzagliatin in a PI3Ki-induced hyperglycemic mice model. Cell line-derived xenograft (CDX) models were employed to evaluate the in vivo tumor growth inhibitory effects of combining dorzagliatin with PI3Ki. Western blot analysis demonstrated that insulin activated the AKT/INSR/mTOR pathway, reversing PI3Ki-induced p-AKT inhibition. Insulin also attenuated the anti-proliferative effects of PI3Ki. In the hyperglycemic mouse model, dorzagliatin significantly reduced blood glucose levels compared to controls. The combination therapy group (Dorzagliatin + PI3Ki) in CDX models showed a marked reduction in tumor volume. Dorzagliatin not only mitigated hyperglycemia but also enhanced the anti-tumor effects of PI3Ki. A clinical trial (NCT06117566) in cervical cancer patients supported these findings, showing that dorzagliatin stabilized blood glucose levels, facilitated body weight recovery, and achieved a confirmed partial response (PR). Dorzagliatin shows promise for managing PI3Ki-associated hyperglycemia, thereby enhancing its therapeutic efficacy. The activation of liver glycogen kinase and insulin regulation may be key mechanisms underlying its therapeutic benefits.

Loss of mitochondrial pyruvate carrier 1 supports proline-dependent proliferation and collagen biosynthesis in ovarian cancer

The pyruvate transporter MPC1 (mitochondrial pyruvate carrier 1) acts as a tumour-suppressor, loss of which correlates with a pro-tumorigenic phenotype and poor survival in several tumour types. In high-grade serous ovarian cancers (HGSOC), patients display copy number loss of MPC1 in around 78% of cases and reduced MPC1 mRNA expression. To explore the metabolic effect of reduced expression, we demonstrate that depleting MPC1 in HGSOC cell lines drives expression of key proline biosynthetic genes; PYCR1, PYCR2 and PYCR3, and biosynthesis of proline. We show that altered proline metabolism underpins cancer cell proliferation, reactive oxygen species (ROS) production, and type I and type VI collagen formation in ovarian cancer cells. Furthermore, exploring The Cancer Genome Atlas, we discovered the PYCR3 isozyme to be highly expressed in a third of HGSOC patients, which was associated with more aggressive disease and diagnosis at a younger age. Taken together, our study highlights that targeting proline metabolism is a potential therapeutic avenue for the treatment of HGSOC.

Ovarian cancer modulates the immunosuppressive function of CD11b+Gr1+ myeloid cells via glutamine metabolism

Immature CD11b All studies were performed using the intraperitoneal ID8 syngeneic epithelial ovarian cancer mouse model. Myeloid cell depletion and immunotherapy were carried out using anti-Gr1 mAb, gemcitabine treatments, and/or anti-PD1 mAb. The treatment effect was assessed by a survival curve, in situ luciferase-guided imaging, and histopathologic evaluation. Adoptive transfer assays were carried out between congenic CD45.2 and CD45.1 mice. Immune surface and intracellular markers were assessed by flow cytometry. ELISA, western blot, and RT-PCR techniques were employed to assess the protein and RNA expression of various markers. Bone marrow-derived myeloid cells were used for ex-vivo studies. The depletion of Gr1 Our study shows that the ovarian cancer microenvironment can regulate the metabolism and function of immunosuppressive CD11b

Mitochondrial-targeted plastoquinone therapy prevents early onset muscle weakness that occurs before atrophy during ovarian cancer

Muscle loss with cancer causes weakness, worsens quality of life, and predicts reduced overall survival rates. Recently, muscle weakness was identified during early-stage cancer before atrophy develops. This discovery indicates that mechanisms independent of muscle loss must contribute to progressive weakness. While mitochondrial stress responses are associated with early-stage 'pre-cachexia' weakness, a causal relationship has not been established. Here, using a mouse model of metastatic ovarian cancer cachexia, we identified that the well-established mitochondrial-targeted plastoquinone SkQ1 partially prevents muscle weakness occurring before the development of atrophy in the diaphragm. Furthermore, SkQ1 improved force production during atrophy without preventing atrophy itself in the tibialis anterior and diaphragm. These findings indicate that atrophy-independent mechanisms of muscle weakness occur in different muscle types throughout ovarian cancer. Ovarian cancer reduced flexor digitorum brevis (FDB) whole muscle force production and myoplasmic free calcium ([Ca These discoveries identify that muscle weakness can occur independent of atrophy throughout ovarian cancer in a manner that is linked to improved calcium handling. The findings also demonstrate that mitochondrial-targeted therapies exert a robust effect in preserving muscle force early during ovarian cancer during the pre-atrophy period and in late stages once cachexia has become severe.

Muscle weakness and mitochondrial stress occur before severe metastasis in a novel mouse model of ovarian cancer cachexia

A high proportion of women with advanced epithelial ovarian cancer (EOC) experience weakness and cachexia. This relationship is associated with increased morbidity and mortality. EOC is the most lethal gynecological cancer, yet no preclinical cachexia model has demonstrated the combined hallmark features of metastasis, ascites development, muscle loss and weakness in adult immunocompetent mice. Here, we evaluated a new model of ovarian cancer-induced cachexia with the advantages of inducing cancer in adult immunocompetent C57BL/6J mice through orthotopic injections of EOC cells in the ovarian bursa. We characterized the development of metastasis, ascites, muscle atrophy, muscle weakness, markers of inflammation, and mitochondrial stress in the tibialis anterior (TA) and diaphragm ∼45, ∼75 and ∼90 days after EOC injection. Primary ovarian tumour sizes were progressively larger at each time point while severe metastasis, ascites development, and reductions in body, fat and muscle weights occurred by 90 Days. There were no changes in certain inflammatory (TNFα), atrogene (MURF1 and Atrogin) or GDF15 markers within both muscles whereas IL-6 was increased at 45 and 90 Day groups in the diaphragm. TA weakness in 45 Day preceded atrophy and metastasis that were observed later (75 and 90 Day, respectively). The diaphragm demonstrated both weakness and atrophy in 45 Day. In both muscles, this pre-severe-metastatic muscle weakness corresponded with considerable reprogramming of gene pathways related to mitochondrial bioenergetics as well as reduced functional measures of mitochondrial pyruvate oxidation and creatine-dependent ADP/ATP cycling as well as increased reactive oxygen species emission (hydrogen peroxide). Remarkably, muscle force per unit mass at 90 days was partially restored in the TA despite the presence of atrophy and severe metastasis. In contrast, the diaphragm demonstrated progressive weakness. At this advanced stage, mitochondrial pyruvate oxidation in both muscles exceeded control mice suggesting an apparent metabolic super-compensation corresponding with restored indices of creatine-dependent adenylate cycling. This mouse model demonstrates the concurrent development of cachexia and metastasis that occurs in women with EOC. The model provides physiologically relevant advantages of inducing tumour development within the ovarian bursa in immunocompetent adult mice. Moreover, the model reveals that muscle weakness in both TA and diaphragm precedes severe metastasis while weakness also precedes atrophy in the TA. An underlying mitochondrial bioenergetic stress corresponded with this early weakness. Collectively, these discoveries can direct new research towards the development of therapies that target pre-atrophy and pre-severe-metastatic weakness during EOC in addition to therapies targeting cachexia.