The intersection between aerobic glycolysis, cerebellar neurogenesis, and medulloblastoma

Aerobic glycolysis supports proliferation in development and cancer through unresolved mechanisms. Aerobic glycolysis, which supports the generation of biomass, is integral to cerebellar granule neuron progenitors (CGNPs) for normal growth and is hijacked in medulloblastoma. Medulloblastoma, the most common malignant pediatric brain tumor, is approached as a disorder of normal brain development. Arising as a disruption of normal cerebellar growth, medulloblastoma exploits the cellular processes used for cerebellar development to promote tumor formation. Thus, genes that are involved in developmentally-regulated progenitor growth may contribute to tumorigenesis when aberrantly expressed. A better understanding of cerebellar development and thus the pathogenesis of medulloblastoma, may lead to more targeted cancer treatments. In response to the developmental mitogen Sonic Hedgehog (SHH), CGNPs increase aerobic glycolysis and up-regulate key glycolytic enzymes Hexokinase-2 (Hk2) and Pyruvate Kinase M2 (Pkm2). HK2, which catalyzes the first step in glycolysis, is required for aerobic glycolysis in brain progenitors and medulloblastomas. Hk2 deletion blocks aerobic glycolysis, disrupts proliferation, and restricts medulloblastoma growth to prolong survival. Moreover, Hk2 was found by others to be up-regulated in medulloblastomas resistant to SHH pathway inhibition by vismodegib treatment. These findings raise the question if Hk2 deletion sensitizes medulloblastoma to vismodegib. Downstream of Hk2, the effect of deleting PKM2 and disrupting the last step in glycolysis in cerebellar neurogenesis and medulloblastoma is unknown. This dissertation examines the importance of aerobic glycolysis to development and cancer. Specifically, I determined the effect of Pkm2 deletion on the cerebellar neurogenesis and medulloblastoma tumorigenesis and the effect of vismodegib treatment on Hk2-deleted medulloblastomas. I demonstrate that CGNPs and medulloblastomas specifically express Pkm as the less active PKM2 isoform. Pkm2 deletion in CGNPs reduces aerobic glycolysis, alters metabolism to increase progenitor proliferation, and accelerates medulloblastoma growth to shorten survival. Thus PKM2 is not required for neural progenitor proliferation or tumorigenesis. Rather, the loss of pyruvate kinase releases cells from growth inhibition. I also found that vismodegib treatment of Hk2-deleted tumors further restricts tumor growth but does not extend survival. Together, these studies demonstrate the potential of targeting aerobic glycolysis as an anti-cancer strategy.Doctor of Philosoph

Adaptations of energy metabolism during cerebellar neurogenesis are co-opted in medulloblastoma

AbstractRecent studies show that metabolic patterns typical of cancer cells, including aerobic glycolysis and increased lipogenesis, are not unique to malignancy, but rather originate in physiologic development. In the postnatal brain, where sufficient oxygen for energy metabolism is scrupulously maintained, neural progenitors nevertheless metabolize glucose to lactate and prioritize lipid synthesis over fatty acid oxidation. Medulloblastoma, a cancer of neural progenitors that is the most common malignant brain tumor in children, recapitulates the metabolic phenotype of brain progenitor cells. During the physiologic proliferation of neural progenitors, metabolic enzymes generally associated with malignancy, including Hexokinase 2 (Hk2) and Pyruvate kinase M2 (PkM2) configure energy metabolism to support growth. In these non-malignant cells, expression of Hk2 and PkM2 is driven by transcriptional regulators that are typically identified as oncogenes, including N-myc. Importantly, N-myc continues to drive Hk2 and PkM2 in medulloblastoma. Similarly E2F transcription factors and PPARγ function in both progenitors and medulloblastoma to optimize energy metabolism to support proliferation. These findings show that the "metabolic transformation" that is a hallmark of cancer is not specifically limited to cancer. Rather, metabolic transformation represents a co-opting of developmental programs integral to physiologic growth. Despite their physiologic origins, the molecular mechanisms that mediate metabolic transformation may nevertheless present ideal targets for novel anti-tumor therapy

Chemosensitivity of IDH1-Mutated Gliomas Due to an Impairment in PARP1-Mediated DNA Repair

Mutations in isocitrate dehydrogenase (IDH) are the most prevalent genetic abnormalities in lower grade gliomas. The presence of these mutations in glioma is prognostic for better clinical outcomes with longer patient survival. In the present study, we found that defects in oxidative metabolism and 2-HG production confer chemosensitization in IDH1-mutated glioma cells. In addition, temozolomide (TMZ) treatment induced greater DNA damage and apoptotic changes in mutant glioma cells. The PARP1-associated DNA repair pathway was extensively compromised in mutant cells due to decreased NAD+ availability. Targeting the PARP DNA repair pathway extensively sensitized IDH1-mutated glioma cells to TMZ. Our findings demonstrate a novel molecular mechanism that defines chemosensitivity in IDH-mutated gliomas. Targeting PARP-associated DNA repair may represent a novel therapeutic strategy for gliomas

Pyruvate Kinase Inhibits Proliferation during Postnatal Cerebellar Neurogenesis and Suppresses Medulloblastoma Formation

Aerobic glycolysis supports proliferation through unresolved mechanisms. We have previously shown that aerobic glycolysis is required for the regulated proliferation of cerebellar granule neuron progenitors (CGNP) and for the growth of CGNP-derived medulloblastoma. Blocking the initiation of glycolysis via deletion of hexokinase-2 (Hk2) disrupts CGNP proliferation and restricts medulloblastoma growth. Here, we assessed whether disrupting pyruvate kinase-M (Pkm), an enzyme that acts in the terminal steps of glycolysis, would alter CGNP metabolism, proliferation, and tumorigenesis. We observed a dichotomous pattern of PKM expression, in which postmitotic neurons throughout the brain expressed the constitutively active PKM1 isoform, while neural progenitors and medulloblastomas exclusively expressed the less active PKM2. Isoform-specific Pkm2 deletion in CGNPs blocked all Pkm expression. Pkm2-deleted CGNPs showed reduced lactate production and increased SHH-driven proliferation.13C-flux analysis showed that Pkm2 deletion reduced the flow of glucose carbons into lactate and glutamate without markedly increasing glucose-to-ribose flux. Pkm2 deletion accelerated tumor formation in medulloblastoma- prone ND2:SmoA1 mice, indicating the disrupting PKM releases CGNPs from a tumor-suppressive effect. These findings show that distal and proximal disruptions of glycolysis have opposite effects on proliferation, and that efforts to block the oncogenic effect of aerobic glycolysis must target reactions upstream of PKM

Acetaminophen-induced acute liver injury in HCV transgenic mice

The exact etiology of clinical cases of acute liver failure is difficult to ascertain and it is likely that various co-morbidity factors play a role. For example, epidemiological evidence suggests that coexistent hepatitis C virus (HCV) infection increased the risk of acetaminophen-induced acute liver injury, and was associated with an increased risk of progression to acute liver failure. However, little is known about possible mechanisms of enhanced acetaminophen hepatotoxicity in HCV-infected subjects. In this study, we tested a hypothesis that HCV-Tg mice may be more susceptible to acetaminophen hepatotoxicity, and also evaluated the mechanisms of acetaminophen-induced liver damage in wild type and HCV-Tg mice expressing core, E1 and E2 proteins. Male mice were treated with a single dose of acetaminophen (300 or 500 mg/kg in fed animals; or 200 mg/kg in fasted animals; i.g.) and liver and serum endpoints were evaluated at 4 and 24 hrs after dosing. Our results suggest that in fed mice, liver toxicity in HCV-Tg mice is not markedly exaggerated as compared to the wild-type mice. In fasted mice, greater liver injury was observed in HCV-Tg mice. In fed mice dosed with 300 mg/kg acetaminophen, we observed that liver mitochondria in HCV-Tg mice exhibited signs of dysfunction showing the potential mechanism for increased susceptibility

Adaptations of energy metabolism during cerebellar neurogenesis are co-opted in medulloblastoma

AbstractRecent studies show that metabolic patterns typical of cancer cells, including aerobic glycolysis and increased lipogenesis, are not unique to malignancy, but rather originate in physiologic development. In the postnatal brain, where sufficient oxygen for energy metabolism is scrupulously maintained, neural progenitors nevertheless metabolize glucose to lactate and prioritize lipid synthesis over fatty acid oxidation. Medulloblastoma, a cancer of neural progenitors that is the most common malignant brain tumor in children, recapitulates the metabolic phenotype of brain progenitor cells. During the physiologic proliferation of neural progenitors, metabolic enzymes generally associated with malignancy, including Hexokinase 2 (Hk2) and Pyruvate kinase M2 (PkM2) configure energy metabolism to support growth. In these non-malignant cells, expression of Hk2 and PkM2 is driven by transcriptional regulators that are typically identified as oncogenes, including N-myc. Importantly, N-myc continues to drive Hk2 and PkM2 in medulloblastoma. Similarly E2F transcription factors and PPARγ function in both progenitors and medulloblastoma to optimize energy metabolism to support proliferation. These findings show that the "metabolic transformation" that is a hallmark of cancer is not specifically limited to cancer. Rather, metabolic transformation represents a co-opting of developmental programs integral to physiologic growth. Despite their physiologic origins, the molecular mechanisms that mediate metabolic transformation may nevertheless present ideal targets for novel anti-tumor therapy

Acetaminophen-induced acute liver injury in HCV transgenic mice

The exact etiology of clinical cases of acute liver failure is difficult to ascertain and it is likely that various co-morbidity factors play a role. For example, epidemiological evidence suggests that coexistent hepatitis C virus (HCV) infection increased the risk of acetaminophen-induced acute liver injury, and was associated with an increased risk of progression to acute liver failure. However, little is known about possible mechanisms of enhanced acetaminophen hepatotoxicity in HCV-infected subjects. In this study, we tested a hypothesis that HCV-Tg mice may be more susceptible to acetaminophen hepatotoxicity, and also evaluated the mechanisms of acetaminophen-induced liver damage in wild type and HCV-Tg mice expressing core, E1 and E2 proteins. Male mice were treated with a single dose of acetaminophen (300 or 500 mg/kg in fed animals; or 200 mg/kg in fasted animals; i.g.) and liver and serum endpoints were evaluated at 4 and 24 hrs after dosing. Our results suggest that in fed mice, liver toxicity in HCV-Tg mice is not markedly exaggerated as compared to the wild-type mice. In fasted mice, greater liver injury was observed in HCV-Tg mice. In fed mice dosed with 300 mg/kg acetaminophen, we observed that liver mitochondria in HCV-Tg mice exhibited signs of dysfunction showing the potential mechanism for increased susceptibility

Bio-logger Ethogram Benchmark: A benchmark for computational analysis of animal behavior, using animal-borne tags

This repository contains the datasets presented in our forthcoming work: B. Hoffman, M. Cusimano, V. Baglione, D. Canestrari, D. Chevallier, D. DeSantis, L. Jeantet, M. Ladds, T. Maekawa, V. Mata-Silva, V. Moreno-González, A. Pagano, E. Trapote, O. Vainio, A. Vehkaoja, K. Yoda, K. Zacarian, A. Friedlaender, and C. Rutz, "A benchmark for computational analysis of animal behavior, using animal-borne tags," 2023. It also contains the experiment results which are reported in the paper. Standardized code to implement, train, and evaluate models can be found at https://github.com/earthspecies/BEBE/. Please note the licenses in each dataset folder. Zip folders beginning with "formatted": These are the datasets we used to run the experiments reported in the benchmark paper. Zip folders beginning with "raw": These are the unprocessed datasets used in BEBE. Code to process these raw datasets into the formatted ones used by BEBE can be found at https://github.com/earthspecies/BEBE-datasets/. Zip folders beginning with "experiments": Results of the cross-validation experiments reported in the paper, as well as hyperparameter optimization. Confusion matrices for all experiments can also be found here