Biology subjects

Dismuke, T.

Publications and source records attributed to Dismuke, T..

4 recordsLinked to original sources

bioRxiv2022

Targeting OLIG2 increases therapeutic responses in SHH medulloblastoma mouse models and patient-derived medulloblastoma organoids

Recurrence after therapy is the primary life-threatening complication of medulloblastoma. In Sonic Hedgehog (SHH)-subgroup medulloblastoma, OLIG2-expressing tumour stem cells are crucial to recurrence. We investigated the potential of the small-molecule OLIG2 inhibitor CT-179 to decrease recurrence in patient-derived organoids, mice genetically-engineered to develop SHH-driven MB, and mice with MB patient-derived xenograft (PDX) tumours. We found that OLIG2 mRNA significantly correlated with poor survival in patients with SHH-MB, but not other subgroups. CT-179 rapidly downregulated OLIG2 protein in vitro and displayed nanomolar IC50 values. CT-179 arrested MB cells at G2/M, with degradation of cyclin B1 and phospho-CDK1 inducing apoptosis. In vivo CT-179 induced similar cell cycle changes in MBs in Smo-mutant mice and significantly increased mouse survival. In both MB organoids and mouse models, CT-179 combined with radiotherapy showed greater efficacy than either treatment alone. These data highlight the potential for OLIG2-targeted therapy to improve MB outcomes by targeting recurrent disease.

cancer biology↗

bioRxiv2021

Chronic AMPK inactivation slows SHH medulloblastoma progression by inhibiting mTORC1 signaling and depleting tumor stem cell populations

We show that inactivating AMPK in vivo in a genetic model of medulloblastoma depletes tumor stem cell populations and slows tumor progression. Medulloblastoma, the most common malignant pediatric brain tumor, grows as heterogenous communities comprising diverse types of tumor and stromal cells. Previously, we showed that different populations in medulloblastomas show different sensitivities to specific targeted therapies. To determine if specific populations depend on AMPK, we analyzed mice with AMPK-inactivated medulloblastomas. We engineered mice with conditional deletion of the AMPK catalytic subunits Prkaa1 and Prkaa2 and conditional expression SmoM2, an oncogenic Smo allele that hyperactivates Sonic Hedgehog (SHH) signaling. We compared these medulloblastomas to SmoM2-driven medulloblastomas in AMPK-intact mice. AMPK-inactivation slowed tumor growth and progression, allowing longer event-free survival (EFS). scRNA-seq showed that AMPK inactivation altered cellular heterogeneity, increasing differentiation, decreasing tumor stem cell populations and reducing glio-neuronal multipotency. Surprisingly, AMPK-inactivated tumors showed decreased mTORC1 activation and Hk2 expression. Genetic Hk2 deletion in SmoM2-medulloblastomas similarly decreased stem cell populations, implicating reduced aerobic glycolysis in the tumor-suppressive effect of AMPK inactivation. Our results show that AMPK inactivation impairs tumor growth through mechanisms that disproportionately affect tumor stem cell populations that have proved refractory to conventional therapies.

cancer biology↗

bioRxiv2021

Nanoparticle-delivered palbociclib enable CDK4/6 inhibitor therapy while combination with mTORC1 inhibitor sapanisertib induces long term benefits in SHH medulloblastoma.

CDK4/6 inhibitors hold promise for brain tumor treatment, but efficacy has been limited by recurrence in both preclinical models and clinical trials. To address recurrence, we tested a nanoparticle formulation of the CDK4/6 inhibitor palbociclib (POx-palbo) in mice genetically-engineered to develop SHH-driven medulloblastoma. We then analyzed medulloblastomas in mice receiving palbociclib treatment, and compared the efficacy of combining palbociclib with specific inhibitors suggested by our analysis. POx-Palbo showed reduced toxicity compared to conventional palbociclib, was tolerable in parenteral administration, improved CNS pharmacokinetics, and extended survival of mice with medulloblastoma. Recurrence, however, remained problematic as fractions of tumor cells proliferated during therapy. ScRNA-seq identified a gene expression pattern unique to proliferating medulloblastoma cells in POx-Palbo-treated mice, marked by up-regulation of the glutamate transporter Slc1a2 and down-regulation of diverse ribosomal genes. Reduced mTORC1 signaling, suggested by ribosomal suppression in POx-Palbo-treated tumors was confirmed by decreased 4EBP1 phosphorylation (p4EBP1). Further reducing mTORC1 activity by combining POx-Palbo with the mTORC1 inhibitor sapanisertib produced mutually enhancing effects, with increased suppression of both pRB and p4EBP1, and prolonged mouse survival compared to either agent alone. In contrast, targeting cell cycle progression by combining POx-Palbo with the SHH-pathway inhibitor vismodegib, or with the replication-targeting agents gemcitabine or etoposide, failed to enhance efficacy. Our data show the potential of nanoparticle formulation and scRNA-seq analysis of resistance to improve brain tumor treatment, and identify POx-palbo plus sapanisertib as effective combinatorial therapy for SHH medulloblastoma. This combination may be appropriate for testing in patients with recurrence, who need new options.

cancer biology↗

bioRxiv2020

Poly(2-oxazoline) nanoparticle delivery enhances the therapeutic potential of vismodegib for medulloblastoma by improving CNS pharmacokinetics and reducing systemic toxicity

We report a novel, nanoparticle formulation of the SHH pathway inhibitor vismodegib that improves efficacy for medulloblastoma treatment while reducing toxicity. Systemic therapies for brain tumors are complicated by restricted blood-brain barrier (BBB) permeability and dose-limiting extraneural toxicity, therefore improved delivery approached are needed. Here we show how a nanoparticle delivery system addresses these obstacles, bringing new efficacy to previously ineffective therapy. Vismodegib has been a promising agent for patients with SHH- subgroup medulloblastoma and is FDA-approved for basal cell carcinoma. However, vismodegib has limited benefit for patients with SHH-driven medulloblastoma, due to off-target toxicities and the development of resistance during therapy. We encapsulated vismodegib in polyoxazoline block copolymer micelles (POx-vismo). We then evaluated POx-vismo using transgenic mice engineered to develop endogenous medulloblastomas, testing the novel agent in a preclinical model with native vasculature and tumor microenvironment. POx-vismo showed improved CNS pharmacokinetics and reduced systemic and bone toxicity. Mechanistic studies show that POx nanoparticles did not enter the CNS, but rather acted within the vascular compartment to improve drug delivery by decreasing drug binding to serum proteins and reducing the volume of distribution. POx-vismo demonstrated improved efficacy, extending the survival of medulloblastoma-bearing mice. Our results show the potential for a simple, non-targeted nanoparticle formulation to improve systemic brain tumor therapy, and specifically to enhance vismodegib therapy for SHH-driven cancers.

neuroscience↗