Angela Pierce

MYC-driven medulloblastoma (MB) is a highly aggressive brain tumor with poor prognosis and limited treatment options. Through CRISPR-Cas9 screening, we identify the Mediator-associated kinase CDK8 as a critical regulator of MYC-driven MB. Both genetic loss and pharmacological inhibition of CDK8 impair MB tumor growth. Moreover, we find that CDK8 cooperates with MYC to sustain the MYC-mediated translational program, as CDK8 depletion induces pronounced transcriptional changes in translation-associated gene sets, reduces ribosome biogenesis, and impairs protein synthesis. Mechanistically, CDK8 regulates the occupancy of RNA polymerase II at specific chromatin loci, facilitating epigenetic alterations that promote the transcription of ribosomal genes. Furthermore, combined inhibition of CDK8 and mTOR synergistically enhances therapeutic efficacy in vivo, leading to more pronounced tumor growth suppression. Overall, our findings establish a functional link between CDK8-mediated transcriptional regulation and mRNA translation, suggesting a promising therapeutic approach targeting protein synthesis for MYC-driven MB.

Medulloblastoma (MB) is the most prevalent malignant brain tumor in children, exhibiting clinical and genomic heterogeneity. Of the four major subgroups, Group 3 tumors (MYC-MB), display high levels of MYC and metastasis rates. Despite treatment with surgery, radiation, and chemotherapy, patients with Group 3 MB are more likely to develop aggressive recurrent tumors with poor survival. To examine resistance mechanisms in this study, we perform single nuclei multiome analysis of matched primary and recurrent tumors. Therapy resistant Medulloblastoma demonstrates an expanded persistent progenitor population. Additionally, distinct chromatin landscapes link to altered transcription and correspond with metabolic reprogramming. In vivo modeling of radiation resistance exhibits similar chromatin-based metabolic reprogramming focused on wild-type isocitrate dehydrogenase (IDH1) activity. IDH1 inhibition reverses resistance-mediated chromatin changes and enables radiation re-sensitization. Ultimately, these findings demonstrate the efficacy of single-cell multiome analysis in elucidating resistance mechanisms and identifying targetable pathways for MYC-driven medulloblastoma.

CD99 expression in H3K27M mutant and H3-WT expressing patient DMG tumors, tumor cell lines, and multiple normal tissues. Expression and functional diversity of CD99 isoforms across cellular contexts.

Systemic 10D1 animal treatment protocol, changes in tumor burden in the mouse pons with 10D1 treatment using different BLI images, changes in animal body weight. IHC images of the tumor tissue collected at the animal endpoint show CD99 and caspase 3 changes.

Western blot and flow cytometric data showing modulation of H3K27M mutation leading to changes in CD99 and H3K27me3 proteins in neoplastic and normal cells.

Fold changes in the RNA transcripts in SU-DIPG04 cells shNull vs shCD99 #1.

Selection and affinity of best binding CD99 antibody clones using western blotting and functional effects of 10D1 in DMG, normal human astrocytes, and iPScs.

Animal survival benefits after receiving either intravenous (IV), intrathecal (IT), or IT followed by IV delivery of 10D1 treatment as a monotherapy and when combined with FFRT.

Treatment protocol to evaluate the efficacy of 10D1 delivery routes combined with FFRT in DMG Xenografts. Changes in the tumor burden following the treatment protocol, shown by BLI images, and a significant increase in animal survival, demonstrated by Kaplan-Meier plot.

RNA qRT-PCR primers and their sequences.