MEDB-80. CDK8 promotes stemness of MYC-driven medulloblastoma

Abstract

Cyclin-dependent kinase 8 (CDK8) belongs to the transcription-related cyclin dependent protein kinase family. CDK8 and cyclin C associate with the mediator complex to regulate gene transcription. Although CDK8 has been shown to be implicated in the malignancy of several types of cancer, its functional role and mechanism in medulloblastoma remains largely unknown. Here, we demonstrate how CDK8 plays an essential role in maintaining stemness and tumorigenicity in medulloblastoma stem cell. CDK8 inhibition suppresses stem cell associated signaling in medulloblastoma cells and inhibits tumor cell self-renewal. Additionally, CDK8 is amplified in MYC-driven medulloblastoma, is positively correlated with c-MYC expression in human medulloblastoma specimens and associates with poor survival in patients. Using cut&run assay, we found CDK8 associates with MED1 to activate transcription of MYC target genes. CDK8 attributes to MYC-driven transcriptional programs mediating DNA repair. Pharmaceutic inhibitors and genetic depletion result in cessation of tumor growth in xenograft mouse models and increase in apoptosis and DNA damage. Collectively, our studies establish the selective inhibition of CDK8 inhibition as a viable therapeutic strategy in MYC-driven medulloblastoma.