An OTX2-PAX3 signaling axis regulates Group 3 medulloblastoma cell fate

Area of Science:

• Oncology
• Developmental Neuroscience
• Genomics

Background:

• OTX2 is a key oncogene in Group 3 medulloblastoma, promoting tumor growth.
• Mechanisms of OTX2-mediated repression of neural differentiation remain unclear.
• Understanding OTX2's regulatory network is crucial for targeting Group 3 medulloblastoma.

Purpose of the Study:

• To identify the OTX2 regulatory network controlling cell fate in Group 3 medulloblastoma.
• To elucidate how OTX2 represses neural differentiation and promotes tumor progression.

Main Methods:

• Extensive multiomic analyses were performed.
• OTX2 silencing and its effects on chromatin landscape and gene expression were studied.
• Single-cell RNA sequencing was used on Group 3 medulloblastoma tumorspheres.
• Functional assays assessed the roles of PAX3 and PAX6 in vitro and in vivo.

Main Results:

• OTX2 silencing altered repressive chromatin, reduced PRC2 complex genes, and increased neurodevelopmental transcription factors (PAX3, PAX6).
• PAX3 and PAX6 expression were lower in Group 3 medulloblastoma patients, correlating with reduced survival.
• PAX3 specifically inhibited self-renewal in vitro and improved survival in vivo.
• An undifferentiated progenitor program, characterized by translation/elongation factor genes, was identified in tumorspheres.
• mTORC1 signaling was identified as a downstream effector of OTX2-PAX3 interaction.

Conclusions:

• OTX2 orchestrates a regulatory network impacting Group 3 medulloblastoma cell fate through chromatin modulation and transcription factor regulation.
• PAX3 plays a critical role in inhibiting tumor self-renewal and improving survival, highlighting its potential as a therapeutic target.
• Protein synthesis pathways, regulated by mTORC1 signaling, are implicated in Group 3 medulloblastoma pathogenesis downstream of OTX2 and PAX3.