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

Abstract

OTX2 is a potent oncogene that promotes tumor growth in Group 3 medulloblastoma. However, the mechanisms by which OTX2 represses neural differentiation are not well characterized. Here, we perform extensive multiomic analyses to identify an OTX2 regulatory network that controls Group 3 medulloblastoma cell fate. OTX2 silencing modulates the repressive chromatin landscape, decreases levels of PRC2 complex genes and increases the expression of neurodevelopmental transcription factors including PAX3 and PAX6 . Expression of PAX3 and PAX6 is significantly lower in Group 3 medulloblastoma patients and is correlated with reduced survival, yet only PAX3 inhibits self-renewal in vitro and increases survival in vivo. Single cell RNA sequencing of Group 3 medulloblastoma tumorspheres demonstrates expression of an undifferentiated progenitor program observed in primary tumors and characterized by translation/elongation factor genes. Identification of mTORC1 signaling as a downstream effector of OTX2-PAX3 reveals roles for protein synthesis pathways in regulating Group 3 medulloblastoma pathogenesis.

Differences in RNA and microRNA Expression Between PTCH1- and SUFU-mutated Medulloblastoma

“…Recently, mTORC1 signaling was detected as a downstream effector of OTX2 in Group 3 MB (31). A relationship between mTOR pathway and SHH was also demonstrated for SHH MB (32,33).…”

In vitro Modeling of Embryonal Tumors

“…Following this principle, inhibition of N-MYC in MYCN-amplified neuroblastoma cell lines induced a differentiation morphology as well as upregulation of neural differentiation genes (Kang et al, 2006;Henriksen et al, 2011;Jiang et al, 2011;Westermark et al, 2011;Hossain et al, 2013). Differentiation phenotypes were also observed upon genetic manipulation of medulloblastoma models (Liu et al, 2017;Cheng et al, 2020;Zagozewski et al, 2020), and MRT models (Betz et al, 2002;Nakayama et al, 2017;Wang et al, 2017). These studies show that reversal of the genetic driver can transform tumor cells to a more mature cell state, possibly reflecting the matured cell type it would have become, had it not become cancerous.…”

From sorting to sequencing in the molecular era: the evolution of the cancer stem cell model in medulloblastoma

“…(A, B) Expression of 12 of the top genes associated with the undifferentiated (A) and differentiated (B) metaprograms as defined by Hovestadt et al [15] in single cells derived from HDMB03 Group 3 MB tumorspheres. Tumorspheres were previously analyzed by scRNA-seq in Zagozewski et al [101]. The undifferentiated metaprogram is associated with an undifferentiated progenitor state and is characterized by ribosomal and translational initiation/elongation factor genes.…”

“…demonstrated that cerebellar organoids can be used to model Group 3 MB and to test the effect of specific genes in modulating tumor growth [98]. Our laboratory recently employed scRNA‐seq to assess heterogeneity in stem cell‐enriched tumorsphere cultures from several newly established Group 3 MB cell lines [101]. These tumorspheres mirrored the specific undifferentiated ‘metaprogram’ associated with Group 3 MB patient samples [15] (Fig.…”

“…Tumorspheres were previously analyzed by scRNA‐seq in Zagozewski et al . [101]. The undifferentiated metaprogram is associated with an undifferentiated progenitor state and is characterized by ribosomal and translational initiation/elongation factor genes.…”