229. Recapitulation of Genetic Predisposition to Medulloblastoma in Human Neuroepithelial Stem Cells

Authors: Jignesh Tailor, S BSc; Miller Huang; Peter Dirks; Michael Taylor; Austin Smith; William Weiss (Toronto, Canada)

Introduction:

Human neural stem cell cultures provide progenitor cells that are potential cells of origin for brain cancers. However, the extent to which genetic predisposition to tumor formation can be faithfully captured in stem cell lines is uncertain. Here we evaluated neuroepithelial stem (NES) cells, long-term propagating hindbrain cells that are representative of the cerebellar primordium.

Methods:

First we transduced NES cells with N-MYC to test whether NES cells can be transformed to brain tumour initiating cells. In parallel, we generated induced pluripotent stem (iPS) cells from patient's with Gorlin syndrome (PTCH mutation) and subsequent differentiated these cells to NES cells to recapitulate the genetic predisposition to medulloblastoma formation. These NES cells were orthotopically transplanted into mouse cerebellum to test their tumor forming capacity.

Results:

Following orthotopic transplantation of NES cells transduced with N-MYC we observed formation of medulloblastoma. Significantly, transcriptomes and patterns of DNA methylation from xenograft tumors were globally more representative of human medulloblastoma compared to a MYCN-driven genetically engineered mouse model. Orthotopic transplantation of NES cells generated from Gorlin syndrome also generated medulloblastoma. We engineered candidate cooperating mutations in Gorlin NES cells, with mutation of DDX3X or loss of GSE1 both accelerating tumorigenesis.

Conclusion:

These findings demonstrate that human NES cells provide a potent experimental resource for dissecting genetic causation in medulloblastoma