Opposing Tumor-Promoting and -Suppressive Functions of Rictor/mTORC2 Signaling in Adult Glioma and Pediatric SHH Medulloblastoma

Cell Rep. 2018 Jul 10;24(2):463-478.e5. doi: 10.1016/j.celrep.2018.06.050.

Abstract

Most human cancers arise from stem and progenitor cells by the sequential accumulation of genetic and epigenetic alterations, while cancer modeling typically requires simultaneous multiple oncogenic events. Here, we show that a single p53 mutation, despite causing no defect in the mouse brain, promoted neural stem and progenitor cells to spontaneously accumulate oncogenic alterations, including loss of multiple chromosomal (chr) regions syntenic to human chr10 containing Pten, forming malignant gliomas with PI3K/Akt activation. Rictor/mTORC2 loss inhibited Akt signaling, greatly delaying and reducing glioma formation by suppressing glioma precursors within the subventricular zone stem cell niche. Rictor/mTORC2 loss delayed timely differentiation of granule cell precursors (GCPs) during cerebellar development, promoting sustained GCP proliferation and medulloblastoma formation, which recapitulated critical features of TP53 mutant sonic hedgehog (SHH) medulloblastomas with GLI2 and/or N-MYC amplification. Our study demonstrates that Rictor/mTORC2 has opposing functions in neural stem cells and GCPs in the adult and the developing brain, promoting malignant gliomas and suppressing SHH-medulloblastoma formation, respectively.

Keywords: Akt; PI3K; Pten; Rictor; glioblastoma; mTORC2; mammalian target of rapamycin complex 2; medulloblastoma; p53; phosphatidylinositol 3-kinase pathway.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Animals
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Carcinogenesis / pathology
  • Cell Differentiation
  • Cell Proliferation
  • Child
  • Genome, Human
  • Glioma / genetics
  • Glioma / metabolism*
  • Glioma / pathology
  • Hedgehog Proteins / metabolism*
  • Humans
  • Mechanistic Target of Rapamycin Complex 2 / metabolism*
  • Medulloblastoma / genetics
  • Medulloblastoma / metabolism*
  • Medulloblastoma / pathology
  • Mice
  • Mutation / genetics
  • Protein Binding
  • Proteolysis
  • Proto-Oncogene Proteins c-akt / metabolism
  • Rapamycin-Insensitive Companion of mTOR Protein / metabolism*
  • Signal Transduction*
  • Treatment Outcome
  • Tumor Suppressor Protein p53 / genetics

Substances

  • ATOH1 protein, human
  • Basic Helix-Loop-Helix Transcription Factors
  • Hedgehog Proteins
  • RICTOR protein, human
  • Rapamycin-Insensitive Companion of mTOR Protein
  • SHH protein, human
  • Tumor Suppressor Protein p53
  • Mechanistic Target of Rapamycin Complex 2
  • Proto-Oncogene Proteins c-akt