RNA-binding protein Musashi1 modulates glioma cell growth through the post-transcriptional regulation of Notch and PI3 kinase/Akt signaling pathways.

Abstract

Musashi1 (MSI1) is an RNA-binding protein that plays critical roles in nervous-system development and stem-cell self-renewal. Here, we examined its role in the progression of glioma. Short hairpin RNA (shRNA)-based MSI1-knock down (KD) in glioblastoma and medulloblastoma cells resulted in a significantly lower number of self renewing colony on day 30 (a 65% reduction), compared with non-silencing shRNA-treated control cells, indicative of an inhibitory effect of MSI1-KD on tumor cell growth and survival. Immunocytochemical staining of the MSI1-KD glioblastoma cells indicated that they ectopically expressed metaphase markers. In addition, a 2.2-fold increase in the number of MSI1-KD cells in the G2/M phase was observed. Thus, MSI1-KD caused the prolongation of mitosis and reduced the cell survival, although the expression of activated Caspase-3 was unaltered. We further showed that MSI1-KD glioblastoma cells xenografted into the brains of NOD/SCID mice formed tumors that were 96.6% smaller, as measured by a bioluminescence imaging system (BLI), than non-KD cells, and the host survival was longer (49.3±6.1 days vs. 33.6±3.6 days; P<0.01). These findings and other cell biological analyses suggested that the reduction of MSI1 in glioma cells prolonged the cell cycle by inducing the accumulation of Cyclin B1. Furthermore, MSI1-KD reduced the activities of the Notch and PI(3) kinase-Akt signaling pathways, through the up-regulation of Numb and PTEN, respectively. Exposure of glioma cells to chemical inhibitors of these pathways reduced the number of spheres and living cells, as did MSI1-KD. These results suggest that MSI1 increases the growth and/or survival of certain types of glioma cells by promoting the activation of both Notch and PI(3) kinase/Akt signaling.

• Authors: Jun Muto, Takao Imai, Daisuke Ogawa, Yoshinori Nishimoto, Yohei Okada, Yo Mabuchi, Takeshi Kawase, Akio Iwanami, Paul S Mischel, Hideyuki Saya, Kazunari Yoshida, Yumi Matsuzaki, Hideyuki Okano
• Journal: PloS one (PLoS One) Vol. 7 Issue 3 Pg. e33431 ( 2012) ISSN: 1932-6203 [Electronic] United States
• PMID: 22428049 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Cyclin B
• Msi1h protein, mouse
• Nerve Tissue Proteins
• RNA, Small Interfering
• RNA-Binding Proteins
• Receptors, Notch
• Phosphatidylinositol 3-Kinases
• Proto-Oncogene Proteins c-akt

Topics

• Animals
• Cell Cycle (physiology)
• Cell Line, Tumor
• Cyclin B (metabolism)
• Gene Knockdown Techniques
• Glioma (metabolism, physiopathology)
• Immunohistochemistry
• Mice
• Mice, Inbred NOD
• Mice, SCID
• Nerve Tissue Proteins (genetics, metabolism)
• Phosphatidylinositol 3-Kinases (metabolism)
• Proto-Oncogene Proteins c-akt (metabolism)
• RNA Interference (physiology)
• RNA, Small Interfering
• RNA-Binding Proteins (genetics, metabolism)
• Receptors, Notch (metabolism)
• Signal Transduction (genetics, physiology)