Journal
ONCOGENE
Volume 29, Issue 23, Pages 3411-3422Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/onc.2010.83
Keywords
miR-17-92; glioblastoma; retinoic acid; spheroid culture; CTGF
Funding
- German Bundesministerium fur Bildung und Forschung [01GS0883, 01GS0884, 01GS0886]
- European Union [MRTN-CT-2006-035733]
- Tumorzentrum Heidelberg-Mannheim
- Sibylle Assmus Foundation
- Verein zur Forderung der Krebsforschung e.V
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All-trans retinoic acid is a potent promoter of cellular differentiation processes, which is used in cancer therapy. Glioblastoma spheroid cultures are enriched in tumor-initiating cells, and provide a model to test new treatment options in vitro. We investigated the molecular mechanisms of response to exposure to differentiation-promoting conditions in such cultures. Microarray analyses of five independent cultures showed that after induction of differentiation, inhibitors of transforming growth factor beta/bone morphogenetic protein, Wnt/beta-catenin and IGF signaling were upregulated, whereas expression of several microRNAs decreased, particularly that of the miR-17-92 cluster. In primary astrocytic gliomas (n = 82), expression of several members of miR-17-92 was significantly higher relative to those of normal brain (n = 8) and significantly increased with tumor grade progression (P < 0.05). A high-level amplification of the miR-17-92 locus was detected in one glioblastoma specimen. Transfection of inhibitors of miR-17-92 induced increased apoptosis and decreased cell proliferation in glioblastoma spheroids. Mir-17-92 inhibition was also associated with increased messenger RNA (mRNA) and/or protein expression of CDKN1A, E2F1, PTEN and CTGF. The CTGF gene was shown to be a target of miR-17-92 in glioblastoma spheroids by luciferase reporter assays. Our results suggest that miR-17-92 and its target CTGF mediate effects of differentiation-promoting treatment on glioblastoma cells through multiple regulatory pathways. Oncogene (2010) 29, 3411-3422; doi:10.1038/onc.2010.83; published online 22 March 2010
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