Coexpression of neuronatin splice forms promotes medulloblastoma growth.
Medulloblastoma (MB) is the most common pediatric brain cancer. Several important developmental pathways have been implicated in MB formation, but fewer therapeutic targets have been identified. To locate frequently overexpressed genes, we performed a comprehensive gene expression survey of MB. Our comparison of 20 primary tumors to normal cerebellum identified neuronatin (NNAT) as the most frequently overexpressed gene in our analysis. NNAT is a neural-specific developmental gene with alpha and beta splice forms. Functional evaluation revealed that RNA interference knockdown of NNAT causes a significant decrease in proliferation. Conversely, coexpression of both splice forms in NNAT-negative MB cell lines increased proliferation, caused a significant shift from G(1) to G(2)/M, and increased soft agar colony formation and size. When expressed individually, each NNAT splice form had much less effect on these in vitro oncogenic predictors. In an in vivo model, the coexpression of both splice forms conferred the ability of xenograft formation to human MB cells that do not normally form xenografts, whereas a control gene had no effect. Our findings suggest that the frequently observed overexpression of both NNAT splice forms in MB enhances growth in this cancer.
Siu
I-Mei
IM
Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, MD 21231 USA.
Bai
Renyuan
R
Gallia
Gary L
GL
Edwards
Jennifer B
JB
Tyler
Betty M
BM
Eberhart
Charles G
CG
Riggins
Gregory J
GJ
D000328:Adult; D000368:Aged; D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002528:Cerebellar Neoplasms / Q000235:genetics*; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008527:Medulloblastoma / Q000235:genetics*; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics*; D020033:Protein Isoforms; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction
D008565:Membrane Proteins; C490237:NNAT protein, human; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms