Functional characterization of RNA-binding protein IMP2 in primary Glioma cell lines [array]

Cancer stem cells (CSC) dictate tumor cell heterogeneity in diverse cancer types and arise, in part, from microRNA (miRNA)-dependent alteration of gene expression. The let-7 miRNA family induces differentiation by silencing genes that maintain stemness and is repressed by the RNA-binding proteins LIN28A/B, which preserve stemness in normal embryonic and malignant cells. Here, we observed that LIN28A/B is undetectable in glioma stem cells (GSC) whereas let-7 and, paradoxically, their target genes are highly expressed. Using photoactivatable-ribonucloside-enchanced crosslinking and immunoprecipitation (PAR-CLIP), we show that insulin-like growth factor-2 mRNA-binding protein 2 (IMP2) protects let-7 target genes from silencing and provides a mechanistically distinct alternative to LIN28A/B toward both GSC and neural stem cell specification. Our observations define the RNA-binding repertoire of IMP2 and identify a mechanism by which it supports GSC maintenance. We characterized miRNA expression differences between glioma stem cells and their differentiated progeny using agilent miRNA microarrays in three different glioma cell lines and both cell states.