Abstract 1117: Norrin signaling is protumorigenic in glioblastoma progression

Norrin signaling is protumorigenic in GBM progression A-Introduction: Norrin, a secreted factor encoded by the Norrie Disease Protein gene (NDP), is an atypical WNT ligand that specifically binds the FZD4 receptor and activates the canonical WNT signaling pathway in endothelial cells to regulate vascular development and barrier function in the brain. Recently, our group identified a novel tumor inhibitory function of NDP/FZD4 signaling in the endothelium in mouse models of medulloblastoma. Here we investigated the function of the NDP/FZD4 signaling axis in glioblastoma (GBM) progression. B-Experimental approaches GBM patients' survival data was obtained from TCGA and analyzed using the cBioportal server. Low passage mitogen expanded GBM cancer stem cell lines were established from primary tumors using standard conditions. NDP expression in experimental cell lines was modulated using lentiviral delivery of short hairpins or full length cDNA. Cell number was assessed by trypan blue cell counting, and sphere forming cell frequency was tested using extreme limited dilution assay (ELDA). For in vivo assessment of tumorigenesis, experimental and control cell lines were xenografted intracranially in NOD/SCID/Gamma (NSG) mice and symptomatic animals were euthanized and brains collected for histological analysis. C-Results Analysis of GBM data from TCGA showed that survival and NDP expression are negatively GBM. Gene expression analysis indicated variable expression levels of NDP/FZD4 signaling pathway components in a panel of 10 primary GBM stem cell lines. In vitro gain and loss of function studies showed that NDP promotes proliferation and sphere formation in GBM. Moreover, the effects of are recapitulated in xenografts. NDP appears to control GBM differentiation, as it affects the proportion of cycling (Ki67+) cells and the level of stemness (Sox2 levels). Finally, NDP function is independent of FZD4 and canonical Wnt signaling, indicating that it functions through an alternative pathway. D-Conclusions Our in vitro and in vivo results indicate that Norrin might have an oncogeneic role in GBM. In addition, the effect of Norrin is FZD4- and WNT-independent. Our results indicate that targeting Norrin GBM might be a potential therapeutic approach. Citation Format: Ahmed A. Elsehemy, Hayden Selvadurai, Katherine Rowland, Peter Dirks, Valerie Wallace. Norrin signaling is protumorigenic in glioblastoma progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1117.