Abstract
Abstract Glioblastoma multiforme is the most aggressive form of human glioma and despite recent progress in therapy the prognosis remains dismal with a median survival of 15 months. Expression based prediction of gene alterations identified Wnt inhibitory factor I (WIF1) as a new candidate tumor suppressor gene involved in glioblastoma. WIF1 encodes a secreted Wnt antagonist and it was strongly down-regulated in most glioblastoma as compared to normal brain, implying deregulation of Wnt signaling. Silencing of the WIF1 gene was found to be mediated by deletion and WIF1 promoter hypermethylation. Ectopic expression of WIF1 in glioblastoma cell lines revealed a dose dependent decrease of Wnt pathway activity. To further dissect the biological effects of WIF1 re-expression, we established WIF1 overexpressing glioblastoma cell lines. We observed that WIF1 re-expression inhibited cell proliferation in vitro and strongly reduced anchorage independent growth. The ability of forming colonies in soft agar was reduced to less than 11% of the control. Moreover, the expression of WIF1 was able to completely abolish tumorigenicity in a respective xenograft model in nude mice. Interestingly, WIF1 overexpression in glioblastoma cells induced a senescence-like phenotype characterized by the appearance of enlarged flattened and multinucleated cells positive for the presence of β-galactosidase, a late marker of senescence. These results provide evidence that WIF1 has tumor suppressing properties in glioblastoma, hence, the implication of a deregulated Wnt pathway may render glioblastoma sensitive to Wnt signaling inhibitors, potentially by diverting the tumor cells into a senescence-like state. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2117. doi:10.1158/1538-7445.AM2011-2117
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