Abstract 1126: Exploring the roles of Suppressor of Fused in the postnatal neurogenic niche and tumorigenesis

Abstract

Abstract Isolated brain tumors consist of cells with stem cell features and a tissue microenvironment similar to the neurogenic niche, implying that tumors must require the same niche factors for tumor growth and progression. Thus, a better understanding of how neural stem cell (NSC) behavior is regulated can have significant therapeutic implications in brain cancers. To this end, we examined the roles of Suppressor of Fused (Sufu) in the postnatal neurogenic niche of the forebrain, the ventricular-subventricular zone (V-SVZ), a potential site of origin for forebrain tumors. Given that recent studies showed low expression of Sufu in gliomas, we wondered how conditional deletion of Sufu using the hGFAP-Cre driver (hGFAP-cre/+;Sufu-fl/fl) influences NSC behavior in the V-SVZ. We found that Sufu critically controls NSC proliferation, since loss of Sufu in the hGFAP-cre/+;Sufu-fl/fl mice resulted in abnormal expansion of the V-SVZ. These defects were due to the increased production of DCX+ Type A cells at the expense of transit amplifying Type C and oligodendrocyte precursor cells. Furthermore, many of these cells failed to migrate out of the V-SVZ, where they remained and continued to proliferate. Nevertheless, an increase in apoptotic cells was observed, which likely prevented the formation of brain tumors from loss of Sufu function alone. Indeed, our preliminary studies showed that the combined deletion of Sufu and the tumor suppressor p53 (hGFAP-Cre/+;Sufu-fl/fl;p53-fl/fl) resulted in a more severe and sustained cell expansion phenotype in the V-SVZ. We predict that these genetic conditions predispose NSCs within the V-SVZ to form tumors at later postnatal stages. We are now investigating this and the molecular mechanisms by which Sufu exerted this effect. Of particular focus is the role of Sufu as an inhibitor of the mitogenic Sonic hedgehog (Shh) signaling, which is highly active in various glioblastoma subtypes. Taken together, our findings point to a potential role for Sufu in preventing tumor development in the forebrain. Our studies also provide novel insights on how developmental and oncogenic signals converge to initiate tumorigenesis or tumor progression. We hope that these studies will lead to the identification of critical niche factors that may be targeted to treat brain cancers and improve patient outcome. Citation Format: Jesse Garcia Castillo, Hector G. Gomez, David Aguilar, Samuel J. Pleasure, Odessa Yabut. Exploring the roles of Suppressor of Fused in the postnatal neurogenic niche and tumorigenesis [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 1126.