Abstract 3363: Brain tumor stem-like cells as a tool for testing small molecules for anti-tumor therapy

Abstract

Abstract Glioblastoma multiforme (GBM) is the most common primary malignant tumor of the adult central nervous system. The highly lethal nature of this tumor partly derives from the acquisition of an invasive phenotype, which allows the tumor cells to infiltrate the surrounding brain tissues. In fact the tumor cells, leading to the recurrence of the primary neoplasm highly contribute to the lack of success in eradicating this disease. Recent evidences suggested that a rare population of stem-like cells (or tumor initiating cells) present in brain tumors may be responsible for development of highly invasive and chemoresistant recurrent tumors. It was suggested that not all the cells from a given brain tumor show the same ability to proliferate and sustain the growth. Only a relatively small fraction of those cells, termed Brain Tumor Stem-like Cells (BTSCs), possess the ability to proliferate, self-renew extensively and adapt to very different micro-environments. Further investigations have demonstrated that BTSCs also more closely mirror the phenotype and genotype of the primary tumors, in fact when used in animal models they are able to generate a tumor that recapitulates the features of the human GBMs. The absence of stem cell specific markers has posed challenges to the identification and isolation of BTSCs from the bulk tumor cells in a definitive manner. Furthermore, recent findings suggest that the Hedgehog (HH) pathway is involved in BTSCs population maintaining in GBM. We report that in a commercially available human recurrent GBM line (DBTRG-05MG) and in different patients derived GBM cells; the key components required for an active HH pathway, such as PTCH1, SMO and SHH, are present and differently expressed according to culture conditions. Cells cultured in serum containing media, have a switched-off HH pathway, while cells kept in serum free containing media supplemented with EGF and bFGF to promote the formation of floating growing neurospheres, show a functional HH signaling pathway. These GBM cells respond to the same mitogens that activate normal adult neural stem cells showing multipotent differentiation properties and expressing markers of the normal stem cells lineage, such as Nestin, SOX2, Bmi1 and Musashi1. Proliferation assays performed using GBM patient-derived neurospheres clearly showed higher sensitivity to the different SMO antagonists tested when compared to the adherent counterpart cultured in serum containing media. The effect of small molecules SMO antagonists in self-renewal assays, confirmed the implication of the HH pathway in the growth of these stem-like cells. Taken together, these data demonstrate the presence of an operational HH pathway in human GBM derived neurospheres, and the ability of those cells to be applied in a drug discovery setting as a reliable SMO antagonists phenotypic testing tool. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3363. doi:1538-7445.AM2012-3363