Abstract 5007: Delineating human fetal CNS stem cell hierarchy reveals a progenitor cell of origin for human Gliobastoma Multiforme.
Authors: Mitra Siddhartha S. , Gholamin Sharareh , Feroze Abdullah , Cheshier Samuel H. , Weissman Irving L. 
Published: August 2014

Glioblastoma Multiforme (GBM) is the most common and highly aggressive human brain tumor. Even with great advancement of surgical procedures and treatment regimens with radiation and chemotherapy, malignant gliomas remain incurable. This is due to their resistance to all conventional therapies and the diffuse infiltrative nature of the tumor cells, which makes complete tumor resection impossible. One of the major difficulties for the identification of the cell of origin for gliomas is the complex cellular composition of this disease. It is now hypothesized that the different subtypes of high-grade glioma may have different cell of origin and in mouse models it has been shown that the cell of origin resides within the progenitor populations. In order to identify the cell of origin we decided to first dissect out the various stages of CNS stem cell differentiation. After testing a panel of 34 antibodies to prospectively isolate neurospheres forming cells from human fetal brain tissue we identified a panel of four antibodies (i.e CD15, Notch1, EGFR, and CD90). Subpopulations of cells derived after FACS were analyzed for single cell lineage potency and the ability to generate neurospheres. Using an in-vitro limiting dilution assay, we ascertained that double-positive (DP; CD15+Notch1+EGFR-CD90-)) populations have the highest frequency of self-renewing cells, followed by quadruple-positive (QP) populations (CD15+Notch1+EGFR-CD90-). In-vitro differentiation assays reveal both DP and QP to be multipotent in nature however serial passaging showed that only the DP cells have a consistent self-renewing capacity, whereas QP derived cells were unable to survive after 5-6 passages.

In glioma samples however we observed by limiting dilution and serial passaging assays that the tumorsphere forming frequency was predominant in the QP population and not in the DP populations. Furthermore the GBM derived DP cells serially passaged if grown under normal neural stem cell growth condition suggesting that this population is still at a pre-malignant state. In-vivo tumorigenic assay via orthotopic implation of as few as a 1000 cells into mouse brain showed significantly higher tumor formation from the QP cells and not in the DP cells. Taken together our data suggests the presence of “normal” or pre-malignant stem cells in glioblastoma, which suggests a possible mechanism of relapse. These pre-malignant cells could comprise a cellular reservoir that may need to be targeted for future therapies.

Citation Format: Siddhartha S. Mitra, Sharareh Gholamin, Abdullah Feroze, Samuel H. Cheshier, Irving L. Weissman. Delineating human fetal CNS stem cell hierarchy reveals a progenitor cell of origin for human Gliobastoma Multiforme. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5007. doi:10.1158/1538-7445.AM2013-5007