TMIC-03LOSS OF DAMAGE-ASSOCIATED MOLECULAR PATTERN SENSING IN CANCER STEM CELLS PROMOTES GLIOBLASTOMA MAINTENANCE

Abstract

TMIC-03. LOSS OF DAMAGE-ASSOCIATED MOLECULAR PATTERN SENSING IN CANCER STEM CELLS PROMOTES GLIOBLASTOMA MAINTENANCE Alvaro Alvarado1,2, James Hale1, Erin Mulkearns-Hubert1, Daniel Silver1, and Justin Lathia1,2; Cleveland Clinic, Cleveland, OH, USA; Case Western Reserve University, Cleveland, OH, USA Glioblastoma (GBM) is composed of heterogeneous cellular populations, including self-renewing, tumorigenic cancer stem cells (CSCs). Discrete anatomical niches have been described where CSCs communicate with their surroundings to promote their self-renewal, tumor maintenance and increased resistance to conventional therapies. A hallmark of GBM is necrosis and the tumor microenvironment also contains many damage-associated molecular pattern molecules (DAMPs) that elicit an immune response and trigger cell death. These DAMPs are sensed by receptors such as those from the toll-like receptor (TLR) family, which have well-established roles in non-immune cells within the brain. The mechanisms by which CSCs but not other tumors cells can thrive despite DAMPs have yet to be elucidated. We analyzed the expression of TLR family members in patient-derived cells and found TLR4 was significantly decreased inCSCs comparedwith non-CSC. Bioinformatics analyses of patient datasets confirmed lower TLR4 expression is associated with poor prognosis. Stimulation of TLR4 induced a decrease in proliferation in non-CSCs, which was not observed in CSCs. Overexpression of TLR4 in CSCs decreased proliferation and self-renewal as well as expression of the stem cell markers SOX2, OCT4, NANOG, and OLIG2. We analyzed the promoter region of these critical genes and identified common transcription factors that were further validated by comparing their expression in CSCs vs. non-CSCs in a RNA-seq dataset. The expression of the top ten candidates was analyzed in the context of TLR4 overexpression. We identified Retinoblastoma binding protein 5 (RbBP5) as a potential key player in this signaling pathway. Mechanistic studies are in progress to determine how RbBP5 and TLR4 interact to regulate stem cell and self-renewal pathways. Our results link a damage-sensing receptor to a CSC-specific transcription factor that is upregulated in GBM and allows cells to tolerate hostile environmental cues. Neuro-Oncology 17:v221–v225, 2015. doi:10.1093/neuonc/nov236.3 Published by Oxford University Press on behalf of the Society for Neuro-Oncology 2015.