DDRE-04. miR-149-3p INHIBITS THE GSC PHENOTYPE AND RE-SENSITIZES THERAPY-RESISTANT GBM CELLS

Abstract

Abstract BACKGROUND Intra-tumor heterogeneity presents one of the biggest challenges in the development of solid cancer therapeutics. Cells within the same tumor display distinct phenotypes that affect their growth rate, survival, migration, therapy-response, and tumor-propagating capacity. We now understand cancer stem cells (CSCs) play critical roles in driving intra-tumor cellular heterogeneity by establishing dynamic cellular transitions within tumors. GBM are highly aggressive tumors that display a poorly differentiated cell phenotype. Lineage-tracing experiments show that stem-like cells are responsible for GBM re-growth after therapy and this process is in part mediated by known drivers of stemness (e.g. Sox2). PURPOSE Understand the contribution of stem-cell driving mechanisms to the therapy-resistant phenotype of GBM. METHODS We used human GBM-derived neurosphere lines as cell models. miRNA expression was performed using commercially available mimics. Change in self-renewal capacity were measured via neurosphere formation assays, and levels of miRNA and stem cell markers were quantified by qRT-PCR. RESULTS We show that GBM cells expressing transgenic Oct4 and Sox2 are more resistant to ionizing radiation (IR) treatment and exposing GBM neurospheres to temozolomide (TMZ) and IR gives rise to a cell sub-set with higher gene expression levels of Oct4 and Sox2 compared to untreated cells. The clinical relevance of this phenotype is supported by multi-dimensional transcriptome analyses that identifies a group of genes induced by Oct4 and Sox2 enriched in recurrent GBM. We identified miR-149-3p as a high-priority candidate capable of simultaneously inhibiting several transcripts induced by Oct4/Sox2 in recurrent GBM. Transient expression of miR-149-3p decreases the capacity of GSCs to self-renew as spheres and re-sensitized therapy-resistant GSCs to TMZ treatment. CONCLUSION These results show that GSC-driving mechanisms induce a subset of genes that give rise to therapy-resistant GBM cells and suggests that miR-149-3p can be developed as a therapeutic for recurrent GBM.