Abstract 3124: Synergistic modulation of microRNAs for treatment of glioblastoma cancer initiating cells

Abstract Glioblastoma multiforme (GBM) is an aggressive and invasive brain tumor primarily found in adults. Survival outcomes after standard clinical treatment of GBM are poor due to the sub-population of GBMs, the cancer initiating cells (CICs). CICs are highly invasive and resistant to multimodal therapeutic treatment strategies. It has been shown that microRNAs (miRs) that modulate apoptotic signaling pathways are dysregulated in GBMs, particularly miRs 34a and 21. Our study investigated the therapeutic potential of modulating levels of the pro-apoptotic miR34a and anti-apoptotic miR21 in the CICs. To accomplish this, we complexed both miR34a and the anti-sense oligonucleotide inhibitor for miR21 (ASO21) to targeted cationic liposomes, as these can be systemically administered in vivo and extravasate through the leaky vasculature of the blood-brain barrier to reach the tumor. The isolated CICs overexpress epidermal growth factor receptor (EGFR). An EGFR peptide was custom synthesized that has a high binding affinity to the receptor and was used as the targeting ligand on the cationic liposomes. We analyzed the effect of miR34a and/or ASO21 on the CIC viability, senescence, and invasion. Our results demonstrate that after treatment with miR34a, ASO21, and combination of the two, the tumor viability decreased to 65%, 70%, and 45%, respectively as compared to the media control (100%). In addition, using β-galactosidase as an indicator for senescent cells, it was observed that the number of cells that were senescent increased. For the miR34a, ASO21, and the combination of the two, 40%, 23%, and 70%, respectively, of the cells were senescent, compared to the 4% of untreated cancer initiating cells. The number of CIC spheres formed was also significantly reduced, as cancer initiating cells treated with the combination had an average of 1125 spheres formed versus the media (untreated) of 2860 spheres formed, suggesting a decreased potential to form bulk tumors. Preliminary protein and gene profiling has demonstrated fold changes in pathway and migration markers Stat3, Reck, and Notch, as well as apoptosis markers Bax, PDCD4, and Caspase 3 for the treatment conditions compared to the medial control. Furthermore, our data demonstrates that the enhanced effect of the miR34a and ASO21 combination treatment had a synergistic effect compared to the individual treatments rather than additive. Therefore, this study demonstrates that modulating miR34a and 21 is a potential therapeutic strategy to induce apoptosis and senescence, and decrease migration in the difficult to treat GBM cancer initiating cells. Citation Format: Kimberly Ornell, Yuan Yin, Alexander Alexander Beliveau, Anjana Jain. Synergistic modulation of microRNAs for treatment of glioblastoma cancer initiating cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3124. doi:10.1158/1538-7445.AM2015-3124