Abstract 3031: HMGA2 promotes invasion and stemness in glioblastoma

Abstract

Abstract Glioblastoma Multiforme (GBM) causes the majority of brain tumor-related deaths in the United States. The high invasiveness of GBM prevents complete surgical resection, allowing tumor recurrence. The lack of curative treatment highlights a dire need to develop specific targeted therapeutics. Identifying and targeting novel molecular markers in glioma stem-like cells (GSCs), one of the major causes of tumor invasion and recurrence, could lead to development of better therapies. HMGA2, a non-histone transcriptional modulator, is a regulator of normal and cancer stem cells. The significance of HMGA2 as a potential therapeutic target in GBM has not been investigated. To elucidate the role of HMGA2 in GBM, we have used a combination of in vitro and in vivo techniques. We found increased HMGA2 expression in the mesenchymal subgroup of GBM tumors in the The Cancer Genome Atlas (TCGA) database and in a subset of primary human GBM tumors. HMGA2 is expressed in multiple patient-derived GBM neurosphere lines with increased expression in CD133+ neurospheres compared to CD133- neurospheres. Lentiviral short hairpin RNA (shRNA)-mediated reduction of HMGA2 significantly inhibited invasion of GBM neurosphere lines (040821, 62% reduction with HMGA2 shRNA vs. control shRNA, P<0.001) in transwell invasion assays. Conversely, lentiviral-mediated overexpression of HMGA2 in GBM neurosphere lines increased invasion (GBM1 and 040821, 100-130% increase with HMGA2 overexpression vs. control vector, P<0.001) in transwell invasion assays. In addition, overexpression of HMGA2 increased clonogenicity of GBM neurosphere lines in vitro in soft agar and methylcellulose colony formation assays (40-60% increase with HMGA2 overexpression vs. control vector, P<0.001). Importantly, log-rank analysis of Kaplan-Meier plots showed increased survival of mice injected with GBM neurosphere lines transduced with HMGA2 shRNA compared to control shRNA (P<0.05) in an in vivo, orthotopic, intracranial mouse xenograft model. To elucidate the molecular mechanism by which HMGA2 promotes invasion and stemness in GBM, we performed mRNA expression profiling on GBM neurosphere lines lentivirally transduced to express HMGA2 or empty vector control. We found increased CD44 expression in HMGA2-overexpressing GBM neurosphere lines compared to control. Together, our results suggest an oncogenic role of HMGA2 in promoting GBM tumorigenicity by increasing invasiveness and a stem cell-like state, thereby suggesting that HMGA2 is a potential therapeutic target in GBM. Citation Format: Harpreet Kaur, Marianne Hütt, Xing-gang Mao, Brent A. Orr, Charles G. Eberhart, Eric H. Raabe. HMGA2 promotes invasion and stemness in glioblastoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3031. doi:10.1158/1538-7445.AM2014-3031