HG-08 * DISRUPTING THE EPIGENETIC MODIFIER HMGA2 IN DIPG AND GBM INHIBITS TUMOR INVASION, GROWTH AND TUMORIGENICITY

Abstract

Diffuse intrinsic pontine glioma (DIPG) and glioblastoma (GBM) are lethal, incurable brain tumors with poor prognosis. Identifying and targeting novel molecular markers regulating tumor invasion and growth can lead to development of better therapies. HMGA2, a minor-groove DNA-binding protein, is a transcriptional modulator in normal and cancer stem cells. We hypothesized that HMGA2 contributes to pediatric high grade glioma invasion and tumorigenicity through its ability to alter the transcription of large numbers of genes. We found increased expression of HMGA2 in a subset of GBM and DIPG tumors by western blotting and immunohistochemistry. We confirmed this result in multiple patient-derived tumor cell lines, including 4 DIPG neurosphere cell lines. Lentiviral short hairpin RNA (shRNA)-mediated reduction of HMGA2 in GBM cells significantly reduced invasion in transwell assay and colony formation in soft agar assay (shHMGA2 vs. shControl, P < 0.01). Similarly, shRNA mediated suppression of HMGA2 in DIPG cell lines reduced proliferation as measured by BrdU incorporation, reduced invasion by transwell assay and increased apoptosis by cleaved caspase-3 (CC-3) immunofluorescence (shHMGA2 vs. shControl, P < 0.01). Pharmacological inhibition of HMGA proteins using the DNA minor-groove binding drug Netropsin significantly inhibited growth (BrdU assay) and increased apoptosis (CC-3 immunofluorescence) of GBM and DIPG cell lines (P < 0.01). Mice bearing orthotopic GBM xenograft cell lines transduced with HMGA2 shRNA lived longer (median survival = 108 days) compared to control shRNA (67.5 days, P < 0.0001 by log-rank analysis). Our results suggest an oncogenic role of HMGA2 in promoting DIPG and GBM invasion and growth, identifying HMGA2 as a potential therapeutic target in these devastating tumors. Netropsin or other minor groove binding agents may be effective therapeutics for pediatric high-grade gliomas.