HGG-06. CHARACTERIZATION OF THE EFFECT OF THE ORAL IRON-MIMETIC GALLIUM MALTOLATE ON PEDIATRIC GLIOBLASTOMA GROWTH IN VIVO

BACKGROUND: Glioblastoma (GBM) is a highly aggressive CNS tumor that is associated with poor outcome. This dire prognosis is due in part to its poor response to the limited treatment options available. Iron and iron proteins play a key role in the growth of brain tumors, with our published studies showing that the ferrobiology of adult GBM can be exploited for therapeutic purposes. Here, we further elucidate the inhibitory effects of oral gallium maltolate (GaM) in pediatric GBM in vivo. METHODS: Pediatric SJ-GBM2 cells were stereotactically implanted into the right striatum of male athymic rats. Advanced MR imaging at 9.4T was carried out weekly starting two weeks after implantation. Daily oral GaM (50mg/kg) or vehicle were provided on tumor confirmation. Longitudinal advanced MRI parameters were processed for enhancing tumor ROIs in OsiriX 8.5.1 (lite) with Imaging Biometrics Software (Imaging Biometrics LLC). Statistical analyses included Kaplan-Meier survival plots, linear mixed model comparisons, and t-statistic for slopes comparison. RESULTS: The sensitivity of the in vivo pediatric GBM xenografts to GaM was consistent with our previous in vitro work. Median overall survival was 21 days in the controls and 49 days in the treatment group (p=0.014). GaM-treated xenograft tumors grew significantly slower than control tumors (p=0.031). Histologically, xenograft tumors recapitulated the aggressive growth features of clinical specimens, such as invasive margins. Unlike adult GBM xenografts in our previous studies, pediatric GBM xenografts did not exhibit vessel normalization or a reduction in pro-angiogenic markers in response to GaM. Additionally, MIB-1% (p=0.6583) and mitotic index (p=0.7097) were not affected by treatment. Yet, transferrin receptor and H-ferritin expression patterns in GaM-treated tumors suggested cellular iron deprivation. CONCLUSION: Monotherapy with GaM provides a significant survival benefit in pediatric GBM, and further studies are planned to optimize the benefit of GaM in pediatric GBM.