To date, there are at least two locations in the mammalian brain where new neurons are being born, one of which is the subgranular zone of the hippocampus. These newborn neurons are fully capable of integrating and functioning as part of the hippocampal circuitry, thereby improving performance on learning and memory tasks. Hippocampal neurogenesis may be modulated by different stimuli and treatments, such as brain-derived neurotrophic factor (BDNF). In the present study, BDNF vector is delivered into the entorhinal cortex. BDNF is anterogradely transported from the entorhinal cortex into the aged non- human primate hippocampus. Newborn cells are detected by use of 5-bromo-2'-deoxyuridine (BrdU). Neurogenesis was measured by the number of BrdU+ cells that colabeled with either a mature neuronal marker (NeuN) or an immature neuronal marker (DCX). It was determined that while BDNF gene delivery resulted in an increased trend of surviving cells, there was no difference in the number of these newborn cells that differentiate into neurons. While the rate of neurogenesis was unaffected by aging, there was an observed decline in the total number of BrdU+ cells colabeled with a neuronal marker as well as the total amount of DCX+ cells. There was, however, a large portion of the BrdU+ cells that remained unidentified. No BrdU+ cell was colocalized with glial fibrillary acidic protein (GFAP), present in astrocytes and neural progenitor cells (NPCs). Lastly, there was no effect of treatment on maturation of newborn neurons as measured by migration and branching of DCX+ cells

Glioblastoma multiforme (GBM) is a highly aggressive brain tumor, which displays innate resistance to multiple treatment modalities. Previous studies have shown that proteasome inhibition can be used as a strategy for treating this malignancy. Marizomib (NPI-0052) is a second generation irreversible proteasome inhibitor, which has a more lipophilic structure and has a broader and more prolonged inhibition profile for 20S proteasome activities compared to bortezomib and carfilzomib. While bortezomib and carfilzomib have only modest activity in gliomas, marizomib might potentially be a novel therapeutic strategy for primary brain tumors. In these studies, we investigated the in vitro activities of marizomib in primary glioma cultures, neural stem/progenitor cells (NSC) and as well as in established human malignant glioma lines. The effect of marizomib on cell proliferation, proteasome activity, motility, apoptosis and Reactive Oxygen Species (ROS) were evaluated in glioma cell lines. The sensitivities varied in function of the pathology of the tumor, with the malignant glioma stem-like cells being the most severely affected, in contrast with the low-grade glioma and NSC-derived cultures. Marizomib inhibited the proliferation of U251-MG and D54-MG cell lines with a half maximal effective concentration (EC50) of 52nM and 20nM respectively, along with a significant decrease in cell migration and invasion. Marizomib treatment of human glioma cells was associated with increased ROS production and apoptosis, along with activation of caspase-3 and cleavage of PARP. Those effects of marizomib can be suppressed by exposure to the ROS quenching agent N-acetyl cysteine (NAC). These preclinical studies demonstrate a significant anti-glioma effect of marizomib. Marizomib has relatively little effect on neural stem/progenitor cells suggesting minimal neurotoxicity. But importantly, unlike bortezomib and carfilzomib, marizomib can cross the blood brain barrier. Additional research into the use of marizomib in malignant gliomas orthotropic models is in progress and will be presented during the meeting.

Retaspimycin hydrochloride (IPI-504), an Hsp90 (heat shock protein 90) inhibitor, has shown activity in multiple preclinical cancer models, such as lung, breast and ovarian cancers. However, its biological effects in gliomas and normal brain derived cellular populations remain unknown. In this study, we profiled the expression pattern of Hsp90α/β mRNA in stable glioma cell lines, multiple glioma-derived primary cultures and human neural stem/progenitor cells. The effects of IPI-504 on cell proliferation, apoptosis, motility and expression of Hsp90 client proteins were evaluated in glioma cell lines. In vivo activity of IPI-504 was investigated in subcutaneous glioma xenografts. Our results showed Hsp90α and Hsp90β expression levels to be patient-specific, higher in high-grade glioma-derived primary cells than in low-grade glioma-derived primary cells, and strongly correlated with CD133 expression and differentiation status of cells. Hsp90 inhibition by IPI-504 induced apoptosis, blocked migration and invasion, and significantly decreased epidermal growth factor receptor levels, mitogen-activated protein kinase and/or Akt activities, and secretion of vascular endothelial growth factor in glioma cell lines. In vivo study showed that IPI-504 could mildly attenuate tumor growth in immunocompromised mice. These findings suggest that targeting Hsp90 by IPI-504 has the potential to become an active therapeutic strategy in gliomas in a selective group of patients, but further research into combination therapies is still needed.