John K. Park

Expression of Notch-1 and Its Ligands, Delta-Like-1 and Jagged-1, Is Critical for Glioma Cell Survival and Proliferation

The Notch family of proteins plays an integral role in determining cell fates, such as proliferation, differentiation, and apoptosis. We show that Notch-1 and its ligands, Delta-like-1 and Jagged-1, are overexpressed in many glioma cell lines and primary human gliomas. Immunohistochemistry of a primary human glioma tissue array shows the presence in the nucleus of the Notch-1 intracellular domain, indicating Notch-1 activation in situ. Down-regulation of Notch-1, Delta-like-1, or Jagged-1 by RNA interference induces apoptosis and inhibits proliferation in multiple glioma cell lines. In addition, pretreatment of glioma cells with Notch-1 or Delta-like-1 small interfering RNA significantly prolongs survival in a murine orthotopic brain tumor model. These results show, for the first time, the dependence of cancer cells on a single Notch ligand; they also suggest a potential Notch juxtacrine/autocrine loop in gliomas. Notch-1 and its ligands may present novel therapeutic targets in the treatment of glioma.

Scale to Predict Survival After Surgery for Recurrent Glioblastoma Multiforme

PURPOSE Despite initial treatment with surgical resection, radiotherapy, and chemotherapy, glioblastoma multiforme (GBM) virtually always recurs. Surgery is sometimes recommended to treat recurrence. In this study, we sought to devise a preoperative scale that predicts survival after surgery for recurrent glioblastoma multiforme. PATIENTS AND METHODS The preoperative clinical and radiographic data of 34 patients who underwent re-operation of recurrent GBM tumors were analyzed using Kaplan-Meier survival analysis and Cox proportional hazards regression modeling. The factors associated with decreased postoperative survival (P < .05) were used to devise a prognostic scale which was validated with a separate cohort of 109 patients. RESULTS The factors associated with poor postoperative survival were: tumor involvement of prespecified eloquent/critical brain regions (P = .021), Karnofsky performance status (KPS) < or = 80 (P = .030), and tumor volume > or = 50 cm(3) (P = .048). An additive scale (range, 0 to 3 points) comprised of these three variables distinguishes patients with good (0 points), intermediate (1 to 2 points), and poor (3 points) postoperative survival (median survival, 10.8, 4.5, and 1.0 months, respectively; P < .001). The scale identified three statistically distinct groups within the validation cohort as well (median survival, 9.2, 6.3, and 1.9 months, respectively; P < .001). CONCLUSION We devised and validated a preoperative scale that identifies patients likely to have poor, intermediate, and good relative outcomes after surgical resection of a recurrent GBM tumor. Application of this simple scale may be useful in counseling patients regarding their treatment options and in designing clinical trials.

A PDGF-Regulated Immediate Early Gene Response Initiates Neuronal Differentiation in Ventricular Zone Progenitor Cells

When exposed to platelet-derived growth factor (PDGF), uncommitted neuroepithelial cells from the developing cortex of embryonic day 14 (E14) rats develop into neurons. Outward signs of the neuronal phenotype are not observed for 4 days following exposure to PDGF. However, only a brief (2-3 hr) period of PDGF receptor activation is required to initiate neuronal development. During the window of receptor activation, RNA synthesis is essential, but protein synthesis is not. These observations indicate that specification of neuronal fate is mediated by an immediate early gene response.

Oligodendrocyte lineage genes (OLIG) as molecular markers for human glial brain tumors

The most common primary tumors of the human brain are thought to be of glial cell origin. However, glial cell neoplasms cannot be fully classified by cellular morphology or with conventional markers for astrocytes, oligodendrocytes, or their progenitors. Recent insights into central nervous system tumorigenesis suggest that novel molecular markers might be found among factors that have roles in glial development. Oligodendrocyte lineage genes (Olig1/2) encode basic helix–loop–helix transcription factors. In the rodent central nervous system, they are expressed exclusively in oligodendrocytes and oligodendrocyte progenitors, and Olig1 can promote formation of an chondroitin sulfate proteoglycon-positive glial progenitor. Here we show that human OLIG genes are expressed strongly in oligodendroglioma, contrasting absent or low expression in astrocytoma. Our data provide evidence that neoplastic cells of oligodendroglioma resemble oligodendrocytes or their progenitor cells and may derive from cells of this lineage. They further suggest the diagnostic potential of OLIG markers to augment identification of oligodendroglial tumors.

Presentation and Management of Chiari I Malformation in Children

To determine the efficacy of operative treatment for children with Chiari I malformation, the medical records and magnetic resonance imaging (MRI) studies of 68 consecutive patients cared for at The Childrens Hospital, Boston, Mass., USA, from December, 1988 to November, 1996 were retrospectively reviewed. All patients underwent suboccipital craniectomy, C1 laminectomy, and dural grafting. Bipolar coagulation to shrink and reduce the volume of the cerebellar tonsils was carried out in 40 patients. In 32 of 40 patients with associated syringomyelia, the procedure included placement of a IVth ventricle to cervical subarachnoid space shunt. Twenty-three patients with syringomyelia also had plugging of the obex. There was no operative mortality. Morbidity included a 22% incidence of nausea/vomiting and a 10% incidence of headache, both limited to the immediate postoperative period. Within the first postoperative month, all patients or their parents reported clear improvement in their presenting symptoms and 93% were found to have clear improvement in their presenting signs. In follow-up periods of 6-70 months, all patients had continued unequivocal symptom improvement and all patients were found on examination to have clear improvement in neurological signs. In patients with syringomyelia, MRI studies carried out at least 6 months postoperatively revealed near total or total syrinx resolution in 80% of the cases. This study demonstrates that a standard bony and dural decompression of the foramen magnum region with modifications designed to maximize the restoration of CSF circulation across the foramen magnum is a safe, effective operative treatment for Chiari I malformation in children.

Expression of Interleukin-13 Receptor α2 in Glioblastoma Multiforme: Implications for Targeted Therapies

Glioblastoma multiforme is the most common primary malignant brain tumor and despite treatment with surgery, radiation, and chemotherapy, the median survival of patients with glioblastoma multiforme is approximately 1 year. Glioblastoma multiforme explants and cell lines have been reported to overexpress the interleukin-13 receptor alpha2 subunit (IL13Ralpha2) relative to nonneoplastic brain. Based on this finding, a recombinant cytotoxin composed of IL13 ligand and a truncated form of Pseudomonas aeruginosa exotoxin A (IL13-PE38QQR) was developed for the targeted treatment of glioblastoma multiforme tumors. In a recently completed phase III clinical trial, however, IL13-PE38QQR was found to be no more effective than an existing therapy in prolonging survival. To determine possible explanations for this result, we analyzed the relative expression levels of IL13Ralpha2 in glioblastoma multiforme and nonneoplastic brain specimens using publicly available oligonucleotide microarray databases, quantitative real-time reverse transcription PCR, and immunohistochemical staining. Increased expression of the IL13Ralpha2 gene relative to nonneoplastic brain was observed in 36 of 81 (44%) and 8 of 17 (47%) tumor specimens by microarray and quantitative real-time reverse transcription PCR analyses, respectively. Immunohistochemical staining of tumor specimens showed highly variable expression of IL13Ralpha2 protein both within and across specimens. These data indicate that prescreening of subjects may be of benefit in future trials of IL13Ralpha2 targeting therapies.

Experimental approaches for the treatment of malignant gliomas

Malignant gliomas, which include glioblastomas and anaplastic astrocytomas, are the most common primary tumors of the brain. Over the past 30 years, the standard treatment for these tumors has evolved to include maximal safe surgical resection, radiation therapy and temozolomide chemotherapy. While the median survival of patients with glioblastomas has improved from 6 months to 14.6 months, these tumors continue to be lethal for the vast majority of patients. There has, however, been recent substantial progress in our mechanistic understanding of tumor development and growth. The translation of these genetic, epigenetic and biochemical findings into therapies that have been tested in clinical trials is the subject of this review.

Differentiation of human and murine induced pluripotent stem cells to microglia-like cells

Microglia are resident inflammatory cells of the CNS and have important roles in development, homeostasis and a variety of neurologic and psychiatric diseases. Difficulties in procuring human microglia have limited their study and hampered the clinical translation of microglia-based treatments shown to be effective in animal disease models. Here we report the differentiation of human induced pluripotent stem cells (iPSC) into microglia-like cells by exposure to defined factors and co-culture with astrocytes. These iPSC-derived microglia have the phenotype, gene expression profile and functional properties of brain-isolated microglia. Murine iPSC-derived microglia generated using a similar protocol have equivalent efficacy to primary brain-isolated microglia in treatment of murine syngeneic intracranial malignant gliomas. The ability to generate human microglia facilitates the further study of this important CNS cell type and raises the possibility of their use in personalized medicine applications.

N-CoR pathway targeting induces glioblastoma derived cancer stem cell differentiation.

Nuclear receptor co-repressor (N-CoR) is a critical regulator of neural stem cell differentiation. Nuclear localization of N-CoR is a feature of undifferentiated neural stem cells and cytoplasmic translocation of N-CoR leads to astrocytic differentiation. Comparative proteomic analysis of microdissected glioblastoma multiforme (GBM) specimens and matched normal glial tissue reveals increased expression of N-CoR in GBM. In GBM primary cell cultures, tumor cells with nuclear localization of N-CoR demonstrate an undifferentiated phenotype, but are subject to astroglial differentiation upon exposure to agents promoting phosphorylation of N-CoR and its subsequent translocation to the cytoplasm. Treatment of glioma cell lines with a combination of retinoic acid and low-dose okadaic acid decreases the co-repressor effect of N-CoR and has a striking synergistic effect on growth inhibition. The identification of N-CoR in GBM provides insights into the tumorigenesis process and supports the development of differentiation-based therapeutic strategies.

Nitrosoureas Inhibit the Stathmin Mediated Migration and Invasion of Malignant Glioma Cells

Malignant gliomas are the most common primary intrinsic brain tumors and are highly lethal. The widespread migration and invasion of neoplastic cells from the initial site of tumor formation into the surrounding brain render these lesions refractory to definitive surgical treatment. Stathmin, a microtubule-destabilizing protein that mediates cell cycle progression, can also regulate directed cell movement. Nitrosoureas, traditionally viewed as DNA alkylating agents, can also covalently modify proteins such as stathmin. We therefore sought to establish a role for stathmin in malignant glioma cell motility, migration, and invasion and determine the effects of nitrosoureas on these cell movement-related processes. Scratch wound-healing recovery, Boyden chamber migration, Matrigel invasion, and organotypic slice invasion assays were performed before and after the down-regulation of cellular stathmin levels and in the absence and presence of sublethal nitrosourea ([1-(2-chloroethyl)-3-cyclohexyl-l-nitrosourea]; CCNU) concentrations. We show that decreases in stathmin expression lead to significant decreases in malignant glioma cell motility, migration, and invasion. CCNU, at a concentration of 10 micromol/L, causes similar significant decreases, even in the absence of any effects on cell viability. The direct inhibition of stathmin by CCNU is likely a contributing factor. These findings suggest that the inhibition of stathmin expression and function may be useful in limiting the spread of malignant gliomas within the brain, and that nitrosoureas may have therapeutic benefits in addition to their antiproliferative effects.