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1.  Where are we now? And where are we going? A report from the Accelerate Brain Cancer Cure (ABC2) Low-grade Glioma Research Workshop 
Neuro-Oncology  2013;16(2):173-178.
Diffuse gliomas consist of both low- and high-grade varieties, each with distinct morphological and biological features. The often extended periods of relative indolence exhibited by low-grade gliomas (LGG; WHO grade II) differ sharply from the aggressive, rapidly fatal clinical course of primary glioblastoma (GBM; WHO grade IV). Nevertheless, until recently, the molecular foundations underlying this stark biological contrast between glioma variants remained largely unknown. The discoveries of distinctive and highly recurrent genomic and epigenomic abnormalities in LGG have both informed a more accurate classification scheme and pointed to viable avenues for therapeutic development. As such, the field of neuro-oncology now seems poised to capitalize on these gains to achieve significant benefit for LGG patients. This report will briefly recount the proceedings of a workshop held in January 2013 and hosted by Accelerate Brain Cancer Cure (ABC2) on the subject of LGG. While much of the meeting covered recent insights into LGG biology, its focus remained on how best to advance the clinical management, whether by improved preclinical modeling, more effective targeted therapeutics and clinical trial design, or innovative imaging technology.
PMCID: PMC3895389  PMID: 24305708
clinical trials; genomics; low-grade glioma; personalized medicine
2.  Children's Oncology Group's 2013 Blueprint for Research: Central Nervous System Tumors 
Pediatric blood & cancer  2012;60(6):1022-1026.
In the US, approximately 2,500 children are diagnosed annually with brain tumors. Their survival ranges from >90% to <10%. For children with medulloblastoma, the most common malignant brain tumor, 5-year survival ranges from >80% (standard-risk) to 60% (high-risk). For those with high-grade gliomas (HGGs) including diffuse intrinsic pontine gliomas, 5-year survival remains <10%. Sixty-five percent patients with ependymoma are cured after surgery and radiation therapy depending on the degree of resection and histopathology of the tumor. Phase II trials for brain tumors will investigate agents that act on cMET, PDGFRA, or EZH2 in HGG, DIPG, or medulloblastoma, respectively. Phase III trials will explore risk-based therapy stratification guided by molecular and clinical traits of children with medulloblastoma or ependymoma.
PMCID: PMC4184243  PMID: 23255213
ependymoma; high-grade glioma and diffuse intrinsic pontine glioma; medulloblastoma
3.  Purged versus non-purged peripheral blood stem-cell transplantation for high-risk neuroblastoma (COG A3973): a randomised phase 3 trial 
The lancet oncology  2013;14(10):999-1008.
Myeloablative chemoradiotherapy and immunomagnetically purged autologous bone marrow transplantation has been shown to improve outcome for patients with high-risk neuroblastoma. Currently, peripheral blood stem cells (PBSC) are infused after myeloablative therapy, but the effect of purging is unknown. We did a randomised study of tumour-selective PBSC purging in stem-cell transplantation for patients with high-risk neuroblastoma.
Between March 16, 2001, and Feb 24, 2006, children and young adults (<30 years) with high-risk neuroblastoma were randomly assigned at diagnosis by a web-based system (in a 1:1 ratio) to receive either nonpurged or immunomagnetically purged PBSC. Randomisation was done in blocks stratified by International Neuroblastoma Staging System stage, age, MYCN status, and International Neuroblastoma Pathology classification. Patients and treating physicians were not masked to treatment assignment. All patients were treated with six cycles of induction chemotherapy, myeloablative consolidation, and radiation therapy to the primary tumour site plus metaiodobenzylguanidine avid metastases present before myeloablative therapy, followed by oral isotretinoin. PBSC collection was done after two induction cycles. For purging, PBSC were mixed with carbonyl iron and phagocytic cells removed with samarium cobalt magnets. Remaining cells were mixed with immunomagnetic beads prepared with five monoclonal antibodies targeting neuroblastoma cell surface antigens and attached cells were removed using samarium cobalt magnets. Patients underwent autologous stem-cell transplantation with PBSC as randomly assigned after six cycles of induction therapy. The primary endpoint was event-free survival and was analysed by intention-to-treat. The trial is registered with, number NCT00004188.
495 patients were enrolled, of whom 486 were randomly assigned to treatment: 243 patients to receive non-purged PBSC and 243 to received purged PBSC. PBSC were collected from 229 patients from the purged group and 236 patients from the non-purged group, and 180 patients from the purged group and 192 from the non-purged group received transplant. 5-year event-free survival was 40% (95% CI 33–46) in the purged group versus 36% (30–42) in the non-purged group (p=0·77); 5-year overall survival was 50% (95% CI 43–56) in the purged group compared with 51% (44–57) in the non-purged group (p=0·81). Toxic deaths occurred in 15 patients during induction (eight in the purged group and seven in the non-purged group) and 12 during consolidation (eight in the purged group and four in the non-purged group). The most common adverse event reported was grade 3 or worse stomatitis during both induction (87 of 242 patients in the purged group and 93 of 243 patients in the non-purged group) and consolidation (131 of 177 in the purged group vs 145 of 191 in the non-purged group). Serious adverse events during induction were grade 3 or higher decreased cardiac function (four of 242 in the purged group and five of 243 in the non-purged group) and elevated creatinine (five of 242 in the purged group and six of 243 non-purged group) and during consolidation were sinusoidal obstructive syndrome (12 of 177 in the purged group and 17 of 191 in the non-purged group), acute vascular leak (11 of 177 in the purged group and nine of 191 in the non-purged group), and decreased cardiac function (one of 177 in the purged group and four of 191 in the non-purged group).
Immunomagnetic purging of PBSC for autologous stem-cell transplantation did not improve outcome, perhaps because of incomplete purging or residual tumour in patients. Non-purged PBSC are acceptable for support of myeloablative therapy of high-risk neuroblastoma.
National Cancer Institute and Alex’s Lemonade Stand Foundation.
PMCID: PMC3963485  PMID: 23890779
4.  PDGFRA amplification is common in pediatric and adult high-grade astrocytomas and identifies a poor prognostic group in IDH1 mutant glioblastoma 
High-grade astrocytomas (HGAs), corresponding to WHO grades III (AA) and IV (GBM), are biologically aggressive and their molecular classification is increasingly relevant to clinical management. PDGFRA amplification is common in HGAs, although its prognostic significance remains unclear. Using fluorescence in situ hybridization (FISH), the most sensitive technique for detecting PDGFRA copy number gains, we determined PDGFRA amplification status in 123 pediatric and 263 adult HGAs. A range of PDGFRA FISH patterns were identified and cases were scored as non-amplified (normal and polysomy) or amplified (low-level and high-level). PDGFRA amplification was frequent in pediatric (29.3%) and adult (20.9%) tumors. Amplification was not prognostic in pediatric HGAs. In adult tumors diagnosed initially as GBM, the presence of combined PDGFRA amplification and IDH1R132H mutation was a significant independent prognostic factor (p=0.01). In HGAs, PDGFRA amplification is common and can manifest as high-level and focal or low-level amplifications. Our data indicate that the latter is more prevalent than previously reported with copy number averaging techniques. To our knowledge, this is the largest survey of PDGFRA status in adult and pediatric HGAs and suggests PDGFRA amplification increases with grade and is associated with a less favorable prognosis in IDH1 mutant de novo GBMs.
PMCID: PMC3715570  PMID: 23438035
PDGFRA; astrocytoma; FISH; IDH1; isocitrate dehydrogenase 1; prognosis
5.  Risk of First and Recurrent Stroke in Childhood Cancer Survivors treated with Cranial and Cervical Radiation Therapy 
Radiation therapy increases stroke risk in pediatric cancer patients, but risk of stroke recurrence in this population remains unknown. In a retrospective cohort study, we assessed rates and predictors of first and recurrent stroke in patients treated with cranial irradiation (CRT) and/or cervical irradiation ≤ 18 years of age.
We performed chart abstraction (n=383) and phone interviews (n=104) to measure first and recurrent stroke in 383 patients who received CRT and/or cervical radiation at a single institution between1980–2009. Stroke was defined as a physician diagnosis and symptoms consistent with stroke. Incidence of first-stroke was number of first-strokes per person-years of observation after radiation. We used survival analysis techniques to determine cumulative incidence of first and recurrent stroke.
Among 325 subjects with sufficient follow-up data, we identified 19 first-strokes (13 ischemic, 4 hemorrhagic, 2 unknown sub-type) occurring at a median age of 24 years (Interquartile range (IQR) 17–33 years) in patients treated with CRT. Imaging was reviewed when available (n=13) and the stroke was confirmed in 12. Overall rate of first-stroke was 625 (95% CI 378–977) per 100,000 person-years. The cumulative incidence of first stroke was 2% (95% CI 0.01–5.3%) at 5 years and 4% (95% C.I. 2.0–8.4%) at 10 years post irradiation. With each 100cGy increase in the radiation dose, the stroke hazard increased by 5% (Hazard ratio = 1.05; 95% CI 1.01–1.09; p=0.02). We identified 6 recurrent strokes; 5 had available imaging that confirmed the stroke. Median time to recurrence was 15 months (IQR 6 months–3.2 years) after first-stroke. The cumulative incidence of recurrent stroke was 38% (95% CI 17–69%) at 5 years and 59% (95% CI 27–92%) at 10 years post first-stroke.
CRT puts childhood cancer survivors at high risk of both first and recurrent stroke. Stroke prevention strategies for these survivors are needed.
PMCID: PMC3696632  PMID: 23623405
6.  The superiority of conservative resection and adjuvant radiation for craniopharyngiomas 
Journal of neuro-oncology  2012;108(1):10.1007/s11060-012-0806-7.
The purpose of this study is to evaluate the roles of resection extent and adjuvant radiation in the treatment of craniopharyngiomas. We reviewed the records of 122 patients ages 11–52 years who received primary treatment for craniopharyngioma between 1980 and 2009 at the University of California, San Francisco (UCSF). Primary endpoints were progression free survival (PFS) and overall survival (OS). Secondary endpoints were development of panhypopituitarism, diabetes insipidus (DI), and visual field defects. Of 122 patients, 30 (24%) were treated with gross total resection (GTR) without radiation therapy (RT), 3 (3%) with GTR + RT, 41 (33.6%) with subtotal resection (STR) without RT, and 48 (39.3%) with STR + RT. Median age at diagnosis was 30 years, with 46 patients 18 years or younger. Median follow-up for all patients was 56.4 months (interquartile range 18.9–144.2 months) and 47 months (interquartile range 12.3–121.8 months) for the 60 patients without progression. Fifty six patients progressed, 10 have died, 6 without progression. Median PFS was 61.1 months for all patients. PFS rate at 2 years was 61.5% (95% CI: 52.1–70.9). OS rate at 10 years was 91.1% (95% CI 84.3–97.9). There was no significant difference in PFS and OS between patients treated with GTR vs. STR + XRT (PFS; p = 0.544, OS; p = 0.735), but STR alone resulted in significantly shortened PFS compared to STR + RT or GTR (p < 0.001 for both). STR was associated with significantly shortened OS compared to STR + RT (p = 0.050) and trended to shorter OS compared to GTR (p = 0.066). GTR was associated with significantly greater risk of developing DI (56.3 vs. 13.3% with STR + XRT, p < 0.001) and panhypopituitarism (54.8 vs. 26.7% with STR + XRT, p = 0.014). In conclusion, for patients with craniopharyngioma, STR + RT may provide superior clinical outcome, achieving better disease control than STR and limiting side effects associated with aggressive surgical resection.
PMCID: PMC3879154  PMID: 22350375
Craniopharyngioma; Surgical resection; Radiation therapy; Adult; Pediatric
8.  Toward an Improved Understanding of the Ionizing Radiation Induced DNA Damage/Response Networks in Human Malignancies 
Frontiers in Oncology  2014;4:335.
PMCID: PMC4255519  PMID: 25538888
ionizing radiation; ionizing radiation induced DNA damage; DNA damage; radiation; editorial
9.  Tumor dosimetry using [124I]m-iodobenzylguanidine microPET/CT for [131I]m- iodobenzylguanidine treatment of neuroblastoma in a murine xenograft model 
[124I]m-iodobenzylguanidine (124I-mIBG) provides a quantitative tool for pretherapy tumor imaging and dosimetry when performed before [131I]m-iodobenzylguanidine (131I-mIBG) targeted radionuclide therapy of neuroblastoma. 124I (T1/2=4.2d) has a comparable half-life to that of 131I (T1/2=8.02d), and can be imaged by PET for accurate quantification of the radiotracer distribution. We estimated expected radiation dose in tumors from 131I-mIBG therapy using 124I-mIBG microPET/CT imaging data in a murine xenograft model of neuroblastoma transduced to express high levels of the human norepinephrine transporter (hNET).
In order to enhance mIBG uptake for in vivo imaging and therapy, NB 1691-luciferase (NB1691) human neuroblastoma cells were engineered to express high levels of hNET protein by lentiviral transduction (NB1691-hNET). Both NB1691 and NB1691-hNET cells were implanted subcutaneously and into renal capsules in athymic mice. 124I-mIBG (4.2–6.5 MBq) was administered intravenously for microPET/CT imaging at 5 time points over 95 hours (0.5, 3–5, 24, 48, and 93–95 h median time points). In vivo biodistribution data in normal organs, tumors, and whole-body were collected from reconstructed PET images corrected for photon attenuation using the CT-based attenuation map. Organ and tumor dosimetry were determined for 124I-mIBG. Dose estimates for 131I-mIBG were made, assuming the same in vivo biodistribution as 124I-mIBG.
All NB1691-hNET tumors had significant uptake and retention of 124I-mIBG, whereas unmodified NB1691 tumors did not demonstrate quantifiable mIBG uptake in vivo, despite in vitro uptake. 124I-mIBG with microPET/CT provided an accurate 3-dimensional tool for estimating the radiation dose that would be delivered with 131I-mIBG therapy. For example, in our model system, we estimated that the administration of 131I-mIBG in the range of 52.8 – 206 MBq would deliver 20 Gy to tumors.
The overexpression of hNET was found to be critical for 124I-mIBG uptake and retention in vivo. The quantitative 124I-mIBG PET/CT is a promising new tool to predict tumor radiation doses with 131I-mIBG therapy of neuroblastoma. This methodology may be applied to tumor dosimetry of 131I-mIBG therapy in human subjects using 124I-mIBG pretherapy PET/CT data.
PMCID: PMC3369020  PMID: 22382618
neuroblastoma; m-iodobenzylguanidine; iodine-124; iodine-131; PET/CT; animal model; radiation dosimetry
10.  Molecular targets and mechanisms of radiosensitization using DNA damage response pathways 
The cellular reaction to genomic instability includes a network of signal transduction pathways collectively referred to as the DNA damage response (DDR). Activated by a variety of DNA lesions, the DDR orchestrates cell cycle arrest and DNA repair, and initiates apoptosis in instances where damage cannot be repaired. As such, disruption of the DDR increases the prevalence of DNA damage secondary to incomplete repair, and in doing so, enhances radiation-induced cytotoxicity. This article describes the molecular agents and their targets within DDR pathways that sensitize cells to radiation. Moreover, it reviews the therapeutic implications of these compounds, provides an overview of relevant clinical trials and offers a viewpoint on the evolution of the field in the years to come.
PMCID: PMC3635474  PMID: 23414472
apoptosis; cell cycle; DNA damage response; ionizing radiation; radioprotection; radiosensitization
11.  Radiation-induced gliomas 
Expert review of neurotherapeutics  2009;9(10):10.1002/pmic.200800802.
Radiation-induced gliomas represent a relatively rare but well-characterized entity in the neuro-oncologic literature. Extensive retrospective cohort data in pediatric populations after therapeutic intracranial radiation show a clearly increased risk in glioma incidence that is both patient age- and radiation dose/volume-dependent. Data in adults are more limited but show heightened risk in certain groups exposed to radiation. In both populations, there is no evidence linking increased risk associated with routine exposure to diagnostic radiation. At the molecular level, recent studies have found distinct genetic differences between radiation-induced gliomas and their spontaneously-occurring counterparts. Clinically, there is understandable reluctance on the part of clinicians to re-treat patients due to concern for cumulative neurotoxicity. However, available data suggest that aggressive intervention can lead to improved outcomes in patients with radiation-induced gliomas.
PMCID: PMC3830919  PMID: 19831840
glioblastoma; radiation; secondary malignancy; gliomas; pediatric neuro-oncology
12.  PTEN promoter methylation and activation of the PI3K/Akt/mTOR pathway in pediatric gliomas and influence on clinical outcome 
Neuro-Oncology  2012;14(9):1146-1152.
The signaling pathways that underlie the pathogenesis of pediatric gliomas are poorly understood. We characterized the PI3K/Akt/mTOR pathway in pediatric gliomas of all grades. Using immunohistochemistry, we assessed activation of the PI3K/Akt/mTOR pathway by evaluating the downstream signaling molecules phospho(p)-S6, phospho(p)-4BP1, and phospho(p)-PRAS40; PTEN; and PTEN promoter methylation, as well as the MIB labeling index. We correlated these findings with the clinical outcomes of 48 children with gliomas. Eighty percent of high-grade gliomas (12/15) showed activation of the PI3K/Akt/mTOR pathway based on p-S6 and p-4EBP1 expression. The majority of high-grade gliomas were negative for PTEN expression (10/15), and 50% had PTEN promoter methylation (grade III: 2/4; grade IV: 3/6). Low-grade gliomas demonstrated PI3K/Akt/mTOR pathway activation in 14/32 (43.8%) by p-S6 and 16/32 (50%) by p-4EBP1. Over 50% of grade I (6/11) and almost all grade II tumors (6/7) showed PTEN promoter methylation. Tumor grade correlated negatively with PTEN expression and positively with expression of p-S6 and p-4EBP1 (PTEN: P = .0025; pS6: P = .0075; p-4EBP1: P = .0066). There was a trend toward inverse correlation of methylation of the PTEN promoter with expression of PTEN protein (P= .0990) and direct correlation of expression of p-S6 and p-4EBP1 with poorer clinical outcome, as measured by progression-free survival (p-S6: P= .0874; p-4EBP1: P= .0475). Tumors with no PTEN expression had a higher MIB labeling index (P= .007). The majority of pediatric gliomas show activation of the PI3K/Akt/mTOR pathway, with methylation of the PTEN promoter occurring commonly in these tumors.
PMCID: PMC3424210  PMID: 22753230
pediatric gliomas; PI3K/Akt/mTOR; PTEN promoter methylation
13.  Poly (ADP-Ribose) Polymerase Inhibitor MK-4827 together with Radiation as a Novel Therapy for Metastatic Neuroblastoma 
Anticancer research  2013;33(3):755-762.
To assess poly (ADP-ribose) polymerase (PARP) inhibitor MK-4827 together with radiation for the treatment of neuroblastoma.
Material and Methods
Clonogenic survival assays were used to assess MK-4827, radiation and combination thereof in four neuroblastoma cell lines. In vivo efficacy was tested in a murine xenograft model of metastatic neuroblastoma. In vivo targeted inhibition and biological effects included measurement of cleaved caspase-3, gamma-H2AX, and Ki 67 by immunohistochemistry (IHC) and poly-ADP-ribose by Enzyme-Linked Immunosorbent Assay.
Treatment of neuroblastoma cell lines reduced clonogenicity and resulted in additive effects with radiation. In vivo treatment with MK-4827 and radiation prolonged survival (p<0.01) compared to single modalities. In vivo superiority of MK-4827 plus radiation was further documented by significant elevations of cleaved caspase-3 and γ-H2AX in tumors from the combination group compared to single modality cohorts.
Combination of MK-4827 and radiation might provide effective therapy for children with high-risk neuroblastoma.
PMCID: PMC3684561  PMID: 23482742
14.  DTI Assessment of the Brainstem White Matter Tracts in Pediatric BSG Before and After Therapy: A Report from the Pediatric Brain Tumor Consortium 
To assess changes in apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values in brainstem gliomas in children and to observe the temporal evolution of changes in the white matter tracts following therapy using diffusion tensor imaging (DTI) analysis.
Serial ADC and FA measurements were obtained in 3 patients with newly diagnosed brainstem gliomas on two approved treatment protocols. Values were compared with a set of normative ADC, FA, and eigenvalues of age-matched children of the corticospinal, transverse pontine and medial lemniscal tracts. Fiber tracking of the tracts coursing through the brainstem was performed using standard diffusion tractography analysis.
We found increased ADC values within tumor at baseline compared to age-matched controls, with subsequent drop following treatment and subsequent increase with recurrence. Correspondingly, FA values were reduced at presentation, but transiently recovered during the phase of tumor response to treatment, and finally decreased significantly during tumor progression. These changes were concordant with the tractography analysis of white matter tracts in the brainstem. Based on these results, we suggest that initial changes in ADC and FA values reflects tract infiltration by tumor, but not complete disruption, whereas tumor progression results in complete loss of anisotropy possibly due to tract disruption.
Serial changes in ADC and FA values and tractography data in pediatric brainstem gliomas suggest initial tumor infiltration, with transient improvement on treatment and subsequent loss of tract anisotropy during tumor progression. This technique may have potential use in assessing response to treatment regimens for pediatric brainstem gliomas.
PMCID: PMC3598014  PMID: 21052693
MRI; diffusion tensor imaging; brainstem glioma; pediatrics
15.  Reduced phosphocholine and hyperpolarized lactate provide magnetic resonance biomarkers of PI3K/Akt/mTOR inhibition in glioblastoma 
Neuro-Oncology  2011;14(3):315-325.
The phosphatidylinositol-3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway is activated in more than88% of glioblastomas (GBM). New drugs targeting this pathway are currently in clinical trials. However, noninvasive assessment of treatment response remains challenging. By using magnetic resonance spectroscopy (MRS), PI3K/Akt/mTOR pathway inhibition was monitored in 3 GBM cell lines (GS-2, GBM8, and GBM6; each with a distinct pathway activating mutation) through the measurement of 2 mechanistically linked MR biomarkers: phosphocholine (PC) and hyperpolarized lactate.31P MRS studies showed that treatment with the PI3K inhibitor LY294002 induced significant decreases in PC to 34 %± 9% of control in GS-2 cells, 48% ± 5% in GBM8, and 45% ± 4% in GBM6. The mTOR inhibitor everolimus also induced a significant decrease in PC to 62% ± 14%, 57% ± 1%, and 58% ± 1% in GS-2, GBM8, and GBM6 cells, respectively. Using hyperpolarized 13C MRS, we demonstrated that hyperpolarized lactate levels were significantly decreased following PI3K/Akt/mTOR pathway inhibition in all 3 cell lines to 51% ± 10%, 62% ± 3%, and 58% ± 2% of control with LY294002 and 72% ± 3%, 61% ± 2%, and 66% ± 3% of control with everolimus in GS-2, GBM8, and GBM6 cells, respectively. These effects were mediated by decreases in the activity and expression of choline kinase α and lactate dehydrogenase, which respectively control PC and lactate production downstream of HIF-1. Treatment with the DNA damaging agent temozolomide did not have an effect on either biomarker in any cell line. This study highlights the potential of PC and hyperpolarized lactate as noninvasive MR biomarkers of response to targeted inhibitors in GBM.
PMCID: PMC3280799  PMID: 22156546
glioblastoma (GBM); hyperpolarized lactate; magnetic resonance spectroscopy (MRS); phosphocholine (PC); PI3K/Akt/mTOR pathway
16.  The Combination of Novel Targeted Molecular Agents and Radiation in the Treatment of Pediatric Gliomas 
Frontiers in Oncology  2013;3:110.
Brain tumors are the most common solid pediatric malignancy. For high-grade, recurrent, or refractory pediatric brain tumors, radiation therapy (XRT) is an integral treatment modality. In the era of personalized cancer therapy, molecularly targeted agents have been designed to inhibit pathways critical to tumorigenesis. Our evolving knowledge of genetic aberrations in pediatric gliomas is being exploited with the use of specific targeted inhibitors. These agents are additionally being combined with XRT to increase the efficacy and duration of local control. In this review, we discuss novel agents targeting three different pathways in gliomas, and their potential combination with XRT. BRAF is a serine/threonine kinase in the RAS/RAF/MAPK kinase pathway, which is integral to cellular division, survival, and metabolism. Two-thirds of pilocytic astrocytomas, a low-grade pediatric glioma, contain a translocation within the BRAF gene called KIAA1549:BRAF that causes an overactivation of the MEK/MAPK signaling cascade. In vitro and in vivo data support the use of MEK or mammalian target of rapamycin (mTOR) inhibitors in low-grade gliomas expressing this translocation. Additionally, 15–20% of high-grade pediatric gliomas express BRAF V600E, an activating mutation of the BRAF gene. Pre-clinical in vivo and in vitro data in BRAF V600E gliomas demonstrate dramatic cooperation between XRT and small molecule inhibitors of BRAF V600E. Another major signaling cascade that plays a role in pediatric glioma pathogenesis is the PI3-kinase (PI3K)/mTOR pathway, known to be upregulated in the majority of high- and low-grade pediatric gliomas. Dual PI3K/mTOR inhibitors are in clinical trials for adult high-grade gliomas and are poised to enter studies of pediatric tumors. Finally, many brain tumors express potent stimulators of angiogenesis that render them refractory to treatment. An analog of thalidomide, CC-5103 increases the secretion of critical cytokines of the tumor microenvironment, including IL-2, IFN-γ, TNF-α, and IL-10, and is currently being evaluated in clinical trials for the treatment of recurrent or refractory pediatric central nervous system tumors. In summary, several targeted inhibitors with radiation are currently under investigation in both translational bench research and early clinical trials. This review article summarizes the molecular rationale for, and the pre-clinical data supporting the combinations of these targeted agents with other anti-cancer agents and XRT in pediatric gliomas. In many cases, parallels are drawn to molecular mechanisms and targeted inhibitors of adult gliomas. We additionally discuss the potential mechanisms underlying the efficacy of these agents.
PMCID: PMC3650671  PMID: 23717811
pediatric gliomas; low-grade glioma; BRAFV600E; PI3K/AKT/mTOR; angiogenesis inhibitors; bevacizumab; lenalidomide
17.  Evaluation of 18F-FDG PET and MRI Associations in Pediatric Diffuse Intrinsic Brain stem Glioma: A Report from the Pediatric Brain Tumor Consortium 
To assess 18F-labeled 2-fluoro-2-deoxy-D-glucose (18F-FDG) uptake in children with a newly diagnosed diffuse intrinsic brainstem glioma (BSG) and to investigate associations with progression-free survival (PFS), overall survival (OS) and MRI indices.
Two Pediatric Brain Tumor Consortium (PBTC) therapeutic trials in children with newly diagnosed BSG were designed to test radiation therapy combined with molecularly targeted agents (PBTC-007: Phase I/II study of gefitinib; PBTC-014: Phase I/II study of tipifarnib). Baseline brain 18F-FDG PET scans were obtained in 40 children in these trials. Images were evaluated by consensus of two PET experts for intensity and uniformity of tracer uptake. Associations of 18F-FDG uptake intensity and uniformity with both PFS and OS were evaluated as well as associations with tumor MRI indices at baseline (tumor volume on FLAIR, baseline intratumoral enhancement, diffusion and perfusion values.
In the majority of children, BSG 18F-FDG uptake was less than gray matter uptake. Survival was poor irrespective of intensity of 18F-FDG uptake, with no association between intensity of 18F-FDG uptake and PFS or OS. However, hyperintense 18F-FDG uptake in tumor compared to gray matter suggested poorer survival rates. Patients with 18F-FDG uptake in ≥ 50% of the tumor had shorter PFS and OS compared to patients with 18F-FDG uptake in < 50% of tumor. There was some evidence that tumors with higher 18F-FDG uptake were more likely to show enhancement; and when the diffusion ratio was lower the uniformity of 18F- FDG uptake appeared higher.
Children with BSG where 18F-FDG uptake involves at least half the tumor appear to have inferior survival compared to children with uptake in <50% of tumor. A larger independent study is needed to verify this hypothesis. Intense tracer uptake in the tumors compared to gray matter suggests decreased survival. Higher 18F-FDG uptake within the tumor was associated with enhancement on MRI. Increased tumor cellularity as reflected by restricted MR diffusion may be associated with increased 18F-FDG uniformity throughout the tumor.
PMCID: PMC3526809  PMID: 21233173
pediatric; brainstem glioma; 18F-FDG PET; MRI; diffusion; enhancement; perfusion; brain tumor
18.  Response, Survival and Toxicity after 131I-MIBG Therapy for Neuroblastoma in Pre-Adolescents, Adolescents and Adults 
Cancer  2011;117(18):4286-4293.
Adolescent and adult patients with neuroblastoma appear to have a more indolent disease course but a lower survival than their younger counterparts. The majority of neuroblastoma tumors specifically accumulate the radiolabeled norepinephrine analogue 131I-metaiodobenzylguanidine (MIBG). 131I-MIBG has therefore become increasingly used as targeted radiotherapy for relapsed or refractory neuroblastoma. The aim of this study was to characterize the toxicity and activity of this therapy in older patients.
We performed a retrospective analysis of 39 consecutive patients ages 10 years and older with relapsed or refractory neuroblastoma who were treated with 131I-MIBG monotherapy at UCSF under Phase I, Phase II, and compassionate access protocols.
Sixteen patients were ≥18 years old at MIBG treatment initiation, whereas twenty-three were 10–17 years old. The median cumulative administered dose of 131I-MIBG was 17.8 mCi/kg. The majority of treatments led to grade 3 or 4 hematologic toxicities which were similar in frequency among age strata. Three patients subsequently developed hematologic malignancy or myelodysplasia. The overall rate of complete plus partial response was 46%. Patients ≥18 years old at time of first MIBG treatment had a significantly higher response rate compared to patients 10–17 years old (56% vs 39%, p=0.023). Median overall survival was 23 months with a trend toward longer overall survival for the ≥18 year old subgroup (p = 0.12).
Our findings suggest that 131I-MIBG is a highly effective salvage agent for adolescents and adults with neuroblastoma.
PMCID: PMC3125487  PMID: 21387264
neuroblastoma; adult; adolescent; MIBG; radiopharmaceutical
19.  Hepatocellular carcinoma: natural history, current management, and emerging tools 
Hepatocellular carcinoma (HCC) is the most common primary liver tumor and represents the third-leading cause of cancer-related death in the world. The incidence of HCC continues to increase worldwide, with a unique geographic, age, and sex distribution. The most important risk factor associated with HCC is liver cirrhosis, with the majority of cases caused by chronic infection with hepatitis B (HBV) and C (HCV) viruses and alcohol abuse, although nonalcoholic fatty liver disease is emerging as an increasingly important cause. Primary prevention in the form of HBV vaccination has led to a significant decrease in HBV-related HCC, and initiation of antiviral therapy appears to reduce the incidence of HCC in patients with chronic HBV or HCV infection. Additionally, the use of ultrasonography enables the early detection of small liver tumors and forms the backbone of recommended surveillance programs for patients at high risk for the development of HCC. Cross-sectional imaging studies, including computed tomography and magnetic resonance imaging, represent further noninvasive techniques that are increasingly employed to diagnose HCC in patients with cirrhosis. The mainstay of potentially curative therapy includes surgery – either resection or liver transplantation. However, most patients are ineligible for surgery, because of either advanced disease or underlying liver dysfunction, and are managed with locoregional and/or systemic therapies. Randomized controlled trials have demonstrated a survival benefit with both local therapies, either ablation or embolization, and systemic therapy in the form of the multikinase inhibitor sorafenib. Despite this, median survival remains poor and recurrence rates significant. Further advances in our understanding of the molecular pathogenesis of HCC hold promise in improving the diagnosis and treatment of this highly lethal cancer.
PMCID: PMC3421475  PMID: 22904613
hepatocellular carcinoma; viral hepatitis; liver transplantation; ablation; embolization; sorafenib
20.  Vorinostat increases expression of functional norepinephrine transporter in neuroblastoma in vitro and in vivo model systems 
Histone deacetylase (HDAC) inhibition causes transcriptional activation or repression of several genes that in turn can influence the biodistribution of other chemotherapeutic agents. Here, we hypothesize that the combination of vorinostat, a HDAC inhibitor, with 131I-metaiodobenzylguanidine (MIBG) would lead to preferential accumulation of the latter in neuroblastoma (NB) tumors via increased expression of the human norepinephrine transporter (NET).
Experimental Design
In vitro and in vivo experiments examined the effect of vorinostat on the expression of NET, an uptake transporter for 131I-MIBG. Human NB cell lines (Kelly and SH-SY-5Y) and NB1691luc mouse xenografts were employed. The upregulated NET protein was characterized for its effect on 123I-MIBG biodistribution.
Preincubation of NB cell lines, Kelly and SH-SY-5Y, with vorinostat caused dose-dependent increases in NET mRNA and protein levels. Accompanying this was a corresponding dose-dependent increase in MIBG uptake in NB cell lines. Four-fold and 2.5 fold increases were observed in Kelly and SH-SY-5Y cells, respectively, pre-treated with vorinostat in comparison to untreated cells. Similarly, NB xenografts, created by intravenous tail vein injection of NB1691-luc, and harvested from nude mice livers treated with vorinostat (150 mg/kg i.p.) showed substantial increases in NET protein expression. Maximal effect of vorinostat pretreatment in NB xenografts on 123I-MIBG biodistribution was observed in tumors that exhibited enhanced uptake in vorinostat treated (0.062 ± 0.011 μCi/(mg tissue-dose injected)) versus untreated mice (0.022 ± 0.003 μCi/(mg tissue-dose injected); p < 0.05).
The results of our study provide preclinical evidence that vorinostat treatment can enhance NB therapy with 131I-MIBG.
PMCID: PMC3247296  PMID: 21421857
norepinephrine transporter; MIBG; Vorinostat; histone deacetylase inhibitor; neuroblastoma xenograft; biodistribution
21.  MRI as a central component of clinical trials analysis in brainstem glioma: a report from the Pediatric Brain Tumor Consortium (PBTC) 
Neuro-Oncology  2011;13(4):417-427.
We report MRI findings from 2 pediatric clinical trials of diffuse intrinsic brainstem glioma (BSG) incorporating concurrent radiation therapy (RT) with molecularly targeted agents (gefitinib and tipifarnib). We determined associations of MRI variables with progression-free survival and overall survival and investigated effects of treatment on these variables.
MRI (including diffusion and perfusion) was done before treatment, every 8 weeks (first year), every 12 weeks (thereafter), and at the end of treatment or disease progression. Reduced tumor volume (P < .0001) and tumor diffusion values (P <.0001) were apparent on the first post-RT/drug studies. Decreases in tumor volume correlated with pre-RT volume (P < .0001) and pre-RT diffusion values (P < .0001); larger decreases were noted for tumors with higher volumes and diffusion values. Patients with larger pre-RT tumors had longer progression-free survival (P < .0001). Patients with ≥25% decrease in tumor volume and diffusion values after RT had longer progression-free survival (P = .028) and overall survival (P = .0009). Enhancement at baseline and over time was significantly associated with shorter survival. Tumor diffusion values with baseline enhancement were significantly lower than those without (P = .0002).
RT of BSG is associated with decreased tumor volume and intralesional diffusion values; patients with ≥25% decrease in values post-RT had relatively longer survival intervals, apparently providing an early imaging-based surrogate for relative outcomes. Patients with larger tumors and greater decreases in tumor volume and diffusion values had longer survival intervals. Tumor enhancement was associated with shorter survival, lower tumor diffusion values (increased cellularity), and a smaller drop in diffusion values after RT (P = .006). These associations justify continued investigation in other large clinical trials of brainstem glioma patients.
PMCID: PMC3064695  PMID: 21297126
Pediatric; brain tumor; brainstem glioma; MRI, radiation
22.  Inhibition of PI3K/mTOR pathways in glioblastoma and implications for combination therapy with temozolomide 
Neuro-Oncology  2011;13(4):384-392.
Due to its molecular heterogeneity and infiltrative nature, glioblastoma multiforme (GBM) is notoriously resistant to traditional and experimental therapeutics. To overcome these hurdles, targeted agents have been combined with conventional therapy. We evaluated the preclinical potential of a novel, orally bioavailable PI3K/mTOR dual inhibitor (XL765) in in vitro and in vivo studies. In vivo serially passaged human GBM xenografts that are more genetically stable than GBM cell lines in culture were used for all experiments. Biochemical downstream changes were evaluated by immunoblot and cytotoxicity by colorimetric ATP-based assay. For in vivo experiments, human xenograft GBM 39 grown intracranially in nude mice was altered to express luciferase to monitor tumor burden by optical imaging. XL765 resulted in concentration-dependent decreases in cell viability in vitro. Cytotoxic doses resulted in specific inhibition of PI3K signaling. Combining XL765 with temozolomide (TMZ) resulted in additive toxicity in 4 of 5 xenografts. In vivo, XL765 administered by oral gavage resulted in greater than 12-fold reduction in median tumor bioluminescence compared with control (Mann–Whitney test p = 0.001) and improvement in median survival (logrank p = 0.05). TMZ alone showed a 30-fold decrease in median bioluminescence, but the combination XL765 + TMZ yielded a 140-fold reduction in median bioluminescence (Mann-Whitney test p = 0.05) with a trend toward improvement in median survival (logrank p = 0.09) compared with TMZ alone. XL765 shows activity as monotherapy and in combination with conventional therapeutics in a range of genetically diverse GBM xenografts.
PMCID: PMC3064692  PMID: 21317208
PI3K/mTOR inhibitor; glioma; temozolomide; signaling inhibitor
23.  Phase II trial of tipifarnib and radiation in children with newly diagnosed diffuse intrinsic pontine gliomas 
Neuro-Oncology  2011;13(3):298-306.
We performed a phase II study to assess the efficacy and toxicity of tipifarnib, a farnesyltransferase inhibitor, administered with radiation therapy (RT) in children with newly diagnosed diffuse intrinsic pontine gliomas. Children 3-21 years old with pontine gliomas (BSGs) were treated with concurrent tipifarnib and RT, followed by adjuvant tipifarnib. Tipifarnib was taken orally twice daily (125 mg/m2/dose) during RT; after RT, it was taken at 200 mg/m2 twice daily for 21 days, in 28-day cycles. Initial and follow-up neuroimaging was centrally reviewed. Forty eligible patients (median age, 5.5 years; range, 3.3–16.5 years) had a median progression-free survival of 6.8 months (range, 0.2-18.6 months) and median overall survival of 8.3 months (range, 0.2-18.6 months). Kaplan–Meier estimates (± standard error) of 1-year progression-free and overall survival were 12.9% ±4.9% and 34.3% ±7.4%, respectively. A single patient remained on tipifarnib without progression at the completion of the study, two years after initiation of treatment. Seven patients were without disease progression for at least six months, three of whom remained controlled for more than a year. The most frequent toxicity was grade 3 lymphopenia. We documented a single instance of “pseudoprogression” by neuroimaging review. We found no discordance among 3 approaches to defining disease progression: as interpreted by treating institutions (based on clinical status and/or imaging) and by central review (using bi-dimensional tumor “area” versus volumetric measurements). For children with diffuse BSGs, tipifarnib administered with irradiation offered no clinical advantage over historical controls. Biopsies and molecular analyses of pediatric BSGs are vital for identification of new agents and for rational use of targeted agents.
PMCID: PMC3064607  PMID: 21339191
diffuse intrinsic pontine glioma; farnesyltransferase inhibitors; pediatric
24.  DNA hypermethylation profiles associated with glioma subtypes and EZH2 and IGFBP2 mRNA expression 
Neuro-Oncology  2011;13(3):280-289.
We explored the associations of aberrant DNA methylation patterns in 12 candidate genes with adult glioma subtype, patient survival, and gene expression of enhancer of zeste human homolog 2 (EZH2) and insulin-like growth factor-binding protein 2 (IGFBP2). We analyzed 154 primary glioma tumors (37 astrocytoma II and III, 52 primary glioblastoma multiforme (GBM), 11 secondary GBM, 54 oligodendroglioma/oligoastrocytoma II and III) and 13 nonmalignant brain tissues for aberrant methylation with quantitative methylation-specific PCR (qMS-PCR) and for EZH2 and IGFBP2 expression with quantitative reverse transcription PCR (qRT-PCR). Global methylation was assessed by measuring long interspersed nuclear element-1 (LINE1) methylation. Unsupervised clustering analyses yielded 3 methylation patterns (classes). Class 1 (MGMT, PTEN, RASSF1A, TMS1, ZNF342, EMP3, SOCS1, RFX1) was highly methylated in 82% (75/91) of lower-grade astrocytic and oligodendroglial tumors, 73% (8/11) of secondary GBMs, and 12% (6/52) of primary GBMs. The primary GBMs in this class were early onset (median age 37 years). Class 2 (HOXA9 and SLIT2) was highly methylated in 37% (19/52) of primary GBMs. None of the 10 genes for class 3 that were differentially methylated in classes 1 and 2 were hypermethylated in 92% (12/13) of nonmalignant brain tissues and 52% (27/52) of primary GBMs. Class 1 tumors had elevated EZH2 expression but not elevated IGFBP2; class 2 tumors had both high IGFBP2 and high EZH2 expressions. The gene-specific hypermethylation class correlated with higher levels of global LINE1 methylation and longer patient survival times. These findings indicate a generalized hypermethylation phenotype in glioma linked to improved survival and low IGFBP2. DNA methylation markers are useful in characterizing distinct glioma subtypes and may hold promise for clinical applications.
PMCID: PMC3064601  PMID: 21339190
glioma; DNA methylation; EZH2; Polycomb; PI3K/Akt
25.  Cooperation of the HDAC inhibitor vorinostat and radiation in metastatic neuroblastoma: Efficacy and underlying mechanisms 
Cancer letters  2011;306(2):223-229.
Histone deacetylase (HDAC) inhibitors can radiosensitize cancer cells. Radiation is critical in high-risk neuroblastoma treatment, and combinations of HDAC inhibitor vorinostat and radiation are proposed for neuroblastoma trials. Therefore, we investigated radiosensitizing effects of vorinostat in neuroblastoma. Treatment of neuroblastoma cell lines decreased cell viability and resulted in additive effects with radiation. In a murine metastatic neuroblastoma in vivo model vorinostat and radiation combinations decreased tumor volumes compared to single modality. DNA repair enzyme Ku-86 was reduced in several neuroblastoma cells treated with vorinostat. Thus, vorinostat potentiates anti-neoplastic effects of radiation in neuroblastoma possibly due to down-regulation of DNA repair enzyme Ku-86.
PMCID: PMC3244077  PMID: 21497989
Metastatic neuroblastoma; Radiation; Vorinostat; DNA repair

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