Tumor treating fields increases blood-brain barrier permeability and relative cerebral blood volume in patients with glioblastoma

BACKGROUND AND OBJECTIVE

200 kHz tumor treating fields (TTFields) is clinically approved for newly-diagnosed glioblastoma (nGBM). Because its effects on conventional surveillance MRI brain scans are equivocal, we investigated its effects on perfusion MRI (pMRI) brain scans.

METHODS

Each patient underwent institutional standard pMRI: dynamic contrast-enhanced (DCE) and dynamic susceptibility contrast (DSC) pMRI at three time points: baseline, 2-, and 6-months on-adjuvant therapy. At each timepoint, the difference between T1 pre- versus post-contrast tumor volume (ΔT1) and these pMRI metrics were evaluated: normalized and standardized relative cerebral blood volume (nRCBV, sRCBV); fractional plasma volume (Vp), volume of extravascular extracellular space (EES) per volume of tissue (Ve), blood-brain barrier (BBB) permeability (Ktrans), and time constant for gadolinium reflux from EES back into the vascular system (Kep). Between-group comparisons were performed using rank-sum analysis, and bootstrapping evaluated likely reproducibility of the results.

RESULTS

Among 13 pMRI datasets (11 nGBM, 2 recurrent GBM), therapies included temozolomide-only (n = 9) and temozolomide + TTFields (n = 4). No significant differences were found in patient or tumor characteristics. Compared to temozolomide-only, temozolomide + TTFields did not significantly affect the percent-change in pMRI metrics from baseline to 2 months. But during the 2- to 6-month period, temozolomide + TTFields significantly increased the percent-change in nRCBV (+26.9% [interquartile range 55.1%] vs -39.1% [37.0%], p = 0.049), sRCBV (+9.5% [39.7%] vs -30.5% [39.4%], p = 0.049), Ktrans (+54.6% [1768.4%] vs -26.9% [61.2%], p = 0.024), Ve (+111.0% [518.1%] vs -13.0% [22.5%], p = 0.048), and Vp (+98.8% [2172.4%] vs -24.6% [53.3%], p = 0.024) compared to temozolomide-only.

CONCLUSION

Using pMRI, we provide initial in-human validation of pre-clinical studies regarding the effects of TTFields on tumor blood volume and BBB permeability in GBM.

Deuterium metabolic imaging for 3D mapping of glucose metabolism in humans with central nervous system lesions at 3T

PURPOSE

To explore the potential of 3T deuterium metabolic imaging (DMI) using a birdcage 2 H radiofrequency (RF) coil in both healthy volunteers and patients with central nervous system (CNS) lesions.

METHODS

A modified gradient filter, home-built 2 H volume RF coil, and spherical k-space sampling were employed in a three-dimensional chemical shift imaging acquisition to obtain high-quality whole-brain metabolic images of 2 H-labeled water and glucose metabolic products. These images were acquired in a healthy volunteer and three subjects with CNS lesions of varying pathologies. Hardware and pulse sequence experiments were also conducted to improve the signal-to-noise ratio of DMI at 3T.

RESULTS

The ability to quantify local glucose metabolism in correspondence to anatomical landmarks across patients with varying CNS lesions is demonstrated, and increased lactate is observed in one patient with the most active disease.

CONCLUSION

DMI offers the potential to examine metabolic activity in human subjects with CNS lesions with DMI at 3T, promising for the potential of the future clinical translation of this metabolic imaging technique.

Development of [18F]DASA-10 for enhanced imaging of pyruvate kinase M2

PURPOSE

The aim of this study was to develop a positron emission tomography (PET) radiotracer for measuring pyruvate kinase M2 (PKM2) with improved physicochemical and pharmacokinetic properties compared to [18F]DASA-23.

EXPERIMENTAL DESIGN

First, we synthesized [18F]DASA-10 and tested its uptake and retention compared to [18F]DASA-23 in human and mouse glioma cell lines. We then confirmed the specificity of [18F]DASA-10 by transiently modulating the expression of PKM2 in DU145 and HeLa cells. Next, we determined [18F]DASA-10 pharmacokinetics in healthy nude mice using PET imaging and subsequently assessed the ability of [18F]DASA-10 versus [18F]DASA-23 to enable in vivo detection of intracranial gliomas in syngeneic C6 rat models of glioma.

RESULTS

[18F]DASA-10 demonstrated excellent cellular uptake and retention with values significantly higher than [18F]DASA-23 in all cell lines and timepoints investigated. [18F]DASA-10 showed a 73 % and 65 % reduced uptake respectively in DU145 and HeLa cells treated with PKM2 siRNA as compared to control siRNA treated cells. [18F]DASA-10 showed favorable biodistribution and pharmacokinetic properties and a significantly improved tumor-to-brain ratio in rat C6 glioma models relative to [18F]DASA-23 (3.2 ± 0.8 versus 1.6 ± 0.3, p = 0.01).

CONCLUSION

[18F]DASA-10 is a new PET radiotracer for molecular imaging of PKM2 with potential to overcome the prior limitations observed with [18F]DASA-23. [18F]DASA-10 shows promise for clinical translation to enable imaging of brain malignancies owing to its low background signal in the healthy brain.

Patterns of Progression in Patients With Newly Diagnosed Glioblastoma Treated With 5-mm Margins in a Phase 1/2 Trial of 5-Fraction Stereotactic Radiosurgery With Concurrent and Adjuvant Temozolomide

PURPOSE

In patients with newly diagnosed glioblastoma (GBM), tumor margins of at least 20 mm are the standard of care. We sought to determine the pattern of tumor progression in patients treated with 5-fraction stereotactic radiosurgery with 5-mm margins.

METHODS AND MATERIALS

Thirty adult patients with newly diagnosed GBM were treated with 5-fraction stereotactic radiosurgery in escalated doses from 25 to 40 Gy with a 5-mm total treatment margin. Progression was scored as "in-field" if the recurrent tumor was within or contiguous with the 5-mm margin, "marginal" if between 5 and 20 mm, and "distant" if entirely occurring greater than 20 mm. As geometric patterns of progression do not reflect the biologic dose received, we calculated the minimum equi-effective dose in 2 Gy (EQD2) per day at the site of tumor recurrence. Progression was "dosimetrically in-field" if covered by a minimum EQD2 per day of 48 Gy10.

RESULTS

From 2010 to 2016, 27 patients had progressed. Progression was in-field in 17 (63%), marginal in 3 (11%), and distant in 7 (26%) patients. In the 3 patients with marginal progression, the minimum EQD2 to recurrent tumor were 48 Gy10, 56 Gy10 (both considered dosimetrically in-field), and 7 Gy10 (ie, dosimetrically out-of-field). Median overall survival was 12.1 months for in-field (95% confidence interval [CI], 8.9-17.6), 15.1 months (95% CI, 10.1 to not achieved) for marginal, and 21.4 months (95% CI, 11.2-33.5) for distant progression. Patients with radiation necrosis were less likely to have in-field progression (1 of 7; 14%) compared with those without radiation necrosis (16 of 20; 80%; P = .003); those with necrosis had a median overall survival of 27.2 months (95% CI, 11.2-48.3) compared with 11.7 months (95% CI, 8.9-17.6) for patients with no necrosis (P = .077).

CONCLUSIONS

In patients with newly diagnosed GBM treated with a 5-mm clinical target volume margin, 3 patients (11%) had marginal progression within 5 to 20 mm; only 1 patient (4%) may have dosimetrically benefitted from conventional 20-mm margins. Radiation necrosis was associated with in-field tumor control.

A Clinical PET Imaging Tracer ([18F]DASA-23) to Monitor Pyruvate Kinase M2-Induced Glycolytic Reprogramming in Glioblastoma

PURPOSE

Pyruvate kinase M2 (PKM2) catalyzes the final step in glycolysis, a key process of cancer metabolism. PKM2 is preferentially expressed by glioblastoma (GBM) cells with minimal expression in healthy brain. We describe the development, validation, and translation of a novel PET tracer to study PKM2 in GBM. We evaluated 1-((2-fluoro-6-[18F]fluorophenyl)sulfonyl)-4-((4-methoxyphenyl)sulfonyl)piperazine ([18F]DASA-23) in cell culture, mouse models of GBM, healthy human volunteers, and patients with GBM.

EXPERIMENTAL DESIGN

[18F]DASA-23 was synthesized with a molar activity of 100.47 ± 29.58 GBq/μmol and radiochemical purity >95%. We performed initial testing of [18F]DASA-23 in GBM cell culture and human GBM xenografts implanted orthotopically into mice. Next, we produced [18F]DASA-23 under FDA oversight, and evaluated it in healthy volunteers and a pilot cohort of patients with glioma.

RESULTS

In mouse imaging studies, [18F]DASA-23 clearly delineated the U87 GBM from surrounding healthy brain tissue and had a tumor-to-brain ratio of 3.6 ± 0.5. In human volunteers, [18F]DASA-23 crossed the intact blood-brain barrier and was rapidly cleared. In patients with GBM, [18F]DASA-23 successfully outlined tumors visible on contrast-enhanced MRI. The uptake of [18F]DASA-23 was markedly elevated in GBMs compared with normal brain, and it identified a metabolic nonresponder within 1 week of treatment initiation.

CONCLUSIONS

We developed and translated [18F]DASA-23 as a new tracer that demonstrated the visualization of aberrantly expressed PKM2 for the first time in human subjects. These results warrant further clinical evaluation of [18F]DASA-23 to assess its utility for imaging therapy-induced normalization of aberrant cancer metabolism.

A phase I/II trial of 5-fraction stereotactic radiosurgery with 5-mm margins with concurrent temozolomide in newly diagnosed glioblastoma: primary outcomes

BACKGROUND

We sought to determine the maximum tolerated dose (MTD) of 5-fraction stereotactic radiosurgery (SRS) with 5-mm margins delivered with concurrent temozolomide in newly diagnosed glioblastoma (GBM).

METHODS

We enrolled adult patients with newly diagnosed glioblastoma to 5 days of SRS in a 3 + 3 design on 4 escalating dose levels: 25, 30, 35, and 40 Gy. Dose limiting toxicity (DLT) was defined as Common Terminology Criteria for Adverse Events grades 3-5 acute or late CNS toxicity, including adverse radiation effect (ARE), the imaging correlate of radiation necrosis.

RESULTS

From 2010 to 2015, thirty patients were enrolled. The median age was 66 years (range, 51-86 y). The median target volume was 60 cm3 (range, 14.7-137.3 cm3). DLT occurred in 2 patients: one for posttreatment cerebral edema and progressive disease at 3 weeks (grade 4, dose 40 Gy); another patient died 1.5 weeks following SRS from postoperative complications (grade 5, dose 40 Gy). Late grades 1-2 ARE occurred in 8 patients at a median of 7.6 months (range 3.2-12.6 mo). No grades 3-5 ARE occurred. With a median follow-up of 13.8 months (range 1.7-64.4 mo), the median survival times were: progression-free survival, 8.2 months (95% CI: 4.6-10.5); overall survival, 14.8 months (95% CI: 10.9-19.9); O6-methylguanine-DNA methyltransferase hypermethylated, 19.9 months (95% CI: 10.5-33.5) versus 11.3 months (95% CI: 8.9-17.6) for no/unknown hypermethylation (P = 0.03), and 27.2 months (95% CI: 11.2-48.3) if late ARE occurred versus 11.7 months (95% CI: 8.9-17.6) for no ARE (P = 0.08).

CONCLUSIONS

The per-protocol MTD of 5-fraction SRS with 5-mm margins with concurrent temozolomide was 40 Gy in 5 fractions. ARE was limited to grades 1-2 and did not statistically impact survival.

Macrophage Exclusion after Radiation Therapy (MERT): A First in Human Phase I/II Trial using a CXCR4 Inhibitor in Glioblastoma

PURPOSE

Preclinical studies have demonstrated that postirradiation tumor revascularization is dependent on a stromal cell-derived factor-1 (SDF-1)/C-X-C chemokine receptor type 4 (CXCR4)-driven process in which myeloid cells are recruited from bone marrow. Blocking this axis results in survival improvement in preclinical models of solid tumors, including glioblastoma (GBM). We conducted a phase I/II study to determine the safety and efficacy of Macrophage Exclusion after Radiation Therapy (MERT) using the reversible CXCR4 inhibitor plerixafor in patients with newly diagnosed glioblastoma.

PATIENTS AND METHODS

We enrolled nine patients in the phase I study and an additional 20 patients in phase II using a modified toxicity probability interval (mTPI) design. Plerixafor was continuously infused intravenously via a peripherally inserted central catheter (PICC) line for 4 consecutive weeks beginning at day 35 of conventional treatment with concurrent chemoradiation. Blood serum samples were obtained for pharmacokinetic analysis. Additional studies included relative cerebral blood volume (rCBV) analysis using MRI and histopathology analysis of recurrent tumors.

RESULTS

Plerixafor was well tolerated with no drug-attributable grade 3 toxicities observed. At the maximum dose of 400 μg/kg/day, biomarker analysis found suprathreshold plerixafor serum levels and an increase in plasma SDF-1 levels. Median overall survival was 21.3 months [95% confidence interval (CI), 15.9-NA] with a progression-free survival of 14.5 months (95% CI, 11.9-NA). MRI and histopathology support the mechanism of action to inhibit postirradiation tumor revascularization.

CONCLUSIONS

Infusion of the CXCR4 inhibitor plerixafor was well tolerated as an adjunct to standard chemoirradiation in patients with newly diagnosed GBM and improves local control of tumor recurrences.

First-in-human intraoperative near-infrared fluorescence imaging of glioblastoma using cetuximab-IRDye800

Introduction

Maximizing extent of surgical resection with the least morbidity remains critical for survival in glioblastoma patients, and we hypothesize that it can be improved by enhancements in intraoperative tumor detection. In a clinical study, we determined if therapeutic antibodies could be repurposed for intraoperative imaging during resection.

Methods

Fluorescently labeled cetuximab-IRDye800 was systemically administered to three patients 2 days prior to surgery. Near-infrared fluorescence imaging of tumor and histologically negative peri-tumoral tissue was performed intraoperatively and ex vivo. Fluorescence was measured as mean fluorescence intensity (MFI), and tumor-to-background ratios (TBRs) were calculated by comparing MFIs of tumor and histologically uninvolved tissue.

Results

The mean TBR was significantly higher in tumor tissue of contrast-enhancing (CE) tumors on preoperative imaging (4.0 ± 0.5) compared to non-CE tumors (1.2 ± 0.3; p = 0.02). The TBR was higher at a 100 mg dose than at 50 mg (4.3 vs. 3.6). The smallest detectable tumor volume in a closed-field setting was 70 mg with 50 mg of dye and 10 mg with 100 mg. On sections of paraffin embedded tissues, fluorescence positively correlated with histological evidence of tumor. Sensitivity and specificity of tumor fluorescence for viable tumor detection was calculated and fluorescence was found to be highly sensitive (73.0% for 50 mg dose, 98.2% for 100 mg dose) and specific (66.3% for 50 mg dose, 69.8% for 100 mg dose) for viable tumor tissue in CE tumors while normal peri-tumoral tissue showed minimal fluorescence.

Conclusion

This first-in-human study demonstrates the feasibility and safety of antibody based imaging for CE glioblastomas.

Phase 1/2 Trial of 5-Fraction Stereotactic Radiosurgery With 5-mm Margins With Concurrent and Adjuvant Temozolomide in Newly Diagnosed Supratentorial Glioblastoma: Health-Related Quality of Life Results

PURPOSE

We report a longitudinal assessment of health-related quality of life (HRQOL) in patients with glioblastoma (GBM) treated on a prospective dose escalation trial of 5-fraction stereotactic radiosurgery (25-40 Gy in 5 fractions) with concurrent and adjuvant temozolomide.

METHODS

HRQOL was assessed using the European Organization for Research and Treatment of Cancer (EORTC) quality of life questionnaire core-30 (QLQ-C30) general, the EORTC quality of life questionnaire-brain cancer specific module (QLQ-BN20), and the M.D. Anderson Symptom Inventory-Brain Tumor (MDASI-BT). Questionnaires were completed at baseline and at every follow-up visit after completion of radiosurgery. Changes from baseline for 9 predefined HRQOL measures (global quality of life, physical functioning, social functioning, emotional functioning, motor dysfunction, communication deficit, fatigue, insomnia, and future uncertainty) were calculated at every time point.

RESULTS

With a median follow-up time of 10.4 months (range, 0.4-52 months), 139 total HRQOL questionnaires were completed by the 30 patients on trial. Compliance with HRQOL assessment was 76% at 12 months. Communication deficit significantly worsened over time, with a decline of 1.7 points per month (P=.008). No significant changes over time were detected in the other 8 scales of our primary analysis, including global quality of life. Although 8 patients (27%) experienced adverse radiation effects (ARE) on this dose escalation trial, it was not associated with a statistically significant decline in any of the primary HRQOL scales. Disease progression was associated with communication deficit, with patients experiencing an average worsening of 13.9 points per month after progression compared with 0.7 points per month before progression (P=.01).

CONCLUSION

On this 5-fraction dose escalation protocol for newly diagnosed GBM, overall HRQOL remained stable and appears similar to historical controls of 30 fractions of radiation therapy. Tumor recurrence was associated with worsening communication deficit, and ARE did not correlate with a decline in HRQOL.

Bevacizumab for Treatment-Refractory Pain Control in Neurofibromatosis Patients

OBJECTIVE

Chronic pain is a well-known morbidity associated with neurofibromatosis (NF) for which better therapies are needed. Surgery, radiation, and pain medications have been utilized, but often fail to relieve debilitating pain. One patient at our institution was noted to have near complete resolution of pain after treatment with bevacizumab for progressive neurologic deficit associated with NF2, suggesting its potential as an effective pain control method. We aim to better characterize the use of bevacizumab for pain control in this subset of patients.  Patients and Methods: We retrospectively reviewed 38 NF patients treated at our institution.   Results: Of the 38 total NF patients, we found that 63% reported chronic pain, with 18% reporting chronic opiate usage. Nine patients with chronic pain were considered for bevacizumab treatment and five went on to receive infusions. Of these patients, four out of five had previous surgical debulking and two out of five had previous radiation for attempted pain control. One patient had a lesion not amenable to surgery or radiation. Patients received a median of 13 cycles of bevacizumab, and four out of five patients reported a decrease in subjective pain. All patients that had pain relief had a relapse of pain symptoms when the dose was reduced or infusions were paused. Seventy-five percent were able to decrease opiate use. No major complications were noted. All five patients have elected to continue infusions for pain control.  Conclusion: Bevacizumab was, in general, well tolerated and should be considered as a treatment option in NF patients with chronic pain refractory or not amenable to surgical decompression and debulking, radiation, and pain medication.

Hyperpolarized (13)C-lactate to (13)C-bicarbonate ratio as a biomarker for monitoring the acute response of anti-vascular endothelial growth factor (anti-VEGF) treatment

Hyperpolarized [1-(13)C]pyruvate MRS provides a unique imaging opportunity to study the reaction kinetics and enzyme activities of in vivo metabolism because of its favorable imaging characteristics and critical position in the cellular metabolic pathway, where it can either be reduced to lactate (reflecting glycolysis) or converted to acetyl-coenzyme A and bicarbonate (reflecting oxidative phosphorylation). Cancer tissue metabolism is altered in such a way as to result in a relative preponderance of glycolysis relative to oxidative phosphorylation (i.e. Warburg effect). Although there is a strong theoretical basis for presuming that readjustment of the metabolic balance towards normal could alter tumor growth, a robust noninvasive in vivo tool with which to measure the balance between these two metabolic processes has yet to be developed. Until recently, hyperpolarized (13)C-pyruvate imaging studies had focused solely on [1-(13)C]lactate production because of its strong signal. However, without a concomitant measure of pyruvate entry into the mitochondria, the lactate signal provides no information on the balance between the glycolytic and oxidative metabolic pathways. Consistent measurement of (13)C-bicarbonate in cancer tissue, which does provide such information, has proven difficult, however. In this study, we report the reliable measurement of (13)C-bicarbonate production in both the healthy brain and a highly glycolytic experimental glioblastoma model using an optimized (13)C MRS imaging protocol. With the capacity to obtain signal in all tumors, we also confirm for the first time that the ratio of (13)C-lactate to (13)C-bicarbonate provides a more robust metric relative to (13)C-lactate for the assessment of the metabolic effects of anti-angiogenic therapy. Our data suggest a potential application of this ratio as an early biomarker to assess therapeutic effectiveness. Furthermore, although further study is needed, the results suggest that anti-angiogenic treatment results in a rapid normalization in the relative tissue utilization of glycolytic and oxidative phosphorylation by tumor tissue.

Volumetric spiral chemical shift imaging of hyperpolarized [2-(13) c]pyruvate in a rat c6 glioma model

PURPOSE

MRS of hyperpolarized [2-(13)C]pyruvate can be used to assess multiple metabolic pathways within mitochondria as the (13)C label is not lost with the conversion of pyruvate to acetyl-CoA. This study presents the first MR spectroscopic imaging of hyperpolarized [2-(13)C]pyruvate in glioma-bearing brain.

METHODS

Spiral chemical shift imaging with spectrally undersampling scheme (1042 Hz) and a hard-pulse excitation was exploited to simultaneously image [2-(13)C]pyruvate, [2-(13)C]lactate, and [5-(13)C]glutamate, the metabolites known to be produced in brain after an injection of hyperpolarized [2-(13)C]pyruvate, without chemical shift displacement artifacts. A separate undersampling scheme (890 Hz) was also used to image [1-(13)C]acetyl-carnitine. Healthy and C6 glioma-implanted rat brains were imaged at baseline and after dichloroacetate administration, a drug that modulates pyruvate dehydrogenase kinase activity.

RESULTS

The baseline metabolite maps showed higher lactate and lower glutamate in tumor as compared to normal-appearing brain. Dichloroacetate led to an increase in glutamate in both tumor and normal-appearing brain. Dichloroacetate-induced %-decrease of lactate/glutamate was comparable to the lactate/bicarbonate decrease from hyperpolarized [1-(13)C]pyruvate studies. Acetyl-carnitine was observed in the muscle/fat tissue surrounding the brain.

CONCLUSION

Robust volumetric imaging with hyperpolarized [2-(13)C]pyruvate and downstream products was performed in glioma-bearing rat brains, demonstrating changes in mitochondrial metabolism with dichloroacetate.

Phase II pilot study of single-agent etirinotecan pegol (NKTR-102) in bevacizumab-resistant high grade glioma

Patients with recurrence of high-grade glioma (HGG) after bevacizumab (BEV) have an extremely poor prognosis. Etirinotecan pegol (EP) is the first long-acting topoisomerase-I inhibitor designed to concentrate in and provide continuous tumor exposure throughout the entire chemotherapy cycle. Here we report results of a Phase 2, single arm, open-label trial evaluating EP in HGG patients who progressed after BEV. Patients age >18 with histologically proven anaplastic astrocytoma or glioblastoma (GB) who previously received standard chemo-radiation and recurred after BEV were eligible. A predicted life expectancy >6 weeks and KPS ≥ 50 were required. The primary endpoint was PFS at 6-weeks. Secondary endpoint was overall survival from first EP infusion. Response was assessed by RANO criteria. Single agent EP was administered IV every 3 weeks at 145 mg/m2. Patients did not receive BEV while on EP. 20 patients (90 % GB) were enrolled with a median age of 50 and median KPS of 70. Three patients with GB (16.7 % of GB) had partial MRI responses. 6-week PFS was 55 %. Median and 6-month PFS were 2.2 months (95 % CI 1.4–3.4 months) and 11.2 % (95 % CI 1.9–28.9 %) respectively. Median overall survival from first EP infusion was 4.5 months (95 % CI 2.4–5.9). Only one patient had grade 3 toxicity (diarrhea with dehydration) attributable to EP. Hematologic toxicity was mild. Three patients had confirmed partial responses according to RANO criteria. These clinical data combined with a favorable safety profile warrant further clinical investigation of this agent in HGG.

A phase II, multicenter trial of rindopepimut (CDX-110) in newly diagnosed glioblastoma: the ACT III study

BACKGROUND

The epidermal growth factor receptor variant III deletion mutation, EGFRvIII, is expressed in ∼30% of primary glioblastoma and linked to poor long-term survival. Rindopepimut consists of the unique EGFRvIII peptide sequence conjugated to keyhole limpet hemocyanin. In previous phase II trials (ACTIVATE/ACT II), rindopepimut was well tolerated with robust EGFRvIII-specific immune responses and promising progression-free and overall survival. This multicenter, single-arm phase II clinical trial (ACT III) was performed to confirm these results.

METHODS

Rindopepimut and standard adjuvant temozolomide chemotherapy were administered to 65 patients with newly diagnosed EGFRvIII-expressing (EGFRvIII+) glioblastoma after gross total resection and chemoradiation.

RESULTS

Progression-free survival at 5.5 months (∼8.5 mo from diagnosis) was 66%. Relative to study entry, median overall survival was 21.8 months, and 36-month overall survival was 26%. Extended rindopepimut vaccination (up to 3.5+ years) was well tolerated. Grades 1-2 injection site reactions were frequent. Anti-EGFRvIII antibody titers increased ≥4-fold in 85% of patients, and increased with duration of treatment. EGFRvIII was eliminated in 4/6 (67%) tumor samples obtained after >3 months of therapy.

CONCLUSIONS

This study confirms, in a multicenter setting, the preliminary results seen in previous phase II trials of rindopepimut. A pivotal, double-blind, randomized, phase III trial ("ACT IV") is under way.

Metabolic response of glioma to dichloroacetate measured in vivo by hyperpolarized (13)C magnetic resonance spectroscopic imaging

BACKGROUND

The metabolic phenotype that derives disproportionate energy via glycolysis in solid tumors, including glioma, leads to elevated lactate labeling in metabolic imaging using hyperpolarized [1-(13)C]pyruvate. Although the pyruvate dehydrogenase (PDH)-mediated flux from pyruvate to acetyl coenzyme A can be indirectly measured through the detection of carbon-13 ((13)C)-labeled bicarbonate, it has proven difficult to visualize (13)C-bicarbonate at high enough levels from injected [1-(13)C]pyruvate for quantitative analysis in brain. The aim of this study is to improve the detection of (13)C-labeled metabolites, in particular bicarbonate, in glioma and normal brain in vivo and to measure the metabolic response to dichloroacetate, which upregulates PDH activity.

METHODS

An optimized protocol for chemical shift imaging and high concentration of hyperpolarized [1-(13)C]pyruvate were used to improve measurements of lactate and bicarbonate in C6 glioma-transplanted rat brains. Hyperpolarized [1-(13)C]pyruvate was injected before and 45 min after dichloroacetate infusion. Metabolite ratios of lactate to bicarbonate were calculated to provide improved metrics for characterizing tumor metabolism.

RESULTS

Glioma and normal brain were well differentiated by lactate-to-bicarbonate ratio (P = .002, n = 5) as well as bicarbonate (P = .0002) and lactate (P = .001), and a stronger response to dichloroacetate was observed in glioma than in normal brain.

CONCLUSION

Our results clearly demonstrate for the first time the feasibility of quantitatively detecting (13)C-bicarbonate in tumor-bearing rat brain in vivo, permitting the measurement of dichloroacetate-modulated changes in PDH flux. The simultaneous detection of lactate and bicarbonate provides a tool for a more comprehensive analysis of glioma metabolism and the assessment of metabolic agents as anti-brain cancer drugs.

The rationale for early detection and treatment of brain tumors in survivors of childhood cancer

Survivors of childhood cancer have a relatively high risk of developing second cancers. The incidence of brain tumor in these patients approaches 1% at 10 years, over 80-fold that in the general population. This high incidence increases the likelihood that early detection of brain tumors in survivors of childhood cancer is feasible. By analogy with other epithelial cancers, detection and treatment of brain tumors at a pre-neoplastic or premalignant stage may render screening and treatment cost effective for certain high-risk populations. Our animal studies with a clinically appropriate model of this condition suggest that there is a pre-neoplastic, pre-malignant brain tumor lesion that is potentially both detectable and effectively treated. The possibility of detecting such a treatable antecedent to brain tumors provides the rationale for genomic and proteomic screening of tumor tissue, CSF, plasma and urine in this animal model, of tumor tissue and body fluids of patients with known brain tumors at various stages, and of body fluids of survivors of childhood cancer.

Chemerin158K protein is the dominant chemerin isoform in synovial and cerebrospinal fluids but not in plasma

Chemerin is a chemoattractant involved in immunity that may also function as an adipokine. Chemerin circulates as an inactive precursor (chem163S), and its activation requires proteolytic cleavages at its C terminus, involving proteases involved in coagulation, fibrinolysis, and inflammation. However, the key proteolytic steps in prochemerin activation in vivo remain to be established. Previously, we have shown that C-terminal cleavage of chem163S by plasmin to chem158K, followed by a carboxypeptidase cleavage, leads to the most active isoform, chem157S. To identify and quantify the in vivo chemerin isoforms in biological specimens, we developed specific ELISAs for chem163S, chem158K, and chem157S, using antibodies raised against peptides from the C terminus of the different chemerin isoforms. We found that the mean plasma concentrations of chem163S, chem158K, and chem157S were 40 ± 7.9, 8.1 ± 2.9, and 0.7 ± 0.8 ng/ml, respectively. The total level of cleaved and noncleaved chemerins in cerebrospinal fluids was ∼10% of plasma levels whereas it was elevated ∼2-fold in synovial fluids from patients with arthritis. On the other hand, the fraction of cleaved chemerins was much higher in synovial fluid and cerebrospinal fluid samples than in plasma (∼75%, 50%, and 18% respectively). Chem158K was the dominant chemerin isoform, and it was not generated by ex vivo processing, indicating that cleavage of prochemerin at position Lys-158, whether by plasmin or another serine protease, represents a major step in prochemerin activation in vivo. Our study provides the first direct evidence that chemerin undergoes extensive proteolytic processing in vivo, underlining the importance of measuring individual isoforms.

Embryonic stem cell rescue of tremor and ataxia in myelin-deficient shiverer mice

Transplantation of neural precursor cells has been proposed as a possible approach for replacing missing or damaged central nervous system myelin. Neonatal and adult myelin-deficient shiverer (shi) mice, bearing a mutation of the myelin basic protein (MBP) gene, have been used extensively as hosts for testing cell engraftment, migration, and myelination, but relatively little progress has been made in reversing shi motor deficits. Here we describe a prenatal cell replacement strategy, showing that embryonic stem cells injected into shi blastocyst embryos can generate chimeric mice with strong and widespread immunoreactive MBP expression throughout the brain and a behavioral (motor) phenotype that appears essentially rescued.

Tumor Necrosis Factor-α–Induced Protein 3 As a Putative Regulator of Nuclear Factor-κB–Mediated Resistance to O6-Alkylating Agents in Human Glioblastomas

Purpose

Pre-existing and acquired drug resistance are major obstacles to the successful treatment of glioblastomas.

Methods

We used an integrated resistance model and genomics tools to globally explore molecular factors and cellular pathways mediating resistance to O6-alkylating agents in glioblastoma cells.

Results

We identified a transcriptomic signature that predicts a common in vitro and in vivo resistance phenotype to these agents, a proportion of which is imprinted recurrently by gene dosage changes in the resistant glioblastoma genome. This signature was highly enriched for genes with functions in cell death, compromise, and survival. Modularity was a predominant organizational principle of the signature, with functions being carried out by groups of interacting molecules in overlapping networks. A highly significant network was built around nuclear factor-κB (NF-κB), which included the persistent alterations of various NF-κB pathway elements. Tumor necrosis factor-α–induced protein 3 (TNFAIP3) was identified as a new regulatory component of a putative cytoplasmic signaling cascade that mediates NF-κB activation in response to DNA damage caused by O6-alkylating agents. Expression of the corresponding zinc finger protein A20 closely mirrored the expression of the TNFAIP3 transcript, and was inversely related to NF-κB activation status in the resistant cells. A prediction model based on the resistance signature enabled the subclassification of an independent, validation cohort of 31 glioblastomas into two outcome groups (P = .037) and revealed TNFAIP3 as part of an optimized four-gene predictor associated significantly with patient survival (P = .022).

Conclusion

Our results offer strong evidence for TNFAIP3 as a key regulator of the cytoplasmic signaling to activate NF-κB en route to O6-alkylating agent resistance in glioblastoma cells. This pathway may be an attractive target for therapeutic modulation of glioblastomas.

Functional network analysis reveals extended gliomagenesis pathway maps and three novel MYC-interacting genes in human gliomas

Gene expression profiling has proven useful in subclassification and outcome prognostication for human glial brain tumors. The analysis of biological significance of the hundreds or thousands of alterations in gene expression found in genomic profiling remains a major challenge. Moreover, it is increasingly evident that genes do not act as individual units but collaborate in overlapping networks, the deregulation of which is a hallmark of cancer. Thus, we have here applied refined network knowledge to the analysis of key functions and pathways associated with gliomagenesis in a set of 50 human gliomas of various histogenesis, using cDNA microarrays, inferential and descriptive statistics, and dynamic mapping of gene expression data into a functional annotation database. Highest-significance networks were assembled around the myc oncogene in gliomagenesis and around the integrin signaling pathway in the glioblastoma subtype, which is paradigmatic for its strong migratory and invasive behavior. Three novel MYC-interacting genes (UBE2C, EMP1, and FBXW7) with cancer-related functions were identified as network constituents differentially expressed in gliomas, as was CD151 as a new component of a network that mediates glioblastoma cell invasion. Complementary, unsupervised relevance network analysis showed a conserved self-organization of modules of interconnected genes with functions in cell cycle regulation in human gliomas. This approach has extended existing knowledge about the organizational pattern of gene expression in human gliomas and identified potential novel targets for future therapeutic development.

Amplification of whole tumor genomes and gene-by-gene mapping of genomic aberrations from limited sources of fresh-frozen and paraffin-embedded DNA

Sufficient quantity of genomic DNA can be a bottleneck in genome-wide analysis of clinical tissue samples. DNA polymerase Phi29 can be used for the random-primed amplification of whole genomes, although the amplification may introduce bias in gene dosage. We have performed a detailed investigation of this technique in archival fresh-frozen and formalin-fixed/paraffin-embedded tumor DNA by using cDNA microarray-based comparative genomic hybridization. Phi29 amplified DNA from matched pairs of fresh-frozen and formalin-fixed/paraffin-embedded tumor samples with similar efficiency. The distortion in gene dosage representation in the amplified DNA was nonrandom and reproducibly involved distinct genomic loci. Regional amplification efficiency was significantly linked to regional GC content of the template genome. The biased gene representation in amplified tumor DNA could be effectively normalized by using amplified reference DNA. Our data suggest that genome-wide gene dosage alterations in clinical tumor samples can be reliably assessed from a few hundred tumor cells. Therefore, this amplification method should lend itself to high-throughput genetic analyses of limited sources of tumor, such as fine-needle biopsies, laser-microdissected tissue, and small paraffin-embedded specimens.

High-resolution genome-wide mapping of genetic alterations in human glial brain tumors

High-resolution genome-wide mapping of exact boundaries of chromosomal alterations should facilitate the localization and identification of genes involved in gliomagenesis and may characterize genetic subgroups of glial brain tumors. We have done such mapping using cDNA microarray-based comparative genomic hybridization technology to profile copy number alterations across 42,000 mapped human cDNA clones, in a series of 54 gliomas of varying histogenesis and tumor grade. This gene-by-gene approach permitted the precise sizing of critical amplicons and deletions and the detection of multiple new genetic aberrations. It has also revealed recurrent patterns of occurrence of distinct chromosomal aberrations as well as their interrelationships and showed that gliomas can be clustered into distinct genetic subgroups. A subset of detected alterations was shown predominantly associated with either astrocytic or oligodendrocytic tumor phenotype. Finally, five novel minimally deleted regions were identified in a subset of tumors, containing putative candidate tumor suppressor genes (TOPORS, FANCG, RAD51, TP53BP1, and BIK) that could have a role in gliomagenesis.

Differentiation prevents assessment of neural stem cell pluripotency after blastocyst injection

Earlier studies reported that neural stem (NS) cells injected into blastocysts appeared to be pluripotent, differentiating into cells of all three germ layers. In this study, we followed in vitro green fluorescent protein (GFP)-labeled NS and embryonic stem (ES) cells injected into blastocysts. Forty-eight hours after injection, significantly fewer blastocysts contained GFP-NS cells than GFP-ES cells. By 96 hours, very few GFP-NS cells remained in blastocysts compared with ES cells. Moreover, 48 hours after injection, GFP-NS cells in blastocysts extended long cellular processes, ceased expressing the NS cell marker nestin, and instead expressed the astrocytic marker glial fibrillary acidic protein. GFP-ES cells in blastocysts remained morphologically undifferentiated, continuing to express the pluripotent marker stage-specific embryonic antigen-1. Selecting cells from the NS cell population that preferentially formed neurospheres for injection into blastocysts resulted in identical results. Consistent with this in vitro behavior, none of almost 80 mice resulting from NS cell-injected blastocysts replaced into recipient mothers were chimeric. These results strongly support the idea that NS cells cannot participate in chimera formation because of their rapid differentiation into glia-like cells. Thus, these results raise doubts concerning the pluripotency properties of NS cells.

Isolation of immortalized, INK4a/ARF-deficient cells from the subventricular zone after in utero N-ethyl-N-nitrosourea exposure

OBJECT

Brain tumors, including gliomas, develop several months after rats are exposed in utero to N-ethyl-N-nitroso-urea (ENU). Although pathological changes cannot be detected until these animals are several weeks old, the process that eventually leads to glioma formation must begin soon after exposure given the rapid clearance of the carcinogen and the observation that transformation of brain cells isolated soon after exposure occasionally occurs. This model can therefore potentially provide useful insights about the early events that precede overt glioma formation. The authors hypothesized that future glioma cells arise from stem/progenitor cells residing in or near the subventricular zone (SVZ) of the brain.

METHODS

Cells obtained from the SVZ or corpus striatum in ENU-exposed and control rats were cultured in an epidermal growth factor (EGF)-containing, chemically defined medium. Usually, rat SVZ cells cultured in this manner (neurospheres) are nestin-positive, undifferentiated, and EGF-dependent and undergo cell senescence. Consistent with these prior observations, control SVZ cells undergo senescence by the 12th to 15th doubling (20 of 20 cultures). In contrast, three of 15 cultures of cells derived from the SVZs of individual ENU-treated rats continue to proliferate for more than 60 cell passages. Each of these nestin-expressing immortalized cell lines harbored a common homozygous deletion spanning the INK4a/ARF locus and was unable to differentiate into neural lineages after exposure to specific in vitro stimuli. Nevertheless, unlike the rat C6 glioma cell line, these immortalized cell lines demonstrate EGF dependence and low clonogenicity in soft agar and did not form tumors after intracranial transplantation.

CONCLUSIONS

Data in this study indicated that immortalized cells may represent glioma precursors that reside in the area of the SVZ after ENU exposure that may serve as a reservoir for further genetic and epigenetic hits that could eventually result in a full glioma phenotype.

Aberrant nestin expression during ethylnitrosourea-(ENU)-induced neurocarcinogenesis

Nestin is a unique intermediate filament protein. While it is robustly expressed in developing brain, postnatal expression is limited to the brain's subventricular zone (SVZ) and endothelial cells. Reexpression occurs, however, under several pathological conditions, including injury and neoplasia. We hypothesized that nestin would be a sensitive marker of early neoplasia after transplacental exposure of rats to ethylnitrosourea (ENU). Rats of various ages were administered bromodeoxyuridine (BudR) before sacrifice, and brain sections were examined for proliferative cells and several immunohistochemical markers, including nestin. Additional rats were examined after a stab wound injury to assess the expression of two of these markers, GFAP and nestin, in reactive astrocytes. All ENU-induced brain tumors (n = 9) were classified as gliomas (astrocytomas or oligoastrocytomas) based on their histology and immunophenotype. Nestin expression was noted in all tumors examined and was present in tumor cells as well as endothelial cells. During tumor development, we consistently noted nestin-expressing cells bearing multiple processes distributed throughout brain parenchyma. Both single cells and multiple cell clusters were observed as early as postnatal day 30 in all ENU-exposed brains examined (n = 11). Such distinctive nestin-expressing cells were not seen in nestin-stained control brains or ENU-exposed brains stained for GFAP or vimentin, nor was such a cell seen in a stab wound model used to assess reactive astrocytosis. While the number of these clusters was highly variable among rats, their size increased between 30 and 90 days. The data suggest that these nestin-expressing cells represent an early stage of the neoplastic process. It remains to be determined whether these cells become apparent at 30 days of age due to "dedifferentiation" of a local resident astrocyte or astrocyte precursor cell or migration of a relatively undifferentiated precursor/stem cell from the SVZ.

The impact of p53 tumor suppressor gene on glioma biology

The tumor suppressor gene, p53, is important in glioma biology. The authors of this paper review its role in cell physiology, epidemiology, glioma progression, prognosis, and therapeutic advances.

Temozolomide as an alternative to irradiation for elderly patients with newly diagnosed malignant gliomas

BACKGROUND

The optimal treatment for elderly patients (defined as patients 70 years of age or older) with malignant gliomas (MG) remains controversial. Some physicians advocate withholding therapy following diagnosis based on the observation that elderly patients do not tolerate adjuvant radiotherapy. The availability of temozolomide (TMZ), a new alkylating agent with antiglioma efficacy, offers another potential therapeutic option for these patients. The drug can be administered orally at home with minimal morbidity.

METHODS

The authors retrospectively reviewed a cohort of 86 consecutive elderly MG patients from three institutions, 32 of whom received monthly TMZ in lieu of radiation.

RESULTS

Initial Karnofsky performance score was the only predictor of survival in this cohort. No difference in survival was noted between these two groups. Toxicity was minimal in the chemotherapy-treated group and a higher percentage of patients receiving chemotherapy died at home.

CONCLUSIONS

The authors concluded that TMZ is as effective as irradiation as a treatment of elderly patients with MG. It is an alternative and, perhaps, a superior therapeutic option to irradiation, based on its ease of administration and low morbidity.

A method for clonal analysis of epidermal growth factor-responsive neural progenitors

Epidermal growth factor (EGF) responsive neural progenitors are defined by clonal growth from single cells. In previous studies we were unable to obtain clones at single cell densities using trypsinized cells and trituration alone always gave cellular aggregates. Here we report on single cell derived clones using a technique involving trituration of EGF responsive neurospheres, cell filtration, and single cell sorting using a MoFlo high speed fluorescence activated cell sorter. Single cell deposition was confirmed by labeling cells with Hoechst 33342 and Flow-check Fluorospheres, and visualization by fluorescence microscopy. The cells were deposited into liquid medium and grown from single cells in 10-20 ng/ml EGF for 12-14 days. This gave a cloning efficiency of 2.12%+/-0.37. New colonies occurred as late as day 18 post-sort. Tritiated thymidine suicide indicates that a percentage of these cells are cycling. Immunohistochemical analysis for oligodendrocytes, astroglia, and neuronal lineages performed on colonies at 10-14 and 21-28 days gave 39% uni-lineage, 36% bi-lineage, and 25% tri-lineage colonies. A total of five different types of progenitor cells were observed. In individual colonies, oligodendrons predominated with a lesser presence of astroglial or neuronal cell types. This approach establishes a reliable and reproducible method for single cell cloning of neurosphere cells.

Antitumor effects of ajulemic acid (CT3), a synthetic non-psychoactive cannabinoid

One of the endogenous transformation products of tetrahydrocannabinol (THC) is THC-11-oic acid, and ajulemic acid (AJA; dimethylheptyl-THC-11-oic acid) is a side-chain synthetic analog of THC-11-oic acid. In preclinical studies, AJA has been found to be a potent anti-inflammatory agent without psychoactive properties. Based on recent reports suggesting antitumor effects of cannabinoids (CBs), we assessed the potential of AJA as an antitumor agent. AJA proved to be approximately one-half as potent as THC in inhibiting tumor growth in vitro against a variety of neoplastic cell lines. However, its in vitro effects lasted longer. The antitumor effect was stereospecific, suggesting receptor mediation. Unlike THC, however, whose effect was blocked by both CB(1) and CB(2) receptor antagonists, the effect of AJA was inhibited by only the CB(2) antagonist. Additionally, incubation of C6 glioma cells with AJA resulted in the formation of lipid droplets, the number of which increased over time; this effect was noted to a much greater extent after AJA than after THC and was not seen in WI-38 cells, a human normal fibroblast cell line. Analysis of incorporation of radiolabeled fatty acids revealed a marked accumulation of triglycerides in AJA-treated cells at concentrations that produced tumor growth inhibition. Finally, AJA, administered p.o. to nude mice at a dosage several orders of magnitude below that which produces toxicity, inhibited the growth of subcutaneously implanted U87 human glioma cells modestly but significantly. We conclude that AJA acts to produce significant antitumor activity and effects its actions primarily via CB(2) receptors. Its very favorable toxicity profile, including lack of psychoactivity, makes it suitable for chronic usage. Further studies are warranted to determine its optimal role as an antitumor agent.

Association of increased phosphatidylinositol 3-kinase signaling with increased invasiveness and gelatinase activity in malignant gliomas

OBJECT

Glioblastoma multiforme is the most malignant of the primary brain tumors and aggressively infiltrates surrounding brain tissue, resulting in distant foci within the central nervous system, thereby rendering this tumor surgically incurable. The recent findings that both phosphatidylinositol 3-kinase (PI 3-K) and the phosphatase and tensin homolog (PTEN) regulate tumor cell invasiveness have led the authors to surmise that these lipid signaling molecules might play a role in regulating matrix metalloproteinases (MMPs), which are essential for tumor cell invasion.

METHODS

Using the C6 glioma cell line, which does not express measurable amounts of PTEN protein and in which in vitro invasiveness is MMP dependent, the authors determined that in vitro glioma cell invasiveness was significantly reduced when cells were preincubated overnight with LY294002 or wortmannin, two specific inhibitors of PI 3-K signaling. Next, using gelatin zymography, it was noted that these compounds significantly inhibited MMP-2 and MMP-9 activities. Moreover, the decrease in MMP activity correlated with the decrease in PI 3-K activity, as assessed by Akt phosphorylation. Finally, using semiquantitative reverse transcriptase-polymerase chain reaction, the authors demonstrated that LY294002 decreased messenger (m)RNA levels for both MMPs. Thus, these in vitro data indicate that PI 3-K signaling modulates gelatinase activity at the level of mRNA. Using immunostaining of phosphorylated Akt (p-Akt) as a measure of PI 3-K activity, the authors next assessed rat brains implanted with C6 cells. Compared with surrounding brain, there was marked p-Akt staining in C6 glioma cells and in neurons immediately adjacent to the tumor, but not in normal brain. The p-Akt staining in tumors was especially intense in perivascular areas. Using double-labeling techniques, colocalization of p-Akt with MMP-2 and MMP-9 was also noted in perivascular tumor areas.

CONCLUSIONS

The increase in p-Akt staining within these PTEN-deficient gliomas is consistent with what would be predicted from unchecked PI 3-K signaling. Furthermore, the immunohistochemically detected colocalization of p-Akt and MMP-2 and MMP-9 supports the authors' in vitro studies and the proposed linkage between PI 3-K signaling and MMP activity in gliomas.

PTEN: a newly identified regulator of neuronal differentiation

Even though phosphorylation of phosphatidylinositols by phosphoinositide 3-kinase has an important and pervasive role in the nervous system, little is known about the phosphatases that reverse this reaction. Recently, such a phosphatase, PTEN, was cloned as a tumor suppressor for gliomas. We now know that PTEN is a tumor suppressor for many tumor types and is a phosphatidylinositol phosphatase specific for the 3-position of the inositol ring. PTEN is expressed in most, if not all, neurons and is localized in the nucleus and cytoplasm. PTEN is not evident in neural processes or synapses. PTEN is induced during neuronal differentiation and is required for survival of differentiating neuronal cells. In summary, PTEN is a regulatory molecule with multiple functions at multiple subcellular sites. Further studies are required to determine which downstream pathways are regulated by PTEN, by which mechanisms PTEN activity is regulated, which stimuli regulate PTEN activity, and why a molecule that inhibits several survival pathways is induced during neurogenesis.

Neurotrophin channeling of neural progenitor cell differentiation

The act of defining neuropoietic progenitor/stem cells is still in its early phases. Epidermal growth factor (EGF) stimulates extended proliferation of aggregates of subventricular striatal cells, taken from E15 mouse striatum, termed neurospheres in liquid culture. We have shown here and in previous work, using either immunohistochemistry or RT-PCR, that neurosphere cells express 13 cytokines (32 tested) and 20 cytokine receptors (28 tested), with 11 potential paracrine and nine potential autocrine loops. The neurotrophin receptors, Trk A, B, and C, were all expressed. Using a newly developed FACS single cell deposition technique, we evaluated the capacity of single EGF stimulated neurosphere cells to respond to the ligands for Trk A and B, nerve growth factor (NGF), and brain-derived neurotrophin factor (BDNF). Addition of NGF or BDNF to EGF for 14 days had no effect, but removal of EGF at day 14 with subsequent addition of BDNF or NGF resulted in an increase in neuronal and astroglial, but not oligodendrocyte, colony cells at 21 and 28 days of culture for BDNF, and of both cell types at 28 days for NGF. Tri-lineage colonies increased at day 21 with BDNF and at day 28 for both NGF and BDNF. Gross colony morphology also showed changes with neurotrophin addition, forming multiple individual cell balls or filamentous spreads. When EGF was withdrawn, a threshold effect was observed, with small, but not large, colonies ceasing growth. BDNF and NGF showed no effects on cell proliferation when compared to EGF controls, as determined by 5'-bromo-2-deoxyuridine (BrdU) incorporation and thus, they appear to affect differentiation of progenitor cells. These data indicate a sequential action of cytokines with EGF maintaining viability and proliferation and blocking differentiation. Removal of EGF is then permissive for the differentiating effects of BDNF and NGF. These data further indicate that the majority of EGF neurosphere clones have neurotrophin dependent tri-lineage potential.

A role for nuclear PTEN in neuronal differentiation

Mutations of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), a protein and lipid phosphatase, have been associated with gliomas, macrocephaly, and mental deficiencies. We have assessed PTEN's role in the nervous system and find that PTEN is expressed in mouse brain late in development, starting at approximately postnatal day 0. In adult brain, PTEN is preferentially expressed in neurons and is especially evident in Purkinje neurons, olfactory mitral neurons, and large pyramidal neurons. To analyze the function of PTEN in neuronal differentiation, we used two well established model systems-pheochromocytoma cells and cultured CNS stem cells. PTEN is expressed during neurotrophin-induced differentiation and is detected in both the nucleus and cytoplasm. Suppression of PTEN levels with antisense oligonucleotides does not block initiation of neuronal differentiation. Instead, PTEN antisense leads to death of the resulting, immature neurons, probably during neurite extension. In contrast, PTEN is not required for astrocytic differentiation. These observations indicate that PTEN acts at multiple sites in the cell, regulating the transition of differentiating neuroblasts to postmitotic neurons.

Positive CSF HSV PCR in patients with GBM: a note of caution

Because two patients with temporal lobe glioblastomas had herpes simplex (HSV) DNA detected in CSF using PCR at the time of their presentation, we reviewed our laboratory's experience and performed PCR on a bank of 159 frozen CSF samples from patients with glioblastoma multiforme and other neurologic disorders. Based on the inability to detect HSV in any other tumor sample, we conclude that the positive HSV PCR in our two index patients most likely represented false-positive results. A diagnosis of HSE should not be made by PCR alone when the clinical presentation is atypical.

Ki-67 (clone MIB-1) proliferation index in recurrent glial neoplasms: no prognostic significance

BACKGROUND

To determine if the Ki-67 (MIB-1 clone) proliferative index (PI) has prognostic potential in patients with recurrent astroglial neoplasms.

METHODS

We conducted a retrospective review of 27 patients whose initial and recurrent specimens were available. Histopathology was determined according to the World Health Organization classification. Proliferation index was calculated on formalin-fixed tissue using the Ki-67 (MIB-1 clone) antibody. Morphometric data were analyzed in conjunction with clinical data and Cox Proportionate Hazards Analysis, Spearman's correlation coefficient and Mann-Whitney Test.

RESULTS

Initial histopathology included 14 glioblastoma multiforme, 7 anaplastic astrocytoma, 3 oligoastrocytoma, and 3 astrocytoma. Recurrent specimens showed changes consistent with treatment. While univariate analysis shows initial histology correlated with survival (p<0.036), PI did not correlate with survival after either initial (p = 0.86) or recurrent (p = 0.46) surgery for any tumor type. PI difference between specimens also did not correlate with survival (p = 0.91). Initial PI did not correlate with recurrent PI either (p = 0.43).

CONCLUSIONS

Ki-67 PI does not confer additional prognostic information for patients with recurrent astroglial neoplasms. One possible explanation for this observation is that treatment may alter the PI independent of its effect on tumor growth.

Cerebrospinal fluid cytology in patients with cancer: minimizing false-negative results

BACKGROUND

Detection of malignant cells on cytologic examination of the cerebrospinal fluid (CSF) is the diagnostic gold standard for leptomeningeal carcinomatosis. The absence of cells is a primary endpoint for most therapeutic trials. Unfortunately, false-negative results are common. Practical strategies are necessary to remedy this problem.

METHODS

Four physician-dependent variables (CSF sample volume, site of CSF sampling, processing time, and frequency of CSF sampling) were identified, and their contributions to the false-negative rate of CSF cytology were evaluated prospectively in 39 patients with leptomeningeal carcinomatosis. Retrospective data were analyzed to estimate the importance of these variables in daily practice.

RESULTS

False-negative CSF cytology results correlated with small CSF volume (P < 0.001), delayed processing (P < 0.001), not obtaining CSF from a site of symptomatic or radiographically demonstrated disease (P = 0.02), and sampling fewer than two times (P < 0.001). In 1 year, 97% of CSF specimens at the study institution were of inadequate volume; >25% were processed too slowly.

CONCLUSIONS

False-negative CSF cytology results are common, but can be minimized by: 1) withdrawing at least 10.5 mL of CSF for cytologic analysis; 2) processing the CSF specimen immediately; 3) obtaining CSF from a site of known leptomeningeal disease; and 4) repeating this procedure once if the initial cytology is negative.

Unexpected in vitro chemosensitivity of malignant gliomas to 4-hydroxyperoxycyclophosphamide (4-HC)

To individually tailor chemotherapy for patients with malignant gliomas according to tumor chemosensitivity, a rapid assay system which can be performed with a high success rate is needed. The fluorescent cytoprint assay (FCA) can assess multiple chemotherapeutic agents using small (approximately 500 cells) tumor aggregates very quickly (approximately 1 wk). Tissue samples from 51 patients with malignant gliomas obtained either at time of initial diagnosis (n = 34) or at recurrence were assayed using this method. The assay success rate approached 90% in those culture samples which were histologically verified as tumor. A meaningful number of agents could be tested both on samples obtained by stereotactic biopsy (median, 5) and on specimens from more extensive resections (median, 6). One hundred ninety-three FCAs were performed on a samples obtained from 36 patients. In only twenty six assays (14%) was an agent deemed sensitive (> 90% cell kill) to a chemotherapeutic agent. Sixty-two percent of sensitive FCAs were observed in tumors tested against the activated analog of cyclophosphamide, 4-hydroxyperoxycyclophosphamide (4-HC), where a sensitivity rate (# samples sensitive/total tested against agent) of 64% (95 % CI, 36.6-77.9%) was noted. This rate was significantly higher than with any other agent tested (p = 0.012, two sided McNemar's test) and was not affected by age, histology or disease status. We conclude that: (1) the FCA represents a feasible method for quickly assaying tumors for sensitivity to multiple chemotherapeutic agents; and (ii) malignant gliomas may be particularly sensitive to 4-HC.

Embryonic precursor cells that express Trk receptors: induction of different cell fates by NGF, BDNF, NT-3, and CNTF

Epidermal growth factor (EGF)-treated neurosphere cultures from embryonal striatum contain multipotential cells capable of neuronal, astrocytic, and oligodendroglial differentiation. In this study, we tested whether these neural precursor cells differentiate in the presence of neurotrophic factors. We first assayed neurosphere cells for expression of neurotrophin receptors. TrkA, TrkB, TrkC, and gp75 were detected by immunofluorescence microscopy in 60-80% of cells. In addition, the ciliary neurotrophic factor receptor alpha was expressed in 50-60% of cells. In the presence of the mitogen, EGF, treatment of stem cells with neurotrophic factors had no apparent effect. Removal of EGF from cells resulted in cessation of cell proliferation and pronounced astrocytic (glial fibrillary acidic protein+) differentiation. Neuronal (neurofilament+) and oligodendroglial (galactocerebroside+) cells appeared in cultures treated with neurotrophic factors. Nerve growth factor (NGF) resulted in bipolar neuronal cells, and brain-derived neurotrophic factor led to multipolar neuronal cells. Treatment with neurotrophin-3 or ciliary neurotrophic factor resulted in bipolar neuronal cells and oligodendrocytes. Neuronal differentiation in the presence of NGF was enhanced by extracellular matrix, and the resulting neuronal cells expressed choline acetyltransferase and, to a lesser degree, tyrosine hydroxylase. These studies demonstrate that neurotrophic factors influence the fates of these multipotential precursor cells. Indeed, the true utility of multipotential precursor cells is the production of different types of cells in different situations. Local cues, such as neurotrophic factors and extracellular matrix, may regulate production of different types of neural cells during development or in response to other stimuli, such as injury.

TrkA expression decreases the in vivo aggressiveness of C6 glioma cells

We stably expressed the nerve growth factor receptor trkA or a truncated trkA lacking the kinase domain (trkA delta) in a highly tumorigenic rat glioma cell line, C6. Survival of rats with large intrastriatal inocula of C6trkA cells was significantly longer than for rats bearing C6 or C6trkA delta cells. Histological studies revealed that C6trkA cells were much less invasive than C6 or C6trkA delta cells and had a greater rate of apoptosis. There was no apparent induction of differentiation of C6 cells by trkA. Therefore, unlike what is observed in neuroblastomas, trkA decreases tumorigenicity by modulating invasiveness and tumor cell death independent of inducing differentiation. This novel mechanism suggests a new therapeutic strategy for malignant gliomas.

Immunotoxin sensitivity of Chinese hamster ovary cells expressing human transferrin receptors with differing internalization rates

Previous studies have shown that immunotoxin action is dependent upon selective binding to the target cell, internalization and then passage into the cytosol. It is important to define precisely how these critical steps are controlled so that the underlying relationship of each to high cytotoxic effectiveness is understood. In order to evaluate the contribution of internalization rate and receptor number on immunotoxin potency, the effects of an anti-(transferrin receptor, TfR)/ricin A chain immunotoxin, 7D3-A, were assessed on a parent Chinese hamster ovary cell line developed in our laboratory with no TfR (TfRneg) and two lines transfected with either wild-type TfR (Tfrwt) or an internalization-deficient (TfR(delta 7-58del)) mutated human TfR. Potent, receptor-mediated cytotoxicity resulted from the action of 7D3-A on TfRwt cells (ID50 < 1 nM) while both TfRneg cells and TfR(delta 7-58del) were only minimally affected (ID50 > 100 nM). Butyrate up-regulation substantially increased receptor expression on the TfRwt and TfR(delta 7-58del) cells, but no corresponding rise in sensitivity to 7D3-A was observed. In contrast, immunotoxin potency was increased by co-treatment of TfRwt cells with the carboxylic ionophore monensin and the effect was even more pronounced for TfR(delta 7-58del) cells. We conclude that internalization rate or intracellular destination is a much more important determinant of immunotoxin efficacy than receptor number.