Synchronous identification of a dysembryoplastic neuroepithelial tumor (DNET) and an oligodendroglioma in a patient: A case report.

Synchronous gliomas of different histopathology are quite rare in non-syndromic, non-irradiated patients. Although "mixed" gliomas are not infrequent, and malignant gliomas often contain areas of disparate differentiation (e.g., glioblastoma with ependymal differentiation), it is unusual to find gliomas of different lineage presenting concurrently. We present a case of synchronous gliomas, one dysembryoplastic neuroepithelial tumor (DNET) and the other oligodendroglioma.

Target cell-specific synaptic dynamics of excitatory to inhibitory neuron connections in supragranular layers of human neocortex.

Rodent studies have demonstrated that synaptic dynamics from excitatory to inhibitory neuron types are often dependent on the target cell type. However, these target cell-specific properties have not been well investigated in human cortex, where there are major technical challenges in reliably obtaining healthy tissue, conducting multiple patch-clamp recordings on inhibitory cell types, and identifying those cell types. Here, we take advantage of newly developed methods for human neurosurgical tissue analysis with multiple patch-clamp recordings, post-hoc fluorescent in situ hybridization (FISH), machine learning-based cell type classification and prospective GABAergic AAV-based labeling to investigate synaptic properties between pyramidal neurons and PVALB- vs. SST-positive interneurons. We find that there are robust molecular differences in synapse-associated genes between these neuron types, and that individual presynaptic pyramidal neurons evoke postsynaptic responses with heterogeneous synaptic dynamics in different postsynaptic cell types. Using molecular identification with FISH and classifiers based on transcriptomically identified PVALB neurons analyzed by Patch-seq, we find that PVALB neurons typically show depressing synaptic characteristics, whereas other interneuron types including SST-positive neurons show facilitating characteristics. Together, these data support the existence of target cell-specific synaptic properties in human cortex that are similar to rodent, thereby indicating evolutionary conservation of local circuit connectivity motifs from excitatory to inhibitory neurons and their synaptic dynamics.

Cortical stimulation mapping and Wada results demonstrate a normal variant of right hemisphere language organization.

PURPOSE: Exclusive right hemisphere language lateralization is rarely observed in the Wada angiography results of epilepsy surgery patients. Cortical stimulation mapping (CSM) is infrequently performed in such patients, as most undergo nondominant left hemisphere resections, which are presumed not to pose any risk to language. Early language reorganization is typically assumed in such individuals, taking left hemisphere epileptiform activity as confirmation of change resulting from a pathologic process. We present data from CSM and Wada studies demonstrating that right hemisphere language occurs in the absence of left hemisphere pathology, suggesting it can exist as a normal, but rare variant, in some individuals. Furthermore, these data confirm the Wada test findings of atypical dominance. METHODS: Cortical stimulation mapping data were examined for all right hemisphere surgical patients with right hemisphere speech at our center between 1974 and 2006. Of 1,209 interpretable Wada procedures, 89 patients (7.4%) had exclusive right hemisphere speech, and 21 (1.7%) of these patients underwent surgery involving the right hemisphere. Language site location was determined by examining intraoperative photographs, and site distribution was statistically compared to published findings from left hemisphere language dominant patients. KEY FINDINGS: Language cortex was identified in the right hemisphere during CSM for all patients with available data. All sites could be classified in superior or middle temporal gyri, inferior parietal lobe, or inferior frontal gyrus, all of which were common zones where language was identified in the left hemisphere dominant comparison sample. SIGNIFICANCE: Results suggest that the Wada procedure is a valid measure for identifying right hemisphere language processing without any false lateralization found in the patients mapped with CSM (i.e., a positive Wada is 100% sensitive for finding right hemisphere language sites), and that the distribution of language sites is consistent across right hemisphere and left hemisphere language dominant patients, supporting the theory that right hemisphere language can occur as a normal variant of language lateralization.

Signature morpho-electric, transcriptomic, and dendritic properties of human layer 5 neocortical pyramidal neurons.

In the neocortex, subcerebral axonal projections originate largely from layer 5 (L5) extratelencephalic-projecting (ET) neurons. The unique morpho-electric properties of these neurons have been mainly described in rodents, where retrograde tracers or transgenic lines can label them. Similar labeling strategies are infeasible in the human neocortex, rendering the translational relevance of findings in rodents unclear. We leveraged the recent discovery of a transcriptomically defined L5 ET neuron type to study the properties of human L5 ET neurons in neocortical brain slices derived from neurosurgeries. Patch-seq recordings, where transcriptome, physiology, and morphology were assayed from the same cell, revealed many conserved morpho-electric properties of human and rodent L5 ET neurons. Divergent properties were often subtler than differences between L5 cell types within these two species. These data suggest a conserved function of L5 ET neurons in the neocortical hierarchy but also highlight phenotypic divergence possibly related to functional specialization of human neocortex.

Functional enhancer elements drive subclass-selective expression from mouse to primate neocortex.

Viral genetic tools that target specific brain cell types could transform basic neuroscience and targeted gene therapy. Here, we use comparative open chromatin analysis to identify thousands of human-neocortical-subclass-specific putative enhancers from across the genome to control gene expression in adeno-associated virus (AAV) vectors. The cellular specificity of reporter expression from enhancer-AAVs is established by molecular profiling after systemic AAV delivery in mouse. Over 30% of enhancer-AAVs produce specific expression in the targeted subclass, including both excitatory and inhibitory subclasses. We present a collection of Parvalbumin (PVALB) enhancer-AAVs that show highly enriched expression not only in cortical PVALB cells but also in some subcortical PVALB populations. Five vectors maintain PVALB-enriched expression in primate neocortex. These results demonstrate how genome-wide open chromatin data mining and cross-species AAV validation can be used to create the next generation of non-species-restricted viral genetic tools.

Stereotactic Brain Biopsy Hemorrhage Risk Factors and Implications for Postoperative Care at a Single Institution: An Argument For Postoperative Imaging.

OBJECTIVE: To determine preoperative factors contributing to postoperative hemorrhage after stereotactic brain biopsy (STB), clinical implications of postoperative hemorrhage, and the role of postoperative imaging in clinical management. METHODS: Retrospective review of STB (2005-2018) across 2 institutions including patients aged >18 years undergoing first STB. Patients with prior craniotomy, open biopsy, or prior STB were excluded. Preoperative variables included age, sex, neurosurgeon seniority, STB method. Postoperative variables included pathology, postoperative hemorrhage on computed tomography, immediate and 30-day postoperative seizure, infection, postoperative hospital stay duration, and 30-day return to operating room (OR). Analysis used the Fisher exact tests for categorical variables. RESULTS: Overall, 410 patients were included. Average age was 56.5 (±16.5) years; 60% (n = 248) were men. The majority of biopsies were performed by senior neurosurgeons (66%, n = 270); frontal lobe (42%, n = 182) and glioblastoma (45%, n = 186) were the most common location and pathology. Postoperative hemorrhage occurred in 28% (114) of patients with 20% <0.05 cm3 and 8% >0.05 cm3. Postoperative hemorrhage of any size was associated with increased rate of postoperative deficit within both 24 hours and 30 days, postoperative seizure, and length of hospital stay when controlling for pathology. Hemorrhages >0.05 cm3 had a 16% higher rate of return to the OR for evacuation, due to clinical deterioration as opposed to radiographic progression. CONCLUSIONS: Postbiopsy hemorrhage was associated with higher risk of immediate and delayed postoperative deficit and seizure. Postoperative computed tomography should be used to determine whether STB patients can be discharged same day or admitted for observation; clinical evaluation should determine return to OR for evacuation.

Evaluating angioarchitectural characteristics of glial and metastatic brain tumors with conventional magnetic resonance imaging.

Primary and metastatic brain tumors can overlap in traditional imaging features detected on preoperative conventional magnetic resonance imaging (MRI). The research objective was to determine whether morphological vascular characteristics present in routine preoperative imaging using traditional MRI sequences are predictive of primary versus metastatic brain tumors; secondarily to determine association of conventional and vascular-related imaging parameters with intraoperative blood loss, pathological invasion, and World Health Organization (WHO) tumor grade. A retrospective review analyzed 100 consecutive intracranial tumor surgeries, 50 WHO grade II-IV gliomas and 50 intracranial metastases. Two blinded expert readers independently evaluated preoperative MRIs, obtained via standard morphological imaging sequences, for adjacent or intra-tumoral arterial aneurysm, peritumoral venous ectasia, prominence, or engorgement ("aberrant peritumoral vessels"), and prominent intra-tumoral flow voids. Multivariate analysis was performed to develop models predictive of glioma and glioblastoma (GBM). Aberrant peritumoral vessels and prominent intra-tumoral flow voids were statistically significant predictors of glioma in univariate analyses (p = 0.048, p = 0.001, respectively) and when combined in multivariate analysis (OR = 5.23, p = 0.001), particularly for GBM (OR = 9.08, p < 0.001). Multivariate modeling identified prominent intra-tumoral flow voids and FLAIR invasion as the strongest combined predictors of gliomas and GBM. Aberrant peritumoral vessels and larger tumor volume predicted higher intraoperative blood loss in all analyses. No vascular-related parameters predicted pathological invasion on multivariate analysis. Aberrant peritumoral vessels and prominent intra-tumoral flow voids were predictive of gliomas, specifically GBM. These vascular characteristics, evaluated on routine clinical preoperative MRI imaging, may aid in distinguishinggliomafrom brainmetastases andmay predict intraoperative blood loss.

Category-specific recognition and naming deficits following resection of a right anterior temporal lobe tumor in a patient with atypical language lateralization.

We present a patient with right-hemispheric speech lateralization who exhibited severe recognition and naming deficits for unique objects (famous faces and landmarks) and grossly normal recognition and naming performances for nonunique objects (animals and man-made objects) following an anterior right temporal lobe (TL) resection of a ganglioglioma. While recognition deficits have been reported for famous faces following right temporal pole lesions, and for landmarks and geographic regions following right TL damage in general, this is the first reported case of both recognition and naming deficits for these objects resulting from a single lesion. These results are consistent with research suggesting that the neuroanatomic substrates for the recognition and naming of unique objects lie in the anterior TL regions. Left temporal pole lesions have been associated with naming deficits for unique objects while right temporal pole lesions have been associated with recognition deficits for unique objects. However, these findings suggest that the substrates of naming can be located in homotopic regions of the right hemisphere when language lateralization is atypical. As various object categories appear to have different neuroanatomical representations in the TLs, we discuss the possible benefits of sampling a wider array of objects during cortical stimulation mapping of language.

Regional hypoxia in glioblastoma multiforme quantified with [18F]fluoromisonidazole positron emission tomography before radiotherapy: correlation with time to progression and survival.

PURPOSE: Hypoxia is associated with resistance to radiotherapy and chemotherapy and activates transcription factors that support cell survival and migration. We measured the volume of hypoxic tumor and the maximum level of hypoxia in glioblastoma multiforme before radiotherapy with [(18)F]fluoromisonidazole positron emission tomography to assess their impact on time to progression (TTP) or survival. EXPERIMENTAL DESIGN: Twenty-two patients were studied before biopsy or between resection and starting radiotherapy. Each had a 20-minute emission scan 2 hours after i.v. injection of 7 mCi of [(18)F]fluoromisonidazole. Venous blood samples taken during imaging were used to create tissue to blood concentration (T/B) ratios. The volume of tumor with T/B values above 1.2 defined the hypoxic volume (HV). Maximum T/B values (T/B(max)) were determined from the pixel with the highest uptake. RESULTS: Kaplan-Meier plots showed shorter TTP and survival in patients whose tumors contained HVs or tumor T/B(max) ratios greater than the median (P < or = 0.001). In univariate analyses, greater HV or tumor T/B(max) were associated with shorter TTP or survival (P < 0.002). Multivariate analyses for survival and TTP against the covariates HV (or T/B(max)), magnetic resonance imaging (MRI) T1Gd volume, age, and Karnovsky performance score reached significance only for HV (or T/B(max); P < 0.03). CONCLUSIONS: The volume and intensity of hypoxia in glioblastoma multiforme before radiotherapy are strongly associated with poorer TTP and survival. This type of imaging could be integrated into new treatment strategies to target hypoxia more aggressively in glioblastoma multiforme and could be applied to assess the treatment outcomes.

Patterns of Failure After Stereotactic Radiosurgery for Recurrent High-Grade Glioma: A Single Institution Experience of 10 Years.

BACKGROUND: Stereotactic radiosurgery (SRS) is a treatment modality that is frequently used as salvage therapy for small nodular recurrent high-grade gliomas (HGG). Due to the infiltrative nature of HGG, it is unclear if this highly focused technique provides a durable local control benefit. OBJECTIVE: To determine how demographic or clinical factors influence the pattern of failure following SRS for recurrent high-grade gliomas. METHODS: We retrospectively reviewed clinical, radiographic, and follow-up information for 47 consecutive patients receiving SRS for recurrent HGG at our institution between June 2006 and July 2016. All patients initially presented with an HGG (WHO grade III and IV). Following SRS for recurrence, all patients experienced treatment failure, and we evaluated patterns of local, regional, and distant failure in relation to the SRS 50% isodose line. RESULTS: Most patients with recurrent HGG developed "in-field" treatment failure following SRS (n = 40; 85%). Higher SRS doses were associated with longer time to failure (hazards ratio = 0.80 per 1 Gy increase; 95% confidence interval 0.67-0.96; P = .016). There was a statistically significant increase in distant versus in-field failure among older patients (P = .035). This effect was independent of bevacizumab use (odds ratio = 0.54, P = 1.0). CONCLUSION: Based on our experience, the majority of treatment failures after SRS for recurrent HGG were "in-field." Older patients, however, presented with more distant failures. Our results indicate that higher SRS doses delivered to a larger area as fractioned or unfractioned regimen may prolong time to failure, especially in the older population.

Positron emission tomography-guided conformal fast neutron therapy for glioblastoma multiforme.

Glioblastoma multiforme (GBM) continues to be a difficult therapeutic challenge. Our study was conducted to determine whether improved survival and tumor control could be achieved with modern delivery of fast neutron radiation using three-dimensional treatment planning. Ten patients were enrolled. Eligibility criteria included pathologic diagnosis of GBM, age >or=18 years, and KPS >or=60. Patients underwent MRI and (18)F-fluorodeoxyglucose PET (FDG PET) as part of initial three-dimensional treatment planning. Sequential targets were treated with noncoplanar fields to a total dose of 18 Gy in 16 fractions over 4 weeks. Median and 1-year overall survival were 55 weeks and 60%, respectively. One patient remains alive at last follow-up 255 weeks after diagnosis. Median progression-free survival was 16 weeks, and all patients had tumor progression by 39 weeks. Treatment was clinically well tolerated, but evidence of mild to moderate gliosis and microvascular sclerosis consistent with radiation injury was observed at autopsy in specimens taken from regions of contralateral brain that received approximately 6-10 Gy. Fast neutron radiation using modern imaging, treatment planning, and beam delivery was feasible to a total dose of 18 Gy, but tumor control probability was poor in comparison to that predicted from a dose-response model based on older studies. Steep dose-response curves for both tumor control and neurotoxicity continue to present a challenge to establishing a therapeutic window for fast neutron radiation in GBM, even with modern techniques.

Category-specific naming and recognition deficits in temporal lobe epilepsy surgical patients.

OBJECTIVE: Based upon Damasio's "convergence zone" model of semantic memory, we predicted that epilepsy surgical patients with anterior temporal lobe (TL) seizure onset would exhibit a pattern of category-specific naming and recognition deficits not observed in patients with seizures arising elsewhere. METHODS: We assessed epilepsy patients with unilateral seizure onset of anterior TL or other origin (n=22), pre- or post-operatively, using a set of category-specific items and a conventional measure of visual naming (Boston Naming Test: BNT). RESULTS: Category-specific naming deficits were exhibited by patients with dominant anterior TL seizure onset/resection for famous faces and animals, while category-specific recognition deficits for these same categories were exhibited by patients with nondominant anterior TL onset/resection. Patients with other seizure onset did not exhibit category-specific deficits. Naming and recognition deficits were frequently not detected by the BNT, which samples only a limited range of stimuli. INTERPRETATION: Consistent with the "convergence zone" framework, results suggest that the nondominant anterior TL plays a major role in binding sensory information into conceptual percepts for certain stimuli, while dominant TL regions function to provide a link to verbal labels for these percepts. Although observed category-specific deficits were striking, they were often missed by the BNT, suggesting that they are more prevalent than recognized in both pre- and post-surgical epilepsy patients. Systematic investigation of these deficits could lead to more refined models of semantic memory, aid in the localization of seizures, and contribute to modifications in surgical technique and patient selection in epilepsy surgery to improve neurocognitive outcome.

Sparse recurrent excitatory connectivity in the microcircuit of the adult mouse and human cortex.

Generating a comprehensive description of cortical networks requires a large-scale, systematic approach. To that end, we have begun a pipeline project using multipatch electrophysiology, supplemented with two-photon optogenetics, to characterize connectivity and synaptic signaling between classes of neurons in adult mouse primary visual cortex (V1) and human cortex. We focus on producing results detailed enough for the generation of computational models and enabling comparison with future studies. Here, we report our examination of intralaminar connectivity within each of several classes of excitatory neurons. We find that connections are sparse but present among all excitatory cell classes and layers we sampled, and that most mouse synapses exhibited short-term depression with similar dynamics. Synaptic signaling between a subset of layer 2/3 neurons, however, exhibited facilitation. These results contribute to a body of evidence describing recurrent excitatory connectivity as a conserved feature of cortical microcircuits.

h-Channels Contribute to Divergent Intrinsic Membrane Properties of Supragranular Pyramidal Neurons in Human versus Mouse Cerebral Cortex.

Gene expression studies suggest that differential ion channel expression contributes to differences in rodent versus human neuronal physiology. We tested whether h-channels more prominently contribute to the physiological properties of human compared to mouse supragranular pyramidal neurons. Single-cell/nucleus RNA sequencing revealed ubiquitous HCN1-subunit expression in excitatory neurons in human, but not mouse, supragranular layers. Using patch-clamp recordings, we found stronger h-channel-related membrane properties in supragranular pyramidal neurons in human temporal cortex, compared to mouse supragranular pyramidal neurons in temporal association area. The magnitude of these differences depended upon cortical depth and was largest in pyramidal neurons in deep L3. Additionally, pharmacologically blocking h-channels produced a larger change in membrane properties in human compared to mouse neurons. Finally, using biophysical modeling, we provide evidence that h-channels promote the transfer of theta frequencies from dendrite-to-soma in human L3 pyramidal neurons. Thus, h-channels contribute to between-species differences in a fundamental neuronal property.

Defining Glioblastoma Resectability Through the Wisdom of the Crowd: A Proof-of-Principle Study.

BACKGROUND: Extent of resection (EOR) correlates with glioblastoma outcomes. Resectability and EOR depend on anatomical, clinical, and surgeon factors. Resectability likely influences outcome in and of itself, but an accurate measurement of resectability remains elusive. An understanding of resectability and the factors that influence it may provide a means to control a confounder in clinical trials and provide reference for decision making. OBJECTIVE: To provide proof of concept of the use of the collective wisdom of experienced brain tumor surgeons in assessing glioblastoma resectability. METHODS: We surveyed 13 academic tumor neurosurgeons nationwide to assess the resectability of newly diagnosed glioblastoma. Participants reviewed 20 cases, including digital imaging and communications in medicine-formatted pre- and postoperative magnetic resonance images and clinical vignettes. The selected cases involved a variety of anatomical locations and a range of EOR. Participants were asked about surgical goal, eg, gross total resection, subtotal resection (STR), or biopsy, and rationale for their decision. We calculated a "resectability index" for each lesion by pooling responses from all 13 surgeons. RESULTS: Neurosurgeons' individual surgical goals varied significantly ( P = .015), but the resectability index calculated from the surgeons' pooled responses was strongly correlated with the percentage of contrast-enhancing residual tumor ( R = 0.817, P < .001). The collective STR goal predicted intraoperative decision of intentional STR documented on operative notes ( P < .01) and nonresectable residual ( P < .01), but not resectable residual. CONCLUSION: In this pilot study, we demonstrate the feasibility of measuring the resectability of glioblastoma through crowdsourcing. This tool could be used to quantify resectability, a potential confounder in neuro-oncology clinical trials.

[F-18]-fluorodeoxyglucose positron emission tomography for targeting radiation dose escalation for patients with glioblastoma multiforme: clinical outcomes and patterns of failure.

PURPOSE: [F-18]-fluorodeoxyglucose positron emission tomography (FDG-PET) imaging for brain tumors has been shown to identify areas of active disease. Radiation dose escalation in the treatment of glioblastoma multiforme may lead to improved disease control. Based on these premises, we initiated a prospective study of FDG-PET for the treatment planning of radiation dose escalation for the treatment of glioblastoma multiforme. METHODS AND MATERIALS: Forty patients were enrolled. Patients were treated with standard conformal fractionated radiotherapy with volumes defined by MRI imaging. When patients reached a dose of 45-50.4 Gy, they underwent FDG-PET imaging for boost target delineation, for an additional 20 Gy (2 Gy per fraction) to a total dose of 79.4 Gy (n = 30). RESULTS: The estimated 1-year and 2-year overall survival (OS) for the entire group was 70% and 17%, respectively, with a median overall survival of 70 weeks. The estimated 1-year and 2-year progression-free survival (PFS) was 18% and 3%, respectively, with a median of 24 weeks. No significant improvements in OS or PFS were observed for the study group in comparison to institutional historical controls. CONCLUSIONS: Radiation dose escalation to 79.4 Gy based on FDG-PET imaging demonstrated no improvement in OS or PFS. This study establishes the feasibility of integrating PET metabolic imaging into radiotherapy treatment planning.

Flow-Related Aneurysm within Glioblastoma: A Case Report and Review of Literature.

BACKGROUND: Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults, with a median survival of 13 months despite surgery and chemoradiation. GBMs are often hypervascular tumors caused by abnormal oversecretion of growth factors such as vascular endothelial growth factor. These angiogenic factors are hypothesized to promote increased blood flow and possibly secondary changes to arterial walls, thus facilitating the formation of flow-related aneurysms. CASE DESCRIPTION: A 59-year-old woman presented with headaches, confusion, nausea and emesis. Computed tomography and magnetic resonance imaging revealed a hypervascular lesion, likely high-grade glioma, in the right frontal lobe, with a dilated vessel within the tumor. Cerebral angiography demonstrated a flow-related aneurysm on the right frontopolar artery supplying the tumor. The aneurysm was embolized with coils and the patient later underwent craniotomy for near total resection of the lesion without complications. Final pathology returned GBM with dilated vessels noted. CONCLUSIONS: Hypervascular lesions, such as GBMs, may be associated with flow-related aneurysms on feeding arteries, but aneurysms within the gross tumor are unusual. Although rare, this finding needs to be recognized on preoperative imaging before tumor resection to prevent potentially catastrophic intraoperative complications.

Safety and efficacy of carmustine (BCNU) wafers for metastatic brain tumors.

BACKGROUND: Carmustine (BCNU) wafers (Gliadel) prolongs local disease control and progression-free survival (PFS) in patients with malignant gliomas. However, in metastatic brain tumors, there is a paucity of evidence in support of its safety and efficacy. The goal of this study was to assess the safety and efficacy of Gliadel wafers in patients with metastatic brain tumors. METHODS: We retrospectively reviewed the University of Washington experience with Gliadel wafers for metastatic brain tumors between 2000 and 2015. RESULTS: Gliadel wafers were used in 14 patients with metastatic brain tumors during the period reviewed. There were no postoperative seizures, strokes, or hemorrhages. There was one postoperative wound infection necessitating return to the operating room. The mean time to tumor progression (n = 7) and death (n = 5) after Gliadel wafer implantation was 2.5 and 2.9 years, respectively. Age was the only variable affecting PFS in patients receiving Gliadel wafers. Patients <53 years old (n = 7) had a PFS of 0.52 years, whereas patients >53 years old (n = 7) had a PFS of 4.29 years (P = 0.02). There was no significant difference in PFS in relation to presenting Karnofsky Performance Status (P = 0.26), number of brain metastasis (P = 0.82), tumor volume (P = 0.54), prior surgery (P = 0.57), or prior radiation (P = 0.41). There were no significant differences in the mean survival in relationship to any variable including age. CONCLUSIONS: BCNU wafers are a safe and a potentially efficacious adjunct to surgery and radiation for improving local disease control in metastatic brain tumors. Larger studies, however, are needed to examine overall efficacy and tumor specific efficacy.

TWIST is expressed in human gliomas and promotes invasion.

TWIST, a basic helix-loop-helix (bHLH) transcription factor that regulates mesodermal development, has been shown to promote tumor cell metastasis and to enhance survival in response to cytotoxic stress. Our analysis of rat C6 glioma cell-derived cDNA revealed TWIST expression, suggesting that the gene may play a role in the genesis and physiology of primary brain tumors. To further delineate a possible oncogenic role for TWIST in the central nervous system (CNS), we analyzed TWIST expression in human gliomas and normal brain by using reverse transcription polymerase chain reaction, Northern blot analysis, in situ hybridization, and immunohistochemistry. TWIST expression was detected in the large majority of human glioma-derived cell lines and human gliomas examined. Levels of TWIST mRNA were associated with the highest grade gliomas, and increased TWIST expression accompanied transition from low grade to high grade in vivo, suggesting a role for TWIST in promoting malignant progression. In accord, elevated TWIST mRNA abundance preceded the spontaneous malignant transformation of cultured mouse astrocytes hemizygous for p53. Overexpression of TWIST protein in a human glioma cell line significantly enhanced tumor cell invasion, a hallmark of high-grade gliomas. These findings support roles for TWIST both in early glial tumorigenesis and subsequent malignant progression. TWIST was also expressed in embryonic and fetal human brain, and in neurons, but not glia, of mature brain, indicating that, in gliomas, TWIST may promote the functions also critical for CNS development or normal neuronal physiology.

Apurinic endonuclease activity in adult gliomas and time to tumor progression after alkylating agent-based chemotherapy and after radiotherapy.

PURPOSE: Apurinic/apyrimidinic endonuclease (Ap endo) is a key DNA repair enzyme that cleaves DNA at cytotoxic abasic sites caused by alkylating agents and radiation. We have observed that human glioma cells deficient in Ap endo activity are hypersensitive to clinically used alkylators (Silber et al., Clin Cancer Res 2002;8:3008.). Here we examine the association of glioma Ap endo activity with clinical response after alkylating agent-based chemotherapy or after radiotherapy. EXPERIMENTAL DESIGN: Cox proportional hazards regression models were used to analyze the relationship of Ap endo activity with time to tumor progression (TTP). RESULTS: In a univariate model with Ap endo activity entered as a continuous variable, the hazard ratio (HR) for progression after alkylator therapy in 30 grade III gliomas increased by a factor of 1.061 for every 0.01 increase in activity (P = 0.013). Adjusting for age, gender, extent of resection, and prior treatment strengthened slightly the association (HR = 1.094; P = 0.003). Similarly, the HR for progression after radiotherapy in 44 grade II and III tumors increased by a factor of 1.069 (P = 0.008). Adjusting for the aforementioned variables had little effect on the association. In contrast, we observed no association between activity and TTP in grade IV gliomas after either alkylator therapy in 34 tumors or radiotherapy in 26 tumors. CONCLUSIONS: Our data suggest that Ap endo activity mediates resistance to alkylating agents and radiation and may be a useful predictor of progression after adjuvant therapy in a subset of gliomas.