Consultative issues in surgical neuropathology: a retrospective review of the rationale for submitting cases for expert review

OBJECTIVES

Second opinions on neuropathology cases are sought for a variety of reasons. We investigated the rationales for seeking expert neuropathologic review.

METHODS

A retrospective review was done of the correspondence accompanying neuropathology cases submitted over a 5-year period. The review used a taxonomy of referral reasons, the submitting diagnoses, and requests for ancillary tests.

RESULTS

In total, 508 adult cases were submitted, including glioblastoma (n = 94), anaplastic astrocytoma (n = 49), low-grade glioma (n = 49), oligodendroglioma (n = 48), and pituitary adenoma (n = 12). Thirty-nine cases submitted requested ancillary testing. A taxonomy of four categories revealed the following: preliminary diagnosis (n = 228 cases) was the most common reason for requesting review, followed by no diagnosis rendered (n = 183 cases), second opinion (n = 53), and confirmation/quality assurance (n = 43); the remaining case was "other." Overall, 456 cases were submitted by pathologists, 40 by clinicians and 12 by patients.

CONCLUSIONS

Pathologists who predominately submit cases with a preliminary diagnosis rendered seek expert consultation while clinicians seek a second opinion.

Supratentorial tanycytic ependymoma in an adult male: case report and review of literature

Ependymomas, tumors of the ependymal cells, are very rare and usually present in the pediatric population. Furthermore, there are even rarer variants of ependymomas that can include cellular, papillary, clear cell, and tanycytic subtypes. We present a case of a supratentorial tanycytic ependymoma in an adult male and review the literature in regard to this rare primary central nervous system neoplasm.

Tetanus toxoid and CCL3 improve dendritic cell vaccines in mice and glioblastoma patients

Upon stimulation, dendritic cells (DCs) mature and migrate to draining lymph nodes to induce immune responses¹. As such, autologous DCs generated ex vivo have been pulsed with tumor antigens and injected back into patients as immunotherapy. While DC vaccines have shown limited promise in the treatment of patients with advanced cancers^2–4 including glioblastoma (GBM),^5–7 the factors dictating DC vaccine efficacy remain poorly understood. Here we demonstrate that pre-conditioning the vaccine site with a potent recall antigen such as tetanus/diphtheria (Td) toxoid can significantly improve the lymph node homing and efficacy of tumor antigen-specific DCs. To assess the impact of vaccine site pre-conditioning in humans, we randomized patients with GBM to pre-conditioning with mature DCs⁸ or Td unilaterally before bilateral vaccination with Cytomegalovirus pp65 RNA-pulsed DCs. We and other laboratories have shown that pp65 is expressed in > 90% of GBM specimens but not surrounding normal brain^9–12, providing an unparalleled opportunity to subvert this viral protein as a tumor-specific target. Patients given Td had enhanced DC migration bilaterally and significantly improved survival. In mice, Td pre-conditioning also enhanced bilateral DC migration and suppressed tumor growth in a manner dependent on the chemokine CCL3. Our clinical studies and corroborating investigations in mice suggest that pre-conditioning with a potent recall antigen may represent a viable strategy to improve antitumor immunotherapy.

Mutations in IDH1, IDH2, and in the TERT promoter define clinically distinct subgroups of adult malignant gliomas

Frequent mutations in isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) and the promoter of telomerase reverse transcriptase (TERT) represent two significant discoveries in glioma genomics. Understanding the degree to which these two mutations co-occur or occur exclusively of one another in glioma subtypes presents a unique opportunity to guide glioma classification and prognosis. We analyzed the relationship between overall survival (OS) and the presence of IDH1/2 and TERT promoter mutations in a panel of 473 adult gliomas. We hypothesized and show that genetic signatures capable of distinguishing among several types of gliomas could be established providing clinically relevant information that can serve as an adjunct to histopathological diagnosis. We found that mutations in the TERT promoter occurred in 74.2% of glioblastomas (GBM), but occurred in a minority of Grade II-III astrocytomas (18.2%). In contrast, IDH1/2 mutations were observed in 78.4% of Grade II-III astrocytomas, but were uncommon in primary GBM. In oligodendrogliomas, TERT promoter and IDH1/2 mutations co-occurred in 79% of cases. Patients whose Grade III-IV gliomas exhibit TERT promoter mutations alone predominately have primary GBMs associated with poor median OS (11.5 months). Patients whose Grade III-IV gliomas exhibit IDH1/2 mutations alone predominately have astrocytic morphologies and exhibit a median OS of 57 months while patients whose tumors exhibit both TERT promoter and IDH1/2 mutations predominately exhibit oligodendroglial morphologies and exhibit median OS of 125 months. Analyzing gliomas based on their genetic signatures allows for the stratification of these patients into distinct cohorts, with unique prognosis and survival.

The genetic landscape of anaplastic astrocytoma

Anaplastic astrocytoma WHO grade III (A3) is a lethal brain tumor that often occurs in middle aged patients. Clinically, it is challenging to distinguish A3 from glioblastoma multiforme (GBM) WHO grade IV. To reveal the genetic landscape of this tumor type, we sequenced the exome of a cohort of A3s (n=16). For comparison and to illuminate the genomic landscape of other glioma subtypes, we also included in our study diffuse astrocytoma WHO grade II (A2, n=7), oligoastrocytoma WHO grade II (OA2, n=2), anaplastic oligoastrocytoma WHO grade III (OA3, n=4), and GBM (n=28). Exome sequencing of A3s identified frequent mutations in IDH1 (75%, 12/16), ATRX (63%, 10/16), and TP53 (82%, 13/16). In contrast, the majority of GBMs (75%, 21/28) did not contain IDH1 or ATRX mutations, and displayed a distinct spectrum of mutations. Finally, our study also identified novel genes that were not previously linked to this tumor type. In particular, we found mutations in Notch pathway genes (NOTCH1, NOTCH2, NOTCH4, NOTCH2NL), including a recurrent NOTCH1-A465Tmutation, in 31% (5/16) of A3s. This study suggests genetic signatures will be useful for the classification of gliomas.

Abstract 63: Driving brain tumorigenesis: Generation of a mutant IDH1 mouse model of progressive glioma

Despite decades worth of research, glioblastoma remains one of the most lethal cancers. The identification of IDH1 as a major cancer gene in glioblastoma provides a great opportunity for improving our understanding, diagnostics and treatment of this disease. Recent studies from our laboratory characterized the genetic landscape of gliomas and have shown the cooperation between IDH1 mutations and other oncogenic alterations including TP53 mutations. Normally, IDH1 functions in the oxidative decarboxylation of isocitrate to α-ketoglutarate, however, the mutant form confers neomorphic enzymatic activity by producing D-2-hydroxyglutarate, an oncometabolite responsible for aberrant methylation in IDH1-mutated tumors. To determine the role of mutant IDH1 in vivo, we generated a conditional knockin mouse model that produces D-2-hydroxyglutarate. This genetically faithful system is biologically and clinically relevant and will promote the understanding of mutant IDH1-mediated tumorigenesis while offering a route for therapeutic targeting.

We observed that broad expression of mutant IDH1 throughout the brain leads to hydrocephalus in 80% of animals. To obviate these deleterious effects, we restricted expression of mutant IDH1 to the neural stem cell population. Animals were sacrificed after one year, at which time we observed mild hydrocephalus in several animals. Recapitulating the genetics of human tumors, we sought to determine the synergistic effects between mutant IDH1 and deletion of P53. We observed development of low- and high-grade gliomas in approximately 14% of animals. Tumors developed in both P53 deleted animals as well as in mutant IDH1/P53 deleted animals, with mutant IDH1 expressed in tumors of the latter cohort. Differences in latency, penetrance, differentiation, and epigenetic modifications are being assessed. Additionally, we are determining the cell fate of IDH1-mutant cells over time to assess the biological effects of the mutation on the behavior and differentiation of neural stem cells. Lastly, to decrease the latency and increase the penetrance of tumor formation, an orthotopic intracranial injection model is being generated to allow for visualization of tumor formation and development, as well as investigation of therapeutic modalities. Understanding the biological effects of the most common mutations found in gliomas will bring us strides closer to determining mechanisms and therapeutic targets for IDH1-mutated cancers.

Citation Format: Christopher J. Pirozzi, Catherine Y. Wang, Austin B. Carpenter, Huishan Zhu, Paula K. Greer, Roger E. McLendon, Darell D. Bigner, Yiping He, Hai Yan. Driving brain tumorigenesis: Generation of a mutant IDH1 mouse model of progressive glioma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 63. doi:10.1158/1538-7445.AM2014-63

Abstract LB-82: MLL2 maintains neoplastic cell growth and global histone H3 lysine 4 monomethylation

One striking theme emerging from recent findings in cancer genetics is that chromatin remodeling and histone methylation modifiers are frequently altered in human cancers. Among these newly identified cancer genes, one of the best examples is the gene encoding MLL2 (KMT2D, a.k.a. ALR/MLL4), a histone lysine methyltransferase that plays an important role in regulating gene transcription. Genetic alterations suggestive of a functional deficiency in MLL2 and other genes in the same pathways are common. The identification of alterations in MLL2 suggests potential new opportunities for therapeutics, and highlights an urgent need to understand the underlying tumorigenic mechanism. Filling such a knowledge gap has been challenging, due to the lack of appropriate assays for the gigantic (∼600 kDa), understudied MLL2 protein.

To overcome the difficulty, we have used innovative somatic gene editing-based assays to determine the effect of an MLL2 deficiency on neoplastic cells. In particular, we have used homologous recombination- and nuclease-mediated gene editing approaches to generate a panel of isogenic human cancer cell lines that differ with respect to their endogenous MLL2 status.

Our studies found that an MLL2 deficiency results in attenuated cancer cell proliferation and defective cell migration. We identified direct transcriptional target genes and revealed the connection of MLL2 to multiple cellular signaling pathways. Analysis of histone H3 modifications revealed that MLL2 is essential for maintaining the level of global histone H3 lysine 4 (H3K4) monomethylation and that its enzymatic SET domain is directly responsible for this function. Furthermore, we found that a majority of MLL2 binding sites are located in regions of potential enhancer elements. The finding concerning enhancer elements is significant, as enhancer elements have increasingly been recognized as critically involved in tumorigenesis.

Together, these findings revealed the role of MLL2 in mediating diverse signaling pathways and regulating enhancer elements in human cells, and shed light on the tumorigenic role of its deficiency. Our study supports that MLL2 has distinct roles in neoplastic cells, as opposed to pre-neoplastic cells, and that inhibiting MLL2 may be a viable strategy for cancer therapeutics.

Citation Format: Changcun Guo, Lee H. Chen, Yafen Huang, Chun-chi Chang, Ping Wang, Christopher J. Pirozzi, Xiaoxia Qin, Xuhui Bao, Paula K. Greer, Roger E. McLendon, Hai Yan, Stephen T. Keir, Darell D. Bigner, Yiping He. MLL2 maintains neoplastic cell growth and global histone H3 lysine 4 monomethylation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-82. doi:10.1158/1538-7445.AM2014-LB-82

miR-33a promotes glioma-initiating cell self-renewal via PKA and NOTCH pathways

Glioblastoma (GBM) is the most common and lethal brain tumor in adults. Glioma-initiating cells (GICs) are stem-like cells that have been implicated in glioblastoma progression and recurrence; however, the distinct properties of GICs and non-GICs within GBM tumors are largely uncharacterized. Here, we evaluated stem cell-associated microRNA (miR) expression in GICs from GBM patients and GICs derived from xenografted human glioma cell lines and determined that miR-33a promotes GIC growth and self-renewal. Moreover, evaluation of a GBM tissue array revealed that higher miR-33a expression was associated with poor prognosis of GBM patients. Antagonizing miR-33a function in GICs reduced self-renewal and tumor progression in immune-compromised mice, whereas overexpression of miR-33a in non-GICs promoted the display of features associated with GICs. We identified the mRNAs encoding phosphodiesterase 8A (PDE8A) and UV radiation resistance-associated gene (UVRAG) as direct miR-33a targets. PDE8A and UVRAG negatively regulated the cAMP/PKA and NOTCH pathways, respectively; therefore, miR-33a-dependent reduction of these proteins promoted growth and self-renewal of GICs by enhancing PKA and NOTCH activity. Furthermore, in GBM specimens, there was an inverse correlation between the expression levels of miR-33a and PDE8A and UVRAG expression. These findings reveal a miR-33a-centered signaling network that promotes GIC maintenance and has potential as a therapeutic target for GBM treatment.

EGFR phosphorylation of DCBLD2 recruits TRAF6 and stimulates AKT-promoted tumorigenesis

Aberrant activation of EGFR in human cancers promotes tumorigenesis through stimulation of AKT signaling. Here, we determined that the discoidina neuropilin-like membrane protein DCBLD2 is upregulated in clinical specimens of glioblastomas and head and neck cancers (HNCs) and is required for EGFR-stimulated tumorigenesis. In multiple cancer cell lines, EGFR activated phosphorylation of tyrosine 750 (Y750) of DCBLD2, which is located within a recently identified binding motif for TNF receptor-associated factor 6 (TRAF6). Consequently, phosphorylation of DCBLD2 Y750 recruited TRAF6, leading to increased TRAF6 E3 ubiquitin ligase activity and subsequent activation of AKT, thereby enhancing EGFR-driven tumorigenesis. Moreover, evaluation of patient samples of gliomas and HNCs revealed an association among EGFR activation, DCBLD2 phosphorylation, and poor prognoses. Together, our findings uncover a pathway in which DCBLD2 functions as a signal relay for oncogenic EGFR signaling to promote tumorigenesis and suggest DCBLD2 and TRAF6 as potential therapeutic targets for human cancers that are associated with EGFR activation.

Malignant brainstem gliomas in adults: clinicopathological characteristics and prognostic factors

Adult malignant brainstem gliomas (BSGs) are poorly characterized due to their relative rarity. We have examined histopathologically confirmed cases of adult malignant BSGs to better characterize the patient and tumor features and outcomes, including the natural history, presentation, imaging, molecular characteristics, prognostic factors, and appropriate treatments. A total of 34 patients were identified, consisting of 22 anaplastic astrocytomas (AAs) and 12 glioblastomas (GBMs). The overall median survival for all patients was 25.8 months, with patients having GBMs experiencing significantly worse survival (12.1 vs. 77.0 months, p = 0.0011). The majority of tumors revealed immunoreactivity for EGFR (93.3 %) and MGMT (64.7 %). Most tumors also exhibited chromosomal abnormalities affecting the loci of epidermal growth factor receptor (92.9 %), MET (100 %), PTEN (61.5 %), and 9p21 (80 %). AAs more commonly appeared diffusely enhancing (50.0 vs. 27.3 %) or diffusely nonenhancing (25.0 vs. 0.0 %), while GBMs were more likely to exhibit focal enhancement (54.6 vs. 10.0 %). Multivariate analysis revealed confirmed histopathology for GBM to significantly affect survival (HR 4.80; 95 % CI 1.86-12.4; p = 0.0012). In conclusion, adult malignant BSGs have an overall poor prognosis, with GBM tumors faring significantly worse than AAs. As AAs and GBMs have differing imaging characteristics, tissue diagnosis may be necessary to accurately determine patient prognosis and identify molecular characteristics which may aid in the treatment of these aggressive tumors.

Efficacy of bevacizumab plus irinotecan in children with recurrent low-grade gliomas--a Pediatric Brain Tumor Consortium study

BACKGROUND

A phase II study of bevacizumab (BVZ) plus irinotecan (CPT-11) was conducted in children with recurrent low-grade glioma to measure sustained response and/or stable disease lasting ≥6 months and progression-free survival.

METHODS

Thirty-five evaluable patients received 2 doses (10 mg/kg each) of single-agent BVZ intravenously 2 weeks apart and then BVZ + CPT-11 every 2 weeks until progressive disease, unacceptable toxicity, or a maximum of 2 years of therapy. Correlative studies included neuroimaging and expression of tumor angiogenic markers (vascular endothelial growth factor [VEGF], VEGF receptor 2, hypoxia-inducible factor 2α, and carbonic anhydrase 9).

RESULTS

Thirty-five evaluable patients (median age 8.4 y [range, 0.6-17.6]) received a median of 12 courses of BVZ + CPT-11 (range, 2-26). Twenty-nine of 35 patients (83%) received treatment for at least 6 months. Eight patients progressed on treatment at a median time of 5.4 months (range, 1-17.8). Six patients (17.7%) still in follow-up have had stable disease without receiving additional treatment for a median of 40.1 months (range, 30.6-49.3) from initiating therapy. The 6-month and 2-year progression-free survivals were 85.4% (SE ± 5.96%) and 47.8% (SE ± 9.27%), respectively. The commonest toxicities related to BVZ included grades 1-2 hypertension in 24, grades 1-2 fatigue in 23, grades 1-2 epistaxis in 18, and grades 1-4 proteinuria in 15. The median volume of enhancement decreased significantly between baseline and day 15 (P < .0001) and over the duration of treatment (P < .037).

CONCLUSION

The combination of BVZ + CPT-11 appears to produce sustained disease control in some children with recurrent low-grade gliomas.

TERT promoter mutations are highly recurrent in SHH subgroup medulloblastoma

Telomerase reverse transcriptase (TERT) promoter mutations were recently shown to drive telomerase activity in various cancer types, including medulloblastoma. However, the clinical and biological implications of TERT mutations in medulloblastoma have not been described. Hence, we sought to describe these mutations and their impact in a subgroup-specific manner. We analyzed the TERT promoter by direct sequencing and genotyping in 466 medulloblastomas. The mutational distributions were determined according to subgroup affiliation, demographics, and clinical, prognostic, and molecular features. Integrated genomics approaches were used to identify specific somatic copy number alterations in TERT promoter-mutated and wild-type tumors. Overall, TERT promoter mutations were identified in 21 % of medulloblastomas. Strikingly, the highest frequencies of TERT mutations were observed in SHH (83 %; 55/66) and WNT (31 %; 4/13) medulloblastomas derived from adult patients. Group 3 and Group 4 harbored this alteration in <5 % of cases and showed no association with increased patient age. The prognostic implications of these mutations were highly subgroup-specific. TERT mutations identified a subset with good and poor prognosis in SHH and Group 4 tumors, respectively. Monosomy 6 was mostly restricted to WNT tumors without TERT mutations. Hallmark SHH focal copy number aberrations and chromosome 10q deletion were mutually exclusive with TERT mutations within SHH tumors. TERT promoter mutations are the most common recurrent somatic point mutation in medulloblastoma, and are very highly enriched in adult SHH and WNT tumors. TERT mutations define a subset of SHH medulloblastoma with distinct demographics, cytogenetics, and outcomes.

KMT2D maintains neoplastic cell proliferation and global histone H3 lysine 4 monomethylation

KMT2D (lysine (K)-specific methyltransferase 2D), formerly named MLL2 (myeloid/lymphoid or mixed-lineage leukemia 2, also known as ALR/MLL4), is a histone methyltransferase that plays an important role in regulating gene transcription. In particular, it targets histone H3 lysine 4 (H3K4), whose methylations serve as a gene activation mark. Recently, KMT2D has emerged as one of the most frequently mutated genes in a variety of cancers and in other human diseases, including lymphoma, medulloblastoma, gastric cancer, and Kabuki syndrome. Mutations in KMT2D identified thus far point to its loss-of-function in pathogenesis and suggest its role as a tumor suppressor in various tissues. To determine the effect of a KMT2D deficiency on neoplastic cells, we used homologous recombination- and nuclease-mediated gene editing approaches to generate a panel of isogenic colorectal and medulloblastoma cancer cell lines that differ with respect to their endogenous KMT2D status. We found that a KMT2D deficiency resulted in attenuated cancer cell proliferation and defective cell migration. Analysis of histone H3 modifications revealed that KMT2D was essential for maintaining the level of global H3K4 monomethylation and that its enzymatic SET domain was directly responsible for this function. Furthermore, we found that a majority of KMT2D binding sites are located in regions of potential enhancer elements. Together, these findings revealed the role of KMT2D in regulating enhancer elements in human cells and shed light on the tumorigenic role of its deficiency. Our study supports that KMT2D has distinct roles in neoplastic cells, as opposed to normal cells, and that inhibiting KMT2D may be a viable strategy for cancer therapeutics.

Bevacizumab (BVZ)-associated toxicities in children with recurrent central nervous system tumors treated with BVZ and irinotecan (CPT-11): a Pediatric Brain Tumor Consortium Study (PBTC-022)

BACKGROUND

The incidence and spectrum of acute toxicities related to the use of bevacizumab (BVZ)-containing regimens in children are largely unknown. This report describes the adverse events in a recently completed large phase 2 trial of BVZ plus irinotecan (CPT-11) in children with recurrent central nervous system tumors.

METHODS

Pediatric Brain Tumor Consortium trial-022 evaluated the efficacy and toxicity of BVZ (10 mg/kg administered intravenously) as a single agent for 2 doses given 2 weeks apart and then combined with CPT-11 every 2 weeks (1 course = 4 weeks) in children with recurrent central nervous system tumors. Children were treated until they experienced progressive disease, unacceptable toxicity or completed up to a maximum of 2 years of therapy. Toxicities were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events, version 3.0. Patients who received at least 1 dose of BVZ were included for toxicity assessment.

RESULTS

Between October 2006 and June 2010, 92 patients evaluable for toxicity were enrolled and received 687 treatment courses. The most common toxicities attributable to BVZ included grade I-III hypertension (38% of patients), grade I-III fatigue (30%), grade I-II epistaxis (24%), and grade I-IV proteinuria (22%). Twenty-two patients (24%) stopped therapy due to toxicity.

CONCLUSIONS

The combination of BVZ and CPT-11 was fairly well-tolerated, and most severe BVZ-related toxicities were rare, self-limiting, and manageable.

Tumor-infiltrating lymphocytes in glioblastoma are associated with specific genomic alterations and related to transcriptional class

PURPOSE

Tumor-infiltrating lymphocytes (TIL) have prognostic significance in many cancers, yet their roles in glioblastoma have not been fully defined. We hypothesized that TILs in glioblastoma are associated with molecular alterations, histologies, and survival.

EXPERIMENTAL DESIGN

We used data from The Cancer Genome Atlas (TCGA) to investigate molecular, histologic, and clinical correlates of TILs in glioblastomas. Lymphocytes were categorized as absent, present, or abundant in histopathologic images from 171 TCGA glioblastomas. Associations were examined between lymphocytes and histologic features, mutations, copy number alterations, CpG island methylator phenotype, transcriptional class, and survival. We validated histologic findings using CD3G gene expression.

RESULTS

We found a positive correlation between TILs and glioblastomas with gemistocytes, sarcomatous cells, epithelioid cells, and giant cells. Lymphocytes were enriched in the mesenchymal transcriptional class and strongly associated with mutations in NF1 and RB1. These mutations are frequent in the mesenchymal class and characteristic of gemistocytic, sarcomatous, epithelioid, and giant cell histologies. Conversely, TILs were rare in glioblastomas with small cells and oligodendroglioma components. Lymphocytes were depleted in the classical transcriptional class and in EGF receptor (EGFR)-amplified and homozygous PTEN-deleted glioblastomas. These alterations are characteristic of glioblastomas with small cells and glioblastomas of the classical transcriptional class. No association with survival was shown.

CONCLUSIONS

TILs were enriched in glioblastomas of the mesenchymal class, strongly associated with mutations in NF1 and RB1 and typical of histologies characterized by these mutations. Conversely, TILs were depleted in the classical class, EGFR-amplified, and homozygous PTEN-deleted tumors and rare in histologies characterized by these alterations.

The integrated landscape of driver genomic alterations in glioblastoma

Glioblastoma is one of the most challenging forms of cancer to treat. Here we describe a computational platform that integrates the analysis of copy number variations and somatic mutations and unravels the landscape of in-frame gene fusions in glioblastoma. We found mutations with loss of heterozygosity in LZTR1, encoding an adaptor of CUL3-containing E3 ligase complexes. Mutations and deletions disrupt LZTR1 function, which restrains the self renewal and growth of glioma spheres that retain stem cell features. Loss-of-function mutations in CTNND2 target a neural-specific gene and are associated with the transformation of glioma cells along the very aggressive mesenchymal phenotype. We also report recurrent translocations that fuse the coding sequence of EGFR to several partners, with EGFR-SEPT14 being the most frequent functional gene fusion in human glioblastoma. EGFR-SEPT14 fusions activate STAT3 signaling and confer mitogen independence and sensitivity to EGFR inhibition. These results provide insights into the pathogenesis of glioblastoma and highlight new targets for therapeutic intervention.

Clinicopathological characteristics and treatment of rhabdoid glioblastoma

Object

Rhabdoid glioblastoma (GB) is an exceedingly rare tumor in which some of the tumor cells possess rhabdoid features such as eccentric nuclei, abundant eosinophilic cytoplasm, and pseudopapillary formations. These tumors are exceptionally aggressive, and leptomeningeal dissemination is common. In the 9 previously reported cases, the longest survival was only 9 months, with a median survival of 17.8 weeks. The authors report the clinicopathological characteristics of 4 cases of rhabdoid GB and demonstrate the utility of intensive temozolomide and adjuvant therapy in these tumors. The authors also review the literature to provide the most comprehensive understanding of these rare tumors to date.

Methods

A retrospective review was performed of patients treated for GB at the Duke University Medical Center between 2004 and 2012. One of two experienced neuropathologists identified 4 cases as being rhabdoid GBs. Immunohistochemistry and fluorescence in situ hybridization analyses were performed in all cases. Kaplan-Meier analysis was used to assess overall survival, with the log-rank test being used to evaluate differences between survival curves. An extensive review of the literature was also performed.

Results

The median age of patients with rhabdoid GB was 30 years. Clinical presentation varied with location, with headache being a presenting symptom in 90% of patients. All lesions were supratentorial, and 45.5% of the cases involved the temporal lobe. Leptomeningeal dissemination occurred in 63.6% of patients, with 1 patient having extracranial metastasis to the scalp and lungs. Fluorescence in situ hybridization revealed epidermal growth factor receptor gain or amplification in all study cases. The median survival in the authors' cohort was significantly higher than that of all previously reported cases (27.5 vs 4.5 months, p = 0.003). Postoperative treatment in the authors' cohort included radiotherapy with concurrent temozolomide, bevacizumab, interleukin 13, CCNU, and/or etoposide.

Conclusions

Enhanced survival in the authors' 4 patients suggests that the current standard of care for the treatment of GB may be beneficial in rhabdoid GB cases, with postoperative radiotherapy and concomitant temozolomide treatment followed by adjuvant therapy. Due to the rapid tumor dissemination associated with these lesions, aggressive and timely therapy is warranted, with frequent surveillance and/or continued therapy despite stable disease. Additionally, patients should undergo full craniospinal imaging to monitor the development of distant metastatic disease.

Intraaxial dermoid cyst of the medulla

Intracranial dermoid cysts are rare congenital lesions that typically occur in the cisternal spaces. However, exceptionally rare cases of intraaxial involvement have been reported, with only 8 cases having been described in the literature. The authors report the first case of an intraaxial dermoid cyst located in the medulla and the first occurrence in an elderly patient. They also review the literature of the existing intraparenchymal cases and provide treatment guidelines. A 66-year-old man presented with slowly progressive dysphagia, left lower-extremity numbness, nausea, and hyperhidrosis. Neurological examination revealed decreased pinprick sensation of the left side of his face and body, and decreased vibratory sensation in his left lower extremity. Additionally, he had an unusual extraocular movement in which abduction of the eye resulted in closure of the contralateral eye. Magnetic resonance imaging revealed a nonenhancing cystic lesion centered in the medulla. The patient underwent a suboccipital craniotomy with laminectomy of C1–2 for excision of the cyst, with subtotal resection due to adherence of the cyst wall to the brainstem. At follow-up 7.5 years after surgery, the patient's neurological examination was stable. Magnetic resonance imaging did not reveal any progression or recurrence of the cyst. As the cyst wall is typically adherent to surrounding structures, resection is usually subtotal due to the risk of neurological deficits. As there have been no cases of progression after subtotal resection, gross-total resection is not warranted for the treatment of these lesions.

Construction of an immunotoxin, D2C7-(scdsFv)-PE38KDEL, targeting EGFRwt and EGFRvIII for brain tumor therapy

PURPOSE

The EGF receptor gene (EGFR) is most frequently amplified and overexpressed, along with its deletion mutant, EGFRvIII, in glioblastoma. We tested the preclinical efficacy of the recombinant immunotoxin, D2C7-(scdsFv)-PE38KDEL, which is reactive with a 55-amino acid (AA) region present in the extracellular domain of both EGFRwt (583-637 AAs) and EGFRvIII (292-346 AAs) proteins.

EXPERIMENTAL DESIGN

The binding affinity and specificity of D2C7-(scdsFv)-PE38KDEL for EGFRwt and EGFRvIII were measured by surface-plasmon resonance and flow cytometry. In vitro cytotoxicity of D2C7-(scdsFv)-PE38KDEL was measured by inhibition of protein synthesis in human EGFRwt-transfected NR6 (NR6W), human EGFRvIII-transfected NR6 (NR6M), EGFRwt-overexpressing A431-epidermoid-carcinoma, and glioblastoma xenograft cells (43, D08-0493MG, D2159MG, and D270MG). In vivo antitumor efficacy of D2C7-(scdsFv)-PE38KDEL was evaluated using 43, NR6M, and D270MG orthotopic tumor models.

RESULTS

The KD of D2C7-(scdsFv)-PE38KDEL for EGFRwt and EGFRvIII was 1.6×10(-9) mol/L and 1.3×10(-9) mol/L, respectively. Flow cytometry with NR6W and NR6M cells confirmed the specificity of D2C7-(scdsFv)-PE38KDEL for EGFRwt and EGFRvIII. The D2C7-(scdsFv)-PE38KDEL IC50 was 0.18 to 2.5 ng/mL on cells expressing EGFRwt (NR6W, A431, 43, and D08-0493MG). The D2C7-(scdsFv)-PE38KDEL IC50 was approximately 0.25 ng/mL on EGFRvIII-expressing cells (NR6M) and on EGFRwt- and EGFRvIII-expressing glioblastoma xenograft cells (D2159MG and D270MG). Significantly, in intracranial tumor models of 43, NR6M, and D270MG, treatment with D2C7-(scdsFv)-PE38KDEL by convection-enhanced delivery prolonged survival by 310% (P=0.006), 28% (P=0.002), and 166% (P=0.001), respectively.

CONCLUSIONS

In preclinical studies, the D2C7-(scdsFv)-PE38KDEL immunotoxin exhibited significant potential for treating brain tumors expressing EGFRwt, EGFRvIII, or both.

Complete response to steroids in dural inflammatory pseudotumor associated with Still's disease

We report a unique case of a dural-based inflammatory pseudotumor (IPT) arising in the left cavernous sinus of a patient with a history of juvenile Still's disease. The patient presented with hemi-facial paresthesias, dull, constant headaches, and transient episodes of sharp pain along the temporalis region. Treatment with oral steroid therapy resulted in complete regression of the lesion and accompanied neuralgia symptoms. Because intracranial IPT can mimic meningiomas both clinically and radiographically and can be associated with systemic arthritic diseases, neurosurgeons should be familiar with this entity in order to avoid unnecessary radical surgery and alternatively consider a tapering course of steroid therapy.

Glioblastoma stem cells generate vascular pericytes to support vessel function and tumor growth

Glioblastomas (GBMs) are highly vascular and lethal brain tumors that display cellular hierarchies containing self-renewing tumorigenic glioma stem cells (GSCs). Because GSCs often reside in perivascular niches and may undergo mesenchymal differentiation, we interrogated GSC potential to generate vascular pericytes. Here, we show that GSCs give rise to pericytes to support vessel function and tumor growth. In vivo cell lineage tracing with constitutive and lineage-specific fluorescent reporters demonstrated that GSCs generate the majority of vascular pericytes. Selective elimination of GSC-derived pericytes disrupts the neovasculature and potently inhibits tumor growth. Analysis of human GBM specimens showed that most pericytes are derived from neoplastic cells. GSCs are recruited toward endothelial cells via the SDF-1/CXCR4 axis and are induced to become pericytes predominantly by transforming growth factor β. Thus, GSCs contribute to vascular pericytes that may actively remodel perivascular niches. Therapeutic targeting of GSC-derived pericytes may effectively block tumor progression and improve antiangiogenic therapy.

Laminin alpha 2 enables glioblastoma stem cell growth

OBJECTIVE

Glioblastomas (GBMs) are lethal cancers that display cellular hierarchies parallel to normal brain. At the apex are GBM stem cells (GSCs), which are relatively resistant to conventional therapy. Interactions with the adjacent perivascular niche are an important driver of malignancy and self-renewal in GSCs. Extracellular matrix (ECM) cues instruct neural stem/progenitor cell-niche interactions, and the objective of our study was to elucidate its composition and contribution to GSC maintenance in the perivascular niche.

METHODS

We interrogated human tumor tissue for immunofluorescence analysis and derived GSCs from tumor tissues for functional studies. Bioinformatics analyses were conducted by mining publicly available databases.

RESULTS

We find that laminin ECM proteins are localized to the perivascular GBM niche and inform negative patient prognosis. To identify the source of laminins, we characterized cellular elements within the niche and found that laminin α chains were expressed by nonstem tumor cells and tumor-associated endothelial cells (ECs). RNA interference targeting laminin α2 inhibited GSC growth and self-renewal. In co-culture studies of GSCs and ECs, laminin α2 knockdown in ECs resulted in decreased tumor growth.

INTERPRETATION

Our studies highlight the contribution of nonstem tumor cell-derived laminin juxtracrine signaling. As laminin α2 has recently been identified as a molecular marker of aggressive ependymoma, we propose that the brain vascular ECM promotes tumor malignancy through maintenance of the GSC compartment, providing not only a molecular fingerprint but also a possible therapeutic target.

A phase I/II trial of pazopanib in combination with lapatinib in adult patients with relapsed malignant glioma

PURPOSE

Increased mitogenic signaling and angiogenesis, frequently facilitated by somatic activation of EGF receptor (EGFR; ErbB1) and/or loss of PTEN, and VEGF overexpression, respectively, drive malignant glioma growth. We hypothesized that patients with recurrent glioblastoma would exhibit differential antitumor benefit based on tumor PTEN/EGFRvIII status when treated with the antiangiogenic agent pazopanib and the ErbB inhibitor lapatinib.

EXPERIMENTAL DESIGN

A phase II study evaluated the antitumor activity of pazopanib 400 mg/d plus lapatinib 1,000 mg/d in patients with grade 4 malignant glioma and known PTEN/EGFRvIII status not receiving enzyme-inducing anticonvulsants (EIAC). The phase II study used a two-stage Green-Dahlberg design for futility. An independent, parallel phase I component determined the maximum-tolerated regimen (MTR) of pazopanib and lapatinib in patients with grade 3/4 glioma receiving EIACs.

RESULTS

The six-month progression-free survival (PFS) rates in phase II (n = 41) were 0% and 15% in the PTEN/EGFRvIII-positive and PTEN/EGFRvIII-negative cohorts, respectively, leading to early termination. Two patients (5%) had a partial response and 14 patients (34%) had stable disease lasting 8 or more weeks. In phase I (n = 34), the MTR was not reached. On the basis of pharmacokinetic and safety review, a regimen of pazopanib 600 mg plus lapatinib 1,000 mg, each twice daily, was considered safe. Concomitant EIACs reduced exposure to pazopanib and lapatinib.

CONCLUSIONS

The antitumor activity of this combination at the phase II dose tested was limited. Pharmacokinetic data indicated that exposure to lapatinib was subtherapeutic in the phase II evaluation. Evaluation of intratumoral drug delivery and activity may be essential for hypothesis-testing trials with targeted agents in malignant glioma.

A PK2/Bv8/PROK2 antagonist suppresses tumorigenic processes by inhibiting angiogenesis in glioma and blocking myeloid cell infiltration in pancreatic cancer

Infiltration of myeloid cells in the tumor microenvironment is often associated with enhanced angiogenesis and tumor progression, resulting in poor prognosis in many types of cancer. The polypeptide chemokine PK2 (Bv8, PROK2) has been shown to regulate myeloid cell mobilization from the bone marrow, leading to activation of the angiogenic process, as well as accumulation of macrophages and neutrophils in the tumor site. Neutralizing antibodies against PK2 were shown to display potent anti-tumor efficacy, illustrating the potential of PK2-antagonists as therapeutic agents for the treatment of cancer. In this study we demonstrate the anti-tumor activity of a small molecule PK2 antagonist, PKRA7, in the context of glioblastoma and pancreatic cancer xenograft tumor models. For the highly vascularized glioblastoma, PKRA7 was associated with decreased blood vessel density and increased necrotic areas in the tumor mass. Consistent with the anti-angiogenic activity of PKRA7 in vivo, this compound effectively reduced PK2-induced microvascular endothelial cell branching in vitro. For the poorly vascularized pancreatic cancer, the primary anti-tumor effect of PKRA7 appears to be mediated by the blockage of myeloid cell migration/infiltration. At the molecular level, PKRA7 inhibits PK2-induced expression of certain pro-migratory chemokines and chemokine receptors in macrophages. Combining PKRA7 treatment with standard chemotherapeutic agents resulted in enhanced effects in xenograft models for both types of tumor. Taken together, our results indicate that the anti-tumor activity of PKRA7 can be mediated by two distinct mechanisms that are relevant to the pathological features of the specific type of cancer. This small molecule PK2 antagonist holds the promise to be further developed as an effective agent for combinational cancer therapy.

Disruption of wild-type IDH1 suppresses D-2-hydroxyglutarate production in IDH1-mutated gliomas

Point mutations at Arg132 of the cytoplasmic NADP(+)-dependent isocitrate dehydrogenase 1 (IDH1) occur frequently in gliomas and result in a gain of function to produce the "oncometabolite" D-2-hydroxyglutarate (D-2HG). The mutated IDH1 allele is usually associated with a wild-type IDH1 allele (heterozygous) in cancer. Here, we identify 2 gliomas that underwent loss of the wild-type IDH1 allele but retained the mutant IDH1 allele following tumor progression from World Health Organization (WHO) grade III anaplastic astrocytomas to WHO grade IV glioblastomas. Intratumoral D-2HG was 14-fold lower in the glioblastomas lacking wild-type IDH1 than in glioblastomas with heterozygous IDH1 mutations. To characterize the contribution of wild-type IDH1 to cancer cell D-2HG production, we established an IDH1-mutated astrocytoma (IMA) cell line from a WHO grade III anaplastic astrocytoma. Disruption of the wild-type IDH1 allele in IMA cells by gene targeting resulted in an 87-fold decrease in cellular D-2HG levels, showing that both wild-type and mutant IDH1 alleles are required for D-2HG production in glioma cells. Expression of wild-type IDH1 was also critical for mutant IDH1-associated D-2HG production in the colorectal cancer cell line HCT116. These insights may aid in the development of therapeutic strategies to target IDH1-mutated cancers.

Subgroup-specific structural variation across 1,000 medulloblastoma genomes

Medulloblastoma, the most common malignant paediatric brain tumour, is currently treated with nonspecific cytotoxic therapies including surgery, whole-brain radiation, and aggressive chemotherapy. As medulloblastoma exhibits marked intertumoural heterogeneity, with at least four distinct molecular variants, previous attempts to identify targets for therapy have been underpowered because of small samples sizes. Here we report somatic copy number aberrations (SCNAs) in 1,087 unique medulloblastomas. SCNAs are common in medulloblastoma, and are predominantly subgroup-enriched. The most common region of focal copy number gain is a tandem duplication of SNCAIP, a gene associated with Parkinson's disease, which is exquisitely restricted to Group 4α. Recurrent translocations of PVT1, including PVT1-MYC and PVT1-NDRG1, that arise through chromothripsis are restricted to Group 3. Numerous targetable SCNAs, including recurrent events targeting TGF-β signalling in Group 3, and NF-κB signalling in Group 4, suggest future avenues for rational, targeted therapy.

Pilot study of systemic and intrathecal mafosfamide followed by conformal radiation for infants with intracranial central nervous system tumors: a pediatric brain tumor consortium study (PBTC-001)

A pilot study to investigate the feasibility of the addition of intrathecal (IT) mafosfamide to a regimen of concomitant multi-agent systemic chemotherapy followed by conformal radiation therapy (RT) for children <3 years with newly diagnosed embryonal CNS tumors was performed. Ninety-three newly diagnosed infants and children (<3 years) with embryonal CNS tumors were enrolled. Twenty weeks of systemic multi-agent chemotherapy commenced within 35 days of surgery. Patients without CSF flow obstruction (n = 71) received IT mafosfamide (14 mg) with chemotherapy. Localized (M(0)) patients with SD or better subsequently received RT followed by 20 additional weeks of chemotherapy. Second look surgery was encouraged prior to RT if there was an incomplete surgical resection at diagnosis. 71 evaluable patients with normal CSF flow received IT Mafosfamide with systemic chemotherapy; patients with M + disease were removed from protocol therapy at 20 weeks and those with PD at the time of progression. One and 5-year progression free survival (PFS) and overall survival (OS) for the cohort of 71 evaluable patients were 52 ± 6.5 % and 33 ± 13 %, and 67 ± 6.2 % and 51 ± 11 %, respectively. The 1-year Progression Free Survival (PFS) for M0 patients with medulloblastoma (MB, n = 20), supratentorial primitive neuroectodermal tumor (PNET, n = 9), and atypical teratoid rhabdoid tumor (ATRT, n = 12) was 80 ± 7 %, 67 ± 15 % and 27 ± 13 % and 5-year PFS was 65 ± 19 %, 37 ± 29 %, and 0 ± 0 %, respectively. The addition of IT mafosfamide to systemic chemotherapy in infants with embryonal CNS tumors was feasible. The PFS for M0 patients appears comparable to or better than most prior historical comparisons and was excellent for those receiving conformal radiotherapy.

Central nervous system

Several different types of tumors, benign and malignant, have been identified in the central nervous system (CNS). The prognoses for these tumors are related to several factors, such as the age of the patient and the location and histology of the tumor. In adults, about half of all CNS tumors are malignant, whereas in pediatric patients, more than 75% are malignant. For most benign CNS tumors that require treatment, neurosurgeons can offer curative resections or at least provide significant relief from mass effect. Unfortunately, we still lack effective treatments for most primary and secondary malignant CNS tumors. However, the past decade has witnessed an explosion in the understanding of the early molecular events in malignant primary CNS tumors, and for the first time in history, oncologists are seeing that a plethora of new therapies targeting these molecular events are being tested in clinical trials. There is hope on the horizon for the fight against these deadly tumors. The distribution of CNS tumors by location has remained constant for numerous years. The majority of primary CNS tumors arise in the major cortical lobes. Twenty nine percent of primary CNS tumors arise from the dural meninges that encase the CNS structures. The vast majority of these are meningiomas, of which over 90% are benign. About 10% of primary CNS tumors are found in the sella turcica region, where the pituitary gland resides. Other much less common sites of primary CNS tumors include the pineal region, ventricular system, cerebellum, brain stem, cranial nerves, and spinal cord. The distribution of CNS tumors by histology has seen a slight increase in more malignant tumors over the past decade, possibly due to increased neuroimaging practices or environmental exposures. Arising from glial cells, gliomas represent over 36% of all primary CNS tumors and consist of astrocytomas, oligodendrogliomas, ependymomas, mixed gliomas, and neuroepithelial tumors. The benign meningiomas make up 32% of primary CNS tumors, followed by nerve sheath tumors and pituitary tumors. Primary CNS lymphomas, embryonal tumors, and craniopharyngiomas are uncommon. The most common gliomas are astrocytomas, and these tumors are typically classified by the World Health Organization (WHO) as Grades I through IV. Grade IV, the most malignant grade of astrocytoma, includes glioblastoma multiforme (GBM), the most common malignant primary CNS glioma in adults, which represents 51% of all CNS gliomas. GBM is unfortunately the most challenging to effectively treat and has the worst patient survival. This chapter is therefore primarily devoted to the current understanding of this topic. Here we describe the molecular and cellular events associated with malignant glioma initiation and progression. We also review the importance of glioma stem cell biology and tumor immunology in early gliomagenesis. In addition, we present a brief description of the most common malignant primary CNS glioma in pediatric patients - medulloblastoma, as well as familial cancer syndromes that include gliomas as part of the syndrome.

Phase 1 trial of dasatinib plus erlotinib in adults with recurrent malignant glioma

To determine the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT) of dasatinib, an inhibitor of the Src family kinase proteins, with erlotinib, an epidermal growth factor receptor tyrosine kinase inhibitor, among recurrent malignant glioma patients. Once daily dasatinib was escalated in successive cohorts while erlotinib was administered daily at established doses based on concurrent CYP3A-inducing anticonvulsant (EIAEDS) use. Dasatinib pharmacokinetic analyzes were performed. Forty-seven patients enrolled including 37 (79 %) with grade IV and 10 (21 %) with grade III malignant glioma. Thirty patients (64 %) were at ≥second recurrence, while 27 (57 %) had received prior bevacizumab. The dasatinib MTD was 180 mg when combined with either 150 mg of erlotinib for patients not on EIAEDs, or 450 mg of erlotinib for patients on EIAEDs. The most common DLTs were diarrhea and fatigue, while most adverse events were grade 2. Pharmacokinetic data suggests that dasatinib exposure increased with increased dasatinib dose and concurrent erlotinib administration, while concurrent EIAED use diminished dasatinib exposure. No radiographic responses were observed, and only one patient (2 %) remained progression-free at 6 months. We demonstrate that dasatinib plus erlotinib can be safely co-administered on a continuous, daily dosing schedule with erlotinib, and established the recommended dose level of this combination.

Frequent ATRX, CIC, FUBP1 and IDH1 mutations refine the classification of malignant gliomas

Mutations in the critical chromatin modifier ATRX and mutations in CIC and FUBP1, which are potent regulators of cell growth, have been discovered in specific subtypes of gliomas, the most common type of primary malignant brain tumors. However, the frequency of these mutations in many subtypes of gliomas, and their association with clinical features of the patients, is poorly understood. Here we analyzed these loci in 363 brain tumors. ATRX is frequently mutated in grade II-III astrocytomas (71%), oligoastrocytomas (68%), and secondary glioblastomas (57%), and ATRX mutations are associated with IDH1 mutations and with an alternative lengthening of telomeres phenotype. CIC and FUBP1 mutations occurred frequently in oligodendrogliomas (46% and 24%, respectively) but rarely in astrocytomas or oligoastrocytomas ( more than 10%). This analysis allowed us to define two highly recurrent genetic signatures in gliomas: IDH1/ATRX (I-A) and IDH1/CIC/FUBP1 (I-CF). Patients with I-CF gliomas had a significantly longer median overall survival (96 months) than patients with I-A gliomas (51 months) and patients with gliomas that did not harbor either signature (13 months). The genetic signatures distinguished clinically distinct groups of oligoastrocytoma patients, which usually present a diagnostic challenge, and were associated with differences in clinical outcome even among individual tumor types. In addition to providing new clues about the genetic alterations underlying gliomas, the results have immediate clinical implications, providing a tripartite genetic signature that can serve as a useful adjunct to conventional glioma classification that may aid in prognosis, treatment selection, and therapeutic trial design.

MET and ALK in glioblastoma multiforme (GBM): Comparison of IHC and FISH

2021

Background: GBM, the most common and lethal malignant primary brain tumor in adults, has an overall one-year life expectancy of 33.7%. Personalized medicine on the basis of predictive biomarkers remains elusive in GBM; however a recent case report showed clinical improvement after treatment with a mesenchymal-epithelial transition (MET) inhibitor. The authors of that report ascribe clinical response to the MET inhibitor, but the drug is also an inhibitor of anaplastic lymphoma kinase (ALK). We explored the co-expression, gain, or amplification of both MET and ALK by IHC and FISH in GBM. Methods: A convenience sample of 56 available tumors from gross-resected GBM cases within the Duke Brain Tumor tissue bank was stained for MET using clone 8F11 (Leica) and for ALK using clone 5A4 (Novocastra). FISH employed the LSI ALK (2p23) breakpoint-spanning dual-color DNA probe and the LSI D7S486 (MET)/CEP 7 dual color DNA probe (Vysis). Results: Of 56 GBM cases, MET was expressed in 69.6% and ALK in 17.9% by IHC. By FISH, gain or amplification was found in 100% of cases for MET and in 48.2% for ALK. Co-expression of MET and ALK by IHC was 14.3% and 48.2% by FISH. Co-expression by either IHC or FISH was also 48.2%. OS estimation for this cohort is premature, with 77% of patients still alive. Conclusions: MET and ALK are (co-)expressed in a significant proportion of GBM. IHC detection of MET and ALK did not correlate well with FISH results, suggesting that gene gain or amplification does not necessarily lead to abnormal MET and ALK protein expression or that IHC methods or antibodies used can be optimized. Prior studies reported MET amplification in GBM as low as 4%. Our study indicates that MET gain/amplification and protein expression may be much higher, having implications for MET-targeted therapy. Additionally, co-expression of ALK and MET has implications for dual inhibitors of these signaling pathways as well as resistance mechanisms. Our continued work will explore significance of MET and ALK as predictors of therapeutic response, with careful control for clinically relevant patient and disease characteristics. [Table: see text]

Bevacizumab therapy for adults with recurrent/progressive meningioma: a retrospective series

Intracranial meningiomas are often indolent tumors which typically grow over years to decades. Nonetheless, meningiomas that progress after maximum safe resection and radiation therapy pose a significant therapeutic challenge and effective therapies have yet to be identified. Preclinical studies implicate angiogenesis in the pathophysiology of more aggressive meningiomas, suggesting that anti-angiogenic therapies may be of utility in this setting. We performed a retrospective review of fourteen patients with recurrent meningioma treated at Duke University Medical Center with bevacizumab, a humanized monoclonal antibody against vascular endothelial growth factor, administered either alone or in combination with chemotherapy. Most patients were heavily pre-treated. Progression-free survival at 6 months was 86 % and was comparable regardless of meningioma grade and whether bevacizumab was administered as monotherapy or in combination with chemotherapy. Most toxicities were mild however single patients developed CNS hemorrhage (grade 1) and intestinal perforation (grade 4), respectively. Bevacizumab can be administered safely to patients with meningioma and appears to be associated with encouraging anti-tumor effect when administered as either a single agent or in combination with chemotherapy. Phase II trials investigating bevacizumab in patients with progressive/recurrent meningioma are warranted.

A pilot study of IL-2Rα blockade during lymphopenia depletes regulatory T-cells and correlates with enhanced immunity in patients with glioblastoma

BACKGROUND

Preclinical studies in mice have demonstrated that the prophylactic depletion of immunosuppressive regulatory T-cells (T(Regs)) through targeting the high affinity interleukin-2 (IL-2) receptor (IL-2Rα/CD25) can enhance anti-tumor immunotherapy. However, therapeutic approaches are complicated by the inadvertent inhibition of IL-2Rα expressing anti-tumor effector T-cells.

OBJECTIVE

To determine if changes in the cytokine milieu during lymphopenia may engender differential signaling requirements that would enable unarmed anti-IL-2Rα monoclonal antibody (MAbs) to selectively deplete T(Regs) while permitting vaccine-stimulated immune responses.

METHODOLOGY

A randomized placebo-controlled pilot study was undertaken to examine the ability of the anti-IL-2Rα MAb daclizumab, given at the time of epidermal growth factor receptor variant III (EGFRvIII) targeted peptide vaccination, to safely and selectively deplete T(Regs) in patients with glioblastoma (GBM) treated with lymphodepleting temozolomide (TMZ).

RESULTS AND CONCLUSIONS

Daclizumab treatment (n = 3) was well-tolerated with no symptoms of autoimmune toxicity and resulted in a significant reduction in the frequency of circulating CD4+Foxp3+ TRegs in comparison to saline controls (n = 3)( p = 0.0464). A significant (p<0.0001) inverse correlation between the frequency of TRegs and the level of EGFRvIII specific humoral responses suggests the depletion of TRegs may be linked to increased vaccine-stimulated humoral immunity. These data suggest this approach deserves further study.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00626015.

An animal model of MYC-driven medulloblastoma

Medulloblastoma (MB) is the most common malignant brain tumor in children. Patients whose tumors exhibit overexpression or amplification of the MYC oncogene (c-MYC) usually have an extremely poor prognosis, but there are no animal models of this subtype of the disease. Here, we show that cerebellar stem cells expressing Myc and mutant Trp53 (p53) generate aggressive tumors following orthotopic transplantation. These tumors consist of large, pleiomorphic cells and resemble human MYC-driven MB at a molecular level. Notably, antagonists of PI3K/mTOR signaling, but not Hedgehog signaling, inhibit growth of tumor cells. These findings suggest that cerebellar stem cells can give rise to MYC-driven MB and identify a novel model that can be used to test therapies for this devastating disease.

Descriptive epidemiology of malignant and nonmalignant primary spinal cord, spinal meninges, and cauda equina tumors, United States, 2004-2007

BACKGROUND

Primary tumors of the spinal cord, spinal meninges, and cauda equina are relatively rare, and a paucity of population-based data exist on tumors in these sites. This study intends to augment the current literature by examining incidence of these tumors on a national level.

METHODS

Data from central cancer registries in the National Program of Cancer Registries (NPCR) and Surveillance, Epidemiology, and End Results (SEER) programs for 2004-2007 (covering 99.2% of US population) and 1999-2007 (covering 89.4% of US population) were analyzed. Analyses for diagnosis years 2004-2007 included cases of malignant and nonmalignant primary spinal cord, spinal meninges, and cauda equina tumors. Descriptive statistics including estimated age-adjusted incidence rates standardized to the 2000 US standard population were conducted for both malignant and nonmalignant primary spinal tumors from cases diagnosed during 2004-2007 as well as trend analyses on malignant cases of primary spinal tumors (n = 5103) for cases diagnosed during 1999-2007 using SEER Stat 6.6.2 software.

RESULTS

There were 2576 cases of malignant primary spinal tumors and 9136 cases of nonmalignant primary spinal tumors in 2004-2007. The incidence of malignant and nonmalignant primary spinal tumors combined differed by age, sex, race, and ethnicity. Results of trend analyses indicated that malignant primary spinal tumors have been stable throughout the 1999-2007 period.

CONCLUSIONS

This large population-based study adds new insights into the descriptive epidemiology of primary spinal cord, spinal meninges, and cauda equina tumors by providing in-depth analyses of the incidence of these tumors on a national level.

Phase II study of carboplatin, irinotecan, and bevacizumab for bevacizumab naïve, recurrent glioblastoma

We evaluated the efficacy of carboplatin, irinotecan, and bevacizumab among bevacizumab-naïve, recurrent glioblastoma (GBM) patients in a phase 2, open-label, single arm trial. Forty eligible patients received carboplatin (area under the plasma curve [AUC] 4 mg/ml-min) on day one, while bevacizumab (10 mg/kg) and irinotecan (340 mg/m(2) for patients on CYP3A-enzyme-inducing anti-epileptics [EIAEDs] and 125 mg/m(2) for patients not on EIAEDs) were administered on days 1 and 14 of every 28-day cycle. Patients were evaluated after each of the first two cycles and then after every other cycle. Treatment continued until progressive disease, unacceptable toxicity, non-compliance, or voluntary withdrawal. The primary endpoint was progression-free survival at 6 months (PFS-6) and secondary endpoints included safety and median overall survival (OS). All patients had progression after standard therapy. The median age was 51 years. Sixteen patients (40%) had a KPS of 90-100, while 27 (68%) were at first progression. The median time from original diagnosis was 11.4 months. The PFS-6 rate was 46.5% (95% CI: 30.4, 61.0%) and the median OS was 8.3 months [95% confidence interval (CI): 5.9, and 10.7 months]. Grade 4 events were primarily hematologic and included neutropenia and thrombocytopenia in 20 and 10%, respectively. The most common grade 3 events were neutropenia, thrombocytopenia, fatigue, and infection in 25, 20, 13, and 10%, respectively. Eleven patients (28%) discontinued study therapy due to toxicity and 17 patients (43%) required dose modification. One patient died due to treatment-related intestinal perforation. The addition of carboplatin and irinotecan to bevacizumab significantly increases toxicity but does not improve anti-tumor activity to that achieved historically with single-agent bevacizumab among bevacizumab-naïve, recurrent GBM patients. (ClinicalTrials.gov number NCT00953121).

A phase II study of O6-benzylguanine and temozolomide in pediatric patients with recurrent or progressive high-grade gliomas and brainstem gliomas: a Pediatric Brain Tumor Consortium study

To estimate the sustained (≥8 weeks) objective response rate in pediatric patients with recurrent or progressive high-grade gliomas (HGG, Stratum A) or brainstem gliomas (BSG, Stratum B) treated with the combination of O6-benzylguanine (O6BG) and temozolomide(®) (TMZ). Patients received O6BG 120 mg/m(2)/d IV followed by TMZ 75 mg/m(2)/d orally daily for 5 consecutive days of each 28-day course. The target objective response rate to consider the combination active was 17%. A two-stage design was employed. Forty-three patients were enrolled; 41 were evaluable for response, including 25 patients with HGG and 16 patients with BSG. The combination of O6BG and TMZ was tolerable, and the primary toxicities were myelosuppression and gastrointestinal symptoms. One sustained (≥8 weeks) partial response was observed in the HGG cohort; no sustained objective responses were observed in the BSG cohort. Long-term (≥6 courses) stable disease (SD) was observed in 4 patients in Stratum A and 1 patient in Stratum B. Of the 5 patients with objective response or long-term SD, 3 underwent central review with 2 reclassified as low-grade gliomas. The combination of O6BG and TMZ did not achieve the target response rate for activity in pediatric patients with recurrent or progressive HGG and BSG.

Radioimmunotargeting of malignant glioma by monoclonal antibody D2C7 reactive against both wild-type and variant III mutant epidermal growth factor receptors

INTRODUCTION

Malignant glioma remains a significant therapeutic challenge, and immunotherapeutics might be a beneficial approach for these patients. A monoclonal antibody (MAb) specific for multiple molecular targets could expand the treatable patient population and the fraction of tumor cells targeted, with potentially increased efficacy. This motivated the generation of MAb D2C7, which recognizes both wild-type epidermal growth factor receptor (EGFRwt) and a tumor-specific mutant, EGFRvIII.

METHODS

D2C7 binding affinity was determined by surface plasmon resonance and its specificity characterized through comparison to EGFRwt-specific EGFR.1 and EGFRvIII-specific L8A4 MAbs by flow cytometry and immunohistochemical analysis. The three MAbs were labeled with (125)I or (131)I using Iodogen, and paired-label internalization assays and biodistribution experiments in athymic mice with human tumor xenografts were performed.

RESULTS

The affinity of D2C7 for EGFRwt and EGFRvIII was 5.2×10(9) M(-1) and 3.6×10(9) M(-1), and cell-surface reactivity with both receptors was documented by flow cytometry. Immunohistochemical analyses revealed D2C7 reactivity with malignant glioma tissue from 90 of 101 patients. Internalization assays performed on EGFRwt-expressing WTT cells and EGFRvIII-expressing NR6M cells indicated a threefold lower degradation of (125)I-labeled D2C7 compared with (131)I-labeled EGFR.1. Uptake of (125)I-labeled D2C7 in NR6M xenografts (52.45±13.97 %ID g(-1) on Day 3) was more than twice that of (131)I-labeled L8A4; a threefold to fivefold tumor delivery advantage was seen when compared to (131)I-labeled EGFR.1 in mice with WTT xenografts.

CONCLUSIONS

These results suggest that D2C7 warrants further evaluation for the development of MAb-based therapeutics against cancers expressing EGFRwt and EGFRvIII.

Phase II study of Gleevec® plus hydroxyurea (HU) in adults with progressive or recurrent meningioma

We prospectively evaluated the efficacy and safety of imatinib plus hydroxyurea in patients with progressive/recurrent meningioma. A total of 21 patients with progressive/recurrent meningioma were enrolled in this dual center, single-arm, phase II trial. All patients received 500 mg of hydroxyurea twice a day. Imatinib was administered at 400 mg/day for patients not on CYP3A enzyme inducing anti-epileptic drugs (EIAEDs) and at 500 mg twice a day for patients on EIAEDs. The primary endpoint was progression-free survival at 6 months (PFS-6) and secondary endpoints were safety, radiographic response rate, and overall survival (OS). Best radiographic response was stable disease and was observed in 14 patients (67%). PFS-6 for all patients, those with grade I tumors (n = 8) and those with grade II or III tumors (n = 13) was 61.9, 87.5 and 46.2%, respectively. Patients with grade II or III tumors had poorer PFS and OS than those with grade I tumors, (P = 0.025 and P = 0.018) respectively. The only grade 3 or greater adverse event occurring in ≥ 10% of patients was anemia (10%). Imatinib plus hydroxyurea is well tolerated among patients with meningioma but has modest anti-tumor activity for this indication.

Direct in vivo evidence for tumor propagation by glioblastoma cancer stem cells

High-grade gliomas (World Health Organization grade III anaplastic astrocytoma and grade IV glioblastoma multiforme), the most prevalent primary malignant brain tumors, display a cellular hierarchy with self-renewing, tumorigenic cancer stem cells (CSCs) at the apex. While the CSC hypothesis has been an attractive model to describe many aspects of tumor behavior, it remains controversial due to unresolved issues including the use of ex vivo analyses with differential growth conditions. A CSC population has been confirmed in malignant gliomas by preferential tumor formation from cells directly isolated from patient biopsy specimens. However, direct comparison of multiple tumor cell populations with analysis of the resulting phenotypes of each population within a representative tumor environment has not been clearly described. To directly test the relative tumorigenic potential of CSCs and non-stem tumor cells in the same microenvironment, we interrogated matched tumor populations purified from a primary human tumor transplanted into a xenograft mouse model and monitored competitive in vivo tumor growth studies using serial in vivo intravital microscopy. While CSCs were a small minority of the initial transplanted cancer cell population, the CSCs, not the non-stem tumor cells, drove tumor formation and yielded tumors displaying a cellular hierarchy. In the resulting tumors, a fraction of the initial transplanted CSCs maintained expression of stem cell and proliferation markers, which were significantly higher compared to the non-stem tumor cell population and demonstrated that CSCs generated cellular heterogeneity within the tumor. These head-to-head comparisons between matched CSCs and non-stem tumor cells provide the first functional evidence using live imaging that in the same microenvironment, CSCs more than non-stem tumor cells are responsible for tumor propagation, confirming the functional definition of a CSC.

A review of VEGF/VEGFR-targeted therapeutics for recurrent glioblastoma

Glioblastoma, the most common primary malignant brain tumor among adults, is a highly angiogenic and deadly tumor. Angiogenesis in glioblastoma, driven by hypoxia-dependent and independent mechanisms, is primarily mediated by vascular endothelial growth factor (VEGF), and generates blood vessels with distinctive features. The outcome for patients with recurrent glioblastoma is poor because of ineffective therapies. However, recent encouraging rates of radiographic response and progression-free survival, and adequate safety, led the FDA to grant accelerated approval of bevacizumab, a humanized monoclonal antibody against VEGF, for the treatment of recurrent glioblastoma in May 2009. These results have triggered significant interest in additional antiangiogenic agents and therapeutic strategies for patients with both recurrent and newly diagnosed glioblastoma. Given the potent antipermeability effect of VEGF inhibitors, the Radiologic Assessment in Neuro-Oncology (RANO) criteria were recently implemented to better assess response among patients with glioblastoma. Although bevacizumab improves survival and quality of life, eventual tumor progression is the norm. Better understanding of resistance mechanisms to VEGF inhibitors and identification of effective therapy after bevacizumab progression are currently a critical need for patients with glioblastoma.

Glioma stem cell proliferation and tumor growth are promoted by nitric oxide synthase-2

Malignant gliomas are aggressive brain tumors with limited therapeutic options, and improvements in treatment require a deeper molecular understanding of this disease. As in other cancers, recent studies have identified highly tumorigenic subpopulations within malignant gliomas, known generally as cancer stem cells. Here, we demonstrate that glioma stem cells (GSCs) produce nitric oxide via elevated nitric oxide synthase-2 (NOS2) expression. GSCs depend on NOS2 activity for growth and tumorigenicity, distinguishing them from non-GSCs and normal neural progenitors. Gene expression profiling identified many NOS2-regulated genes, including the cell-cycle inhibitor cell division autoantigen-1 (CDA1). Further, high NOS2 expression correlates with decreased survival in human glioma patients, and NOS2 inhibition slows glioma growth in a murine intracranial model. These data provide insight into how GSCs are mechanistically distinct from their less tumorigenic counterparts and suggest that NOS2 inhibition may be an efficacious approach to treating this devastating disease.

Embryonal central nervous system neoplasms arising in infants and young children: a pediatric brain tumor consortium study

CONTEXT

Medulloblastomas (MBs) and atypical teratoid/rhabdoid tumors (AT/RTs) arising in infants and children can be difficult to distinguish; however, histologic characterization is prognostically important.

OBJECTIVE

To determine histologic and phenotypic markers associated with utility with progression-free survival (PFS) and overall survival (OS) in children younger than 3 years with MBs and AT/RTs.

DESIGN

We undertook a histologic and immunophenotypic study of MBs and AT/RTs arising in infants and children younger than 3 years treated in a Pediatric Brain Tumor Consortium study. The 41 girls and 55 boys ranged in age from 2 to 36 months at enrollment. These infants and children exhibited 51 MBs, 26 AT/RTs, and 24 other tumors (not further studied). Median follow-up of the patients was 17.2 months from diagnosis (range: 1.4-93 months).

RESULTS

Infants and children with AT/RT exhibited a statistically significant shorter PFS and OS when compared to infants and children with MBs (both P < .001). A lack of nuclear BAF47 immunohistochemical reactivity proved reliable in identifying AT/RTs. Among MBs, our data suggest an association of nodularity and prolonged PFS and OS, which must be independently confirmed. Anaplasia correlated with OTX2 reactivity and both OTX2 and moderate to severe anaplasia correlated with PFS but not with OS.

CONCLUSION

Distinguishing AT/RT from MBs is clinically important. For expert neuropathologists, the diagnoses of AT/RT and MB can be reliably made from hematoxylin-eosin stains in the vast majority of cases. However certain rare small cell variants of AT/RT can be confused with MB. We also found that immunohistochemical reactivity for BAF47 is clinically useful in distinguishing MBs from AT/RTs and for identifying certain small cell AT/RTs. Among MBs, nodularity may be an important prognostic factor for improved PFS and OS in infants and children.

Phase 2 study of carboplatin, irinotecan, and bevacizumab for recurrent glioblastoma after progression on bevacizumab therapy

BACKGROUND

The efficacy of carboplatin, irinotecan, and bevacizumab among recurrent glioblastoma (GBM) patients after prior progression on bevacizumab therapy in a phase 2, open-label, single-arm trial was evaluated.

METHODS

Eligible patients received carboplatin (area under the plasma curve [AUC] 4 mg/ml-min) on day 1, whereas bevacizumab (10 mg/kg) and irinotecan (340 mg/m(2) for patients on CYP3A enzyme-inducing anti-epileptics [EIAEDs] and 125 mg/m(2) for patients not on EIAEDs) were administered on days 1 and 14 of every 28-day cycle. Patients were evaluated after each of the first 2 cycles and then after every other cycle. Treatment continued until progressive disease, unacceptable toxicity, noncompliance, or voluntary withdrawal. The primary end point was progression-free survival at 6 months (PFS-6), and secondary end points included safety and median overall survival (OS).

RESULTS

All patients had progression on at least 1 prior bevacizumab regimen and 56% enrolled after either second or third overall progression. The median OS was 5.8 months (95% confidence interval [CI], 4.0-7.0 months) and PFS-6 rate was 16% (95% CI, 5.0%-32.5%). The most common grade 3 or 4 events were hematologic and occurred in 29% of cycles. Nine patients (38%) required dose modification. There were no treatment-related deaths.

CONCLUSIONS

Carboplatin, irinotecan, and bevacizumab was associated with modest activity and adequate safety among recurrent GBM patients who progressed on bevacizumab previously.