Nonreceptor tyrosine kinase BMX maintains self-renewal and tumorigenic potential of glioblastoma stem cells by activating STAT3

Glioblastomas display cellular hierarchies containing tumor-propagating glioblastoma stem cells (GSCs). STAT3 is a critical signaling node in GSC maintenance but molecular mechanisms underlying STAT3 activation in GSCs are poorly defined. Here we demonstrate that the bone marrow X-linked (BMX) nonreceptor tyrosine kinase activates STAT3 signaling to maintain self-renewal and tumorigenic potential of GSCs. BMX is differentially expressed in GSCs relative to nonstem cancer cells and neural progenitors. BMX knockdown potently inhibited STAT3 activation, expression of GSC transcription factors, and growth of GSC-derived intracranial tumors. Constitutively active STAT3 rescued the effects of BMX downregulation, supporting that BMX signals through STAT3 in GSCs. These data demonstrate that BMX represents a GSC therapeutic target and reinforces the importance of STAT3 signaling in stem-like cancer phenotypes.

Greater chemotherapy-induced lymphopenia enhances tumor-specific immune responses that eliminate EGFRvIII-expressing tumor cells in patients with glioblastoma

Epidermal growth factor receptor variant III (EGFRvIII) is a tumor-specific mutation widely expressed in glioblastoma multiforme (GBM) and other neoplasms, but absent from normal tissues. Immunotherapeutic targeting of EGFRvIII could eliminate neoplastic cells more precisely but may be inhibited by concurrent myelosuppressive chemotherapy like temozolomide (TMZ), which produces a survival benefit in GBM. A phase II, multicenter trial was undertaken to assess the immunogenicity of an experimental EGFRvIII-targeted peptide vaccine in patients with GBM undergoing treatment with serial cycles of standard-dose (STD) (200 mg/m(2) per 5 days) or dose-intensified (DI) TMZ (100 mg/m(2) per 21 days). All patients receiving STD TMZ exhibited at least a transient grade 2 lymphopenia, whereas those receiving DI TMZ exhibited a sustained grade 3 lymphopenia (<500 cells/μL). CD3(+) T-cell (P = .005) and B-cell (P = .004) counts were reduced significantly only in the DI cohort. Patients in the DI cohort had an increase in the proportion of immunosuppressive regulatory T cells (T(Reg); P = .008). EGFRvIII-specific immune responses developed in all patients treated with either regimen, but the DI TMZ regimen produced humoral (P = .037) and delayed-type hypersensitivity responses (P = .036) of greater magnitude. EGFRvIII-expressing tumor cells were also eradicated in nearly all patients (91.6%; CI(95): 64.0%-99.8%; P < .0001). The median progression-free survival (15.2 months; CI(95): 11.0-18.5 months; hazard ratio [HR] = 0.35; P = .024) and overall survival (23.6 months; CI(95): 18.5-33.1 months; HR = 0.23; P = .019) exceeded those of historical controls matched for entry criteria and adjusted for known prognostic factors. EGFRvIII-targeted vaccination induces patient immune responses despite therapeutic TMZ-induced lymphopenia and eliminates EGFRvIII-expressing tumor cells without autoimmunity.

Multiple phenotypic changes in mice after knockout of the B3gnt5 gene, encoding Lc3 synthase--a key enzyme in lacto-neolacto ganglioside synthesis

BACKGROUND

Ganglioside biosynthesis occurs through a multi-enzymatic pathway which at the lactosylceramide step is branched into several biosynthetic series. Lc3 synthase utilizes a variety of galactose-terminated glycolipids as acceptors by establishing a glycosidic bond in the beta-1,3-linkage to GlcNaAc to extend the lacto- and neolacto-series gangliosides. In order to examine the lacto-series ganglioside functions in mice, we used gene knockout technology to generate Lc3 synthase gene B3gnt5-deficient mice by two different strategies and compared the phenotypes of the two null mouse groups with each other and with their wild-type counterparts.

RESULTS

B3gnt5 gene knockout mutant mice appeared normal in the embryonic stage and, if they survived delivery, remained normal during early life. However, about 9% developed early-stage growth retardation, 11% died postnatally in less than 2 months, and adults tended to die in 5-15 months, demonstrating splenomegaly and notably enlarged lymph nodes. Without lacto-neolacto series gangliosides, both homozygous and heterozygous mice gradually displayed fur loss or obesity, and breeding mice demonstrated reproductive defects. Furthermore, B3gnt5 gene knockout disrupted the functional integrity of B cells, as manifested by a decrease in B-cell numbers in the spleen, germinal center disappearance, and less efficiency to proliferate in hybridoma fusion.

CONCLUSIONS

These novel results demonstrate unequivocally that lacto-neolacto series gangliosides are essential to multiple physiological functions, especially the control of reproductive output, and spleen B-cell abnormality. We also report the generation of anti-IgG response against the lacto-series gangliosides 3'-isoLM1 and 3',6'-isoLD1.

Glioblastoma Stem Cells: A Neuropathologist's View

Glioblastoma (WHO Grade IV) is both the most common primary brain tumor and the most malignant. Advances in the understanding of the biology of the tumor are needed in order to obtain a clearer picture of the mechanisms driving these tumors. To neuropathologists, glioblastoma is a tumor that represents a complex system of migrating pleomorphic tumor cells, proliferating blood vessels, infiltrating inflammatory cells, and necrosis. This review will highlight how the glioma stem cell concept brings these elements together into a collective whole, interacting with microenvironmental influences in complex ways. Borrowing from chaos theory a vocabulary of "self organizing systems" and "complex adaptive systems" that seem useful in describing these pathologic features, a new paradigm of glioblastoma biology will be proposed that genetic changes should be understood in a three dimensional framework as they relate not only to the tumor cells themselves but also to the multicellular hierarchical unit, not isolated from, but responsive to, its local milieu. In this way we will come to better appreciate the impact our therapeutic interventions have on the regional phenotypic heterogeneity that exists within the tumor and the intercellular communications directing adaptation and progression.

Immunologic escape after prolonged progression-free survival with epidermal growth factor receptor variant III peptide vaccination in patients with newly diagnosed glioblastoma

PURPOSE

Immunologic targeting of tumor-specific gene mutations may allow precise eradication of neoplastic cells without toxicity. Epidermal growth factor receptor variant III (EGFRvIII) is a constitutively activated and immunogenic mutation not expressed in normal tissues but widely expressed in glioblastoma multiforme (GBM) and other neoplasms.

PATIENTS AND METHODS

A phase II, multicenter trial was undertaken to assess the immunogenicity of an EGFRvIII-targeted peptide vaccine and to estimate the progression-free survival (PFS) and overall survival (OS) of vaccinated patients with newly diagnosed EGFRvIII-expressing GBM with minimal residual disease. Intradermal vaccinations were given until toxicity or tumor progression was observed. Sample size was calculated to differentiate between PFS rates of 20% and 40% 6 months after vaccination.

RESULTS

There were no symptomatic autoimmune reactions. The 6-month PFS rate after vaccination was 67% (95% CI, 40% to 83%) and after diagnosis was 94% (95% CI, 67% to 99%; n = 18). The median OS was 26.0 months (95% CI, 21.0 to 47.7 months). After adjustment for age and Karnofsky performance status, the OS of vaccinated patients was greater than that observed in a control group matched for eligibility criteria, prognostic factors, and temozolomide treatment (hazard ratio, 5.3; P = .0013; n = 17). The development of specific antibody (P = .025) or delayed-type hypersensitivity (P = .03) responses to EGFRvIII had a significant effect on OS. At recurrence, 82% (95% CI, 48% to 97%) of patients had lost EGFRvIII expression (P < .001).

CONCLUSION

EGFRvIII-targeted vaccination in patients with GBM warrants investigation in a phase III, randomized trial.

Integrin alpha 6 regulates glioblastoma stem cells

Cancer stem cells (CSCs) are a subpopulation of tumor cells suggested to be critical for tumor maintenance, metastasis, and therapeutic resistance. Prospective identification and targeting of CSCs are therefore priorities for the development of novel therapeutic paradigms. Although CSC enrichment has been achieved with cell surface proteins including CD133 (Prominin-1), the roles of current CSC markers in tumor maintenance remain unclear. We examined the glioblastoma stem cell (GSC) perivascular microenvironment in patient specimens to identify enrichment markers with a functional significance and identified integrin alpha6 as a candidate. Integrin alpha6 is coexpressed with conventional GSC markers and enriches for GSCs. Targeting integrin alpha6 in GSCs inhibits self-renewal, proliferation, and tumor formation capacity. Our results provide evidence that GSCs express high levels of integrin alpha6, which can serve not only as an enrichment marker but also as a promising antiglioblastoma therapy.

MRP3: a molecular target for human glioblastoma multiforme immunotherapy

Background

Glioblastoma multiforme (GBM) is refractory to conventional therapies. To overcome the problem of heterogeneity, more brain tumor markers are required for prognosis and targeted therapy. We have identified and validated a promising molecular therapeutic target that is expressed by GBM: human multidrug-resistance protein 3 (MRP3).

Methods

We investigated MRP3 by genetic and immunohistochemical (IHC) analysis of human gliomas to determine the incidence, distribution, and localization of MRP3 antigens in GBM and their potential correlation with survival. To determine MRP3 mRNA transcript and protein expression levels, we performed quantitative RT-PCR, raising MRP3-specific antibodies, and IHC analysis with biopsies of newly diagnosed GBM patients. We used univariate and multivariate analyses to assess the correlation of RNA expression and IHC of MRP3 with patient survival, with and without adjustment for age, extent of resection, and KPS.

Results

Real-time PCR results from 67 GBM biopsies indicated that 59/67 (88%) samples highly expressed MRP3 mRNA transcripts, in contrast with minimal expression in normal brain samples. Rabbit polyvalent and murine monoclonal antibodies generated against an extracellular span of MRP3 protein demonstrated reactivity with defined MRP3-expressing cell lines and GBM patient biopsies by Western blotting and FACS analyses, the latter establishing cell surface MRP3 protein expression. IHC evaluation of 46 GBM biopsy samples with anti-MRP3 IgG revealed MRP3 in a primarily membranous and cytoplasmic pattern in 42 (91%) of the 46 samples. Relative RNA expression was a strong predictor of survival for newly diagnosed GBM patients. Hazard of death for GBM patients with high levels of MRP3 RNA expression was 2.71 (95% CI: 1.54-4.80) times that of patients with low/moderate levels (p = 0.002).

Conclusions

Human GBMs overexpress MRP3 at both mRNA and protein levels, and elevated MRP3 mRNA levels in GBM biopsy samples correlated with a higher risk of death. These data suggest that the tumor-associated antigen MRP3 has potential use for prognosis and as a target for malignant glioma immunotherapy.

Phase II trial of bevacizumab and erlotinib in patients with recurrent malignant glioma

Vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR) signaling are established contributors to malignant glioma (MG) biology. We, therefore, evaluated bevacizumab, a humanized anti-VEGF monoclonal antibody, in combination with the EGFR tyrosine kinase inhibitor erlotinib, in this phase 2 study for recurrent MG patients (www.ClinicalTrials.gov, NCT00671970). Fifty-seven patients (n = 25, glioblastoma [GBM]; n = 32, anaplastic glioma [AG]) were enrolled. The primary endpoint was 6-month progression-free survival (PFS-6). Overall survival (OS), radiographic response, pharmacokinetics, and correlative biomarkers were the secondary endpoints. Patients were stratified based on the concurrent use of enzyme-inducing antiepileptic drugs (EIAEDs). Bevacizumab (10 mg/kg) was given intravenously every 2 weeks. Erlotinib was orally administered daily at 200 mg/day for patients not on EIAEDs and 500 mg/day for patients on EIAEDs. PFS-6 and median OS were 28% and 42 weeks for GBM patients and 44% and 71 weeks for AG patients, respectively. Twelve (48%) GBM patients and 10 (31%) AG patients achieved a radiographic response. Erlotinib pharmacokinetic exposures were comparable between EIAED and non-EIAED groups. Rash, mucositis, diarrhea, and fatigue were common but mostly grades 1 and 2. Among GBM patients, grade 3 rash, observed in 32%, was associated with survival benefit, whereas elevated hypoxia-inducible factor-2 alpha and VEGF receptor-2 levels were associated with poor survival. Bevacizumab plus erlotinib was adequately tolerated in recurrent MG patients. However, this regimen was associated with similar PFS benefit and radiographic response when compared with other historical bevacizumab-containing regimens.

Integrated genomic analyses identify ERRFI1 and TACC3 as glioblastoma-targeted genes

The glioblastoma genome displays remarkable chromosomal aberrations, which harbor critical glioblastoma-specific genes contributing to several oncogenetic pathways. To identify glioblastoma-targeted genes, we completed a multifaceted genome-wide analysis to characterize the most significant aberrations of DNA content occurring in glioblastomas. We performed copy number analysis of 111 glioblastomas by Digital Karyotyping and Illumina BeadChip assays and validated our findings using data from the TCGA (The Cancer Genome Atlas) glioblastoma project. From this study, we identified recurrent focal copy number alterations in 1p36.23 and 4p16.3. Expression analyses of genes located in the two regions revealed genes which are dysregulated in glioblastomas. Specifically, we identify EGFR negative regulator, ERRFI1, within the minimal region of deletion in 1p36.23. In glioblastoma cells with a focal deletion of the ERRFI1 locus, restoration of ERRFI1 expression slowed cell migration. Furthermore, we demonstrate that TACC3, an Aurora-A kinase substrate, on 4p16.3, displays gain of copy number, is overexpressed in a glioma-grade-specific pattern, and correlates with Aurora kinase overexpression in glioblastomas. Our multifaceted genomic evaluation of glioblastoma establishes ERRFI1 as a potential candidate tumor suppressor gene and TACC3 as a potential oncogene, and provides insight on targets for oncogenic pathway-based therapy.

IDH1(R132) mutation identified in one human melanoma metastasis, but not correlated with metastases to the brain

Isocitrate dehydrogenase 1 (IDH1) and isocitrate dehydrogenase 2 (IDH2) are enzymes which convert isocitrate to alpha-ketoglutarate while reducing nicotinamide adenine dinucleotide phosphate (NADP+to NADPH). IDH1/2 were recently identified as mutated in a large percentage of progressive gliomas. These mutations occur at IDH1(R132) or the homologous IDH2(R172). Melanomas share some genetic features with IDH1/2-mutated gliomas, such as frequent TP53 mutation. We sought to test whether melanoma is associated with IDH1/2 mutations. Seventy-eight human melanoma samples were analyzed for IDH1(R132) and IDH2(R172) mutation status. A somatic, heterozygous IDH1 c.C394T (p.R132C) mutation was identified in one human melanoma metastasis to the lung. Having identified this mutation in one metastasis, we sought to test the hypothesis that certain selective pressures in the brain environment may specifically favor the cell growth or survival of tumor cells with mutations in IDH1/2, regardless of primary tumor site. To address this, we analyzed IDH1(R132) and IDH2(R172) mutation status 53 metastatic brain tumors, including nine melanoma metastases. Results revealed no mutations in any samples. This lack of mutations would suggest that mutations in IDH1(R132) or IDH2(R172) may be necessary for the formation of tumors in a cell-lineage dependent manner, with a particularly strong selective pressure for mutations in progressive gliomas; this also suggests the lack of a particular selective pressure for growth in brain tissue in general. Studies on the cell-lineages of tumors with IDH1/2 mutations may help clarify the role of these mutations in the development of brain tumors.

Recombinant single-chain variable fragment antibodies against extracellular epitopes of human multidrug resistance protein MRP3 for targeting malignant gliomas

Multidrug resistance protein 3 (MRP3), a multidrug resistance protein identified by serial analysis of gene expression as a glioblastoma multiforme (GBM)-associated molecule, is highly expressed in GBM, but not in normal brain cells. Thus, MRP3 is a candidate for GBM immunotargeting, but to date, no monoclonal antibody has been isolated that can target an extracellular MRP3 epitope. By phage display, we have isolated 3 recombinant, fully human, single-chain Fv (scFv) antibodies, M25, M58 and M89, which specifically react with the extracellular N-terminus of human MRP3. In ELISA, these scFvs reacted only with the peptide used for screening and not with other MRP3-derived peptides. Flow cytometric analysis revealed that these scFv fragments bind specifically to viable human GBM cells displaying different MRP3 expression levels, but not to MRP3-null cells. Furthermore, these scFv antibodies failed to react with tumor cells overexpressing other MRP proteins, including MRP1, MRP2, MRP4 and MRP5. M25 and M58 also bound to viable neurospheres. Iodogen-labeled scFvs demonstrated a yield of 56-76%. The immunoreactive fractions of the radiolabeled M25, M58 and M89 scFvs were 32, 52 and 69%, respectively. M25 exhibited 20% internalization into D2159MG neurospheres, M58, 33% into D54MG cells and M89, 26% into D247MG. Immunohistochemical evaluation of human gliomas to determine the localization of MRP3 antigen using scFvs M25 and M58 showed a dense cytoplasmic and membranous staining pattern. These Fv-based recombinant antibodies, which possess superior tumor penetration capabilities and selectively target tumor cells that express MRP3, may potentially be used in immunotherapy and diagnosis for brain tumors and other cancers.

Single-stage bilateral choroid plexectomy for choroid plexus papilloma in a patient presenting with high cerebrospinal fluid output

Cerebrospinal fluid overproduction resulting in communicating hydrocephalus is observed in patients who have choroid plexus papilloma or choroid plexus carcinoma. Less often, patients with these conditions have diffuse villous hyperplasia. Prior studies report CSF production greater than 3 L per day in these patients. These patients are treated with CSF shunting or by either unilateral choroid plexectomy or staged bilateral choroid plexectomy. The authors present a patient who had a number of congenital anomalies and a karyotype that revealed balanced translocations, 5 to 7 and 9 to 11. She presented with hydrocephalus and had CSF production of 5 L per day, greater output than ever previously reported. She was treated with a single-stage bilateral choroid plexectomy. Histopathological analysis revealed a bilateral choroid plexus papilloma. Postoperatively, the patient responded well clinically and showed radiographic improvement of her hydrocephalus. Bilateral choroid plexus papilloma has been reported in the literature as a cause for neonatal and congenital hydrocephalus. It can result in high CSF output and can be successfully treated with a single-stage bilateral choroid plexectomy. Further studies are ongoing to identify genes involved in embryogenesis of the choroid plexus.

Detection of amino-terminal extracellular domain of somatostatin receptor 2 by specific monoclonal antibodies and quantification of receptor density in medulloblastoma

Somatostatin receptor 2 (SSTR2) is expressed by most medulloblastomas (MEDs). We isolated monoclonal antibodies (MAbs) to the 12-mer (33)QTEPYYDLTSNA(44), which resides in the extracellular domain of the SSTR2 amino terminus, screened the peptide-bound MAbs by fluorescence microassay on D341 and D283 MED cells, and demonstrated homogeneous cell-surface binding, indicating that all cells expressed cell surface-detectable epitopes. Five radiolabeled MAbs were tested for immunoreactive fraction (IRF), affinity (KA) (Scatchard analysis vs. D341 MED cells), and internalization by MED cells. One IgG(3) MAb exhibited a 50-100% IRF, but low KA. Four IgG(2a) MAbs had 46-94% IRFs and modest KAs versus intact cells (0.21-1.2 x 10(8) M(-1)). Following binding of radiolabeled MAbs to D341 MED at 4 degrees C, no significant internalization was observed, which is consistent with results obtained in the absence of ligand. However, all MAbs exhibited long-term association with the cells; binding at 37 degrees C after 2 h was 65-66%, and after 24 h, 52-64%. In tests with MAbs C10 and H5, the number of cell surface receptors per cell, estimated by Scatchard and quantitative FACS analyses, was 3.9 x 10(4) for the "glial" phenotype DAOY MED cell line and 0.6-8.8 x 10(5) for four neuronal phenotype MED cell lines. Our results indicate a potential immunotherapeutic application for these MAbs.

Targeting interleukin 6 signaling suppresses glioma stem cell survival and tumor growth

Glioblastomas are the most common and most lethal primary brain tumor. Recent studies implicate an important role for a restricted population of neoplastic cells (glioma stem cells (GSCs)) in glioma maintenance and recurrence. We now demonstrate that GSCs preferentially express two interleukin 6 (IL6) receptors: IL6 receptor alpha (IL6R alpha) and glycoprotein 130 (gp130). Targeting IL6R alpha or IL6 ligand expression in GSCs with the use of short hairpin RNAs (shRNAs) significantly reduces growth and neurosphere formation capacity while increasing apoptosis. Perturbation of IL6 signaling in GSCs attenuates signal transducers and activators of transcription three (STAT3) activation, and small molecule inhibitors of STAT3 potently induce GSC apoptosis. These data indicate that STAT3 is a downstream mediator of prosurvival IL6 signals in GSCs. Targeting of IL6R alpha or IL6 expression in GSCs increases the survival of mice bearing intracranial human glioma xenografts. IL6 is clinically significant because elevated IL6 ligand and receptor expression are associated with poor glioma patient survival. The potential utility of anti-IL6 therapies is demonstrated by decreased growth of subcutaneous human GSC-derived xenografts treated with IL6 antibody. Together, our data indicate that IL6 signaling contributes to glioma malignancy through the promotion of GSC growth and survival, and that targeting IL6 may offer benefit for glioma patients.

Erythropoietin Receptor Signaling Through STAT3 Is Required For Glioma Stem Cell Maintenance

Recombinant erythropoietin (EPO) is a growth factor used in the treatment of chemotherapy-induced anemia, but recent studies suggest that EPO may accelerate cancer growth. Although several cancers express EPO receptors (EPORs), the mechanism by which EPOR promotes tumor growth remains poorly understood. Glioblastomas display a cellular hierarchy of self-renewal and tumor propagation restricted to glioma stem cells (GSCs). We find that GSCs express higher levels of EPOR than matched non-stem glioma cells. Prospective enrichment for EPOR on GSCs increased neurosphere formation, suggesting that EPOR can select for a subset of GSCs with increased self-renewal capacity. Targeting EPOR expression with lentiviral mediated short hairpin RNA (shRNA) reduced GSC growth, survival, and neurosphere formation capacity, defining a crucial role for EPOR in GSC maintenance. We further find that STAT3 is an important mediator of EPOR signals in GSCs. EPOR knockdown attenuated the basal activation of STAT3 present in GSCs, and a small molecule inhibitor of STAT3 reduced GSC growth and survival. EPOR signaling was critical for survival in vivo, as targeting EPOR expression decreased GSC tumorigenic potential. Elevated EPOR expression also associated with poor patient outcome. Thus, EPOR on GSCs promotes tumor growth and may explain the poor survival of cancer patients treated with EPO.

OTX2 is critical for the maintenance and progression of Shh-independent medulloblastomas

OTX2 is a developmentally regulated transcription factor involved in early morphogenesis of the central nervous system. This gene is amplified and overexpressed in medulloblastoma cell lines, but the nature and extent of its genetic alterations in primary tumors have not been evaluated. Analysis of a large cohort of primary medulloblastomas revealed frequent focal copy number gain of a region minimally containing OTX2 as a single gene. OTX2 copy number gain was restricted to tumor subtypes that did not express a molecular signature of Wnt or Shh pathway activation. FISH analysis revealed copy number gain in a subset of cells within medulloblastoma samples, suggesting a late event in tumor progression. Gain of OTX2 copy number was associated with the presence of anaplastic histologic features and shorter survival in medulloblastoma patients. In support of a functional role, ectopic OTX2 expression enhanced proliferation and tumorigenicity of immortalized primary cells, whereas OTX2 knockdown in medulloblastoma cells prolonged the survival of animals bearing xenograft tumors. Mechanistic investigations revealed upregulation of MYC as a potential mechanism whereby OTX2 promotes tumor progression. Our findings define OTX2 as an important oncogenic driver in medulloblastoma.

Treatment of HER2-positive breast carcinomatous meningitis with intrathecal administration of alpha-particle-emitting (211)At-labeled trastuzumab

INTRODUCTION

Carcinomatous meningitis (CM) is a devastating disease characterized by the dissemination of malignant tumor cells into the subarachnoid space along the brain and spine. Systemic treatment with monoclonal antibody (mAb) trastuzumab can be effective against HER2-positive systemic breast carcinoma but, like other therapies, is ineffective against CM. The goal of this study was to evaluate the therapeutic effect of alpha-particle emitting (211)At-labeled trastuzumab following intrathecal administration in a rat model of breast carcinoma CM.

METHODS

Athymic rats were injected intrathecally with MCF-7/HER2-18 breast carcinoma cells through a surgically implanted indwelling intrathecal catheter. In Experiment 1, animals received 33 or 66 muCi (211)At-labeled trastuzumab, cold trastuzumab or saline. In Experiment 2, animals were inoculated with a lower tumor burden and received 46 or 92 muCi (211)At-labeled trastuzumab or saline. In Experiment 3, animals received 28 muCi (211)At-labeled trastuzumab, 30 muCi (211)At-labeled TPS3.2 control mAb or saline. Histopathological analysis of the neuroaxis was performed at the end of the study.

RESULTS

In Experiment 1, median survival increased from 21 days for the saline and cold trastuzumab groups to 45 and 48 days for 33 and 66 muCi (211)At-labeled trastuzumab, respectively. In Experiment 2, median survival increased from 23 days for saline controls to 68 and 92 days for 46 and 92 muCi (211)At-labeled trastuzumab, respectively. In Experiment 3, median survival increased from 20 days to 29 and 36 days for animals treated with (211)At-labeled TPS3.2 and (211)At-labeled trastuzumab, respectively. Long-term survivors were observed exclusively in the (211)At-trastuzumab-treated groups.

CONCLUSION

Intrathecal (211)At-labeled trastuzumab shows promise as a treatment for patients with HER2-positive breast CM.

GMab-1, a high-affinity anti-3'-isoLM1/3',6'-isoLD1 IgG monoclonal antibody, raised in lacto-series ganglioside-defective knockout mice

The lacto-series gangliosides 3'-isoLM1 and 3',6'-isoLD1 have been identified as tumor-associated antigens whose formation is initiated by the Lc3-synthase. Until now, high-affinity IgG monoclonal antibodies (mAbs) against 3'-isoLM1 and 3',6'-isoLD1, which are highly expressed in gliomas, have not been developed, although mAbs against lacto-series gangliosides are powerful tools for functional studies. We previously produced the Lc3-synthase gene beta3Gn-T5 knockout mice. In this study, we immunized beta3Gn-T5 knockout mice with 3'-isoLM1/3',6'-isoLD1 and produced the anti-3'-isoLM1/3',6'-isoLD1 mAb GMab-1, of the IgG(3) subclass, which should be useful for functional analysis of lacto-series gangliosides and for antibody-based therapy of gliomas.

Metronomic chemotherapy with daily, oral etoposide plus bevacizumab for recurrent malignant glioma: a phase II study

Background:

We evaluated bevacizumab with metronomic etoposide among recurrent malignant glioma patients in a phase 2, open-label trial.

Methods:

A total of59 patients, including 27 with glioblastoma (GBM) and 32 with grade 3 malignant glioma, received 10 mg kg⁻¹ bevacizumab biweekly and 50 mg m⁻² etoposide daily for 21 consecutive days each month. The primary end point was a 6-month progression-free survival, and secondary end points included safety and overall survival. Vascular endothelial growth factor (VEGF), VEGFR-2, carbonic anhydrase 9 (CA9) and hypoxia-inducible factor-2α (HIF-2α) were assessed semiquantitatively in archival tumours using immunohistochemistry and were correlated with outcome.

Results:

Among grade 3 and GBM patients, the 6-month progression-free survivals were 40.6% and 44.4%, the radiographic response rates were 22% and 37% and the median survivals were 63.1 and 44.4 weeks, respectively. Hypertension predicted better outcome among both grade 3 and GBM patients, whereas high CA9 and low VEGF were associated with poorer progression-free survival (PFS) among those with GBM. The most common grade ⩾3 adverse events included neutropaenia (24%), thrombosis (12%), infection (8%) and hypertension (3%). Two patients had asymptomatic, grade 1 intracranial haemorrhage and one on-study death occurred because of pulmonary embolism.

Conclusion:

Bevacizumab with metronomic etoposide has increased toxicity compared with previous reports of bevacizumab monotherapy. Its anti-tumour activity is similar to that of bevacizumab monotherapy or bevacizumab plus irinotecan. (ClinicalTrials.gov: NCT00612430).

Glioblastoma proto-oncogene SEC61gamma is required for tumor cell survival and response to endoplasmic reticulum stress

Glioblastoma multiforme is the most prevalent type of adult brain tumor and one of the deadliest tumors known to mankind. The genetic understanding of glioblastoma multiforme is, however, limited, and the molecular mechanisms that facilitate glioblastoma multiforme cell survival and growth within the tumor microenvironment are largely unknown. We applied digital karyotyping and single nucleotide polymorphism arrays to screen for copy-number changes in glioblastoma multiforme samples and found that the most frequently amplified region is at chromosome 7p11.2. The high resolution of digital karyotyping and single nucleotide polymorphism arrays permits the precise delineation of amplicon boundaries and has enabled identification of the minimal region of amplification at chromosome 7p11.2, which contains two genes, EGFR and SEC61gamma. SEC61gamma encodes a subunit of a heterotrimeric protein channel located in the endoplasmic reticulum (ER). In addition to its high frequency of gene amplification in glioblastoma multiforme, SEC61gamma is also remarkably overexpressed in 77% of glioblastoma multiforme but not in lower-grade gliomas. The small interfering RNA-mediated knockdown of SEC61gamma expression in tumor cells led to growth suppression and apoptosis. Furthermore, we showed that pharmacologic ER stress agents induce SEC61gamma expression in glioblastoma multiforme cells. Together, these results indicate that aberrant expression of SEC61gamma serves significant roles in glioblastoma multiforme cell survival likely via a mechanism that is involved in the cytoprotective ER stress-adaptive response to the tumor microenvironment.

A monoclonal antibody IMab-1 specifically recognizes IDH1R132H, the most common glioma-derived mutation

IDH1 (isocitrate dehydrogenase 1) mutations have been identified as early and frequent genetic alterations in astrocytomas, oligodendrogliomas, and oligoastrocytomas as well as secondary glioblastomas. In contrast, primary glioblastomas very rarely contain IDH1 mutations, although primary and secondary glioblastomas are histologically indistinguishable. The IDH1 mutations are remarkably specific to a single codon in the conserved and functionally important Arg132 in IDH1. In gliomas, the most frequent IDH1 mutations (>90%) were G395A (R132H). In this study, we immunized mice with R132H-containing IDH1 (IDH1(R132H)) peptide. After cell fusion using Sendai virus envelope, the monoclonal antibodies (mAbs), which specifically reacted with IDH1(R132H), were screened in ELISA. One of the mAbs, IMab-1 reacted with the IDH1(R132H) peptide, but not with wild type IDH1 (IDH1(wt)) peptide in ELISA. In Western-blot analysis, IMab-1 reacted with only the IDH1(R132H) protein, not IDH1(wt) protein or the other IDH1 mutants, indicating that IMab-1 is IDH1(R132H)-specific. Furthermore, IMab-1 specifically stained the IDH1(R132H)-expressing cells in astrocytomas in immunohistochemistry, whereas it did not react with IDH1(R132H)-negative primary glioblastoma sections. In conclusion, we established an anti-IDH1(R132H)-specific monoclonal antibody IMab-1, which should be significantly useful for diagnosis and biological evaluation of mutation-bearing gliomas.

The hypoxic microenvironment maintains glioblastoma stem cells and promotes reprogramming towards a cancer stem cell phenotype

Glioblastomas are highly lethal cancers that contain cellular hierarchies with self-renewing cancer stem cells that can propagate tumors in secondary transplant assays. The potential significance of cancer stem cells in cancer biology has been demonstrated by studies showing contributions to therapeutic resistance, angiogenesis and tumor dispersal. We recently reported that physiologic oxygen levels differentially induce hypoxia inducible factor-2alpha (HIF2alpha) levels in cancer stem cells. HIF1alpha functioned in proliferation and survival of all cancer cells but also was activated in normal neural progenitors suggesting a potentially restricted therapeutic index while HIF2alpha was essential in only in cancer stem cells and was not expressed by normal neural progenitors demonstrating HIF2alpha is a cancer stem cell specific target. We now extend these studies to examine the role of hypoxia in regulating tumor cell plasticity. We find that hypoxia promotes the self-renewal capability of the stem and non-stem population as well as promoting a more stem-like phenotype in the non-stem population with increased neurosphere formation as well as upregulation of important stem cell factors, such as OCT4, NANOG and c-MYC. The importance of HIF2alpha was further supported as forced expression of non-degradable HIF2alpha induced a cancer stem cell marker and augmented the tumorigenic potential of the non-stem population. This novel finding may indicate a specific role of HIF2alpha in promoting glioma tumorigenesis. The unexpected plasticity of the non-stem glioma population and the stem-like phenotype emphasizes the importance of developing therapeutic strategies targeting the microenvironmental influence on the tumor in addition to cancer stem cells.

EGFRvIII-targeted vaccination therapy of malignant glioma

Given the highly infiltrative growth pattern of malignant glioma and the lack of specificity associated with currently available treatment regimens, alternative strategies designed to eradicate cancer cells while limiting collateral toxicity in normal tissues remain a high priority. To this end, the development of specific immunotherapies against targeted neoplastic cells represents a promising approach. The epidermal growth factor receptor class III variant (EGFRvIII), a constitutively activated mutant of the wild-type tyrosine kinase, is present in a substantial proportion of malignant gliomas and other human cancers, yet completely absent from normal tissues. This receptor variant consists of an in-frame deletion, the translation of which produces an extracellular junction with a novel glycine residue, flanked by amino acid sequences that are not typically adjacent in the normal protein. In this review, both preclinical and early clinical development of a peptide vaccine directed against this portion of the EGFRvIII antigenic domain are recapitulated. Following vaccination, our group has demonstrated potent, redirected cellular and humoral immunity against cancer cells expressing the mutant receptor without significant toxicity. Additionally, the corresponding therapeutic outcomes observed in these studies lend credence to the potential role of peptide-based vaccination strategies among emerging antitumor immunotherapies in patients with malignant glioma.

Phase 1 trial of temozolomide plus irinotecan plus O6-benzylguanine in adults with recurrent malignant glioma

BACKGROUND

The current study was a phase 1 clinical trial conducted with patients who had recurrent or progressive malignant glioma (MG). The trial was designed to determine the maximum tolerated dose (MTD) and toxicity of irinotecan (CPT-11) when administered with temozolomide (TMZ) and O(6)-benzylguanine (O(6)-BG).

METHODS

All 3 drugs, CPT-11, TMZ, and O(6)-BG, were administered on Day 1 of a 21-day treatment. First, patients were treated with a 1-hour bolus infusion of O(6)-BG at a dose of 120 mg/m(2) followed immediately by a 48-hour continuous infusion of O(6)-BG at a dose of 30 mg/m(2)/d. Second, within 60 minutes of the end of the 1-hour bolus infusion of O(6)-BG, TMZ was administered orally at a dose of 355 mg/m(2). Third, 1 hour after administration of TMZ, CPT-11 was infused over 90 minutes. Patients were accrued to 1 of 2 strata based on CYP3A1- and CYP3A4-inducing antiepileptic drug (EIAED) use; dose escalation was conducted independently within these strata.

RESULTS

Fifty-five patients were enrolled. In both strata, the dose-limiting toxicities were hematologic and included grade 4 neutropenia, febrile neutropenia, leukopenia, and/or thrombocytopenia. For Stratum 1 (EIAEDs), when TMZ was administered at a dose of 355 mg/m(2), the MTD of CPT-11 was determined to be 120 mg/m(2). In contrast, for Stratum 2 (no EIAEDs), when TMZ was administered at a dose of 200 mg/m(2), the MTD of CPT-11 was determined to be 80 mg/m(2).

CONCLUSIONS

The authors believe that the results of the current study provide the foundation for a phase 2 trial of O(6)-BG in combination with CPT-11 and TMZ in patients with MG.

Phase II trial of Gliadel plus O6-benzylguanine in adults with recurrent glioblastoma multiforme

PURPOSE

This phase II trial was designed to define the efficacy of Gliadel wafers in combination with an infusion of O6-benzylguanine (O6-BG) that suppresses tumor O6-alkylguanine-DNA alkyltransferase (AGT) levels in patients with recurrent glioblastoma multiforme for 5 days and to evaluate the safety of this combination therapy.

EXPERIMENTAL DESIGN

This was a phase II, open-label, single center trial. On gross total resection of the tumor, up to eight Gliadel wafers were implanted. Bolus infusion of O6-BG was administered at 120 mg/m2 over 1 hour on days 1, 3, and 5, along with a continuous infusion at 30 mg/m2/d. The primary end points were 6-month overall survival (OS) and safety, and the secondary end points were 1-year, 2-year, and median OS.

RESULTS

Fifty-two patients were accrued. The 6-month OS was 82% [95% confidence interval (95% CI), 72-93%]. The 1- and 2-year OS rates were 47% (95% CI, 35-63%) and 10% (95% CI, 3-32%), respectively. The median OS was 50.3 weeks (95% CI, 36.1-69.4 weeks). Treatment-related toxicity with this drug combination included grade 3 hydrocephalus (9.6%), grade 3 cerebrospinal fluid (CSF) leak (19.2%), and grade 3 CSF/brain infection (13.4%).

CONCLUSION

The efficacy of implanted Gliadel wafers may be improved with the addition of O6-BG. Although systemically administered O6-BG can be coadministered with Gliadel wafers safely, it may increase the risk of hydrocephalus, CSF leak, and CSF/brain infection. Future trials are required to verify that inhibition of tumor AGT levels by O6-BG results in increased efficacy of Gliadel wafers without added toxicity.

Phase 2 trial of erlotinib plus sirolimus in adults with recurrent glioblastoma

We evaluated the anti-tumor activity and safety of erlotinib, a receptor tyrosine kinase inhibitor of the epidermal growth factor receptor, plus sirolimus, an inhibitor of the mammalian target of rapamycin, among patients with recurrent glioblastoma (GBM) in a phase 2, open-label, single-arm trial. Thirty-two patients received daily erlotinib and sirolimus. The doses of erlotinib and sirolimus were 150 mg and 5 mg for patients not on concurrent CYP3A-inducing anti-epileptics (EIAEDS), and 450 mg and 10 mg for patients on EIAEDS. Evaluations were performed every two months. The primary endpoint was 6-month progression-free survival and secondary endpoints included safety and overall survival. Archival tumor samples were assessed for EGFR, EGFRvIII, PTEN, pAKT and pS6. Enrolled patients were heavily pre-treated including 53% who had received three or more prior chemotherapy agents and 28% who had received prior bevacizumab therapy. The most common grade > or = 2 adverse events were rash (59%), mucositis (34%) and diarrhea (31%). Grade 3 or higher events were rare. Best radiographic response included stable disease in 15 patients (47%); no patients achieved either a CR or PR. The estimated 6-month progression-free survival was 3.1% for all patients. Progression-free survival was better for patients not on EIAEDs (P = 0.03). Tumor markers failed to show an association with PFS except for increased pAKT expression which achieved borderline significance (P = 0.045). Although neither rash nor diarrhea had an association with outcome, hyperlipidemia was associated with longer PFS (P = 0.029). Erlotinib plus sirolimus was well tolerated but had negligible activity among unselected recurrent GBM patients. (ClinicalTrials.gov number: NCT0062243).

Phase II trial of temozolomide (TMZ) plus irinotecan (CPT-11) in adults with newly diagnosed glioblastoma multiforme before radiotherapy

This phase II trial evaluated efficacy and safety of temozolomide (TMZ) in combination with irinotecan (CPT-11) before radiotherapy in patients with newly diagnosed glioblastoma multiforme (GBM). Prior to radiotherapy, patients were treated with a maximum of three 6-week cycles of TMZ and CPT-11. Patients received TMZ at a dose of 200 mg/m(2)/day on days 1-5 and CPT-11 on days 1, 8, 22, and 29, with a dose adjustment for enzyme-inducing antiepileptic drug use. The primary end point was objective response rate (ORR). Secondary end points included progression-free survival (PFS), overall survival (OS), safety, and tumor O(6)-methylguanine-DNA methyltransferase (MGMT) expression. Of the 42 patients treated, 8 (19%) patients achieved a partial response. Median PFS and median OS were 3.1 and 13.8 months, respectively. Grade 3 or 4 AEs were documented in 36% of patients, most of which were hematologic (29%). Twenty-four percent of patients had grade 3 or 4 non-hematologic AEs, with gastrointestinal AEs being the most common (12%) Two patients died, one of intracranial hemorrhage and one of treatment-related renal failure. Low MGMT expression, compared with high MGMT expression, showed no significant difference in ORR (25 vs. 8%), median PFS (14 vs. 5 months) or OS (21 vs. 15 months). Although TMZ plus CPT-11 is at least comparable in efficacy to TMZ alone, this combination appears more toxic and poorly tolerated. The lack of correlation of activity with MGMT expression is intriguing, but needs further evaluation in subsequent trials.

Hypoxia-inducible factors regulate tumorigenic capacity of glioma stem cells

Glioblastomas are lethal cancers characterized by florid angiogenesis promoted in part by glioma stem cells (GSCs). Because hypoxia regulates angiogenesis, we examined hypoxic responses in GSCs. We now demonstrate that hypoxia-inducible factor HIF2alpha and multiple HIF-regulated genes are preferentially expressed in GSCs in comparison to non-stem tumor cells and normal neural progenitors. In tumor specimens, HIF2alpha colocalizes with cancer stem cell markers. Targeting HIFs in GSCs inhibits self-renewal, proliferation, and survival in vitro, and attenuates tumor initiation potential of GSCs in vivo. Analysis of a molecular database reveals that HIF2A expression correlates with poor glioma patient survival. Our results demonstrate that GSCs differentially respond to hypoxia with distinct HIF induction patterns, and HIF2alpha might represent a promising target for antiglioblastoma therapies.

Phase I trial of temozolomide plus O6-benzylguanine 5-day regimen with recurrent malignant glioma

This phase I clinical trial conducted with patients who had recurrent or progressive malignant glioma (MG) was designed to determine the maximum tolerated dose (MTD) and toxicity of three different 5-day dosing regimens of temozolomide (TMZ) in combination with O(6)-benzylguanine (O(6)-BG). Both TMZ and O(6)-BG were administered on days 1-5 of a 28-day treatment cycle. A bolus infusion of O(6)-BG was administered at 120 mg/m(2) over 1 h on days 1, 3, and 5, along with a continuous infusion of O(6)-BG at 30 mg/m(2)/day. TMZ was administered at the end of the first bolus infusion of O(6)-BG and then every 24 h for 5 days during the continuous infusion of O(6)-BG. Patients were accrued to one of three 5-day dosing regimens of TMZ. Twenty-nine patients were enrolled into this study. The dose-limiting toxicities (DLTs) were grade 4 neutropenia, leukopenia, and thrombocytopenia. The MTD for TMZ for the three different 5-day dosing schedules was determined as follows: schedule 1, 200 mg/m(2) on day 1 and 50 mg/m(2)/day on days 2-5; schedule 2, 50 mg/m(2)/day on days 1-5; and schedule 3, 50 mg/m(2)/day on days 1-5 while receiving pegfilgrastim. Thus, the 5-day TMZ dosing schedule that maximized the total dose of TMZ when combined with O(6)-BG was schedule 1. This study provides the foundation for a phase II trial of O(6)-BG in combination with a 5-day dosing schedule of TMZ in TMZ-resistant MG.

Phase II trial of temozolomide plus o6-benzylguanine in adults with recurrent, temozolomide-resistant malignant glioma

PURPOSE

This phase II trial was designed to define the role of O(6)-benzylguanine (O(6)-BG) in restoring temozolomide sensitivity in patients with recurrent or progressive, temozolomide-resistant malignant glioma and to evaluate the safety of administering O(6)-BG in combination with temozolomide.

PATIENTS AND METHODS

Patients were accrued into two independent strata on the basis of histology: glioblastoma multiforme (GBM) and anaplastic glioma. Both temozolomide and O(6)-BG were administered on day 1 of a 28-day treatment cycle. Patients were administered a 1-hour O(6)-BG infusion at a dose of 120 mg/m(2) followed immediately by a 48-hour infusion at a dose of 30 mg/m(2)/d. Temozolomide was administered orally within 60 minutes of the end of the 1-hour O(6)-BG infusion at a dose of 472 mg/m(2). The primary end point was objective response rate. Secondary end points included progression-free survival, overall survival, and safety.

RESULTS

Sixty-six of 67 patients who enrolled were treated with temozolomide and O(6)-BG. One of 34 patients (3%) with GBM (95% CI, 0.1% to 15%) and five of 32 assessable patients (16%) with anaplastic glioma (95% CI, 5% to 33%) were responders. The most commonly reported adverse events were grade 4 hematologic events experienced in 48% of the patients.

CONCLUSION

O(6)-BG when added to a 1-day dosing regimen of temozolomide was able to restore temozolomide sensitivity in patients with temozolomide-resistant anaplastic glioma, but there seemed to be no significant restoration of temozolomide sensitivity in patients with temozolomide-resistant GBM.

Identification of CD15 as a marker for tumor-propagating cells in a mouse model of medulloblastoma

The growth of many cancers depends on self-renewing cells called cancer stem cells or tumor-propagating cells (TPCs). In human brain tumors, cells expressing the stem cell marker CD133 have been implicated as TPCs. Here we show that tumors from a model of medulloblastoma, the Patched mutant mouse, are propagated not by CD133(+) cells but by cells expressing the progenitor markers Math1 and CD15/SSEA-1. These cells have a distinct expression profile that suggests increased proliferative capacity and decreased tendency to undergo apoptosis and differentiation. CD15 is also found in a subset of human medulloblastomas, and tumors expressing genes similar to those found in murine CD15(+) cells have a poorer prognosis. Thus, CD15 may represent an important marker for TPCs in medulloblastoma.

Few isolated neurons in hypothalamic hamartomas may cause gelastic seizures

Hypothalamic hamartomas (HHs) are congenital, benign masses in the hypothalamus and tuber cinereum that may cause central precocious puberty and gelastic seizures. Nodules of small neurons are thought to be a universal feature of the microarchitecture of HH lesions associated with epilepsy. Here we describe the case of a 5-year-old boy with gelastic seizures who underwent resection of a HH that contained nodules of glial cells, but only few, randomly distributed neurons. HHs that contain few or no neurons have only been reported thus far in cases associated with precocious puberty. This case demonstrates that few solitary neurons in HHs can drive the development of gelastic seizures, and nodules of small neurons may not be a universal feature of HHs associated with epilepsy. This finding is clinically important since hypothalamic hamartomas with rare neurons can easily be misdiagnosed as pilocytic astrocytomas or subependymomas if their presence is overlooked. A neuronal stain is helpful in making the correct diagnosis in these cases.

c-Myc is required for maintenance of glioma cancer stem cells

Background

Malignant gliomas rank among the most lethal cancers. Gliomas display a striking cellular heterogeneity with a hierarchy of differentiation states. Recent studies support the existence of cancer stem cells in gliomas that are functionally defined by their capacity for extensive self-renewal and formation of secondary tumors that phenocopy the original tumors. As the c-Myc oncoprotein has recognized roles in normal stem cell biology, we hypothesized that c-Myc may contribute to cancer stem cell biology as these cells share characteristics with normal stem cells.

Methodology/Principal Findings

Based on previous methods that we and others have employed, tumor cell populations were enriched or depleted for cancer stem cells using the stem cell marker CD133 (Prominin-1). We characterized c-Myc expression in matched tumor cell populations using real time PCR, immunoblotting, immunofluorescence and flow cytometry. Here we report that c-Myc is highly expressed in glioma cancer stem cells relative to non-stem glioma cells. To interrogate the significance of c-Myc expression in glioma cancer stem cells, we targeted its expression using lentivirally transduced short hairpin RNA (shRNA). Knockdown of c-Myc in glioma cancer stem cells reduced proliferation with concomitant cell cycle arrest in the G₀/G₁ phase and increased apoptosis. Non-stem glioma cells displayed limited dependence on c-Myc expression for survival and proliferation. Further, glioma cancer stem cells with decreased c-Myc levels failed to form neurospheres in vitro or tumors when xenotransplanted into the brains of immunocompromised mice.

Conclusions/Significance

These findings support a central role of c-Myc in regulating proliferation and survival of glioma cancer stem cells. Targeting core stem cell pathways may offer improved therapeutic approaches for advanced cancers.

Brain cancer stem cells display preferential sensitivity to Akt inhibition

Malignant brain tumors are among the most lethal cancers, and conventional therapies are largely limited to palliation. Novel therapies targeted against specific molecular pathways may offer superior efficacy and less toxicity than conventional therapies, but initial clinical trials of molecular targeted agents in brain cancer therapy have been frequently disappointing. In brain tumors and other cancers, subpopulations of tumor cells have recently been characterized by their ability to self-renew and initiate tumors. Although these cancer stem cells, or tumor initiating cells, are often only present in small numbers in human tumors, mounting evidence suggests that cancer stem cells contribute to tumor maintenance and therapeutic resistance. Thus, the development of therapies that target cancer stem cell signal transduction and biology may improve brain tumor patient survival. We now demonstrate that populations enriched for cancer stem cells are preferentially sensitive to an inhibitor of Akt, a prominent cell survival and invasion signaling node. Treatment with an Akt inhibitor more potently reduced the numbers of viable brain cancer stem cells relative to matched nonstem cancer cells associated with a preferential induction of apoptosis and a suppression of neurosphere formation. Akt inhibition also reduced the motility and invasiveness of all tumor cells but had a greater impact on cancer stem cell behaviors. Furthermore, inhibition of Akt activity in cancer stem cells increased the survival of immunocompromised mice bearing human glioma xenografts in vivo. Together, these results suggest that Akt inhibitors may function as effective anticancer stem cell therapies.

Targeting cancer stem cells through L1CAM suppresses glioma growth

Malignant gliomas are lethal cancers that display striking cellular heterogeneity. A highly tumorigenic glioma tumor subpopulation, termed cancer stem cells or tumor-initiating cells, promotes therapeutic resistance and tumor angiogenesis. Therefore, targeting cancer stem cells may improve patient survival. We interrogated the role of a neuronal cell adhesion molecule, L1CAM, in glioma stem cells as L1CAM regulates brain development and is expressed in gliomas. L1CAM(+) and CD133(+) cells cosegregated in gliomas, and levels of L1CAM were higher in CD133(+) glioma cells than normal neural progenitors. Targeting L1CAM using lentiviral-mediated short hairpin RNA (shRNA) interference in CD133(+) glioma cells potently disrupted neurosphere formation, induced apoptosis, and inhibited growth specifically in glioma stem cells. We identified a novel mechanism for L1CAM regulation of cell survival as L1CAM knockdown decreased expression of the basic helix-loop-helix transcription factor Olig2 and up-regulated the p21(WAF1/CIP1) tumor suppressor in CD133(+) glioma cells. To determine if targeting L1CAM was sufficient to reduce glioma stem cell tumor growth in vivo, we targeted L1CAM in glioma cells before injection into immunocompromised mice or directly in established tumors. In each glioma xenograft model, shRNA targeting of L1CAM expression in vivo suppressed tumor growth and increased the survival of tumor-bearing animals. Together, these data show that L1CAM is required for maintaining the growth and survival of CD133(+) glioma cells both in vitro and in vivo, and L1CAM may represent a cancer stem cell-specific therapeutic target for improving the treatment of malignant gliomas and other brain tumors.

Mismatch repair deficiency does not mediate clinical resistance to temozolomide in malignant glioma

PURPOSE

A major mechanism of resistance to methylating agents, including temozolomide, is the DNA repair protein O(6)-alkylguanine-DNA alkyltransferase (AGT). Preclinical data indicates that defective DNA mismatch repair (MMR) results in tolerance to temozolomide regardless of AGT activity. The purpose of this study was to determine the role of MMR deficiency in mediating resistance in samples from patients with both newly diagnosed malignant gliomas and those who have failed temozolomide therapy.

EXPERIMENTAL DESIGN

The roles of AGT and MMR deficiency in mediating resistance in glioblastoma multiforme were assessed by immunohistochemistry and microsatellite instability (MSI), respectively. The mutation status of the MSH6 gene, a proposed correlate of temozolomide resistance, was determined by direct sequencing and compared with data from immunofluorescent detection of MSH6 protein and reverse transcription-PCR amplification of MSH6 RNA.

RESULTS

Seventy percent of newly diagnosed and 78% of failed-therapy glioblastoma multiforme samples expressed nuclear AGT protein in > or = 20% of cells analyzed, suggesting alternate means of resistance in 20% to 30% of cases. Single loci MSI was observed in 3% of patient samples; no sample showed the presence of high MSI. MSI was not shown to correlate with MSH6 mutation or loss of MSH6 protein expression.

CONCLUSIONS

Although high AGT levels may mediate resistance in a portion of these samples, MMR deficiency does not seem to be responsible for mediating temozolomide resistance in adult malignant glioma. Accordingly, the presence of a fraction of samples exhibiting both low AGT expression and MMR proficiency suggests that additional mechanisms of temozolomide resistance are operational in the clinic.

Efficacy of high-dose chemotherapy or standard salvage therapy in patients with recurrent medulloblastoma

The efficacy of high-dose chemotherapy (HDC) or standard salvage therapy was evaluated in patients with recurrent medulloblastoma (MBL) using retrospective chart review of all patients with recurrent MBL treated at Duke University Medical Center between 1995 and 2005 and who had undergone HDC with or without radiotherapy (RT) or standard salvage therapy after relapse. A total of 30 patients were diagnosed with recurrent MBL after standard RT alone or chemotherapy with RT. Nineteen patients (7 who received no RT before recurrence [group A] and 12 who received definitive RT before recurrence [group B]) underwent surgery and/or induction chemotherapy followed by HDC plus autologous stem-cell rescue. Eleven patients (group C) underwent standard salvage therapy. Six of seven group A patients also received standard RT just before or after recovery from HDC, and 5 of 12 group B patients received adjuvant palliative focal RT post-HDC. At a median follow-up of 28 months, three of seven patients in group A are alive and disease-free at >or=34, >or=110, and >or=116 months, respectively, post-HDC. All patients in groups B and C have died of tumor, at a median of 35 months and 26 months from HDC and standard salvage therapy, respectively. HDC or standard salvage therapy was ineffective in our patients with recurrent MBL who had received standard RT before recurrence. The favorable impact of HDC on disease control in the two long-term survivors cannot be clearly established due to the cofounding effect of definitive RT postrecurrence.

Chordoid glioma: a case report and molecular characterization of five cases

Chordoid gliomas are rare, slow-growing neoplasms of the anterior third ventricle. We reported a case of chordoid glioma in a 41-year-old man with obstructive hydrocephalus. Histologically, the tumor consisted of polygonal epithelioid cells admixed with elongated cells in a myxoid stroma. A prominent lymphoplasmacytic infiltrate was present. The tumor cells expressed glial fibrillary acidic protein (GFAP), epithelial membrane antigen (EMA), vimentin, CD31, CD34, epidermal growth factor receptor (EGFR) and S100 but were negative for pankeratin and E-cadherin. The percentage of Ki67 positive cells was approximately 3%. Weak p53 immunoreactivity was seen in less than 10% of the cells. Array comparative genomic hybridization performed on this case, as well as on four other archived cases, showed losses at several loci. Fluorescence in situ hybridization (FISH) confirmed consistent genetic alterations at 9p21 and 11q13. These are the fifth through ninth reported cases of chordoid gliomas with molecular characterization suggesting a distinct genetic origin from other gliomas.

Surgical neuropathology update: a review of changes introduced by the WHO classification of tumours of the central nervous system, 4th edition

CONTEXT

The World Health Organization (WHO) recently published its 4th edition of the classification of tumors of the central nervous system, incorporating a substantial number of important changes to the previous version (WHO 2000). The new WHO classification introduces 7 changes in the grading of central nervous system neoplasms, ranging in significance from minor to major, in categories of anaplastic oligoastrocytomas, meningiomas, choroid plexus tumors, pineal parenchymal tumors, ganglioglioma, cerebellar liponeurocytoma, and hemangiopericytomas. The 4th edition also introduces 10 newly codified entities, variants, and patterns, as well as 1 new genetic syndrome. A number of established brain tumors are reorganized, including medulloblastomas and primitive neuroectodermal tumors, in an attempt to more closely align classification with current understanding of central nervous system neoplasia.

OBJECTIVE

To summarize and discuss the most significant updates in the 4th edition for the practicing surgical pathologist, including (1) changes in grading among established entities; (2) newly codified tumor entities, variants, patterns, and syndromes; and (3) changes in the classification of existing brain tumors.

DATA SOURCES

The primary source for this review is the WHO Classification of Tumours of the Central Nervous System, 4th edition. Other important sources include the 3rd edition of this book and the primary literature that supported changes in the 4th edition.

CONCLUSIONS

The new edition of the WHO blue book reflects advancements in the understanding of brain tumors in terms of classification, grading, and new entities. The changes introduced are substantial and will have an impact on the practice of general surgical pathologists and neuropathologists.

Issues of diagnostic review in brain tumor studies: from the Brain Tumor Epidemiology Consortium

Epidemiologists routinely conduct centralized single pathology reviews to minimize interobserver diagnostic variability, but this practice does not facilitate the combination of studies across geographic regions and institutions where diagnostic practices differ. A meeting of neuropathologists and epidemiologists focused on brain tumor classification issues in the context of protocol needs for consortial studies (http://epi.grants.cancer.gov/btec/). It resulted in recommendations relevant to brain tumors and possibly other rare disease studies. Two categories of brain tumors have enough general agreement over time, across regions, and between individual pathologists that one can consider using existing diagnostic data without further review: glioblastomas and meningiomas (as long as uniform guidelines such as those provided by the WHO are used). Prospective studies of these tumors benefit from collection of pathology reports, at a minimum recording the pathology department and classification system used in the diagnosis. Other brain tumors, such as oligodendroglioma, are less distinct and require careful histopathologic review for consistent classification across study centers. Epidemiologic study protocols must consider the study specific aims, diagnostic changes that have taken place over time, and other issues unique to the type(s) of tumor being studied. As diagnostic changes are being made rapidly, there are no readily available answers on disease classification issues. It is essential that epidemiologists and neuropathologists collaborate to develop appropriate study designs and protocols for specific hypothesis and populations.

Intracerebral infusion of an EGFR-targeted toxin in recurrent malignant brain tumors

The purpose of this study is to determine the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), and intracerebral distribution of a recombinant toxin (TP-38) targeting the epidermal growth factor receptor in patients with recurrent malignant brain tumors using the intracerebral infusion technique of convection-enhanced delivery (CED). Twenty patients were enrolled and stratified for dose escalation by the presence of residual tumor from 25 to 100 ng/ml in a 40-ml infusion volume. In the last eight patients, coinfusion of (123)I-albumin was performed to monitor distribution within the brain. The MTD was not reached in this study. Dose escalation was stopped at 100 ng/ml due to inconsistent drug delivery as evidenced by imaging the coinfused (123)I-albumin. Two DLTs were seen, and both were neurologic. Median survival after TP-38 was 28 weeks (95% confidence interval, 26.5-102.8). Of 15 patients treated with residual disease, two (13.3%) demonstrated radiographic responses, including one patient with glioblastoma multiforme who had a nearly complete response and remains alive >260 weeks after therapy. Coinfusion of (123)I-albumin demonstrated that high concentrations of the infusate could be delivered >4 cm from the catheter tip. However, only 3 of 16 (19%) catheters produced intraparenchymal infusate distribution, while the majority leaked infusate into the cerebrospinal fluid spaces. Intracerebral CED of TP-38 was well tolerated and produced some durable radiographic responses at doses <or=100 ng/ml. CED has significant potential for enhancing delivery of therapeutic macromolecules throughout the human brain. However, the potential efficacy of drugs delivered by this technique may be severely constrained by ineffective infusion in many patients.

A pilot study: 131I-antitenascin monoclonal antibody 81c6 to deliver a 44-Gy resection cavity boost

The purpose of this study was to determine the feasibility and assess the efficacy and toxicity, among newly diagnosed malignant glioma patients, of administering (131)I-labeled murine antitenascin monoclonal antibody 81C6 ((131)I-81C6) into a surgically created resection cavity (SCRC) to achieve a patient-specific, 44-Gy boost to the 2-cm SCRC margin. A radioactivity dose of (131)I-81C6 calculated to achieve a 44-Gy boost to the SCRC was administered, followed by conventional external beam radiotherapy (XRT) and chemotherapy. Twenty-one patients were enrolled in the study: 16 with glioblastoma multiforme (GBM) and 5 with anaplastic astrocytoma. Twenty patients received the targeted 44-Gy boost (+/-10%) to the SCRC. Attributable toxicity was mild and limited to reversible grade 3 neutropenia or thrombocytopenia (n = 3; 14%), CNS wound infections (n = 3; 14%), and headache (n = 2; 10%). With a median follow-up of 151 weeks, median overall survival times for all patients and those with GBM are 96.6 and 90.6 weeks, respectively; 87% of GBM patients are alive at 1 year. It is feasible to consistently achieve a 44-Gy boost dose to the SCRC margin with patient-specific dosing of (131)I-81C6. Our study regimen ((131)I-81C6 + XRT + temozolomide) was well tolerated and had encouraging survival. To determine if selection of good-prognosis patients affects outcome associated with this approach, the U.S. Food and Drug Administration has approved a trial randomizing newly diagnosed GBM patients to either our study regimen or standard XRT plus temozolomide.

Utility of EGFR and PTEN numerical aberrations in the evaluation of diffusely infiltrating astrocytomas. Laboratory investigation

OBJECT

Diffusely infiltrating astrocytomas are the most common primary brain tumors. As a group, they demonstrate an inherent tendency toward malignant progression. Histological grading using the guidelines of the World Health Organization (WHO) remains the gold standard for predicting the biological behavior of these tumors. Although useful, this grading system is often limited due to small sample sizes and the subjectivity in interpretation. Given the important roles for EGFR and PTEN in the malignant progression of astrocytomas, the authors hypothesized that the fraction of tumor cells with aberrations in these genetic loci would correlate with the histological grade.

METHODS

The authors evaluated 217 consecutive diffusely infiltrating astrocytomas that were graded using the WHO guidelines, including 16 diffuse astrocytomas (WHO Grade II), 72 anaplastic astrocytomas ([AAs] WHO Grade III), and 129 glioblastomas multiforme ([GBMs] WHO Grade IV). Cases were evaluated quantitatively using dual-color fluorescence in situ hybridization with probes for the EGFR and PTEN loci and the centromeres of chromosomes 7 and 10.

RESULTS

The population of tumor cells with polysomy of chromosome 7 and the EGFR locus and monosomy of chromosome 10 and the PTEN locus correlated significantly with histological grade. In particular, high-grade astrocytomas (that is, AAs and GBMs) had elevated fractions of tumor cells with polysomy of chromosome 7 and the EGFR locus and monosomy of chromosome 10 and the PTEN locus. Using these findings, the authors generated a mathematical model capable of subcategorizing high-grade astrocytomas. The successful model incorporated only the percentage of tumor cells with polysomy of EGFR and monosomy of PTEN, as well as patient age. The predictions of this model correlated with survival in a manner similar to histopathological grading.

CONCLUSIONS

The findings presented in this study emphasize the utility of combining histological interpretation and molecular testing in the evaluation of infiltrating astrocytomas. These results underscore the utility of building a grading framework that combines histopathological and molecular analysis.

Tumor angiogenic and hypoxic profiles predict radiographic response and survival in malignant astrocytoma patients treated with bevacizumab and irinotecan

PURPOSE

The combination of a vascular endothelial growth factor (VEGF) -neutralizing antibody, bevacizumab, and irinotecan is associated with high radiographic response rates and improved survival outcomes in patients with recurrent malignant gliomas. The aim of these retrospective studies was to evaluate tumor vascularity and expression of components of the VEGF pathway and hypoxic responses as predictive markers for radiographic response and survival benefit from the bevacizumab and irinotecan therapy.

PATIENTS AND METHODS

In a phase II trial, 60 patients with recurrent malignant astrocytomas were treated with bevacizumab and irinotecan. Tumor specimens collected at the time of diagnosis were available for further pathologic studies in 45 patients (75%). VEGF, VEGF receptor-2, CD31, hypoxia-inducible carbonic anhydrase 9 (CA9), and hypoxia-inducible factor-2alpha were semiquantitatively assessed by immunohistochemistry. Radiographic response and survival outcomes were correlated with these angiogenic and hypoxic markers.

RESULTS

Of 45 patients, 27 patients had glioblastoma multiforme, and 18 patients had anaplastic astrocytoma. Twenty-six patients (58%) had at least partial radiographic response. High VEGF expression was associated with increased likelihood of radiographic response (P = .024) but not survival benefit. Survival analysis revealed that high CA9 expression was associated with poor survival outcome (P = .016).

CONCLUSION

In this patient cohort, tumor expression levels of VEGF, the molecular target of bevacizumab, were associated with radiographic response, and the upstream promoter of angiogenesis, hypoxia, determined survival outcome, as measured from treatment initiation. Validation in a larger clinical trial is warranted.

Splenda alters gut microflora and increases intestinal p-glycoprotein and cytochrome p-450 in male rats

Splenda is comprised of the high-potency artificial sweetener sucralose (1.1%) and the fillers maltodextrin and glucose. Splenda was administered by oral gavage at 100, 300, 500, or 1000 mg/kg to male Sprague-Dawley rats for 12-wk, during which fecal samples were collected weekly for bacterial analysis and measurement of fecal pH. After 12-wk, half of the animals from each treatment group were sacrificed to determine the intestinal expression of the membrane efflux transporter P-glycoprotein (P-gp) and the cytochrome P-450 (CYP) metabolism system by Western blot. The remaining animals were allowed to recover for an additional 12-wk, and further assessments of fecal microflora, fecal pH, and expression of P-gp and CYP were determined. At the end of the 12-wk treatment period, the numbers of total anaerobes, bifidobacteria, lactobacilli, Bacteroides, clostridia, and total aerobic bacteria were significantly decreased; however, there was no significant treatment effect on enterobacteria. Splenda also increased fecal pH and enhanced the expression of P-gp by 2.43-fold, CYP3A4 by 2.51-fold, and CYP2D1 by 3.49-fold. Following the 12-wk recovery period, only the total anaerobes and bifidobacteria remained significantly depressed, whereas pH values, P-gp, and CYP3A4 and CYP2D1 remained elevated. These changes occurred at Splenda dosages that contained sucralose at 1.1-11 mg/kg (the US FDA Acceptable Daily Intake for sucralose is 5 mg/kg). Evidence indicates that a 12-wk administration of Splenda exerted numerous adverse effects, including (1) reduction in beneficial fecal microflora, (2) increased fecal pH, and (3) enhanced expression levels of P-gp, CYP3A4, and CYP2D1, which are known to limit the bioavailability of orally administered drugs.