Central Nervous System Tumor Cells Research Articles

Differential Replication and Oncolytic Effects of Zika Virus in Aggressive CNS Tumor Cells: Insights from Organoid and Tumoroid Models

Central nervous system (CNS) cancers are responsible for high rates of morbidity and mortality worldwide. Malignant CNS tumors such as adult Glioblastoma (GBM) and pediatric embryonal CNS tumors such as medulloblastoma (MED) and atypical teratoid rhabdoid tumors (ATRT) present relevant therapeutic challenges due to the lack of response to classic treatment regimens with radio and chemotherapy. Recent findings on the Zika virus’ (ZIKV) ability to infect and kill CNS neoplastic cells draw attention to the virus’ oncolytic potential. Studies demonstrating the safety of using ZIKV for treating malignant CNS tumors, enabling the translation of this approach to clinical trials, are scarce in the literature. Here we developed a co-culture model of mature human cerebral organoids assembled with GBM, MED or ATRT tumor cells and used these assembloids to test ZIKV oncolytic effect, replication potential and preferential targeting between normal and cancer cells. Our hybrid co-culture models allowed the tracking of tumor cell growth and invasion in cerebral organoids. ZIKV replication and ensuing accumulation in the culture medium was higher in organoids co-cultured with tumor cells than in isolated control organoids without tumor cells. ZIKV infection led to a significant reduction in tumor cell proportion in organoids with GBM and MED cells, but not with ATRT. Tumoroids (3D cultures of tumor cells alone) were efficiently infected by ZIKV. Interestingly, ZIKV rapidly replicated in GBM, MED, and ATRT tumoroids reaching significantly higher viral RNA accumulation levels than co-cultures. Moreover, ZIKV infection reduced viable cells number in MED and ATRT tumoroids but not in GBM tumoroids. Altogether, our findings indicate that ZIKV has greater replication rates in aggressive CNS tumor cells than in normal human cells comprising cerebral organoids. However, such higher ZIKV replication in tumor cells does not necessarily parallels oncolytic effects, suggesting cellular intrinsic and extrinsic factors mediating tumor cell death by ZIKV.

Direct Synthesis of α- and β-2'-Deoxynucleosides with Stereodirecting Phosphine Oxide via Remote Participation.

2'-Deoxynucleosides and analogues play a vital role in drug development, but their preparation remains a significant challenge. Previous studies have focused on β-2'-deoxynucleosides with the natural β-configuration. In fact, their isomeric α-2'-deoxynucleosides also exhibit diverse bioactivities and even better metabolic stability. Herein, we report that both α- and β-2'-deoxynucleosides can be prepared with high yields and stereoselectivity using a remote directing diphenylphosphinoyl (DPP) group. It is particularly efficient to prepare α-2'-deoxynucleosides with an easily accessible 3,5-di-ODPP donor. Instead of acting as a H-bond acceptor on a 2-(diphenylphosphinoyl)acetyl (DPPA) group in our previous studies for syn-facial O-glycosylation, the phosphine oxide moiety here acts as a remote participating group to enable highly antifacial N-glycosylation. This proposed remote participation mechanism is supported by our first characterization of an important 1,5-briged P-heterobicyclic intermediate via variable-temperature NMR spectroscopy. Interestingly, antiproliferative assays led to a α-2'-deoxynucleoside with IC50 values in the low micromole range against central nervous system tumor cell lines SH-SY5Y and LN229, whereas its β-anomer exhibited no inhibition at 100 μM. Furthermore, the DPP group significantly enhanced the antitumor activities by 10 times.

DUBing Primary Tumors of the Central Nervous System: Regulatory Roles of Deubiquitinases.

The ubiquitin proteasome system (UPS) utilizes an orchestrated enzymatic cascade of E1, E2, and E3 ligases to add single or multiple ubiquitin-like molecules as post-translational modification (PTM) to proteins. Ubiquitination can alter protein functions and/or mark ubiquitinated proteins for proteasomal degradation but deubiquitinases (DUBs) can reverse protein ubiquitination. While the importance of DUBs as regulatory factors in the UPS is undisputed, many questions remain on DUB selectivity for protein targeting, their mechanism of action, and the impact of DUBs on the regulation of diverse biological processes. Furthermore, little is known about the expression and role of DUBs in tumors of the human central nervous system (CNS). In this comprehensive review, we have used publicly available transcriptional datasets to determine the gene expression profiles of 99 deubiquitinases (DUBs) from five major DUB families in seven primary pediatric and adult CNS tumor entities. Our analysis identified selected DUBs as potential new functional players and biomarkers with prognostic value in specific subtypes of primary CNS tumors. Collectively, our analysis highlights an emerging role for DUBs in regulating CNS tumor cell biology and offers a rationale for future therapeutic targeting of DUBs in CNS tumors.

DDEL-17. POOLED CANCER CELL SCREENING IDENTIFIES GENOMIC DETERMINANTS OF NANOPARTICLE DELIVERY TO CANCER CELLS: SUB ANALYSIS OF CENTRAL NERVOUS SYSTEM TUMOR CELL LINES

Abstract Background There is great interest in utilizing nanoparticles to improve drug delivery to central nervous system (CNS) tumors, but the biologic features underlying successful delivery at the tumor site are not known. METHODS We developed a pooled screening assay to investigate cellular features predictive of nanoparticle delivery and screened 35 fluorescent nanoparticle formulations against 488 pooled cancer cell lines with DNA barcodes. The nanoparticle library was comprised of nonlethal liposomal or polymeric cores with varied surface functionality, including natural and synthetic polymers. Cells were profiled using fluorescence-activated cell sorting and barcodes sequenced and deconvolved to generate an association score for each nanoparticle-cell line pair. RESULTS Of 488 cancer cell lines, 22 cancer cell lineages (tissues of origin) were included. There were 35 cell lines derived from CNS tumors; of these 22 were classified as astrocytoma or glioblastoma, one as oligodendroglioma, and 2 as medulloblastoma. Of CNS tumor cell lines, 40% were from female patients and average age at cell line derivation was 52 years; TP53 hotspot mutations were detected in 25/35 lines, PTEN hotspot mutations in 15/25 lines. Using unsupervised hierarchical clustering by nanoparticle association profiles, CNS tumor lines did not cluster together by lineage, subtype, or mutation status but rather by baseline expression of genes involved in nanocarrier trafficking. Nanoparticle association profiles were heterogeneous among the CNS tumor lines for most formulations, though CNS tumor lines had high association with polystyrene formulations with respect to other lineages. Select CNS tumor lines had high uptake of liposomes coated with the natural polymers fucoidan, alginate, hyaluronic acid and chondroitin sulfate; these trends were further probed in a non-pooled screen of 5 additional cell lines. Conclusions Uptake of liposomal and polymeric nanoparticles is heterogeneous across CNS tumor lines, but can be predicted using baseline gene expression.

TBIO-07. Pediatric tumor classification through genome-wide methylation profiling of extracellular vesicle DNA

BACKGROUND: Genome-wide methylation profiling reliably classifies pediatric central nervous system (CNS) tumors. Extracellular vesicles (EVs) are released by pediatric CNS tumor cells (pCC) and contain high molecular weight tumor DNA, rendering EVs a potential biomarker source to identify tumor subgroups, stratify patients and monitor therapy by liquid biopsy. We investigated, whether the DNA in pCC-derived EVs reflects genome-wide tumor methylation profiles and allows tumor subtype classification. Currently, the tests are being expanded to include blood samples (n=80 patients). METHODS: DNA was isolated from EVs secreted by pediatric CNS tumor cells (pCC) as well as from the shortly cultured tumor cells and from the original tumor samples (n=4 patients). Pediatric Fibroblasts and EVs derived thereof were used as a non-tumorous control. EVs were classified by nanoparticle analysis (NTA), immunoblotting, imaging flow cytometry (IFCM and electron microscopy. Genome-wide DNA methylation profiling was performed using an 850k Illumina EPIC array and results were classified according to the DKFZ brain tumor classifier and further analysed by t-SNE and Copy number alteration analysis (CNA). RESULTS: The size range of pCC-derived EVs was 120-150 nm, as measured by NTA. The majority of secreted EVs exhibited high expression of common EV markers (i.e. CD9, CD63 and CD81), as characterized by IFCM. Genome-wide DNA methylation profiling of pCC-derived EVs correctly identified the methylation class of the original tumor (i.e. pilocytic astrocytoma, medulloblastoma). In addition, t-SNE analysis and copy number alterations matched the pattern of the parental pCC and original tumor samples. CONCLUSION: EV DNA faithfully reflects the tumor methylation class and copy number alterations present in the parental cells and the original tumor. Methylation profiling of circulating tumor EV DNA could become a useful tool to detect and classify pediatric CNS tumors.

MODL-05 Metronomic Intrathecal Delivery of CDK4/6 Inhibitors in Preclinical Models of Pediatric Brain Tumors

INTRODUCTION: CDK4/6 inhibitors have shown promise against central nervous system (CNS) tumors in vitro. This class of drugs relies on long-term exposure. Their use in early phase clinical studies in children with CNS tumors has defined dose limitations due to systemic toxicity. We have sought to circumvent these limitations in using CDK4/6 inhibitors for pediatric CNS tumors by first demonstrating enhanced efficiency with long-term administration and exploiting prolonged intrathecal delivery (IT). METHODS: Pediatric CNS tumor cell lines were used for cell viability assays: ATRT (BT-12, BT-16), CPC (CCHE-45), diffuse midline glioma (DIPG-XIII, HSJD-007), and medulloblastoma (DAOY); the assays were conducted at 24h, 72h, and 7d post-administration of CDK4/6 inhibitors (abemaciclib, palbociclib, ribociclib). Half maximal growth inhibitory concentrations (GI50) and areas under the curve (AUC) were compared for short-term (24h, 72h) and long-term (7d) dose-response curves. Toxicity with chronic IT administration was assessed using a neurobehavioral safety profile of 7-day continuous infusion of 2.5mM palbociclib (n = 5) into the mouse lateral ventricle compared with vehicle (n = 4). RESULTS: Our results demonstrate increased CDK4/6 inhibitor potency with longer administration. The greatest reductions in short-term to long-term GI50 were observed in ATRT, CPC, and DIPG across all inhibitors. The most pronounced time-dependent efficacy was observed with palbociclib for ATRT and abemaciclib for CPC and DIPG. AUCs significantly decreased (P < 0.05) with increasing drug exposure time across all inhibitors. 7-day intraventricular palbociclib infusion was equivalent in safety to PBS at doses ranging from 1,000 to 10,000-fold the in vitro GI50. CONCLUSIONS: The efficiency of CDK4/6 inhibitors in pediatric CNS tumors is enhanced with prolonged exposure. Long-term IT administration can achieve high CNS doses without associated systemic toxicities. Translational efforts using a metronomic IT strategy are logical to explore for pediatric CNS tumors which have potential for a leptomeningeal disease pattern.

Pharmacogenomics of cisplatin-induced neurotoxicities: Hearing loss, tinnitus and peripheral sensory neuropathy.

12004 Background: Cisplatin is an essential component of first-line chemotherapy for many cancers, but causes neurotoxicity, including hearing loss (CisHL), tinnitus (CisTinn), and peripheral sensory neuropathy (CisPNeuro). However, few opportunities exist to identify risk factors and comorbidities for cisplatin-induced neurotoxicities among large numbers of homogenously treated patients without the confounding effect of cranial radiotherapy. Methods: Within a well-characterized clinical cohort of 1,680 cisplatin-treated testicular cancer survivors, linear and logistic regression analysis were utilized to analyze associations of CisHL (n = 1,258), CisTinn (n = 1,217), and CisPNeuro (n = 1,653) with non-genetic risk factors. Genome-wide association studies and gene-based analysis were performed on each phenotype. Results: Cisplatin-induced neurotoxicities (CisHL CisTinn, CisPNeuro), adjusting for age and cisplatin dose, were interdependent. Survivors with these neurotoxicities experienced more hypertension (CisTinn: OR = 2.62, p &lt; 0.0001; CisHL: β = 0.25, p = 8.5 x10-4; CisPNeuro: OR = 1.86, p &lt; 0.0001) and were more likely to report their health as poor (CisTinn: OR = 0.54, p &lt; 0.0001; CisHL: β = -0.11, p &lt; 0.0001; CisPNeuro: OR = 0.61, p &lt; 0.0001). Persistent vertigo was significantly associated with both CisTinn (OR = 7.18, p &lt; 0.0001) and CisPNeuro (OR = 4.29, p &lt; 0.0001). In addition, CisTinn was significantly associated with hypercholesterolemia (OR = 1.78, p = 0.01). Importantly, gene-based association analyses identified significant associations between CisTinn and WNT8A (n = 1,037, p = 2.52x10-6) , encoding a signaling protein important in germ cell tumors; and marginal significance between CisHL and TXNRD1 (n = 1,071, p = 4.21x10-6) , thioredoxin reductase-1, which plays a key role in redox regulation. In silico analysis showed high expression levels of TXNRD1 were significantly correlated with cellular resistance to cisplatin in central nervous system tumor cells (Spearman Rho = 0.35, p = 0.04; R2= 0.14, p = 0.03), indicating TXNRD1 is protective for cisplatin-induced cytotoxicity. Previously, rs62283056 in WFS1 found to be significantly associated with CisHL (n = 511; subset of current population), was marginally significant in an independent replication cohort (p = 0.06; n = 606; subset of current population). Conclusions: Cisplatin-induced neurotoxicities are significantly associated with multiple clinical characteristics, including hypertension and self-reported poor health. WNT8A and TXNRD1 are notable risk factors for CisTinn and CisHL, respectively . Future studies should further investigate these genes and their potential impact on chemotherapy strategies. This study, based on the largest number of testicular cancer survivors investigated to date, highlights the clinical importance of these iatrogenic toxicities and their associated risk factors.

BIOM-57. PEDIATRIC TUMOR CLASSIFICATION THROUGH GENOME-WIDE METHYLATION PROFILING OF EXTRACELLULAR VESICLE DNA

Abstract BACKGROUND Genome-wide methylation profiling reliably classifies pediatric central nervous system (CNS) tumors. Extracellular vesicles (EVs) are released by pediatric CNS tumor cells (pCC) and contain high molecular weight tumor DNA, rendering EVs a potential biomarker source to identify tumor subgroups, stratify patients and monitor therapy by liquid biopsy. We investigated whether the DNA in pCC-derived EVs reflects genome-wide tumor methylation profiles and allows tumor subtype classification. METHODS DNA was isolated from EVs secreted by pediatric CNS tumor cells (pCC) as well as from the shortly cultured tumor cells and from the original tumor samples (n=4 patients). Pediatric Fibroblasts and EVs derived thereof were used as a non-tumorous control. EVs were classified by nanoparticle analysis (NTA), immunoblotting, imaging flow cytometry (IFCM and electron microscopy. Genome-wide DNA methylation profiling was performed using an 850k Illumina EPIC array and results were classified according to the DKFZ brain tumor classifier and further analysed by t-SNE and Copy number alteration analysis (CNA). RESULTS The size range of pCC-derived EVs was 120–150 nm, as measured by NTA. The majority of secreted EVs exhibited high expression of common EV markers (i.e. CD9, CD63 and CD81), as characterized by IFCM. Genome-wide DNA methylation profiling of pCC-derived EVs correctly identified the methylation class of the original tumor (i.e. pilocytic astrocytoma, medulloblastoma). In addition, t-SNE analysis and copy number alterations matched the pattern of the parental pCC and original tumor samples. CONCLUSION EV DNA faithfully reflects the tumor methylation class and copy number alterations present in the parental cells and the original tumor. Methylation profiling of circulating tumor EV DNA could become a useful tool to detect and classify pediatric CNS tumors.

Exosomes and exosomal microRNA in non-targeted radiation bystander and abscopal effects in the central nervous system.

Localized cranial radiotherapy is a dominant treatment for brain cancers. After being subjected to radiation, the central nervous system (CNS) exhibits targeted effects as well as non-targeted radiation bystander effects (RIBE) and abscopal effects (RIAE). Radiation-induced targeted effects in the CNS include autophagy and various changes in tumor cells due to radiation sensitivity, which can be regulated by microRNAs. Non-targeted radiation effects are mainly induced by gap junctional communication between cells, exosomes containing microRNAs can be transduced by intracellular endocytosis to regulate RIBE and RIAE. In this review, we discuss the involvement of microRNAs in radiation-induced targeted effects, as well as exosomes and/or exosomal microRNAs in non-targeted radiation effects in the CNS. As a target pathway, we also discuss the Akt pathway which is regulated by microRNAs, exosomes, and/or exosomal microRNAs in radiation-induced targeted effects and RIBE in CNS tumor cells. As the CNS-derived exosomes can cross the blood-brain-barrier (BBB) into the bloodstream and be isolated from peripheral blood, exosomes and exosomal microRNAs can emerge as promising minimally invasive biomarkers and therapeutic targets for radiation-induced targeted and non-targeted effects in the CNS.

GENE-22. GENOME-WIDE METHYLATION PROFILING OF GLIOBLASTOMA EXTRACELLULAR VESICLE DNA ALLOWS TUMOR CLASSIFICATION

Abstract BACKGROUND Genome-wide methylation profiling has recently been developed into a tool that allows subtype tumor classification in central nervous system (CNS) tumors. Extracellular vesicles (EVs) are released by CNS tumor cells and contain high molecular weight tumor DNA, rendering EVs a potential biomarker source to identify tumor subgroups, stratify patients and monitor therapy by liquid biopsy. We investigated whether the DNA in glioma-derived EVs reflects genome-wide tumor methylation profiles and allows tumor subtype classification. METHODS DNA was isolated from EVs secreted by cultured glioma stem-like cells (GSC) as well as from the cells of origin and from the original tumor samples (n=3 patients). EVs were classified by nanoparticle analysis (NTA), immunoblotting, imaging flow cytometry (IFCM), multiplex EV assays and electron microscopy. Genome-wide DNA methylation profiling was performed using an 850k Illumina EPIC array and results were classified according to the DKFZ brain tumor classifier. RESULTS The size range of GSC-derived EVs was 120–150 nm, as measured by NTA. The majority of secreted EVs exhibited high expression of common EV markers (i.e. CD9, CD63 and CD81), as characterized by IFCM and multiplex EV assays. Genome-wide methylation profiling of GSC-derived EVs correctly identified the methylation class of the original tumor, including information on the IDH mutation status and subclass classification (RTK1, RTK2). In addition, copy number alterations and the MGMT metyhlation status matched the pattern of the parental GSCs and original tumor samples. CONCLUSION EV DNA faithfully reflects the tumor methylation class as well as the MGMT methylation status and copy number variations present in the parental cells and the original tumor. Methylation profiling of circulating tumor EV DNA could become a useful tool to detect and classify CNS tumors.

MiR-367 as a therapeutic target in stem-like cells from embryonal central nervous system tumors.

Aberrant expression of the pluripotency factor OCT4A in embryonal tumors of the central nervous system (CNS) is a key factor that contributes to tumor aggressiveness and correlates with poor patient survival. OCT4A overexpression has been shown to up‐regulate miR‐367, a microRNA (miRNA) that regulates pluripotency in embryonic stem cells and stem‐like aggressive traits in cancer cells. Here, we show that (a) miR‐367 is carried in microvesicles derived from embryonal CNS tumor cells expressing OCT4A; and (b) inhibition of miR‐367 in these cells attenuates their aggressive traits. miR‐367 silencing in OCT4A‐overexpressing tumor cells significantly reduced their proliferative and invasive behavior, clonogenic activity, and tumorsphere generation capability. In vivo, targeting of miR‐367 through direct injections of a specific inhibitor into the cerebrospinal fluid of Balb/C nude mice bearing OCT4A‐overexpressing tumor xenografts inhibited tumor development and improved overall survival. miR‐367 was also shown to target SUZ12, one of the core components of the polycomb repressive complex 2 known to be involved in epigenetic silencing of pluripotency‐related genes, including POU5F1, which encodes OCT4A. Our findings reveal possible clinical applications of a cancer stemness pathway, highlighting miR‐367 as a putative liquid biopsy biomarker that could be further explored to improve early diagnosis and prognosis prediction, and potentially serve as a therapeutic target in aggressive embryonal CNS tumors.

Zika Virus Selectively Kills Aggressive Human Embryonal CNS Tumor Cells In Vitro and In Vivo.

Zika virus (ZIKV) is largely known for causing brain abnormalities due to its ability to infect neural progenitor stem cells during early development. Here, we show that ZIKV is also capable of infecting and destroying stem-like cancer cells from aggressive human embryonal tumors of the central nervous system (CNS). When evaluating the oncolytic properties of Brazilian Zika virus strain (ZIKVBR) against human breast, prostate, colorectal, and embryonal CNS tumor cell lines, we verified a selective infection of CNS tumor cells followed by massive tumor cell death. ZIKVBR was more efficient in destroying embryonal CNS tumorspheres than normal stem cell neurospheres. A single intracerebroventricular injection of ZIKVBR in BALB/c nude mice bearing orthotopic human embryonal CNS tumor xenografts resulted in a significantly longer survival, decreased tumor burden, fewer metastasis, and complete remission in some animals. Tumor cells closely resembling neural stem cells at the molecular level with activated Wnt signaling were more susceptible to the oncolytic effects of ZIKVBR Furthermore, modulation of Wnt signaling pathway significantly affected ZIKVBR-induced tumor cell death and viral shedding. Altogether, these preclinical findings indicate that ZIKVBR could be an efficient agent to treat aggressive forms of embryonal CNS tumors and could provide mechanistic insights regarding its oncolytic effects.Significance: Brazilian Zika virus strain kills aggressive metastatic forms of human CNS tumors and could be a potential oncolytic agent for cancer therapy. Cancer Res; 78(12); 3363-74. ©2018 AACR.

Extracranial metastasis of gliobastoma: Three illustrative cases and current review of the molecular pathology and management strategies

Glioblastoma (GBM) is the most common and the most malignant primary brain tumor in adults, accounting for ~12-15% of all intracranial neoplasms. Despite advances in surgical, medical and radiation therapies, the mortality of GBM remains high, with a median survival ranging between 40 and 70 weeks. Similar to other primary brain tumors, the extracranial metastasis of GBM is extremely rare, occurring in <2% of patients. To demonstrate the clinical characteristics of this rare tumor, we herein present three cases of extracranial GBM metastasis: One to the lungs, which represents the longest reported survival of lung metastases from GBM to date; the second to the soft tissue of the posterior neck; and the third to the lumbar intradural space. Unlike tumors elsewhere, there are unique barriers in the brain that prevent the hematogenous and lymphatic spread of intracranial tumors, such as the dura mater and the thickened basement membrane of the blood vessels. In addition, central nervous system tumor cells lack extracellular matrix proteins required to invade surrounding connective tissue, a prerequisite for tumor dissemination. In this study, we aimed to investigate the different possible mechanisms underlying the extracranial metastasis of GBM and determine the biomolecular and genetic characteristics differentiating GBMs that metastasize from those that do not. We also reviewed the role of systemic chemotherapy and bevacizumab in the treatment of disseminated GBMs. Early identification and differentiation of these tumors may enable patients to benefit from surgical resection, radiation and combination chemotherapy prior to developing other comorbidities from metastatic disease, which may translate into prolonged survival with an acceptable quality of life.

Molecular pathology and targeted therapy of common tumors in central nervous system

It is difficult to cure central nervous system tumors using traditional method, due to chemotherapy drugs lack of specificity. They kill the tumor cells, and damage normal tissues and organs at the same time. The latest hotspot is targeted therapy on the specific molecules in the molecular pathway of central nervous system tumor cells. This review introduces the relationship between molecularly biological characteristics of medulloblastoma, oligodendrocytoma, glioblastoma and the prognosis in the view of critical intracellular pathway and genetic mutation. Furthermore, it reviews the current situation and progress of targeted therapy of tumors. As a consequence, it offers some new information for the individualized therapy of central nervous system tumors. doi: 10.3969/j.issn.1672-6731.2014.12.017

Using BRAFV600E as a marker of autophagy dependence in pediatric brain tumors

Autophagy inhibition is a potential therapeutic strategy in central nervous system (CNS) tumors. The BRAFV600E mutation is known to affect autophagy. Our studies indicate CNS tumor cells with BRAFV600E mutant cells (but not wild type) display high rates of induced autophagy, are sensitive to autophagy inhibition, and display synergy when chloroquine is combined with the RAF kinase inhibitor vemurafenib or standard chemotherapeutics. Our studies also indicate chloroquine can improve vemurafenib sensitivity in intrinsically resistant cells and in a patient with induced-vemurafenib resistance. These findings suggest CNS tumors with BRAFV600E are autophagy-dependent and that identification of BRAFV600E may be a marker to identify pediatric patients with the best potential response to autophagy inhibition.

Autophagy inhibition improves chemosensitivity in BRAF(V600E) brain tumors.

Autophagy inhibition is a potential therapeutic strategy in cancer, but it is unknown which tumors will benefit. The BRAF(V600E) mutation has been identified as important in pediatric central nervous system (CNS) tumors and is known to affect autophagy in other tumor types. We evaluated CNS tumor cells with BRAF(V600E) and found that mutant (but not wild-type) cells display high rates of induced autophagy, are sensitive to pharmacologic and genetic autophagy inhibition, and display synergy when the clinically used autophagy inhibitor chloroquine was combined with the RAF inhibitor vemurafenib or standard chemotherapeutics. Importantly, we also demonstrate that chloroquine can improve vemurafenib sensitivity in a resistant ex vivo primary culture and provide the first demonstration in a patient harboring the V600E mutation treated with vemurafenib that the addition of chloroquine can improve clinical outcomes. These findings suggest that CNS tumors with BRAF(V600E) are autophagy-dependent and should be targeted with autophagy inhibition in combination with other therapeutic strategies. Autophagy inhibition may improve cancer therapy, but it is unclear which tumors will benefit. We found that BRAF mutations cause brain tumor cells to depend on autophagy and display selective chemosensitization with autophagy inhibition. We present a pediatric case in which deliberate autophagy inhibition halted tumor growth and overcame acquired BRAF-inhibition resistance.

Immunopathology of Central Nervous System Tumors

The central nervous system (CNS) is characterized by unique immune biology. Distinct mechanisms of CNS immune surveillance and activation have important implications in tumor development as CNS tumors are known to evade anti-tumoral immunity, and may also contribute to immunosuppression. Multiple cell-surface and secreted mediators, expressed in both CNS tumor cells and responding immune cells, have been shown to influence the immune response to CNS tumors. In this review we provide an overview of CNS tumor immune escape and immunosuppression, highlighting the cellular and molecular features associated with both CNS tumors cells and responding immune cells. In this context, we discuss of the role of the M1 and M2 tumor associated macrophage phenotypes, myeloid derived suppressor cells, regulatory T-cells, as well as many immunomodulatory cytokines. Additionally, recent insights into the STAT-3 intracellular signaling pathway and the presence of active human CMV infection in the context of CNS tumor development are discussed.

In vivo intracellular oxygen dynamics in murine brain glioma and immunotherapeutic response of cytotoxic T cells observed by fluorine-19 magnetic resonance imaging.

Noninvasive biomarkers of anti-tumoral efficacy are of great importance to the development of therapeutic agents. Tumor oxygenation has been shown to be an important indicator of therapeutic response. We report the use of intracellular labeling of tumor cells with perfluorocarbon (PFC) molecules, combined with quantitative 19F spin-lattice relaxation rate (R1) measurements, to assay tumor cell oxygen dynamics in situ. In a murine central nervous system (CNS) GL261 glioma model, we visualized the impact of Pmel-1 cytotoxic T cell immunotherapy, delivered intravenously, on intracellular tumor oxygen levels. GL261 glioma cells were labeled ex vivo with PFC and inoculated into the mouse striatum. The R1 of 19F labeled cells was measured using localized single-voxel magnetic resonance spectroscopy, and the absolute intracellular partial pressure of oxygen (pO2) was ascertained. Three days after tumor implantation, mice were treated with 2×107 cytotoxic T cells intravenously. At day five, a transient spike in pO2 was observed indicating an influx of T cells into the CNS and putative tumor cell apoptosis. Immunohistochemistry and quantitative flow cytometry analysis confirmed that the pO2 was causally related to the T cells infiltration. Surprisingly, the pO2 spike was detected even though few (∼4×104) T cells actually ingress into the CNS and with minimal tumor shrinkage. These results indicate the high sensitivity of this approach and its utility as a non-invasive surrogate biomarker of anti-cancer immunotherapeutic response in preclinical models.

Lapatinib and Obatoclax Kill Tumor Cells through Blockade of ERBB1/3/4 and through Inhibition of BCL-xL and MCL-1

Prior studies in breast cancer cells have shown that lapatinib and obatoclax interact in a greater than additive fashion to cause cell death and do so through a toxic form of autophagy. The present studies sought to extend our analyses to the central nervous system (CNS) tumor cells and to further define mechanisms of drug action. Lapatinib and obatoclax killed multiple CNS tumor isolates. Cells lacking PTEN (phosphatase and tensin homolog on chromosome 10) function were relatively resistant to drug combination lethality; expression of PTEN in PTEN-null cells restored drug sensitivity, and knockdown of PTEN promoted drug resistance. On the basis of knockdown of ERBB1-4 (erythroblastic leukemia viral oncogene homolog 1-4), we discovered that the inhibition of ERBB1/3/4 receptors were most important for enhancing obatoclax lethality rather than ERBB2. In parallel, we noted in CNS tumor cells that knockdown of BCL-xL (B-cell lymphoma-extra large)and MCL-1 (myeloid cell leukemia-1) interacted in an additive fashion to facilitate lapatinib lethality. Pretreatment of tumor cells with obatoclax enhanced the lethality of lapatinib to a greater extent than concomitant treatment. Treatment of animals carrying orthotopic CNS tumor isolates with lapatinib- and obatoclax-prolonged survival. Altogether, our data show that lapatinib and obatoclax therapy could be of use in the treatment of tumors located in the CNS.

Expression of the Stem Cell Markers Nestin and CD133 on Circulating Melanoma Cells

Different molecular markers have been identified for melanoma-initiating cells including CD133 and nestin. Assuming that metastasis requires a dissemination of tumor-initiating cells, presence of circulating tumor-initiating cells should be associated with worse patient outcome. In this study, 20 ml blood was collected from 32 consecutive patients affected by metastatic melanoma and blood was enriched for circulating melanoma cells (CMCs) by CD45 depletion of the non-melanoma cell fraction. Multiparameter cytometry was carried out to co-stain with combinations of CD133 and nestin (NES). Six tissue samples from metastatic lesions of six different patients were stained with the same antibodies by immunohistochemistry. Percentage of NES-positive CMCs correlated with tumor burden and number of metastatic sites. Cox regression analysis revealed levels of lactate dehydrogenase (LDH; hazard ratio: 12.8 (1.35-121.5); P=0.02), number of metastatic sites (hazard ratio 3.87 (1.66-9.03); P=0.02), tumor burden (hazard ratio 5.72 (1.57-20.9); P=0.01), and percentage of NES-expressing CMCs ≥ 35% (hazard ratio 5.73 (1.66-19.7); P=0.006) to be factors related to shorter overall survival. CD133- and NES-expression profiles on CMCs were similar to matched metastatic tissue. These findings show that CMCs expressed stem cell-associated markers NES and CD133. Higher expression of NES on CMCs might represent an index of poor prognosis.