Akt activation is a common event in pediatric malignant gliomas and a potential adverse prognostic marker: a report from the Children's Oncology Group

LncRNA CAI2 Contributes to Poor Prognosis of Glioma through the PI3K-Akt Signaling Pathway

AIMS

We aim to explore new potential therapeutic targets and markers in human glioma.

BACKGROUND

Gliomas are the most common malignant primary tumor in the brain.

OBJECTIVE

In the present research, we evaluated the effect of CAI2, a long non-coding RNA, on the biological behaviors of glioma and explored the related molecular mechanism.

METHODS

The expression of CAI2 was analyzed using qRT-PCR in 65 cases of glioma patients. The cell proliferation was determined with MTT and colony formation assays, and the PI3K-AKt signaling pathway was analyzed using western blot.

RESULTS

CAI2 was upregulated in human glioma tissue compared with the matched, adjacent nontumor tissue and was correlated with WHO grade. Survival analyses proved that the overall survival of patients with high CAI2 expression was poor compared to that of patients with low CAI2 expression. High CAI2 expression was an independent prognostic factor in glioma. The absorbance values in the MTT assay after 96 h were .712 ± .031 for the si-control and .465 ± .018 for the si- CAI2-transfected cells, and si-CAI2 inhibited colony formation in U251 cells by approximately 80%. The levels of PI3K, p-AKt, and AKt in si-CAI2-treated cells were decreased.

CONCLUSION

CAI2 may promote glioma growth through the PI3K-AKt signaling pathway. This research provided a novel potential diagnostic marker for human glioma.

Vorinostat, temozolomide or bevacizumab with irradiation and maintenance BEV/TMZ in pediatric high-grade glioma: A Children's Oncology Group Study

Background

Outcomes for children with high-grade gliomas (HGG) remain poor. This multicenter phase II trial evaluated whether concurrent use of vorinostat or bevacizumab with focal radiotherapy (RT) improved 1-year event-free survival (EFS) compared to temozolomide in children with newly diagnosed HGG who received maintenance temozolomide and bevacizumab.

Methods

Patients ≥ 3 and < 22 years with localized, non-brainstem HGG were randomized to receive RT (dose 54-59.4Gy) with vorinostat, temozolomide, or bevacizumab followed by 12 cycles of bevacizumab and temozolomide maintenance therapy.

Results

Among 90 patients randomized, the 1-year EFS for concurrent bevacizumab, vorinostat, or temozolomide with RT was 43.8% (±8.8%), 41.4% (±9.2%), and 59.3% (±9.5%), respectively, with no significant difference among treatment arms. Three- and five-year EFS for the entire cohort was 14.8% and 13.4%, respectively, with no significant EFS difference among the chemoradiotherapy arms. IDH mutations were associated with more favorable EFS (P = .03), whereas H3.3 K27M mutations (P = .0045) and alterations in PIK3CA or PTEN (P = .025) were associated with worse outcomes. Patients with telomerase- and alternative lengthening of telomeres (ALT)-negative tumors (n = 4) had an EFS of 100%, significantly greater than those with ALT or telomerase, or both (P = .002). While there was no difference in outcomes based on TERT expression, high TERC expression was associated with inferior survival independent of the telomere maintenance mechanism (P = .0012).

Conclusions

Chemoradiotherapy with vorinostat or bevacizumab is not superior to temozolomide in children with newly diagnosed HGG. Patients with telomerase- and ALT-negative tumors had higher EFS suggesting that, if reproduced, mechanism of telomere maintenance should be considered in molecular-risk stratification in future studies.

PI3K/AKT/mTOR signaling pathway activity in IDH-mutant diffuse glioma and clinical implications

BACKGROUND

IDH-mutant diffuse gliomas are heterogeneous, and improved methods for optimal patient therapeutic stratification are needed. PI3K/AKT/mTOR signaling activity can drive disease progression and potential therapeutic inhibitors of the pathway are available. Yet, the prevalence of PI3K/AKT/mTOR signaling pathway activity in IDH-mutant glioma is unclear and few robust strategies to assess activity in clinical samples exist.

METHODS

PI3K/AKT/mTOR signaling pathway activity was evaluated in a retrospective cohort of 132 IDH-mutant diffuse glioma (91 astrocytoma and 41 oligodendroglioma, 1p/19q-codeleted) through quantitative multiplex immunoprofiling using phospho-specific antibodies for PI3K/AKT/mTOR pathway members, PRAS40, RPS6, and 4EBP1, and tumor-specific anti-IDH1 R132H. Expression levels were correlated with genomic evaluation of pathway intrinsic genes and univariate and multivariate Cox proportional hazard regression models were used to evaluate the relationship with outcome.

RESULTS

Tumor-specific expression of p-PRAS40, p-RPS6, and p-4EBP1 was common in IDH-mutant diffuse glioma and increased with CNS WHO grade from 2 to 3. Genomic analysis predicted pathway activity in 21.7% (13/60) while protein evaluation identified active PI3K/AKT/mTOR signaling in 56.6% (34/60). Comparison of expression in male versus female patients suggested sexual dimorphism. Of particular interest, when adjusting for clinical prognostic factors, the level of phosphorylation of RPS6 was strongly associated with PFS (P < .005). Phosphorylation levels of both PRAS40 and RPS6 showed an association with PFS in univariate analysis.

CONCLUSIONS

Our study emphasizes the value of proteomic assessment of signaling pathway activity in tumors as a means to identify relevant oncogenic pathways and potentially as a biomarker for identifying aggressive disease.

An Overview of Conventional Drugs and Nanotherapeutic Options for the Treatment and Management of Pediatric Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is a common form of pediatric cancer affecting the lymphoblast, a type of white blood cell found in the bone marrow. In this disease, the normal lymphoblast cells transform into leukemic cells and subsequently enter the bloodstream. Leukemic cells found in patients with ALL have shown differences in cholesterol uptake and utilization. Current treatment consists of chemotherapy, chimeric antigen receptor (CAR) therapy, and hematopoietic stem cell transplantation (HSCT). In addition, minimal residual disease (MRD) has become an effective tool for measuring treatment efficacy and the potential for relapse. Chemotherapy resistance remains a significant barrier in the treatment of ALL. Biomarkers such as an upregulated Akt signaling pathway and an overexpressed VLA-4 integrin-protein have been associated with drug resistance. Nanoparticles have been used to favorably alter the pharmacokinetic profile of conventional drug agents. These drug-delivery systems are designed to selectively deliver their drug payloads to desired targets. Therefore, nanoparticles offer advantages such as improved efficacy and reduced toxicity. This review highlights conventional treatment options, distinctive characteristics of pediatric ALL, therapeutic challenges encountered during therapy, and the key role that nanotherapeutics play in the treatment of ALL.

A Phase I and Surgical Study of Ribociclib and Everolimus in Children with Recurrent or Refractory Malignant Brain Tumors: A Pediatric Brain Tumor Consortium Study

PURPOSE

Genomic aberrations in cell cycle and PI3K pathways are commonly observed in pediatric brain tumors. This study determined the MTD/recommended phase II dose (RP2D) of ribociclib and everolimus and characterized single-agent ribociclib concentrations in plasma and tumor in children undergoing resection.

PATIENTS AND METHODS

Patients were enrolled in the phase I study according to a rolling 6 design and received ribociclib and everolimus daily for 21 and 28 days, respectively. Surgical patients received ribociclib at the pediatric RP2D (350 mg/m2) for 7-10 days preoperatively followed by enrollment on the phase I study. Pharmacokinetics were analyzed for both cohorts.

RESULTS

Sixteen patients were enrolled on the phase I study (median age, 10.3 years; range, 3.9-20.4) and 6 patients in the surgical cohort (median age, 11.4 years; range: 7.2-17.1). Thirteen patients were enrolled at dose level 1 without dose-limiting toxicities (DLT). Two of the 3 patients at dose level 2 experienced DLTs (grade 3 hypertension and grade 4 alanine aminotransferase). The most common grade 3/4 toxicities were lymphopenia, neutropenia, and leukopenia. The RP2D of ribociclib and everolimus was 120 and 1.2 mg/m2 for 21 and 28 days, respectively. Steady-state everolimus exposures with ribociclib were 2.5-fold higher than everolimus administered alone. Ribociclib plasma, tumor concentrations, and cerebrospinal fluid (CSF) samples were collected. The mean tumor-to-plasma ratio of ribociclib was 19.8 (range, 2.22-53.4).

CONCLUSIONS

Ribociclib and everolimus were well-tolerated and demonstrated pharmacokinetic properties similar to those in adults. Potential therapeutic ribociclib concentrations could be achieved in CSF and tumor tissue, although interpatient variability was observed.

Multicentric glioblastoma in a 4-year-old female patient: A case report

In the USA and Germany, pediatric glioblastoma (pGBM) makes up <3% of childhood brain tumors. Occasionally, GBM has multiple contrast lesions and is referred to as multicentric GBM. The current study present a case of a four-year-old female patient presented with headache, vomiting and consciousness disturbance. Radiologically, a neoplastic lesion of the right frontal lobe with hemorrhage, and bilateral thalamus, right temporal and left occipital neoplastic lesions were identified. The right frontal lesion was not continuous to other lesions. It was concluded that the tumor was a multicentric GBM with intra-tumoral hemorrhage. The tumor was pathologically GBM. Following surgery, the patient underwent chemotherapy and radiotherapy, but 11 months after surgery, the patient passed away. This case had features of childhood GBM and multicentric GBM and was difficult to treat.

Pulvinar Locus is Highly Relevant to Patients' Outcomes in Surgically Resected Thalamic Gliomas in Children

OBJECTIVE

Thalamic gliomas in children are less suitable for surgical resection because of their location. In cases of unavoidable resection, careful surgical planning in addition to histology and extent of resection affects prognosis.

METHODS

A cohort of 10 pediatric patients with thalamic glioma underwent surgical resection at our department. The predominant location of tumor origins in the thalamus was defined in imaging studies. Histopathology was determined (retrospectively in a subset) according to the World Health Organization classification 2016, including the newly established type of "diffuse midline glioma, H3 K27M-mutant."

RESULTS

Three low-grade gliomas (grade I/II) and 7 high-grade gliomas (grade III/IV) were identified. The mean follow-up period was 49.8 months. All 3 low-grade gliomas did not recur (progression-free survival, 58.3 months). Six of 7 high-grade gliomas recurred, and the patients died of the primary disease (overall survival, 28.1 months). Poor outcomes, especially when located at the pulvinar region, were noticeable, with strong predictive power for poor prognosis (P = 0.0018). The presence of H3 K27M mutation and pulvinar location were closely associated (P = 0.0036). Four of 5 patients with pulvinar region tumors developed dissemination and died of the primary disease.

CONCLUSIONS

Pulvinar location is specifically associated with a high rate of malignancy in histology, the presence of H3 K27M mutation, and dissemination at an early disease stage. This association suggests that a distinct biological profile affects prognosis depending on location within the thalamus, especially the pulvinar. We report that tumor location is highly relevant to prognosis and should be taken into consideration when planning treatment.

Molecular, Pathological, Radiological, and Immune Profiling of Non-brainstem Pediatric High-Grade Glioma from the HERBY Phase II Randomized Trial

The HERBY trial was a phase II open-label, randomized, multicenter trial evaluating bevacizumab (BEV) in addition to temozolomide/radiotherapy in patients with newly diagnosed non-brainstem high-grade glioma (HGG) between the ages of 3 and 18 years. We carried out comprehensive molecular analysis integrated with pathology, radiology, and immune profiling. In post-hoc subgroup analysis, hypermutator tumors (mismatch repair deficiency and somatic POLE/POLD1 mutations) and those biologically resembling pleomorphic xanthoastrocytoma ([PXA]-like, driven by BRAF_V600E or NF1 mutation) had significantly more CD8+ tumor-infiltrating lymphocytes, and longer survival with the addition of BEV. Histone H3 subgroups (hemispheric G34R/V and midline K27M) had a worse outcome and were immune cold. Future clinical trials will need to take into account the diversity represented by the term "HGG" in the pediatric population.

The therapeutic potential of targeting the PI3K pathway in pediatric brain tumors

Central nervous system tumors are the most common cancer type in children and the leading cause of cancer related deaths. There is therefore a need to develop novel treatments. Large scale profiling studies have begun to identify alterations that could be targeted therapeutically, including the phosphoinositide 3-kinase (PI3K) signaling pathway, which is one of the most commonly activated pathways in cancer with many inhibitors under clinical development. PI3K signaling has been shown to be aberrantly activated in many pediatric CNS neoplasms. Pre-clinical analysis supports a role for PI3K signaling in the control of tumor growth, survival and migration as well as enhancing the cytotoxic effects of current treatments. Based on this evidence agents targeting PI3K signaling have begun to be tested in clinical trials of pediatric cancer patients. Overall, targeting the PI3K pathway presents as a promising strategy for the treatment of pediatric CNS tumors. In this review we examine the genetic alterations found in the PI3K pathway in pediatric CNS tumors and the pathological role it plays, as well as summarizing the current pre-clinical and clinical data supporting the use of PI3K pathway inhibitors for the treatment of these tumors.

Patient and treatment factors associated with survival among pediatric glioblastoma patients: A Surveillance, Epidemiology, and End Results study

Glioblastoma (GBM) is a rare malignancy in children. The United States Surveillance, Epidemiology, and End Results (SEER) database allows large-scale analyses of clinical characteristics and prognostic features. We used it to study patients aged <20 years with histologically confirmed GBM (2000-2010) and examined the relationship between patient demographics, tumor characteristics, patterns of treatment, and outcomes. The primary outcome was disease-specific survival. 302 subjects were identified, with median age 11 years. Median follow-up was 32 months (95% CI 27-39). 34.4% had gross total resection (GTR). 61% underwent radiation after surgery (17% of subjects <3 years, 67% of those aged 4-19 years). Median survival and 2-year survival rates were 20 months and 46.9%, respectively. In multivariate analyses, age, tumor location, extent of resection, and year of diagnosis were significantly associated with the primary outcome. Compared to those aged 0-4 years, subjects aged 5-9 years and 10-14 years had higher risk of mortality. Infratentorial tumor location (HR 2.0, 95% CI 1.2-3.3, p = 0.007) and subtotal resection (HR 2.04, 95% CI 1.4-3.0, p < 0.001) were associated with increased mortality. Later year of diagnosis was significantly associated with decreased risk of death (HR 0.93, 95% CI 0.9-0.99, p = 0.031). There was no association between sex, race, region, or tumor size and the primary outcome. Repeat analyses examining all-cause mortality identified the same risk factors as for CNS cancer-specific mortality. Younger age, supratentorial location, GTR, and later year of diagnosis were associated with improved survival.

Recent perspectives of molecular aberrations in pediatric high-grade glioma

Pediatric high-grade glioma (HGG), including diffuse intrinsic pontine glioma (DIPG) are highly aggressive tumors with no effective cures. Lack of understanding of the molecular biology of these tumors, in part due to lack of well-characterized pre-clinical models, is a great challenge in the development of novel therapies. Recent studies have shown that pediatric HGG short-term cell cultures retain many of the tumor characteristics in vivo and at present one of the best choices for in-vivo experimental studies. The present review article would put light on novel genetic and epigenetic changes in pediatric HGG that might, act as a gold standard potential biomarkers and/or therapeutic targets in near future.

A phase I study of single-agent perifosine for recurrent or refractory pediatric CNS and solid tumors

The PI3K/Akt/mTOR signaling pathway is aberrantly activated in various pediatric tumors. We conducted a phase I study of the Akt inhibitor perifosine in patients with recurrent/refractory pediatric CNS and solid tumors. This was a standard 3+3 open-label dose-escalation study to assess pharmacokinetics, describe toxicities, and identify the MTD for single-agent perifosine. Five dose levels were investigated, ranging from 25 to 125 mg/m2/day for 28 days per cycle. Twenty-three patients (median age 10 years, range 4-18 years) with CNS tumors (DIPG [n = 3], high-grade glioma [n = 5], medulloblastoma [n = 2], ependymoma [n = 3]), neuroblastoma (n = 8), Wilms tumor (n = 1), and Ewing sarcoma (n = 1) were treated. Only one DLT occurred (grade 4 hyperuricemia at dose level 4). The most common grade 3 or 4 toxicity at least possibly related to perifosine was neutropenia (8.7%), with the remaining grade 3 or 4 toxicities (fatigue, hyperglycemia, fever, hyperuricemia, and catheter-related infection) occurring in one patient each. Pharmacokinetics was dose-saturable at doses above 50 mg/m2/day with significant inter-patient variability, consistent with findings reported in adult studies. One patient with DIPG (dose level 5) and 4 of 5 patients with high-grade glioma (dose levels 2 and 3) experienced stable disease for two months. Five subjects with neuroblastoma (dose levels 1 through 4) achieved stable disease which was prolonged (≥11 months) in three. No objective responses were noted. In conclusion, the use of perifosine was safe and feasible in patients with recurrent/refractory pediatric CNS and solid tumors. An MTD was not defined by the 5 dose levels investigated. Our RP2D is 50 mg/m2/day.

Pediatric high-grade glioma: current molecular landscape and therapeutic approaches

High-grade pediatric central nervous system glial tumors are comprised primarily of anaplastic astrocytomas (AA, WHO grade III) and glioblastomas (GBM, WHO grade IV). High-grade gliomas are most commonly diagnosed in the primary setting in children, but as in adults, they can also arise as a result of transformation of a low-grade malignancy, though with limited frequency in the pediatric population. The molecular genetics of high-grade gliomas in the pediatric population are distinct from their adult counterparts. In contrast to the adult population, high-grade gliomas in children are relatively infrequent, representing less than 20% of cases.

Outcome of young children with high-grade glioma treated with irradiation-avoiding intensive chemotherapy regimens: Final report of the Head Start II and III trials

PURPOSE

To report the final analysis of survival outcomes for children with newly diagnosed high-grade glioma (HGG) treated on the "Head Start" (HS) II and III protocols with chemotherapy and intent to avoid irradiation in children <6 years old.

PATIENTS AND METHODS

Between 1997 and 2009, 32 eligible children were enrolled in HS II and III with anaplastic astrocytoma (AA, n = 19), glioblastoma multiforme (GBM, n = 11), or other HGG (n = 2). Central pathology review was completed on 78% of patients. Patients with predominantly brainstem tumors were excluded. Patients were to be treated with single induction chemotherapy regimen C, comprising four cycles of vincristine, carboplatin, and temozolomide. Following induction, patients underwent marrow-ablative chemotherapy and autologous hematopoietic cell rescue. Irradiation was used for patients with residual tumor after consolidation or >6 years old or at the time of tumor progression.

RESULTS

The 5-year event-free survival (EFS) and overall survival (OS) for all HGG patients were 25 ± 8% and 36 ± 9%, respectively. The EFS at 5 years for patients with AA and GBM were 24 ± 11% and 30 ± 16%, respectively (P = 0.65). The OS at 5 years for patients with AA and GBM was 34 ± 12% and 35 ± 16%, respectively (P = 0.83). Children <36 months old experienced improved 5-year EFS and OS of 44 ± 17% and 63 ± 17%, compared with children 36-71 months old (31 ± 13% and 38 ± 14%) and children >72 months old (0% and 13 ± 12%).

CONCLUSIONS

Irradiation-avoiding treatment strategies should be evaluated further in young children with HGG given similar survival rates to older children receiving standard irradiation-containing therapies.

Molecular Biology in Pediatric High-Grade Glioma: Impact on Prognosis and Treatment

High-grade gliomas are the main cause of death in children with brain tumours. Despite recent advances in cancer therapy, their prognosis remains poor and the treatment is still challenging. To date, surgery followed by radiotherapy and temozolomide is the standard therapy. However, increasing knowledge of glioma biology is starting to impact drug development towards targeted therapies. The identification of agents directed against molecular targets aims at going beyond the traditional therapeutic approach in order to develop a personalized therapy and improve the outcome of pediatric high-grade gliomas. In this paper, we critically review the literature regarding the genetic abnormalities implicated in the pathogenesis of pediatric malignant gliomas and the current development of molecularly targeted therapies. In particular, we analyse the impact of molecular biology on the prognosis and treatment of pediatric high-grade glioma, comparing it to that of adult gliomas.

Plasma and cerebrospinal fluid pharmacokinetics of the Akt inhibitor, perifosine, in a non-human primate model

PURPOSE

Central nervous system tumors are histologically and biologically heterogeneous. Standard treatment for malignant tumors includes surgery, radiation and chemotherapy, yet surgical resection is not always an option and chemotherapeutic agents have limited benefit. Recent investigations have focused on molecularly targeted therapies aimed at critical tumorigenic pathways. Several tumor types, including high-grade gliomas and pediatric pontine gliomas, exhibit Akt activation. Perifosine, an orally bioavailable, synthetic alkylphospholipid and potent Akt inhibitor, has demonstrated activity in some preclinical models, but absent activity in a genetically engineered mouse model of pontine glioma. We evaluated the plasma and cerebrospinal fluid pharmacokinetics of orally administered perifosine in a non-human primate model to evaluate CNS penetration.

METHODS

Perifosine was administered orally to three adult rhesus monkeys as a single dose of 7.0 mg/kg perifosine. Serial paired plasma and CSF samples were collected for up to 64 days. Perifosine was quantified with a validated HPLC/tandem mass spectrometry assay. Pharmacokinetic parameters were estimated using non-compartmental methods. CSF penetration was calculated from the areas under the concentration-time curves.

RESULTS

Peak plasma concentrations (C max) ranged from 11.7-19.3 µM, and remained >1 µM for >28 days. Time to C max (T max) was 19 h. The median (range) AUCPl was 3148 (2502-4705) µM/h, with a median (range) terminal half-life (t 1/2) of 193 (170-221) h. Plasma clearance was 494 (329-637) mL/h/kg. Peak CSF concentrations were 4.1-10.1 nM (T max 64-235 h). CSF AUCs and t 1/2 were 6358 (2266-7568) nM/h and 277 (146-350) h, respectively. Perifosine concentrations in the CSF remained over  nM for >35 days. The mean CSF penetration was 0.16 %.

CONCLUSION

CNS penetration of perifosine after systemic administration is poor. However, levels were measurable in both plasma and CSF for an extended time (>2 months) after a single oral dose.

Impact of tumor location and pathological discordance on survival of children with midline high-grade gliomas treated on Children's Cancer Group high-grade glioma study CCG-945

Children with high-grade glioma (HGG) have a poor prognosis compared to those with low-grade glioma (LGG). Adjuvant chemotherapy may be beneficial, but its optimal use remains undetermined. Histology and extent of resection are important prognostic factors. We tested the hypothesis that patients with midline HGG treated on Children's Cancer Group Study (CCG) CCG-945 have a worse prognosis compared to the entire group. Of 172 children eligible for analysis, 60 had midline tumors primarily localized to the thalamus, hypothalamus and basal ganglia. Time-to-progression and death were determined from the date of initial diagnosis, and survival curves were calculated. Univariate analyses were undertaken for extent of resection, chemotherapy regimen, anatomic location, histology, proliferation index, MGMT status and p53 over-expression. For the entire midline tumor group, 5-year PFS and OS were 18.3 ± 4.8 and 25 ± 5.4 %, respectively. Many patients only had a biopsy (43.3 %). The sub-groups with near/total resection and hypothalamic location appeared to have better PFS and OS. However, the effect of tumor histology on OS was significant for children with discordant diagnoses on central pathology review of LGG compared to HGG. Proliferative index (MIB-1 > 36 %), MGMT and p53 over-expression correlated with poor outcomes. Children treated on CCG-945 with midline HGG have a worse prognosis when compared to the entire group. The midline location may directly influence the extent of resection. Central pathology review and entry of patients on clinical trials continue to be priorities to improve outcomes for children with HGG.

Prognostic and predictive biomarkers in adult and pediatric gliomas: toward personalized treatment

It is increasingly clear that both adult and pediatric glial tumor entities represent collections of neoplastic lesions, each with individual pathological molecular events and treatment responses. In this review, we discuss the current prognostic biomarkers validated for clinical use or with future clinical validity for gliomas. Accurate prognostication is crucial for managing patients as treatments may be associated with high morbidity and the benefits of high risk interventions must be judged by the treating clinicians. We also review biomarkers with predictive validity, which may become clinically relevant with the development of targeted therapies for adult and pediatric gliomas.

Isoform level expression profiles provide better cancer signatures than gene level expression profiles

BACKGROUND

The majority of mammalian genes generate multiple transcript variants and protein isoforms through alternative transcription and/or alternative splicing, and the dynamic changes at the transcript/isoform level between non-oncogenic and cancer cells remain largely unexplored. We hypothesized that isoform level expression profiles would be better than gene level expression profiles at discriminating between non-oncogenic and cancer cellsgene level.

METHODS

We analyzed 160 Affymetrix exon-array datasets, comprising cell lines of non-oncogenic or oncogenic tissue origins. We obtained the transcript-level and gene level expression estimates, and used unsupervised and supervised clustering algorithms to study the profile similarity between the samples at both gene and isoform levels.

RESULTS

Hierarchical clustering, based on isoform level expressions, effectively grouped the non-oncogenic and oncogenic cell lines with a virtually perfect homogeneity-grouping rate (97.5%), regardless of the tissue origin of the cell lines. However, gene levelthis rate was much lower, being 75% at best based on the gene level expressions. Statistical analyses of the difference between cancer and non-oncogenic samples identified the existence of numerous genes with differentially expressed isoforms, which otherwise were not significant at the gene level. We also found that canonical pathways of protein ubiquitination, purine metabolism, and breast-cancer regulation by stathmin1 were significantly enriched among genes thatshow differential expression at isoform level but not at gene level.

CONCLUSIONS

In summary, cancer cell lines, regardless of their tissue of origin, can be effectively discriminated from non-cancer cell lines at isoform level, but not at gene level. This study suggests the existence of an isoform signature, rather than a gene signature, which could be used to distinguish cancer cells from normal cells.

Molecular diagnostics in paediatric glial tumours

Glial tumours in children have distinct patterns of epigenetic alteration, chromosomal structure, and gene and protein expression that differentiate them from their histological counterparts in adults. Understanding paediatric gliomas at the molecular level provides important prognostic and therapeutic insights, such as which genetic alterations confer a favourable response to adjuvant therapy, or which signalling pathways might be amenable to specific molecularly targeted agents. For clinicians, the ultimate goal is to individualise therapeutic regimens on the basis of the molecular fingerprint of a particular tumour and the prognosis conferred by this profile. In this Review, we examine a series of studies of molecular and genomic analysis of glial tumours in children, and discuss the many clinical insights that these molecular features provide.

Pediatric glioma stem cells: biologic strategies for oncolytic HSV virotherapy

While glioblastoma multiforme (GBM) is the most common adult malignant brain tumor, GBMs in childhood represent less than 10% of pediatric malignant brain tumors and are phenotypically and molecularly distinct from adult GBMs. Similar to adult patients, outcomes for children with high-grade gliomas (HGGs) remain poor. Furthermore, the significant morbidity and mortality yielded by pediatric GBM is compounded by neurotoxicity for the developing brain caused by current therapies. Poor outcomes have been attributed to a subpopulation of chemotherapy and radiotherapy resistant cells, termed “glioma stem cells” (GSCs), “glioma progenitor cells,” or “glioma-initiating cells,” which have the ability to initiate and maintain the tumor and to repopulate the recurring tumor after conventional therapy. Future innovative therapies for pediatric HGG must be able to eradicate these therapy-resistant GSCs. Oncolytic herpes simplex viruses (oHSV), genetically engineered to be safe for normal cells and to express diverse foreign anti-tumor therapeutic genes, have been demonstrated in preclinical studies to infect and kill GSCs and tumor cells equally while sparing normal brain cells. In this review, we discuss the unique aspects of pediatric GSCs, including markers to identify them, the microenvironment they reside in, signaling pathways that regulate them, mechanisms of cellular resistance, and approaches to target GSCs, with a focus on the promising therapeutic, genetically engineered oHSV.

Harmine hydrochloride inhibits Akt phosphorylation and depletes the pool of cancer stem-like cells of glioblastoma

Harmine hydrochloride (Har-hc), a derivative from Harmine which is a natural extractive from plants, has been considered for treatment of kinds of cancers and cerebral diseases. In this study, we found that Har-hc clearly decreased cell viability, induced apoptosis and inhibited Akt phosphorylation in glioblastoma cell lines. Moreover, Har-hc had the ability to inhibit self-renewal and promote differentiation of glioblastoma stem like cells (GSLCs) accompanied by inhibition of Akt phosphorylation. Especially, we demonstrated that Har-hc inhibited neurosphere formation of human primary GSLCs. In vivo test also confirmed Har-hc decreased the tumorigenicity of GSLCs. Thus we conclude that Har-hc has potent anti-cancer effects in glioblastoma cells, which is at least partially via inhibition of Akt phosphorylation. Administration of Har-hc may act as a new approach to glioblastoma treatment.

PTEN promoter methylation and activation of the PI3K/Akt/mTOR pathway in pediatric gliomas and influence on clinical outcome

The signaling pathways that underlie the pathogenesis of pediatric gliomas are poorly understood. We characterized the PI3K/Akt/mTOR pathway in pediatric gliomas of all grades. Using immunohistochemistry, we assessed activation of the PI3K/Akt/mTOR pathway by evaluating the downstream signaling molecules phospho(p)-S6, phospho(p)-4BP1, and phospho(p)-PRAS40; PTEN; and PTEN promoter methylation, as well as the MIB labeling index. We correlated these findings with the clinical outcomes of 48 children with gliomas. Eighty percent of high-grade gliomas (12/15) showed activation of the PI3K/Akt/mTOR pathway based on p-S6 and p-4EBP1 expression. The majority of high-grade gliomas were negative for PTEN expression (10/15), and 50% had PTEN promoter methylation (grade III: 2/4; grade IV: 3/6). Low-grade gliomas demonstrated PI3K/Akt/mTOR pathway activation in 14/32 (43.8%) by p-S6 and 16/32 (50%) by p-4EBP1. Over 50% of grade I (6/11) and almost all grade II tumors (6/7) showed PTEN promoter methylation. Tumor grade correlated negatively with PTEN expression and positively with expression of p-S6 and p-4EBP1 (PTEN: P = .0025; pS6: P = .0075; p-4EBP1: P = .0066). There was a trend toward inverse correlation of methylation of the PTEN promoter with expression of PTEN protein (P= .0990) and direct correlation of expression of p-S6 and p-4EBP1 with poorer clinical outcome, as measured by progression-free survival (p-S6: P= .0874; p-4EBP1: P= .0475). Tumors with no PTEN expression had a higher MIB labeling index (P= .007). The majority of pediatric gliomas show activation of the PI3K/Akt/mTOR pathway, with methylation of the PTEN promoter occurring commonly in these tumors.

Pediatric neuro-oncology: current status and future directions

Tumors of the central nervous system (CNS) are the most common solid malignancies in childhood and are the leading cause of cancer-related death in this age group. While an ongoing improvement in overall prognosis has been achieved in the last few decades, current therapeutic approaches still confer significant morbidities, especially for the very young. The traditional strategies of surgery, radiotherapy and conventional cytotoxic chemotherapy need to be further refined while newer approaches, including molecularly targeted agents, hold the promise of better responses, improved outcomes and reduced toxicities. This article discusses treatment standards, the focus of current clinical investigations and the future promise of novel, biologically based approaches for the most common pediatric CNS tumors: primitive neuroectodermal tumors including medulloblastomas, ependymomas and astrocytomas (both low-grade and high-grade glioma).

Protease-activated receptor-2 (PAR2) mediates VEGF production through the ERK1/2 pathway in human glioblastoma cell lines

Glioblastoma (GBM) is a highly aggressive cancer type characterized by intense neovascularization. Several lines of evidence indicate that blood clotting enzymes play an important role in the tumor microenvironment, mainly through the activation of protease-activated receptors (PAR). In particular, PAR1 and PAR2 isoforms may activate signal transduction pathways that promote a number of pro-tumoral responses. However, little is known concerning the role of PAR1/PAR2 in GBM progression. In this study, we investigated the expression and function of PAR1 and PAR2 in the human GBM cell lines A172 and U87-MG. We also evaluated the effect of agonist peptides for PAR1 (PAR1-AP) and PAR2 (PAR2-AP) on signaling pathways and the expression of vascular endothelial growth factor (VEGF). Immunoblotting assays showed that A172 and U87-MG constitutively express PAR1 and PAR2. Treatment of GBM cells with PAR1-AP or PAR2-AP enhanced Akt (protein kinase B) and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation in a time-dependent manner. LY29042 and PD98059, inhibitors of the phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways, decreased PAR-mediated activation of Akt and ERK1/2, respectively. In addition, we observed that PAR2, but not PAR1, activation increased VEGF secretion in U87-MG and A172 cells. Notably, only PD98059 reduced PAR2-mediated VEGF production by GBM cells. Our results suggest that PAR2 modulates VEGF production through the MAPK/ERK1/2 pathway, and not the PI3K/Akt pathway, in human GBM cell lines. Therefore, the PAR2/MAPK signaling axis might be regarded as a relevant target for adjuvant treatment of GBM with a possible impact on tumor angiogenesis.

Biologically targeted therapeutics in pediatric brain tumors

Pediatric brain tumors are often difficult to cure and involve significant morbidity when treated with traditional treatment modalities, including neurosurgery, conventional chemotherapy, and radiotherapy. During the past two decades, a clearer understanding of tumorigenesis, molecular growth pathways, and immune mechanisms in the pathogenesis of cancer has opened up promising avenues for therapy. Pediatric clinical trials with novel biologic agents are underway to treat various pediatric brain tumors, including high and low grade gliomas and embryonal tumors. As the therapeutic potential of these agents undergoes evaluation, their toxicity profiles are also becoming better understood. These agents have potentially better central nervous system penetration and lower toxicity profiles compared with conventional chemotherapy. In infants and younger children, biologic agents may prove to be of equal or greater efficacy compared with traditional chemotherapy and radiation therapy, and may reduce the deleterious side effects of traditional therapeutics on the developing brain. Molecular pathways implicated in pediatric brain tumors, agents that target these pathways, and current clinical trials are reviewed. Associated neurologic toxicities will be discussed subsequently. Considerable work is needed to establish the efficacy of these agents alone and in combination, but pediatric neurologists should be aware of these agents and their rationale.

Cell-type-dependent thyroid hormone effects on glioma tumor cell lines

Purpose. The present study investigated the potential effects of long-term T3 treatment on glioma tumor cell lines. Thyroid hormone action on cell growth, differentiation and survival during development may be of therapeutic relevance Methods and Results 1321N1 cell line, an astrocytoma grade II, and U87MG, a glioblastoma grade IV, were exposed for 2 and 4 days in medium deprived of T3 and in medium containing 1 nM T3. T3 promoted re-differentiation in both cell lines. However, T3 increased cell proliferation in 1321N1 (2 days) which declined thereafter (4 days) while in U87MG resulted in suppression of cell proliferation. At the molecular level, a 2.9 fold increase in the expression of TRα1 receptor was observed in U87MG versus 1321N1, P < 0.05. TRβ1 receptor was undetectable. These changes corresponded to a distinct pattern of T3-induced kinase signaling activation; T3 had no effect on ERK activation in both cell lines but significantly increased phospho-Akt levels in 1321N1. Conclusion. In conclusion, T3 can re-differentiate glioma tumor cells, whereas its effect on cell proliferation appears to be dependent on the type of tumor cell line with aggressive tumors being more sensitive to T3. TRα1 receptor may, at least in part, be implicated in this response.

Expression of pERK and pAKT in pediatric high grade astrocytomas: correlation with YKL40 and prognostic significance

The Ras signaling pathway, consisting of mitogen-activated protein kinase (MAPK) and PI3K/AKT signaling, is a prominent oncogenic pathways in adult diffuse gliomas, but few studies have evaluated such pathways in pediatric malignant gliomas. We investigated by immunohistochemistry MAPK and AKT signaling in a series of 28 pediatric high-grade gliomas (WHO grade III and IV). We sought a possible association of phospho-ERK (p-ERK) and phospho-AKT (p-AKT) with expression of other proteins involved in the Ras pathway, that is, YKL40, epidermal growth factor receptor (EGFR), EGFR vIII and c-Met. Moreover we correlated the expression of p-ERK and p-AKT with prognosis. No cases showed expression for c-Met and EGFR, and only one case was positive for EGFR vIII. YKL-40 protein was expressed in 43% of cases. We detected expression of p-ERK and p-AKT in 61% and 57%, respectively, of pediatric high grade gliomas. Statistical analysis comparing the two groups in term of high and low p-ERK and p-AKT expression showed a trend toward worse overall survival in patients with high expression of p-AKT. The activation of ERK and AKT suggest a possible role of this protein in inducing activation of the Ras signaling pathway in pediatric high-grade gliomas. Moreover high levels of p-AKT are associated with worse overall survival.

Treatment of high-grade glioma in children and adolescents

Pediatric high-grade gliomas (HGGs)--including glioblastoma multiforme, anaplastic astrocytoma, and diffuse intrinsic pontine glioma--are difficult to treat and are associated with an extremely poor prognosis. There are no effective chemotherapeutic regimens for the treatment of pediatric HGG, but many new treatment options are in active investigation. There are crucial molecular differences between adult and pediatric HGG such that results from adult clinical trials cannot simply be extrapolated to children. Molecular markers overexpressed in pediatric HGG include PDGFRα and P53. Amplification of EGFR is observed, but to a lesser degree than in adult HGG. Potential molecular targets and new therapies in development for pediatric HGG are described in this review. Research into bevacizumab in pediatric HGG indicates that its activity is less than that observed in adult HGG. Similarly, tipifarnib was found to have minimal activity in pediatric HGG, whereas gefitinib has shown greater effects. After promising phase I findings in children with primary CNS tumors, the integrin inhibitor cilengitide is being investigated in a phase II trial in pediatric HGG. Studies are also ongoing in pediatric HGG with 2 EGFR inhibitors: cetuximab and nimotuzumab. Other novel treatment modalities under investigation include dendritic cell-based vaccinations, boron neutron capture therapy, and telomerase inhibition. While the results of these trials are keenly awaited, the current belief is that multimodal therapy holds the greatest promise. Research efforts should be directed toward building multitherapeutic regimens that are well tolerated and that offer the greatest antitumor activity in the setting of pediatric HGG.

Treatment of recurrent diffuse intrinsic pontine glioma: the MD Anderson Cancer Center experience

Recurrent diffuse intrinsic pontine gliomas (DIPG) are traditionally treated with palliative care since no effective treatments have been described for these tumors. Recently, clinical studies have been emerging, and individualized treatment is attempted more frequently. However, an informative way to compare the treatment outcomes has not been established, and historical control data are missing for recurrent disease. We conducted a retrospective chart review of patients with recurrent DIPG treated between 1998 and 2010. Response progression-free survival and possible influencing factors were evaluated. Thirty-one patients were identified who were treated in 61 treatment attempts using 26 treatment elements in 31 different regimens. The most frequently used drugs were etoposide (14), bevacizumab (13), irinotecan (13), nimotuzumab (13), and valproic acid (13). Seven patients had repeat radiation therapy to the primary tumor. Response was recorded after 58 treatment attempts and was comprised of 0 treatment attempts with complete responses, 7 with partial responses, 20 with stable diseases, and 31 with progressive diseases The median progression-free survival after treatment start was 0.16 years (2 months) and was found to be correlated to the prior time to progression but not to the number of previous treatment attempts. Repeat radiation resulted in the highest response rates (4/7), and the longest progression-free survival. These data provide a basis to plan future clinical trials for recurrent DIPG. Repeat radiation therapy should be tested in a prospective clinical study.