Dissecting the functional significance of HSP90AB1 and other heat shock proteins in countering glioblastomas and ependymomas using omics analysis and drug prediction using virtual screening.

Heat shock proteins (HSPs) are the evolutionary family of proteins that are highly conserved and present widely in various organisms and play an array of important roles and cellular functions. Currently, very few or no studies are based on the systematic analysis of the HSPs in Glioblastoma (GBMs) and ependymomas. We performed an integrated omics analysis to predict the mutual regulatory differential HSP signatures that were associated with both glioblastoma and ependymomas. Further, we explored the various common dysregulated biological processes operating in both the tumors, and were analyzed using functional enrichment, gene ontology along with the pathway analysis of the predicted HSPs. We established an interactome network of protein-protein interaction (PPIN) to identify the hub HSPs that were commonly associated with GBMs and ependymoma. To understand the mutual molecular mechanism of the HSPs in both malignancies, transcription factors, and miRNAs overlapping with both diseases were explored. Moreover, a transcription factor-miRNAs-HSPs coregulatory network was constructed along with the prediction of potential candidate drugs that were based on perturbation-induced gene expression analysis. Based on the RNA-sequencing data, HSP90AB1 was identified as the most promising target among other predicted HSPs. Finally, the ranking of the drugs was arranged based on various drug scores. In conclusion, this study gave a spotlight on the mutual targetable HSPs, biological pathways, and regulatory signatures associated with GBMs and ependymoma with an improved understanding of crosstalk involved. Additionally, the role of therapeutics was also explored against HSP90AB1. These findings could potentially be able to explain the interplay of HSP90AB1 and other HSPs within these two malignancies.

Drug Repurposing in Pediatric Brain Tumors: Posterior Fossa Ependymoma and Diffuse Midline Glioma under the Looking Glass.

Tumors of the Central Nervous System (CNS) represent the leading cause of cancer-related deaths in children. Current treatment options are not curative for most malignant histologies, and intense preclinical and clinical research is needed to develop more effective therapeutic interventions against these tumors, most of which meet the FDA definition for orphan diseases. Increased attention is being paid to the repositioning of already-approved drugs for new anticancer indications as a fast-tracking strategy for identifying new and more effective therapies. Two pediatric CNS tumors, posterior fossa ependymoma (EPN-PF) type A and diffuse midline glioma (DMG) H3K27-altered, share loss of H3K27 trimethylation as a common epigenetic hallmark and display early onset and poor prognosis. These features suggest a potentially common druggable vulnerability. Successful treatment of these CNS tumors raises several challenges due to the location of tumors, chemoresistance, drug blood-brain barrier penetration, and the likelihood of adverse side effects. Recently, increasing evidence demonstrates intense interactions between tumor cell subpopulations and supportive tumor microenvironments (TMEs) including nerve, metabolic, and inflammatory TMEs. These findings suggest the use of drugs, and/or multi-drug combinations, that attack both tumor cells and the TME simultaneously. In this work, we present an overview of the existing evidence concerning the most preclinically validated noncancer drugs with antineoplastic activity. These drugs belong to four pharmacotherapeutic classes: antiparasitic, neuroactive, metabolic, and anti-inflammatory. Preclinical evidence and undergoing clinical trials in patients with brain tumors, with special emphasis on pediatric EPN-PF and DMG, are summarized and critically discussed.

Why haven't we solved intracranial pediatric ependymoma? Current questions and barriers to treatment advances.

Pediatric intracranial ependymoma has seen a recent exponential expansion of biological findings, rapidly dividing the diagnosis into several subgroups, each with specific molecular and clinical characteristics. While such subdivision may complicate clinical conclusions from historical trials, this knowledge also provides an opportunity for interrogating the major clinical and biological questions preventing near-term translation into effective therapy for children with ependymoma. In this article, we briefly review some of the most critical clinical questions facing both patient management and the construct of future trials in childhood ependymoma, as well as explore some of the current barriers to efficient translation of preclinical discovery to the clinic.

Infantile metastatic ependymoma with a novel molecular profile and favorable outcome to intensive chemotherapy without irradiation: Case-based review.

Ependymal tumors are the third most common brain tumor under 14 years old. Even though metastatic disease is a rare event, it affects mostly young children and carries an adverse prognosis. The factors associated with dissemination and the best treatment approach have not yet been established and there is limited published data on how to manage metastatic disease, especially in patients under 3 years of age. We provide a review of the literature on clinical characteristics and radiation-sparing treatments for metastatic ependymoma in children under 3 years of age treated. The majority (73%) of the identified cases were above 12 months old and had the PF as the primary site at diagnosis. Chemotherapy-based approaches, in different regimens, were used with radiation reserved for progression or relapse. The prognosis varied among the studies, with an average of 50%-58% overall survival. This study also describes the case of a 7-month-old boy with metastatic posterior fossa (PF) ependymoma, for whom we identified a novel SPECC1L-RAF1 gene fusion using a patient-centric comprehensive molecular profiling protocol. The patient was successfully treated with intensive induction chemotherapy followed by high-dose chemotherapy and autologous hematopoietic progenitor cell rescue (AuHSCR). Currently, the patient is in continuous remission 5 years after his diagnosis, without radiation therapy. The understanding of the available therapeutic approaches may assist physicians in their management of such patients. This report also opens the perspective of newly identified molecular alterations in metastatic ependymomas that might drive more chemo-sensitive tumors.

Metronomic Cyclophosphamide With Cisplatin and Bevacizumab for Refractory Anaplastic Ependymoma: A Retrospective Study.

BACKGROUND/AIM: Anaplastic ependymoma is a rare cancer of the central nervous system. The treatment includes optimal resection with focal radiotherapy. Some case reports or retrospective studies have suggested efficacy of regimens containing platinum or bevacizumab. We describe the feasibility and clinical benefit of the cisplatin-bevacizumab-cyclophosphamide treatment of anaplastic ependymoma. PATIENTS AND METHODS: Patients were identified through the Adolescent and Young Adults (AYAS) brain tumor national Web conference. We estimated the median progression-free (PFS) and overall survival (OS). RESULTS: There were eight patients with anaplastic ependymoma, with a median age of 36 years. The median OS was 19.9 months and median PFS was 12.3 months. Three patients obtained partial response, four stable disease, and one patient had disease progression during induction. Six patients received maintenance with a median duration of 224 days. CONCLUSION: This study confirms the tolerance of bevacizumab-cyclophosphamide-cisplatin treatment of anaplastic ependymoma. The clinical benefit seems even superior to that described in the literature.

Systemic chemotherapy of pediatric recurrent ependymomas: results from the German HIT-REZ studies.

PURPOSE: Survival in recurrent ependymoma (EPN) depends mainly on the extent of resection achieved. When complete resection is not feasible, chemotherapy is often used to extend progression-free and overall survival. However, no consistent effect of chemotherapy on survival has been found in patients with recurrent EPN. METHODS: Systemic chemotherapeutic treatment of 138 patients enrolled in the German HIT-REZ-studies was analyzed. Survival depending on the use of chemotherapy, disease-stabilization rates (RR), duration of response (DOR) and time to progression (TTP) were estimated. RESULTS: Median age at first recurrence was 7.6 years (IQR: 4.0-13.6). At first recurrence, median PFS and OS were 15.3 (CI 13.3-20.0) and 36.9 months (CI 29.7-53.4), respectively. The Hazard Ratio for the use of chemotherapy in local recurrences in a time-dependent Cox-regression analysis was 0.99 (CI 0.74-1.33). Evaluable responses for 140 applied chemotherapies were analyzed, of which sirolimus showed the best RR (50%) and longest median TTP [11.51 (CI 3.98; 14.0) months] in nine patients, with the strongest impact found when sirolimus was used as a monotherapy. Seven patients with progression-free survival > 12 months after subtotal/no-resection facilitated by chemotherapy were found. No definitive survival advantage for any drug in a specific molecularly defined EPN type was found. CONCLUSION: No survival advantage for the general use of chemotherapy in recurrent EPN was found. In cases with incomplete resection, chemotherapy was able to extend survival in individual cases. Sirolimus showed the best RR, DOR and TTP out of all drugs analyzed and may warrant further investigation.

Bevacizumab as a surgery-sparing agent for spinal ependymoma in patients with neurofibromatosis type II: Systematic review and case.

Neurofibromatosis type 2 (NF2) is a rare, hereditary tumor syndrome, often requiring repeated surgeries for multiple lesions with significant cumulative morbidity. As such, non-operative management should be considered when possible for this patient population. The aim of this study is to provide a systematic review of the literature regarding this treatment strategy. A descriptive case of a patient in whom bevacizumab treatments enabled over 15 years of surgical postponement for a symptomatic spinal cord ependymoma is also provided. Evidence suggests that bevacizumab is a reasonable surgery-deferring option for cystic lesions, and it may be especially useful in NF2 patients to reduce cumulative morbidity.

The BET Inhibitor OTX015 Exhibits In Vitro and In Vivo Antitumor Activity in Pediatric Ependymoma Stem Cell Models.

Childhood ependymomas are heterogenous chemoresistant neoplasms arising from aberrant stem-like cells. Epigenome deregulation plays a pivotal role in ependymoma pathogenesis, suggesting that epigenetic modifiers hold therapeutic promise against this disease. Bromodomain and extraterminal domain (BET) proteins are epigenome readers of acetylated signals in histones and coactivators for oncogenic and stemness-related transcriptional networks, including MYC/MYCN (Proto-Oncogene, BHLH Transcritpion Factor)-regulated genes. We explored BET inhibition as an anticancer strategy in a panel of pediatric patient-derived ependymoma stem cell models by OTX015-mediated suppression of BET/acetylated histone binding. We found that ependymoma tissues and lines express BET proteins and their targets MYC and MYCN. In vitro, OTX015 reduced cell proliferation by inducing G0/G1-phase accumulation and apoptosis at clinically tolerable doses. Mechanistically, inhibitory p21 and p27 increased in a p53-independent manner, whereas the proliferative driver, phospho-signal transducer and activator of transcription 3 (STAT3), decreased. Upregulation of apoptosis-related proteins and survivin downregulation were correlated with cell line drug sensitivity. Minor alterations of MYC/MYCN expression were reported. In vivo, OTX015 significantly improved survival in 2/3 orthotopic ependymoma models. BET proteins represent promising targets for pharmaceutical intervention with OTX015 against ependymoma. The identification of predictive determinants of sensitivity may help identify ependymoma molecular subsets more likely to benefit from BET inhibitor therapies.

A phase II study of dose-dense temozolomide and lapatinib for recurrent low-grade and anaplastic supratentorial, infratentorial, and spinal cord ependymoma.

BACKGROUND: No standard medical treatment exists for adult patients with recurrent ependymoma, and prospective clinical trials in this population have not succeeded because of its rarity and challenges in accruing patients. The Collaborative Ependymoma Research Network conducted a prospective phase II clinical trial of dose-dense temozolomide (TMZ) and lapatinib, targeting the unmethylated O6-methylguanine-DNA methyltransferase (MGMT) promoter status and increased expression of ErbB2 (human epidermal growth factor receptor 2) and ErbB1 (epidermal growth factor receptor) in ependymomas. METHODS: Patients age 18 or older with histologically proven and progressive ependymoma or anaplastic ependymoma were eligible and received dose-dense TMZ and daily lapatinib. The primary outcome measure was median progression-free survival (PFS). Landmark 6- and 12-month PFS and objective response were measured. Serial assessments of symptom burden using the MD Anderson Symptom Inventory Brain Tumor (MDASI-BT)/MDASI-Spine Tumor modules were collected. RESULTS: The 50 patients enrolled had a median age of 43.5 years, median Karnofsky performance status of 90, and a median of 2 prior relapses. Twenty patients had grade III, 16 grade II, and 8 grade I ependymoma. Half had spinal cord tumors; 15 had a supratentorial tumor, 8 infratentorial, and 2 had disseminated disease. Treatment was well tolerated. The median PFS was 7.8 months (95% CI: 5.5,12.2); the 6- and 12-month PFS rates were 55% and 38%, with 2 complete and 6 partial responses. Measures of symptom burden showed reduction in moderate-severe pain and other disease-related symptoms in most patients. CONCLUSIONS: This treatment, with demonstrated clinical activity with objective responses and prolonged disease control associated with disease-related symptom improvements, is an option as a salvage regimen for adult patients with recurrent ependymoma.

The potentially therapeutic targets of pediatric anaplastic ependymoma by transcriptome profiling.

Ependymoma (EPN) is a type of tumor that occurs in the central nervous system of children and adults. EPN produces resistance to chemotherapy, and there are no targeted drugs available as a proper cure. Therefore, the use of high-throughput sequencing technologies to elucidate pathogenic mechanisms is of prime importance to identify potential tumor target genes helpful for developing effective therapeutic approaches against EPN. With this objective, we used RNA-seq analysis to identify differentially expressed genes (DEGs) and pathways in 4 pairs of EPN tissues and adjacent tissues. In total, we found 5,445 differentially expressed genes. The synaptic vesicle cycle and extracellular matrix (ECM) receptor interaction pathways were highly enriched in the ependymoma group. Nine differentially expressed genes (SNAP25, GRM4, CELSR1, LAMA1, WNT5A, ROR2, CCND1, EPHB2, FOXJ1) were randomly verified by RT-qPCR, supporting the authenticity of our sequencing results. This study provides global gene information and some new potential biomarkers for the diagnosis and therapeutic targets of ependymoma.

Local and systemic therapy of recurrent ependymoma in children and adolescents: short- and long-term results of the E-HIT-REZ 2005 study.

BACKGROUND: Survival in recurrent ependymomas in children and adolescents mainly depends on the extent of resection. Studies on repeated radiotherapy and chemotherapy at relapse have shown conflicting results. METHODS: Using data from the German multi-center E-HIT-REZ-2005 study, we examined the role of local therapy and the efficacy of chemotherapy with blockwise temozolomide (TMZ) in children and adolescents with recurrent ependymomas. RESULTS: Fifty-three patients with a median age of 6.9 years (1.25-25.4) at first recurrence and a median follow-up time of 36 months (2-115) were recruited. Gross- and near-total resection (GTR/NTR) were achieved in 34 (64.2%) patients and associated with a markedly improved 5-year overall survival (OS) of 48.7% vs. 5.3% in less than GTR/NTR. Radiotherapy showed no improvement in OS following complete resection (OS: 70 (CI: 19.9-120.1) vs. 95 (CI: 20.7-169.4) months), but an advantage was found in less than GTR/NTR (OS: 22 (CI: 12.7-31.3) vs. 7 (CI: 0-15.8) months). Following the application of TMZ, disease progression was observed in most evaluable cases (18/21). A subsequent change to oral etoposide and trofosfamide showed no improved response. PF-A EPN were most abundant in relapses (n = 27). RELA-positive EPN (n = 5) had a 5-year OS of 0%. CONCLUSION: The extent of resection is the most important predictor of survival at relapse. Focal re-irradiation is a useful approach if complete resection cannot be achieved, but no additional benefit was seen after GTR/NTR. Longer-term disease stabilization (>6 months) mediated by TMZ occurred in a small number of cases (14.3%).

Sub-group, Sub-type, and Cell-type Heterogeneity of Ependymoma.

Ependymomas are aggressive central nervous system tumors that resist chemotherapy. In this issue of Cancer Cell, Gojo et al. dissect the single cell transcriptional landscapes of ependymoma to define cellular programs that mediate therapeutic resistance, tumor aggressiveness, and potential targets for therapy.

Caracterización de los pacientes con ependimoma intracraneal en el hospital pediátrico Juan Manuel Márquez. 2012-2017 / Characterization of patients with intracranial ependymoma in the pediatric hospital Juan Manuel Márquez. 2012-2017

RESUMEN Introducción: los ependimomas constituyen aproximadamente del 3-5 % de los tumores intracraneales y del 5-10 % de los tumores cerebrales, en la edad pediátrica. Objetivo: caracterizar los pacientes con ependimomas intracraneales intervenidos quirúrgicamente, en el Hospital Pediátrico ¨Juan Manuel Márquez. ¨ Materiales y método: estudio descriptivo, retrospectivo, a pacientes en edad pediátrica con diagnóstico histológico de ependimoma de localización intracraneal. En el período de enero 2012 a diciembre 2017. El universo quedó conformado por todos los pacientes en edad pediátrica operados con diagnóstico histológico de ependimoma intracraneal en el lugar y período antes mencionado (N=22). Resultados: la edad media fue 2,75 años con límites entre 1 y 17 y una desviación estándar de 3,65. Los pacientes del sexo masculino representaron el 63,64 %, la relación con el sexo femenino en los primeros 4 años fue de 1:1. En cuanto al cuadro clínico, se observó predominio de la hidrocefalia en el 72,73 % de los pacientes. Los ependimomas intracraneales de localización infratentorial, (63,64 %) predominaron. El 45,45 % de las lesiones estudiadas se correspondían con el subtipo histológico de ependimoma anaplásico. Conclusiones: la combinación de cirugía, radioterapia y quimioterapia se empleó en la mayoría de los casos. Predominó el abordaje directo de la lesión a través de craneotomía y exéresis adecuada a la localización del ependimoma, sin embargo, en la mayoría solo se logró resección entre el 50 y 90 %. En la mayoría de los pacientes la evolución luego del diagnóstico, evidenció una tendencia hacia la estabilidad (AU).

ABSTRACT Introduction: ependymoma are almost 3-5 % of the intracranial tumors and 5-10 % of the brain tumors in pediatric age. Objective: to characterize the patients with intracranial ependymoma who underwent surgery in the Pediatric Hospital ¨Juan Manuel Márquez.¨ Materials and method: retrospective, descriptive study of patients in pediatric age with histological diagnosis of ependymoma of intracranial location in the period January 2012-December 2017. The universe was formed by all patients of pediatric age who underwent surgery with histological diagnosis of intracranial ependymoma in the before-mentioned place and period (N=22). Results: the average age was 2.75 years with limits between 1 and 17 years old. Male patients represented 63.64 %; the relation with female sex during the first 4 years was 1:1. Regarding the clinical characteristics, hydrocephaly predominated in 72.73 % of patients. Intracranial ependymoma of infratentorial location (63.64 %) predominated. 45.45 % of the studied lesions corresponded to the histological subtype of anaplastic ependymoma. Conclusions: the combination of surgery, radiotherapy and chemotherapy was used in most of the cases. The direct approach of the lesion through craniotomy and a removal adequate to ependymoma location predominated. However, in most of them just the resection of 50-90 % was achieved. The evolution of most of patients after the diagnosis evidenced a tendency to the stability (AU).

Phase I study of intraventricular infusions of autologous ex vivo expanded NK cells in children with recurrent medulloblastoma and ependymoma.

BACKGROUND: Recurrent pediatric medulloblastoma and ependymoma have a grim prognosis. We report a first-in-human, phase I study of intraventricular infusions of ex vivo expanded autologous natural killer (NK) cells in these tumors, with correlative studies. METHODS: Twelve patients were enrolled, 9 received protocol therapy up to 3 infusions weekly, in escalating doses from 3 × 106 to 3 × 108 NK cells/m2/infusion, for up to 3 cycles. Cerebrospinal fluid (CSF) was obtained for cellular profile, persistence, and phenotypic analysis of NK cells. Radiomic characterization on pretreatment MRI scans was performed in 7 patients, to develop a non-invasive imaging-based signature. RESULTS: Primary objectives of NK cell harvest, expansion, release, and safety of 112 intraventricular infusions of NK cells were achieved in all 9 patients. There were no dose-limiting toxicities. All patients showed progressive disease (PD), except 1 patient showed stable disease for one month at end of study follow-up. Another patient had transient radiographic response of the intraventricular tumor after 5 infusions of NK cell before progressing to PD. At higher dose levels, NK cells increased in the CSF during treatment with repetitive infusions (mean 11.6-fold). Frequent infusions of NK cells resulted in CSF pleocytosis. Radiomic signatures were profiled in 7 patients, evaluating ability to predict upfront radiographic changes, although they did not attain statistical significance. CONCLUSIONS: This study demonstrated feasibility of production and safety of intraventricular infusions of autologous NK cells. These findings support further investigation of locoregional NK cell infusions in children with brain malignancies.

National trends in management of adult myxopapillary ependymomas.

Myxopapillary ependymomas (MPE) are WHO Grade I ependymomas that annually occur in 0.05-0.08 per 100,000 people. Surgical resection is the recommended first line therapy. Due to the rarity of the disease, there is a relatively poor understanding of the use of radiotherapy (RT) in managing this disease. The National Cancer Database (NCDB) was analyzed for patterns of care foradult MPE diagnosed between 2002 and 2016. Of 753 qualifying cases, the majority of patients underwent resection (n = 617, 81.9%). A relatively small portion received RT (n = 103, 13.3%) with most receiving RT post-operatively (n = 98, 95.1%). The likelihood of patients to undergo resection and RT was associated with patient age at diagnosis (p = 0.002), tumor size (p < 0.001), and race (p = 0.017). Chemotherapy was not widely utilized (0.27% of patients). One limitation of our analysis is that there was no data on progression free survival (PFS), an important outcome given the high survival rate in this disease. Surgery remains the primary means to manage adult MPE. For spinal MPE, it is understood that gross total resection (GTR) should be attempted whenever possible as GTR has been associated with improved PFS in several studies. The impact of RT on overall survival (OS) is indeterminate given the 1.6% death rate in the cohort. Analyses of the impact of RT on PFS in a larger database would be beneficial for determining an algorithm for post-operative and definitive RT in this disease entity.

Propofol Total Intravenous Anesthesia as an Intervention for Severe Radiation-Induced Phantosmia in an Adolescent with Ependymoma.

Radiation-induced phantosmia has been reported both in children and adults. A fraction of these patients have nausea and vomiting triggered by phantosmia. Radiation-induced phantosmia, although transient, can be distressing enough to prevent a patient from staying still during radiation therapy. To date, specific interventions for radiation-induced phantosmia, including anesthesia, have not been reported. We report for the first time anesthesia as an intervention for transient severe radiation-induced phantosmia, in a 16-year-old girl with ependymoma undergoing proton therapy, and we discuss the pros and cons of techniques for anesthesia and airway management.

New therapeutic target for pediatric anaplastic ependymoma control: study of anti-tumor activity by a Kunitz-type molecule, Amblyomin-X.

EPNs comprise a heterogeneous group of neuroepithelial tumors, accounting for about 10% of all intracranial tumors in children and up to 30% of brain tumors in those younger than 3 years. Actually, the pattern therapy for low-grade EPNs includes complete surgical resection followed by radiation therapy. Total surgical excision is often not possible due to tumor location. The aim of this study was to evaluate, for the first time, the anti-tumor activity of Amblyomin-X in 4 primary cultures derived from pediatric anaplastic posterior fossa EPN, Group A (anaplastic, WHO grade III) and one primary culture of a high grade neuroepithelial tumor with MN1 alteration, which was initially misdiagnosed as EPN: i) by in vitro assays: comparisons of temozolomide and cisplatin; ii) by intracranial xenograft model. Amblyomin-X was able to induce cell death in EPN cells in a more significant percentage compared to cisplatin. The cytotoxic effects of Amblyomin-X were not detected on hFSCs used as control, as opposed to cisplatin-treatment, which promoted a substantial effect in the hAFSCs viability. TEM analysis showed ultrastructural alterations related to the process of cell death: mitochondrial degeneration, autophagosomes and aggregate-like structures. MRI and histopathological analyzes demonstrated significant tumor mass regression. Our results suggest that Amblyomin-X has a selective effect on tumor cells by inducing apoptotic cell death and may be a therapeutic option for Group AEPNs.

A novel imaging flow cytometry method for the detection of histone H4 acetylation in myeloid cells.

BACKGROUND: The histone deacetylase inhibitor (HDACI) valproic acid has been shown to inhibit the growth of multiple paediatric tumour types and is well tolerated in a childhood cancer setting. The current study was designed to develop a novel imaging flow cytometry method for the detection of histone H4 acetylation in white blood cells obtained from childhood cancer patients treated with valproic acid. MATERIALS AND METHODS: HL-60 cells and whole blood samples from healthy volunteers were incubated with valproic acid (0-8 mM) for 0-24 hours, with additional blood samples collected from ependymoma patients receiving valproic acid on the SIOP Ependymoma II clinical trial. An imaging flow cytometry method was developed using an ImageStream®χ flow cytometer, collecting 100 000 images per sample following excitation of PE tagged acH4 antibody and DAPI. RESULTS: The mean percentage of acH4-positive cells increased to a greater extent than increases in mean and median fluorescence intensity following incubation with valproic acid. Comparable results were observed for in vitro and ex vivo experiments, and the assay was shown to be appropriate for clinical sample analysis. Myeloid cells exhibited a smaller proportion of acH4-positive cells than the lymphoid population, but a greater fold increase above basal levels. CONCLUSIONS: The percentage of acH4-positive myeloid cells has the potential to be used as a robust pharmacodynamic biomarker for the measurement of acH4 for HDACIs. The developed assay is now being utilised in a clinical trial involving the treatment of childhood ependymoma patients with valproic acid.