Plasma ctDNA Monitoring of a PTCH1-Mutant Metastatic Adult Medulloblastoma Showing a Durable Benefit With Vismodegib.

Adult medulloblastoma (MB) is a rare disease affecting 0.6 persons per million adults over 19 years of age. The SHH-activated/TP53-wild type is the most common subtype, accounting for 60% of adult MBs, being characterized by mutations in PTCH1, SMO, or the TERT promoter. Several small studies demonstrate objective but short-lived responses to SMO inhibitors such as vismodegib or sonidegib. Like other oncogene-addicted solid tumors, detection of the corresponding drivers through liquid biopsy could aid in the molecular diagnosis and monitoring of the disease through less invasive procedures. However, most studies have only evaluated cerebrospinal fluid as the ctDNA reservoir, and very limited evidence exists on the role of liquid biopsy in plasma in patients with primary central nervous system tumors, including MB. We present the case of a 26-year-old patient with a recurrent MB, in which next-generation sequencing (FoundationOne CDx) revealed a mutation in PTCH1, allowing the patient to be treated with vismodegib in second line, resulting in a durable benefit lasting for 1 year. Using an in-house digital PCR probe, the PTCH1 mutation could be tracked in ctDNA during treatment with first-line chemotherapy and while on treatment with vismodegib, demonstrating a precise correlation with the radiological and clinical behavior of the disease.

Electrochemical biosensing of circulating microRNA-21 in cerebrospinal fluid of medulloblastoma patients through target-induced redox signal amplification.

Monitoring of cerebrospinal fluid (CSF) microRNAs (miRs) offers a promising option for the diagnosis and management of patients with central nervous system tumors. However, the sensitive detection of miRs in clinical CSF samples has been hindered by the ultra-low abundance of target miRs. Here, we report an electrochemical biosensor for the highly sensitive label-free detection of CSF miR-21 relying on target-induced redox signal amplification (eTIRSA). The biosensor was developed by covalently assembling the capture stands partially complementary to miR-21 on the gold nanoparticle-coated glassy carbon electrode. In the presence of miR-21, the short capture stand hybridized with the partial bases of miR-21, allowing the rest sequence of the target molecule to further bind with a long guanine-rich sequence which could specifically adsorb a number of methylene blue indicators, thus generating an amplified electrochemical redox signal, typically at a working potential of - 0.19 V (vs. SCE). The response of the surface-bound methylene blue indicators was positively correlated to the concentration of miR-21, providing a dynamic range of 0.5-80 pM and a limit of detection down to 56 fM. Moreover, the eTIRSA biosensor had high specificity with single-base resolution and exhibited good performance for label-free quantification of miR-21 in medulloblastoma cell extracts and clinical CSF samples and for accurate discrimination of medulloblastoma against non-cancer controls, indicating its potential application in CSF miR-based liquid biopsy of brain cancers.

Endocrinological late effects of oncologic treatment on survivors of medulloblastoma. / Efectos endocrinológicos tardíos del tratamiento oncológico en supervivientes de meduloblastoma.

INTRODUCTION: Radiation therapy, chemotherapy, and surgery used to treat brain tumors have effects on the hy pothalamic-pituitary-adrenal axis and can result in endocrine dysfunction in up to 96% of cases. PATIENTS AND METHOD: Retrospective and descriptive study in patients diagnosed with medulloblasto ma who underwent treatment with chemo and radiotherapy in the last 20 years in a tertiary hospital. The variables analyzed were age, sex, weight, height, body mass index (BMI) at the end of follow-up, sexual maturity stage, serum levels of TSH and free T4, ACTH/cortisol and IGF-1, FSH, LH, estradiol, testosterone, lipid profile (total cholesterol), and growth hormone dynamic function test. RESULTS: Total sample of 23 patients. Growth hormone deficiency is the most frequent sequelae (82%) fo llowed by thyroid dysfunction (44.8%), and disorders of puberty (24.1%). Only one case of diabetes insipidus and two cases of corticotropin deficiency were diagnosed. CONCLUSIONS: Long-term follow- up of medulloblastoma survivors treated with chemo and radiotherapy reveals a very high prevalence of endocrine dysfunction, especially growth hormone deficiency and hypothyroidism. We believe that monitoring and long-term follow-up of these patients is necessary in order to ensure adequate therapeutic management of those treatable dysfunctions.

Pre-treatment lymphopenia and indication of tumor-induced systemic immunosuppression in medulloblastoma.

The presence of tumor-induced systemic immune suppression, including lymphopenia, has been recognized in adult patients with glioblastoma for several decades, and pre-treatment neutrophil-to-lymphocyte count ratio (NLCR) is associated with inferior clinical outcome in patients with glioblastoma. Whether tumor-induced systemic immune suppression is also present in children with malignant brain tumors is not known. We performed a retrospective analysis of pretreatment neutrophil and lymphocyte counts in pediatric patients with medulloblastoma (MB) compared to a control group of children with posterior fossa pilocytic astrocytoma (PA). Compared to the control group, we observed statistically significantly lower absolute lymphocyte counts (ALCs) and higher NLCRs in the medulloblastoma group. Our findings suggest the presence of tumor-induced systemic immune suppression in MB patients already present at the time of diagnosis, with potential implications for the development of immune therapies in this population.

Pre-operative neutrophil count and neutrophil-lymphocyte count ratio (NLCR) in predicting the histological grade of paediatric brain tumours: a preliminary study.

INTRODUCTION: The neutrophil-lymphocyte count ratio (NLCR) is an established prognostic marker for renal, lung and colorectal carcinomas and has been suggested to be predictive of histological grade and outcome in adult intracranial tumours. The purpose of this study was to determine whether a correlation of the pre-operative neutrophil count (NC) and NLCR with the final histological grade exists in paediatric intracranial tumours. METHODS: A retrospective analysis was undertaken at a single centre. Patients less than 18 years old at the time of surgery who underwent tumour-related procedures from 2006 to 2015 were included. Patients with recurrent tumours, previous bone marrow transplant and metastases were excluded. Pre-operative full blood counts (FBC), collected before the diagnosis of intracranial pathology and before administration of steroids, were matched with histological diagnosis for each patient. Post-operative FBC was also recorded, together with survival data where applicable. RESULTS: A total of 116 patients (74 male, 42 female; mean age, 8 ± 0.9 years) with a diagnosis of primary intracranial tumours had pre-operative FBC that could be matched to final histological grade. Pre-operative NC and NLCR were higher with increasing grade of tumour: grade 1 (NC 4.29 109/l, NLCR 2.26), grade 2 (NC 4.59 109/l, NLCR 2.38), grade 3 (NC 5.67 109/l, NLCR 2.72) and grade 4 (NC 6.59 109/l, NLCR 3.31). Patients with WHO grade 1 and 2 tumours pooled together had a lower NC (4.37 95% CI ± 0.67 109/l) compared to WHO grade 3 and 4 patients (6.41 95% CI ± 0.99 109/l, p = 0.0013). The NLCR was lower in grade 1 and 2 tumours (2.29 ± 0.59) (compared to grade 3 and 4 tumours; 3.20 ± 0.76) but this did not reach significance (p = 0.069). The subgroup of patients with pilocytic astrocytoma had a significantly lower NC when compared to patients with high-grade tumours (p = 0.005). Medulloblastoma and supratentorial PNET subgroups had significantly higher NC compared to the low-grade group (p = 0.033, p = 0.002). Post-operative NC was significantly higher in the high-grade tumours (p = 0.034), but no difference was observed for NLCR (p = 0.28). CONCLUSIONS: No evidence exists to support the correlation of pre-operative NC or NLCR to histological diagnosis in paediatric intracranial tumours. Our results indicate that a higher pre-operative NC/NLCR correlates with a higher histological grade of tumour. This suggests that immunological mechanisms may be involved in the pathogenesis of paediatric brain tumours, and a further prospective study is required to substantiate and expand these findings.

Regulatory T cell subsets in patients with medulloblastoma at diagnosis and during standard irradiation and chemotherapy (PBTC N-11).

BACKGROUND: We evaluated circulating levels of immunosuppressive regulatory T cells (Tregs) and other lymphocyte subsets in patients with newly diagnosed medulloblastoma (MBL) undergoing surgery compared to a control cohort of patients undergo craniectomy for correction of Chiari malformation (CM) and further determined the impact of standard irradiation and chemotherapy on this cell population. METHODS: Eligibility criteria for this biologic study included age 4-21 years, patients with CM undergoing craniectomy (as non-malignant surgical controls) and receiving dexamethasone for prevention of post-operative nausea, and those with newly diagnosed posterior fossa tumors (PFT) undergoing surgical resection and receiving dexamethasone as an anti-edema measure. Patients with confirmed MBL were also followed for longitudinal blood collection and analysis during radiotherapy and chemotherapy. RESULTS: A total of 54 subjects were enrolled on the study [22-CM, 18-MBL, and 14-PFT]. Absolute number and percentage Tregs (defined as CD4+CD25+FoxP3+CD127low/-) at baseline were decreased in MBL and PFT compared to CM [p = 0.0016 and 0.001, respectively). Patients with MBL and PFT had significantly reduced overall CD4+ T cell count (p = 0.0014 and 0.0054, respectively) compared to those with CM. Radiation and chemotherapy treatment in patients with MBL reduced overall lymphocyte counts; however, within the CD4+ T cell compartment, Tregs increased during treatment but gradually declined post therapy. CONCLUSIONS: Our results demonstrate that patients with MBL and PFT exhibit overall reduced CD4+ T cell counts at diagnosis but not an elevated proportion of Tregs. Standard treatment exacerbates lymphopenia in those with MBL while enriching for immunosuppressive Tregs over time.

Impact of acute hematological toxicity on treatment interruptions during cranio-spinal irradiation in medulloblastoma: a tertiary care institute experience.

To analyze treatment interruptions due to acute hematological toxicity in patients of medulloblastoma receiving cranio-spinal irradiation (CSI). Prospectively collected data from case records of 52 patients of medulloblastoma treated between 2011 and 2014 was evaluated. Blood counts were monitored twice a week during CSI. Spinal irradiation was interrupted for patients with ≥grade 2 hematological toxicity and resumed after recovery to grade 1 level (TLC >3000; platelet count >75,000). Treatment interruptions and hematological toxicity were analyzed. Median age was 11 years. All patients received adjuvant CSI of 36 Gy, followed by boost of 18 Gy to posterior fossa, at 1.8 Gy per fraction. Concurrent chemotherapy was not given. Adjuvant chemotherapy was given after CSI for high risk patients. Spinal fields were interrupted in 73.1% of patients. Cause of first interruption was leucopenia in 92.1%, thrombocytopenia in 2.6%, and both in 5.3%. Median number of fractions at first interruption was 8, with 25% of interruptions in first week. Median duration for hematological recovery after nadir was 5 days for leucopenia and 3 days for thrombocytopenia. Half of the patients had at least 2 interruptions, and 19% subsequently developed grade 3 toxicity. On multivariate analysis, significant correlation with duration of delay was observed for pre-treatment haemoglobin, number of fractions at first interruption, grade and duration of recovery of leucopenia. Acute hematological toxicity with CSI is frequently under-reported. Patients with low pre-treatment hemoglobin, early onset leucopenia, profound leucopenia and prolonged recovery times are at a higher risk of having protracted courses of irradiation. Frequent monitoring of blood counts and timely interruption of spinal fields of irradiation at grade 2 level of hematological toxicity minimizes the risk of grade 3 and grade 4 toxicity, while reducing the interruptions in irradiation of the gross tumour bed.

Is the NBN gene mutation I171V a potential risk factor for malignant solid tumors in children?

NBN gene is considered as one of the low-to-moderate cancer susceptibility gene. At least 4 germline NBN mutations have been found in several malignancies in adults. In our studies, we observed the high incidence of germline mutation I171V of NBN gene in breast, colorectal, larynx cancer, and in multiple primary tumors. In this study, we would like to answer the question whether I171V germline mutation of NBN gene may constitute risk factor for solid tumors in children. The frequency of this mutation has been analyzed in patients with neuroblastoma (n=66), Wilms tumor (n=54), medulloblastoma (n=57), and rhabdomyosarcoma (n=82) hospitalized in Pediatric Oncology, Hematology and Bone Marrow Transplantation Department in the years between 1987 and 2010. About 2947 anonymous blood samples collected on Guthrie cards drawn from the newborn screening program of the Wielkopolska region have been used as controls. All the patients and controls came from the same geographical region. I171V mutation of the NBN gene has been observed in 5 controls. Among children with solid tumors only in 1 child with medulloblastoma I171V variant has been found. In conclusion, I171V germline mutation in contrary to adults cannot be considered as a risk factor for children malignancies. However, owing to low number of patients with solid tumors the possibility of a Type II error may exist.

Circulating Lymphocyte Counts Early During Radiation Therapy Are Associated With Recurrence in Pediatric Medulloblastoma.

PURPOSE: Decreased peripheral lymphocyte counts are associated with survival after radiation therapy (RT) in several solid tumors, although they appear late during or after the radiation course and often correlate with other clinical factors. Here we investigate if absolute lymphocyte counts (ALCs) are independently associated with recurrence in pediatric medulloblastoma early during RT. METHODS AND MATERIALS: We assessed 202 patients with medulloblastoma treated between 2000 and 2016 and analyzed ALC throughout therapy, focusing on both early markers (ALC during week 1 - ALCwk1; grade 3+ Lymphopenia during week 2 - Lymphopeniawk2) and late markers (ALC nadir). Uni- and multivariable regressions were used to assess association of clinical and treatment variables with ALC and of ALC with recurrence. RESULTS: Thirty-six recurrences were observed, with a median time to recurrence of 1.6 years (range, 0.2-10.3) and 7.1 years median follow-up. ALC during RT was associated with induction chemotherapy (P < .001), concurrent carboplatin (P = .009), age (P = .01), and high-risk status (P = .05). On univariable analysis, high-risk disease (hazard ratio = 2.0 [1.06-3.9]; P = .03) and M stage≥1 (hazard ratio = 2.2 [1.1-4.4]) were associated with recurrence risk, as was lower ALC early during RT (ALCwk1, hazard ratio = 0.28 [0.12-0.65]; P = .003; Lymphopeniawk2, hazard ratio = 2.27 [1.1-4.6]; P = .02). Neither baseline ALC nor nadir correlated with outcome. These associations persisted when excluding carboplatin and pre-RT chemotherapy patients, and in the multivariable analysis accounting for confounders lymphocyte counts remained significant (ALCwk1, hazard-ratio = 0.23 [0.09-0.57]; P = .002; Lymphopeniawk2, hazard-ratio = 2.3 [1.1-4.8]; P = .03). CONCLUSIONS: ALC during weeks 1 and 2 of RT was associated with recurrence, and low ALC is an independent prognostic factor in medulloblastoma. Strategies to mitigate the risk of radiation-induced lymphopenia should be considered.

Exploring genetic alterations in circulating tumor DNA from cerebrospinal fluid of pediatric medulloblastoma.

Medulloblastoma (MB) is the most common type of brain malignancy in children. Molecular profiling has become an important component to select patients for therapeutic approaches, allowing for personalized therapy. In this study, we successfully identified detectable levels of tumor-derived cell-free DNA (cfDNA) in cerebrospinal fluid (CSF) samples of patients with MB. Furthermore, cfDNA from CSF can interrogate for tumor-associated molecular clues. MB-associated alterations from CSF, tumor, and post-chemotherapy plasma were compared by deep sequencing on next-generation sequencing platform. Shared alterations exist between CSF and matched tumor tissues. More alternations were detected in circulating tumor DNA from CSF than those in genomic DNA from primary tumor. It was feasible to detect MB-associated mutations in plasma of patients treated with chemotherapy. Collectively, CSF supernatant can be used to monitor genomic alterations, as a superior technique as long as tumor-derived cfDNA can be isolated from CSF successfully.

Medulloblastoma during pregnancy: Hormone-mediated association? Report of 2 cases.

OBJECTIVE: To report two rare cases of medulloblastoma in pregnant patients and a review of the literature. MATERIAL AND METHODS: Report of patients diagnosed with medulloblastoma during their pregnancies, who were treated with surgery and adjuvant therapy. We also reviewed other cases reported in the literature and the association made with hormonal receptors. RESULTS: Brain tumors in coincidence with pregnancy are unusual, and the incidence of medulloblastoma in pregnancy is still rarer. We found 8 cases of medulloblastomas diagnosed during pregnancy. Reports suggest that hormonal changes and increases in the levels of growth factors and angiogenic factors during pregnancy influence the rate of growth of brain tumors (not only medulloblastomas but also meningiomas or glial tumors). CONCLUSIONS: The uniqueness of these cases is their rarity. The symptoms are usually masked by the symptoms of pregnancy. At present, there is still little evidence regarding the pathogenesis and treatment of medulloblastoma in pregnancy.

A Multi-institutional Comparative Analysis of Proton and Photon Therapy-Induced Hematologic Toxicity in Patients With Medulloblastoma.

PURPOSE: This multi-institutional retrospective study sought to examine the hematologic effects of craniospinal irradiation (CSI) in pediatric patients with medulloblastoma using proton or photon therapy. METHODS AND MATERIALS: Clinical and treatment characteristics were recorded for 97 pediatric patients with medulloblastoma who received CSI without concurrent chemotherapy or with concurrent single-agent vincristine from 2000 to 2017. Groups of 60 and 37 patients underwent treatment with proton-based and photon-based therapy, respectively. Overall survival was determined by Kaplan-Meier curves with log-rank test. Comparisons of blood counts at each timepoint were conducted using multiple t tests with Bonferroni corrections. Univariate and multivariate analyses of time to grade ≥3 hematologic toxicity were performed with Cox regression analyses. RESULTS: Median age of patients receiving proton and photon CSI was 7.5 years (range, 3.5-22.7 years) and 9.9 years (range, 3.6-19.5 years), respectively. Most patients had a diagnosis of standard risk medulloblastoma, with 86.7% and 89.2% for the proton and photon cohorts, respectively. Median total dose to involved field or whole posterior fossa was 54.0 Gy/Gy relative biological effectiveness (RBE) and median CSI dose was 23.4 Gy/Gy(RBE) (range, 18-36 Gy/Gy[RBE]) for both cohorts. Counts were significantly higher in the proton cohort compared with the photon cohort in weeks 3 to 6 of radiation therapy (RT). Although white blood cell counts did not differ between the 2 cohorts, patients receiving proton RT had significantly higher lymphocyte counts throughout the RT course. Similar results were observed when excluding patients who received vertebral body sparing proton RT or limiting to those receiving 23.4 Gy. Only photon therapy was associated with decreased time to grade ≥3 hematologic toxicity on univariate and multivariable analyses. No difference in overall survival was observed, and lymphopenia did not predict survival. CONCLUSIONS: Patients who receive CSI using proton therapy experience significantly decreased hematologic toxicity compared with those receiving photon therapy.

Metabolic Fingerprinting on Synthetic Alloys for Medulloblastoma Diagnosis and Radiotherapy Evaluation.

Diagnostics is the key in screening and treatment of cancer. As an emerging tool in precision medicine, metabolic analysis detects end products of pathways, and thus is more distal than proteomic/genetic analysis. However, metabolic analysis is far from ideal in clinical diagnosis due to the sample complexity and metabolite abundance in patient specimens. A further challenge is real-time and accurate tracking of treatment effect, e.g., radiotherapy. Here, Pd-Au synthetic alloys are reported for mass-spectrometry-based metabolic fingerprinting and analysis, toward medulloblastoma diagnosis and radiotherapy evaluation. A core-shell structure is designed using magnetic core particles to support Pd-Au alloys on the surface. Optimized synthetic alloys enhance the laser desorption/ionization efficacy and achieve direct detection of 100 nL of biofluids in seconds. Medulloblastoma patients are differentiated from healthy controls with average diagnostic sensitivity of 94.0%, specificity of 85.7%, and accuracy of 89.9%, by machine learning of metabolic fingerprinting. Furthermore, the radiotherapy process of patients is monitored and a preliminary panel of serum metabolite biomarkers is identified with gradual changes. This work will lead to the application-driven development of novel materials with tailored structural design and establishment of new protocols for precision medicine in near future.

Proteome and miRNome profiling of microvesicles derived from medulloblastoma cell lines with stem-like properties reveals biomarkers of poor prognosis.

Primary central nervous system (CNS) tumors are the most common deadly childhood cancer. Several patients with medulloblastoma experience local or metastatic recurrences after standard treatment, a condition associated with very poor prognosis. Current neuroimaging techniques do not accurately detect residual stem-like medulloblastoma cells promoting tumor relapses. In attempt to identify candidate tumor markers that could be circulating in blood or cerebrospinal (CSF) fluid of patients, we evaluated the proteome and miRNome content of extracellular microvesicles (MVs) released by highly-aggressive stem-like medulloblastoma cells overexpressing the pluripotent factor OCT4A. These cells display enhanced tumor initiating capability and resistance to chemotherapeutic agents. A common set of 464 proteins and 10 microRNAs were exclusively detected in MVs of OCT4A-overexpressing cells from four distinct medulloblastoma cell lines, DAOY, CHLA-01-MED, D283-MED, and USP13-MED. The interactome mapping of these exclusive proteins and miRNAs revealed ERK, PI3K/AKT/mTOR, EGF/EGFR, and stem cell self-renewal as the main oncogenic signaling pathways altered in these aggressive medulloblastoma cells. Of these MV cargos, four proteins (UBE2M, HNRNPCL2, HNRNPCL3, HNRNPCL4) and five miRNAs (miR-4449, miR-500b, miR-3648, miR-1291, miR-3607) have not been previously reported in MVs from normal tissues and in CSF. These proteins and miRNAs carried within MVs might serve as biomarkers of aggressive stem-like medulloblastoma cells to improve clinical benefit by helping refining diagnosis, patient stratification, and early detection of relapsed disease.

Exosomal miR-130b-3p targets SIK1 to inhibit medulloblastoma tumorigenesis.

Exosomes are an important carrier for cell communication. miRNAs in exosomes are potential biomarkers and therapeutic targets in different types of cancer. However, the role of exosomal miRNAs in medulloblastoma (MB) patients is largely unknown. In this study, we reported that there was a higher level of miR-130b-3p in exosomes derived from MB patient plasma compared with exosomes from healthy control plasma. Exosomes from MB patient plasma could transfer miR-130b-3p to an MB cell line and played suppressor roles for cell proliferation. miR-130b-3p suppressed MB tumorigenesis by targeting a previously unknown target, serine/threonine-protein kinase 1 (SIK1), through the p53 signaling pathways. In addition, we found an unreported role of SIK1 in promoting MB tumor growth and an SIK1 inhibitor could inhibit MB cell proliferation. This research provides new insight into the molecular mechanism of MB and may provide a new therapeutic strategy for MB treatment.

Pilot study of DNA methylation-derived neutrophil-to-lymphocyte ratio and survival in pediatric medulloblastoma.

INTRODUCTION: Methylation-derived neutrophil-to-lymphocyte ratio (mdNLR) has been identified as a potential prognostic biomarker of outcomes in various cancers. We evaluated the prognostic value of blood-derived mdNLR within a retrospective cohort of pediatric medulloblastoma patients. MATERIALS AND METHODS: DNA methylation was measured in archival peripheral blood samples collected on 56 pediatric medulloblastoma patients. Hazard ratios (HR) and 95% confidence intervals (CI) for the association between mdNLR and survival were evaluated using Cox proportional hazard models. RESULTS: Compared to patients who were alive at last follow-up (n = 43), the mean mdNLR value was slightly higher in deceased patients (n = 13) (12.3 vs. 5.2,P = 0.163). Elevated log-transformed mdNLR was suggestively associated with an increased likelihood of death in unadjusted models (HR=1.43, 95%CI: 0.92-2.22) and significantly associated with mortality in adjusted models (HR=1.61, 95%CI: 1.01-2.58). DISCUSSION: Future work is warranted to investigate the relationship between mdNLR outcomes in specific pediatric medulloblastoma molecular subgroups.

Various components of the insulin-like growth factor system in tumor tissue, cerebrospinal fluid and peripheral blood of pediatric medulloblastoma and ependymoma patients.

The insulin-like growth factor (IGF) system plays an important role in neuronal development and may contribute to the development of brain tumors. In this study, we studied mRNA expression levels of IGFs, insulin-like growth factor binding proteins (IGFBPs) and insulin-like growth factor receptors (IGFRs) in 27 pediatric medulloblastomas, 13 pediatric ependymomas and 5 control cerebella. Compared to normal cerebellum, mRNA levels of IGFBP-2 and IGFBP-3 were significantly increased in medulloblastomas and ependymomas. IGFBP-2 expression was indicative of poor prognosis in medulloblastomas, whereas IGFBP-3 mRNA levels were especially high in anaplastic ependymomas. IGFBP-5 and IGF-II mRNA levels were significantly increased in ependymomas compared to control cerebellum. Protein expression levels of IGFs and IGFBPs were analyzed in the cerebrospinal fluid (CSF) of 16 medulloblastoma, 4 ependymoma and 23 control patients by radioimmuno assay to determine whether they could be used as markers for residual disease after surgery. No aberrant CSF protein expression levels were found for ependymoma patients. In medulloblastoma patients, the IGFBP-3 protein levels were significantly higher than in ependymoma patients and controls. Moreover, enhanced levels of proteolytic fragments of IGFBP-3 were found in the CSF of medulloblastoma patients, being in concordance with a significantly increased IGFBP-3 proteolytic activity in the CSF of these patients. In conclusion, our data suggest that the IGF system is of importance in pediatric medulloblastomas and ependymomas. Larger studies should be conducted to validate the predictive values of the levels of intact IGFBP-3 and proteolytic fragments in CSF in the follow-up of medulloblastomas.

Development and validation of a sensitive LC MS/MS method for the measurement of the checkpoint kinase 1 inhibitor prexasertib and its application in a cerebral microdialysis study.

LC MS/MS methods to measure prexasertib in mouse plasma and Ringer's solution containing 0.5% BSA (Ringer's/BSA) were developed and validated. Liquid-liquid extraction with tert-butyl methyl ether was used to extract prexasertib from mouse plasma and Ringer's/BSA. Reverse phase chromatography with gradient elution was performed to separate prexasertib from the endogenous interference in the matrix, followed by MS detection using positive ion MRM mode. The initial calibration curve for mouse plasma samples ranged from 1 to 500 ng/ml, and after validation of that curve and use in a preliminary study another calibration curve (0.2-200 ng/ml) was created to enable the quantitation of prexasertib at lower concentrations. The method described was precise and accurate with %CV in precision studies of ≤ 6.7% and accuracies within 95.0-110% of nominal target concentration across all concentrations tested for both matrices. This validated method was successfully applied in the analysis of prexasertib in mouse plasma and dialysate samples collected during a cerebral microdialysis study.