Medulloblastoma is a malignant childhood cerebellar tumour comprised of distinct molecular subgroups. Whereas genomic characteristics of these subgroups are well defined, the extent to which cellular diversity underlies their divergent biology and clinical behaviour remains largely unexplored. We used single-cell transcriptomics to investigate intra-and inter-tumoural heterogeneity in twenty-five medulloblastomas spanning all molecular subgroups. WNT, SHH, and Group 3 tumours comprised subgroup-specific undifferentiated and differentiated neuronallike malignant populations, whereas Group 4 tumours were exclusively comprised of differentiated neuronal-like neoplastic cells. SHH tumours closely resembled granule neurons of varying differentiation states that correlated with patient age. Group 3 and Group 4 tumours exhibited a developmental trajectory from primitive progenitor-like to more mature neuronal-like cells, whose relative proportions distinguished these subgroups. Cross-species transcriptomics defined distinct glutamatergic populations as putative cells-of-origin for SHH and Group 4 subtypes. Collectively, these data provide novel insights into the cellular and developmental states underlying subtypespecific medulloblastoma biology. Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
Primary diffuse leptomeningeal melanomatosis (PDLMM) is an extremely rare and aggressive cancer type for which best treatment strategies remain to be elucidated. Herein, we present current and prospective diagnostic strategies and treatment management of PDLMM. Against the background of an extensive literature review of published PDLMM cases and currently employed therapeutic strategies, we present an illustrative case of a pediatric patient suffering from PDLMM. We report the first case of a pediatric patient with PDLMM who received combination treatment including trametinib and everolimus, followed by intravenous nivolumab and ipilimumab with concomitant intensive intraventricular chemotherapy, resulting in temporary significant clinical improvement and overall survival of 7 months. Following this clinical experience, we performed a comprehensive literature review, identifying 26 additional cases. By these means, we provide insight into current knowledge on clinical and molecular characteristics of PDLMM. Analysis of these cases revealed that the unspecific clinical presentation, such as unrecognized increased intracranial pressure (present in 67%), is a frequent reason for the delay in diagnosis. Mortality remains substantial despite diverse therapeutic approaches with a median overall survival of 4 months from diagnosis. On the molecular level, to date, the only oncogenic driver reported so far is mutation of NRAS (n = 3), underlining a close biological relation to malignant melanoma and neurocutaneous melanosis. We further show, for the first time, that this somatic mutation can be exploited for cerebrospinal fluid liquid biopsy detection, revealing a novel potential biomarker for diagnosis and monitoring of PDLMM. Last, we use a unique patient derived PDLMM cell model to provide first insights into in vitro drug sensitivities. In summary, we provide future diagnostic and therapeutic guidance for PDLMM and first insights into the use of liquid biopsy and in vitro models for this orphan cancer type.
Medulloblastoma (MB) recurrence is usually incurable despite intensive therapy including high-dose chemotherapy. An evolving alternative approach to conventional chemotherapy aims at interfering with tumor angiogenesis at different levels. We report on a novel combinatorial metronomic antiangiogenic approach. The study is a retrospective observational study of 29 consecutive patients with first or multiple recurrences prospectively treated according to the MEMMAT strategy (“MEMMAT-like”) before the formal protocol (MEMMAT; ClinicalTrials.gov Identifier: NCT01356290) started. The study period was 11/2006 to 06/2016. Treatment consisted of daily oral thalidomide, fenofibrate, celecoxib, and alternating 21-day cycles of low-dose oral etoposide and cyclophosphamide supplemented by IV bevacizumab and intraventricular therapy consisting of alternating etoposide and liposomal cytarabine. Median overall survival (OS) after recurrence for the whole group was 29.5 months, OS was 48.3 ± 9.3% at three years and 34.5 ± 8.8% at five years, and progression-free survival was 42.0 ± 9.5% at three years and 29.4 ± 9% at five years. As of 07/2022, 9/29 patients are alive 86 to 164 months after the recurrence that prompted the “MEMMAT-like” therapy. Treatment was primarily out-patient and generally well-tolerated. Toxicities did occur but were manageable. In conclusion, antiangiogenic therapy according to the MEMMAT strategy increased median OS of patients with recurrent MB and may lead to long-term survival. Adherence to the protocol, including intraventricular therapy, appears important.
In the era of precision oncology, rapid molecular profiling as well as continuous monitoring of response to treatment or relapse are of increasing importance. We investigated digital droplet (dd)PCR for cerebrospinal fluid (CSF) derived cell-free (cf)DNA detection as a new method for rapid diagnosing of MYC/MYCN amplification in CNS malignancies - a patient collective with a dismal prognosis. Wet lab validated ddPCR probes for MYC were first investigated in D425 cells, a human medulloblastoma cell line with confirmed MYC amplification. Results of the methylation array of patients with stored CSF/serum samples (-80°C) were screened for patients with MYC/MYCN amplification. Five patients with medulloblastoma (group 3/4) and MYC-amplification and one patient with a diffuse glioma and MYCN-amplification were included in this study. ddPCR was performed on cfDNA isolated from CSF or serum. MYC amplification was detected by ddPCR in 28/33 (85%) CSF samples, with 4/5 negative samples being from one patient, and only one sample showing an unsuccessful analysis. MYC amplification was detectable in all longitudinal samples in 4/5 patients. 1/1 sample from the patient with MYCN amplific ation was positive in ddPCR. We were not able to detect MYC amplification in serum samples. Importantly, a turn-around time of only six hours from sample thawing/acquisition to result generation was easily achievable. Concluding, detection of MYC/MYCN-amplification in CSF by ddPCR is feasible in the clinical setting and allows for a rapid molecular diagnosis. MYC-amplification was constantly detectable in 4/5 patients with longitudinal CSF samples, which is in-line with the tumor burden our patients suffered from. Interestingly, the detectability in the patient’s serum was low, presumably due to the lower percentage of cell-free tumor (ct)DNA in serum when compared to CSF. Our results render ddPCR as a promising tool for bed-side molecular diagnosis and disease monitoring.
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