Disseminated Medulloblastoma in a Child with Germline BRCA2 6174delT Mutation and without Fanconi Anemia

Do Patients With Hypoallergenic Total Knee Arthroplasty Implants for Metal Allergy Do Worse? An Analysis of Health Care Utilizations and Patient-Reported Outcome Measures

BACKGROUND

Metal allergy is a rare and controversial cause of implant failure and poor outcomes following total knee arthroplasty (TKA). Few studies have investigated clinical and patient-reported outcome measures (PROMs) in patients treated with hypoallergenic implants. This investigation aimed to compare: (1) health care utilizations (eg, hospital length of stay, 90-day readmission rate, and incidence of nonhome discharge) and (2) 1-year PROMs between patients who received hypoallergenic and standard TKA implants.

METHODS

This was a retrospective review of prospectively collected data from patients who underwent primary TKA between 2018 and 2019. Propensity score matching (3:1) was used to compare standard TKA patients with those who received hypoallergenic TKA implants, respectively. Knee injury and Osteoarthritis Outcome Score (KOOS) pain, KOOS Physical function Shortform (PS), and Veterans RAND 12-Item Health Survey Mental Component Score were collected preoperatively and at 1-year. After matching, 190 hypoallergenic and 570 standard TKAs were analyzed.

RESULTS

No differences were observed in length of stay (P = .98), 90-day readmission (P = .89), and nonhome discharge (P = .82). Additionally, there was no significant difference in change from preoperative to 1-year PROMs (KOOS pain, P = .97; KOOS PS, P = .88; Veterans RAND 12-Item Health Survey Mental Component Score, P = .28). Patient-reported satisfaction was similar at 1-year (P = .23). Patients achieved similar rates of Patient Acceptable Symptom State (PASS) and minimal clinically important difference (MCID) for KOOS pain (PASS, P = .77; MCID, P = .33) and KOOS PS (PASS, P = .44; MCID, P = .65).

CONCLUSION

Patients treated with hypoallergenic TKA implants for suspected metal allergy had similar outcomes compared to patients who had standard implants and no metal allergy.

LIN28 expression and function in medulloblastoma

Medulloblastoma (MB) is the most common malignant pediatric brain tumor. Current treatment modalities are not completely effective and can lead to severe neurological and cognitive adverse effects. In addition to urgently needing better treatment approaches, new diagnostic and prognostic biomarkers are required to improve the therapy outcomes of MB patients. The RNA-binding proteins, LIN28A and LIN28B, are known to regulate invasive phenotypes in many different cancer types. However, the expression and function of these proteins in MB had not been studied to date. This study identified the expression of LIN28A and LIN28B in MB patient samples and cell lines and assessed the effect of LIN28 inhibition on MB cell growth, metabolism and stemness. LIN28B expression was significantly upregulated in MB tissues compared to normal brain tissues. This upregulation, which was not observed in other brain tumors, was specific for the aggressive MB subgroups and correlated with patient survival and metastasis rates. Functionally, pharmacological inhibition of LIN28 activity concentration-dependently reduced LIN28B expression, as well as the growth of D283 MB cells. While LIN28 inhibition did not affect the levels of intracellular ATP, it reduced the expression of the stemness marker CD133 in D283 cells and the sphere formation of CHLA-01R cells. LIN28B, which is highly expressed in the human cerebellum during the first few months after birth, subsequently decreased with age. The results of this study highlight the potential of LIN28B as a diagnostic and prognostic marker for MB and open the possibility to utilize LIN28 as a pharmacological target to suppress MB cell growth and stemness.

Drug Resistance in Medulloblastoma Is Driven by YB-1, ABCB1 and a Seven-Gene Drug Signature

Therapy resistance represents an unmet challenge in the treatment of medulloblastoma. Accordingly, the identification of targets that mark drug-resistant cell populations, or drive the proliferation of resistant cells, may improve treatment strategies. To address this, we undertook a targeted approach focused on the multi-functional transcription factor YB-1. Genetic knockdown of YB-1 in Group 3 medulloblastoma cell lines diminished cell invasion in 3D in vitro assays and increased sensitivity to standard-of-care chemotherapeutic vincristine and anti-cancer agents panobinostat and JQ1. For vincristine, this occurred in part by YB-1-mediated transcriptional regulation of multi-drug resistance gene ABCB1, as determined by chromatin immunoprecipitation. Whole transcriptome sequencing of YB-1 knockdown cells identified a role for YB-1 in the regulation of tumourigenic processes, including lipid metabolism, cell death and survival and MYC and mTOR pathways. Stable cisplatin- and vincristine-tolerant Group 3 and SHH cell lines were generated to identify additional mechanisms driving resistance to standard-of-care medulloblastoma therapy. Next-generation sequencing revealed a vastly different transcriptomic landscape following chronic drug exposure, including a drug-tolerant seven-gene expression signature, common to all sequenced drug-tolerant cell lines, representing therapeutically targetable genes implicated in the acquisition of drug tolerance. Our findings provide significant insight into mechanisms and genes underlying therapy resistance in medulloblastoma.

Dormant SOX9-Positive Cells Facilitate MYC-Driven Recurrence of Medulloblastoma

Relapse is the leading cause of death in patients with medulloblastoma, the most common malignant pediatric brain tumor. A better understanding of the mechanisms underlying recurrence could lead to more effective therapies for targeting tumor relapses. Here, we observed that SOX9, a transcription factor and stem cell/glial fate marker, is limited to rare, quiescent cells in high-risk medulloblastoma with MYC amplification. In paired primary-recurrent patient samples, SOX9-positive cells accumulated in medulloblastoma relapses. SOX9 expression anti-correlated with MYC expression in murine and human medulloblastoma cells. However, SOX9-positive cells were plastic and could give rise to a MYC high state. To follow relapse at the single-cell level, an inducible dual Tet model of medulloblastoma was developed, in which MYC expression was redirected in vivo from treatment-sensitive bulk cells to dormant SOX9-positive cells using doxycycline treatment. SOX9 was essential for relapse initiation and depended on suppression of MYC activity to promote therapy resistance, epithelial-mesenchymal transition, and immune escape. p53 and DNA repair pathways were downregulated in recurrent tumors, whereas MGMT was upregulated. Recurrent tumor cells were found to be sensitive to treatment with an MGMT inhibitor and doxorubicin. These findings suggest that recurrence-specific targeting coupled with DNA repair inhibition comprises a potential therapeutic strategy in patients affected by medulloblastoma relapse.

SIGNIFICANCE

SOX9 facilitates therapy escape and recurrence in medulloblastoma via temporal inhibition of MYC/MYCN genes, revealing a strategy to specifically target SOX9-positive cells to prevent tumor relapse.

Splicing-Disrupting Mutations in Inherited Predisposition to Solid Pediatric Cancer

The prevalence of hereditary cancer in children was estimated to be very low until recent studies suggested that at least 10% of pediatric cancer patients carry a germline mutation in a cancer predisposition gene. A significant proportion of pathogenic variants associated with an increased risk of hereditary cancer are variants affecting splicing. RNA splicing is an essential process involved in different cellular processes such as proliferation, survival, and differentiation, and alterations in this pathway have been implicated in many human cancers. Hereditary cancer genes are highly susceptible to splicing mutations, and among them there are several genes that may contribute to pediatric solid tumors when mutated in the germline. In this review, we have focused on the analysis of germline splicing-disrupting mutations found in pediatric solid tumors, as the discovery of pathogenic splice variants in pediatric cancer is a growing field for the development of personalized therapies. Therapies developed to correct aberrant splicing in cancer are also discussed as well as the options to improve the diagnostic yield based on the increase in the knowledge in splicing.

Inositol treatment inhibits medulloblastoma through suppression of epigenetic-driven metabolic adaptation

Deregulation of chromatin modifiers plays an essential role in the pathogenesis of medulloblastoma, the most common paediatric malignant brain tumour. Here, we identify a BMI1-dependent sensitivity to deregulation of inositol metabolism in a proportion of medulloblastoma. We demonstrate mTOR pathway activation and metabolic adaptation specifically in medulloblastoma of the molecular subgroup G4 characterised by a BMI1High;CHD7Low signature and show this can be counteracted by IP6 treatment. Finally, we demonstrate that IP6 synergises with cisplatin to enhance its cytotoxicity in vitro and extends survival in a pre-clinical BMI1High;CHD7Low xenograft model.

Molecular Profiling of Malignant Pleural Effusions with Next Generation Sequencing (NGS): Evidence that Supports Its Role in Cancer Management

Malignant pleural effusions (MPEs) often develop in advanced cancer patients and confer significant morbidity and mortality. In this review, we evaluated whether molecular profiling of MPEs with next generation sequencing (NGS) could have a role in cancer management, focusing on lung cancer. We reviewed and compared the diagnostic performance of pleural fluid liquid biopsy with other types of samples. When applied in MPEs, NGS may have comparable performance with corresponding tissue biopsies, yield higher DNA amount, and detect more genetic aberrations than blood-derived liquid biopsies. NGS in MPEs may also be preferable to plasma liquid biopsy in advanced cancer patients with a MPE and a paucicellular or it could be difficult to obtain tissue/fine-needle aspiration biopsy. Of interest, post-centrifuge supernatant NGS may exhibit superior results compared to cell pellet, cell block or other materials. NGS in MPEs can also guide clinicians in tailoring established therapies and identifying therapy resistance. Evidence is still premature regarding the role of NGS in MPEs from patients with cancers other than lung. We concluded that MPE processing could provide useful prognostic and theranostic information, besides its diagnostic role.

Genetic Predisposition to Solid Pediatric Cancers

Progresses over the past years have extensively improved our capacity to use genome-scale analyses—including high-density genotyping and exome and genome sequencing—to identify the genetic basis of pediatric tumors. In particular, exome sequencing has contributed to the evidence that about 10% of children and adolescents with tumors have germline genetic variants associated with cancer predisposition. In this review, we provide an overview of genetic variations predisposing to solid pediatric tumors (medulloblastoma, ependymoma, astrocytoma, neuroblastoma, retinoblastoma, Wilms tumor, osteosarcoma, rhabdomyosarcoma, and Ewing sarcoma) and outline the biological processes affected by the involved mutated genes. A careful description of the genetic basis underlying a large number of syndromes associated with an increased risk of pediatric cancer is also reported. We place particular emphasis on the emerging view that interactions between germline and somatic alterations are a key determinant of cancer development. We propose future research directions, which focus on the biological function of pediatric risk alleles and on the potential links between the germline genome and somatic changes. Finally, the importance of developing new molecular diagnostic tests including all the identified risk germline mutations and of considering the genetic predisposition in screening tests and novel therapies is emphasized.

Patient-Derived Orthotopic Xenograft Models of Pediatric Brain Tumors: In a Mature Phase or Still in Its Infancy?

In recent years, molecular profiling has led to the discovery of an increasing number of brain tumor subtypes, and associated therapeutic targets. These molecular features have been incorporated in the 2016 new World Health Organization (WHO) Classification of Tumors of the Central Nervous System (CNS), which now distinguishes tumor subgroups not only histologically, but also based on molecular characteristics. Despite an improved diagnosis of (pediatric) tumors in the CNS however, the survival of children with malignant brain tumors still is far worse than for those suffering from other types of malignancies. Therefore, new treatments need to be developed, based on subgroup-specific genetic aberrations. Here, we provide an overview of the currently available orthotopic xenograft models for pediatric brain tumor subtypes as defined by the 2016 WHO classification, to facilitate the choice of appropriate animal models for the preclinical testing of novel treatment strategies, and to provide insight into the current gaps and challenges.

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.

Inhibition of Rho-Associated Kinase Suppresses Medulloblastoma Growth

Medulloblastoma is one of the most common malignant brain tumor types in children, with an overall survival of 70%. Mortality is associated with metastatic relapsed tumors. Rho-associated kinases (ROCKs), important for epithelial-mesenchymal transition (EMT) and proper nervous system development, have previously been identified as a promising drug target to inhibit cancer growth and metastatic spread. Here, we show that ROCKs are expressed in medulloblastoma, with higher ROCK2 mRNA expression in metastatic compared to non-metastatic tumors. By evaluating three ROCK inhibitors in a panel of medulloblastoma cell lines we demonstrated that medulloblastoma cells were sensitive for pharmacological ROCK inhibition. The specific ROCK inhibitor RKI-1447 inhibited the tumorigenicity in medulloblastoma cells as well as impeded cell migration and invasion. Differential gene expression analysis suggested that ROCK inhibition was associated with the downregulation of signaling pathways important in proliferation and metastasis e.g., TNFα via NFκβ, TGFβ, and EMT. Expression of key proteins in these pathways such as RHOA, RHOB, JUN, and vimentin was downregulated in ROCK inhibited cells. Finally, we showed that ROCK inhibition by RKI-1447 suppressed medulloblastoma growth and proliferation in vivo. Collectively, our results suggest that ROCK inhibition presents a potential new therapeutic option in medulloblastoma, especially for children with metastatic disease.

Preclinical Models of Pediatric Brain Tumors-Forging Ahead

Approximately five out of 100,000 children from 0 to 19 years old are diagnosed with a brain tumor. These children are treated with medication designed for adults that are highly toxic to a developing brain. Those that survive are at high risk for a lifetime of limited physical, psychological, and cognitive abilities. Despite much effort, not one drug exists that was designed specifically for pediatric patients. Stagnant government funding and the lack of economic incentives for the pharmaceutical industry greatly limits preclinical research and the development of clinically applicable pediatric brain tumor models. As more data are collected, the recognition of disease sub-groups based on molecular heterogeneity increases the need for designing specific models suitable for predictive drug screening. To overcome these challenges, preclinical approaches will need continual enhancement. In this review, we examine the advantages and shortcomings of in vitro and in vivo preclinical pediatric brain tumor models and explore potential solutions based on past, present, and future strategies for improving their clinical relevancy.

Spectrum and prevalence of genetic predisposition in medulloblastoma: a retrospective genetic study and prospective validation in a clinical trial cohort

BACKGROUND

Medulloblastoma is associated with rare hereditary cancer predisposition syndromes; however, consensus medulloblastoma predisposition genes have not been defined and screening guidelines for genetic counselling and testing for paediatric patients are not available. We aimed to assess and define these genes to provide evidence for future screening guidelines.

METHODS

In this international, multicentre study, we analysed patients with medulloblastoma from retrospective cohorts (International Cancer Genome Consortium [ICGC] PedBrain, Medulloblastoma Advanced Genomics International Consortium [MAGIC], and the CEFALO series) and from prospective cohorts from four clinical studies (SJMB03, SJMB12, SJYC07, and I-HIT-MED). Whole-genome sequences and exome sequences from blood and tumour samples were analysed for rare damaging germline mutations in cancer predisposition genes. DNA methylation profiling was done to determine consensus molecular subgroups: WNT (MBWNT), SHH (MBSHH), group 3 (MBGroup3), and group 4 (MBGroup4). Medulloblastoma predisposition genes were predicted on the basis of rare variant burden tests against controls without a cancer diagnosis from the Exome Aggregation Consortium (ExAC). Previously defined somatic mutational signatures were used to further classify medulloblastoma genomes into two groups, a clock-like group (signatures 1 and 5) and a homologous recombination repair deficiency-like group (signatures 3 and 8), and chromothripsis was investigated using previously established criteria. Progression-free survival and overall survival were modelled for patients with a genetic predisposition to medulloblastoma.

FINDINGS

We included a total of 1022 patients with medulloblastoma from the retrospective cohorts (n=673) and the four prospective studies (n=349), from whom blood samples (n=1022) and tumour samples (n=800) were analysed for germline mutations in 110 cancer predisposition genes. In our rare variant burden analysis, we compared these against 53 105 sequenced controls from ExAC and identified APC, BRCA2, PALB2, PTCH1, SUFU, and TP53 as consensus medulloblastoma predisposition genes according to our rare variant burden analysis and estimated that germline mutations accounted for 6% of medulloblastoma diagnoses in the retrospective cohort. The prevalence of genetic predispositions differed between molecular subgroups in the retrospective cohort and was highest for patients in the MBSHH subgroup (20% in the retrospective cohort). These estimates were replicated in the prospective clinical cohort (germline mutations accounted for 5% of medulloblastoma diagnoses, with the highest prevalence [14%] in the MBSHH subgroup). Patients with germline APC mutations developed MBWNT and accounted for most (five [71%] of seven) cases of MBWNT that had no somatic CTNNB1 exon 3 mutations. Patients with germline mutations in SUFU and PTCH1 mostly developed infant MBSHH. Germline TP53 mutations presented only in childhood patients in the MBSHH subgroup and explained more than half (eight [57%] of 14) of all chromothripsis events in this subgroup. Germline mutations in PALB2 and BRCA2 were observed across the MBSHH, MBGroup3, and MBGroup4 molecular subgroups and were associated with mutational signatures typical of homologous recombination repair deficiency. In patients with a genetic predisposition to medulloblastoma, 5-year progression-free survival was 52% (95% CI 40-69) and 5-year overall survival was 65% (95% CI 52-81); these survival estimates differed significantly across patients with germline mutations in different medulloblastoma predisposition genes.

INTERPRETATION

Genetic counselling and testing should be used as a standard-of-care procedure in patients with MBWNT and MBSHH because these patients have the highest prevalence of damaging germline mutations in known cancer predisposition genes. We propose criteria for routine genetic screening for patients with medulloblastoma based on clinical and molecular tumour characteristics.

FUNDING

German Cancer Aid; German Federal Ministry of Education and Research; German Childhood Cancer Foundation (Deutsche Kinderkrebsstiftung); European Research Council; National Institutes of Health; Canadian Institutes for Health Research; German Cancer Research Center; St Jude Comprehensive Cancer Center; American Lebanese Syrian Associated Charities; Swiss National Science Foundation; European Molecular Biology Organization; Cancer Research UK; Hertie Foundation; Alexander and Margaret Stewart Trust; V Foundation for Cancer Research; Sontag Foundation; Musicians Against Childhood Cancer; BC Cancer Foundation; Swedish Council for Health, Working Life and Welfare; Swedish Research Council; Swedish Cancer Society; the Swedish Radiation Protection Authority; Danish Strategic Research Council; Swiss Federal Office of Public Health; Swiss Research Foundation on Mobile Communication; Masaryk University; Ministry of Health of the Czech Republic; Research Council of Norway; Genome Canada; Genome BC; Terry Fox Research Institute; Ontario Institute for Cancer Research; Pediatric Oncology Group of Ontario; The Family of Kathleen Lorette and the Clark H Smith Brain Tumour Centre; Montreal Children's Hospital Foundation; The Hospital for Sick Children: Sonia and Arthur Labatt Brain Tumour Research Centre, Chief of Research Fund, Cancer Genetics Program, Garron Family Cancer Centre, MDT's Garron Family Endowment; BC Childhood Cancer Parents Association; Cure Search Foundation; Pediatric Brain Tumor Foundation; Brainchild; and the Government of Ontario.

Proteomic profiling of isogenic primary and metastatic medulloblastoma cell lines reveals differential expression of key metastatic factors

Medulloblastoma is the most common malignant brain tumor in children. Around 30% of medulloblastoma patients are diagnosed with metastasis, which often results in a poor prognosis. Unfortunately, molecular mechanisms of medulloblastoma metastasis remain largely unknown. In this study, we employed the recently developed deep proteome analysis approach to quantitatively profile the expression of >10,000 proteins from CHLA-01-MED and CHLA-01R-MED isogenic cell lines derived from the primary and metastatic tumor of the same patient diagnosed with a group IV medulloblastoma. Using statistical analysis, we identified ~1400 significantly altered proteins between the primary and metastatic cell lines including known factors such as placental growth factor (PLGF), LIM homeobox 1 (LHX1) and prominim 1 (PROM1), as well as the negative regulator secreted protein acidic and cysteine rich (SPARC). Additional transwell experiments and immunohistochemical analysis of clinical medulloblastoma samples implicated yes-associated protein 1 (YAP1) as a potential key factor contributing to metastasis. Taken together, our data broadly defines the metastasis-relevant regulated proteome and provides a precious resource for further investigating potential mechanisms of medulloblastoma metastasis.

SIGNIFICANCE

This study represented the first deep proteome analysis of metastatic medulloblastomas and provided a valuable candidate list of altered proteins in metastatic medulloblastomas. The primary data suggested YAP1 as a potential driver for the metastasis of medulloblastoma. These results open up numerous avenues for further investigating the underlying mechanisms of medulloblastoma metastasis and improving the prognosis of medulloblastoma patients.

In vitro models of medulloblastoma: Choosing the right tool for the job

The recently-defined four molecular subgroups of medulloblastoma have required updating of our understanding of in vitro models to include molecular classification and risk stratification features from clinical practice. This review seeks to build a more comprehensive picture of the in vitro systems available for modelling medulloblastoma. The subtype classification and molecular characterisation for over 40 medulloblastoma cell-lines has been compiled, making it possible to identify the strengths and weaknesses in current model systems. Less than half (18/44) of established medulloblastoma cell-lines have been subgrouped. The majority of the subgrouped cell-lines (11/18) are Group 3 with MYC-amplification. SHH cell-lines are the next most common (4/18), half of which exhibit TP53 mutation. WNT and Group 4 subgroups, accounting for 50% of patients, remain underrepresented with 1 and 2 cell-lines respectively. In vitro modelling relies not only on incorporating appropriate tumour cells, but also on using systems with the relevant tissue architecture and phenotype as well as normal tissues. Novel ways of improving the clinical relevance of in vitro models are reviewed, focusing on 3D cell culture, extracellular matrix, co-cultures with normal cells and organotypic slices. This paper champions the establishment of a collaborative online-database and linked cell-bank to catalyse preclinical medulloblastoma research.