Characterization of medulloblastoma in Fanconi Anemia: a novel mutation in the BRCA2 gene and SHH molecular subgroup

Multidisciplinary approaches to study anaemia with special mention on aplastic anaemia (Review)

Anaemia is a common health problem worldwide that disproportionately affects vulnerable groups, such as children and expectant mothers. It has a variety of underlying causes, some of which are genetic. A comprehensive strategy combining physical examination, laboratory testing (for example, a complete blood count), and molecular tools for accurate identification is required for diagnosis. With nearly 400 varieties of anaemia, accurate diagnosis remains a challenging task. Red blood cell abnormalities are largely caused by genetic factors, which means that a thorough understanding requires interpretation at the molecular level. As a result, precision medicine has become a key paradigm, utilising artificial intelligence (AI) techniques, such as deep learning and machine learning, to improve prognostic evaluation, treatment prediction, and diagnostic accuracy. Furthermore, exploring the immunomodulatory role of vitamin D along with biomarker‑based molecular techniques offers promising avenues for insight into anaemia's pathophysiology. The intricacy of aplastic anaemia makes it particularly noteworthy as a topic deserving of concentrated molecular research. Given the complexity of anaemia, an integrated strategy integrating clinical, laboratory, molecular, and AI techniques shows a great deal of promise. Such an approach holds promise for enhancing global anaemia management options in addition to advancing our understanding of the illness.

Medulloblastomas Initiated by Homologous Recombination Defects in Mice

Germline mutations of homologous-recombination (HR) genes are among the top contributors to medulloblastomas. A significant portion of human medulloblastomas exhibit genomic signatures of HR defects. We queried whether ablation of Brca2 and Palb2, and their related Brca1 and Bccip genes, in the mouse brain can differentially initiate medulloblastomas. Conditional knockout mouse models of these HR genes and a conditional knockdown of Bccip (shBccip-KD) were established. Deletion of any of these genes led to microcephaly and neurologic defects, with Brca1- and Bccip- producing the worst. Trp53 co-deletion significantly rescued the microcephaly with Brca1, Palb2, and Brca2 deficiency but exhibited limited impact on Bccip- mice. For the first time, inactivation of either Brca1 or Palb2 with Trp53 was found to induce medulloblastomas. Despite shBccip-CKD being highly penetrative, Bccip/Trp53 deletions failed to induce medulloblastomas. The tumors displayed diverse immunohistochemical features and chromosome copy number variation. Although there were widespread up-regulations of cell proliferative pathways, most of the tumors expressed biomarkers of the sonic hedgehog subgroup. The medulloblastomas developed from Brca1-, Palb2-, and Brca2- mice were highly sensitive to a poly (ADP-ribose) polymerase inhibitor but not the ones from shBccip-CKD mice. These models recapitulate the spontaneous medulloblastoma development with high penetrance and a narrow time window, providing ideal platforms to test therapeutic agents with the ability to differentiate HR-defective and HR-proficient tumors.

G-quadruplexes are a source of vulnerability in BRCA2 deficient granule cell progenitors and medulloblastoma

Biallelic pathogenic variants in the essential DNA repair gene BRCA2 causes Fanconi anemia, complementation group FA-D1. Patients in this group are highly prone to develop embryonal tumors, most commonly medulloblastoma arising from the cerebellar granule cell progenitors (GCPs). GCPs undergo high proliferation in the postnatal cerebellum under SHH activation, but the type of DNA lesions that require the function of the BRCA2 to prevent tumorigenesis remains unknown. To identify such lesions, we assessed both GCP neurodevelopment and tumor formation using a mouse model with deletion of exons three and four of Brca2 in the central nervous system, coupled with global Trp53 loss. Brca2 Δex3-4 ;Trp53 -/- animals developed SHH subgroup medulloblastomas with complete penetrance. Whole-genome sequencing of the tumors identified structural variants with breakpoints enriched in areas overlapping G-quadruplexes (G4s). Brca2-deficient GCPs exhibited decreased replication speed in the presence of the G4-stabilizer pyridostatin. Pif1 helicase, which resolves G4s during replication, was highly upregulated in tumors, and Pif1 knockout in primary MB tumor cells resulted in increased genome instability upon pyridostatin treatment. These data suggest that G4s may represent sites prone to replication stalling in highly proliferative GCPs and without BRCA2, G4s become a source of genome instability. Tumor cells upregulate G4-resolving helicases to facilitate rapid proliferation through G4s highlighting PIF1 helicase as a potential therapeutic target for treatment of BRCA2-deficient medulloblastomas.

Germline biallelic BRCA2 pathogenic variants and medulloblastoma: an international cohort study

Constitutional heterozygous pathogenic variants in genes coding for some components of the Fanconi anemia-BRCA signaling pathway, which repairs DNA interstrand crosslinks, represent risk factors for common cancers, including breast, ovarian, pancreatic and prostate cancer. A high cancer risk is also a main clinical feature in patients with Fanconi anemia (FA), a rare condition characterized by bone marrow failure, endocrine and physical abnormalities. The mainly recessive condition is caused by germline pathogenic variants in one of 21 FA-BRCA pathway genes. Among patients with FA, the highest cancer risks are observed in patients with biallelic pathogenic variants in BRCA2 or PALB2. These patients develop a range of embryonal tumors and leukemia during the first decade of life, however, little is known about specific clinical, genetic and pathologic features or toxicities. Here, we present genetic, clinical, pathological and treatment characteristics observed in an international cohort of eight patients with FA due to biallelic BRCA2 pathogenic variants and medulloblastoma (MB), an embryonal tumor of the cerebellum. Median age at MB diagnosis was 32.5 months (range 7-58 months). All patients with available data had sonic hedgehog-MB. Six patients received chemotherapy and one patient also received proton radiation treatment. No life-threatening toxicities were documented. Prognosis was poor and all patients died shortly after MB diagnosis (median survival time 4.5 months, range 0-21 months) due to MB or other neoplasms. In conclusion, MB in patients with biallelic BRCA2 pathogenic variants is a lethal disease. Future experimental treatments are necessary to help these patients.

Newly Recognized Genetic Tumor Syndromes of the CNS in the 5th WHO Classification: Imaging Overview with Genetic Updates

The nervous system is commonly involved in a wide range of genetic tumor-predisposition syndromes. The classification of genetic tumor syndromes has evolved during the past years; however, it has now become clear that these syndromes can be categorized into a relatively small number of major mechanisms, which form the basis of the new 5th edition of the World Health Organization book (beta online version) on genetic tumor syndromes. For the first time, the World Health Organization has also included a separate chapter on genetic tumor syndromes in the latest edition of all the multisystem tumor series, including the 5th edition of CNS tumors. Our understanding of these syndromes has evolved rapidly since the previous edition (4th edition, 2016) with recognition of 8 new syndromes, including the following: Elongator protein complex-medulloblastoma syndrome, BRCA1-associated protein 1 tumor-predisposition syndrome, DICER1 syndrome, familial paraganglioma syndrome, melanoma-astrocytoma syndrome, Carney complex, Fanconi anemia, and familial retinoblastoma. This review provides a description of these new CNS tumor syndromes with a focus on imaging and genetic characteristics.

Double Heterozygosity for Rare Deleterious Variants in the BRCA1 and BRCA2 Genes in a Hungarian Patient with Breast Cancer

Hereditary breast cancer is most commonly attributed to germline BRCA1 and BRCA2 gene variants. The vast majority of BRCA1 and BRCA2 mutation carriers are single heterozygotes, and double heterozygosity (DH) is a very rare finding. Here, we describe the case of a BRCA1/BRCA2 double heterozygous female proband diagnosed with breast cancer. Genetic testing for hereditary breast and ovarian cancer revealed two pathogenic variants in the BRCA1 (c.5095C>T, p.(Arg1699Trp)) and in BRCA2 genes (c.658_659delGT, p.(Val220Ilefs*4)) in heterozygous form. None of the variants were founder Jewish mutations; to our knowledge, these rare deleterious variants have not been previously described in DH patients in the literature. The patient had triple-negative unilateral breast cancer at the age of 36 and 44 years. Based on family studies, the BRCA1 variant was maternally inherited.

Case report: Somatic mutations in microtubule dynamics-associated genes in patients with WNT-medulloblastoma tumors

Medulloblastoma (MB) is the most common pediatric brain tumor which accounts for about 20% of all pediatric brain tumors and 63% of intracranial embryonal tumors. MB is considered to arise from precursor cell populations present during an early brain development. Most cases (~70%) of MB occur at the age of 1-4 and 5-9, but are also infrequently found in adults. Total annual frequency of pediatric tumors is about 5 cases per 1 million children. WNT-subtype of MB is characterized by a high probability of remission, with a long-term survival rate of about 90%. However, in some rare cases there may be increased metastatic activity, which dramatically reduces the likelihood of a favorable outcome. Here we report two cases of MB with a histological pattern consistent with desmoplastic/nodular (DP) and classic MB, and genetically classified as WNT-MB. Both cases showed putative causal somatic protein truncating mutations identified in microtubule-associated genes: ARID2, TUBB4A, and ANK3.

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.

Polyclonal evolution of Fanconi anemia to MDS and AML revealed at single cell resolution

Background

Fanconi anemia (FA) is a rare disease of bone marrow failure. FA patients are prone to develop myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). However, the molecular clonal evolution of the progression from FA to MDS/AML remains elusive.

Methods

Herein, we performed a comprehensive genomic analysis using an FA patient (P1001) sample that transformed to MDS and subsequently AML, together with other three FA patient samples at the MDS stage.

Results

Our finding showed the existence of polyclonal pattern in these cases at MDS stage. The clonal evolution analysis of FA case (P1001) showed the mutations of UBASH3A, SF3B1, RUNX1 and ASXL1 gradually appeared at the later stage of MDS, while the IDH2 alteration become the dominant clone at the leukemia stage. Moreover, single-cell sequencing analyses further demonstrated a polyclonal pattern was present at either MDS or AML stages, whereas IDH2 mutated cell clones appeared only at the leukemia stage.

Conclusions

We thus propose a clonal evolution model from FA to MDS and AML for this patient. The results of our study on the clonal evolution and mutated genes of the progression of FA to AML are conducive to understanding the progression of the disease that still perplexes us.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40164-022-00319-5.

Care Coordination in a SARS-CoV-2-infected Child With Newly Diagnosed Medulloblastoma and Fanconi Anemia

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is responsible for a global pandemic that can cause severe infections in children, especially those with comorbid conditions. Here, we report a case of a child with a newly diagnosed medulloblastoma, Fanconi Anemia, and SARS-CoV-2 infection. Through multidisciplinary care coordination and meticulous planning, we were able to safely initiate this patient's oncology care and implement a long-term model to address the patient's care. This approach could be replicated with any newly diagnosed pediatric patient that requires monitoring for signs of COVID-19 with concurrent oncology care.

Signaling pathway deregulation and molecular alterations across pediatric medulloblastomas

Medulloblastomas (MBs) account for 15% of brain tumors in children under the age of 15. To date, the overall 5-year survival rate for all children is only around 60%. Recent advances in cancer genomics have led to a fundamental change in medulloblastoma classification and is evolving along with the genomic discoveries, allowing to regularly reclassify this disease. The previous molecular classification defined 4 groups (WNT-activated MB, SHH-activated MB and the groups 3 and 4 characterized partially by NMYC and MYC driven MBs). This stratification moved forward recently to better define these groups and their correlation to outcome. This new stratification into 7 novel subgroups was helpful to lay foundations and complementary data on the understanding regarding molecular pathways and gene mutations underlying medulloblastoma biology. This review was aimed at answering the recent key questions on MB genomics and go further in the relevance of those genes in MB development as well as in their targeted therapies.

Precision Therapy for Brain Tumors in Hereditary Syndromes

OPINION STATEMENT

Nervous system tumors arising in the setting of monogenic, hereditary cancer predisposition syndromes are unique in that the initiating genetic event in tumor formation is known. This knowledge provides a powerful treatment approach if the alteration or pathway can be targeted with a therapeutic agent. A reasonable argument can be made for the use of targeted agents in these tumor patients, even though many of them have FDA approval only for other tumor types. It is our practice to use and employ targeted therapy when standard treatments have failed or represent an unattractive option. Over time, however, targeted therapies will likely become first-line options.

Efficient embryonic homozygous gene conversion via RAD51-enhanced interhomolog repair

Searching for factors to improve knockin efficiency for therapeutic applications, biotechnology, and generation of non-human primate models of disease, we found that the strand exchange protein RAD51 can significantly increase Cas9-mediated homozygous knockin in mouse embryos through an interhomolog repair (IHR) mechanism. IHR is a hallmark of meiosis but only occurs at low frequencies in somatic cells, and its occurrence in zygotes is controversial. Using multiple approaches, we provide evidence for an endogenous IHR mechanism in the early embryo that can be enhanced by RAD51. This process can be harnessed to generate homozygotes from wild-type zygotes using exogenous donors and to convert heterozygous alleles into homozygous alleles without exogenous templates. Furthermore, we identify additional IHR-promoting factors and describe features of IHR events. Together, our findings show conclusive evidence for IHR in mouse embryos and describe an efficient method for enhanced gene conversion.

Genetic syndromes predisposing to pediatric brain tumors

The application of high-throughput sequencing approaches including paired tumor/normal sampling with therapeutic intent has demonstrated that 8%-19% of pediatric CNS tumor patients harbor a germline alteration in a classical tumor predisposition gene (NF1, P53). In addition, large-scale germline sequencing studies in unselected cohorts of pediatric neuro-oncology patients have demonstrated novel candidate tumor predisposition genes (ELP1 alterations in sonic hedgehog medulloblastoma). Therefore, the possibility of an underlying tumor predisposition syndrome (TPS) should be considered in all pediatric patients diagnosed with a CNS tumor which carries critical implications including accurate prognostication, selection of optimal therapy, screening, risk reduction, and family planning. The Pediatric Cancer Working Group of the American Association for Cancer Research (AACR) recently published consensus screening recommendations for children with the most common TPS. In this review, we provide an overview of the most relevant as well as recently identified TPS associated with the most frequently encountered pediatric CNS tumors with an emphasis on pathogenesis, genetic testing, clinical features, and treatment implications.

Downregulation of miR-326 and its host gene β-arrestin1 induces pro-survival activity of E2F1 and promotes medulloblastoma growth

Persistent mortality rates of medulloblastoma (MB) and severe side effects of the current therapies require the definition of the molecular mechanisms that contribute to tumor progression. Using cultured MB cancer stem cells and xenograft tumors generated in mice, we show that low expression of miR-326 and its host gene β-arrestin1 (ARRB1) promotes tumor growth enhancing the E2F1 pro-survival function. Our models revealed that miR-326 and ARRB1 are controlled by a bivalent domain, since the H3K27me3 repressive mark is found at their regulatory region together with the activation-associated H3K4me3 mark. High levels of EZH2, a feature of MB, are responsible for the presence of H3K27me3. Ectopic expression of miR-326 and ARRB1 provides hints into how their low levels regulate E2F1 activity. MiR-326 targets E2F1 mRNA, thereby reducing its protein levels; ARRB1, triggering E2F1 acetylation, reverses its function into pro-apoptotic activity. Similar to miR-326 and ARRB1 overexpression, we also show that EZH2 inhibition restores miR-326/ARRB1 expression, limiting E2F1 pro-proliferative activity. Our results reveal a new regulatory molecular axis critical for MB progression.

Cancer Predisposition Syndromes Associated With Pediatric High-Grade Gliomas

Pediatric High-Grade Gliomas (pHGG) are among the deadliest childhood brain tumors and can be associated with an underlying cancer predisposing syndrome. The thorough understanding of these syndromes can aid the clinician in their prompt recognition, leading to an informed genetic counseling for families and to a wider understanding of a specific genetic landscape of the tumor for target therapies. In this review, we summarize the main pHGG-associated cancer predisposing conditions, providing a guide for suspecting these syndromes and referring for genetic counseling.

Cancer Predisposition Syndromes and Medulloblastoma in the Molecular Era

Medulloblastoma is the most common malignant brain tumor in children. In addition to sporadic cases, medulloblastoma may occur in association with cancer predisposition syndromes. This review aims to provide a complete description of inherited cancer syndromes associated with medulloblastoma. We examine their epidemiological, clinical, genetic, and diagnostic features and therapeutic approaches, including their correlation with medulloblastoma. Furthermore, according to the most recent molecular advances, we describe the association between the various molecular subgroups of medulloblastoma and each cancer predisposition syndrome. Knowledge of the aforementioned conditions can guide pediatric oncologists in performing adequate cancer surveillance. This will allow clinicians to promptly diagnose and treat medulloblastoma in syndromic children, forming a team with all specialists necessary for the correct management of the other various manifestations/symptoms related to the inherited cancer syndromes.

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.

MRI features as a helpful tool to predict the molecular subgroups of medulloblastoma: state of the art

Medulloblastoma is the most common malignant pediatric brain tumor. Medulloblastoma should not be viewed as a single disease, but as a heterogeneous mixture of various subgroups with distinct characteristics. Based on genomic profiles, four distinct molecular subgroups are identified: Wingless (WNT), Sonic Hedgehog (SHH), Group 3 and Group 4. Each of these subgroups are associated with specific genetic aberrations, typical age of onset as well as survival prognosis. Magnetic resonance imaging (MRI) is performed for all patients with brain tumors, and has a key role in the diagnosis, surgical guidance and follow up of patients with medulloblastoma. Several studies indicate MRI as a promising tool for early detection of medulloblastoma subgroups. The early identification of the subgroup can influence the extent of surgical resection, radiotherapy and chemotherapy targeted treatments. In this article, we review the state of the art in MRI-facilitated medulloblastoma subgrouping, with a summary of the main MRI features in medulloblastoma and a brief discussion on molecular characterization of medulloblastoma subgroups. The main focus of the article is MRI features that correlate with medulloblastoma subtypes, as well as features suggestive of molecular subgroups. Finally, we briefly discuss the latest trends in MRI studies and latest developments in molecular characterization.

β-arrestin1-mediated acetylation of Gli1 regulates Hedgehog/Gli signaling and modulates self-renewal of SHH medulloblastoma cancer stem cells

Background

Aberrant Sonic Hedgehog/Gli (Hh/Gli) signaling pathway is a critical regulator of Sonic hedgehog medulloblastoma (SHH-MB). Cancer stem cells (CSCs), thought to be largely responsible for tumor initiation, maintenance, dissemination and relapse, have been identified in SHH-MB. Since we previously demonstrated that Hh/Gli signaling controls CSCs features in SHH-MB and that in these tumors miR-326 is down regulated, here we investigated whether there is a functional link between Hh/Gli signaling and miR-326.

Methods

We evaluated β-arrestin1 (Arrb1) and its intragenic miR-326 levels in CSCs derived from SHH-MB. Subsequently, we modulated the expression of Arrb1 and miR-326 in CSCs in order to gain insight into their biological role. We also analyzed the mechanism by which Arrb1 and miR-326 control Hh/Gli signaling and self-renewal, using luciferase and protein immunoprecipitation assays.

Results

Low levels of Arrb1 and miR-326 represent a feature of CSCs derived from SHH-MB. We observed that re-expression of Arrb1 and miR-326 inhibits Hh/Gli signaling pathway at multiple levels, which cause impaired proliferation and self-renewal, accompanied by down regulation of Nanog levels. In detail, miR-326 negatively regulates two components of the Hh/Gli pathway the receptor Smoothened (Smo) and the transcription factor Gli2, whereas Arrb1 suppresses the transcriptional activity of Gli1, by potentiating its p300-mediated acetylation.

Conclusions

Our results identify a new molecular mechanism involving miR-326 and Arrb1 as regulators of SHH-MB CSCs. Specifically, low levels of Arrb1 and miR-326 trigger and maintain Hh/Gli signaling and self-renewal.

The germline variants in DNA repair genes in pediatric medulloblastoma: a challenge for current therapeutic strategies

BACKGROUND

The defects in DNA repair genes are potentially linked to development and response to therapy in medulloblastoma. Therefore the purpose of this study was to establish the spectrum and frequency of germline variants in selected DNA repair genes and their impact on response to chemotherapy in medulloblastoma patients.

METHODS

The following genes were investigated in 102 paediatric patients: MSH2 and RAD50 using targeted gene panel sequencing and NBN variants (p.I171V and p.K219fs*19) by Sanger sequencing. In three patients with presence of rare life-threatening adverse events (AE) and no detected variants in the analyzed genes, whole exome sequencing was performed. Based on combination of molecular and immunohistochemical evaluations tumors were divided into molecular subgroups. Presence of variants was tested for potential association with the occurrence of rare life-threatening AE and other clinical features.

RESULTS

We have identified altogether six new potentially pathogenic variants in MSH2 (p.A733T and p.V606I), RAD50 (p.R1093*), FANCM (p.L694*), ERCC2 (p.R695C) and EXO1 (p.V738L), in addition to two known NBN variants. Five out of twelve patients with defects in either of MSH2, RAD50 and NBN genes suffered from rare life-threatening AE, more frequently than in control group (p = 0.0005). When all detected variants were taken into account, the majority of patients (8 out of 15) suffered from life-threatening toxicity during chemotherapy.

CONCLUSION

Our results, based on the largest systematic study performed in a clinical setting, provide preliminary evidence for a link between defects in DNA repair genes and treatment related toxicity in children with medulloblastoma. The data suggest that patients with DNA repair gene variants could need special vigilance during and after courses of chemotherapy.

Metastatic Group 3 Medulloblastoma in a Patient With Tuberous Sclerosis Complex: Case Description and Molecular Characterization of the Tumor

Medulloblastoma is the most common pediatric brain tumor. We describe a child with tuberous sclerosis complex that developed a Group 3, myc overexpressed, metastatic medulloblastoma (MB). Considering the high risk of treatment-induced malignancies, a tailored therapy, omitting radiation, was given. Based on the evidence of mammalian target of rapamycin mTORC, mTOR Complex; RAS, Rat sarcoma; RAF, rapidly accelerated fibrosarcoma (mTOR) pathway activation in the tumor, targeted therapy was applied resulting in complete remission of disease. Although the PI3K/AKT/mTOR signaling pathway plays a role in MB, we did not find TSC1/TSC2 (TSC, tuberous sclerosis complex) mutation in our patient. We speculate that a different pathway resulting in mTOR activation is the basis of both TSC and MB in this child; H&E, haematoxilin and eosin; Gd, gadolinium.

Non-canonical Hedgehog/AMPK-Mediated Control of Polyamine Metabolism Supports Neuronal and Medulloblastoma Cell Growth

Developmental Hedgehog signaling controls proliferation of cerebellar granule cell precursors (GCPs), and its aberrant activation is a leading cause of medulloblastoma. We show here that Hedgehog promotes polyamine biosynthesis in GCPs by engaging a non-canonical axis leading to the translation of ornithine decarboxylase (ODC). This process is governed by AMPK, which phosphorylates threonine 173 of the zinc finger protein CNBP in response to Hedgehog activation. Phosphorylated CNBP increases its association with Sufu, followed by CNBP stabilization, ODC translation, and polyamine biosynthesis. Notably, CNBP, ODC, and polyamines are elevated in Hedgehog-dependent medulloblastoma, and genetic or pharmacological inhibition of this axis efficiently blocks Hedgehog-dependent proliferation of medulloblastoma cells in vitro and in vivo. Together, these data illustrate an auxiliary mechanism of metabolic control by a morphogenic pathway with relevant implications in development and cancer.

Biallelic FANCD1/BRCA2 mutations predisposing to glioblastoma multiforme with multiple oncogenic amplifications

Fanconi anaemia (FA) caused by biallelic mutation in FANCD1/BRCA2 is rare but carries a high risk of early onset cancer. Medulloblastoma is well described in this cohort but reports of other brain tumours are uncommon. The molecular profile of tumours from FA patients is not well reported. A glioblastoma multiforme (GBM) from a 3-year-old patient with FA and confirmed biallelic BRCA2 mutations was submitted for methylation analysis. This revealed strong clustering with the K27 mutation subgroup and copy number analysis showed gains of chromosomes 1q, 4q, part of 7q, part of 8q and 17q with resultant amplifications of MDM4, CDK6, MET, MYC and PPM1D (WIP1). We also describe for the first time the germline mutation in BRCA2 c.8057T > C resulting in p.Leu2686Pro in our patient with confirmed FA. Biallelic BRCA2 mutations have predisposed to an aggressive and universally fatal subtype of childhood GBM in our patient. Copy number alterations and multiple oncogenic amplifications may be secondary to inherent chromosomal instability and this raises the question of what role BRCA2 may play in the development of GBM in children without FA.

Fanconi anemia with biallelic FANCD1/BRCA2 mutations - Case report of a family with three affected children

Fanconi anemia, complementation group D1 with bi-allelic FANCD1 (BRCA2) mutations, is a very rare genetic disorder characterized by early onset of childhood malignancies, including acute leukemia, brain cancer and nephroblastoma. Here, we present a case report of a family with 3 affected children in terms of treatment outcome, toxicity and characterization of the malignancies using comprehensive cytogenetic analysis. The first child was diagnosed with T-cell acute lymphoblastic leukemia when he was 11 months old. During chemotherapy, he suffered from repeated pancytopenia, sepsis and severe vincristine polyneuropathy, and 18 months after primary diagnosis, he succumbed to secondary acute monocytic leukemia. The second child was diagnosed with stage 2 triphasic nephroblastoma (Wilms tumor), when he was 3 years and 11 months old. During chemotherapy, he suffered from vincristine polyneuropathy. Currently, he is in complete remission, 29 months following the initial diagnosis. The third child was diagnosed with medulloblastoma with classical histology, when she was 4 years and 5 months old. After the first cycle of chemotherapy, she suffered from prolonged pancytopenia, sepsis and severe skin and mucosal toxicity. Six weeks after primary diagnosis, a first relapse in the posterior fossa was diagnosed, and at 7 and half months after primary diagnosis, a second relapse was diagnosed that led to the patient's death. Our case report underscores tumor heterogeneity, treatment toxicity and poor outcome in Fanconi anemia patients of complementation group D1.