Clinico-Radiological Outcomes in WNT-Subgroup Medulloblastoma.

Medulloblastoma (MB) comprises four broad molecular subgroups, namely wingless (WNT), sonic hedgehog (SHH), Group 3, and Group 4, respectively, with subgroup-specific developmental origins, unique genetic profiles, distinct clinico-demographic characteristics, and diverse clinical outcomes. This is a retrospective audit of clinical outcomes in molecularly confirmed WNT-MB patients treated with maximal safe resection followed by postoperative standard-of-care risk-stratified adjuvant radio(chemo)therapy at a tertiary-care comprehensive cancer centre. Of the 74 WNT-MB patients registered in a neuro-oncology unit between 2004 to 2020, 7 patients accrued on a prospective clinical trial of treatment deintensification were excluded, leaving 67 patients that constitute the present study cohort. The median age at presentation was 12 years, with a male preponderance (2:1). The survival analysis was restricted to 61 patients and excluded 6 patients (1 postoperative mortality plus 5 without adequate details of treatment or outcomes). At a median follow-up of 72 months, Kaplan-Meier estimates of 5-year progression-free survival and overall survival were 87.7% and 91.2%, respectively. Traditional high-risk features, large residual tumour (≥1.5 cm2), and leptomeningeal metastases (M+) did not significantly impact upon survival in this molecularly characterized WNT-MB cohort treated with risk-stratified contemporary multimodality therapy. The lack of a prognostic impact of conventional high-risk features suggests the need for refined risk stratification and potential deintensification of therapy.

WNT-pathway medulloblastoma: what constitutes low-risk and how low can one go?

Novel biological insights have established that medulloblastoma is a heterogenous disease comprising four broad molecular subgroups - WNT, SHH, Group 3, and Group 4 respectively, resulting in the incorporation of molecular/genetic information in 5th edition of WHO classification and contemporary risk-stratification. Concerns regarding therapy-related late toxicity in long-term survivors have led to systematic attempts at treatment de-intensification in good-risk medulloblastoma. Given the excellent survival (>90%) of WNT-pathway medulloblastoma, prospective clinical trials have focused on optimization of therapy to balance survival versus quality of survival. The currently accepted definition of low-risk WNT-pathway medulloblastoma includes children <16 years of age with residual tumour <1.5 cm2 and no evidence of metastases. This systematically excludes adolescents and young adults who have been perceived to have worse outcomes. We have previously reported long-term survival of our adolescent and young adult cohort that were largely comparable to childhood medulloblastoma. We now report on molecularly characterized WNT-subgroup patients treated between 2004-2020 with risk-stratified multi-modality therapy to identify differences between childhood (<15 years) versus adolescent and young adults (>15 years). Despite modest differences in disease status at presentation and treatment modality, there were no significant differences in patterns of failure or survival between childhood versus adolescent and young adult WNT-pathway medulloblastoma. Two de-intensification trials in low-risk WNT-pathway medulloblastoma - first testing omission of upfront craniospinal irradiation and second a primary chemotherapy approach after surgery - had to be terminated prematurely due to unacceptably high relapse rates suggesting that craniospinal irradiation remains an integral component of treatment. The presence of TP53 mutations and OTX2 gains have recently been reported as independent negative prognostic factors in a multi-institutional cohort of WNT-pathway medulloblastoma raising questions on eligibility of such patients for de-escalation trials. The definition of low-risk WNT-pathway medulloblastoma may need to be refined in light of recent clinical data and newer biological information.

Prognostic impact of semantic MRI features on survival outcomes in molecularly subtyped medulloblastoma.

PURPOSE: Imaging features are known to reflect inherent disease biology in various cancers including brain tumors. We report on the prognostic impact of magnetic resonance imaging (MRI) features on survival in patients with medulloblastoma treated between 2007 and 2018 at our institute. METHODS: Sixteen semantic imaging features (with predefined categories) were extracted from pre- and postcontrast T1-weighted and T2-weighted MRI by consensus. Univariate analysis and multivariate Cox regression analysis were performed to assess the correlation of semantic features with relapse-free survival (RFS) and overall survival (OS). RESULTS: The study cohort comprised 171 medulloblastoma patients (median age 9 years) treated with maximal safe resection followed by risk-stratified adjuvant radio(chemo)therapy. A total of 55 patients experienced recurrent/progressive disease (commonly neuraxial metastases) resulting in 44 deaths, including one treatment-related death. At a median follow-up of 45 months (interquartile range 19-65 months), 5­year Kaplan-Meier estimates of RFS and OS were 64% and 71%, respectively. Semantic MRI features such as non-central tumor location on vertical axis, absence of brainstem involvement, ≤ 80% solid tumor area with contrast uptake, heterogenous pattern of contrast enhancement, necrosis, calcification, and T2-weighted heterogeneity were associated with significantly worse RFS and/or OS in univariate analysis. Cox regression analysis identified tumor location on the vertical axis, brainstem involvement, and calcification as independent prognostic factors impacting outcomes. Distinctive MRI features correlated with survival even within individual molecular subgroups of medulloblastoma. CONCLUSION: Distinctive semantic MRI features correlate significantly with survival outcomes in medulloblastoma, also within individual molecular subgroups, reflecting their prognostic impact.

Real-Time PCR Assays on Formalin-Fixed, Paraffin-Embedded Medulloblastomas.

Real-time PCR technology has been instrumental in contributing toward biomarker discovery, classification of tumors as well as risk stratification of patients. However, much of its success depends on the quality and quantity of the starting material used for RNA extraction. Clinical samples are most often provided as formalin-fixed and paraffin-embedded, wherein the RNA is extensively degraded, affecting sensitivity. Here, we describe a real-time PCR based assay developed for molecular subgrouping of medulloblastomas that is particularly useful for formalin-fixed, paraffin-embedded (FFPE) samples.

Quantification of microRNAs in Cells and Tissues Using Stem-Loop RT PCR and qPCR.

MicroRNA s are small RNA molecules that regulate gene expression by binding to the 3' untranslated region of the mRNA of their target genes. MicroRNA expression is altered in medulloblastoma as compared to the normal brain and this alteration is often associated with the pathogenesis of this tumor. The quantification of microRNA expression is carried out using quantitative/real-time polymerase chain reaction (PCR). In this chapter, we describe the protocol for the quantification of microRNA s in medulloblastoma tissues and cultured cells. This is carried out in three steps: (1) Extraction of total RNA, (2) Stem-loop reverse-transcriptase PCR, and (3) quantitative PCR.

In Vivo Tumorigenicity Assays Using Subcutaneous and Orthotopic Xenografts in Immunodeficient Mice.

Evaluation of tumorigenic potential of medulloblastoma cell lines in vivo has been the obvious and major next step following cell line driven research for last many years. Effect of changes in expression of gene/s or efficacy of anticancer drugs on tumor initiation and/or growth can be easily assessed by injecting genetically modified cell lines in vivo or by treating in vivo xenografts of established cell lines with newer inhibitors or anticancer drugs. These studies are easy to perform and to reproduce in comparison to patient derived xenografts owing to ease in propagating, maintaining, and modifying genetic makeup of cell lines. Here we describe standardized protocols of obtaining either subcutaneous or orthotopic xenografts of medulloblastoma cell lines in immunodeficient mice. Once established, tumor growth of xenografts can be assessed during the course of experiment by either employing a simple method using Vernier caliper or technically demanding but sensitive method like in vivo bioluminescence imaging. In addition, xenograft tumors of euthanized animals can be preserved as formalin-fixed tissue specimens for further histopathological, immunohistochemical, or molecular analysis.

Clinical Audit of Survival Outcomes and Prognostic Factors in Adolescents and Adults with Medulloblastoma.

Purpose: Medulloblastomas, comprising 20%-25% of all primary brain tumors in children are much rarer in adulthood. Disease biology varies substantially across different age groups; however, owing to rarity, adults with medulloblastoma are traditionally treated using pediatric protocols. This is a retrospective audit of adolescent and adult medulloblastoma from a comprehensive cancer center. Methods: Data regarding demography, clinical presentation, imaging characteristics, histopathological features, molecular profiling, risk stratification, treatment details, and outcomes were retrieved from medical records. All time-to-event outcomes were analyzed using Kaplan-Meier method and compared with the log-rank test. Univariate and multivariate analysis of relevant prognostic factors was done with p value <0.05 being considered statistically significant. Results: A total of 162 patients ≥15 years of age with medulloblastoma were included. The median age was 25 years (range: 15-59 years) with leptomeningeal metastases seen in 31 (19%) patients at initial diagnosis. Following surgery, patients were treated with appropriate risk-stratified adjuvant therapy comprising of craniospinal irradiation plus boost with or without systemic chemotherapy. At a median follow-up of 50 months, 5-year Kaplan-Meier estimates of progression-free survival and overall survival were 53.5% and 59.5%, respectively. The addition of adjuvant systemic chemotherapy did not impact upon survival in standard-risk medulloblastoma. High-risk (HR) disease and anaplastic histology emerged as significant and independent predictors of poor survival on multivariate analysis. Conclusion: Medulloblastoma is a rare tumor in adolescents and adults with key differences in disease biology and resultant outcomes compared with the pediatric population. Contemporary management comprising maximal safe resection followed by appropriate risk-stratified adjuvant therapy provides acceptable survival outcomes.

MiR-592 activates the mTOR kinase, ERK1/ERK2 kinase signaling and imparts neuronal differentiation signature characteristic of Group 4 medulloblastoma.

Medulloblastoma, a common malignant brain tumor in children, consists of four molecular subgroups WNT, SHH, Group 3 and Group 4. Group 3, Group 4 tumors have an overlap in their expression profiles and genetic alterations but differ significantly in their clinical characteristics, with Group 3 having the worst 5-year overall survival of <60%. MiR-592 is overexpressed predominantly in Group 4 tumors. MiR-592 expression reduced the anchorage-independent growth, invasion potential and tumorigenicity of Group 3 medulloblastoma cells. DEPTOR, an endogenous inhibitor of the mTOR kinase, and EML1 were identified as novel targets of miR-592. The miR-592 mediated decrease in the DEPTOR expression levels activated both mTORC1 and mTORC2 complex in medulloblastoma cells. However, the miR-592 expression also decreased the AKT kinase activity, likely to be due to the activation of the inhibitory feedback of the mTOR signaling. MiR-592 expression upregulated several neuronal differentiation-related genes, a characteristic of Group 4 medulloblastoma in Group 3 cell lines. The expression of miR-592 also upregulated the activity of ERK1/ERK2 kinases indicating activation of the MAPK signaling pathway. The inhibition of MAPK signaling by the ERK1/ERK2 inhibitor and mTOR signaling by rapamycin abrogated the miR-592-mediated upregulation of neuronal differentiation-related genes. Group 4 medulloblastomas showed higher activity of the mTOR and MAPK signaling compared to Group 3 tumors. Thus, miR-592 overexpression appears to be a driver event and a determining factor of Group 4 biology, which activates the mTOR and MAPK signaling pathways and thereby imparts its characteristic expression profile of neuronal differentiation-related genes.

Downregulation of CRX, a Group 3-specific oncogenic transcription factor, inhibits TGF-ß/activin signaling in medulloblastoma cells.

Medulloblastoma, the most common malignant brain tumor in children, consists of four molecular subgroups WNT, SHH, Group 3, and Group 4. Group 3 has the worst survival rate among the four subgroups and is characterized by the expression of retina-specific genes. CRX, the master regulator of the photoreceptor differentiation, is aberrantly expressed in Group 3 medulloblastomas. CRX expression increased the proliferation, anchorage-independent growth, invasion potential, and tumorigenicity of medulloblastoma cells indicating the oncogenic role of CRX in medulloblastoma pathogenesis. CRX knockdown resulted in the downregulation of expression of several retina-specific genes like IMPG2, PDC, RCVRN. and Group 3 specific genes like GABRA5, MYC, PROM1. Thus, CRX plays a major role not only in the expression of retina-specific genes but also in defining Group 3 identity. Increased expression of several pro-apoptotic genes upon CRX knockdown suggests that CRX could protect Group 3 medulloblastoma cells from cell death. Several negative regulators of the TGF-ß signaling pathway like SMAD7, PMEPA1, KLF2 were upregulated upon the CRX knockdown. Western blot analysis showed a decrease in the levels of (Phospho)-SMAD2, total levels of SMAD2, SMAD4, and an increase in the levels of SMAD7 indicating inhibition of the TGF-ß signaling pathway upon CRX knockdown. Copy number variations in several genes involved in the TGF-ß signaling pathway occur in a subset of Group 3 tumors. Autocrine TGF-ß/activin signaling has recently been reported to be active in a subset of Group 3 medulloblastomas. CRX knockdown resulting in the inhibition of the TGF-ß/activin signaling pathway demonstrates an interaction between the two Group 3 specific oncogenic pathways and suggests simultaneous targeting of both CRX and TGF-ß signaling as a possible therapeutic strategy.

Downregulation of ARID1B, a tumor suppressor in the WNT subgroup medulloblastoma, activates multiple oncogenic signaling pathways.

Medulloblastoma, a common pediatric malignant brain tumor, consists of four distinct molecular subgroups WNT, SHH, Group 3 and Group 4. Exome sequencing of 11 WNT subgroup medulloblastomas from an Indian cohort identified mutations in several chromatin modifier genes, including genes of the mammalian SWI/SNF complex. The genome of WNT subgroup tumors is known to be stable except for monosomy 6. Two tumors, having monosomy 6, carried a loss of function mutation in the ARID1B gene located on chromosome 6. ARID1B expression is also lower in the WNT subgroup tumors compared to other subgroups and normal cerebellar tissues that could result in haploinsufficiency. The short hairpin RNA-mediated knockdown of ARID1B expression resulted in a significant increase in the malignant potential of medulloblastoma cells. Transcriptome sequencing identified upregulation of several genes encoding cell adhesion proteins, matrix metalloproteases indicating the epithelial-mesenchymal transition. The ARID1B knockdown also upregulated ERK1/ERK2 and PI3K/AKT signaling with a decrease in the expression of several negative regulators of these pathways. The expression of negative regulators of the WNT signaling like TLE1, MDFI, GPX3, ALX4, DLC1, MEST decreased upon ARID1B knockdown resulting in the activation of the canonical WNT signaling pathway. Synthetic lethality has been reported between SWI/SNF complex mutations and EZH2 inhibition, suggesting EZH2 inhibition as a possible therapeutic modality for WNT subgroup medulloblastomas. Thus, the identification of ARID1B as a tumor suppressor and its downregulation resulting in the activation of multiple signaling pathways opens up opportunities for novel therapeutic modalities for the treatment of WNT subgroup medulloblastoma.

The proteomic analysis shows enrichment of RNA surveillance pathways in adult SHH and extensive metabolic reprogramming in Group 3 medulloblastomas.

Medulloblastoma, a common malignant brain tumor in children, comprises four molecular subgroups WNT, SHH, Group 3, and Group 4. In the present study, we performed a deep proteome-based investigation of SHH, Group 3 and Group 4 tumors. The adult SHH medulloblastomas were found to have a distinct proteomic profile. Several RNA metabolism-related pathways including mRNA splicing, 5' to 3' RNA decay, 3' to 5' RNA decay by the RNA exosome, and the N6-methyladenosine modification of RNA were enriched in adult SHH tumors. The heightened expression of the RNA surveillance pathways is likely to be essential for the viability of adult SHH subgroup medulloblastomas, which carry mutations in U1snRNA encoding gene and thus could be a vulnerability of these tumors. Group 3 and Group 4 medulloblastomas, on the other hand, are known to have an overlap in their expression profiles and underlying genetic alterations. Group 3 proteome was found to be distinctively enriched in several metabolic pathways including glycolysis, gluconeogenesis, glutamine anabolism, glutathione-mediated anti-oxidant pathway, and drug metabolism pathway suggests that the extensive metabolic rewiring is likely to be responsible for the aggressive clinical behavior of Group 3 tumors. This comprehensive proteomic analysis has provided valuable insight into the biology of Group 3 and adult SHH medulloblastomas, which could be further explored for effective treatment of these tumors.

Autophagy inhibition impairs the invasion potential of medulloblastoma cells.

Medulloblastoma, a highly malignant pediatric brain tumor, consists of four distinct molecular subgroups called WNT, SHH, Group 3, and Group 4 that differ in their clinical characteristics with the WNT subgroup having excellent survival rate. About 1/3rd medulloblastomas have metastasis at the time of diagnosis suggesting, high invasion potential of these tumors. We have earlier reported that the tumor-suppressive role of miR-204 and miR-30a is accompanied by inhibition of autophagy in medulloblastoma cells. In the present study, we have investigated the role of autophagy in medulloblastoma biology. Autophagy was inhibited in the medulloblastoma cell lines belonging to the SHH, Group 3, and Group 4 using the shRNA mediated knockdown of ATG5, an upstream regulator of autophagy. The effect of autophagy inhibition was studied on the growth and malignant behavior of medulloblastoma cells. ATG5 knockdown resulted in the autophagy inhibition in medulloblastoma cells as judged by the reduction in the flux of LC3B, a marker for autophagy. Autophagy inhibition did not result in a significant difference in the proliferation and anchorage-independent growth of the medulloblastoma cells. On the other hand, autophagy inhibition brought about a substantial reduction in the invasion potential of all three medulloblastoma cell lines studied. The present study suggests a therapeutic potential for autophagy inhibitors in the treatment of medulloblastoma. Autophagy inhibitors could be effective in reducing the dose of craniospinal radiation, thereby leading to a significant reduction in the treatment-related side effects.

Restoration of miR-193a expression is tumor-suppressive in MYC amplified Group 3 medulloblastoma.

Medulloblastoma, a highly malignant pediatric brain tumor, consists of four molecular subgroups, namely WNT, SHH, Group 3, and Group 4. The expression of miR-193a, a WNT subgroup-specific microRNA, was found to be induced by MYC, an oncogenic target of the canonical WNT signaling. MiR-193a is not expressed in Group 3 medulloblastomas, despite MYC expression, as a result of promoter hypermethylation. Restoration of miR-193a expression in the MYC amplified Group 3 medulloblastoma cells resulted in inhibition of growth, tumorigenicity, and an increase in radiation sensitivity. MAX, STMN1, and DCAF7 were identified as novel targets of miR-193a. MiR-193a mediated downregulation of MAX could suppress MYC activity since it is an obligate hetero-dimerization partner of MYC. MYC induced expression of miR-193a, therefore, seems to act as a feedback inhibitor of MYC signaling. The expression of miR-193a resulted in widespread repression of gene expression that included not only several cell cycle regulators, WNT, NOTCH signaling genes, and those encoding DNA replication machinery, but also several chromatin modifiers like SWI/SNF family genes and histone-encoding genes. MiR-193a expression brought about a reduction in the global levels of H3K4me3, H3K27ac, the histone marks of active chromatin, and an increase in the levels of H3K27me3, a repressive chromatin mark. In cancer cells having high MYC expression, MYC brings about transcriptional amplification of all active genes apart from the induction of its target genes. MiR-193a, on the other hand, brought about global repression of gene expression. Therefore, miR-193a has therapeutic potential in the treatment of not only Group 3 medulloblastomas but possibly other MYC overexpressing aggressive cancers as well.

Outcomes of salvage re-irradiation in recurrent medulloblastoma correlate with age at initial diagnosis, primary risk-stratification, and molecular subgrouping.

PURPOSE: To report outcomes of salvage re-irradiation (re-RT) in recurrent/progressive medulloblastoma (MB). METHODS: Medical records of patients treated with curative-intent re-RT as multi-modality management for recurrent/progressive MB between 2008 and 2018 were analyzed retrospectively. RESULTS: A total of 28 patients (median age 18 years at index diagnosis) were included. Molecular subgrouping was done using real-time reverse transcriptase polymerase chain reaction (RT-PCR) based on the differential expression of select set of 12 protein coding genes and 9 microRNAs. Fifteen of 17 (88%) patients with sonic hedgehog (SHH)-MB developed isolated local recurrence within the index tumor-bed, while 5 of 7 (72%) patients with Group 4 MB developed localized relapse outside the posterior fossa. Diffuse neuraxial dissemination was seen in 2 patients with SHH-MB, and one each of Group 4 and wingless (WNT)-MB. Molecular subgrouping was not known in 3 patients. The dose and volume of re-RT was based on site and patterns of relapse, comprising unifocal in 18 (64%), multi-focal in 3 (11%), and repeat craniospinal irradiation (re-CSI) in 7 (25%) patients. Median interval from primary irradiation to re-RT was 49.5 months (range 24-98 months) with median cumulative biologically effective dose of 117 Gy (range 78-132 Gy). All patients received platinum-based salvage chemotherapy either before or after re-RT. One patient developed symptomatic radiation necrosis following re-CSI. At a median follow-up of 24 months (range 6-84 months), 2-year post-re-RT progression-free survival (PFS) and overall survival (OS) was 46% and 51% respectively. Younger age (< 18 years) at index diagnosis, primary risk stratification (standard-risk) and molecular subgrouping (Group 4) were associated with significantly better post-re-RT outcomes. CONCLUSION: Salvage re-RT provides good local control and encouraging survival outcomes with acceptable toxicity in selected patients with recurrent/progressive MB.

Pediatric Patients With SHH Medulloblastoma Fail Differently as Compared With Adults: Possible Implications for Treatment Modifications.

PURPOSE: The purpose of this work was to study the diversity of sonic hedgehog (SHH) medulloblastoma across different age groups with an emphasis on patterns of relapse. METHODS: All data for the study were obtained through review of medical records, imaging, radiation charts, treatment planning, and chemotherapy details. RESULTS: Sixty-three patients with SHH medulloblastoma were identified from a prospectively maintained database and classified into 3 groups-infantile: ≤3 years (i-SHH, n=11); pediatric: >3 to <18 years (p-SHH, n=21); and adult: ≥18 years (a-SHH; n=31). Lateralized tumors were common with increasing age (81% a-SHH, 67% p-SHH, 27% i-SHH; P=0.01). Large cell anaplastic histology was relatively common for p-SHH (33%), while the nodular/desmoplastic variant was more frequent in i-SHH (64%) and adults (51%). Median follow-up was 38 months (range, 5 to 91 mo). Five-year event-free survival was 80%, 31%, and 52% for i-SHH, p-SHH, and a-SHH, respectively (P=0.001). Median time to failure for p-SHH and a-SHH were 12 and 36 months, respectively. For p-SHH, 83% were metastatic relapses compared with localized failure in 75% for a-SHH. Five-year overall survival for i-SHH, p-SHH, and a-SHH were 91%, 31%, and 70%, respectively (P=0.001). On univariate analysis, event-free survival was significantly worse for superiorly located tumors (P=0.01), nondesmoplastic histology (P=0.02), and histology alone for overall survival (P=0.04) (none on multivariate analysis). CONCLUSIONS: SHH medulloblastoma demonstrates varied outcomes depending on age, with p-SHH associated with early and metastatic relapses, while for a-SHH it tends to be delayed and localized.

Downregulation of miR-204 expression defines a highly aggressive subset of Group 3/Group 4 medulloblastomas.

Genome-wide expression profiling studies have identified four core molecular subgroups of medulloblastoma: WNT, SHH, Group 3 and Group 4. Molecular markers are necessary for accurate risk stratification in the non-WNT subgroups due to the underlying heterogeneity in genetic alterations and overall survival. MiR-204 expression was evaluated in molecularly classified 260 medulloblastomas from an Indian cohort and in 763 medulloblastomas from the MAGIC cohort, SickKids, Canada. Low expression of miR-204 in the Group 3 / Group 4 tumors identify a highly aggressive subset of tumors having poor overall survival, in the two independent cohorts of medulloblastomas. Downregulation of miR-204 expression correlates with poor survival within the Group 4 as well indicating it as a valuable risk-stratification marker in the subgroup. Restoration of miR-204 expression in multiple medulloblastoma cell lines was found to inhibit their anchorage-independent growth, invasion potential and tumorigenicity. IGF2R was identified as a novel target of miR-204. MiR-204 expression resulted in downregulation of both M6PR and IGF2R that transport lysosomal proteases from the Golgi apparatus to the lysosomes. Consistent with this finding, miR-204 expression resulted in reduction in the levels of the lysosomal proteases in medulloblastoma cells. MiR-204 expression also resulted in inhibition of autophagy that is known to be dependent on the lysosomal degradation pathway and LC3B, a known miR-204 target. Treatment with HDAC inhibitors resulted in upregulation of miR-204 expression in medulloblastoma cells, suggesting therapeutic role for these inhibitors in the treatment of medulloblastomas. In summary, miR-204 is not only a valuable risk stratification marker in the combined cohort of Group 3 / Group 4 medulloblastomas as well as in the Group 4 itself, that has paucity of good prognostication markers, but also has therapeutic potential as indicated by its tumor suppressive effect on medulloblastoma cells.

Nomograms based on preoperative multiparametric magnetic resonance imaging for prediction of molecular subgrouping in medulloblastoma: results from a radiogenomics study of 111 patients.

Background: Novel biological insights have led to consensus classification of medulloblastoma into 4 distinct molecular subgroups-wingless (WNT), sonic hedgehog (SHH), Group 3, and Group 4. We aimed to predict molecular subgrouping in medulloblastoma based on preoperative multiparametric magnetic resonance imaging (MRI) characteristics. Methods: A set of 19 MRI features were evaluated in 111 patients with histologic diagnosis of medulloblastoma for prediction of molecular subgrouping. MRI characteristics were correlated with molecular subgroups derived from tissue samples in 111 patients (WNT = 17, SHH = 44, Group 3 = 27, and Group 4 = 23). Multinomial logistic regression of imaging parameters was performed on a training cohort (TC) of 76 patients, representing two-thirds of randomly selected patients from each of 4 molecular subgroups, to generate binary nomograms. Validation of these nomograms was performed on the remaining 35 patients as the validation cohort (VC). Results: Medulloblastoma subgroups could be accurately predicted by preoperative MRI features in 74% of cases. Predictive accuracy was excellent for SHH (95%), acceptably high for Group 4 (78%), modest for Group 3 (56%) and worst for WNT (41%) subgroup medulloblastoma. SHH-specific nomogram was associated with excellent correlation between TC and VC, with area under the curve (AUC) of 0.939 and 0.991, respectively. AUC for Group 4 was acceptable at 0.851 and 0.788 in TC and VC, respectively; however, these values were consistently suboptimal in WNT and Group 3 medulloblastoma. Conclusion: The predictive accuracy of MRI-based nomograms was excellent for SHH and encouraging for Group 4 medulloblastoma. Further work is needed for Group 3 and WNT-pathway medulloblastoma.

Restoration of miR-30a expression inhibits growth, tumorigenicity of medulloblastoma cells accompanied by autophagy inhibition.

Medulloblastoma is a highly malignant pediatric brain tumor. About 30% patients have metastasis at diagnosis and respond poorly to treatment. Those that survive, suffer long term neurocognitive, endocrine and developmental defects due to the cytotoxic treatment to developing child brain. It is therefore necessary to develop targeted treatment strategies based on underlying biology for effective treatment of medulloblastoma with minimal side effects. Medulloblastomas are believed to be the result of deregulated nervous system development as evident from the role of WNT and SHH developmental signaling pathways in pathogenesis of medulloblastomas. MicroRNAs are known to play vital roles in nervous system development as well as in cancer. MicroRNA profiling of medulloblastomas identified miR-30 family members' expression to be downregulated in medulloblastomas belonging to the four known molecular subgroups viz. WNT, SHH, Group 3 and Group 4 as compared to that in normal brain tissues. Furthermore, established medulloblastoma cell lines Daoy, D283 and D425 were also found to underexpress miR-30a. Restoration of miR-30a expression using inducible lentiviral vector inhibited proliferation, clonogenic potential and tumorigenicity of medulloblastoma cells. MiR-30a is known to target Beclin1, a mediator of autophagy. MiR-30a expression was found to downregulate Beclin1 expression and inhibit autophagy in the medulloblastoma cell lines as judged by downregulation of LC3B expression and its turnover upon chloroquine treatment and starvation induced autophagy induction. MiR-30a therefore could serve as a novel therapeutic agent for the effective treatment of medulloblastoma by inhibiting autophagy that is known to play important role in cancer cell growth, survival and malignant behavior.