Medulloblastoma

Thrombospondin-1 mimetics are promising novel therapeutics for MYC-associated medulloblastoma

BACKGROUND

Medulloblastoma (MB) comprises four subtypes of which group 3 MB are the most aggressive. Although overall survival for MB has improved, the outcome of group 3 MB remains dismal. C-MYC (MYC) amplification or MYC overexpression which characterizes group 3 MB is a strong negative prognostic factor and is frequently associated with metastases and relapses. We previously reported that MYC expression alone promotes highly aggressive MB phenotypes, in part via repression of thrombospondin-1 (TSP-1), a potent tumor suppressor.

METHODS

In this study, we examined the potential role of TSP-1 and TSP-1 peptidomimetic ABT-898 in MYC-amplified human MB cell lines and two distinct murine models of MYC-driven group 3 MBs.

RESULTS

We found that TSP-1 reconstitution diminished metastases and prolonged survival in orthotopic xenografts and promoted chemo- and radio-sensitivity via AKT signaling. Furthermore, we demonstrate that ABT-898 can recapitulate the effects of TSP-1 expression in MB cells in vitro and specifically induced apoptosis in murine group 3 MB tumor cells.

CONCLUSION

Our data underscore the importance of TSP-1 as a critical tumor suppressor in MB and highlight TSP-1 peptidomimetics as promising novel therapeutics for the most lethal subtype of MB.

JPO2/CDCA7L and LEDGF/p75 Are Novel Mediators of PI3K/AKT Signaling and Aggressive Phenotypes in Medulloblastoma

Substantial evidence links Myc-PI3K/AKT signaling to the most aggressive subtype of medulloblastoma and this axis in medulloblastoma therapy. In this study, we advance understanding of how Myc-PI3K/AKT signaling contributes to this malignancy, specifically, in identifying the Myc-interacting protein JPO2 and its partner binding protein LEDGF/p75 as critical modulators of PI3K/AKT signaling and metastasis in medulloblastoma. JPO2 overexpression induced metastatic medulloblastoma in vivo through two synergistic feed-forward regulatory circuits involving LEDGF/p75 and AKT that promote metastatic phenotypes in this setting. Overall, our findings highlight two novel prometastatic loci in medulloblastoma and point to the JPO2:LEDGF/p75 protein complex as a potentially new targetable component of PI3K/AKT signaling in medulloblastoma. Cancer Res; 76(9); 2802-12. ©2016 AACR.

NPV-LDE-225 (Erismodegib) inhibits epithelial mesenchymal transition and self-renewal of glioblastoma initiating cells by regulating miR-21, miR-128, and miR-200

BACKGROUND

Glioblastoma multiforme is the most common form of primary brain tumor, often characterized by poor survival. Glioblastoma initiating cells (GICs) regulate self-renewal, differentiation, and tumor initiation properties and are involved in tumor growth, recurrence, and resistance to conventional treatments. The sonic hedgehog (SHH) signaling pathway is essential for normal development and embryonic morphogenesis. The objectives of this study were to examine the molecular mechanisms by which GIC characteristics are regulated by NPV-LDE-225 (Smoothened inhibitor; (2,2'-[[dihydro-2-(4-pyridinyl)-1,3(2H,4H)-pyrimidinediyl]bis(methylene)]bis[N,N-dimethylbenzenamine).

METHODS

Cell viability and apoptosis were measured by XTT and annexin V-propidium iodide assay, respectively. Gli translocation and transcriptional activities were measured by immunofluorescence and luciferase assay, respectively. Gene and protein expressions were measured by quantitative real-time PCR and Western blot analyses, respectively.

RESULTS AND CONCLUSION

NPV-LDE-225 inhibited cell viability, neurosphere formation, and Gli transcriptional activity and induced apoptosis by activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase. NPV-LDE-225 increased the expression of tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-R1/DR4, TRAIL-R2/DR5, and Fas and decreased the expression of platelet derived growth factor receptor-α and Bcl2, and these effects were abrogated by Gli1 plus Gli2 short hairpin RNAs. NPV-LDE-225 enhanced the therapeutic potential of FasL and TRAIL by upregulating Fas and DR4/5, respectively. Interestingly, NPV-LDE-225 induced expression of programmed cell death 4 and apoptosis and inhibited cell viability by suppressing micro RNA (miR)-21. Furthermore, NPV-LDE-225 inhibited pluripotency-maintaining factors Nanog, Oct4, Sox2, and cMyc. The inhibition of Bmi1 by NPV-LDE-225 was regulated by induction of miR-128. Finally, NPV-LDE-225 suppressed epithelial-mesenchymal transition by upregulating E-cadherin and inhibiting N-cadherin, Snail, Slug, and Zeb1 through modulating the miR-200 family. Our data highlight the importance of the SHH pathway for self-renewal and early metastasis of GICs.

Neurological disorders and therapeutics targeted to surmount the blood-brain barrier

We are now in an aging population, so neurological disorders, particularly the neurodegenerative diseases, are becoming more prevalent in society. As per the epidemiological studies, Europe alone suffers 35% of the burden, indicating an alarming rate of disease progression. Further, treatment for these disorders is a challenging area due to the presence of the tightly regulated blood-brain barrier and its unique ability to protect the brain from xenobiotics. Conventional therapeutics, although effective, remain critically below levels of optimum therapeutic efficacy. Hence, methods to overcome the blood-brain barrier are currently a focus of research. Nanotechnological applications are gaining paramount importance in addressing this question, and yielding some promising results. This review addresses the pathophysiology of the more common neurological disorders and novel drug candidates, along with targeted nanoparticle applications for brain delivery.

Genetics of medulloblastoma: clues for novel therapies

Medulloblastoma is the most common malignant brain tumor in children. Current medulloblastoma therapy entails surgery, radiation and chemotherapy. The 5-year survival rate for patients ranges from 40 to 70%, with most survivors suffering from serious long-term treatment-related sequelae. Additional research on the molecular biology and genetics of medulloblastoma is needed to identify robust prognostic markers for disease-risk stratification, to improve current treatment regimes and to discover novel and more effective molecular-targeted therapies. Recent advances in molecular biology have led to the development of powerful tools for the study of medulloblastoma tumorigenesis, which have revealed new insights into the molecular underpinnings of this disease. Here we discuss the signaling pathway alterations implicated in medulloblastoma pathogenesis, the techniques used in molecular profiling of these tumors and recent molecular subclassification schemes. Particular emphasis is given to the identification of novel molecular targets for less toxic, patient-tailored therapeutic approaches.

Rhesus macaque as an animal model for posterior fossa syndrome following tumor resection

BACKGROUND/AIMS

Posterior fossa tumors are the most common brain tumors in children. Surgeons usually remove these tumors via a midline incision through the posterior vermis of the cerebellum. Though often effective, this surgery causes hypotonia, ataxia, oculomotor deficits, transient mutism, difficulty in swallowing and nausea. To date, there is no animal model that mimics these complications. We found that the rhesus macaque is a good model for the consequences of this surgery.

METHODS

We made a midline incision through the cerebellar vermis of one monkey to mimic the posterior fossa surgery. Then, we closely monitored the monkey for deficits following the surgery.

RESULTS

In the first few days, the monkey exhibited nausea, hypotonia, ataxia, difficulty in swallowing and an absence of vocalization. At 28 days, we recorded eye movements and found severe deficits in the accuracy of rapid eye movements and smooth pursuit of a target. Additionally, the animal had trouble fixating and a rightward-beating nystagmus. Oculomotor signs persisted until we sacrificed the animal 99 days after surgery, but the other effects resolved by 37 days.

CONCLUSION

Our surgery in a monkey caused the same postsurgical signs observed in humans. We expect to use this model to improve the posterior fossa surgery methods.

Immunohistochemical expression of Sonic hedgehog in intraductal papillary mucinous tumor of the pancreas

Aberrant expression of Sonic hedgehog (Shh) has been reported in many human cancers including ductal carcinoma of the pancreas. The intraductal papillary mucinous tumor (IPMT) has been considered as one of the precursor lesions of invasive ductal carcinoma of the pancreas. Shh expression in pancreatic IPMT has not been reported. We investigated an immunohistochemical (IHC) expression of Shh in 55 cases of pancreatic IPMT. We analyzed the IHC expression of Shh in the following histologic grades of tumor: adenoma (AD), moderate dysplasia (MD), noninvasive carcinoma (NIC), and invasive carcinoma (IC), and with the following histologic subtype classification: intestinal, pancreatobiliary, null, and unclassifiable type. IHC Shh expression was noted in 6 (46.2%) of 13 AD, 5 (35.7%) of 14 MD, 12 (80%) of 15 NIC, and 11 (84.6%) of 13 IC. Shh expression was significantly increased in malignant IPMT (NIC+IC) compared with nonmalignant IPMT (AD+MD) (82.1% vs. 40.7%, P=0.0005). IHC Shh expression was found in 11 (68.8%) of 16 intestinal types, 13 (92.8%) of 14 pancreatobiliary types, 8 (38.1%) of 21 null types, and 2 (50%) of 4 unclassifiable types. Intestinal and pancreatobiliary subtypes showed a high expression of Shh compared with the null and unclassifiable type of IPMT. All 3 cases of node metastasis showed IHC Shh expression in tumor cells of metastatic lymph nodes. Therefore, Shh expression may have a critical role in the late stage of carcinogenesis of IPMT, and may impact metastatic progression to the lymph nodes in malignant IPMT.

Interferon-gamma mediated up-regulation of caspase-8 sensitizes medulloblastoma cells to radio- and chemotherapy

Loss of caspase-8 expression - which has been demonstrated in a subset of Medulloblastoma (MB) - might block important apoptotic signalling pathways and therefore contribute to treatment resistance. In this study, IFN-gamma mediated up-regulation of caspase-8 in human MB cells was found to result in chemosensitization to cisplatin, doxorubicin and etoposide, and sensitisation to radiation. These effects were more prominent in D425 and D341 MB cells (low basal caspase-8 expression) when compared to DAOY MB cells (high basal caspase-8 expression). IFN-gamma mediated chemosensitization and radiosensitization effects were reduced by treatment with the caspase-8 specific inhibitor z-IETD-fmk. Treatment of IFN-gamma resulted in activation of STAT1 in DAOY MB cells and to a lesser extent in D425, but not in D341, indicating that IFN-gamma acts in MB cells through STAT1-dependent and -independent signalling pathways. Taken together, our results demonstrate that IFN-gamma mediated restoration of caspase-8 in MB cells might enhance apoptotic pathways relevant to the response to chemo- and radiotherapy.

Capillary physiology of human medulloblastoma: impact on chemotherapy

BACKGROUND

Advances in the treatment of medulloblastoma have largely been attributed to the introduction of chemotherapy, although Phase III trials have shown advantages for chemotherapy only in subgroups. Because the efficacy of chemotherapy depends on tumor vascularization, the vascular physiology of human medulloblastomas was evaluated.

METHODS

Seven patients with histologically proven medulloblastomas underwent measurements of capillary permeability and vascular plasma volume using contrast-enhanced dynamic computer tomography. Regional blood flow was measured in 5 patients using xenon computed tomography (CT).

RESULTS

The capillary permeability-surface product for water-soluble compounds ranged from 1.7 +/- 5.5 to 17.6 +/- 12.3 muL/g/min with a mean of 10.5 +/- 6.3 microL/g/min. The vascular plasma volume ranged from 0.02 +/- 0.021 to 0.045 +/- 0.049 mL/g with a mean of 0.03 +/- 0.01 mL/g. The efflux rate ranged from 0.012 +/- 0.007 to 0.065 +/- 0.064 1/min with a mean of 0.039 +/- 0.020 1/min. Regional tumoral blood flow showed a mean of 19.86 +/- 6.8 mL/100g/min as compared with normal cerebellum with 45.4 +/- 12.03 mL/100g/min (P < .005).

CONCLUSIONS

The current study demonstrated a low capillary permeability and blood flow in medulloblastomas that could explain the limited response rates of partially resected tumors even after aggressive high-dose chemotherapy, as recently reported.

The hedgehog signalling pathway in the gastrointestinal tract: implications for development, homeostasis, and disease

The hedgehog signalling pathway is critical to normal mammalian gastrointestinal development. Through epithelial-mesenchymal interactions, hedgehog signalling ensures appropriate axial patterning of the embryonic gut. Congenital abnormalities, including malrotations, anorectal malformations, and tracheoesophageal fistula are associated with germ-line mutations/deletion of genes encoding hedgehog signalling components in man and present in genetically engineered animal models. In adults, there is evidence that the pathway plays a role in maintaining stem cell populations in the stomach and directing epithelial cell differentiation in the intestine. Recent data implicate hedgehog signalling in the formation and maintenance of a number of malignancies, including those of the upper gastrointestinal (GI) tract and pancreas, in which abrogation of the pathway offers a novel therapeutic approach in animal models. Most recently, evidence in vitro indicates that there is a recapitulation of embryonic hedgehog signalling in acute epithelial injury and chronic inflammation, a finding with key implications for inflammatory disorders of the intestine, such as inflammatory bowel diseases. This pathway may provide an important link between chronic inflammation and cancer. We summarize the available evidence demonstrating that this developmental pathway has continuing roles in adult homeostasis and is dysregulated in malignancy and inflammation of the gastrointestinal tract.

Robust infectivity and replication of Delta-24 adenovirus induce cell death in human medulloblastoma

The diverse advanced treatment modalities currently available to children with medulloblastoma, including surgery and radiotherapy, are associated with deleterious side effects and often with an unfavorable prognosis. A mutant adenovirus, Delta-24, which has a 24-base pair deletion in the Rb-binding region of the E1A gene, demonstrates selective replication and oncolysis in various malignant phenotypes. Here we report the ability of Delta-24 to kill medulloblastoma cells. Flow cytometric analyses of cell receptors demonstrated expression of the coxsackie adenovirus receptor and RGD-related integrins in the assessed medulloblastoma cell lines. Infectivity assays using a replication-deficient adenovirus to transduce the green fluorescence protein gene showed that the Delta-24 adenovirus infects 99% of Daoy and 46% of D283 Med medulloblastoma cells at a multiplicity of infection (MOI) of 50. Within 4 days after infecting medulloblastoma cells with Delta-24, a noticeable cytopathic effect was produced. Delta-24 induced a total cytopathic effect in Daoy and D283 Med medulloblastoma cells after 6 and 8 days of infection, respectively. In the infected population of cells, cell death correlated with the accumulation of cells in the S phase. At 5 days post-infection with 2.5 MOIs of Delta-24 adenovirus, the percentage of Daoy medulloblastoma cells in the S phase increased to 71.9+/-5.5%, compared with control values of 20.5+/-1.4%. The release of viral progeny was quantified as being increased by two orders of magnitude, indicating efficient replication of Delta-24 in medulloblastoma cells. This is the first report of the ability of oncolytic adenoviruses to infect and kill medulloblastoma cells, the findings of which suggest the potential efficacy of Delta-24 as a therapy for human medulloblastoma tumors.

Survivin, Survivin-2B, and Survivin-deItaEx3 expression in medulloblastoma: biologic markers of tumour morphology and clinical outcome

Survivin is an apoptotic inhibitor that is expressed at high levels in a variety of malignancies. Survivin has four known alternative splice forms (Survivin, Survivin-2B, Survivin-deltaEx3, and Survivin-3B), and the recent literature suggests that these splice variants have unique functions and subcellular localisation patterns. We evaluated 19 fresh-frozen paediatric medulloblastomas for the expression of three Survivin isoforms by quantitative PCR. Survivin was most highly expressed when compared with normal cerebellar tissue. We also investigated Survivin protein expression in 40 paraffin-embedded paediatric medulloblastoma tumours by immunohistochemistry. We found a statistically significant association between the percentage of Survivin-positive cells and histologic subtype, with the large-cell-anaplastic variant expressing Survivin at higher levels than the classic subtype. We also found a statistically significant relationship between the percent of Survivin-positive cells in the tumours and clinical outcome, with higher levels of Survivin correlating with a worse prognosis. In summary, our study demonstrates a role for Survivin as a marker of tumour morphology and clinical outcome in medulloblastoma. Survivin may be a promising future prognostic tool and potential biologic target in this malignancy.

Basal cell nevus syndrome

PURPOSE OF REVIEW

Basal cell nevus syndrome (BCNS), is a hereditary condition transmitted as an autosomal dominant trait exhibiting high penetrance and variable expressivity. Inherited or spontaneous mutations in the human homologue of the Drosophila patched gene underlie the disorder and in addition to tumor predisposition, are associated with a range of 'patterning' defects. Recent advances, with glimpses of possible therapies are emerging, but because of the wide-ranging nature of phenotypic expression and overlap with other syndromes, there is difficulty. Finally, because of the importance of PTCH and paralogous genes in many species other than humans, reports appear in a correspondingly wide range of journals, which makes 'keeping abreast' difficult.

RECENT FINDINGS

Progress has been achieved in understanding the role of Gli-1, 2, & 3 in development of 'sporadic' BCCs and BCNS. Expression of PTCH1 is now known to be regulated by alternative promoters and a single functional Gli-binding site. Expression of FOXE1 as a new transcriptional target of Gli2 has been demonstrated in human epidermis and BCCs. Finally, the discovery of Shh pathway inhibitors such as cyclopamine, a naturally occurring alkaloid and ornithine decarboxylase inhibition suggest possible interventional therapies.

SUMMARY

In BCNS, phenotype does not correlate with position of mutations within Patched, suggesting genetic makeup and environment modulate effects of premature protein truncation induced by PTCH mutation. These developmental abnormalities occur as a result of haplo-insufficiency in heterozygotes for the mutated gene, whereas neoplastic complications arise from a classical two-hit tumor suppressor gene model. Attention is therefore turning toward TP53 and PTCH associations.

Medulloblastoma cell invasion is inhibited by green tea (-)epigallocatechin-3-gallate

Epigallocatechin-3-gallate (EGCG), the major green tea polyphenol, can reach the brain following oral intake and could thus act as an anti-tumoral agent targeting several key steps of brain cancer cells invasive activity. Because integrin-mediated extracellular matrix recognition is crucial during the cell adhesion processes involved in carcinogenesis, we have investigated the effects of EGCG on different cellular integrins of the pediatric brain tumor-derived medulloblastoma cell line DAOY. Using flow cytometry, we report the levels of expression of several cell surface integrins in DAOY. These include high expression of alpha2, alpha3, and beta1 integrins, as well as alphav and beta3 integrins. Moreover, we provide evidence that EGCG can antagonize DAOY cell migration specifically on collagen by increasing cell adhesive ability through specific gene and protein upregulation of the beta1 integrin subunit. Our results suggest that this naturally occurring green tea polyphenol may thus be used as a nutraceutical therapeutic agent in targeting the invasive character of medulloblastomas.

Neurosurgical treatment of brain tumors in children

Primary brain tumors are the most common solid neoplasms of childhood. The diagnosis of brain tumors in the general pediatric population remains challenging. Nevertheless, it is clear that refinements in imaging, surgical technique, and adjunctive therapies have led to longer survival and an improving quality of life in children with brain tumors.