Molecular genetics of pediatric central nervous system tumors

Immunotherapy for Medulloblastoma: Current Perspectives

Background

Immune-mediated therapies have transformed the treatment of metastatic melanoma and renal, bladder, and both small and non-small cell lung carcinomas. However, immunotherapy is yet to demonstrate dramatic results in brain tumors like medulloblastoma for a variety of reasons. Recent pre-clinical and early phase human trials provide encouraging results that may overcome the challenges of central nervous system (CNS) tumors, which include the intrinsic immunosuppressive properties of these cancers, a lack of antigen targets, antigenic variability, and the immune-restrictive site of the CNS. These studies highlight the growing potential of immunotherapy to treat patients with medulloblastoma, a disease that is a frequent cause of morbidity and mortality to children and young adults.

Methods

We conducted an inclusive review of the PubMed-indexed literature and studies listed in clinicaltrials.gov using combinations of the keywords medulloblastoma, immunotherapy, CNS tumors, brain tumors, vaccines, oncolytic virus, natural killer, and CAR T to identify trials evaluating immunotherapy in preclinical experiments or in patients with medulloblastoma. Given a limited number of investigations using immunotherapy to treat patients with medulloblastoma, 24 studies were selected for final analysis and manuscript citation.

Results

This review presents results from pre-clinical studies in medulloblastoma cell lines, animal models, and the limited trials involving human patients.

Conclusion

From our review, we suggest that cancer vaccines, oncolytic viral therapy, natural killer cells, and CAR T therapy hold promise against the innate immunosuppressive properties of medulloblastoma in order to prolong survival. There is an unmet need for immunotherapy regimens that target overexpressed antigens in medulloblastoma tumors. We advocate for more combination treatment clinical trials using conventional surgical and radiochemotherapy approaches in the near-term clinical development.

MiR-9-3p augments apoptosis induced by H2O2 through down regulation of Herpud1 in glioma

MicroRNAs are short, single-stranded non-coding RNA molecules that function as regulators of tumor progression in various cancers, including glioma. The present study sought to investigate the biological functions of miR-9-3p in glioma progression. The results of a microRNA microarray indicated that microRNA-9-3p (miR-9-3p, miR-9*) is down-regulated in high-grade (grades III and IV) gliomas compared with non-tumor tissues. These results were confirmed with real-time PCR. The miR-9-3p expression level was associated with age and tumor grade. Herpud1 was regulated by miR-9-3p in glioma cells and tissues and was identified as a miR-9-3p target with luciferase reporter assays. Glioma cells transfected with miR-9-3p mimics or HERPUD1-RNAi had more apoptotic cells than them in control after induced by H₂O₂. Our results indicated that low expression of miR-9-3p results in a high level of Herpud1, which may protect against apoptosis in glioma.

Medulloblastoma: Molecular Classification-Based Personal Therapeutics

Recent advances in cancer genomics have revealed 4 distinct subgroups of medulloblastomas, each with unique transcription profiles, DNA alterations and clinical outcome. Molecular classification of medulloblastomas improves predictions of clinical outcome, allowing more accurate matching of intensity of conventional treatments with chemotherapy and radiation to overall prognosis and setting the stage for the introduction of targeted therapies.

Over-expression of miR-145 enhances the effectiveness of HSVtk gene therapy for malignant glioma

This study attempts to combine two findings toward developing a rational strategy for improved therapy for glioma. One of the findings, made in this pre-clinical study, is that an hTERT-targeting ribozyme-controlled HSVtk gene (hTERT.Rz.HSVtk) exerts anti-tumor effects. The second observation is that the over-expression of a small noncoding RNA, miR-145, causes down-regulation of metastasis-related genes, such as PLAUR, SPOCK3, ADAM22, SLC7A5 and FASCN1. While blocking in vivo tumor growth only slightly, over-expression of miR-145 significantly inhibits both the migration and invasion of U87MG/U373MG glioma cells. We hypothesized that a simultaneous adenoviral-mediated over-expression of miR-145 might enhance the anti-tumor effects of hTERT.Rz.HSVtk and that a combination therapy with miR-145 and the HSVtk gene would be an effective approach for treating glioma. We tested this by developing adenoviral vectors that over-express miR-145 under the CMV promoter and employing them in combination with hTERT.Rz.HSVtk expression, both in vitro and in vivo in animal studies. We found that the adenovirus Ad5CMV.Rz.HSVtk.miR145 harboring an HSVtk expression cassette plus miR-145 produced prolonged survival benefits compared to administration of Ad5CMV.Rz.HSVtk or Ad5CMV.miR-145 alone. This study demonstrates that combination therapy using the hTERT.Rz.HSVtk gene together with miR-145 over-expression produces enhanced anti-tumor effects compared to that resulting from hTERT.Rz.HSVtk gene therapy alone.

Pediatric brain tumors: genetics and clinical outcome

OBJECT

In this paper the authors' goal was to investigate the genetic characteristics of primary brain tumors in children and determine their influence on clinical outcome.

METHODS

The authors performed high-resolution comparative genomic hybridization studies in 14 low-grade and 12 high-grade brain neoplasms in 26 children who underwent surgery between 2005 and 2007.

RESULTS

Complex comparative genomic hybridization alterations were observed in 2 (14.3%) of the 14 lowgrade lesions and in 8 (66.6%) of the 12 high-grade lesions. High-level amplifications of DNA were detected in 3 cases, namely in a desmoplastic medulloblastoma where a c-Myc amplification was found. Gains of 1q were detected in 2 low-grade and 6 high-grade lesions that were classified as ependymomas, astrocytomas, oligodendrogliomas, oligoastrocytomas, and gangliogliomas. When the authors correlated genetics with outcome, they noted that among the low-grade neoplasms only the 2 patients who presented with complex comparative genomic hybridization alterations had to undergo reoperation because of recurrent disease. The patient with c-Myc amplification died of progressive disease. Gains of 1q were only observed in tumor cases with progressive disease.

CONCLUSIONS

Complex genetic alterations are indicative of a less favorable outcome in low-grade tumors. In these cases, closer follow-up should be pursued. The authors corroborate that c-Myc amplification is a marker of poor prognosis in medulloblastomas. In this study, they were able to verify that a 1q gain correlates with a poor clinical outcome, independent of tumor grade and histological type. The authors propose that it may be considered a common marker of poor prognosis in these neoplasms.

Glioma stem cells: a midterm exam

Several years ago, the discovery of a highly tumorigenic subpopulation of stem-like cells embedded within fresh surgical isolates of malignant gliomas lent support to a new paradigm in cancer biology--the cancer stem cell hypothesis. At the same time, these "glioma stem cells" seemed to resolve a long-standing conundrum on the cell of origin for primary cancers of the brain. However, central tenets of the cancer stem cell hypothesis have recently been challenged, and the cellular origins of stem-like cells within malignant glioma are still contended. Here, we summarize the issues that are still in play with respect to the cancer stem cell hypothesis, and we revisit the developmental origins of malignant glioma. Do glioma stem cells arise from developmentally stalled neural progenitors or from dedifferentiated astrocytes? Five separate predictions of a neural progenitor cell of origin are put to the test.

Medulloblastoma in childhood: new biological advances

Medulloblastoma is the most common embryonal tumour in children. Patients with medulloblastoma are currently staged as average-risk or poor-risk on the basis of clinical findings. With current multimodality therapy, nearly 90% of children with average-risk, non-disseminated medulloblastoma have 5-year event-free survival, and those with high-risk disease have a 60-65% survival rate; however, the outcome for younger children, particularly infants, is worse. Children who survive medulloblastoma are at risk of long-term sequelae related to the neurological effects of the tumour, surgery, or radiotherapy, and the additive effects of chemotherapy. Molecular biology has changed our understanding of medulloblastoma and has implications for diagnostic stratification and treatment. As newer biological agents are translated from the lab to the bedside, clinicians need to understand the fundamental signalling pathways that are targeted during therapy. Greater understanding of the molecular biology of medulloblastoma is needed so that more children can be cured or have an improved quality of life.