Amplifications in this series included MYCL, MYCN and MYC previously implicated in medulloblastoma pathogenesis, as well as novel amplicons on chromosomes 2, 4, 11 and 12.
Additional analysis by interphase fluorescence in situ hybridisation (iFISH), PCR-based mapping and SNP-array revealed this novel amplification at 8q24.22-q24.23 is independent of MYC amplification at 8q24.21, and is unique to medulloblastoma in over 800 cancer cell lines assessed from different tumour types, suggesting it contains key genes specifically involved in medulloblastoma development.
We show that bromodomain inhibition with JQ1 restricts c-MYC driven transcriptional programs in medulloblastoma, suppresses medulloblastoma cell growth and induces a cell cycle arrest.
Finally, the positive correlation of MYC and JAG2 also with aggressive anaplastic tumors and highly metastatic MB stages suggested that high JAG2 expression may be useful as additional marker to identify aggressive MBs.
Both anaplasia and increased c-myc gene expression have been shown to be negative prognostic indicators for survival in medulloblastoma patients. myc gene amplification has been identified in many large cell/anaplastic medulloblastoma, but no causative link between c-myc and anaplastic changes has been established.
The MYC oncogenes are the most commonly amplified loci in medulloblastoma, and have previously been proposed as biomarkers of adverse disease prognosis by us and others.
This study highlights B7-H3 as a viable target in MB angiogenesis, and that the expression of miR-29 can inhibit B7-H3 and sensitize MB cells to treatment with MYC-inhibiting drugs.
Most children with medulloblastoma fall within the standard-risk clinical disease group defined by absence of high-risk features (metastatic disease, large-cell/anaplastic histology, and MYC amplification), which includes 50-60% of patients and has a 5-year event-free survival of 75-85%.
Chemical genomic profiling of QHii066-treated medulloblastoma cells confirmed inhibition of MYC-related transcriptional activity and revealed an enrichment of HOXA5 target gene expression. siRNA-mediated knockdown of HOXA5 markedly blunted the response of medulloblastoma cells to QHii066.
Immunohistochemical and molecular data (c-myc gene amplification and the presence of isochromosome 17q) support the contention that this histologically diverse tumor represents a pattern of medulloblastoma with striated muscle and pigmented epithelial differentiation, rather than a teratoma or a cerebellar variant of melanotic neuroectodermal tumor of infancy ('progonoma').
Human MYC-amplified (Med8A and D283) and non-amplified (UW228-2 and ONS76) MB cell lines were incubated for 2, 4 or 6 h with increasing doses (0-100 μg/ml) of 5-ALA, and PPIX accumulation was determined by flow cytometry.
Antisense-based knockdown of miR-512-5p (mature sequence of miR-512-2) resulted in significant upregulation of MYCC expression in HeLa and A549 cells, while forced overexpression of miR-512-2 in medulloblastoma/PNET cell lines DAOY, UW-228-2, PFSK resulted in the downregulation of MYCC protein.
MYCC and MYCN oncogene amplification in medulloblastoma. A fluorescence in situ hybridization study on paraffin sections from the Children's Oncology Group.
The association of clinically aggressive medulloblastoma with MYC expression, large cell/anaplastic change and high levels of photoreceptor differentiation transcripts has also been noted in several studies.