ABSTRACT
The development of targeted anti-cancer therapies through the study of cancer genomes is intended to increase survival rates and decrease treatment-related toxicity. We treated a transposon-driven, functional genomic mouse model of medulloblastoma with 'humanized' in vivo therapy (microneurosurgical tumour resection followed by multi-fractionated, image-guided radiotherapy). Genetic events in recurrent murine medulloblastoma exhibit a very poor overlap with those in matched murine diagnostic samples (<5%). Whole-genome sequencing of 33 pairs of human diagnostic and post-therapy medulloblastomas demonstrated substantial genetic divergence of the dominant clone after therapy (<12% diagnostic events were retained at recurrence). In both mice and humans, the dominant clone at recurrence arose through clonal selection of a pre-existing minor clone present at diagnosis. Targeted therapy is unlikely to be effective in the absence of the target, therefore our results offer a simple, proximal, and remediable explanation for the failure of prior clinical trials of targeted therapy.
Subject(s)
Cerebellar Neoplasms/therapy , Clone Cells/drug effects , Clone Cells/metabolism , Medulloblastoma/therapy , Neoplasm Recurrence, Local/genetics , Neoplasm Recurrence, Local/pathology , Selection, Genetic/drug effects , Animals , Cerebellar Neoplasms/genetics , Cerebellar Neoplasms/pathology , Cerebellar Neoplasms/radiotherapy , Cerebellar Neoplasms/surgery , Clone Cells/pathology , Craniospinal Irradiation , DNA Mutational Analysis , Disease Models, Animal , Drosophila melanogaster/cytology , Drosophila melanogaster/genetics , Female , Genome, Human/genetics , Humans , Male , Medulloblastoma/genetics , Medulloblastoma/pathology , Medulloblastoma/radiotherapy , Medulloblastoma/surgery , Mice , Molecular Targeted Therapy/methods , Neoplasm Recurrence, Local/therapy , Radiotherapy, Image-Guided , Signal Transduction , Xenograft Model Antitumor AssaysABSTRACT
BACKGROUND: Ependymoma is the third most common malignant tumor of the posterior fossa and is a major cause of neurological morbidity and mortality in children. Current treatments, particularly surgery and external beam irradiation result in relatively poor outcomes with significant neurological and cognitive sequelae from treatment. Historical approaches have considered all ependymomas as similar entities based on their morphological appearance. RESULTS: Recent advances in genomics and epigenetics have revealed, however, that ependymomas from different CNS locations represent distinct entities. Moreover, ependymoma of the posterior fossa, the most common location in children, is actually comprised of two distinct molecular variants. These two variants have marked differences in demographics, transcriptomes, structure, methylation patterns, and clinical outcomes. This allows for the development of new biology-based clinical risk stratification, which can both prioritize patients for de-escalation of therapy and identify those who will benefit from novel therapeutic strategies. Indeed, the identification of these two variants allows an opportunity for robust preclinical modeling for development of novel therapeutic strategies. CONCLUSIONS: Herein, we have summarized our current clinical approach to diagnosis and treatment of posterior fossa ependymoma, recent advances in understanding the biology of posterior fossa ependymoma and how these new insights can be translated into the clinic to form the basis of the next generation of clinical trials.