Extrachromosomal DNA driven oncogene spatial heterogeneity and evolution in glioblastoma

MagnusHaughey

Barts Cancer Institute

"Extrachromosomal DNA driven oncogene spatial heterogeneity and evolution in glioblastoma"

Extrachromosomal DNA (ecDNA) oncogene amplification is associated with treatment resistance and shorter survival in cancer. Currently, the spatial dynamics of ecDNA, and their evolutionary impact, are poorly understood. Here, we investigate ecDNA spatial-temporal evolution by integrating computational modeling with samples from 94 treatment-naive human IDH-wildtype glioblastoma patients. Random ecDNA segregation combined with ecDNA-conferred fitness advantages induce predictable spatial ecDNA copy-number patterns which depend on ecDNA oncogenic makeup. EGFR-ecDNAs often reach high copy-number, confer strong fitness advantages and do not co-amplify other oncogenes on the same ecDNA. In contrast, PDGFRA-ecDNAs reach lower copy-number, confer weaker fitness advantages and co-amplify other oncogenes. EGFR structural variants occur exclusively on ecDNA, arise from and are intermixed with wild-type EGFR-ecDNAs. Modeling suggests wild-type and variant EGFR-ecDNAs often accumulate before clonal expansion, even in patients co-amplifying multiple ecDNA species. Early emergence of oncogenic ecDNA under strong positive selection is confirmed in vivo and in vitro in mouse neural stem cells. Our results implicate ecDNA as a driver of gliomagenesis, and suggest a potential time window in which early ecDNA detection may facilitate more effective intervention.
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