In contrast to chromosomal DNA, which is replicated and divvied up equally among daughter cells during cell division, the extrachromosomal DNA (ecDNA) found in some cancer cells is not always split evenly. Lacking centromeres, these circular bits of DNA are often unevenly parceled to daughter cells. Some daughter cells receive more ecDNA, which they then duplicate, so the copy number of oncogenes in those cells rises quickly. Moreover, because each cell division is essentially a “coin flip” with regard to ecDNA inheritance, variation among the cancerous cell population is preserved, providing an ample supply of the fuel needed for natural selection. These two features in combination could enable cancers containing ecDNA to evolve much more rapidly than cancers lacking ecDNA can.
The circular nature of ecDNAs can enable gene interactions that may support the increased transcription of oncogenes, as genetic elements normally found in distant parts of the genome may ...
