Extrachromosomal DNA (ecDNA) is a key driver of cancer progression and treatment resistance, as revealed by a comprehensive analysis of 14,778 patients across 39 tumor types. ecDNA refers to large, circular DNA molecules found outside chromosomes that can amplify oncogenes, immune-modulatory genes, and regulatory elements. This study highlights that ecDNA was detected in 17.1% of tumor samples, varying by cancer type, and was most prevalent in aggressive forms like glioblastoma and HER2-positive breast cancer. These structures contribute to intratumoral genetic heterogeneity by promoting high oncogene copy numbers and enabling rapid genetic evolution, which facilitates treatment resistance and disease progression.
The research uncovers distinct ecological and genetic signatures associated with ecDNA. Its formation and progression are influenced by intrinsic factors such as mutations in tumor suppressor genes like TP53 and environmental exposures such as tobacco use. Notably, the study finds that ecDNA often contains immunomodulatory genes, leading to reduced T-cell infiltration and immune suppression in tumors. This mechanism helps explain why cancers with ecDNA are less responsive to immunotherapies.
Regulatory ecDNA, a subset containing only non-coding regions like enhancers and promoters, plays a role in gene regulation by interacting with other ecDNA to drive high levels of gene expression. These regulatory elements are often co-amplified with oncogene-containing ecDNA, highlighting their cooperative potential in cancer progression.
Clinical analysis reveals that ecDNA is associated with advanced tumor stages, metastases, and shorter survival times. Its prevalence increases after chemotherapy and targeted therapies, indicating its role in treatment resistance. These findings emphasize the clinical challenge posed by ecDNA and its potential as a target for new therapies. By illuminating the diverse roles of ecDNA in cancer, this research provides a foundation for better understanding tumor evolution and identifying novel treatment strategies.
Bailei at al., Origins and impact of extrachromosomal DNA. Nature Nov;635(8037):193-200. https://www.nature.com/articles/s41586-024-08107-3
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