ecDNA in Oncogene Amplification and Tumor Progression

In several cancers, extrachromosomal DNA (ecDNA) has become a key factor in tumor development and oncogene amplification. The circular, acentric DNA fragments that make up ecDNA, in contrast to linear chromosomal DNA, multiply on their own and frequently contain amplified oncogenes, including MYC, EGFR, and CDK4. Through the facilitation of fast gene dosage variation, high-level transcriptional activity, and epigenetic plasticity, these structures give tumor cells selection benefits. In addition to promoting clonal evolution, immunological evasion, and phenotypic diversity, ecDNA promotes significant intratumoral heterogeneity, all of which are factors in aggressive tumor behavior and a poor prognosis. Crucially, ecDNA promotes dynamic adaptability under therapeutic pressure, which is essential for the development of drug resistance and the failure of targeted therapies. This chapter describes ecDNA’s molecular makeup, biosynthesis, and transcriptional regulation, highlighting how it speeds up tumor growth, metastasis, and treatment resistance. Furthermore, ecDNA is becoming a therapeutic target and diagnostic biomarker in precision oncology. Limiting tumor plasticity and overcoming therapeutic resistance may be possible through novel approaches that target ecDNA-specific pathways. Understanding the biology of ecDNA has the potential to revolutionize next-generation cancer diagnostics and therapy paradigms in addition to improving our understanding of the dynamics of the cancer genome.