Extrachromosomal DNA (ecDNA) as Diagnostic Biomarkers for Cancers

Extrachromosomal DNA (ecDNA) has emerged as a critical biomarker in cancer due to its role in oncogene amplification (e.g., MYC, EGFR), tumor heterogeneity, and drug resistance. Present in body fluids as circular DNA, double minutes, or telomeric circles, ecDNA drives aggressive cancer progression by enhancing transcriptional activity and enabling rapid genetic adaptation. This chapter explores the diagnostic potential of ecDNA and current detection methodologies. Its detection offers a non-invasive approach for early cancer diagnosis and prognosis. Current methods include fluorescence in situ hybridization (FISH), which targets AT-rich ecDNA regions using DAPI staining, and scanning electron microscopy for high-resolution imaging. Liquid biopsy stands out for its clinical utility, detecting ecDNA in blood to monitor tumor dynamics and therapy resistance. Despite its promise, challenges like sensitivity limitations and standardization hinder widespread adoption. Future advancements in sequencing and single-cell technologies may overcome these barriers, positioning ecDNA as a transformative tool in precision oncology.