Exosomes, small membrane vesicles (30-100 nm) secreted by cells, contain functional biomolecules and can transfer between cells. This study demonstrates that tumor-derived exosomes contain double-stranded DNA (dsDNA), which represents the entire genome of the parent tumor cells and reflects their mutational status. Using enzymatic and physical methods, the researchers showed that dsDNA is the predominant form of DNA within exosomes, with a significant reduction in DNA size after digestion with dsDNase. They also found that exosomal DNA (exoDNA) is more stable and less affected by digestion compared to genomic DNA (gDNA). ExoDNA was shown to carry mutations present in the parental tumor cells, such as the BRAF V600E mutation in melanoma and EGFR mutations in non-small cell lung cancer (NSCLC). These findings suggest that exoDNA could serve as a circulating biomarker for cancer detection and monitoring treatment response. The study also highlights the potential of exoDNA as a non-invasive tool for early cancer detection and as a potential therapeutic target. The research was supported by various grants and acknowledges contributions from multiple institutions and individuals. The study provides a comprehensive analysis of exoDNA, showing its potential as a novel biomarker in cancer detection.Exosomes, small membrane vesicles (30-100 nm) secreted by cells, contain functional biomolecules and can transfer between cells. This study demonstrates that tumor-derived exosomes contain double-stranded DNA (dsDNA), which represents the entire genome of the parent tumor cells and reflects their mutational status. Using enzymatic and physical methods, the researchers showed that dsDNA is the predominant form of DNA within exosomes, with a significant reduction in DNA size after digestion with dsDNase. They also found that exosomal DNA (exoDNA) is more stable and less affected by digestion compared to genomic DNA (gDNA). ExoDNA was shown to carry mutations present in the parental tumor cells, such as the BRAF V600E mutation in melanoma and EGFR mutations in non-small cell lung cancer (NSCLC). These findings suggest that exoDNA could serve as a circulating biomarker for cancer detection and monitoring treatment response. The study also highlights the potential of exoDNA as a non-invasive tool for early cancer detection and as a potential therapeutic target. The research was supported by various grants and acknowledges contributions from multiple institutions and individuals. The study provides a comprehensive analysis of exoDNA, showing its potential as a novel biomarker in cancer detection.