PhD Defence: Peng Han

Thesis title: Function and potential clinical application of circular DNA in cancer

Supervisor: Birgitte Regenberg

Assessment committee:
Michael Lisby, (chair), Department of Biology, University of Copenhagen
Sihan Wu, IT Southwestern, USA
Nicola Crosetto, Milan, Italy

Abstract:
Extrachromosomal circular DNA (eccDNA) has been detected across a broad spectrum of eukaryotes species, from yeast to humans, underscoring its evolutionary conservation, and suggesting its potential roles in cellular functions. The evolution of cancer cells has been linked to genomic mutations, including eccDNA that carry oncogenes. However, while previous studies have primarily focused on the function of large amplified eccDNA (1 to 3 Mb in size) with oncogenes, comprehensive understanding of eccDNA across both small and large sizes remains incomplete. In my work, I present eccDNA profiles across three cancer types: renal, bladder, and gastric cancer. I describe a method for investigating eccDNA function, and report on a pilot study investigating eccDNA in human urine biopsy of healthy individuals and chronic kidney disease patients. Using these approaches, I investigate the role of circularized genes on eccDNA in cancers and assess the feasibility of developing urinary biomarkers based on eccDNA.