Nucleases are a group of enzymes that cleave the phosphodiester bonds in nucleic acids. As such, nucleases act as biological scissors that exhibit a plethora of fundamental roles, in prokaryotes and eukaryotes, dependent or non-dependent on their catalytic capability. Thus, differential status of nucleases between healthy and disease conditions might not be surprising, and can be deployed in disease detection. Specifically, there is growing body of research demonstrating the potential of nucleases as diagnostic biomarkers in several types of cancer. Biomarkers for early diagnosis are an immense need in the diagnostic landscape of cancer. In this sense, nucleases are promising biomolecules, and they possess a unique feature of catalytic activity that could be deployed for diagnosis and future therapeutic strategies. In this thesis we aim to demonstrate the use of nucleases as biomarkers associated to cancer, and the capability of oligonucleotide substrates for targeting a specific nuclease.xiii I am deeply grateful to my lovely family, my supporter in all my endeavors. Thank you, Mom, Dad and Alexan for all your love, encouragement and believing in me. Mom, I deeply appreciate your unlimited love and care for me and Ella, and I am beyond thankful for always being there when I needed time to focus on my work and writing.I want to give a big thanks to my husband Rami for encouraging me to take this path, and for his love and support all the way. I am lucky and beyond grateful for having you by my side. Big thanks also to my daughter Ella who opened my heart to new horizons of love. Thank you for being my sweetest supporter ever, especially when you say "Jag vill bli som du mamma". And I want to say what I always tell you: Jag älskar dig så mycket. Norrköping, December 2022 Alien Balian xv Papers Included in the Thesis I. Nucleases as Molecular Targets for Cancer Diagnosis Balian A., Hernandez FJ. Biomark Res., (2021), 9(1):86.Author's contribution: AB has conducted literature search, written all the sections, made the initial design of the figures and responded to the reviewers' comments to edit the paper.