Pretorius, P.J.Aucamp, Janine2018-07-182018-07-182017http://hdl.handle.net/10394/28548PhD (Biochemistry), North-West University, Potchefstroom Campus, 2018Newly synthesised, actively released circulating DNA can translocate to neighbouring and remote parts of the body, enter cells and alter their biology. It has been implicated in the bystander effect, tumour development and metastasis, the blocking of tumour growth, and the spread of antibioticand chemoresistance, as well as bacterial and viral virulence. This raises the question of whether these intercellular messaging functions of circulating DNA can have clinical implications. There is little preventing the transfer of circulating DNA from donors to recipients during blood transfusions, making it possible that information contained in the circulating DNA of donors can elicit genetic, epigenetic and/or biochemical effects in recipients. Utilising both two- and threedimensional cell cultures and valproic acid, paracetamol and natural plant products, this thesis demonstrates the transfer of pharmaceutically-induced biochemical and epigenetic effects from donor to recipient cells via cell-free DNA. This observed lateral transfer of information in vitro emphasises the clinical risk of similar events occurring during the transfusion of biological fluids, such as blood products. Furthermore, the thesis motivates the utilisation of cell-free DNA from the growth medium of in vitro cultures in conjunction with in vivo models. It is illustrated that restricting the cellular environment to the cell types, physiological system, organ or disease in question can significantly simplify the search for biomarkers and the elucidation of the biological functions of circulating DNA. In particular, the utilisation of three-dimensional cell culture technologies, in this case using spheroids developed via microgravity bioreactors, in circulating DNA research is introducedenCell-free DNACirculating DNAClinical implicationsIntercellular messengerLateral information transferBlood donationValproic acidThesis