Detection of DNA Strand Breaks by Fluroscence Assisted DNA Unwinding (FADU) Assay in Hela Cells Treated with Berbrine Chloride before Exposure to Various Doses of γ - Radiation

Ionizing radiations are in frequent clinical use for diagnosis and treatment and the fact is that 50% of the patients visiting Cancer Treatment Centers for cancer therapy receive radiotherapy either alone or in conjunction with chemotherapy [1,2]. The radiotherapy and chemotherapy both kills tumor cells by inflicting damage to cellular DNA and it is also known that the underlying cause of cancer is the induction of mutations into DNA by physical or chemical agents [3-5]. The DNA damaging agents, including ionizing radiations and interstrand DNA cross-linking compounds have been used alone or as a combined treatment modality against cancer due to their extreme DNA damaging ability on proliferating cells. The efficacies of radiation therapy and chemotherapy as well as the mutagenic potential of the DNA damaging agents used in these therapies are modulated by the ability of cells to repair the inflicted DNA damage [6]. Investigation of the molecular mechanisms of DNA damage repair and maintenance of genome stability and their biological effects are important. One of the most genotoxic DNA lesions that results from treatment with ionizing radiation or DNA cross linking compounds is the DNA double-strand break (DSB). DSBs are caused not only by exogenous sources but also by endogenous sources such as radicals generated during metabolic processes [4,5]. In addition, a predominant source of DSBs in dividing cells is the process of DNA replication itself. Since DNA strand breaks play an important role in mutagenesis and oncogenesis, their dose–effect relationships and their rejoining kinetics are essential indicators that reflect cellular response processes [6-8]. In addition to the primarily induced DNA breaks many other DNA lesions may be transformed into strand breaks by cellular repair processes and can thus easily be measured and quantified [4,5].