Cancer is a complex disease resulting from various genetic changes that lead to disorders in the mechanisms regulating the basic functions of the cell. As a result of these genetic changes, it is a disease characterized by the fact that new cancer cells are constantly formed and cannot be destroyed by disrupting the cell cycle. Cancer is one of the main causes of deaths worldwide. It causes approximately 9 million deaths annually. Many different treatment modalities are applied in cancer treatment to decrease mortality and increase survival. There are three main approaches in cancer treatment: chemotherapy, radiotherapy and surgical methods. In chemotherapy, which is the most commonly used method among these, while apoptosis of cancer cells is targeted with chemical agents, it is also prevented from stopping the cancer by spreading. However, new approaches to cancer treatment are still being investigated today, since existing drugs cause high toxicity, undesirable side effects and drug resistance. An important goal of current researchs is the development of new, more specific chemotherapeutics and the identification of new biological targets, especially for the most aggressive tumors. DNA topoisomerases are among the various molecular targets for cancer treatment. Cell proliferation are well-characterized targets due to their essential role in differentiation and survival. These enzymes change the three dimensional structure of DNA without affecting chemical structure through transient breaks. They are divided into two subclasses as type I and type II according to their fracture formation on a single chain or double chain.
Topoisomerase I, Topoisomerase II, Cancer.