https://www.selleckchem.com/products/SB590885.html Elevation of the level of intracellular reactive oxygen species (ROS) has immense implication in the biological system. On the one hand, ROS promote the signaling cascades for the maintenance of normal physiological functions, the phenomenon referred to as redox biology, and on the other hand increased ROS can cause damages to the cellular macromolecules as well as genetic material, the process known as oxidative stress. Oxidative stress acts as an etiological factor for wide varieties of pathologies, cancer being one of them. ROS is regarded as a "double-edged sword" with respect to oncogenesis. It can suppress as well as promote the malignant progression depending on the type of signaling pathway it uses. Moreover, the attribution of ROS in promoting phenotypic plasticity as well as acquisition of stemness during neoplasia has become a wide area of research. The current review discussed all the aspects of ROS in the perspective of tumor biology with special reference to epithelial-mesenchymal transition (EMT) and cancer stem cells. OBJECTIVE To discuss the major milestones in the history of clinical research and how these correlate with the role of the clinical research nurse. DATA SOURCES Government Web sites, published articles, and grey literature. CONCLUSION The history of clinical research, drug development, and the regulations has come of age, and as a result clinical oncology research has a more defined scope and purpose. With the Oncology Nursing Society and the International Association of Clinical Research Nurses recognizing the scopes of practice for clinical research nursing, such roles are becoming more prevalent and integrated in oncology. IMPLICATIONS FOR NURSING PRACTICE It is vital for all clinical research nurses to understand and adhere to the laws and regulations related to clinical trials and human subject protection. The clinical research nurse must ensure good clinical practice and complianc