Cancer is a chronic disease caused by dysregulation of multiple genes and requires more than 25 years for development. Accumulating evidence suggests that reactive oxygen species (ROS) generated inside body under normal physiologic conditions are also critically involved in regulating tumor functions. Recent advancement in free radical biology and tumor biology suggests that ROS control numerous aspects of tumor development such as drug resistance, epithelial-to-mesenchymal transition, and cancer stemness. ROS have been demonstrated to regulate multistep process of tumor development including inflammation, transformation, survival, proliferation, invasion, angiogenesis, and metastasis by activating various oncogenic transcription factors. Paradoxically, ROS also control the expression of various tumor suppressor genes such as p53, Rb, and PTEN. Similarly, γ-radiation and various chemotherapeutic agents used to treat cancer mediate their effects through the production of ROS. This paradox provides a great challenge for researchers whose aim is to exploit ROS stress for the development of cancer therapies. Thus, a thorough assessment of current developments concerning role of ROS in tumor biology is required.

We invite authors around the world to contribute original research articles as well as review articles that will stimulate the continuing efforts to understand the role of ROS in tumor development. We are particularly interested in thought-provoking articles that provide an overview of existing concepts, novel findings, controversies, and challenges concerning the role of ROS in cancer development. Articles on future prospects of targeting ROS associated signaling molecules in cancer therapy are invited.

Potential topics include, but are not limited to:

• ROS and drug resistance
• ROS and multisteps of tumor development
• ROS and cancer therapy
• ROS and cancer stem cells
• ROS and inflammation
• ROS and cancer cell metabolism
• ROS and dietary agents/nutraceuticals