Reactive Oxygen Species: Central Regulators of the Tumor Microenvironment: An Immuno-Oncology Perspective

Reactive oxygen species (ROS), a group of molecules generated by partial reduction of oxygen, have been postulated as central regulators of essential cellular functions through the modulation of signaling pathways activity. Excessive production of ROS, also known as oxidative stress, is a common feature of tumor microenvironment (TME). A large number of studies have provided strong evidence supporting a role of oxidative stress in the regulation of tumor development and progression through the modulation of the TME. In this chapter, we summarize the state of the field as it relates to causes and consequences of ROS elevation in the TME. In addition, we describe the molecular and biological mechanisms governing the intricate network of events driven by oxidative stress leading to an immunosuppressed TME. Finally, we discuss the translational significance of ROS induction as new therapeutic strategies with an emphasis in the role of photodynamic therapy, as a ROS-based potent antitumor agent regulating inflammation and immune system activation during tumor progression.