Autophagy, Reactive Oxygen Species, and Tumorigenesis

Tumorigenesis is a multistep process which requires healthy cell to transform into uncontrolled growing mass of cells. Healthy cells have inherent property and police to regulate such transformation. These regulatory phenomena get distorted in the process of tumorigenesis. Several external and internal stimuli or carcinogens promote these cells to become tumor cells. A tumor cell acquires limitless DNA replication, unchecked proliferative state, insensitivity toward cell cycle regulation, disabled apoptosis, active angiogenesis, invisibility to immune cells, and deranged autophagy. Autophagy is a lysosome-mediated process to regulate and maintain healthy state of a cell by removing damaged cell organelles and/or pathogens. Autophagy is also triggered by oxidative stress and DNA damage caused by reactive oxygen species (ROS). Thus, a failure in normal autophagy has a crucial role in tumor initiation and development. This chapter discusses the deranged interplay between autophagy and ROS leading to tumorigenesis.