Figure 2.

Schematic representation of the homeostatic role of ROS and their pathologic role in tumor growth and cell death. Low production of ROS and balanced antioxidant activity play a fundamental role in cellular signaling and repair resulting in controlled growth and survival. Proliferation of tumor cells yields elevated ROS concentrations enhancing cell survival and proliferation leading to DNA damage and genetic instability causing cell dysfunction. Chemotherapeutic agents and radiotherapy increase ROS production to toxic concentrations resulting in irreparable damage to the cell, inadequate adaptations and eventually cell death. The heart is particularly vulnerable to ROS/RNS injury because antioxidant resources are lower than other tissues. Modified with permission from Moloney and Cotter (2017).