(The Best Years in Life) Normally, oxygen helps with normal programmed cell death. That is due to the oxidative damage caused by reactive oxygen species (ROS). ROS are chemically reactive molecules containing oxygen. Examples include oxygen ions and peroxides. ROS are formed as a natural byproduct of the normal metabolism of oxygen. As part of the cancer process cancer cells revert to a primitive form of respiration which uses glucose instead of oxygen. As a result, they no longer take in oxygen like healthy cells do. Read More.