Administration of exogenous catalase as a cancer therapeutic has been proposed to modulate the tumor microenvironment (TME) by: 1) decreasing oxidative stress by reducing the level of hydrogen peroxide and 2) decreasing hypoxia by increasing the amount of oxygen [[2], [3], [4], [5], [6], [7], [8], [9], [10]]. The gene discussed is CAT; the disease is cancer.