Abstract: The present invention refers to a method for inducing tumor apoptosis by influencing the ROS (reactive oxygen species) signaling pathway in tumor cells. Increasing the level of ROS leads to the selective inactivation of a tumor cell catalase and subsequently to an apoptosis of these cells. The level of ROS can be increased by increasing the level of nitric oxide through inhibition of the enzymes nitric oxide dioxygenase or arginase. According to the present invention inhibitors of the nitric oxide dioxygenase or arginase can be used for the manufacture of a medicament for the treatment of cancer. The present invention further provides a method for identifying compounds which can be used for the treatment of cancer, wherein the method allows to specifically identify compounds which induce apoptosis through the ROS signaling pathway. The present invention also provides a kit for identifying compounds which induce tumor apoptosis by inactivating a catalase on the tumor cell surface.