Besides oxygenation status, ability of repairing DNA damage and cancer cell repopulation following irradiation are also believed to be an important cause of treatment failure.46, 47, 48 If ITPP actually works via a molecular pathway related to PI3K signaling, then the radiosensitizing effect of ITPP would be more complicated than just a simple decrease in hypoxia. This evidence concerns the gene TPP1 and cancer.