HMOX1 and cancer: On one hand, however, in cancer cells, Nrf2 inhibition confers radiosensitizing effects through inhibiting ROS scavenging, promoting DNA damage as well as reducing the expression of downstream target protein including NQO1 and HO-1 or cross-talk with other signal molecules like HIF-1 and NF-κB. On the other hand, in normal cells, downregulation of Nrf2 may induce radiotoxicity, thereby strengthening radiation-induced injury.