In irradiated A549 lung cancer cells, PGE2, released in the tumor microenvironment, promoted the survival of neighboring non-irradiated cells by enhancing antioxidant defenses through the Nrf2-mediated upregulation of the antioxidant enzyme heme oxygenase-1 (HO-1) [12]. The gene discussed is HMOX1; the disease is lung carcinoma.