HMOX1 and cancer: Traditionally considered as the master regulator of cytoprotective responses against exogenous or endogenous stressors, the signal pathway formed by transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf2) and its downstream target gene heme oxygenase-1 (HO-1) has recently been found to promote cancer development, malignant progression, therapy resistance and poor prognosis 4.