ARNT and cancer: HIFs, the master regulators of cellular response to hypoxia, constitute a family of heterodimeric transcription factors composed of one oxygen labile subunit (HIF-1α, -2α or 3α) and a constitutively expressed β subunit HIF-1β (ARNT; aryl hydrocarbon receptor nuclear translocator) and are highly involved in the pathology of cancer and other diseases associated with tissue hypoxia (reduced oxygen tension) [19].