ARNT and melanoma: The requirement of HIF-1α to elevate ARNT under hypoxic conditions in Hep3B cells strongly parallels a mechanism already demonstrated in 518A2 human melanoma cells.17 In this cell line the same regulatory relationship between HIF-1α and its binding partner ARNT was described.17 Whether this cellular trait relies on the same mechanism or is the outcome of different alterations in both cell models is unclear.