Interestingly, the association between HIF-1α and ARNT can also be inhibited by interaction of HIF-1α with MgcRacGAP (male germ cell RacGTPase Activating Protein) in cancer cells [39,40] or after treatment of human bronchial smooth muscle cells with the proinflammatory factor TNF-α [11]. Here, HIF1A is linked to cancer.