Along the same line, when a HIF-1α-derived polypeptide (dnHIF-1α; aa 30-389) containing the bHLH and PAS domain was expressed in pancreatic adenocarcinoma cell lines it acted as a dominant negative mutant (apparently by forming an DNA-binding but inactive complex with ARNT) as it reduced binding of endogenous HIF-1 to its target promoters and, subsequently, inhibited its activity. This evidence concerns the gene HIF1A and pancreatic adenocarcinoma.