STAT3 and pancreatic ductal adenocarcinoma: Disruption of the IL-6 gene and conditional inactivation of STAT3 reduced progressive pancreatic intraepithelial neoplasia (PanIn) lesion and pancreatic ductal adenocarcinoma formation in mutant K-ras-transgenic mice [65,166], suggesting that STAT3 activity is required for the development of the earliest premalignant pancreatic lesions, acinar-to-ductal metaplasia, and PanIN and for the progression from PanIN to invasive pancreatic ductal adenocarcinoma [65].