KRAS and pancreatic adenocarcinoma: However, in both instances, functions seem to differ: For miR-126, reduced expression resulting in KRAS elevation has been reported for pancreatic adenocarcinoma [29]; for miR-155, overexpression was associated with carcinoma progression, indicating a tumorigenic role [30] while miR-155 downregulation has also been reported (in pNEN) [22, 23].