Glucagon-like peptide-1 (GLP-1) molecular forms in human pancreatic endocrine tumors resemble those in intestine rather than pancreas.

Different glucagon-like peptide-1 (GLP-1) molecular forms are produced in the pancreas and the small intestine by differential processing of proglucagon. In this report, molecular forms of GLP-1 in two human pancreatic endocrine tumors were studied and compared with those in the pancreas and small intestine. A predominant GLP-1 immunoreactive form in the pancreas was eluted at the position of GLP-1(1-36) amide, whereas a predominant immunoreactive form in the ileal mucosa was eluted at the position of GLP-1(7-36) amide. In a glucagonoma, GLP-1 immunoreactive forms corresponding to GLP-1(7-36) amide and GLP-1(7-37) were predominant and immunoreactive forms at the position of GLP-1(1-36) amide and GLP-1(1-37) were minor. In another tumor, an insulinoma, immunoreactive forms were detected at the positions of GLP-1(7-36) amide, GLP-1(7-37), GLP-1(1-36) amide and GLP-1(1-37). Thus, the pattern of GLP-1 molecules in pancreatic tumors was not a pancreatic pattern and mimicked that found in the small intestine or consisted of both the patterns found in the small intestine and the pancreas. These data suggest that neoplastic transformation of the islet cells is associated with a switching in processing phenotype from islet (A) cells to intestinal (L) cells.