Insulin-like growth factor-II in endocrine pancreatic tumours - Immmunohistochemical, biochemical and in situ hybridization findings

In earlier studies a high-molecular-weight (HMW) insulin-like,growth factor -II (IGF-II) peptide was identified in adult human pancreas and localized t o the insulin-producing B-cells. This peptide has now been investigated in neoplastic insulin cells. Forty endocrine pancreatic tumours and 17 pancrea tic adenocarcinomas of ductal type were included in the study. All cases we re investigated with immunohistochemical techniques using antibodies to IGF -II, insulin, pro-insulin, glucagon, somatostatin, pancreatic polypeptide, gastrin and vasoactive intestinal peptide (VIP). Frozen tissue from nine tu mours and two normal pancreatic glands was extracted, gel separated, and qu antified using radioimmunoassay. The tumours were also investigated by in s itu hybridization. IGF-II-immunoreactive cells were found in nearly all the 18 insulin-producing tumours (16/18), in a minority of the other endocrine tumours, but not in pancreatic adenocarcinomas. All extracts from the endo crine tumours showed varying amounts of IGF-II and had different molecular- weight forms. The immunohistochemical and radioimmunoassay findings are bot h based on immunological binding and were further confirmed by Northern blo t and in situ hybridization. These results show that IGF-II is expressed in insulin-producing tumours as well as in pancreatic tumours producing other peptides, in contrast to normal pancreatic islets where IGF-II is found ex clusively in insulin-producing cells.