Immunocytochemical Localization of Prohormone Convertase 1/3 and 2 in Pancreatic Islet Cells and Islet Cell Tumors

Abstract

Peptide hormones are synthesized as bigger prohormones, which are processed posttranslationally into smaller active hormones. Proinsulin and proglucagon are processed into insulin and glucagon by prohormone convertase (PC) 1/3 and 2. The current study was performed to test a hypothesis that there may be some difference in immunoreactive PC levels between normal islet cells and islet cell tumors, as the latter contain more prohormones than the former. All islet cell tumors, including insulinomas, gastrinomas, glucagonomas, pancreatic polypeptide-omas (PP-omas), and nonfunctioning islet cell tumors, contain fewer PCs than normal islet cells. The smaller PC levels in islet cell tumors may be responsible for the higher levels of prohormones in islet cell tumors, and the smaller levels of PCs in islet cell tumors may be another distinguishing characteristic of islet cell tumors.