mRNA expression patterns of insulin-like growth factor system components in human neuroendocrine tumours

Background Insulin-like growth factors (IGF) and their corresponding recept ors and binding proteins are important in carcinogenesis for several rumour s, but their expression pattern in the functionally and biologically hetero geneous human neuroendocrine rumours of the gastroenteropancreatic tract is largely unknown. Materials and methods This study searched for the mRNA expression patterns of components of the IGF system: IGF-1 and IGF-2, IGF receptors 1 and 2 (IG F-1R, IGF-2R), IGF-binding proteins 1-6 (IGFBP1-6)) in the most frequent hu man gastroenteropancreatic neuroendocrine tumours (gastrinomas, insulinomas , tumours associated with carcinoid syndrome and functionally inactive tumo urs) employing reverse transcriptase-polymerase chain reaction (RT-PCR). Results In the 37 tumour samples analysed (nine gastrinomas, 10 insulinomas , nine tumours associated with carcinoid syndrome and nine functionally ina ctive rumours) IGFBP-2 was found in all tumour samples while the IGFBP-1 wa s expressed only at low frequency (10-22%) among the four tumour types. The IGF-2R was predominantly expressed in gastrinomas. Among the four tumour t ypes the expression of IGF-1R, IGF-2R and IGFBP-6 varied significantly. In addition, 12 pairs of significantly coexpressed IGF system components were detected (IGF-1 <----> IGF-1R, IGF-1 <----> IGF-2R, IGF-1 <----> IGFBP-3, I GF-1 <----> IGFBP-6, IGFBP-3 <----> IGF-1R, IGFBP-6 <----> IGF-1R, IGFBP-1 <----> IGF-2R, IGFBP-3 <----> IGF-2R, IGFBP-5 <----> IGF-2R, IGFBP-3 <----> IGFBP-5, IGFBP-3 <----> IGFBP-6, IGFBP-5 <----> IGFBP-6). Conclusions The described differences of the expression patterns of the IGF system components in neuroendocrine tumour subtypes suggest tumour type-de pendent different pathways in tumour growth control by IGF system component s.