Neuroendocrine tumours (NETs) may occur in multiple sites including, the pancreas, gastrointestinal tract, lung, thymus, adrenals and pituitary, and as part of the multiple endocrine neoplasia type 1 (MEN1) syndrome. Current treatments for advanced NETs, rarely achieve a cure due to metastases at presentation and therefore additional treatments are required. Identification of cell surface receptors or binding sites that are unique to NETs could lead to novel targeted drugs, radio-isotope or gene therapy treatments. To identify such receptors we used a phage display selection technique in which a library of peptides is expressed on the outside of phage virions encoded by the genetic material inside. Using 20 month old Men1+/− mice, which develop pancreatic NETs (PNETs), three rounds of phage display screening using a 12-mer library (New England Biolabs) were performed with mice that had been previously intravenously administered with clodronate liposomes, to deplete resident macrophages in the liver and spleen, prior to intravenous administration of 1.65×1011 plaque forming units of phage. PNETs were harvested after 3 hours and binding phage identified. From two independent experiments seven peptides emerged after the third round of screening that were recovered on at least three clones, and designated mouse PNETs peptides (MPP) 17 which represented 65%, 24%, 11%, 13%, 3%, 3%, and 3% of clones, respectively. MPP1, when compared with vehicle only or scrambled peptide control, was found to increase murine insulinoma (MIN-6) cell proliferation, assessed by trypan blue exclusion assay, at day 6 by 1.43-fold and 1.43-fold (p<0.05), respectively. Basic Local Alignment Search Tool (BLAST) analysis suggested that MPP1 has homology to the Niemann-Pick C1-like protein 1 precursor which plays a role in cholesterol homeostasis and is known to be expressed in human pancreas. Thus, our studies have identified a peptide that may play a role in targeting NET cells.
07 Nov 2016 - 09 Nov 2016