gastrin-17 and Gastrinoma

Gastrin measurements are performed primarily for the diagnosis of gastrin-producing tumors, gastrinomas, which cause the Zollinger-Ellison syndrome (ZES). Gastrin circulates as several bioactive peptides, however, and the peptide pattern in gastrinoma patients often deviates from normal. Therefore, it is necessary to measure all forms of gastrin.. Only immunoassays are useful for measurement of gastrin in plasma. The original assays were RIAs developed in research laboratories that used antibodies directed against the C terminus of gastrin peptides. Because the C-terminal tetrapeptide amide sequence constitutes the active site of gastrin peptides, these assays were well suited for gastrinoma diagnosis. More recently, however, most clinical chemistry laboratories have switched to commercial kits. Because of recent cases of kit-measured normogastrinemia in patients with ZES symptoms, the diagnostic sensitivity and analytical specificity of the available kits have been examined. The results show that gastrin kits frequently measure falsely low concentrations because they measure only a single gastrin form. Falsely high concentrations were also encountered, owing to overreactivity with O-sulfated gastrins or plasma proteins. Thus, more than half of the gastrin kits on the market are unsuited for diagnostics.. Gastrinomas are neuroendocrine tumors, some of which become malignant. A delay in diagnosis leads to fulminant ZES, with major, even lethal, complications. Consequently, it is necessary that the diagnostic sensitivity of gastrin kits be adequate. This diagnostic sensitivity requires antibodies that bind the C-terminal epitope of bioactive gastrins without the influence of O-sulfation.

Topics: Amino Acid Sequence; Antibody Specificity; Biomarkers, Tumor; Gastrinoma; Gastrins; Humans; Immunoassay; Molecular Sequence Data; Reagent Kits, Diagnostic; Sensitivity and Specificity; Zollinger-Ellison Syndrome

Two major forms of gastrin, gastrin-17 (G17) and gastrin-34 (G34), exist in blood. However, conventional immunoassay methods can only quantify total gastrin or G17 alone. Here, we aimed to establish a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantify G17 and G34 simultaneously.. Serum samples were prepared by anion-exchange solid-phase extraction. The analytical performance of the LC-MS/MS method was validated and the method was compared to chemiluminescence immunoassay (CLIA) and radioimmunoassay (RIA). The G17 and G34 concentrations in 245 serum samples from healthy controls, individuals with gastrinoma, and individuals with other diseases were analyzed.. The total runtime of the LC-MS/MS method was 6 min. No substantial matrix effect was observed with internal standard correction. The intraassay coefficients of variation (CVs) for G17 and G34 were 4.0%-14.2% and 4.4%-10.4%, respectively, and total CVs were 5.2%-14.1% and 4.6%-12.4%, respectively. The correlation coefficient between LC-MS/MS and CLIA was 0.87, and between LC-MS/MS and RIA was 0.84. The G17+G34 concentrations for 87.5% of individuals with gastrinoma were higher than the 95th percentile of healthy controls (18.1 pg/mL), whereas the concentrations for individuals with other diseases and gastrinoma overlapped. Based on the Youden indices calculated for G17+G34, G34, and G17, the most specific biomarker was G17 (96.9% clinical specificity at 209.8 pg/mL) for gastrinoma.. This method should aid in the diagnosis of diseases associated with increased gastrin concentrations.

Topics: Chromatography, Liquid; Gastrinoma; Gastrins; Humans; Pancreatic Neoplasms; Tandem Mass Spectrometry

Topics: Adult; Antibodies; Enzyme-Linked Immunosorbent Assay; Female; Gastrin-Secreting Cells; Gastrinoma; Gastrins; Humans; Male; Pancreatic Neoplasms; Radioimmunoassay

Functional gastrin-containing tumor cells were maintained for up to 8 wk without fibroblastoid cell overgrowth. Short-term cultures consisted mainly of colonies composed of small polygonal cells, 70%-90% of which stained positive for immunoreactive gastrin. Cultures exhibited limited growth but viability remained high for 2-3 wk. Culture medium contained component I, and gastrin 34, 17, and 14. With time the major C-terminal gastrin species in medium changed from gastrin 17 at 3 days to gastrin 34 at 5 wk. Extracts of cultured cells contained gastrin 34, 17, and 14; gastrin 17 was the major form detected at all times. Ultrastructurally, cultured tumor cells retained morphological integrity for several weeks; however, with time changes in the appearance of the secretory granules accompanied by evidence of cellular retrodifferentiation were gradually observed. Secretin, gastrin-releasing peptide, 8-bromoadenosine 3':5'-cyclic monophosphate, and phorbol, 12-myristate, 13-acetate stimulated the release of gastrin from cultured cells in a time-dependent fashion. Secretin, bombesin, gastrin-releasing peptide, L-tryptophan, and ethylamine stimulated gastrin release in a dose-dependent fashion. Somatostatin 14 inhibited secretin, bombesin, and gastrin-releasing peptide stimulated gastrin release but did not alter basal release. Cultured cells demonstrated de novo gastrin synthesis, evidenced by their ability to incorporate radiolabeled amino acids into immunoadsorbable gastrinlike material. Primary cultures of gastrin-containing tumor cells free from stromal contamination offer unique advantages for studies of factors that regulate the synthesis and secretion of gastrin and may prove of potential value for studies on cell differentiation and growth.

Topics: Culture Media; Gastrinoma; Gastrins; Humans; Immunoenzyme Techniques; Pancreatic Neoplasms; Protein Precursors; Time Factors; Tumor Cells, Cultured

Tissue pieces of a metastatic human gastrinoma (ultrastructural Type II) were successfully transplanted to the anterior eye-chamber of rats immunosuppressed with Cyclosporin A. Immunocytochemical investigation of the transplants showed evidence for preserved endocrine activity of tumour cells with immunoreactivity towards the C-terminal of the gastrin/cholecystokinin molecule. Studies of gastric acid secretion in tumour-bearing rats and sham-operated controls with chronic gastric fistulas showed that the basal acid output did not differ between the groups during 3 weeks of study. However, the stimulated gastric acid secretion decreased after 5 days in both groups to remain significantly depressed throughout the study, an effect probably due to Cyclosporin A treatment of the groups. The concentration of immunoreactive gastrin in plasma from rats with tumours in oculo was 5 times higher than in sham-operated rats. Gastrin-34 was the major immunoreactive component in both patient serum and rat plasma. An immunoreactive fraction corresponding to component I was found in the patient serum, but not in the rat plasma, although present in the chamber fluid. Components corresponding to gastrin-17 were found both in the patient serum and in the rat plasma. The chromatographic pattern of the tumour was similar to that in rat chamber fluid. The dominating component corresponded to gastrin-17, while gastrin-34 represented the quantitatively smaller component. Gastrin-34 was, however, relatively more abundant in the tumour extract than in the chamber fluid. The study also indicates that a gastrin-producing tumour transplanted in oculo in immunosuppressed rats may increase the rat plasma concentration of the same molecular forms of gastrin as seen in the clinical situation.

Topics: Adolescent; Animals; Anterior Chamber; Chromatography, Gel; Female; Gastric Acid; Gastrinoma; Gastrins; Humans; Immunosuppression Therapy; Male; Microscopy, Electron; Neoplasm Transplantation; Pancreatic Neoplasms; Protein Precursors; Radioimmunoassay; Rats; Rats, Inbred Strains