Identification in rat brain of a 19-kDa protein that comigrates on two-dimensional electrophoresis with p19, a hormonally regulated phosphoprotein of insulinoma cells

We have previously shown that a set of 19-kDa cytosolic proteins, p19, undergoes hormone-dependent phosphorylation in several peptide hormone-producing tumor cells. Here we show, using comigration on two-dimensional electrophoresis with RIN-1122 rat insulinoma cell p19, that an identical set of 19-kDa proteins is present in rat brain but not in liver or skeletal muscle. We have partially purified p19 from rat brain and have compared the apparent isoelectric variants by tryptic peptide mapping. The data suggest that p19 is a novel phosphoprotein consisting of an unphosphorylated form and of three phosphoforms.

Synaptophysin. A new marker for pancreatic neuroendocrine tumors

Synaptophysin (SYP) is a glycoprotein recently isolated from presynaptic vesicles of bovine neurons. Initial studies have demonstrated its presence in neurons in the brain, spinal cord and retina, and in adrenal medullary cells. A subsequent study demonstrated it in pancreatic islet cells and certain neuroendocrine (NE) neoplasms, including several pancreatic islet cell tumors. Based on these preliminary observations, we examined, by immunohistochemistry, conventionally fixed, paraffin sections of 57 pancreatic endocrine tumors with a monoclonal antibody to SYP. Furthermore, we compared the SYP immunoreactivity of 30 of these same tumors with that of neuron-specific enolase (NSE) and of chromogranin (CG). SYP was demonstrated in all but one of the 57 tumors. In the comparative study, for which material was available in only 30 cases, SYP and NSE were present in 29 of the tumors, whereas CG was seen in only 15 cases. We conclude that SYP is a highly sensitive and useful marker for pancreatic NE neoplasms. Moreover, in view of the increasingly evident limited specificity of NSE, SYP should be considered the marker of choice for pancreatic NE neoplasms.

Immunocytochemistry of normal pancreatic islets and spontaneous islet cell tumors in dogs

Immunocytochemical studies of the distribution of glucagon, gastrin, insulin, and somatostatin in normal canine pancreatic islets and 20 canine islet cell tumors were done using the peroxidase-anti-peroxidase (PAP) technique. In the normal adult canine pancreas, islets typically consisted of clusters of 20-30 cells, but smaller foci and even individual cells were identified. Alpha cells (glucagon) were often peripherally located, beta cells (insulin) were centrally located and most numerous, and delta cells (somatostatin) were the least numerous and randomly located. Both juvenile and adult canine pancreases did not stain for gastrin. Of the 20 tumors examined, 18 had positive immunoreactivity for insulin, nine for glucagon, 14 for somatostatin, and one for gastrin. Two tumors were uninterpretable due to autolysis. Three tumors were pure insulinomas, but no pure somatostatinomas, glucagonomas, or gastrinomas were identified. Most tumors and metastases had mixed positive immunoreactivity; one neoplastic cell type predominated with lesser numbers of other cell types. Metastatic sites (liver and lymph node) stained for insulin and somatostatin, only. Foci of non-neoplastic islet cell tissue (nesidioblastosis), often located at the pancreatic-mesenteric junction, stained strongly positive for insulin, glucagon, and somatostatin but not for gastrin. The tumor staining pattern did not consistently correlate with tumor function, as determined by blood glucose and serum insulin assays. The PAP technique works well on paraffin-embedded, formalin-fixed tissue using rabbit or guinea pig antisera as the primary antibody. Staining occurred on sections of paraffin blocks stored for up to 7 years.

Proinsulin radioimmunoassay in the evaluation of insulinomas and familial hyperproinsulinemia

Two new radioimmunoassays for human proinsulin (hPI) have been developed and used to study patients with islet cell tumors and familial hyperproinsulinemia. Both antisera were adsorbed against human C-peptide conjugated to Sepharose, following which cross-reactivity to insulin and C-peptide was less than 0.001%. Antiserum 18D recognized the junction between the insulin B-chain and C-peptide and provided fivefold greater sensitivity than our previously reported hPI assay. Antiserum 11E recognized a determinant which includes or is adjacent to the A-chain-C-peptide junction or which is specified by the tertiary structure. In all 20 patients studied with surgically confirmed islet cell tumors, fasting plasma proinsulinlike material (PLM) was abnormal (greater than 3 SD from the mean measured in either lean or obese subjects) in both assays. This provided better discrimination than has been reported for PLM measured by gel filtration (abnormal in 13 of 14 of the present samples) with a considerably less laborious procedure. Samples from two families in which a mutant proinsulin is present in the circulation have immunoreactivity in the two assays consistent with previous identification of the molecule as an A-chain-C-peptide-linked intermediate of proinsulin conversion. The immunoreactivity of a sample from another family in which large amounts of proinsulin circulate are consistent with an intact molecule being the predominant form. This assay will be useful for confirming the diagnosis of insulin-secreting tumor in patients suspected of recurrent fasting hypoglycemia and in physiologic studies of proinsulin secretion.

The asymptomatic pancreatic islet cell tumor: a novel presentation

Pancreatic islet cell tumors that secrete one or several polypeptide hormones have been suspected and diagnosed secondary to their systemic manifestations. This case report details the diagnosis and treatment of an 62-year-old man with a large pancreatic islet cell tumor without symptoms in whom the mass was found as a direct result of blunt trauma to the abdomen. The tumor contained high concentrations of both vasoactive intestinal polypeptide (VIP) and somatostatin. A discussion of VIP-containing tumors is included.

Immunocytochemical characterization of 10 pancreatic tumours, associated with the glucagonoma syndrome, using antibodies to separate regions of the pro-glucagon molecule and other neuroendocrine markers

Histological diagnosis of neuroendocrine tumours can be hampered by their lack of peptide or amine immunoreactivity. In order to assess the usefulness of a range of specific and general markers of neuroendocrine differentiation, 10 pancreatic endocrine tumours, associated with high levels of circulating glucagon, were studied using histology, histochemistry, immunocytochemistry and electron microscopy. All cases showed immunoreactivity for one or other of the peptides derived from pro-glucagon, although only seven were found to contain immunoreactive pancreatic glucagon. The presence of secretory granules in eight of the tumours was demonstrated by electron microscopy, argyrophilia or chromogranin immunoreactivity. Not only was neuron specific enolase positively immunostained in all the tumours, thereby revealing their neuroendocrine nature, but also the intensity of the immunostain was higher in four of the five malignant ones than in the rest of the cases. Pancreatic polypeptide was present in non-glucagon cells in six out of 10 cases. Our results emphasize the importance of the use, not only of general histochemical and immunocytochemical tests but also antibodies to all possible derivatives of the precursor form of the active tumour product in the diagnosis of possible endocrine tumours. In this way, any abnormal molecular forms of the peptide synthesized by tumour cells with altered synthetic and secretory mechanisms may be detected.

Human chorionic gonadotropin and human placental lactogen in extragonadal tumors. An immunoperoxidase study of ten non-germ cell neoplasms

The immunoperoxidase localization of the alpha and beta subunits of human chorionic gonadotropin (hCG) and of human placental lactogen (hPL) was studied in ten extragonadal nontrophoblastic tumors associated with raised serum levels of one or more of these placental proteins. Three of the tumors were bronchial carcinomas, one was a gastric carcinoma, two were malignant carcinoids (one bronchial and one gastric), two were pancreatic islet cell carcinomas, and two were metastatic carcinomas with an unknown primary site. The maximum alpha subunit serum level was 33,000 ng/ml (gastric carcinoid), the maximum hCG/hCG-beta level was 705,000 ng/ml, and the maximum hPL level was 50 ng/ml (both in the gastric carcinoma). An indirect immunoperoxidase technique and rabbit polyclonal affinity-purified antibodies and peroxidase conjugates were used on formalin-fixed, paraffin-embedded sections. Five blocks (eight cases) or six blocks (two cases) from various sites were obtained from each patient at surgery and/or autopsy. Positive stains for hCG/hCG-beta were seen in six of seven tumors (25/37 blocks) with raised levels, for the alpha subunit in nine of nine tumors (30/47 blocks), and for hPL in two of five tumors (4/26 blocks). Only a relatively minor number of the cells were positive, and within the same case, there was considerable site-to-site variation in the number of positive cells. Large bizarre cells contained hCG/hCG-beta as well as the alpha subunit, if it was demonstrated in the same tumor as the beta subunit. Otherwise, the alpha subunit was found in small unremarkable cells. Giant cells that were smaller than those positive for hCG/hCG-beta contained in hPL. In some serial sections, hCG-alpha, hCG/hCG-beta, and hPL were segregated in different cell populations, supporting the concepts of their separate genetic control.

Pancreatic polypeptide in islet cell tumors. Morphologic and functional correlations

Twelve islet cell tumors and one islet cell hyperplasia were studied with immunocytochemical and radioimmunoassay methods. With immunocytochemical staining, all six insulinomas, one mixed insulinoma-glucagonoma, and four gastrinomas were positive for insulin, insulin and glucagon, and gastrin, respectively. Pancreatic polypeptide (PP) was positive in three insulinomas and one mixed insulinoma-glucagonoma. All of the tumors were positive for neuron-specific enolase (NSE). Radioimmunoassays of tissue extracts further disclosed that all functioning tumors contained more than one pancreatic hormone. PP concentrations of two insulinomas and one mixed insulinoma-glucagonoma were higher than that of normal control pancreases. A study of protein meal-stimulated PP secretion revealed that three of the insulinoma cases and two gastrinoma cases exhibited higher plasma PP levels than the age-matched controls. The findings suggest that: both functioning and nonfunctioning islet cell tumors derive from neuroendocrine cells positive for NSE; all functioning islet cell tumors appear to contain PP in the tumor tissue as a minor component; as many as 70% of the patients with islet cell tumors present with abnormally higher plasma PP levels after protein meals; and a study of meal-stimulated PP secretion may well be used as a marker for the presence of functional islet cell tumors.

Varying expression of cytokeratin and neurofilaments in neuroendocrine tumors of human gastrointestinal tract

Twelve cases of gastrointestinal neuroendocrine tumors, including eight carcinoids and four pancreatic islet cell tumors or their metastases, were immunohistochemically analyzed for the expression of different types of intermediate filament proteins. All of the tumors showed cytokeratin positivity in immunostaining, and the Western blotting technique revealed 45- and 52-kilodalton cytokeratins in carcinoid tumors. Three of the islet cell tumors, but none of the carcinoid tumors, showed, in addition, varying numbers of neurofilament-positive tumor cells when evaluated with rabbit and mouse monoclonal antineurofilament antibodies. The presence of only the 70-kilodalton neurofilament and cytokeratin polypeptides in an islet cell tumor was revealed also by using the Western blotting technique. On the other hand, both fetal and adult pancreatic islet cells showed only cytokeratin positivity. Neurofilament-positive epithelial cells were not found in normal small intestines either. The results show epithelial characteristics in normal gastrointestinal neuroendocrine cells and neuroendocrine tumors by their expression of cytokeratin. In addition, some islet cell tumors display the 70-kilodalton neurofilament protein which suggests the acquisition of a new type of intermediate filament during the neoplastic change.

Pancreatic endocrine tumours associated with WDHA syndrome. An immunohistochemical and electron microscopic study

Nine pancreatic endocrine tumours of patients with watery diarrhoea hypokalaemia achlorhydria (WDHA) syndrome were examined by immunohistochemistry and electron microscopy. All cases revealed neoplastic proliferation of VIP (vasoactive intestinal peptide)-immunoreactive (IR) cells. Immunoreactivity to a novel peptide hormone PHM-27, which is processed from a common big precursor peptide of VIP (prepro VIP/PHM-27), was identified in VIP-IR cells of 8 tumours. VIP-PHM-IR cells had secretory granules measuring about 130 to 220 nm in diameter. Radioimmunoassay of tumour tissue extracts showed high VIP and PHM contents in proportional amounts in most cases. According to the results of immunostaining, the 8 tumours fell into two large groups; 5 with PP (pancreatic polypeptide)-IR cells and 3 with CT (calcitonin)-IR cells. The former group demonstrated VIP cells and PP cells intermingled in various proportions, including one tumour in which coexistence of PP-IR and VIP-IR in the same cells was demonstrated. Cell heterogeneity of the tumours and possible relationships of VIP, PP and CT cells were discussed.

Crystals and alpha-1-antitrypsin-reactive globoid inclusions in an islet cell tumor of the pancreas

An islet cell tumor of the pancreas with unusual light microscopic, ultrastructural, and immunocytochemical features is reported. In addition to secretory granules and positive immunostaining for pancreatic polypeptide, the tumor contained globoid intracytoplasmic inclusions by light and electron microscopy, which correlated with a positive immunoreaction for alpha-1-antitrypsin, and Reinke-like crystals.

Expression of laminin in pancreatic neoplasms and in chronic pancreatitis

The distribution of laminin, a basement membrane glycoprotein, was studied by immunohistological techniques in 10 samples of normal pancreatic tissue, in 15 samples of chronic pancreatitis, and in 33 pancreatic neoplasms. Sections of formalin-fixed, paraffin-embedded specimens were pretreated with pepsin and immunostained for laminin. As judged by the expression of laminin, normal pancreatic glands were surrounded by a continuous, intact basement membrane. In chronic pancreatitis the basement membrane was also mainly continuous, but focally weaker and thinner than around normal glands. In pancreatic adenocarcinomas laminin was irregularly distributed and in large areas totally absent. In anaplastic carcinomas no extracellular laminin was seen, but two cases showed some intracellular laminin in a punctate pattern. The findings suggest that these cancers have defects in the deposition of a basement membrane or that it is degraded. Our data suggest that the integrity of the basement membrane correlates with the degree of malignancy in ductal adenocarcinomas, but this is not the case for mucinous cystic neoplasms or for islet cell tumors. In these neoplasms a nearly intact basement membrane was seen both in malignant tumors and in their benign counterparts.

Binding of antibodies against human prealbumin to intestinal and bronchial carcinoids and to pancreatic endocrine tumours

Antibodies against human prealbumin (HPA) give a strong immunoperoxidase staining of the A (glucagon) pancreatic cells and of glucagon-, insulin- and gastrin-producing pancreatic tumours. The majority of intestinal and bronchial carcinoids are also reactive. The staining may be related to presence in the C-terminal sequence of HPA of determinants in common with polypeptide (pro-) hormones.

Pancreatic somatostatinoma: abundance of somatostatin-28(1-12)-like immunoreactivity in tumor and plasma

In the present study we characterized and compared the relative amounts of the different molecular forms of somatostatin-14 like immunoreactivity (S-14 LI) and of somatostatin-28(1-12) like immunoreactivity (S-28(1-12) LI) in extracts of tumor and peripheral plasma of a patient with a pancreatic somatostatinoma. Tissue and plasma were chromatographed on Sephadex G-50 columns equilibrated with 6 M urea. Immunoreactivity in the eluting fractions was assayed with two separate, region specific RIAs using antibodies R149 (S-14 LI) and S309 (S-28(1-12)LI). RIA R149 recognizes the 6-8 and 14 regions of the S-14 sequence and detects S-14, S-28, and prosomatostatin, an approximately 14,000 mol wt precursor for the two peptides. RIA S309 recognizes the 2-11 segment of S-28 and reacts with S-28, S-28(1-12), and higher mol wt S-28(1-12) LI but not S-14. Total tumor S-14 LI was 190 pmol/mg protein and consisted of three peaks of immunoreactivity of apparent 14,000 mol wt (14K S-14 LI), 3,200 mol wt (3.2K corresponding to S-28) and 1,600 mol wt (1.6K corresponding to S-14). The three peaks comprised, respectively, 7%, 57%, and 36% of total S-14 LI. Total tumor S-28(1-12) LI was 594 pmol/mg protein and eluted as four major peaks of immunoreactivity as follows: peak I (mol wt 15,000, 10% of total S-28(1-12) LI); peak II (mol wt 8,000, 20% of S-28(1-12) LI), peak III (corresponding to S-28, 19% of S-28(1-12) LI); peak IV (corresponding to S-28(1-12), approximately 50% of total S-28(1-12) LI). Total plasma concentration of S-14 LI was 714 pM, being made up of the three peaks found in tumor but in the following relative amounts (14K S-14 LI, 22%; 3.2K, 29%; 1.6 K, 49%). Plasma S-28(1-12) LI was 4 times higher (2879 pM) than S-14 LI and contained immunoreactivity corresponding to each of the four peaks found in the tumor.

CONCLUSIONS

1) The tumor and plasma concentrations of S-28(1-12) LI were greater than that of S-14 LI. 2) Both tumor and plasma S-14 LI and S-28 LI were heterogeneous and comprised species corresponding not only to S-14 but also S-28, S-28(1-12), prosomatostatin, and other higher mol wt forms of S-28.(ABSTRACT TRUNCATED AT 400 WORDS)

Alpha-1-antitrypsin in islet cell tumors of the pancreas

The presence of alpha-1-antitrypsin (A1AT) in normal pancreatic islets recently has been demonstrated, and serum elevation of A1AT in patients having pancreatic tumors has been reported. In the present study, the presence of A1AT in 12 of 33 islet cell tumors was demonstrated. The possible utility of A1AT as a marker for islet cell tumors is suggested.

Human growth hormone releasing factor and somatostatin from two pancreatic tumors: isolation and characterization

Peptides with high intrinsic activity to release growth hormone from pituitary cells in tissue cultures were isolated from two different human pancreatic tumors that had caused acromegaly. Homogeneous peptides were obtained after gel filtration and two steps of reverse-phase high-performance liquid chromatography. From one tumor a 44-residue peptide (human pancreas growth hormone releasing factor, hpGRF-44) was isolated, together with two shorter fragments of reduced bioactivity having 40 and 37 amino acid residues (hpGRF-40, hpGRF-37). In contrast, the other tumor contained only one form of GRF which proved to be identical to hpGRF-40. These hpGRFs are indistinguishable from partially purified preparations of hypothalamic growth hormone releasing factor of human, porcine and murine origins with respect to biological activity and are very similar in their physicochemical properties (molecular weight, retention behavior on reverse-phase HPLC, absence of sulfhydryl groups). One of the pancreatic tumors also contained two forms of immunoreactive somatostatin. One form, after isolation and partial microsequencing, was identified as somatostatin-14 with a structure identical to that of the peptide found in other species. The second form has tentatively been identified as somatostatin-28 on the basis of chromatographic behavior.

Primary structures of three human pancreas peptides with growth hormone-releasing activity

The primary structures of three polypeptides, possessing high intrinsic growth hormone-releasing activity and derived from a human pancreatic carcinoma which had caused acromegaly, were established by sequence analyses of the intact peptides and their cyanogen bromide digestion fragments with a gas-phase sequenator. The three human pancreas growth hormone-releasing factors contain 44 (hpGRF-44), 40 (hpGRF-40), and 37 (hpGRF-37) amino acids in identical sequences from their NH2 termini. High pressure liquid chromatography of the native peptides and their synthetic replicates showed that hpGRF-37 and hpGRF-40 possess free carboxyl termini while that of hpGRF-44 is amidated. The structure of hpGRF-44 was established as: Tyr-Ala-Asp-Ala-Ile-Phe-Thr-Asn-Ser-Tyr-Arg-Lys-Val-Leu-Gly-Gln-Leu-Ser-Ala Arg-Lys-Leu-Leu-Gln-Asp-Ile-Met-Ser-Arg-Gln-Gln-Gly-Glu-Ser-Asn-Gln-Glu-Arg-Gly Ala-Arg-Ala-Arg-Leu-NH2.