Islet amyloid polypeptide (IAPP) in patients with neuroendocrine tumours

Human RAD51 Protein Forms Amyloid-like Aggregates In Vitro

RAD51 is a central protein of homologous recombination and DNA repair processes that maintains genome stability and ensures the accurate repair of double-stranded breaks (DSBs). In this work, we assessed amyloid properties of RAD51 in vitro and in the bacterial curli-dependent amyloid generator (C-DAG) system. Resistance to ionic detergents, staining with amyloid-specific dyes, polarized microscopy, transmission electron microscopy (TEM), X-ray diffraction and other methods were used to evaluate the properties and structure of RAD51 aggregates. The purified human RAD51 protein formed detergent-resistant aggregates in vitro that had an unbranched cross-β fibrillar structure, which is typical for amyloids, and were stained with amyloid-specific dyes. Congo-red-stained RAD51 aggregates demonstrated birefringence under polarized light. RAD51 fibrils produced sharp circular X-ray reflections at 4.7 Å and 10 Å, demonstrating that they had a cross-β structure. Cytoplasmic aggregates of RAD51 were observed in cell cultures overexpressing RAD51. We demonstrated that a key protein that maintains genome stability, RAD51, has amyloid properties in vitro and in the C-DAG system and discussed the possible biological relevance of this observation.

Downregulated Pancreatic Beta Cell Genes Indicate Poor Prognosis in Patients With Pancreatic Neuroendocrine Neoplasms

OBJECTIVE

To predict metachronous liver metastasis after pancreatectomy for pancreatic neuroendocrine neoplasms (Pan-NENs).

SUMMARY OF BACKGROUND DATA

Liver metastasis determines the prognosis of patients with Pan-NENs, but no index exists in the WHO 2017 classification for this prediction.

METHODS

Between April 2014 and March 2018, resected primary tumors from 20 patients with or without simultaneous liver metastasis were examined using genome-wide gene expression analysis. For validation analysis, resected primary tumors from 62 patients without simultaneous liver metastasis were examined for PAX6 expression.

RESULTS

Gene expression profiling revealed pancreatic beta cell genes (NES, -2.0; P < 0.001) as the most downregulated set in patients with simultaneous liver metastasis. In the test study, PAX6 was the most valuable index for liver metastasis (log FC, -3.683; P = 0.0096). Multivariate analysis identified PAX6 expression (hazard ratio, 0.2; P = 0.03) as an independent risk factor for metachronous liver metastasis-free survival (mLM-FS). The 5-year mLM-FS of patients with high versus low PAX6 expression was significantly better (95% vs 66%, respectively; P < 0.0001). The 5-year overall survival rate of was also better than in those with high versus low PAX6 expression (100% vs 87%, respectively). Patients with low PAX 6 expression were significantly younger and leaner, had a higher Ki-67 index (P = 0.01, 0.007, 0.008, respectively), and showed a higher mitotic rate than patients with high PAX6 expression.

CONCLUSIONS

Downregulated pancreatic beta cell genes involving PAX6 in primary tumors may predict mLM and poor overall survival after primary tumor resection in Pan-NEN patients.

In-vitro and in-vivo antagonistic action of an anti-amylin Spiegelmer

The anorectic and dipsogenic effects of the pancreatic hormone amylin are mediated by the area postrema and the subfornical organ. We tested the effectiveness of a new amylin antagonist, a so-called RNA Spiegelmer, by electrophysiological in-vitro recordings from the rat subfornical organ and by immunohistological c-Fos studies in the area postrema. Amylin's excitatory effect on subfornical organ neurons was blocked by the anti-amylin Spiegelmer. Peripheral administration 5 h prior to amylin also suppressed the amylin-induced activation (c-Fos expression) in the area postrema. The biostable anti-amylin Spiegelmer may be therapeutically beneficial in conditions associated with high plasma amylin levels, such as cancer anorexia occurring during certain pancreatic tumors.

Pancreatic signals controlling food intake; insulin, glucagon and amylin

The control of food intake and body weight by the brain relies upon the detection and integration of signals reflecting energy stores and fluxes, and their interaction with many different inputs related to food palatability and gastrointestinal handling as well as social, emotional, circadian, habitual and other situational factors. This review focuses upon the role of hormones secreted by the endocrine pancreas: hormones, which individually and collectively influence food intake, with an emphasis upon insulin, glucagon and amylin. Insulin and amylin are co-secreted by B-cells and provide a signal that reflects both circulating energy in the form of glucose and stored energy in the form of visceral adipose tissue. Insulin acts directly at the liver to suppress the synthesis and secretion of glucose, and some plasma insulin is transported into the brain and especially the mediobasal hypothalamus where it elicits a net catabolic response, particularly reduced food intake and loss of body weight. Amylin reduces meal size by stimulating neurons in the hindbrain, and there is evidence that amylin additionally functions as an adiposity signal controlling body weight as well as meal size. Glucagon is secreted from A-cells and increases glucose secretion from the liver. Glucagon acts in the liver to reduce meal size, the signal being relayed to the brain via the vagus nerves. To summarize, hormones of the endocrine pancreas are collectively at the crossroads of many aspects of energy homeostasis. Glucagon and amylin act in the short term to reduce meal size, and insulin sensitizes the brain to short-term meal-generated satiety signals; and insulin and perhaps amylin as well act over longer intervals to modulate the amount of fat maintained and defended by the brain. Hormones of the endocrine pancreas interact with receptors at many points along the gut-brain axis, from the liver to the sensory vagus nerve to the hindbrain to the hypothalamus; and their signals are conveyed both neurally and humorally. Finally, their actions include gastrointestinal and metabolic as well as behavioural effects.

Head and neck amyloidosis: a clinicopathologic study of 15 cases

Amyloidosis refers to the idiopathic, extracellular deposition of fibrillar proteins, termed amyloid, in tissues. Although amyloidosis is a rare disease, the head and neck region has been reported as a frequent site of amyloid deposits, accounting for approximately 19% of reported amyloid cases in one review. Fifteen cases of head and neck amyloid, excluding the brain, with clinical follow-up were identified in the Surgical Pathology files from 1985 to 2005 at Emory University Hospital. The histopathology, histochemistry, and patient follow-up were reviewed. Nine men and six women with an age range of 18-76 years (mean 55.7 years) were identified. The initial clinical presentation was dependent on the site of amyloid deposits. The clinical types of amyloidosis included localized amyloid deposits in the larynx and tongue, plasma cell dyscrasia associated AL amyloidosis, and hemodialysis-associated amyloidosis. Secondary amyloidosis developed in one patient with carcinoid tumor.

Tissue Expression and Secretion of Amylin

Amylin and insulin are co-localized within the same secretory granules of pancreatic beta-cells. Acutely, the secreted ratio of amylin:insulin is comparatively invariant, but long-standing hyperglycemia may favor induction of amylin synthesis and secretion over that of insulin. Amylin is also found in much lesser quantities in the gut and other tissues. In humans, both type 1 diabetes mellitus and the later stages of type 2 diabetes mellitus are characterized by deficiency of both insulin and amylin secretion. The severity of amylin deficiency appears to correlate with the severity of insulin deficiency. This concordance of deficiencies in amylin and insulin secretion observed with the progression of diabetes mellitus is consistent with their co-localization in pancreatic beta-cells. Amylin is cleared mainly by proteolytic degradation at the kidney. The terminal t1/2 for rat amylin in rats is approximately 13 min, and that for pramlintide in humans is approximately 20-45 min.

Amylin in pancreatic islets and pancreatic endocrine neoplasms

Amylin is a chief constituent of the amyloid present in insulinomas, and is colocalized in beta islet cells. By immunocytochemical staining, all four islet cells including insulin, glucagon, somatostatin (SRIF) and pancreatic polypeptide (PP) cells were positively stained for amylin. The strongly insulin-positive cells corresponded with the strongly amylin-positive cells, and glucagon cells appeared to be strongly positive for amylin, whereas SRIF and PP cells were weakly positive for amylin. Among 37 cases of pancreatic endocrine neoplasms, insulinomas were more stronger stained for amylin than other islet cell tumors; however, amylin staining was the same or weaker than insulin staining. Glucagonomas and PP-omas were weakly positive for amylin, whereas six of 11 gastrinomas were weakly positive for amylin. It is concluded that three orthoendocrine tumors including insulinomas, glucagonomas and PP-omas were all positive for amylin, whereas ectopic hormone secreting gastrinomas were positive for amylin in six of 11 cases (55%). This colocalization of amylin with insulin, glucagon and PP may support a structure-function relationship of amylin and pancreatic hormones. The lesser immunoreactive amylin in pancreatic endocrine neoplasms than in normal islet cells may contribute to autonomous hypersecretion of hormones by pancreatic endocrine neoplasms.

RNA interference of achaete-scute homolog 1 in mouse prostate neuroendocrine cells reveals its gene targets and DNA binding sites

We have previously characterized a transgenic mouse model (CR2-TAg) of metastatic prostate cancer arising in the neuroendocrine (NE) cell lineage. Biomarkers of NE differentiation in this model are expressed in conventional adenocarcinoma of the prostate with NE features. To further characterize the pathways that control NE proliferation, differentiation, and survival, we established prostate NE cancer (PNEC) cell lines from CR2-TAg prostate tumors and metastases. GeneChip analyses of cell lines harvested at different passages, and as xenografted tumors, indicated that PNECs express consistent features ex vivo and in vivo and share a remarkable degree of similarity with primary CR2-TAg prostate NE tumors. PNECs express mAsh1, a basic helix-loop-helix (bHLH) transcription factor essential for NE cell differentiation in other tissues. RNA interference knockdown of mAsh1, GeneChip comparisons of treated and control cell populations, and a computational analysis of down-regulated genes identified 12 transcriptional motifs enriched in the gene set. Affected genes, including Adcy9, Hes6, Iapp1, Ndrg4, c-Myb, and Mesdc2, are enriched for a palindromic E-box motif, CAGCTG, indicating that it is a physiologically relevant mAsh1 binding site. The enrichment of a c-Myb binding site and the finding that c-Myb is down-regulated by mAsh1 RNA interference suggest that mAsh1 and c-Myb are in the same signaling pathway. Our data indicate that mAsh1 negatively regulates the cell cycle (e.g., via enhanced Cdkn2d, Bub1 expression), promotes differentiation (e.g., through effects on cAMP), and enhances survival by inhibiting apoptosis. PNEC cell lines should be generally useful for genetic and/or pharmacologic studies of the regulation of NE cell proliferation, differentiation, and tumorigenesis.

Extended life span is associated with insulin resistance in a transgenic mouse model of insulinoma secreting human islet amyloid polypeptide

Pancreatic amyloid is found in patients with insulinomas and type 2 diabetes. To study mechanisms of islet amyloidogenesis, we produced transgenic mice expressing the unique component of human islet amyloid, human islet amyloid polypeptide (hIAPP). These mice develop islet amyloid after 12 mo of high-fat feeding. To determine whether we could accelerate the rate of islet amyloid formation, we crossbred our hIAPP transgenic animals with RIP-Tag mice that develop islet tumors and die at 12 wk of age from hypoglycemia. At 12 wk of age, this new line of hIAPPxRIP-Tag mice was heavier (29.7 +/- 1.0 vs. 25.0 +/- 1.3 g, P < 0.05) and had increased plasma glucose levels (4.6 +/- 0.4 vs. 2.9 +/- 0.6 mmol/l, P < 0.05) compared with littermate RIP-Tag mice. However, the hIAPPxRIP-Tag mice did not display islet amyloid or amyloid fibrils despite high circulating hIAPP levels (24.6 +/- 7.0 pmol/l). Interestingly, hIAPPxRIP-Tag mice had a longer life span than RIP-Tag mice (121 +/- 8 vs. 102 +/- 5 days, P < 0.05). This increase in life span in hIAPPxRIP-Tag was positively correlated with body weight (r = 0.48, P < 0.05) and was associated with decreased insulin sensitivity compared with RIP-Tag mice. hIAPPxRIP-Tag mice did not develop amyloid during their 4-mo life span, suggesting that increased hIAPP secretion is insufficient for islet amyloid formation within such a short time. However, hIAPPxRIP-Tag mice did have an increase in life span that was associated with insulin resistance, suggesting that hIAPP has extrapancreatic effects, possibly on peripheral glucose metabolism.

Expression of p68 protein kinase and its prognostic significance during IFN-alpha therapy in patients with carcinoid tumours

The aim of this study was to evaluate the antiproliferative effects of interferon alpha (IFN-alpha) on neuroendocrine differentiated cell lines and, retrospectively, to assess the prognostic significance of p68 protein kinase (PKR) induction in neuroendocrine gut and pancreatic tumour patients. Archive specimens from 56 patients were studied, 43 before IFN-alpha and 56 during therapy. The tissues were immunostained for p68 protein kinase (PKR) using the monoclonal antibody (MAb) TJ4C4. A significant increase in immunostaining after treatment with IFN-alpha compared with before treatment (3.47 +/- 0.12 versus 2.72 +/- 0.15, P < 0.001) was noted. The p68 score was significantly increased after treatment only in patients with stable disease before = 2.71 +/- 0.19, after = 3.40 +/- 0.14 (P < 0.001) or an objective response before 3.13 +/- 0.22, after = 4.00 +/- 0.24 (P < 0.05) but not in those with progressive disease (before = 2.32 +/- 0.24, after 2.86 +/- 0.26, NS). A low p68 score (< 3.0) during treatment was a predictor of shorter duration of response and overall survival (P = 0.0062 and P < 0.0001, respectively). Furthermore, IFN-alpha showed a significant antiproliferative effect (by [3H]thymidine incorporation) on two carcinoid tumour cell lines in a dose-dependent manner which correlated with a dose-dependent induction of p68 mRNA and protein expression (by Northern and Western blot analysis). We conclude that IFN-alpha can effectively inhibit the in vitro growth of carcinoid tumor cell lines and upregulates the expression of p68 at both mRNA and protein levels in carcinoid tumours. The induction of p68 could be a prognostic indicator of response in patients with carcinoid tumours during IFN-alpha treatment.

Carcinoid tumors of the lung: immuno- and ligandohistochemistry, analysis of integrated optical density, syntactic structure analysis, clinical data, and prognosis of patients treated surgically

BACKGROUND

Analysis of potentially prognostic relevant factors of carcinoid tumors of the lung.

METHODS

Clinical features, tumor size, and features derived from immuno- and ligandohistochemistry, cytometry and histometry, and survival have been analyzed in 82 potentially curatively resected carcinoid tumors of the lung.

RESULTS

Patients with typical carcinoid tumors had a longer history of symptoms (13 vs. 8 months), fewer smoked (30% vs. 80%), and developed less frequently lymph node metastases (20% vs. 65%) compared to patients with atypical carcinoids. Statistically significant differences between both cell types have been observed in cytometric and histometric features, and binding of Lewis A trisaccharide (Lea). Prognosis is associated with the cell type, presence of lymph node metastases and heparin-binding lectin (HBL), certain cytometric and structural features, and binding of macrophage migration inhibitory factor (MIF) and beta-N-acetyl-D-galactosamine (beta-GalNAc).

CONCLUSIONS

Complete lymph node dissection is necessary, data of cytometry, histometry, and ligandohistochemistry might eventually predict the course of the disease.

Attenuation of the anorectic effects of glucagon, cholecystokinin, and bombesin by the amylin receptor antagonist CGRP(8-37)

The anorectic effect of IP injection of amylin (1 microgram/kg) was abolished by simultaneous IP injection of the amylin receptor antagonist calcitonin gene-related peptide-(8-37) [CGRP(8-37), 10 micrograms/kg]. The IP injection of pancreatic glucagon (400 micrograms/kg) at dark onset also reduced food intake in 24-h food-deprived rats, and this effect was also totally blocked by coadministration of CGRP(8-37) (10 micrograms/kg). In another feeding paradigm with glucagon (540 micrograms/kg IP 3 h into the light phase in 3 h-prefed rats), however, the anorectic effect of glucagon was not significantly antagonized by CGRP(8-37). The anorectic effect of cholecystokinin (CCK) (0.25 microgram/kg) and bombesin (BBS) (2 micrograms/kg) was partly neutralized by CGRP(8-37). In contrast, the anorectic effect of vasopressin (VP) (2.5 micrograms/kg) was not influenced by CGRP(8-37). As glucagon has been shown previously to increase the secretion of amylin, we conclude that the anorectic effect of peripherally administered glucagon is mediated by the release of amylin, at least under certain conditions. This may also be true for CCK and BBS, as these peptides are insulinotropic and may therefore be presumed to increase amylin release.