Presence of nerve growth factor-like immunoreactivity in carcinoid tumour cells and induction of a neuronal phenotype in long-term culture

Co-expression of intermediate filaments glial fibrillary acidic protein and cytokeratin in pituitary adenoma

PURPOSE

To analyze the co-expression of the intermediate filaments GFAP and cytokeratin in 326 pituitary adenomas with regard to the distribution pattern, the subtype of the adenoma and clinical prognostic data.

METHODS

Tissue from 326 pituitary adenomas and 13 normal anterior pituitaries collected in the Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, between 2006 and 2009 was investigated by immunohistochemistry, immunofluorescence and electron microscopy.

RESULTS

Co-expression of intermediate filaments GFAP and cytokeratin was associated with hormone expression in 62/278 cases (22%), but only found in 2/48 (4%) of null cell adenomas (p < 0.01). Simultaneous co-expression of GFAP and cytokeratin in the same cells was demonstrated in 26 out of 326 pituitary adenomas and in all 13 pituitaries. In pituitary intermediate filaments were demonstrated in a larger area of the cytoplasm than in adenoma (p < 0.01), however, overlapping expression was seen in 2.6% of the total area in both, pituitary and adenoma. Congenially, cells with overlapping expression were found near vessels and in follicles. Furthermore, adenomas with cellular co-expression of GFAP and cytokeratin were associated with a lower recurrence rate (7.7%) compared to adenomas without co-expression of intermediate filaments (17.8%).

CONCLUSIONS

Cellular co-expression of the intermediate filaments GFAP and cytokeratin in pituitary adenomas and the pituitary was demonstrated and shown to be associated with hormone expression and low recurrence rate. The results are discussed with regard to the biology of folliculostellate cells, neural transformation and tumor stem cells. This study may complement the understanding of pituitary adenoma biology.

Combined gangliocytoma and prolactinoma of the pituitary gland

Gangliocytomas of the pituitary gland are rare lesions that often occur in combination with pituitary adenomas, which are frequently associated with the hypersecretion of pituitary hormones, particularly growth hormones. We report a case of combined gangliocytoma and prolactinoma of the pituitary gland. A 49-year-old male presented with vertigo. Radiological examination revealed an intrasellar tumor with a suprasellar extension, which was removed via the trans-sphenoidal approach. Histologically, the tumor was composed of adenoma cells, mature ganglion cells and cells with features intermediate between those of adenoma cells and ganglion cells (intermediate cells). Immunohistochemical analysis revealed the ganglion cells and intermediate cells as well as adenoma cells to be positive for prolactin. No growth hormone-positive tumor cells were observed. The ganglion cells were positive for synaptophysin and neurofilament. The findings in this case are discussed in relation to hypotheses proposed for histogenesis, and the presence of intermediate cells supports three hypotheses. The first is that adenoma cells transform into ganglion cells, and the second is that both components originate from the embryonal pituitary cell rests, showing intermediate features between ganglion cells and adenoma cells. The last is that their common origin may be the same stem/progenitor cells in normal adult pituitaries.

Ganglion cell containing pituitary adenomas: signs of neuronal differentiation in adenoma cells

Ganglion cell containing pituitary adenomas are rare. They represent tumors originating in the sella turcica which are composed of adenomatous and neuronal components. Recently accumulated information suggests a common origin for their neuronal and pituitary constituents. The objective of this study was to report the clinical and morphologic findings of pituitary gangliocytomas and study their immunoprofile using neuronal markers. Seven cases of pituitary gangliocytomas retrieved from 1,322 sellar lesions were studied. All tumors were removed from patients with mild acromegaly. Histologically they were biphasic composed of pituitary adenoma and clusters of ganglion cells embedded in a variably dense neuropil substrate. All adenomas belonged to the category of sparsely granulated somatotroph adenoma and were positive for growth hormone, whereas in five tumors, a few adenoma cells were also positive for prolactin. Ganglion cells were immunoreactive for NSE, synaptophysin and neurofilament protein (NFP). NFP-reactive fibrils were observed in the neuropil substrate and varied in number among the cases. Interestingly, all tumors contained varying numbers of adenoma cells with NFP-positive, dot-like areas of cytoplasmic reactivity, mostly tiny paranuclear, a finding not previously reported in human pituitary gangliocytomas. The presence of NFP in pituitary adenomas indicates neuronal differentiation in adenoma cells, suggesting a common origin for neuronal and pituitary adenoma cell elements in gangliocytomas.

Neurotrophin system expression in human pulmonary carcinoid tumors

Neurotrophin (NT) and NT receptor expression was assessed in 12 typical (TC) and 8 atypical (AC) human pulmonary carcinoids by Western blot and immunohistochemistry. TC and AC carcinoid express to different extent NT and NT receptor proteins. Nerve growth factor (NGF) was expressed by 83% of the TC but not by the AC carcinoids. Brain derived neurotrophic factor (BDNF) was expressed by 33 and 100% of TC and AC carcinoids, respectively. NT-3 was expressed by 58% of the TC and 38% of AC carcinoids. TC carcinoids express high affinity NT receptors while 50% of the AC carcinoids express the TrkB receptor. Our results demonstrate that NGF/TrkA and BDNF/TrkB signaling need to be considered as regulatory pathways that may address survival, differentiation and/or aggressiveness of human pulmonary carcinoids. Contrarily to the BDNF/TrkB, expression of the NGF/TrkA signaling may overcome aggressiveness of carcinoid cells. NTs may be useful as markers in the clinic.

A transplantable human carcinoid as model for somatostatin receptor-mediated and amine transporter-mediated radionuclide uptake

A human midgut carcinoid tumor was successfully transplanted into nude mice and propagated for five consecutive generations (30 months) with well-preserved phenotype. Tumor cells in nude mice expressed identical neuroendocrine markers as the original tumor, including somatostatin receptors (somatostatin receptors 1 to 5) and vesicular monoamine transporters (VMAT1 and VMAT2). Because of the expression of somatostatin receptors and VMAT1 and VMAT2 the grafted tumors could be visualized scintigraphically using the somatostatin analogue 111In-octreotide and the catecholamine analogue 123I-metaiodobenzylguanidine. The biokinetics of the somatostatin analogue 111In-octreotide in the tumors was studied and showed a high retention 7 days after administration. Cell cultures were re-established from transplanted tumors. Immunocytochemical and ultrastructural studies confirmed the neuroendocrine differentiation. The human origin of transplanted tumor cells was confirmed by cytogenetic and fluorescence it situ hybridization analyses. Spontaneous secretion of serotonin and its metabolite, 5-hydroxyindole acetic acid, from tumor cells was demonstrated. The tumor cells increased their [Ca2+]i in response to beta-adrenoceptor stimulation (isoproterenol) and K+-depolarization. All somatostatin receptor subtypes could be demonstrated in cultured cells. This human transplantable carcinoid tumor, designated GOT1, grafted to nude mice, will give unique possibilities for studies of somatostatin receptor- and VMAT-mediated radionuclide uptake as well as for studies of secretory mechanisms.

Pituitary adenoma with neuronal choristoma: a report of two rare cases

Two rare cases of pituitary adenoma with neuronal choristoma are described. Both patients were female and presented with features of acromegaly with elevated growth hormone and prolactin levels. Radiologically, both lesions were predominantly intrasellar in location with extension into suprasellar region, but hypothalamus was not involved. Histopathological examination revealed a mixture of chromophobe pituitary adenoma cells and neuronal cells. In both cases, the adenoma component was positive for growth hormone and prolactin. Interestingly, immunopositivity for alpha-subunit, cytokeratin and prolactin was seen in the adenoma and neuronal cells in one case. Our findings support the hypothesis that the neuronal cells possibly arise from adenoma cells as a result of metaplasia.

Prolactin-producing pituitary adenoma and carcinoma with neuronal components--a metaplastic lesion

Recent studies indicate that cells of various epithelial tumors are capable of transformation to neurons. Observing both neurons and neuropil in two prolactin-producing adenohypophyseal tumors, one benign and one malignant, we sought to assess their cellular differentiation, the presence of nerve growth factor receptor, and expression of the dopamine receptor gene using immunocytochemistry, electron microscopy, and in situ hybridization. Light and electron microscopy clearly revealed cells morphologically transitional between adenoma/carcinoma cells and neurons. Large neurons lacked proliferative activity. Neurons in varying number showed immunoreactivity for pituitary hormones including prolactin, growth hormone and alpha subunit in the adenoma and prolactin alone in the carcinoma. The distribution of nerve growth factor receptor staining was similar. In both tumors, in situ hybridization showed mRNAs for prolactin and dopamine receptor within adenohypophyseal cells and neurons. Our results indicate that the occurrence of neurons and neuropil in growth hormone and prolactin-producing pituitary tumors appears to be the result of metaplasia. The process is not limited to benign tumors and may be due to the production of tropic substances by the adenohypophysial cells, which by paracrine/autocrine mechanisms result in transformation of adenoma cells to nerve cells.

Tachykinins in the gut. Part II. Roles in neural excitation, secretion and inflammation

The preprotachykinin-A gene-derived peptides substance (substance P; SP) and neurokinin (NK) A are expressed in intrinsic enteric neurons, which supply all layers of the gut, and extrinsic primary afferent nerve fibers, which innervate primarily the arterial vascular system. The actions of tachykinins on the digestive effector systems are mediated by three different types of tachykinin receptor, termed NK1, NK2 and NK3 receptors. Within the enteric nervous system, SP and NKA are likely to mediate, or comediate, slow synaptic transmission and to modulate neuronal excitability via stimulation of NK3 and NK1 receptors. In the intestinal mucosa, tachykinins cause net secretion of fluid and electrolytes, and it appears as if SP and NKA play a messenger role in intramural secretory reflex pathways. Secretory processes in the salivary glands and pancreas are likewise influenced by tachykinins. The gastrointestinal arterial system may be dilated or constricted by tachykinins, whereas constriction and an increase in the vascular permeability are the only effects seen in the venous system. Various gastrointestinal disorders are associated with distinct changes in the tachykinin system, and there is increasing evidence that tachykinins participate in the hypersecretory, vascular and immunological disturbances associated with infection and inflammatory bowel disease. In a therapeutic perspective, it would seem conceivable that tachykinin antagonists could be exploited as antidiarrheal, antiinflammatory and antinociceptive drugs.

Neuroendocrine insights from the laboratory to the clinic

BACKGROUND

The interaction between adrenergic nerves and enterochromaffin (EC) cells was studied in health and disease using animal models and patients with the midgut carcinoid syndrome.

METHODS

The methods included morphological techniques (fluorescence microscopy/cytofluorimetry, electronmicroscopy), experimental models (in vivo/in vitro nerve stimulation, pharmacological analyses, axonal transport, tumor transplantation, tumor cell cultures) and clinical tests (pentagastrin provocation, octreotide scintigraphy).

RESULTS

From vagal nerve stimulation studies it was clear that activation of adrenergic fibers could release serotonin (5-HT) from EC cells, which led to the mapping of a vagal adrenergic pathway. Ultrastructurally a direct innervation of EC cells was demonstrated. It was confirmed in vitro that adrenoceptors controlled the release of 5-HT; it was maintained in neoplasia as studied in the tumor models. The tumor cells shared several functional and morphological characteristics with adrenergic neurons and exerted trophic actions on neurons grown in co-culture.

CONCLUSIONS

Pentagastrin provocation of 5-HT release in carcinoid patients may be mediated via release of catecholamines from the adrenals in turn activating adrenoceptors on tumor cells. Pretreatment with a somatostatin analog can reduce these reactions and thus minimize the risk for carcinoid crisis during surgery.

Pituitary adenoma with neuronal choristoma (PANCH): composite lesion or lineage infidelity?

Fifteen cases of the rare association of pituitary adenoma and neuronal choristoma (PANCH) were investigated by histology, immunohistochemistry, and electron microscopy. Acromegaly was apparent clinically in 11 patients and was equivocal in 1, and 3 lesions appeared to be nonfunctioning. Histology revealed various proportions of chromophobic PA and nervous tissue consisting of neuronlike cells and neuropil. Immunohistochemistry documented growth hormone (GH) in every PA, including those unassociated with clinical acromegaly. In contrast, the NCH component showed no consistent immunohistochemical profile. Most frequent reactivities were for the pituitary hormone alpha subunit, thyroid-stimulating hormone, and GH, whereas only a few cases displayed scattered positivity for GH-releasing hormone. Low-molecular weight keratin tested positive in PAs and in a few cells and processes of an NCH. A few fibrous bodies were immunoreactive for neurofilament protein. Electron microscopy revealed sparsely granulated GH cell adenoma, neurons, and neuropil. Cells intermediate between PA and neurons were numerous in 1 lesion. The present morphologic findings as well as lack of GH cell hyperplasia and the consistent association of NCH with but one type of PA do not support the causative role of NCH in the initiation of PA, as proposed previously. It appears that NCH is the result of neuronal differentiation within sparsely granulated GH cell adenomas.

Growth factors and carcinoid tumours

The presence of growth factors and their receptors in human midgut carcinoids and in gastric carcinoids of Mastomys have been investigated. Human midgut carcinoid tumours produce IGF-I as demonstrated by immunocytochemistry and radioimmunoassay. IGF-I receptors were detectable in half of the tumours and stimulation of cultured tumour cells with IGF-I enhanced DNA synthesis. IGF-I may therefore act as an autocrine stimulator of carcinoid tumour growth. Expression of TGF-alpha and EGF-receptors could also be demonstrated in midgut carcinoids by immunocytochemistry and Northern analysis, suggesting that TGF-alpha participates in the autocrine modulation of carcinoid growth. Co-culture of human midgut carcinoid tumours and rat fetal cholinergic neurons demonstrated secretion of a potent neuronotrophic factor by cultured tumour cells. IGF-I and TGF-alpha may account for these neuronotrophic effects, but carcinoid tumours may also secrete an as yet unidentified growth factor. Gastric (ECL cell) carcinoids developed rapidly in Mastomys during hypergastrinemia due to histamine2-receptor blockade, suggesting that gastrin is an essential growth factor for these carcinoids.

The effect of somatostatin analogue SMS 201-995 on serotonin levels in the medium of primary carcinoid cell cultures

Carcinoid cell cultures were established from primary tumours and liver and mesenteric metastases. The cells continued to produce serotonin for up to 6 months. Cells from different tumours showed different properties. In most wells carcinoid cells grew on a layer of fibroblasts. The tendency to co-culture seemed to be less marked in cells from liver biopsy specimens. The amount of serotonin decreased to 63% 300 min after addition of the somatostatin analogue SMS 201-995 (SMS) to the culture, compared with controls (p < 0.05; n = 10). This decrease was observed up until 12 days, when SMS was added at each change of medium (p < 0.005; n = 8). In the first 10 min, however, SMS induced an increase in serotonin concentration (p < 0.005; n = 11). This effect may be related to other, immediate stimulatory effects of SMS seen in other cell lines originating from neural ridge-derived tissue. We believe it is important to elucidate the properties of individual tumours, as choice of therapy may vary between patients with the same diagnosis. We have described a method to obtain such information within a couple of days, before a definite treatment is selected.

Presence of IGF-I in human midgut carcinoid tumours--an autocrine regulator of carcinoid tumour growth?

The presence of IGF-I and IGF-I receptors in human midgut carcinoid tumours has been investigated. Using immunocytochemistry, IGF-I-positive tumour cells were demonstrated in 11/11 tumour cases studied. Labelling of consecutive sections with antibodies against IGF-I and proliferating cell nuclear antigen (PCNA)/cyclin demonstrated a co-distribution of the 2 antigens in carcinoid tumours. Extracts of tumour tissues were subjected to radioimmunoassay and shown to contain significant amounts of IGF-I. Reverse-phase HPLC of tumour extracts demonstrated a major IGF-I-immunoreactive component eluting in the position of rhIGF-I, but also 2 other more hydrophobic forms. Conditioned serum-free media from primary cultures of carcinoid tumors contained detectable amounts of IGF-I, indicating a spontaneous release of IGF-I from tumour cells into the culture medium. Levels of IGF-I in media were reduced (19%) after incubation of cultures with a somatostatin analogue for 4 days. IGF-I receptors were observed on tumour cells in 4/10 tumours by immunocytochemistry. Tumour cells with immunoreactive IGF-I receptors could be stimulated to enhanced growth, measured as an increase in DNA contents, by exogenous administration of IGF-I every 3-4 days for 2 weeks. The results show that cultured human midgut carcinoid tumours secrete IGF-I and that some of the tumours also have IGF-I receptors. We therefore suggest that IGF-I may act as an autocrine or paracrine regulator of carcinoid tumour-cell growth.

Production of transferable neuronotrophic factor(s) by human midgut carcinoid tumour cells; studies using cultures of rat fetal cholinergic neurons

A co-culture system was established between human midgut carcinoid tumour cells and rat fetal cholinergic neurons. In monocultures in serum-free media, only tumour cells survived, while neurons deteriorated. In serum-free co-cultures, neurons displayed outgrowth of neuritic processes. Neurons of neuronal serum-free monocultures thrived if supplemented with conditioned media from tumour cell cultures grown serum-free. This indicates that tumour cells produce transferable growth factor(s) with potent neuronotrophic actions. Immunocytochemical studies indicate that this growth factor resembles nerve growth factor immunologically, since tumour cells were strongly immunoreactive after incubation with a rabbit anti-nerve growth factor antiserum, and furthermore expressed immunoreactive nerve growth factor receptors.

Fetal mouse kidney maturation in vitro: coordinated influences of epidermal growth factor, transferrin and hydrocortisone

We have investigated the individual and combined actions of epidermal growth factor (EGF), transferrin and hydrocortisone on the maturation of whole fetal mouse metanephroi maintained in serum-free conditions for up to 5 days. The presence of EGF (100 ng/ml) resulted in elevated levels of [3H]-thymidine incorporation when compared to controls; autoradiograms showed that the proliferation of mesenchymal cells in the nephrogenic zone is particularly enhanced as verified by cell counting. Brush border hydrolase activities (alkaline phosphatase and gamma-glutamyltransferase), on the other hand, were significantly diminished. Transferrin (5 micrograms/ml) slightly stimulated DNA synthesis and potentiated EGF mitogenic action. The activation of DNA replication by the growth factor seems to be mediated through the protein kinase C pathway. When added alone, hydrocortisone (10(-6) M) strongly inhibited DNA synthesis, stimulated hydrolase activities and exerted a positive effect on brush border differentiation. When combined with EGF or to EGF + transferrin, hydrocortisone counteracted the effects of these latter peptides on DNA synthesis and enzyme activities. Considering the earlier observation of a reciprocal relation between proliferation and differentiation during the neotubulogenic phase of kidney development, the results described in the current study suggest that synergistic and synarchic actions of these heterologous factors are involved in the regulation of tubulogenesis.

Somatostatin analogue and tissue cultures in the study of a human malignant glucagonoma

A patient with metastasizing glucagonoma producing multiple molecular forms of glucagon is reported. The patient responded to symptomatic treatment with a somatostatin analogue (SMS 201-995). Glucagonoma tumour cells were studied in two tissue culture systems: intraocular transplants of immunosuppressed rats and long-term cell cultures. In both systems, several region-specific glucagon antisera gave a positive immunoreaction with tumour cells indicating synthesis of multiple molecular species. Intraocular tumour transplants released glucagon into the chamber fluid. In animals with unilateral transplants, glucagon was also detected in the contralateral eye chamber, indicating passage from the transplants via unknown mechanisms. Treatment of tumour cells during culture with SMS 201-995 inhibited rapidly the spontaneous release of glucagon without evident cytotoxic effects. The inhibitory effect decreased with time.

Intra-ocular transplantation of carcinoid tumours from mastomys and humans

Carcinoid tumours from man and Mastomys (Praomys) natalensis produce a variety of peptide hormones. The study of these peptide-secreting tumours has been difficult because of the small amount of tissue available and because of limitations with present cell culture systems. The aim of this study was to establish an experimental model where carcinoid tumours could be maintained and their hormone secretion studied. The intra-ocular transplantation technique was chosen for its simplicity and high rate of success. Gastric carcinoid tumours from mastomys (n = 4) and human carcinoids (n = 2) (one bronchial and one ileal) were transplanted to the anterior eye chamber of Sprague-Dawley rats. Pieces of fresh tumour tissue were injected into the anterior eye chamber of rats and allowed to grow for 4-8 weeks. Rats transplanted with human tissue were immunosuppressed by daily injections with cyclosporin A (20 mg/kg). Eye chambers were inspected regularly and plasma from transplanted rats was collected for assay of peptide YY (PYY) and glucagon. Vascularization of transplants occurred within 1-2 days after transplantation in 70-80 per cent of all experiments. Microscopic analysis of transplants demonstrated a rich supply of blood vessels to tumour cells which contained characteristic neurosecretory granules. Transplanted rats had significantly (P less than 0.05) elevated levels of PYY (44-165 pmol/l) and glucagon (67-162 pmol/l) in plasma as compared with sham-operated rats (PYY 28-40 pmol/l, glucagon 33-40 pmol/l), indicating that hormone secretion by tumour cells in oculo was maintained.(ABSTRACT TRUNCATED AT 250 WORDS)

Coexistence of delta sleep-inducing peptide and serotonin in midgut carcinoid tumour cells in vivo and in vitro

By immunocytochemistry, delta sleep-inducing peptide (DSIP) was demonstrated to coexist with serotonin (5-HT) in a majority of midgut carcinoid tumour cells studied in biopsies and long-term cell cultures. Tumour cell colonies were characterized ultrastructurally and by confocal laser microscopy. The cultures produced several DSIP-like peptides chromatographically separated from culture media. DSIP has not yet proved to be a useful tumour marker clinically. Provocation with pentagastrin in patients with midgut carcinoid syndrome resulted in increased peripheral levels of 5HT, but not of DSIP.