Wängberg B

Comparative studies on the expression of somatostatin receptor subtypes, outcome of octreotide scintigraphy and response to octreotide treatment in patients with carcinoid tumours

We have compared the expression of somatostatin receptor (sstr) subtypes with the outcome of somatostatin receptor scintigraphy and the effect of somatostatin receptor activation in patients with disseminated carcinoid tumours. Tumour tissues from nine patients with midgut carcinoids (ileal) and three patients with foregut carcinoids (gastric, thymic) were analysed using Northern blotting. Expression of somatostatin receptors was demonstrated in all tumours (12 out of 12), with all five receptor subtypes present in 9 out of 12 tumours. Somatostatin receptor scintigraphy using [111In]DTPA-D-Phe1-octreotide visualized tumours in all patients (12 out of 12). The 111In activity concentrations in tumour tissue (T) and blood (B) were determined in three tumours 1-7 days after injection of the radionuclide. The T/B 111In activity concentration ratios ranged between 32 and 651. Clinically, treatment with the long-acting somatostatin analogue octreotide resulted in marked symptom relief accompanied by a significant reduction in tumour markers, for example urinary-5-HIAA levels (28-71% reduction). Incubation of midgut carcinoid tumours in primary culture with octreotide (10 microM) resulted in a reduction in spontaneously secreted serotonin (45-71% reduction) and 5-HIAA (41-94% reduction). The results demonstrate that carcinoid tumours possess multiple somatostatin receptor subtypes and that somatostatin analogues such as octreotide, which preferentially bind to somatostatin receptor subtype 2 and 5, can be used in the diagnosis and medical treatment of these tumours. In the future, novel somatostatin analogues with subtype specific receptor profiles may prove to be of value for individualizing the treatment of disseminated carcinoid tumour disease.

Uptake of meta-iodobenzylguanidine in neuroendocrine tumours is mediated by vesicular monoamine transporters

The radio-iodinated noradrenaline analogue meta-iodobenzylguanidine (MIBG) can be used for scintigraphy and radiation therapy of neuroendocrine (NE). The aim of the present study was to study the importance of vesicular monoamine transporters (VMATs) for the uptake of 123I-MIBG in NE tumours. In nude mice, bearing the human transplantable midgut carcinoid GOT1, all organs and xenografted tumours accumulated 123I after i.v. injection of 123I-MIBG. A high concentration of 123I was maintained in GOT1 tumours and adrenals, which expressed VMATs, but rapidly decreased in all other tissues. In the VMAT-expressing NE tumour cell lines GOT1 and BON and in VMAT-expressing primary NE tumour cell cultures (carcinoids, n=4 and pheochromocytomas, n=4), reserpine significantly reduced the uptake of 123I-MIBG. The membrane pump inhibitor clomipramine had no effect on the uptake of 123I-MIBG in GOT1 and BON cells, but inhibited the uptake in one out of four primary carcinoid cell cultures and three out of four primary pheochromocytoma cell cultures. In conclusion, VMATs and secretory granules are of importance for the uptake and retention of 123I-MIBG in NE tumours. Information about the type and degree of expression of VMATs in NE tumours may be helpful in future to select patients suitable for radiation therapy with radio-iodinated MIBG.

Acromegaly and Cushing's syndrome due to ectopic production of GHRH and ACTH by a thymic carcinoid tumour: in vitro responses to GHRH and GHRP‐6

A 50‐year‐old male presented with diabetes mellitus and Cushings syndrome associated with a large mediastinal mass. The levels of serum cortisol were high (1500–1800 nmol/l) without diurnal variation. Plasma ACTH levels (200–250 ng/l) and urinary excretion of cortisol were also increased. The levels of these hormones did not change in response to stimulation with corticotrophin releasing hormone (CRH) or suppression with high doses of dexamethasone. The patient had an elevated baseline GH level (7.3 mU/l), and the levels of immunoreactive GH‐releasing hormone (GHRH) in eight plasma samples were markedly increased (600–1500 ng/l). Circulating levels of IGF‐1, chromogranin A and neuropeptide Y (NPY) were also increased. Computer‐assisted tomography and octreotide scintigraphy revealed a large mediastinal tumour and metastases in the left supraclavicular fossa. During treatment with octreotide, the baseline GH level was decreased (to 4.4 mU/l), while the GH pulse height was unchanged. Surgical removal of most of the tumour tissue resulted in a further decrease in the baseline serum GH level to a value (1.6 mU/l) about 20% of that before treatment, while the pulse height and mean GH were affected to a lesser extent. Postoperatively, circulating levels of cortisol and IGF‐1 decreased, and the patient exhibited clinical improvement. Histological examination showed a neuroendocrine tumour with characteristics consistent with a foregut carcinoid of thymic origin. Immunoreactive GHRH, ACTH and NPY, but not immunoreactive GH, were detected in 80–90% of the tumour cells and the three peptides appeared to be co‐localized. In primary culture, cells from this tumour displayed calcium influx in response to GHRH or GH releasing peptide‐6 (GHRP‐6), while there were not such responses by cells from another carcinoid not producing GHRH, ACTH or NPY. These results demonstrate a rare case of ectopic production of GHRH, ACTH and NPY, and indicate that the tumour cells were responsive to GHRH and GHRP‐6 as well as octreotide.

The effect of a somatostatin analogue on the release of hormones from human midgut carcinoid tumour cells.

The use of a somatostatin analogue (SMS 201-995) has greatly facilitated the treatment of patients with the midgut carcinoid syndrome. Clinical studies have shown that SMS reduces the peripheral levels of tumour-produced serotonin (5-HT) and tachykinins, e.g. neuropeptide K (NPK), basally and after pentagastrin provocation. Some studies have indicated an inhibitory effect of SMS on tumour cell growth as well. In the present study we have investigated the effects of SMS on four different human midgut carcinoid tumours maintained in long term culture. Media levels of 5-HT and NPK-LI in tumour cell cultures decreased rapidly during incubation with SMS (10(-8)-10(-10) M) in all four tumours studied without evidence for tachyphylaxis (up to 6 weeks observation period). SMS treatment (10(-8) M) during 4 days reduced the media concentrations of 5-HT by 56%, while the intracellular contents of 5-HT were decreased by 27% indicating dual inhibitory effects on synthesis and secretion of 5-HT from tumour cells. The DNA contents of cultures were not affected by SMS (10(-8) M or 10(-10) M) treatment for 4 or 14 days. When tumour cell cultures were challenged with isoprenaline (IP) (10(-6) M) no reduction of the IP induced release of 5-HT could be detected after pretreatment of tumour cell cultures with SMS (10(-8) M) for 1 h, 4 h or 4 days. These studies provide evidence for a direct action of the somatostatin analogue on midgut carcinoid tumour cells, reducing both synthesis and secretion of hormones from tumour cells. This effect appears not to be related to inhibition of tumour cell growth. The inhibition of 5-HT secretion from tumour cells by SMS seems to operate via a second messenger system different from the one mediating the beta-adrenoceptor stimulated release of 5-HT.

Intraoperative detection of somatostatin-receptor-positive neuroendocrine tumours using indium-111-labelled DTPA-D-Phe1-octreotide.

After injection of 111In-labelled DTPA-D-Phe1-octreotide, intraoperative tumour localisation was performed using a scintillation detector in 23 patients with neuroendocrine tumours. Count rates from suspect tumour lesions and adjacent normal tissue were expressed as a ratio before (Rin situ) and after (Rex vivo) excision. 111In activity concentration ratios of tumour tissue to blood (T/B) were determined in a gamma counter. In patients with midgut carcinoids, (all scintigraphy positive), false Rin situ recordings were found in 4/29 macroscopically identified tumours. T/B ratios were all high (27-650). In patients with medullary thyroid carcinomas (eight out of ten scintigraphy positive), misleading Rin situ results were found in 4/37 macroscopically identified tumours. T/B ratios were lower (3-39) than those seen in midgut carcinoids. Two out of four patients with endocrine pancreatic tumours had positive scintigraphy, reliable intraoperative measurements and very high T/B ratios (910-1500). One patient with a gastric carcinoid had correct measurements in situ and ex vivo with high T/B ratios (71-210). In situ measurements added little information to preoperative scintigraphy and surgical findings using the present detection system. Rex vivo measurements were more reliable. The very high T/B ratios seen in midgut carcinoids and some endocrine pancreatic tumours would be favourable for future radiation therapy via somatostatin receptors.

Systematic review of surgery and outcomes in patients with primary aldosteronism

Primary aldosteronism (PA) is the most common cause of secondary hypertension. The main aims of this paper were to review outcome after surgical versus medical treatment of PA and partial versus total adrenalectomy in patients with PA.

Expression of somatostatin receptors in oncocytic (Hürthle cell) neoplasia of the thyroid

SummaryTen consecutive patients with Hürthle cell lesions of the thyroid (nodule/adenoma/carcinoma) were studied by 111In-DTPA-D-Phe1-octreotide scintigraphy. Octreotide scintigraphy localized the primary Hürthle cell tumour in eight patients as distinct areas of increased uptake of radionuclide. Two patients with Hürthle cell carcinoma, previously thyroidectomized, had their metastases visualized by octreotide scintigraphy. Northern analyses showed expression of multiple somatostain receptor subtypes. Visualization of the Hürthle cell tumour may be due to a higher expression of somatostatin receptors in the lesions than in surrounding normal thyroid tissue. The tissue/blood 111In concentration ratios for tumour samples from five patients showed clearly higher values than observed for normal connective tissue, muscle or lymph nodes. A relatively high uptake of 111In was also observed in goiter tissue, which may lead to misinterpretations. The main indication for octreotide scintigraphy in patients with Hürthle cell carcinoma is suspicion of metastatic disease.

Acquired hypermethylation of the P16INK4A promoter in abdominal paraganglioma: relation to adverse tumor phenotype and predisposing mutation

Recurrent alterations in promoter methylation of tumor suppressor genes (TSGs) and LINE1 (L1RE1) repeat elements were previously reported in pheochromocytoma and abdominal paraganglioma. This study was undertaken to explore CpG methylation abnormalities in an extended tumor panel and assess possible relationships between metastatic disease and mutation status. CpG methylation was quantified by bisulfite pyrosequencing for selected TSG promoters and LINE1 repeats. Methylation indices above normal reference were observed for DCR2 (TNFRSF10D), CDH1, P16 (CDKN2A), RARB, and RASSF1A. Z-scores for overall TSG, and individual TSG methylation levels, but not LINE1, were significantly correlated with metastatic disease, paraganglioma, disease predisposition, or outcome. Most strikingly, P16 hypermethylation was strongly associated with SDHB mutation as opposed to RET/MEN2, VHL/VHL, or NF1-related disease. Parallel analyses of constitutional, tumor, and metastasis DNA implicate an order of events where constitutional SDHB mutations are followed by TSG hypermethylation and 1p loss in primary tumors, later transferred to metastatic tissue. In the combined material, P16 hypermethylation was prevalent in SDHB-mutated samples and was associated with short disease-related survival. The findings verify the previously reported importance of P16 and other TSG hypermethylation in an independent tumor series. Furthermore, a constitutional SDHB mutation is proposed to predispose for an epigenetic tumor phenotype occurring before the emanation of clinically recognized malignancy.

Cytotoxic Effects of Valproic Acid on Neuroendocrine Tumour Cells.

Background/Aims: Histone deacetylases (HDACs) modulate lysine acetylation on histones and are frequently deregulated in cancer. HDAC inhibitors with potent anti-tumour effects have been developed and are now being tested in clinical trials. The aim of this study was to investigate the effects of valproic acid (VPA), an inhibitor of class I and class IIa HDACs, on neuroendocrine tumour (NET) cell growth. Methods: Three NET cell lines, GOT1 (small intestinal), KRJ-I (small intestinal), and BON (pancreatic), were treated with VPA and examined with respect to cell viability, cell cycle arrest, apoptosis, and global transcriptional response. Results: We found that VPA induced a dose-dependent growth inhibition of NET cells in vitro, which was mainly due to activation of extrinsic and intrinsic apoptotic pathways. VPA induced a major transcriptional response by altering the expression of 16-19% of the protein-coding genes in NET cell lines. Pathway analysis allowed the prediction of alterations in key regulatory pathways, e.g. activation of TGF-β1, FOXO3, p53 signalling, and inhibition of MYC signalling. Analysis of GOT1 xenografts showed reduced growth and reduced Ki-67 index, as well as an increase in apoptosis and necrosis after VPA treatment. Conclusions: We found that VPA treatment has a cytotoxic effect on NET cells of intestinal and pancreatic origin. There are several mechanisms by which VPA kills NET cells, which suggests the possibility of combination therapy. We propose that epigenetic therapy with HDAC inhibitors should be evaluated further in patients with NET disease.

Embolisation therapy in the midgut carcinoid syndrome-just tumour ischaemia?

Forty-eight patients with midgut carcinoid tumours and disseminated disease were treated at our unit 1986-1991. All patients underwent primary surgery with optimal tumour reduction. Twenty-seven patients with bilobar liver metastases had subsequent embolizations of the hepatic arteries to further reduce the functional tumour mass and were thereafter treated with a low dose of octreotide. The response to this treatment was evaluated by CT at 3 months postembolization. The patients could then be divided into 13 responders (no visible hepatic tumours or more than 50% reduction, group I) and 14 non-responders (less than 50 reduction or progression, group II). When these patients were studied biochemically and in terms of prognosis, the reduction of 5-HIAA levels postembolization was much more pronounced in group I (80 +/- 3%) then in group II (28 +/- 12%). The biochemical and radiological responses were long-lasting in group I, none of the patients needed further ischaemic treatment. Of specific interest were 3 patients with bilobar disease, who after selective unilobar embolisation normalised their 5-HIAA levels and had bilateral tumour regression. These findings indicate involvement of systemic effects in addition to tumour ischaemia alone. The initial biochemical response with marked decrease of 5-HIAA levels in combination with tumour regression may thus serve as an indicator of good prognosis.