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Federica Grillo, Tullio Florio, Francesco Ferraù, Elda Kara, Giuseppe Fanciulli, Antongiulio Faggiano, Annamaria Colao, and NIKE Group

In the last few years, the therapeutic approach for neuroendocrine neoplasms (NENs) has changed dramatically following the approval of several novel targeted treatments. The multitarget tyrosine kinase inhibitor (MTKI), sunitinib malate, has been approved by Regulatory Agencies in pancreatic NENs. The MTKI class, however, includes several other molecules (approved for other conditions), which are currently being studied in NENs. An in-depth review on the studies published on the MTKIs in neuroendocrine tumors such as axitinib, cabozantinib, famitinib, lenvatinib, nintedanib, pazopanib, sorafenib and sulfatinib was performed. Furthermore, we extensively searched on the Clinical Trial Registries databases worldwide, in order to collect information on the ongoing clinical trials related to this topic. Our systematic analysis on emerging MTKIs in the treatment of gastroenteropancreatic and lung NENs identifies in vitro and in vivo studies, which demonstrate anti-tumor activity of diverse MTKIs on neuroendocrine cells and tumors. Moreover, for the first time in the literature, we report an updated view concerning the upcoming clinical trials in this field: presently, phase I, II and III clinical trials are ongoing and will include, overall, a staggering 1667 patients. This fervid activity underlines the increasing interest of the scientific community in the use of emerging MTKIs in NEN treatment.

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Tim J Takkenkamp, Mathilde Jalving, Frederik J H Hoogwater, and Annemiek M E Walenkamp

Immunotherapy in the form of immune checkpoint inhibitors (ICIs) has transformed the treatment landscape in numerous types of advanced cancer. However, the majority of patients do not benefit from this treatment modality. Although data are scarce, in general, patients with low-grade neuroendocrine tumours (NETs) do not benefit from treatment with ICIs in contrast to patients with neuroendocrine carcinoma, in which a small subgroup of patients may benefit. Low- and intermediate-grade NETs predominantly lack factors associated with response to ICIs treatment, like immune cell infiltration, and have an immunosuppressive tumour metabolism and microenvironment. In addition, because of its potential influence on the response to ICIs, major interest has been shown in the tryptophan-degrading enzymes indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO). These enzymes work along the kynurenine pathway that deplete tryptophan in the tumour microenvironment. IDO and TDO are especially of interest in NETs since some tumours produce serotonin but the majority do not, which potentially deplete the precursor tryptophan. In this review, we summarize the current knowledge on the immune tumour microenvironment of neuroendocrine tumours and implications for treatment with immune checkpoint inhibitors. We also discuss (targetable) factors in the NET tumour microenvironment that potentially modulate the anti-cancer immune response.

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Aristides Lytras and George Tolis

In the context of multiple neuroendocrine tumor syndromes, reproductive abnormalities may occur via a number of different mechanisms, such as hyperprolactinemia, increased GH/IGF-1 levels, hypogonadotropic hypogonadism, hypercortisolism, hyperandrogenism, hyperthyroidism, gonadotropin hypersecretion, as well as, tumorigenesis or functional disturbances in gonads or other reproductive organs. Precocious puberty and/or male feminization is a feature of McCune–Albright syndrome (MAS), neurofibromatosis type 1 (NF1), Carney complex (CNC), and Peutz–Jeghers syndrome (PJS), while sperm maturation and ovulation defects have been described in MAS and CNC. Although tumorigenesis of reproductive organs due to a multiple neuroendocrine tumor syndrome is very rare, certain lesions are characteristic and very unusual in the general population. Awareness leading to their recognition is important especially when other endocrine abnormalities coexist, as occasionally they may even be the first manifestation of a syndrome. Lesions such as certain types of ovarian cysts (MAS, CNC), pseudogynecomastia due to neurofibromas of the nipple–areola area (NF1), breast disease (CNC and Cowden disease (CD)), cysts and ‘hypernephroid’ tumors of the epididymis or bilateral papillary cystadenomas (mesosalpinx cysts) and endometrioid cystadenomas of the broad ligament (von Hippel–Lindau disease), testicular Sertoli calcifying tumors (CNC, PJS) monolateral or bilateral macroochidism and microlithiasis (MAS) may offer diagnostic clues. In addition, multiple neuroendocrine tumor syndromes may be complicated by reproductive malignancies including ovarian cancer in CNC, breast and endometrial cancer in CD, breast malignancies in NF1, and malignant sex-cord stromal tumors in PJS.

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Maria Grazia Borrello, Antonella Aiello, Bernard Peissel, Maria Grazia Rizzetti, Piera Mondellini, Debora Degl'Innocenti, Veronica Catalano, Morena Gobbo, Paola Collini, Italia Bongarzone, Marco A Pierotti, Angela Greco, and Ettore Seregni

Activating mutations of RET, a gene encoding two isoforms of a tyrosine kinase receptor physiologically expressed in several neural crest-derived cell lineages, are associated with the inherited forms of medullary thyroid carcinoma (MTC). The identification and characterization of novel RET mutations involved in MTC is valuable, as RET gene testing plays a crucial role in the management of these patients. In an MTC patient, we have identified a germline c.1996A>G transition in heterozygosis leading to K666E substitution. In addition, the conservative S904S (c.2712C>G) and the non-conservative functional G691S (c.2071G>A) polymorphisms have been identified. Through functional studies, we demonstrate for the first time that K666E is a gain-of-function mutation with oncogenic potential, based on its ability to transform NIH3T3 cells. It was not possible to define whether K666E is a de novo or inherited RET variant in the patient, as the family history was negative for MTC, and the carrier status of family members could not be tested. Our results, together with a recent report of co-segregation of the mutation in three MTC families, suggest that K666E is a causative MTC mutation. As we have shown that the same patient allele carries both K666E and G691S variants, the latter known to increase downstream RET signaling, a possible role for the G691S polymorphism has also been investigated. We have demonstrated that, although RET-G691S is not oncogenic per se, it enhances the transforming activity of the RET-K666E mutant, thus suggesting a modifier role for this functional polymorphism.

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S Corbetta, L Vicentini, S Ferrero, A Lania, G Mantovani, D Cordella, P Beck-Peccoz, and A Spada

Previous studies indicate that nuclear factor kappaB (NF-κB) transcription factor is deregulated and overexpressed in several human neoplasias. The aim of this study was to test the hypothesis that the NF-κB pathway may be involved in parathyroid tumorigenesis. For this purpose, we determined the level of NF-κB activity, evaluated as phosphorylation of the transcription subunit p65, its modulation by specific and non-specific agents and its impact on cyclin D1 expression. Phosphorylated p65 levels present in parathyroid neoplasias (n = 13) were significantly lower than those found in normal tissues (n = 3; mean optical density (OD) 0.19 ± 0.1 vs 0.4 ± 0.1, P = 0.007), but there was no significant difference between adenomas and secondary and multiple endocrine neoplasia type 1 (MEN1)-related hyperplasia. Conversely, MEN2A (Cys634Arg)-related parathyroid samples showed extremely high levels of phosphorylated p65 that exhibited a nuclear localization at immunohistochemistry (n = 3). Phosphorylated p65 levels negatively correlated with menin expression (r2 = 0.42, P = 0.05). Tumor necrosis factor-α (TNFα) caused a significant increase in phosphorylated p65 levels (183 ± 13.8% of basal) while calcium sensing receptor (CaR) agonists exerted a significant inhibition (19.2 ± 3.3% of basal). Although TNFα was poorly effective in increasing cyclin D1 expression, NF-κB blockade by the specific inhibitor BAY11-7082 reduced FCS-stimulated cyclin D1 by about 60%. Finally, the inhibitory effects of CaR and BAY11-7082 on cyclin D1 expression were not additive – by blocking NF-κB CaR activation did not induce a further reduction in cyclin D1 levels. In conclusion, the study demonstrated that in parathyroid tumors: (1) p65 phosphorylation was dramatically increased by RET constitutive activation and was negatively correlated with menin expression, (2) p65 phosphorylation was increased and reduced by TNFα and CaR agonists respectively, and (3) blockade of the NF-κB pathway caused a significant decrease in cyclin D1 expression.

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Paola Caria, Tinuccia Dettori, Daniela V Frau, Angela Borghero, Antonello Cappai, Alessia Riola, Maria L Lai, Francesco Boi, Piergiorgio Calò, Angelo Nicolosi, Stefano Mariotti, and Roberta Vanni

RET/PTC rearrangement and BRAF V600E mutation are the two prevalent molecular alterations associated with papillary thyroid carcinoma (PTC), and their identification is increasingly being used as an adjunct to cytology in diagnosing PTC. However, there are caveats associated with the use of the molecular approach in fine-needle aspiration (FNA), particularly for RET/PTC, that should be taken into consideration. It has been claimed that a clonal or sporadic presence of this abnormality in follicular cells can distinguish between malignant and benign nodules. Nevertheless, the most commonly used PCR-based techniques lack the capacity to quantify the number of abnormal cells. Because fluorescence in situ hybridization (FISH) is the most sensitive method for detecting gene rearrangement in a single cell, we compared results from FISH and conventional RT-PCR obtained in FNA of a large cohort of consecutive patients with suspicious nodules and investigated the feasibility of setting a FISH-FNA threshold capable of distinguishing non-clonal from clonal molecular events. For this purpose, a home brew break-apart probe, able to recognize the physical breakage of RET, was designed. While a ≥3% FISH signal for broken RET was sufficient to distinguish nodules with abnormal follicular cells, only samples with a ≥6.8% break-apart FISH signal also exhibited positive RT-PCR results. On histological analysis, all nodules meeting the ≥6.8% threshold proved to be malignant. These data corroborate the power of FISH when compared with RT-PCR in quantifying the presence of RET/PTC in FNA and validate the RT-PCR efficiency in detecting clonal RET/PTC alterations.

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Valtter B Virtanen, Eero Pukkala, Reetta Kivisaari, Perttu P Salo, Antti Koivusalo, Johanna Arola, Päivi J Miettinen, Risto J Rintala, Markus Perola, and Mikko P Pakarinen

The objective of this study was to assess the occurrence of thyroid cancer and co-occurring RET mutations in a population-based cohort of adult Hirschsprung disease (HD) patients. All 156 patients operated for HD in a tertiary center during 1950–1986 were followed for thyroid malignancies up to 2010 through the nationwide Finnish Cancer Registry. Ninety-one individuals participated in clinical and genetic screening, which included serum calcitonin and thyroid ultrasound (US) with cytology. Exons 10, 11, 13, and 16 were sequenced in all, and all exons of RET in 43 of the subjects, including those with thyroid cancer, RET mutations, suspicious clinical findings, and familial or long-segment disease. Through the cancer registry, two cases (aged 35 and 37 years) of medullary thyroid cancer (MTC) were observed; the incidence for MTC was 340-fold (95% CI 52–1600) compared with average population. These individuals had C611R and C620R mutations in exon 10. One papillary thyroid cancer without RET mutations was detected by clinical screening. Four subjects (aged 31–50 years) with co-occurring RET mutations in exons 10 (C609R; n=1) and 13 (Y791F, n=3) had sporadic short-segment HD with normal thyroid US and serum calcitonin. Three novel mutations and five single-nucleotide polymorphisms were found outside exons 10 and 13 without associated signs of thyroid cancer. MTC-associated RET mutations were restricted to exons 10 and 13 affecting ∼5% of unselected adults with HD. Clinical thyroid assessment did not improve accuracy of genetic screening, which should not be limited to patients with familial or long-segment disease.

Restricted access

F W F Hanna, C F Johnston, J E S Ardill, and K D Buchanan

Abstract

Background: Salmon calcitonin (sCT) injection into rats has been reported to induce pituitary tumours. We have demonstrated the co-existence, in the rat-derived α-TSH cell line, of an sCT-like peptide, as well as a receptor for sCT.

Aim: This was to investigate the possible existence of sCT-like immunoreactivity (sCT-LI) in human neuroendocrine tumours.

Methods: A collection of human neuroendocrine tumours was tested, using a highly specific antibody for sCT. Immunostaining was abolished by preabsorption with sCT at concentrations higher than 1 μg/ml. However, as immunofluorescence was still obvious at the highest concentration (100 pg/ml) of hCT employed, any significant cross-reactivity was excluded.

Results: Of the human pituitary null cell tumours studied, positive staining was obtained in 2 out of 12, suggesting a similarity between the rat and human pituitary glands. None of the other pituitary tumours tested showed sCT-LI (these included 8 corticotroph tumours, 6 prolactinomas and 2 somatotroph tumours).

This work was extended to medullary thyroid carcinomas (MTCs) and a further group of neuroendocrine tumours, looking for the specificity of this sCT-LI among the various APUDomas.

All the tested MTCs (n=14) expressed sCT-LI, while none of the examined phaeochromocytomas (n=23), intestinal carcinoids (n=14), lung carcinoids (n=16), stomach carcinoids (n=2), rectal carcinoids (n=2), gastrinomas (n=4), insulinomas (n=12), oat cell carcinomas (n=7), carotid body tumours (n=9), VIPomas (n=3), or a glucagonoma (n=1) expressed sCT-LI. This indicates that this sCT-LI might be unique to MTC (and possibly the pituitary).

Conclusion: The possible existence of the most potent form of CT may provide an explanation for the vasomotor disturbances in MTC and may be a potential new tumour marker for MTC. Phylogenetically, the presence of a lower form of CT in mammalian tissues would give an insight into the conservation of the CT peptide family in evolution.

Endocrine-Related Cancer (1997) 4 191-195

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Zhihong Chen, Lora W Forman, Kenneth A Miller, Brandon English, Asami Takashima, Regine A Bohacek, Robert M Williams, and Douglas V Faller

The concept of targeting cancer therapeutics toward specific mutations or abnormalities in tumor cells, which are not found in normal tissues, has the potential advantages of high selectivity for the tumor and correspondingly low secondary toxicities. Many human malignancies display activating mutations in the Ras family of signal-transducing genes or over-activity of p21Ras-signaling pathways. Carcinoid and other neuroendocrine tumors have been similarly demonstrated to have activation of Ras signaling directly by mutations in Ras, indirectly by loss of Ras-regulatory proteins, or via constitutive activation of upstream or downstream effector pathways of Ras, such as growth factor receptors or PI3-kinase and Raf/mitogen-activated protein kinases. We previously reported that aberrant activation of Ras signaling sensitizes cells to apoptosis when the activity of the PKCδ isozyme is suppressed and that PKCδ suppression is not toxic to cells with normal levels of p21Ras signaling. We demonstrate here that inhibition of PKCδ by a number of independent means, including genetic mechanisms (shRNA) or small-molecule inhibitors, is able to efficiently and selectively repress the growth of human neuroendocrine cell lines derived from bronchopulmonary, foregut, or hindgut tumors. PKCδ inhibition in these tumors also efficiently induced apoptosis. Exposure to small-molecule inhibitors of PKCδ over a period of 24 h is sufficient to significantly suppress cell growth and clonogenic capacity of these tumor cell lines. Neuroendocrine tumors are typically refractory to conventional therapeutic approaches. This Ras-targeted therapeutic approach, mediated through PKCδ suppression, which selectively takes advantage of the very oncogenic mutations that contribute to the malignancy of the tumor, may hold potential as a novel therapeutic modality.

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Fritz-Line Vélayoudom-Céphise, Pierre Duvillard, Lydia Foucan, Julien Hadoux, Cecile N Chougnet, Sophie Leboulleux, David Malka, Joël Guigay, Diane Goere, Thierry Debaere, Caroline Caramella, Martin Schlumberger, David Planchard, Dominique Elias, Michel Ducreux, Jean-Yves Scoazec, and Eric Baudin

The new WHO classification of gastroenteropancreatic (GEP) neuroendocrine tumors (NET) implies that G3 neoplasms with mitotic index >20 and/or Ki67 index >20% are neuroendocrine carcinomas (NEC), described as poorly differentiated, small or large cell types, by analogy with lung NEC. To characterize the subgroup of non-small-cell-type GEP and thoracic NET with mitotic index >20 and/or Ki67 >20% according to their pathological features, response to cisplatin and overall survival (OS). We reviewed pathological and clinical presentation of G3 non-small-cell-type NET referred to our institution for 5 years. Data from 166 patients with metastatic thoracic and GEP-NET were collected. Twenty-eight patients (17%) fulfill the inclusion criteria. Tumors were classified as well-differentiated NET (G3-WDNET) in 42.8% of cases and poorly differentiated, large-cell NEC (G3-LCNEC) in 57.2% of cases. Plasma chromogranin A or neuron-specific enolase were elevated in 42 and 25% respectively of G3-WDNET and 31 and 50% of G3-LCNEC. Somatostatin receptor scintigraphy was positive in 88 and 50% of G3-WDNET or G3-LCNEC respectively. Complete or partial response to cisplatin was observed in 31% of cases, all classified as G3-LCNEC. The median OS was 41 months for G3-WDNET but 17 months for G3-LCNEC (P=0.34). Short survival was observed in 25% of G3-WDNET but 62.5% of G3-LCNEC patients (P=0.049). G3 ENETS GEP and thoracic neuroendocrine neoplasms (NEN) could constitute a heterogeneous subgroup of NEN as regards diagnosis, prognosis, and treatment. If confirmed, future classifications may consider splitting them into two groups according to their morphological differentiation.