Ovarian neuroendocrine tumor metastases can induce estrogen production in postmenopausal patients

Neuroendocrine tumors (NET) are malignant neoplasms that can be associated with specific hormonal syndromes. We describe a novel syndrome of postmenopausal vaginal bleeding and ovarian estradiol overproduction due to ovarian NET localizations. An extensive workup was performed for two index patients with ovarian metastases of small bowel neuroendocrine tumors and symptoms of postmenopausal vaginal bleeding. Clinically significant ovarian estrogen production was demonstrated by a combination of ovarian vein sampling and normalization of circulating estrogen levels after oophorectomy. Immunohistochemical analyses revealed marked aromatase immunoactivity in the ovarian NET cells, while CYP17A1 and SF-1 were detected in the adjacent ovarian stromal cells but not the NET cells. Ex vivo and in vivo endocrine tests were unable to identify a paracrine mechanism of ovarian estradiol overproduction by NET cells. A retrospective search of electronic medical records revealed that 21% (14/66) of postmenopausal patients with an ovarian NET localization reported symptoms of vaginal blood loss. Together, these findings support the presence of a novel NET-associated hormonal syndrome.

Epigenetic Mechanisms Modulated by Glucocorticoids With a Focus on Cushing Syndrome

In Cushing syndrome (CS), prolonged exposure to high cortisol levels results in a wide range of devastating effects causing multisystem morbidity. Despite the efficacy of treatment leading to disease remission and clinical improvement, hypercortisolism-induced complications may persist. Since glucocorticoids use the epigenetic machinery as a mechanism of action to modulate gene expression, the persistence of some comorbidities may be mediated by hypercortisolism-induced long-lasting epigenetic changes. Additionally, glucocorticoids influence microRNA expression, which is an important epigenetic regulator as it modulates gene expression without changing the DNA sequence. Evidence suggests that chronically elevated glucocorticoid levels may induce aberrant microRNA expression which may impact several cellular processes resulting in cardiometabolic disorders. The present article reviews the evidence on epigenetic changes induced by (long-term) glucocorticoid exposure. Key aspects of some glucocorticoid-target genes and their implications in the context of CS are described. Lastly, the effects of epigenetic drugs influencing glucocorticoid effects are discussed for their ability to be potentially used as adjunctive therapy in CS.

Somatostatin receptors and the associated intracellular machinery: the two sides of the coin

Somatostatin receptors (SSTs) are widely expressed in pituitary tumors and neuroendocrine neoplasms (NENs) of different origins, i.e. the gastrointestinal tract and the thorax (lungs and thymus), thus representing a well-established target for medical treatment with SST ligands (SRLs). However, the response to SRLs is highly heterogeneous between tumors. Two main factors can contribute to this variability: (i) the differential SST expression among tumor types and (ii) the differential expression/modulation of the SST-related intracellular machinery. In this literature review, we provide an overview of available data on the variable expression of SSTs in pituitary tumors and NENs, together with the resulting clinical implications. Moreover, we aim to describe the complex intracellular machinery involved in SST signaling and trafficking. Particularly, we will focus on β-arrestins and describe their role in receptor internalization and recycling, as well as the various functions of these scaffold molecules in tumor pathogenesis and progression. This review highlights the interplay between membrane receptors and intracellular machinery, together with its role in determining the clinical behavior of the tumor and the response to treatment in patients with pituitary tumors or NENs.

Midgut neuroendocrine tumor patients have a depleted gut microbiome with a discriminative signature

RATIONALE

When compared to other types of cancer, the prevalence of midgut neuroendocrine tumors (NET) has disproportionally increased over the past decades. To date, there has been very little progress in discovering (epi)genetic drivers and treatment options for these tumors. Recent microbiome research has revealed that enteroendocrine cells communicate with the intestinal microbiome and has provided novel treatment targets for various other cancer types. Hence, our aim was to analyze the role of the gut microbiome in midgut NET patients.

METHODS

Fecal samples, prospectively collected from patients and control subjects, were analyzed with next generation 16S sequencing. Patients with neuroendocrine carcinomas and recent antibiotics use were excluded. Relevant variables were extracted from questionnaires and electronic health records. Microbial composition was compared between patients and controls as well as between groups within the patient cohort.

RESULTS

87 midgut NET patients and 95 controls were included. Midgut NET patients had a less rich and diverse gut microbiome than controls (p < 0.001). Moreover, we identified 31 differentially abundant species and a gut microbial signature consisting of 17 species that was predictive of midgut NET presence with an area under the receiver operating characteristic curve of 0.863. Gut microbial composition was not directly associated with the presence of the carcinoid syndrome, tumor grade or multifocality. Nonetheless, we did observe a potential link between microbial diversity and the presence of carcinoid syndrome symptoms within the subset of patients with elevated 5-hydroxyindolacetic acid levels.

CONCLUSION

Midgut NET patients have an altered gut microbiome which suggests a role in NET development and could provide novel targets for microbiome-based diagnostics and therapeutics.

Applying HDACis to increase SSTR2 expression and radiolabeled DOTA-TATE uptake: from cells to mice

AIMS

The aim of our study was to determine the effect of histone deacetylase (HDAC) inhibitors (HDACis) on somatostatin type-2 receptor (SSTR2) expression and [111In]In-/[177Lu]Lu-DOTA-TATE uptake in vitro and in vivo.

MATERIALS AND METHODS

The human cell lines NCI-H69 (small-cell lung carcinoma) and BON-1 (pancreatic neuroendocrine tumor) were treated with HDACis (i.e. entinostat, mocetinostat (MOC), LMK-235, CI-994 or panobinostat (PAN)), and SSTR2 mRNA expression levels and [111In]In-DOTA-TATE uptake were measured. Furthermore, vehicle- and HDACi-treated NCI-H69 and BON-1 tumor-bearing mice were injected with radiolabeled DOTA-TATE followed by biodistribution studies. Additionally, SSTR2 and HDAC mRNA expression of xenografts, and of NCI-H69, BON-1, NCI-H727 (human pulmonary carcinoid) and GOT1 (human midgut neuroendocrine tumor) cells were determined.

KEY FINDINGS

HDACi treatment resulted in the desired effects in vitro. However, no significant increase in tumoral DOTA-TATE uptake was observed after HDACi treatment in NCI-H69 tumor-bearing animals, whereas tumoral SSTR2 mRNA and/or protein expression levels were significantly upregulated after treatment with MOC, CI-994 and PAN, i.e. a maximum of 2.1- and 1.3-fold, respectively. Analysis of PAN-treated BON-1 xenografts solely demonstrated increased SSTR2 mRNA expression levels. Comparison of HDACs and SSTR2 expression in BON-1 and NCI-H69 xenografts showed a significantly higher expression of 6/11 HDACs in BON-1 xenografts. Of these HDACs, a significant inverse correlation was found between HDAC3 and SSTR2 expression (Pearson r = -0.92) in the studied cell lines.

SIGNIFICANCE

To conclude, tumoral uptake levels of radiolabeled DOTA-TATE were not enhanced after HDACi treatment in vivo, but, depending on the applied inhibitor, increased SSTR2 expression levels were observed.

The Role of the IGF2 Methylation Score in Diagnosing Adrenocortical Tumors with Unclear Malignant Potential-Feasibility of Formalin-Fixed Paraffin-Embedded Tissue

The differentiation between benign and malignant adrenocortical tumors based on pathological assessment can be difficult. We present a series of 17 patients with unclear malignant tumors, of whom six had recurrent or metastatic disease. The assessment of the methylation pattern of insulin-like growth factor 2 (IGF2) regulatory regions in fresh frozen material has shown to be valuable in determining the malignancy of adrenocortical tumors, although this has not been elaborately tested in unclear malignant tumors. Since fresh frozen tissue was only available in six of the patients, we determined the feasibility of using formalin-fixed paraffin-embedded (FFPE) tissue for this method. We isolated DNA from FFPE tissue and matched the fresh frozen tissue of three patients with adrenocortical carcinoma. Methylation patterns of IGF2 regulatory regions were determined by pyrosequencing using different amounts of bisulfite-converted DNA (5 ng, 20 ng, 40 ng). Compared to fresh frozen tissue, FFPE tissue had a higher failure rate (fresh frozen 0%; FFPE 18.5%) and poor-to-moderate replicability (fresh frozen rho = 0.89-0.99, median variation 1.6%; FFPE rho = -0.09-0.85, median variation 7.7%). There was only a poor-to-moderate correlation between results from fresh frozen and FFPE tissue (rho = -0.28-0.70, median variation 13.2%). In conclusion, FFPE tissue is not suitable for determining the IGF2 methylation score in patients with an unclear malignant adrenocortical tumor using the currently used method. We, therefore, recommend fresh frozen storage of resection material for diagnostic and biobank purposes.

Rintatolimod: a potential treatment in patients with pancreatic cancer expressing Toll-like receptor 3

Pancreatic cancer has a dismal prognosis, and treatment options for patients with locally advanced or metastatic disease are limited. Early tumor progression after standard chemo- and or radiotherapy remains a major concern in managing these patients. Treating pancreatic cancer patients with the Toll-like receptor 3 (TLR-3) agonist rintatolimod (Ampligen^®) was effective in boosting the immune response. Rintatolimod acts via the TLR-3 receptor on several immune cells. However, the TLR-3 expression pattern in pancreatic cancer cells and how rintatolimod affects pancreatic cancer cells have not yet been investigated. The TLR-3 protein and mRNA expression were evaluated in thirteen PDAC tissue samples as well as in the human PDAC (hPDAC) cell lines CFPAC-1, MIAPaCa-2, and PANC-1 using immunohistochemistry and multiplexed gene expression analysis, respectively. The direct anti-tumor effects of rintatolimod were investigated using a proliferation and migration assay after different incubation time points with increasing concentrations of rintatolimod (ranging from 0.05 to 0.4 mg/ml). The TLR-3 protein and mRNA expression were heterogeneous between the PDAC tissue samples and the three hPDAC cell lines. TLR-3 protein and mRNA expression were high in CFPAC-1, moderate in MIAPaCa-2, and undetectable in PANC-1. Rintatolimod three-day treatment resulted in significantly reduced proliferation of CFPAC-1 cells compared to vehicle-treated control cells. In addition, after 24 hours, rintatolimod-treated CFPAC-1 cells showed less cell migration compared to vehicle-treated control cells, although this difference was not statistically significant. Lastly, we identified fifteen genes, altered with a Log₂ FOC > |1.0| in rintatolimod-treated CFPAC-1 cells, which were significantly related to three transcription factors (NFKB1, RELA, and SP1) regulating the TLR-3 signaling pathway. In conclusion, we propose that rintatolimod treatment might have a direct TLR-3-dependent anti-tumoral effect on pancreatic cancer cells expressing TLR-3.

Proteomic analysis of small intestinal neuroendocrine tumors and mesenteric fibrosis

Mesenteric metastases in small intestinal neuroendocrine tumors (SI-NETs) are associated with mesenteric fibrosis (MF) in a proportion of patients. MF can induce severe abdominal complications, and an effective preventive treatment is lacking. To elucidate possible novel therapeutic targets, we performed a proteomics-based analysis of MF. The tumor cell and stromal compartment of primary tumors and paired mesenteric metastases of SI-NET patients with MF (n = 6) and without MF (n = 6) was analyzed by liquid chromatography-mass spectrometry-based proteomics. Analysis of differential protein abundance was performed. Collagen alpha-1(XII) (COL12A1) and complement component C9 (C9) expression was evaluated by immunohistochemistry (IHC) in mesenteric metastases. A total of 2988 proteins were identified. Unsupervised hierarchical clustering showed close clustering of paired primary and mesenteric tumor cell samples. Comparing MF to non-MF samples, we detected differentially protein abundance solely in the mesenteric metastasis stroma group. There was no differential abundance of proteins in tumor cell samples or primary tumor stroma samples. Analysis of the differentially abundant proteins (n = 36) revealed higher abundance in MF samples of C9, various collagens and proteoglycans associated with profibrotic extracellular matrix dysregulation and signaling pathways. Proteins involved in fatty acid oxidation showed a lower abundance. COL12A1 and C9 were confirmed by IHC to have significantly higher expression in MF mesenteric metastases compared to non-MF. In conclusion, proteome profiles of SI-NETs with and without MF differ primarily in the stromal compartment of mesenteric metastases. Analysis of differentially abundant proteins revealed possible new signaling pathways involved in MF development. In conclusion, proteome profiles of SI-NETs with and without MF differ primarily in the stromal compartment of mesenteric metastases. Analysis of differentially abundant proteins revealed possible new signaling pathways involved in MF development.

Epigenetic regulation of SST2 expression in small intestinal neuroendocrine tumors

Background

Somatostatin receptor type 2 (SST₂) expression is critical for the diagnosis and treatment of neuroendocrine tumors and is associated with improved patient survival. Recent data suggest that epigenetic changes such as DNA methylation and histone modifications play an important role in regulating SST₂ expression and tumorigenesis of NETs. However, there are limited data on the association between epigenetic marks and SST₂ expression in small intestinal neuroendocrine tumors (SI-NETs).

Methods

Tissue samples from 16 patients diagnosed with SI-NETs and undergoing surgical resection of the primary tumor at Erasmus MC Rotterdam were analysed for SST₂ expression levels and epigenetic marks surrounding the SST₂ promoter region, i.e. DNA methylation and histone modifications H3K27me3 and H3K9ac. As a control, 13 normal SI-tissue samples were included.

Results

The SI-NET samples had high SST₂ protein and mRNA expression levels; a median (IQR) of 80% (70-95) SST₂-positive cells and 8.2 times elevated SST₂ mRNA expression level compared to normal SI-tissue (p=0.0042). In comparison to normal SI-tissue, DNA methylation levels and H3K27me3 levels were significantly lower at five out of the eight targeted CpG positions and at two out of the three examined locations within the SST₂ gene promoter region of the SI-NET samples, respectively. No differences in the level of activating histone mark H3K9ac were observed between matched samples. While no correlation was found between histone modification marks and SST₂ expression, SST₂ mRNA expression levels correlated negatively with DNA methylation within the SST₂ promoter region in both normal SI-tissue and SI-NETs (p=0.006 and p=0.04, respectively).

Conclusion

SI-NETs have lower SST₂ promoter methylation levels and lower H3K27me3 methylation levels compared to normal SI-tissue. Moreover, in contrast to the absence of a correlation with SST₂ protein expression levels, significant negative correlations were found between SST₂ mRNA expression level and the mean level of DNA methylation within the SST₂ promoter region in both normal SI-tissue and SI-NET tissue. These results indicate that DNA methylation might be involved in regulating SST₂ expression. However, the role of histone modifications in SI-NETs remains elusive.

Peripheral glucocorticoid receptor antagonism by relacorilant with modest HPA axis disinhibition

Glucocorticoid stress hormones are produced in response to hypothalamic-pituitary-adrenal (HPA) axis activation. Glucocorticoids are essential for physiology and exert numerous actions via binding to the glucocorticoid receptor (GR). Relacorilant is a highly selective GR antagonist currently undergoing a phase 3 clinical evaluation for the treatment of endogenous Cushing's syndrome. It was found that increases in serum adrenocorticotropic hormone (ACTH) and cortisol concentrations after relacorilant treatment were substantially less than the increases typically observed with mifepristone, but it is unclear what underlies these differences. In this study, we set out to further preclinically characterize relacorilant in comparison to the classical but non-selective GR antagonist mifepristone. In human HEK-293 cells, relacorilant potently antagonized dexamethasone- and cortisol-induced GR signaling, and in human peripheral blood mononuclear cells, relacorilant largely prevented the anti-inflammatory effects of dexamethasone. In mice, relacorilant treatment prevented hyperinsulinemia and immunosuppression caused by increased corticosterone exposure. Relacorilant treatment reduced the expression of classical GR target genes in peripheral tissues but not in the brain. In mice, relacorilant induced a modest disinhibition of the HPA axis as compared to mifepristone. In line with this, in mouse pituitary cells, relacorilant was generally less potent than mifepristone in regulating Pomc mRNA and ACTH release. This contrast between relacorilant and mifepristone is possibly due to the distinct transcriptional coregulator recruitment by the GR. In conclusion, relacorilant is thus an efficacious peripheral GR antagonist in mice with only modest disinhibition of the HPA axis, and the distinct properties of relacorilant endorse the potential of selective GR antagonist treatment for endogenous Cushing's syndrome.

Dissecting the in vitro efficacy of octreotide and cabergoline in GH- and GH/PRL-secreting pituitary tumors

CONTEXT

Cabergoline (CAB) is an off-label medical therapy for acromegaly, overshadowed by first-generation somatostatin receptor ligands, e.g. octreotide (OCT).

OBJECTIVE

Head-to-head comparison between OCT and CAB in inhibiting growth hormone (GH) secretion in primary cultures of GH- and GH/PRL-secreting tumors. To investigate the role of somatostatin (SST) and dopamine type 2 (D2R) receptor expression.

DESIGN

To evaluate the antisecretory effect of OCT and CAB, together with receptor mRNA expression, in 23 tumor cultures.

SETTING AND PATIENTS

Acromegaly patients referred to the Erasmus Medical Center (Rotterdam, The Netherlands).

INTERVENTIONS

72-hour OCT and CAB treatment (10 nM).

MAIN OUTCOME MEASURES

GH concentrations in cell culture media.

RESULTS

OCT showed a slightly higher efficacy compared with CAB (GH decrease -39.5% vs. -32.5%, p = 0.079). The effect of the two drugs was superimposable in GH/PRL co-secreting tumors (-42.1% vs. -44.8%), where SST1 and D2R had a higher expression compared to the pure GH-secreting ones (p = 0.020 and p = 0.026). OCT was more effective than CAB in 8/23 cultures, while CAB was more effective than OCT in 3/23 (CAB + group). In CAB + tumors, SST1 expression was higher compared to the other groups (p = 0.034). At ROC curve analysis, SST1 and D2R discriminated between GH and GH/PRL co-secretion (AUC 0.856, p = 0.013; AUC 0.822, p = 0.024). SST1 was the best predictor of CAB response (≥50% GH reduction, AUC 0.913, p = 0.006; 80% sensitivity, 94% specificity).

CONCLUSIONS

OCT is 5-10% more effective than CAB in vitro. SST1 mRNA expression can represent a reliable marker of GH/PRL co-secreting tumors showing a preferential response to CAB treatment.

Digital quantification of somatostatin receptor subtype 2a immunostaining: a validation study

OBJECTIVE

The aim of this study was to develop an open-source and reproducible digital quantitative analysis (DIA) of somatostatin receptor subtype 2a (SST2) staining in formalin-fixed paraffin-embedded tissues of pancreatic neuroendocrine tumors (panNETs) and growth hormone (GH)-secreting pituitary adenomas (GHomas).

DESIGN

SST2 immunostaining of 18 panNETs and 39 GHomas was assessed using a novel DIA protocol and compared with a widely used semi-quantitative immunoreactivity score (IRS).

METHODS

The DIA software calculates the staining intensity/area and the percentage of positive cells (%PC). Four representative images were selected for each sample by two independent selectors (S1 and S2), with the analysis performed by two independent analyzers (A1 and A2). Agreement between observers was calculated using the concordance correlation coefficient (CCC).

RESULTS

In panNETs, the CCC ranged 0.935-0.977 for intensity/area and 0.942-0.983 for %PC. In GHomas, the CCC ranged 0.963-0.997 for intensity/area and 0.979-0.990 for %PC. In both panNETs and GHomas, the DIA staining intensity was strongly correlated with the IRS (Spearman rho: 0.916-0.969, P < 0.001), as well as the DIA %PC with the IRS %PC (Spearman rh: 0.826-0.881, P < 0.001). In GHomas, the biochemical response to somatostatin receptor ligands correlated with SST2 expression, evaluated both as DIA intensity/area (Spearman rho: -0.448 to -0.527, P = 0.007-0.004) and DIA %PC (Spearman rho: -0.558 to -0.644, P ≤ 0.001).

CONCLUSIONS

The DIA has an excellent inter-observer agreement and showed a strong correlation with the widely used semi-quantitative IRS. The DIA protocol is an open-source, highly reproducible tool and provides a reliable quantitative evaluation of SST2 immunohistochemistry.

Immunomodulatory antitumor effect of interferon‑beta combined with gemcitabine in pancreatic cancer

Resistance to gemcitabine is common and critically limits its therapeutic efficacy in patients with pancreatic cancer. Interferon‑beta (IFN‑β) induces numerous antitumor effects and synergizes with gemcitabine treatment. The immunomodulatory effects of this treatment regimen have not yet been described. In the present study, the antitumor effect of IFN‑β combined with gemcitabine was investigated in immune competent mice. Mouse KPC3 cells were used in all experiments. Treatment effects were determined with cell proliferation assay. Reverse transcription‑quantitative PCR was used to measure gene expression. For in vivo experiments, cells were subcutaneously injected in immune competent mice. For immune profiling, NanoString analysis was performed on tumor samples of treated and untreated mice. Baseline expression of Ifnar‑1 and Ifnar‑2c in KPC3 cells was 1.42±0.16 and 1.50±0.17, respectively. IC50 value of IFN‑β on cell growth was high (>1,000 IU/ml). IFN‑β pre‑treatment increased the in vitro response to gemcitabine (1.3‑fold decrease in EC50; P<0.001). In vivo, tumor size was not statistically significant smaller in mice treated with IFN‑β plus gemcitabine (707±92 mm3 vs. 1,239±338 mm3 in vehicle‑treated mice; P=0.16). IFN‑β alone upregulated expression of numerous immune‑related genes. This effect was less pronounced when combined with gemcitabine. For the first time, to the best of our knowledge, the immunomodulatory effects of IFN‑β, alone and combined with gemcitabine, in pancreatic cancer were reported. Prognostic markers for predicting effective responses to IFN‑β therapy are urgently needed.

Reciprocal Interactions between Fibroblast and Pancreatic Neuroendocrine Tumor Cells: Putative Impact of the Tumor Microenvironment

Introduction: Pancreatic neuroendocrine neoplasms (PNENs) present with a fibrotic stroma that constitutes the tumor microenvironment (TME). The role played by stromal fibroblasts in the growth of PNENs and their sensitivity to the mTOR inhibitor RAD001 has not yet been established. Methods: We investigated reciprocal interactions between (1) human PNEN cell lines (BON-1/QGP-1) or primary cultures of human ileal neuroendocrine neoplasm (iNEN) or PNEN and (2) human fibroblast cell lines (HPF/HFL-1). Proliferation was assessed in transwell (tw) co-culture or in the presence of serum-free conditioned media (cm), with and without RAD001. Colony formation and migration of BON-1/QGP-1 were evaluated upon incubation with HPFcm. Results: Proliferation of BON-1 and QGP-1 increased in the presence of HFL-1cm, HPFcm, HFL-1tw and HPFtw (BON-1: +46−70% and QGP-1: +42−55%, p < 0.001 vs. controls) and HPFcm significantly increased the number of BON-1 or QGP-1 colonies (p < 0.05). This stimulatory effect was reversed in the presence of RAD001. Likewise, proliferation of human iNEN and PNEN primary cultures increased in the presence of HFL-1 or HPF. Reciprocally, BON-1cm and BONtw stimulated the proliferation of HPF (+90 ± 61% and +55 ± 47%, respectively, p < 0.001 vs. controls), an effect less pronounced with QGP-1cm or QGPtw (+19 to +27%, p < 0.05 vs. controls). Finally, a higher migration potential for BON-1 and QGP-1 was found in the presence of HPFcm (p < 0.001 vs. controls). Conclusions: Fibroblasts in the TME of PNENs represent a target of interest, the stimulatory effect of which over PNENs is mitigated by the mTOR inhibitor everolimus.

Aberrant tryptophan metabolism in stromal cells is associated with mesenteric fibrosis in small intestinal neuroendocrine tumors

BACKGROUND

Increased levels of serotonin secretion are associated with mesenteric fibrosis (MF) in small intestinal neuroendocrine tumors (SI-NETs). However, the profibrotic potential of serotonin differs between patients, and in this study, we aimed to gain an understanding of the mechanisms underlying this variability. To this end, we analyzed the proteins involved in tryptophan metabolism in SI-NETs.

METHODS

Proteomes of tumor and stroma from primary SI-NETs and paired mesenteric metastases of patients with MF (n = 6) and without MF (n = 6) were identified by liquid chromatography-mass spectrometry (LC-MS). The differential expression of proteins involved in tryptophan metabolism between patients with and without MF was analyzed. Concurrently, monoamine oxidase A (MAO-A) expression was analyzed in the tumor and stromal compartment by immunohistochemistry (IHC) and reported as intensity over area (I/A).

RESULTS

Of the 42 proteins involved in tryptophan metabolism, 20 were detected by LC-MS. Lower abundance of ten proteins was found in mesenteric metastases stroma in patients with MF. No differential expression was found in primary SI-NETs. In patients with MF, IHC showed lower MAO-A expression in the stroma of the primary SI-NETs (median 4.2 I/A vs 6.5 I/A in patients without MF, P = 0.003) and mesenteric metastases (median 2.1 I/A vs 2.8 I/A in patients without MF, P= 0.019).

CONCLUSION

We found a decreased expression of tryptophan and serotonin-metabolizing enzymes in the stroma in patients with MF, most notably in the mesenteric stroma. This might account for the increased profibrotic potential of serotonin and explain the variability in the development of SI-NET-associated fibrotic complications.

Sexual Dimorphism in Small-intestinal Neuroendocrine Tumors: Lower Prevalence of Mesenteric Disease in Premenopausal Women

CONTEXT

Small-intestinal neuroendocrine tumors (SI-NETs) have a modest but significantly higher prevalence and worse prognosis in male patients.

OBJECTIVE

This work aims to increase understanding of this sexual dimorphism in SI-NETs.

PATIENTS AND METHODS

Retrospectively, SI-NET patients treated in a single tertiary center were included and analyzed for disease characteristics. Estrogen receptor 1 (ESR1) and 2 (ESR2), progesterone receptor (PGR), and androgen receptor (AR) messenger RNA (mRNA) expression was assessed in primary tumors and healthy intestine. Estrogen receptor alpha (ERα) and AR protein expression were analyzed by immunohistochemistry in primary tumors and mesenteric metastases.

RESULTS

Of the 559 patients, 47% were female. Mesenteric metastasis/fibrosis was more prevalent in men (71% / 46%) than women (58% / 37%; P = 0.001 and P = 0.027, respectively). In women, prevalence of mesenteric metastases increased gradually with age from 41.1% in women <50 years to 71.7% in women >70 years. Increased expression of ESR1 and AR mRNA was observed in primary tumors compared to healthy intestine (both P < 0.001). ERα staining was observed in tumor cells and stroma with a strong correlation between tumor cells of primary tumors and mesenteric metastases (rho = 0.831, P = 0.02), but not in stroma (rho = -0.037, P = 0.91). AR expression was only found in stroma.

CONCLUSION

Sexual dimorphism in SI-NETs was most pronounced in mesenteric disease, and the risk of mesenteric metastasis in women increased around menopause. The combination of increased ERα and AR expression in the SI-NET microenvironment suggests a modulating role of sex steroids in the development of the characteristic SI-NET mesenteric metastasis and associated fibrosis.

Complicated Clinical Course in Incipient Gigantism Due to Treatment-resistant Aryl Hydrocarbon Receptor–Interacting Protein–mutated Pediatric Somatotropinoma

Background

Our objective was to describe the clinical course and treatment challenges in a very young patient with a pituitary adenoma due to a novel aryl hydrocarbon receptor–interacting protein (AIP) gene mutation, highlighting the limitations of somatostatin receptor immunohistochemistry to predict clinical responses to somatostatin analogs in acromegaly.

Case Report

We report the case of a 7-year-old boy presenting with headache, visual field defects, and accelerated growth following failure to thrive. The laboratory results showed high insulin-like growth factor I (IGF-I) (standardised deviation scores ( +3.49) and prolactin levels (0.5 nmol/L), and magnetic resonance imaging identified a pituitary macroadenoma. Tumoral/hormonal control could not be achieved despite 3 neurosurgical procedures, each time with apparent total resection or with lanreotide or pasireotide. IGF-I levels decreased with the GH receptor antagonist pegvisomant. The loss of somatostatin receptor 5 was observed between the second and third tumor resection. In vitro, no effect on tumoral GH release by pasireotide (with/without cabergoline) was observed. Genetic analysis revealed a novel germline AIP mutation: p.Tyr202∗ (pathogenic; class 4).

Discussion

In vitro response of tumor tissue to somatostatin may better predict tumoral in vivo responses of somatostatin analogs than somatostatin receptor immunohistochemistry.

Conclusion

We identified a novel pathologic AIP mutation that was associated with incipient acrogigantism in an extremely young patient who had a complicated course of disease. Growth acceleration can be masked due to failure to thrive. Tumoral growth hormone release in vivo may be predicted with in vitro exposure to somatostatin receptor analogs, as it cannot be assumed that all AIP-mutated somatotropinomas respond well to pasireotide.

Epigenetic regulation of somatostatin and somatostatin receptors in neuroendocrine tumors and other types of cancer

Both somatostatin (SST) and somatostatin receptors (SSTRs) are proteins with important functions in both physiological tissue and in tumors, particularly in neuroendocrine tumors (NETs). NETs are frequently characterized by high SSTRs expression levels. SST analogues (SSAs) that bind and activate SSTR have anti-proliferative and anti-secretory activity, thereby reducing both the growth as well as the hormonal symptoms of NETs. Moreover, the high expression levels of SSTR type-2 (SSTR2) in NETs is a powerful target for therapy with radiolabeled SSAs. Due to the important role of both SST and SSTRs, it is of great importance to elucidate the mechanisms involved in regulating their expression in NETs, as well as in other types of tumors. The field of epigenetics recently gained interest in NET research, highlighting the importance of this process in regulating the expression of gene and protein expression. In this review we will discuss the role of the epigenetic machinery in controlling the expression of both SSTRs and the neuropeptide SST. Particular attention will be given to the epigenetic regulation of these proteins in NETs, whereas the involvement of the epigenetic machinery in other types of cancer will be discussed as well. In addition, we will discuss the possibility to target enzymes involved in the epigenetic machinery to modify the expression of the SST-system, thereby possibly improving therapeutic options.

How to Differentiate Benign from Malignant Adrenocortical Tumors?

Simple Summary

Adrenocortical carcinoma is a rare cancer with a poor prognosis. Adrenal tumors are, however, commonly identified in clinical practice. Discrimination between benign and malignant adrenal tumors is of great importance to determine the appropriate treatment and follow-up strategy. This review summarizes the current diagnostic strategies and challenges to distinguish benign from malignant adrenal lesions. We will focus both on radiological and biochemical assessments, enabling diagnosis of the adrenal lesion preoperatively, and on histopathological and a wide variety of molecular assessments that can be done after surgical removal of the adrenal lesion. Furthermore, new non-invasive strategies such as liquid biopsies, in which blood samples are used to study circulating tumor cells, tumor DNA and microRNA, will be addressed in this review.

Abstract

Adrenocortical carcinoma (ACC) is a rare cancer with a poor prognosis. Adrenal incidentalomas are, however, commonly identified in clinical practice. Discrimination between benign and malignant adrenal tumors is of great importance considering the large differences in clinical behavior requiring different strategies. Diagnosis of ACC starts with a thorough physical examination, biochemical evaluation, and imaging. Computed tomography is the first-level imaging modality in adrenal tumors, with tumor size and Hounsfield units being important features for determining malignancy. New developments include the use of urine metabolomics, also enabling discrimination of ACC from adenomas preoperatively. Postoperatively, the Weiss score is used for diagnosis of ACC, consisting of nine histopathological criteria. Due to known limitations as interobserver variability and lack of accuracy in borderline cases, much effort has been put into new tools to diagnose ACC. Novel developments vary from immunohistochemical markers and pathological scores, to markers at the level of DNA, methylome, chromosome, or microRNA. Molecular studies have provided insights into the most promising and most frequent alterations in ACC. The use of liquid biopsies for diagnosis of ACC is studied, although in a small number of patients, requiring further investigation. In this review, current diagnostic modalities and challenges in ACC will be addressed.

Modifying Effects of Glucose and Insulin/Insulin-Like Growth Factors on Colon Cancer Cells

There are only a few experimental studies which have investigated effects of glucose alone, and glucose in combination with insulin/insulin-like growth factors (IGF) on the growth of colon cancer. In the present study, we studied in vitro in human colorectal cancer cells originating from four Dukes' stages of colorectal cancer the effects of glucose, insulin and IGFs on proliferation, migration, cell cycle progression and gene expression of the IGF system. Growth of colon cancer cells originating from a Dukes' stage A was glucose-dependent, whereas growth of cancer cells from Dukes' stage B, C and D was glucose-independent. Stimulatory effects of insulin and IGFs on cell growth were observed only in colon cancer cells originating from Dukes' stage C and D. IGF-II stimulated migration in Dukes' stage B cells only. The growth stimulatory effects in Dukes' stage C and D colorectal cancer cells were accompanied by G2/M arrest and associated with an increased IGF-IR/IGF-II receptor ratio. In conclusion, our in vitro data suggest that the stimulating effects of glucose, IGFs and insulin on proliferation differ between colorectal cancer cells from early and late Dukes' stages. Stimulatory effects of glucose on proliferation appear predominantly present in stage Dukes' stage A colorectal cancer cells, while in contrast growth factor-mediated stimulation of cell proliferation is more pronounced in Dukes' late stage (metastasized) colorectal cancer cells. Moreover, our study suggests that a stringent glucose control may be important to control tumor growth in early stages of colorectal cancer, while inhibition of the endocrine actions of the IGFs and insulin become more important in the late (metastasized) stages of colorectal cancer to restrain growth of colon cancer cells.

A Prospective Trial With Ketoconazole Induction Therapy and Octreotide Maintenance Treatment of Cushing’s Disease

Context: The lack of efficacy of octreotide in the medical treatment of Cushing’s disease (CD) may result from suppressive effects of hypercortisolism on somatostatin receptor subtype 2 (SST2) expression by corticotroph adenomas. We previously demonstrated that SST2 mRNA expression levels in corticotroph tumor cells from patients preoperatively treated with cortisol-lowering therapy are significantly higher compared to those from patients with uncontrolled CD at time of surgery. It may be hypothesized that control of cortisol production induced by steroidogenesis inhibitors may reverse SST2 expression and increase efficacy of tumor-directed therapy with octreotide. Objective: To evaluate the efficacy of a sequential strategy of initiation treatment with ketoconazole (KTC) to reduce cortisol levels, followed by octreotide as maintenance therapy in patients with CD. Patients and Design: 14 adult patients with CD were prospectively enrolled. All patients started on KTC (600-800 mg/day), and once cortisol levels were normalized, octreotide 20 mg/4 weeks was initiated which could eventually be increased to 30 mg/4 weeks. After two months of combined therapy, patients were maintained on octreotide monotherapy until the end of the study period (9 months). Treatment success was assessed by the mean of 2 collections of urinary free cortisol (UFC) levels. Results: The mean age of our study population (14 patients) was 48.6 years, 64% (n=8) were female, 85% (n=12) were newly diagnosed and naïve in treatment. Ketoconazole was able to normalize UFC level in 11 (79%) patients. Subsequently, octreotide effectively sustained normal UFC levels in 3 patients (27%) (responders). Four (36%) other patients showed a partial response to octreotide. In 3 patients, normal UFC levels were sustained for one- or two-months following discontinuation of KTC and in the other partial responder, the UFC levels at follow-up decreased by at least 50% of the baseline levels. The remaining 4 (36%) patients developed hypercortisolism as soon as ketoconazole was stopped (non-responders). Responders to octreotide had lower UFC levels at baseline when compared to partial and non-responders (1.40 ± 0.06 vs. 2.05 ± 0.20 ULN, p=0.08). Two of three responders showed improvement in weight, waist circumference, and systolic and diastolic blood pressure during the treatment period. In terms of side effects, one patient discontinued KTC because of gastrointestinal intolerance and 5 patients had a transient increase in liver enzymes. Conclusions: This proof-of-concept study shows that the sequential treatment with ketoconazole to lower cortisol levels followed by octreotide to maintain normal cortisol production seems effective in a subset of patients with mild CD. Ongoing studies aim to evaluate whether this is the result from increased SST2 expression in corticotroph adenomas.

Levoketoconazole, the 2S,4R Enantiomer of Ketoconazole, a New Steroidogenesis Inhibitor for Cushing's Syndrome Treatment

INTRODUCTION

Racemic ketoconazole (RK) is a steroidogenesis inhibitor used for treatment of Cushing's syndrome. Levoketoconazole (COR-003), the pure 2S,4R enantiomer, is potentially more potent and safe compared to RK. We compared in vitro effects of levoketoconazole and RK on adrenocortical and pituitary adenoma cells.

MATERIALS AND METHODS

HAC15 cells and 15 primary human neoplastic adrenocortical cultures (+/- ACTH), and murine (AtT20) and human corticotroph adenoma cultures were incubated with levoketoconazole or RK (0.01-10 µM). Cortisol and ACTH were measured using a chemiluminescence immunoassay system, and steroid profiles by liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

In HAC15, levoketoconazole inhibited cortisol at lower concentrations (IC50: 0.300 µM) compared to RK (0.611 µM; P < 0.0001). IC50 values of levoketoconazole for basal cortisol production in primary adrenocortical cultures varied over a 24-fold range (0.00578-0.140 µM), with 2 patients having a higher sensitivity for levoketoconazole vs RK (2.1- and 3.7-fold). LC-MS/MS analysis in selected cases revealed more potent inhibition of cortisol and other steroid profile components by levoketoconazole vs RK. In AtT20, levoketoconazole inhibited cell growth and ACTH secretion (10 µM: -54% and -38%, respectively), and levoketoconazole inhibited cell number in 1 of 2 primary human corticotroph pituitary adenoma cultures (-44%, P < 0.001).

CONCLUSION

Levoketoconazole potently inhibits cortisol production in adrenocortical cells, with a variable degree of suppression between specimens. Levoketoconazole inhibits adrenal steroid production more potently compared to RK and might also inhibit ACTH secretion and growth of pituitary adenoma cells. Together with previously reported potential advantages, this indicates that levoketoconazole is a promising novel pharmacotherapy for Cushing's syndrome.

Efficacy of a Novel Second-Generation Somatostatin-Dopamine Chimera (TBR-065) in Human Medullary Thyroid Cancer: A Preclinical Study

INTRODUCTION

Somatostatin and dopamine (DA) receptors have a pivotal role in controlling hormone secretion and cell proliferation in different neuroendocrine neoplasms, including medullary thyroid cancer (MTC). In the present preclinical study, we evaluated the anti-tumor activity of TBR-065 (formerly BIM-23B065), a second-generation somatostatin-DA chimera, in 2 human MTC cell lines.

METHODS

The effects of lanreotide (LAN) and TBR-065 on cell growth and proliferation, calcitonin (CT) secretion, cell cycle, apoptosis, cell migration, and tumor-induced angiogenesis have been evaluated through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, DNA flow cytometry with propidium iodide (PI), Annexin V-FITC/PI staining, electrochemiluminescence immuno assay, wound-healing assay, and zebrafish platform, respectively.

RESULTS

TBR-065 exerted a more prominent anti-tumor activity than LAN in both MTC cell lines, as shown by inhibition of cell proliferation (maximal inhibition in TT: -50.3 and -37.6%, respectively; in MZ-CRC-1: -58.8 and -27%, respectively) and migration (in TT: -42.7 and -22.9%, respectively; in MZ-CRC-1: -75.5 and -58.2%, respectively). Only the new chimera decreased significantly the fraction of cells in S phase (TT: -33.8%; MZ-CRC-1: -18.8%) and increased cells in G2/M phase (TT: +13%; MZ-CRC-1: +30.5%). In addition, TBR-065 exerted a more prominent pro-apoptotic effect than LAN in TT cells. A concomitant decrease in CT secretion was observed after 2 days of incubation with both drugs, with a more relevant effect of TBR-065. However, neither LAN nor TBR-065 showed any effect on tumor-induced angiogenesis, as evaluated using a zebrafish/tumor xenograft model.

DISCUSSION/CONCLUSION

In MTC cell lines, a second-generation somatostatin-DA analog, TBR-065, exerts a more relevant anti-tumor activity than LAN, through modulation of cell cycle, induction of apoptosis, and reduction in migration. Further studies are required to establish whether TBR-065 has comparable potent inhibitory effects on tumor growth in vivo.

Type I interferons in pancreatic cancer and development of new therapeutic approaches

Immunotherapy has emerged as a new treatment strategy for cancer. However, its promise in pancreatic cancer has not yet been realized. Understanding the immunosuppressive tumor microenvironment of pancreatic cancer, and identifying new therapeutic targets to increase tumor-specific immune responses, is necessary in order to improve clinical outcomes. Type I interferons, e.g. IFN-α and -β, are considered as an important bridge between the innate and adaptive immune system. Thereby, type I IFNs induce a broad spectrum of anti-tumor effects, including immunologic, vascular, as well as direct anti-tumor effects. While IFN therapies have been around for a while, new insights into exogenous and endogenous activation of the IFN pathway have resulted in new IFN-related cancer treatment strategies. Here, we focus on the pre-clinical and clinical evidence of novel ways to take advantage of the type I IFN pathway, such as IFN based conjugates and activation of the STING and RIG-I pathways.