Translation of molecular pathways into clinical trials of neuroendocrine tumors

Neuroendocrine Tumors: Genomics and Molecular Biomarkers with a Focus on Metastatic Disease

Neuroendocrine tumors (NETs) are considered rare tumors that originate from specialized endocrine cells. Patients often present with metastatic disease at the time of diagnosis, which negatively impacts their quality of life and overall survival. An understanding of the genetic mutations that drive these tumors and the biomarkers used to detect new NET cases is important to identify patients at an earlier disease stage. Elevations in CgA, synaptophysin, and 5-HIAA are most commonly used to identify NETs and assess prognosis; however, new advances in whole genome sequencing and multigenomic blood assays have allowed for a greater understanding of the drivers of NETs and more sensitive and specific tests to diagnose tumors and assess disease response. Treating NET liver metastases is important in managing hormonal or carcinoid symptoms and is imperative to improve patient survival. Treatment for liver-dominant disease is varied; delineating biomarkers that may predict response will allow for better patient stratification.

From chronic pruritus to neuroendocrine tumor: A case report

Chronic pruritus is a major and distressing symptom of many diseases of dermatological, neurological, psychogenic or systemic origin. This chronic itch could be a presenting sign of malignancy; therefore, paraneoplastic pruritus has also been associated with neuroendocrine tumors (NETs). This article focuses on a patient presenting with chronic pruritus for the past 12 months and who received numerous treatment schemes with very poor clinical improvement, that presented in the hospital for worsening of the chronic pruritus associated with skin rash and significant weight loss (approximately 6 kg over a 2-month period). The laboratory tests showed iron deficiency anemia, eosinophilia and negative tumor markers. In order to investigate the hypoanabolic and anemic syndromes, upper gastrointestinal endoscopy and colonoscopy, which showed no lesions or tumors, were employed. Skin biopsy was performed and antihistaminic and local steroid treatment was initiated. The patient's status worsened within a week and the patient was started on systemic steroid treatment with poor results. Computer tomography was performed to identify any tumor(s) located either in the pelvis or abdomen. A lesion was found in the terminal ileum, identified as a hypervascularized associating bulky lymphadenopathy. The patient was transferred to the surgical ward where right hemicolectomy with manual ileotransverse anastomosis L-L was performed. The histopathological result confirmed NET G2. The patient clinically improved, the skin lesions resolved and the itchiness disappeared. The general status improved significantly. NET G2 diagnosing was possible due to the atypic paraneoplastic sign: chronic pruritus. This case study highlights the association between itch and malignancy and presents an atypical way of NET presentation when all tumor markers remain negative.

NETest is superior to chromogranin A in neuroendocrine neoplasia: a prospective ENETS CoE analysis

INTRODUCTION

The absence of a reliable, universal biomarker is a significant limitation in neuroendocrine neoplasia (NEN) management. We prospectively evaluated two CgA assays, (NEOLISA, EuroDiagnostica) and (CgA ELISA, Demeditec Diagnostics (DD)) and compared the results to the NETest.

METHODS

NEN cohort (n = 258): pancreatic, n = 67; small intestine, n = 40; appendiceal, n = 10; rectal, n = 45; duodenal, n = 9; gastric, n = 44; lung, n = 43. Image-positive disease (IPD) (n = 123), image & histology- negative (IND) (n = 106), and image-negative and histology positive (n = 29). CgA metrics: NEOLISA, ULN: 108 ng/mL, DD: ULN: 99 ng/mL. Data mean ± s.e.m. NETest: qRT-PCR - multianalyte analyses, ULN: 20. All samples de-identified and assessed blinded. Statistics: Mann-Whitney U-test, Pearson correlation and McNemar-test.

RESULTS

CgA positive in 53/258 (NEOLISA), 32 (DD) and NETest-positive in 157/258. In image- positive disease (IPD, n = 123), NEOLISA-positive: 33% and DD: 19%. NETest-positive: 122/123 (99%; McNemar's Chi2= 79-97, P < 0.0001). NEOLISA was more accurate than DD (P = 0.0003). In image- negative disease (IND), CgA was NEOLISA-positive (11%), DD (8%), P = NS, and NETest (33%). CgA assays could not distinguish progressive (PD) from stable disease (SD) or localized from metastatic disease (MD). NETest was significantly higher in PD (47 ± 5) than SD (29 ± 1, P = 0.0009). NETest levels in MD (35 ± 2) were elevated vs localized disease (24 ± 1.3, P = 0.008).

CONCLUSIONS

NETest, a multigenomic mRNA biomarker, was ~99% accurate in the identification of NEN disease. The CgA assays detected NEN disease in 19-33%. Multigenomic blood analysis using NETest is more accurate than CgA and should be considered the biomarker standard of care.

Prospective Evaluation of the NETest as a Liquid Biopsy for Gastroenteropancreatic and Bronchopulmonary Neuroendocrine Tumors: An ENETS Center of Excellence Experience

BACKGROUND

There is a substantial unmet clinical need for an accurate and effective blood biomarker for neuroendocrine neoplasms (NEN). We therefore evaluated, under real-world conditions in an ENETS Center of Excellence (CoE), the clinical utility of the NETest as a liquid biopsy and compared its utility with chromogranin A (CgA) measurement.

METHODS

The cohorts were: gastroenteropancreatic NEN (GEP-NEN; n = 253), bronchopulmonary NEN (BPNEN; n = 64), thymic NEN (n = 1), colon cancer (n = 37), non-small-cell lung cancer (NSCLC; n = 63), benign lung disease (n = 59), and controls (n = 86). In the GEPNEN group, 164 (65%) had image-positive disease (IPD, n = 135) or were image-negative but resection-margin/biopsy-positive (n = 29), and were graded as G1 (n = 106), G2 (n = 49), G3 (n = 7), or no data (n = 2). The remainder (n = 71) had no evidence of disease (NED). In the BPNEN group, 43/64 (67%) had IPD. Histology revealed typical carcinoids (TC, n = 14), atypical carcinoids (AC, n = 14), small-cell lung cancer (SCLC, n = 11), and large-cell neuroendocrine carcinoma (LCNEC, n = 4). Disease status (stable or progressive) was evaluated according to RECIST v1.1. Blood sampling involved NETest (n = 563) and NETest/CgA analysis matched samples (n = 178). NETest was performed by PCR (on a scale of 0-100), with a score ≥20 reflecting a disease-positive status and >40 reflecting progressive disease. CgA positivity was determined by ELISA. Samples were deidentified and measurements blinded. The Kruskal-Wallis, Mann-Whitney U, and McNemar tests, and the area under the curve (AUC) of the receiver-operating characteristics (ROC) were used in the statistical analysis.

RESULTS

In the GEPNEN group, NETest was significantly higher (34.4 ± 1.8, p < 0.0001) in disease-positive patients than in patients with NED (10.5 ± 1, p < 0.0001), colon cancer patients (18 ± 4, p < 0.0004), and controls (7 ± 0.5, p < 0.0001). Sensitivity for detecting disease compared to controls was 89% and specificity was 94%. NETest levels were increased in G2 vs. G1 (39 ± 3 vs. 32 ± 2, p = 0.02) and correlated with stage (localized: 26 ± 2 vs. regional/distant: 40 ± 3, p = 0.0002) and progression (55 ± 5 vs. 34 ± 2 in stable disease, p = 0.0005). In the BPNEN group, diagnostic sensitivity was 100% and levels were significantly higher in patients with bronchopulmonary carcinoids (BPC; 30 ± 1.3) who had IPD than in controls (7 ± 0.5, p < 0.0001), patients with NED (24.1 ± 1.3, p < 0.005), and NSCLC patients (17 ± 3, p = 0.0001). NETest levels were higher in patients with poorly differentiated BPNEN (LCNEC + SCLC; 59 ± 7) than in those with BPC (30 ± 1.3, p = 0.0005) or progressive disease (57.8 ± 7), compared to those with stable disease (29.4 ± 1, p < 0.0001). The AUC for differentiating disease from controls was 0.87 in the GEPNEN group and 0.99 in BPC patients (p < 0.0001). Matched CgA analysis was performed in 178 patients. In the GEPNEN group (n = 135), NETest was significantly more accurate for detecting disease (99%) than CgA positivity (53%; McNemar test χ2 = 87, p < 0.0001). In the BPNEN group (n = 43), NETest was significantly more accurate for disease detection (100%) than CgA positivity (26%; McNemar's test χ2 = 30, p < 0.0001).

CONCLUSIONS

The NETest is an accurate diagnostic for GEPNEN and BPNEN. It exhibits tumor biology correlation with grading, staging, and progression. CgA as a biomarker is significantly less accurate than NETest. The NETest has substantial clinical utility that can facilitate patient management.

The Altered Metabolic Molecular Signatures Contribute to the RAD001 Resistance in Gastric Neuroendocrine Tumor

Although the inhibition of mTOR is a promising treatment for neuroendocrine tumors, several questions are still open for cell specificity and resistance. With the newly characterized gastric neuroendocrine tumor mouse model (CEA424-SV40 T antigen transgenic mice), the anti-tumor efficiency of RAD001 (Everolimus) was tested both in vitro and in vivo. Tumor samples were analyzed for the expression of RNA by cDNA microarrays and also signaling pathways to get more details on the local surviving or selected cells. RAD001 treatment dramatically slowed down tumor growth and prolonged the animals' survival. This inhibitory effect has a preference for tumor cells since gastrointestinal hormone and neuroendocrine tumor specific markers were more reduced than the epithelial ones. While phosphorylation of p70S6K was almost completely blocked both in vitro and in vivo, the phosphorylation of 4EBP1 was only partially inhibited in vitro and unaffected in vivo. RAD001 treatment induced feedback activation of metabolism related pathways like PI(3)K–Akt–mTOR and MEK/ERK signalings. An induction of senescence as well as differential expression of genes responsible for metabolism was also observed, which highlighted the contribution of metabolic molecular signatures to the escape of the tumor cells from the treatment. Together, our data revealed efficient anti-tumor ability of RAD001 in a new gastric neuroendocrine tumor mouse model system and offered new insights into the clinical aspects of the incomplete elimination of tumor cells in patients treated.

The clinical applications of a multigene liquid biopsy (NETest) in neuroendocrine tumors

PURPOSE

There are few effective biomarkers for neuroendocrine tumors. Precision oncology strategies have provided liquid biopsies for real-time and tailored decision-making. This has led to the development of the first neuroendocrine tumor liquid biopsy (the NETest). The NETest represents a transcriptomic signature of neuroendocrine tumor (NETs) that captures tumor biology and disease activity. The data have direct clinical application in terms of identifying residual disease, disease progress and the efficacy of treatment. In this overview we assess the available published information on the metrics and clinical efficacy of the NETest.

MATERIAL AND METHODS

Published data on the NETest have been collated and analyzed to understand the clinical application of this multianalyte biomarker in NETs.

RESULTS

NETest assay has been validated as a standardized and reproducible clinical laboratory measurement. It is not affected by demographic characteristics, or acid suppressive medication. Clinical utility of the NETest has been documented in gastroenteropancreatic, bronchopulmonary NETs, in paragangliomas and pheochromocytomas. The test facilitates accurate diagnosis of a NET disease, and real-time monitoring of the disease status (stable/progressive disease). It predicts aggressive tumor behavior, identifies operative tumor resection, and efficacy of the medical treatment (e.g. somatostatin analogues), or peptide receptor radionuclide therapy (PRRT). NETest metrics and clinical applications out-perform standard biomarkers like chromogranin A.

CONCLUSIONS

The NETest exhibits clinically competent metrics as an effective biomarker for neuroendocrine tumors. Measurement of NET transcripts in blood is a significant advance in neuroendocrine tumor management and demonstrates that blood provides a viable source to identify and monitor tumor status.

Synergistic Highly Potent Targeted Drug Combinations in Different Pheochromocytoma Models Including Human Tumor Cultures

There are no officially approved therapies for metastatic pheochromocytomas apart from ultratrace 131I-metaiodbenzylguanidine therapy, which is approved only in the United States. We have, therefore, investigated the antitumor potential of molecular-targeted approaches in murine pheochromocytoma cell lines [monocyte chemoattractant protein (MPC)/monocyte chemoattractant protein/3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)], immortalized mouse chromaffin Sdhb-/- cells, three-dimensional pheochromocytoma tumor models (MPC/MTT spheroids), and human pheochromocytoma primary cultures. We identified the specific phosphatidylinositol-3-kinase α inhibitor BYL719 and the mammalian target of rapamycin inhibitor everolimus as the most effective combination in all models. Single treatment with clinically relevant doses of BYL719 and everolimus significantly decreased MPC/MTT and Sdhb-/- cell viability. A targeted combination of both inhibitors synergistically reduced MPC and Sdhb-/- cell viability and showed an additive effect on MTT cells. In MPC/MTT spheroids, treatment with clinically relevant doses of BYL719 alone or in combination with everolimus was highly effective, leading to a significant shrinkage or even a complete collapse of the spheroids. We confirmed the synergism of clinically relevant doses of BYL719 plus everolimus in human pheochromocytoma primary cultures of individual patient tumors with BYL719 attenuating everolimus-induced AKT activation. We have thus established a method to assess molecular-targeted therapies in human pheochromocytoma cultures and identified a highly effective combination therapy. Our data pave the way to customized combination therapy to target individual patient tumors.

The NETest: The Clinical Utility of Multigene Blood Analysis in the Diagnosis and Management of Neuroendocrine Tumors

The neuroendocrine neoplasms test (NETest) is a multianalyte liquid biopsy that measures neuroendocrine tumor gene expression in blood. This unique signature precisely defines the biological activity of an individual tumor in real time. The assay meets the 3 critical requirements of an optimal biomarker: diagnostic accuracy, prognostic value, and predictive therapeutic assessment. NETest performance metrics are sensitivity and specificity and in head-to-head comparison are 4-fold to 10-fold more accurate than chromogranin A. NETest accurately identifies completeness of surgery and response to somatostatin analogs. Clinical registry data demonstrate significant clinical utility in watch/wait programs.

Histopathological, immunohistochemical, genetic and molecular markers of neuroendocrine neoplasms

Neuroendocrine neoplasms (NENs) arise from cells of the neuroendocrine system located in many sites amongst which most common are the gastrointestinal (GI) system and the lung. The efforts to assess the specific site of origin or predict the biological behavior of NENs is based upon a detailed study of neoplasm's architectural pattern, immunohistochemical, genetic and molecular profile. Immunohistochemistry is used to characterize the aggressivity of NENs, by assessing the proliferation index Ki-67, as well as the neuroendocrine differentiation by assessing chromogranin A (CgA) and CD56. Basal panels of immunohistochemical markers such as CDX-2, Isl-1, TTF-1, PAX6/8 are currently being used to allocate the neoplasms, while in dubious cases new markers are investigating. Unraveling the genetic and molecular mechanisms of NENs pathogenesis along with shedding light on the molecular heterogeneity of neoplasms and the individual patterns of molecular lesions, underlining these neoplasms may provide new tools in terms of diagnostics and therapeutics. Molecular targeted therapies (MTTs) such as everolimus and sunitinib have been the first example of druggable molecular targets implicated in NENs that have been approved for NEN treatment. New investigational drugs are developing along with genetic tests that may allow the identification of the specific subset of patients that will respond to each individual MTT. Multiparametrical molecular and genetic analysis such as the NETest and the MASTER are already in trials shedding light in a step-by-step management of NENs that allow not only the selection of an appropriate therapeutic option but also the identification of response to treatment or early relapse allowing an early amendment of the strategy. Summarizing the combination of histopathological, immunohistochemical, genetic and molecular profile of a NEN opens new horizons in the efficient management of NENs.

Targeted therapy of gastroenteropancreatic neuroendocrine tumours: preclinical strategies and future targets

Molecular targeted therapy of advanced neuroendocrine tumours (NETs) of the gastroenteropancreatic (GEP) system currently encompasses approved therapy with the mammalian target of rapamycin (mTOR) inhibitor everolimus and the multi-tyrosinkinase inhibitor sunitinib. However, clinical efficacy of these treatment strategies is limited by low objective response rates and limited progression-free survival due to tumour resistance. Further novel strategies for molecular targeted therapy of NETs of the GEP system are needed. This paper reviews preclinical research models and signalling pathways in NETs of the GEP system. Preclinical and early clinical data on putative novel targets for molecular targeted therapy of NETs of the GEP system are discussed, including PI3K, Akt, mTORC1/mTORC2, GSK3, c-Met, Ras-Raf-MEK-ERK, embryogenic pathways (Hedgehog, Notch, Wnt/beta-catenin, TGF-beta signalling and SMAD proteins), tumour suppressors and cell cycle regulators (p53, cyclin-dependent kinases (CDKs) CDK4/6, CDK inhibitor p27, retinoblastoma protein (Rb)), heat shock protein HSP90, Aurora kinase, Src kinase family, focal adhesion kinase and epigenetic modulation by histone deacetylase inhibitors.

A Delphic consensus assessment: imaging and biomarkers in gastroenteropancreatic neuroendocrine tumor disease management

The complexity of the clinical management of neuroendocrine neoplasia (NEN) is exacerbated by limitations in imaging modalities and a paucity of clinically useful biomarkers. Limitations in currently available imaging modalities reflect difficulties in measuring an intrinsically indolent disease, resolution inadequacies and inter-/intra-facility device variability and that RECIST (Response Evaluation Criteria in Solid Tumors) criteria are not optimal for NEN. Limitations of currently used biomarkers are that they are secretory biomarkers (chromogranin A, serotonin, neuron-specific enolase and pancreastatin); monoanalyte measurements; and lack sensitivity, specificity and predictive capacity. None of them meet the NIH metrics for clinical usage. A multinational, multidisciplinary Delphi consensus meeting of NEN experts (n = 33) assessed current imaging strategies and biomarkers in NEN management. Consensus (>75%) was achieved for 78% of the 142 questions. The panel concluded that morphological imaging has a diagnostic value. However, both imaging and current single-analyte biomarkers exhibit substantial limitations in measuring the disease status and predicting the therapeutic efficacy. RECIST remains suboptimal as a metric. A critical unmet need is the development of a clinico-biological tool to provide enhanced information regarding precise disease status and treatment response. The group considered that circulating RNA was better than current general NEN biomarkers and preliminary clinical data were considered promising. It was resolved that circulating multianalyte mRNA (NETest) had clinical utility in both diagnosis and monitoring disease status and therapeutic efficacy. Overall, it was concluded that a combination of tumor spatial and functional imaging with circulating transcripts (mRNA) would represent the future strategy for real-time monitoring of disease progress and therapeutic efficacy.

Predictive factors of response to mTOR inhibitors in neuroendocrine tumours

Medical treatment of neuroendocrine tumours (NETs) has drawn a lot of attention due to the recent demonstration of efficacy of several drugs on progression-free survival, including somatostatin analogs, small tyrosine kinase inhibitors and mTOR inhibitors (or rapalogs). The latter are approved as therapeutic agents in advanced pancreatic NETs and have been demonstrated to be effective in different types of NETs, with variable efficacy due to the development of resistance to treatment. Early detection of patients that may benefit from rapalogs treatment is of paramount importance in order to select the better treatment and avoid ineffective and expensive treatments. Predictive markers for therapeutic response are under intensive investigation, aiming at a tailored patient management and more appropriate resource utilization. This review summarizes the available data on the tissue, circulating and imaging markers that are potentially predictive of rapalog efficacy in NETs.

Additive Anti-Tumor Effects of Lovastatin and Everolimus In Vitro through Simultaneous Inhibition of Signaling Pathways

Background

The mTORC1-inhibitor everolimus shows limited efficacy in treating patients with gastro-entero-pancreatic or pulmonary neuroendocrine tumors (NETs), and poor outcome in patients with malignant pheochromocytoma or hepatic carcinoma. We speculated that any effect may be enhanced by antogonising other signaling pathways.

Methods

Therefore, we tested the effect of lovastatin—known to inhibit both ERK and AKT signaling—and everolimus, separately and in combination, on cell viability and signaling pathways in human midgut (GOT), pancreatic (BON1), and pulmonary (H727) NET, hepatocellular carcinoma (HepG2, Huh7), and mouse pheochromocytoma (MPC, MTT) cell lines.

Results

Lovastatin and everolimus separately significantly reduced cell viability in H727, HepG2, Huh7, MPC and MTT cells at clinically relevant doses (P ≤ 0.05). However, high doses of lovastatin were necessary to affect GOT or BON1 cell viability. Clinically relevant doses of both drugs showed additive anti-tumor effects in H727, HepG2, Huh7, MPC and MTT cells (P ≤ 0.05), but not in BON1 or GOT cells. In all cell lines investigated, lovastatin inhibited EGFR and AKT signaling. Subsequently, combination treatment more strongly inhibited EGFR and AKT signaling than everolimus alone, or at least attenuated everolimus-induced EGFR or AKT activation. Vice versa, everolimus constantly decreased pp70S6K and combination treatment more strongly decreased pp70S6K than lovastatin alone, or attenuated lovastatin-induced p70S6K activation: in BON1 cells lovastatin-induced EGFR inhibition was least pronounced, possibly explaining the low efficacy and consequent absent additive effect.

Conclusion

In summary, clinically relevant doses of lovastatin and everolimus were effective separately and showed additive effects in 5 out of 7 cell lines. Our findings emphasize the importance of targeting several interacting signaling pathways simultaneously when attempting to attenuate tumor growth. However, the variable reactions of the different cell lines highlight the necessity to understand the unique molecular aberrations in any tumor. Nevertheless, this combination seems worthy of being tested in vivo.

Consensus on biomarkers for neuroendocrine tumour disease

Management of neuroendocrine neoplasia represents a clinical challenge because of its late presentation, lack of treatment options, and limitations in present imaging modalities and biomarkers to guide management. Monoanalyte biomarkers have poor sensitivity, specificity, and predictive ability. A National Cancer Institute summit, held in 2007, on neuroendocrine tumours noted biomarker limitations to be a crucial unmet need in the management of neuroendocrine tumours. A multinational consensus meeting of multidisciplinary experts in neuroendocrine tumours assessed the use of current biomarkers and defined the perquisites for novel biomarkers via the Delphi method. Consensus (at >75%) was achieved for 88 (82%) of 107 assessment questions. The panel concluded that circulating multianalyte biomarkers provide the highest sensitivity and specificity necessary for minimum disease detection and that this type of biomarker had sufficient information to predict treatment effectiveness and prognosis. The panel also concluded that no monoanalyte biomarker of neuroendocrine tumours has yet fulfilled these criteria and there is insufficient information to support the clinical use of miRNA or circulating tumour cells as useful prognostic markers for this disease. The panel considered that trials measuring multianalytes (eg, neuroendocrine gene transcripts) should also identify how such information can optimise the management of patients with neuroendocrine tumours.

An Overview on the Sequential Treatment of Pancreatic Neuroendocrine Tumors (pNETs)

Patients suffering from pancreatic neuroendocrine tumors (pNETs) are now candidates to receive novel approved drugs that have demonstrated benefit in disease control rate and delay the time taken for tumor progression in Phase III clinical trials; for example, sunitinib, everolimus and lanreotide. Though pNETs represent a rare and heterogeneous disease, recent approaches are being taken to better understand the molecular pathways involved in carcinogenesis. Consequently, new treatment strategies are now available and others still under investigation show promising results. However, some questions around how to approach patients with pNETs are still unresolved, such as what the best sequence of treatments we can offer to each of our patients in the clinic at any time of their disease would be. Therapeutic decisions are, at the moment, guided by clinical judgment, based on different parameters coming from retrospective analysis and non-randomized clinical trials. However, advances in genomic research would lead to a more precise approach using therapeutic targets that would also allow the development of new agents, prognostic or predictive biomarkers and a better understanding of resistance mechanisms. The following article is a comprehensive review of the approved and investigational drugs in pNET, and highlights the current concerns about treatment sequencing, but also provides an update of some of the present and future efforts for an improvement in the therapeutic algorithm of the disease.

Aspirin inhibits cell viability and mTOR downstream signaling in gastroenteropancreatic and bronchopulmonary neuroendocrine tumor cells

AIM: To investigate the effect of aspirin on neuroendocrine tumor (NET) cell growth and signaling in vitro.

METHODS: Human pancreatic BON1, bronchopulmonary NCI-H727 and midgut GOT1 neuroendocrine tumor cells were treated with different concentrations of aspirin (from 0.001 to 5 mmol/L), and the resulting effects on metabolic activity/cell proliferation were measured using cell proliferation assays and SYBR-DNA-labeling after 72, 144 and 216 h of incubation. The effects of aspirin on the expression and phosphorylation of several critical proteins that are involved in the most common intracellular growth factor signaling pathways (especially Akt protein kinase B) and mammalian target of rapamycin (mTOR) were determined by Western blot analyses. Propidium iodide staining and flow cytometry were used to evaluate changes in cell cycle distribution and apoptosis. Statistical analysis was performed using a 2-tailed Student’s t-test to evaluate the proliferation assays and cell cycle analyses. The results are expressed as the mean ± SD of 3 or 4 independently performed experiments. Statistical significance was set at P < 0.05.

RESULTS: Treatment with aspirin suppressed the viability/proliferation of BON1, NCI-H727 and GOT1 cells in a time- and dose-dependent manner. Significant effects were observed at starting doses of 0.5-1 mmol/L and peaked at 5 mmol/L. For instance, after treatment with 1 mmol/L aspirin for 144 h, the viability of pancreatic BON1 cells decreased to 66% ± 13% (P < 0.05), the viability of bronchopulmonary NCI-H727 cells decreased to 53% ± 8% (P < 0.01) and the viability of midgut GOT1 cells decreased to 89% ± 6% (P < 0.01). These effects were associated with a decreased entry into the S phase, the induction of the cyclin-dependent kinase inhibitor p21 and reduced expression of cyclin-dependent kinase 4 and cyclin D3. Aspirin suppressed mTOR downstream signaling, evidenced by the reduced phosphorylation of the mTOR substrates 4E binding protein 1, serine/threonine kinase P70S6K and S6 ribosomal protein and inhibited glycogen synthase kinase 3 activity. We observed the (compensatory) activation of tuberous sclerosis 2, the serine/threonine specific protein kinase AKT and extracellular signal-regulated kinases.

CONCLUSION: Aspirin demonstrates promising anticancer properties for NETs in vitro. Further preclinical and clinical studies are needed.

18F-FDG and 18F-FLT-PET imaging for monitoring everolimus effect on tumor-growth in neuroendocrine tumors: studies in human tumor xenografts in mice

Introduction

The mTOR inhibitor everolimus has shown promising results in some but not all neuroendocrine tumors. Therefore, early assessment of treatment response would be beneficial. In this study, we investigated the in vivo and in vitro treatment effect of everolimus in neuroendocrine tumors and evaluated the performance of ¹⁸F-FDG and the proliferation tracer ¹⁸F-FLT for treatment response assessment by PET imaging.

Methods

The effect of everolimus on the human carcinoid cell line H727 was examined in vitro with the MTT assay and in vivo on H727 xenograft tumors. The mice were scanned at baseline with ¹⁸F-FDG or ¹⁸F-FLT and then treated with either placebo or everolimus (5 mg/kg daily) for 10 days. PET/CT scans were repeated at day 1,3 and 10.

Results

Everolimus showed significant inhibition of H727 cell proliferation in vitro at concentrations above 1 nM. In vivo tumor volumes measured relative to baseline were significantly lower in the everolimus group compared to the control group at day 3 (126±6% vs. 152±6%; p = 0.016), day 7 (164±7% vs. 226±13%; p<0.001) and at day 10 (194±10% vs. 281±18%; p<0.001). Uptake of ¹⁸F-FDG and ¹⁸F-FLT showed little differences between control and treatment groups, but individual mean uptake of ¹⁸F-FDG at day 3 correlated with tumor growth day 10 (r² = 0.45; P = 0.034), ¹⁸F-FLT mean uptake at day 1 correlated with tumor growth day 7 (r² = 0.63; P = 0.019) and at day 3 ¹⁸F-FLT correlated with tumor growth day 7 (r² = 0.87; P<0.001) and day 10 (r² = 0.58; P = 0.027).

Conclusion

Everolimus was effective in vitro and in vivo in human xenografts lung carcinoid NETs and especially early ¹⁸F-FLT uptake predicted subsequent tumor growth. We suggest that ¹⁸F-FLT PET can be used for tailoring therapy for neuroendocrine tumor patients through early identification of responders and non-responders.

Hallmarks of gastrointestinal neuroendocrine tumours: implications for treatment

In the past few years, there have been advances in the treatment of neuroendocrine tumours (NETs) and improvements in our understanding of NET biology. However, the benefits to patients have been relatively modest and much remains yet to be done. The 'Hallmarks of Cancer', as defined by Hanahan and Weinberg, provide a conceptual framework for understanding the aberrations that underlie tumourigenesis and to help identify potential targets for therapy. In this study, our objective is to review the major molecular characteristics of NETs, based on the recently modified 'Hallmarks of Cancer', and highlight areas that require further research.

[Drug therapy for neuroendocrine tumours]

The author aims to review the established medical treatment options of neuroendocrine tumours, which have expanded greatly in recent years and present the most important aspects to be considered in planning patients' management. Medical treatment is usually considered in advanced stages of these tumours, as well as in cases of hormone overproduction. Somatostatin analogues have been known to be effective in alleviating hormone excess syndromes, especially carcinoid syndrome for the past 25 years. There is a convincing evidence that the somatostatin analogue octreotide is useful as an antitumor agent, at least in well-differentiated small intestinal neuroendocrine tumours and probably also in those of pancreatic origin. Interferons may be also used and the indications for their use may be almost the same. Optimal patient selection is mandatory for the use of cytotoxic chemotherapy. Streptozotocin- and, recently, temozolomide-based chemotherapies should be considered in progressive phases of well differentiated (G1/G2) pancreatic neuroendocrine tumours. A cisplatin-etoposide combination is the first choice for the treatment of G3 neuroendocrine carcinomas of any origin. Recently, the mammalian target of rapamycin inhibitor everolimus and the combined tyrosine kinase inhibitor sunitinib were registered for the treatment of G1/G2 pancreatic neuroendocrine tumours. The most recent drug treatment recommendations and therapeutic algorithms to improve systemic therapy in patients with neuroendocrine tumours are summarized and novel drug candidates with particular potential for future management of these tumours are outlined.

Neuroendocrine phenotype alteration and growth suppression through apoptosis by MK-2206, an allosteric inhibitor of AKT, in carcinoid cell lines in vitro

Carcinoids are neuroendocrine malignancies characterized by their overproduction of various bioactive hormones that lead to the carcinoid syndrome. We have shown previously that AKT serves as a key regulator of growth and phenotypic expression of tumor markers in carcinoids by the genetic depletion of AKT expression. However, no small-molecule inhibitor of AKT kinase activity has been developed until recently. MK-2206, a novel allosteric inhibitor of AKT, is currently undergoing clinical trials for the treatment of solid tumors. In this study, we explored the effect of MK-2206 on carcinoid cell proliferation and bioactive hormone production in vitro in two carcinoid cell lines - pancreatic carcinoid BON and bronchopulmonary H727. Treatment with MK-2206 effectively suppressed AKT phosphorylation at serine 473 and significantly reduced cell proliferation in a dose-dependent manner. Most importantly, MK-2206 treatment resulted in a significant reduction in ASCL1, CgA, and NSE expression, collectively recognized as markers of neuroendocrine tumor malignancy. Furthermore, MK-2206-treated cells showed an increase in levels of cleaved PARP and cleaved caspase-3, with a concomitant reduction in levels of Mcl-1 and XIAP, indicating that the antiproliferative effect of MK-2206 occurs through the induction of apoptosis. In conclusion, MK-2206 suppresses carcinoid tumor growth, and alters its neuroendocrine phenotype, indicating that this drug may be beneficial for patients with carcinoid syndrome. These studies merit further clinical investigation.

Targeted therapies in neuroendocrine tumors (NET): clinical trial challenges and lessons learned

In the past 3 years, we have witnessed the completion of four randomized phase III studies in neuroendocrine tumors and the approval of two new drugs, everolimus and sunitinib, for the treatment of patients with well-differentiated pancreatic neuroendocrine tumors. These studies demonstrate a shift from case series and single-arm studies toward prospective, randomized controlled clinical trials and evidence-based therapy in the neuroendocrine tumor field. However, the clinical development of these agents also highlights the potential challenges awaiting other new drugs in this area. Herein, we discuss the strengths and weaknesses of the most recent phase II and phase III neuroendocrine tumor studies and discuss how limitations inherent in current trial design can lead to potential pitfalls. We also discuss how trial design can be improved, with the hope of increasing the number of drugs successfully developed to treat patients with neuroendocrine tumors.

Therapy of metastatic pancreatic neuroendocrine tumors (pNETs): recent insights and advances

Neuroendocrine tumors (NETs) [carcinoids, pancreatic neuroendocrine tumors (pNETs)] are becoming an increasing clinical problem because not only are they increasing in frequency, but they can frequently present with advanced disease that requires diagnostic and treatment approaches different from those used in the neoplasms that most physicians are used to seeing and treating. In the past few years there have been numerous advances in all aspects of NETs including: an understanding of their unique pathogenesis; specific classification systems developed which have prognostic value; novel methods of tumor localization developed; and novel treatment approaches described. In patients with advanced metastatic disease these include the use of newer chemotherapeutic approaches, an increased understanding of the role of surgery and cytoreductive methods, the development of methods for targeted delivery of cytotoxic agents, and the development of targeted medical therapies (everolimus, sunitinib) based on an increased understanding of the disease biology. Although pNETs and gastrointestinal NETs share many features, recent studies show they differ in pathogenesis and in many aspects of diagnosis and treatment, including their responsiveness to different therapies. Because of limited space, this review will be limited to the advances made in the management and treatment of patients with advanced metastatic pNETs over the past 5 years.