Role of Somatostatin Analogues in the Treatment of Neuroendocrine Tumors

Neuropeptides or their receptors in pathogenesis of lung diseases and therapeutic potentials

There are complex interactions between the immune system and the nervous system in the lung. The nervous system perceives environmental stimuli and transmits these signals to immune cells via neurotransmitters, which is essential for effective immunity and environmental balance. Neuropeptides are important neurotransmitters in the lung, where they regulate immune responses through direct and indirect mechanisms, affecting the occurrence and development of lung diseases. In this review, we emphasize the role of neuropeptides in the pathogeneis of lung diseases and their potential therapeutic value for lung diseases.

Response heterogeneity as a new biomarker of treatment response in patients with neuroendocrine tumors

Aim: The RAISE project aimed to find a surrogate end point to predict treatment response early in patients with enteropancreatic neuroendocrine tumors (NET). Response heterogeneity, defined as the coexistence of responding and non-responding lesions, has been proposed as a predictive marker for progression-free survival (PFS) in patients with NETs. Patients & methods: Computerized tomography scans were analyzed from patients with multiple lesions in CLARINET (NCT00353496; n = 148/204). Cox regression analyses evaluated association between response heterogeneity, estimated using the standard deviation of the longest diameter ratio of target lesions, and NET progression. Results: Greater response heterogeneity at a given visit was associated with earlier progression thereafter: week 12 hazard ratio (HR; 95% confidence interval): 1.48 (1.20-1.82); p < 0.001; n = 148; week 36: 1.72 (1.32-2.24); p < 0.001; n = 108. HRs controlled for sum of longest diameter ratio: week 12: 1.28 (1.04-1.59); p = 0.020 and week 36: 1.81 (1.20-2.72); p = 0.005. Conclusion: Response heterogeneity independently predicts PFS in patients with enteropancreatic NETs. Further validation is required.

Somatostatin, Cortistatin and Their Receptors Exert Antitumor Actions in Androgen-Independent Prostate Cancer Cells: Critical Role of Endogenous Cortistatin

Somatostatin (SST), cortistatin (CORT), and their receptors (SSTR1-5/sst5TMD4-TMD5) comprise a multifactorial hormonal system involved in the regulation of numerous pathophysiological processes. Certain components of this system are dysregulated and play critical roles in the development/progression of different endocrine-related cancers. However, the presence and therapeutic role of this regulatory system in prostate cancer (PCa) remain poorly explored. Accordingly, we performed functional (proliferation/migration/colonies-formation) and mechanistic (Western-blot/qPCR/microfluidic-based qPCR-array) assays in response to SST and CORT treatments and CORT-silencing (using specific siRNA) in different PCa cell models [androgen-dependent (AD): LNCaP; androgen-independent (AI)/castration-resistant PCa (CRPC): 22Rv1 and PC-3], and/or in the normal-like prostate cell-line RWPE-1. Moreover, the expression of SST/CORT system components was analyzed in PCa samples from two different patient cohorts [internal (n = 69); external (Grasso, n = 88)]. SST and CORT treatment inhibited key functional/aggressiveness parameters only in AI-PCa cells. Mechanistically, antitumor capacity of SST/CORT was associated with the modulation of oncogenic signaling pathways (AKT/JNK), and with the significant down-regulation of critical genes involved in proliferation/migration and PCa-aggressiveness (e.g., MKI67/MMP9/EGF). Interestingly, CORT was highly expressed, while SST was not detected, in all prostate cell-lines analyzed. Consistently, endogenous CORT was overexpressed in PCa samples (compared with benign-prostatic-hyperplasia) and correlated with key clinical (i.e., metastasis) and molecular (i.e., SSTR2/SSTR5 expression) parameters. Remarkably, CORT-silencing drastically enhanced proliferation rate and blunted the antitumor activity of SST-analogues (octreotide/pasireotide) in AI-PCa cells. Altogether, we provide evidence that SST/CORT system and SST-analogues could represent a potential therapeutic option for PCa, especially for CRPC, and that endogenous CORT could act as an autocrine/paracrine regulator of PCa progression.

Neuroendocrine liver metastases: The role of liver transplantation

PURPOSE OF REVIEW

Neuroendocrine tumor (NET) metastasis localized to the liver is an accepted indication for liver transplantation as such tumors have a low biological aggressiveness in terms of malignancy and are slow growing.

RECENT FINDINGS

The long-term results are comparable with and in some cases even better than those of transplantations performed for primary liver cancer. However, compared with nonmalignant conditions, neuroendocrine liver metastasis (NELM) may result in an inferior outcome of transplantation. In the face of the scarcity of donated organs and recent improved results of non-surgical treatment for NELM, controversy over patient selection and timing for liver transplantation continues.

SUMMARY

In this review, we provide an overview of the diagnostic work-up and selection criteria of patients with NELM being considered for liver transplantation. Thereafter, we provide a critical analysis of the reported outcomes of OLT.

Eltrombopag is a potential target for drug intervention in SARS-CoV-2 spike protein

The COVID-19 pandemic, caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), is a current global threat for which there is an urgent need to search for an effective therapy. The transmembrane spike (S) glycoprotein of SARS-CoV-2 directly binds to the host angiotensin-converting enzyme 2 (ACE2) and mediates viral entrance, which is therefore considered as a promising drug target. Considering that new drug development is a time-consuming process, drug repositioning may facilitate rapid drug discovery dealing with sudden infectious diseases. Here, we compared the differences between the virtual structural proteins of SARS-CoV-2 and SARS-CoV, and selected a pocket mainly localizing in the fusion cores of S2 domain for drug screening. A virtual drug design algorithm screened the Food and Drug Administration-approved drug library of 1234 compounds, and 13 top scored compounds were obtained through manual screening. Through in vitro molecular interaction experiments, eltrombopag was further verified to possess a high binding affinity to S protein plus human ACE2 and could potentially affect the stability of the ACE2-S protein complex. Hence, it is worth further exploring eltrombopag as a potential drug for the treatment of SARS-CoV-2 infection.

An Update on Gastroenteropancreatic Neuroendocrine Neoplasms: From Mysteries to Paradigm Shifts

Although neuroendocrine neoplasms (NEN) were once thought to be rare and mostly "benign" diseases, they are now being redefined in light of recently discovered molecular information. NENs constitute a spectrum of variably differentiated neoplasms, ranging from well-differentiated tumors with a protracted course over many years to very aggressive neuroendocrine carcinomas. Although the majority of NEN are non-functional lesions, some of these tumors, do produce a hormonal hypersecretion syndrome. Their reappraisal has led scientist to unveil previously unknown oncogenic pathways and connections that resulted in a new category in the International Classification of Diseases (ICD-11) and a revised version of the World Health Organization Classification (WHO 2018). Complex diseases like NEN require a multidisciplinary approach that includes the perspectives of endocrinologists, medical and surgical oncologists, radiation oncologists, imaging specialists and pathologists. There are currently virtually thousands of ongoing trials evaluating the efficacy and safety of several molecular targeted therapies. The purpose of this review was to critically evaluate recent information regarding the pathogenesis, diagnosis and treatment of NEN.

The therapeutic efficacy of 177Lu-DOTATATE/DOTATOC in advanced neuroendocrine tumors: A meta-analysis

BACKGROUND

Somatostatin analog therapies showed great potential for patients suffering advanced neuroendocrine tumors (NETs). This study was aimed to evaluate the therapeutic efficacy of Lu-DOTATATE/DOTATOC (Lu-octreotate/octreotide) peptide receptor radionuclide therapy (PRRT) in advanced or inoperable NETs patients.

METHODS

Pubmed, Web of Science, Embase and Cochrane Library were searched from 1950 to April 2019. Eligible studies should include randomized or nonrandomized controlled trials (RCTs)-based investigations of Lu-octreotate/octreotide PRRT for NETs. All these studies were assessed with Response Evaluation Criteria in Solid Tumors (RECIST), RECIST 1.1, Southwest Oncology Group (SWOG) criteria or World Health Organization (WHO) criteria. Disease response rates (DRRs) and disease control rates (DCRs) were calculated according to each response criteria group. DRRs were defined as the percentages of patients with complete response (CR) + partial response (PR), while DCRs represented the percentages of patients with CR+ PR+ stable disease (SD). The pooled proportions were calculated with either a fixed-effects model or a random-effects model depending on the test for heterogeneity.

RESULTS

A total of 22 studies (1758 patients) were included in this meta-analysis: 8 studies with 478 patients met RECIST criteria, 10 studies with 1127 patients met RECIST 1.1 criteria, 5 studies with 459 patients met SWOG criteria, and 1 study with 40 patients met WHO criteria, and among these articles 1 study met both RECIST and RECIST 1.1 criteria and 1 met both RECIST 1.1 and SWOG criteria. The pooled DRRs were 33.0% (95% CI: 25.0%-42.0%, I = 65%), 35.0% (95% CI: 26.0%-45.0%, I = 91%) and 25.0% (95% CI: 14.0%-36.0%, I = 84%) according to RECIST, RECIST 1.1 and SWOG criteria, respectively. The pooled DCRs were 79.0% (95% CI: 75.0%-83.0%, I = 97%), 83.0% (95% CI: 78.0%-88.0%, I = 0) and 82.0% (95% CI: 75.0%-89.0%, I = 91%), respectively.

CONCLUSION

In advanced NETs patients, DRRs and DCRs were significantly elevated after initial treatment with Lu-DOTATATE PRRT, which shows that this treatment would be beneficial and promising for advanced or inoperable NETs patients.

Impact of Mesenteric Mass in Patients With Midgut Neuroendocrine Tumors

OBJECTIVES

In this study, we used the institutional pathological and clinical databases from The Mount Sinai Hospital to investigate the impact of mesenteric mass on clinical and staging features in small intestinal neuroendocrine tumors.

METHODS

Demographic, clinical, and staging data were collected. Tumor-node-metastasis stage was assigned according to the American Joint Committee on Cancer eighth edition staging manual. We used a χ-square test to evaluate the association between mesenteric mass and presenting symptoms, as well as the association between mesenteric mass and tumor characteristics, type of surgical resection, and use of somatostatin analogues.

RESULTS

Presence of mesenteric mass was strongly associated with highly symptomatic clinical presentation (P < 0.0001). Patients with a mesenteric mass were more likely to have more advanced tumor status (T3 and T4; P = 0.005). The presence of a mesenteric mass was also more strongly associated with metastatic disease (P = 0.002). Patients with a mesenteric mass were more likely to undergo extensive surgical resection (P < 0.0001) and be treated with somatostatin analogues (P < 0.003).

CONCLUSIONS

The data confirm our clinical observations that mesenteric involvement represents more extensive disease and is also associated with more aggressive treatment.

The long noncoding RNA landscape of neuroendocrine prostate cancer and its clinical implications

Background

Treatment-induced neuroendocrine prostate cancer (tNEPC) is an aggressive variant of late-stage metastatic castrate-resistant prostate cancer that commonly arises through neuroendocrine transdifferentiation (NEtD). Treatment options are limited, ineffective, and, for most patients, result in death in less than a year. We previously developed a first-in-field patient-derived xenograft (PDX) model of NEtD. Longitudinal deep transcriptome profiling of this model enabled monitoring of dynamic transcriptional changes during NEtD and in the context of androgen deprivation. Long non-coding RNA (lncRNA) are implicated in cancer where they can control gene regulation. Until now, the expression of lncRNAs during NEtD and their clinical associations were unexplored.

Results

We implemented a next-generation sequence analysis pipeline that can detect transcripts at low expression levels and built a genome-wide catalogue (n = 37,749) of lncRNAs. We applied this pipeline to 927 clinical samples and our high-fidelity NEtD model LTL331 and identified 821 lncRNAs in NEPC. Among these are 122 lncRNAs that robustly distinguish NEPC from prostate adenocarcinoma (AD) patient tumours. The highest expressed lncRNAs within this signature are H19, LINC00617, and SSTR5-AS1. Another 742 are associated with the NEtD process and fall into four distinct patterns of expression (NEtD lncRNA Class I, II, III, and IV) in our PDX model and clinical samples. Each class has significant (z-scores >2) and unique enrichment for transcription factor binding site (TFBS) motifs in their sequences. Enriched TFBS include (1) TP53 and BRN1 in Class I, (2) ELF5, SPIC, and HOXD1 in Class II, (3) SPDEF in Class III, (4) HSF1 and FOXA1 in Class IV, and (5) TWIST1 when merging Class III with IV. Common TFBS in all NEtD lncRNA were also identified and include E2F, REST, PAX5, PAX9, and STAF. Interrogation of the top deregulated candidates (n = 100) in radical prostatectomy adenocarcinoma samples with long-term follow-up (median 18 years) revealed significant clinicopathological associations. Specifically, we identified 25 that are associated with rapid metastasis following androgen deprivation therapy (ADT). Two of these lncRNAs (SSTR5-AS1 and LINC00514) stratified patients undergoing ADT based on patient outcome.

Discussion

To date, a comprehensive characterization of the dynamic landscape of lncRNAs during the NEtD process has not been performed. A temporal analysis of the PDX-based NEtD model has for the first time provided this dynamic landscape. TFBS analysis identified NEPC-related TF motifs present within the NEtD lncRNA sequences, suggesting functional roles for these lncRNAs in NEPC pathogenesis. Furthermore, select NEtD lncRNAs appear to be associated with metastasis and patients receiving ADT. Treatment-related metastasis is a clinical consequence of NEPC tumours. Top candidate lncRNAs FENDRR, H19, LINC00514, LINC00617, and SSTR5-AS1 identified in this study are implicated in the development of NEPC. We present here for the first time a genome-wide catalogue of NEtD lncRNAs that characterize the transdifferentiation process and a robust NEPC lncRNA patient expression signature. To accomplish this, we carried out the largest integrative study that applied a PDX NEtD model to clinical samples. These NEtD and NEPC lncRNAs are strong candidates for clinical biomarkers and therapeutic targets and warrant further investigation.

Pharmacological Inhibition of Class IIA HDACs by LMK-235 in Pancreatic Neuroendocrine Tumor Cells

Histone deacetylases (HDACs) play a key role in epigenetic mechanisms in health and disease and their dysfunction is implied in several cancer entities. Analysis of expression patterns in pancreatic neuroendocrine tumors (pNETs) indicated HDAC5 to be a potential target for future therapies. As a first step towards a possible treatment, the aim of this study was to evaluate the in vitro cellular and molecular effects of HDAC5 inhibition in pNET cells. Two pNET cell lines, BON-1 and QGP-1, were incubated with different concentrations of the selective class IIA HDAC inhibitor, LMK-235. Effects on cell viability were determined using the resazurin-assay, the caspase-assay, and Annexin-V staining. Western Blot and immunofluorescence microscopy were performed to assess the effects on HDAC5 functionality. LMK-235 lowered overall cell viability by inducing apoptosis in a dose- and time-dependent manner. Furthermore, acetylation of histone-H3 increased with higher LMK-235 concentrations, indicating functional inhibition of HDAC4/5. Immunocytochemical analysis showed that proliferative activity (phosphohistone H3 and Ki-67) decreased at highest concentrations of LMK-235 while chromogranin and somatostatin receptor 2 (SSTR2) expression increased in a dose-dependent manner. HDAC5 expression was found to be largely unaffected by LMK-235. These findings indicate LMK-235 to be a potential therapeutic approach for the development of an effective and selective pNET treatment.

BIOCHEMICAL RESPONSES IN SYMPTOMATIC AND ASYMPTOMATIC PATIENTS WITH NEUROENDOCRINE TUMORS: POOLED ANALYSIS OF 2 PHASE 3 TRIALS

OBJECTIVE

Neuroendocrine tumors (NETs) are associated with elevated 5-hydroxyindoleacetic acid (5-HIAA) and chromogranin A (CgA) levels. This study aimed to analyze relationships between urinary 5-HIAA and plasma CgA levels and clinical outcomes.

METHODS

Centrally assessed biomarker levels and correlations with progression-free survival (PFS) and carcinoid syndrome (CS) symptom control were evaluated in a pooled analysis of CLARINET (96-week randomized, double-blind, placebo-controlled) and ELECT (16-week randomized, double-blind, placebo-controlled, 32-week initial open label and ≥2 year long-term extension open label) studies of adults with NETs, with (ELECT) or without (CLARINET) CS at 97 institutions. Patients were treated with subcutaneous lanreotide depot 120 mg monthly.

RESULTS

Of 319 pooled patients, 86% and 95% had baseline 5-HIAA and CgA data, respectively, with 47% and 74% having levels greater than the upper limit of normal (ULN). PFS was longer among patients who experienced a decrease in biomarker levels at week 12, with statistical significance reached in the CgA cohort (not reached vs. 14.4 months; P<.0001). A large proportion (87%) of patients without symptoms of CS in the CLARINET study had detectable levels of 5-HIAA (48% >ULN). In ELECT, patients with CS who received lanreotide and experienced a biochemical response (≥50% decrease from baseline) achieved greater symptom control.

CONCLUSION

This pooled analysis of two randomized, placebo-controlled trials demonstrated that 5-HIAA and CgA are secreted as biochemical biomarkers in many patients with NETs, regardless of clinical syndromes. Significant biochemical response was associated with improved clinical outcomes, as measured by improved PFS or improved CS symptom control.

ABBREVIATIONS

5-HIAA = 5-hydroxyindoleacetic acid; CgA = chromogranin A; CI = confidence interval; CLARINET = Controlled Study of Lanreotide Antiproliferative Response in Neuroendocrine Tumors; CS = carcinoid syndrome; ELECT = Evaluation of Lanreotide Depot/Autogel Efficacy and Safety as a Carcinoid Syndrome Treatment; HR = hazard ratio; ITT = intention-to-treat; NET = neuroendocrine tumor; PanNET = pancreatic NET; PFS = progression-free survival; PPI = proton pump inhibitor; SSA = somatostatin analogue; ULN = upper limit of normal.

The Treatment Landscape and New Opportunities of Molecular Targeted Therapies in Gastroenteropancreatic Neuroendocrine Tumors

Neuroendocrine neoplasms (NENs) are a heterogeneous group of neoplasms that originate from neuroendocrine stem cells and express both neural and endocrine markers. They are found in almost every organ, and while NENs are mostly associated with slow growth, complications due to the uncontrolled secretion of active peptides, and metastatic disease, may significantly impair the quality of life and can ultimately lead to the death of affected individuals. Expanding knowledge of the genetic, epigenetic, and proteomic landscapes of NENs has led to a better understanding of their molecular pathology and consequently increased treatment options for patients. Here, we review the principal breakthroughs in NEN treatment management, owing largely to omics technologies over the last few years, current recommendations of systemic treatment, and ongoing research into the identification of predictive and response biomarkers based on molecular targeted therapies.

Neuropeptide G Protein-Coupled Receptors as Oncotargets

Neuropeptide G protein-coupled receptors (GPCRs) are overexpressed on numerous cancer cells. In a number of tumors, such as small cell lung cancer (SCLC), bombesin (BB) like peptides and neurotensin (NTS) function as autocrine growth factors whereby they are secreted from tumor cells, bind to cell surface receptors and stimulate growth. BB-drug conjugates and BB receptor antagonists inhibit the growth of a number of cancers. Vasoactive intestinal peptide (VIP) increases the secretion rate of BB-like peptide and NTS from SCLC leading to increased proliferation. In contrast, somatostatin (SST) inhibits the secretion of autocrine growth factors from neuroendocrine tumors (NETs) and decreases proliferation. SST analogs such as radiolabeled octreotide can be used to localize tumors, is therapeutic for certain cancer patients and has been approved for four different indications in the diagnosis/treatment of NETs. The review will focus on how BB, NTS, VIP, and SST receptors can facilitate the early detection and treatment of cancer.

Carcinoid-syndrome: recent advances, current status and controversies

PURPOSE OF REVIEW

To review recent advances and controversies in all aspects of carcinoid-syndrome.

RECENT FINDINGS

Over the last few years there have been a number of advances in all aspects of carcinoid syndrome as well as new therapies. These include new studies on its epidemiology which demonstrate it is increasing in frequency; increasing insights into the pathogenesis of its various clinical manifestations and into its natural history: definition of prognostic factors; new methods to verify its presence; the development of new drugs to treat its various manifestations, both initially and in somatostatin-refractory cases; and an increased understanding of the pathogenesis, natural history and management of carcinoid heart disease. These advances have generated several controversies and these are also reviewed.

SUMMARY

There have been numerous advances in all aspects of the carcinoid-syndrome, which is the most common functional syndrome neuroendocrine tumors produce. These advances are leading to new approaches to the management of these patients and in some cases to new controversies.

Lymph Node Metastasis in the Prognosis of Gastroenteropancreatic Neuroendocrine Tumors

OBJECTIVES

This study aimed to determine the prognostic use of the extent of lymph node (LN) involvement in patients with gastroenteropancreatic neuroendocrine tumors (GEP-NETs) by analyzing population-based data.

METHODS

Patients in the Surveillance, Epidemiology, and End Results registry were identified with histologically confirmed, surgically resected GEP-NETs. We divided patients into 3 lymph node ratio (LNR) groups based on the ratio of positive LNs to total LNs examined: 0.2 or less, greater than 0.2 to 0.5, and greater than 0.5. Disease-specific survival was compared according to LNR group.

RESULTS

We identified 3133 patients with surgically resected GEP-NETs. Primary sites included the stomach (11% of the total), pancreas (30%), colon (32%), appendix (20%), and rectum (7%). Survival was worse in patients with LNRs of 0.2 or less (hazard ratio [HR], 1.5; 95% confidence interval [CI], 1.2-2.0), greater than 0.2 to 0.5 (HR, 2.0; 95% CI, 1.6-2.5), and greater than 0.5 (HR, 3.1; 95% CI, 2.5-3.9) compared with N0 patients. Ten-year disease-specific survival decreased as LNR increased from N0 (81%) to 0.2 or less (69%), greater than 0.2 to 0.5 (55%), and greater than 0.5 (50%). Results were consistent for patients with both low- and high-grade tumors from most primary sites.

CONCLUSIONS

Degree of LN involvement is a prognostic factor at the most common GEP-NET sites. Higher LNR is associated with decreased survival.

Cell Cycle Protein Expression in Neuroendocrine Tumors: Association of CDK4/CDK6, CCND1, and Phosphorylated Retinoblastoma Protein With Proliferative Index

OBJECTIVES

Dysregulation of the cell cycle has been observed and implicated as an etiologic factor in a range of human malignancies, but remains relatively unstudied in neuroendocrine tumors (NETs). We evaluated expression of key proteins involved in cell cycle regulation in a large cohort of NETs.

METHODS

We evaluated immunohistochemical expression of CDKN1B, CDKN1A, CDKN2A, CDK2, CDK4, CDK6, cyclin D1, cyclin E1, and phosphorylated retinoblastoma protein (phospho-RB1) in a cohort of 267 patients with NETs. We then explored associations between cell cycle protein expression, mutational status, histologic features, and overall survival.

RESULTS

We found that high expression of CDK4, CDK6, CCND1, and phospho-RB1 was associated with higher proliferative index, as defined by MKI67. We additionally observed a trend toward shorter overall survival associated with low expression of CDKN1B. This association seemed strongest in SINETs (multivariate hazards ratio, 2.04; 95% confidence interval, 1.06-3.93; P = 0.03). We found no clear association between CDKN1B mutation and protein expression.

CONCLUSIONS

Our results suggest that dysregulation and activation of the CDK4/CDK6-CCND1-phospho-RB1 axis is associated with higher proliferative index in NETs. Investigation of the therapeutic potential of CDK4/CDK6 inhibitors in higher grade NETs is warranted.