In1-ghrelin, a splice variant of ghrelin gene, is associated with the evolution and aggressiveness of human neuroendocrine tumors: Evidence from clinical, cellular and molecular parameters

Altered CELF4 splicing factor enhances pancreatic neuroendocrine tumors aggressiveness influencing mTOR and everolimus response

Pancreatic neuroendocrine tumors (PanNETs) comprise a heterogeneous group of tumors with growing incidence. Recent molecular analyses provided a precise picture of their genomic and epigenomic landscape. Splicing dysregulation is increasingly regarded as a novel cancer hallmark influencing key tumor features. We have previously demonstrated that splicing machinery is markedly dysregulated in PanNETs. Here, we aimed to elucidate the molecular and functional implications of CUGBP ELAV-like family member 4 (CELF4), one of the most altered splicing factors in PanNETs. CELF4 expression was determined in 20 PanNETs, comparing tumor and non-tumoral adjacent tissue. An RNA sequencing (RNA-seq) dataset was analyzed to explore CELF4-linked interrelations among clinical features, gene expression, and splicing events. Two PanNET cell lines were employed to assess CELF4 function in vitro and in vivo. PanNETs display markedly upregulated CELF4 expression, which is closely associated with malignancy features, altered expression of key tumor players, and distinct splicing event profiles. Modulation of CELF4 influenced proliferation in vitro and reduced in vivo xenograft tumor growth. Interestingly, functional assays and RNA-seq analysis revealed that CELF4 silencing altered mTOR signaling pathway, enhancing the effect of everolimus. We demonstrate that CELF4 is dysregulated in PanNETs, where it influences tumor development and aggressiveness, likely by modulating the mTOR pathway, suggesting its potential as therapeutic target.

Cellular Uptake of a Fluorescent Ligand Reveals Ghrelin O-Acyltransferase Interacts with Extracellular Peptides and Exhibits Unexpected Localization for a Secretory Pathway Enzyme

Ghrelin O-acyltransferase (GOAT) plays a central role in the maturation and activation of the peptide hormone ghrelin, which performs a wide range of endocrinological signaling roles. Using a tight-binding fluorescent ghrelin-derived peptide designed for high selectivity for GOAT over the ghrelin receptor GHSR, we demonstrate that GOAT interacts with extracellular ghrelin and facilitates ligand cell internalization in both transfected cells and prostate cancer cells endogenously expressing GOAT. Coupled with enzyme mutagenesis, ligand uptake studies support the interaction of the putative histidine general base within GOAT with the ghrelin peptide acylation site. Our work provides a new understanding of GOAT's catalytic mechanism, establishes that GOAT can interact with ghrelin and other peptides located outside the cell, and raises the possibility that other peptide hormones may exhibit similar complexity in their intercellular and organismal-level signaling pathways.

Spliceosomic dysregulation unveils NOVA1 as a candidate actionable therapeutic target in pancreatic neuroendocrine tumors

Dysregulation of the splicing machinery is emerging as a hallmark in cancer due to its association with multiple dysfunctions in tumor cells. Inappropriate function of this machinery can generate tumor-driving splicing variants and trigger oncogenic actions. However, its role in pancreatic neuroendocrine tumors (PanNETs) is poorly defined. In this study we aimed to characterize the expression pattern of a set of splicing machinery components in PanNETs, and their relationship with aggressiveness features. A qPCR-based array was first deployed to determine the expression levels of components of the major (n = 13) and minor spliceosome (n = 4) and associated splicing factors (n = 27), using a microfluidic technology in 20 PanNETs and non-tumoral adjacent samples. Subsequently, in vivo and in vitro models were applied to explore the pathophysiological role of NOVA1. Expression analysis revealed that a substantial proportion of splicing machinery components was altered in tumors. Notably, key splicing factors were overexpressed in PanNETs samples, wherein their levels correlated with clinical and malignancy features. Using in vivo and in vitro assays, we demonstrate that one of those altered factors, NOVA1, is tightly related to cell proliferation, alters pivotal signaling pathways and interferes with responsiveness to drug treatment in PanNETs, suggesting a role for this factor in the aggressiveness of these tumors and its suitability as therapeutic target. Altogether, our results unveil a severe alteration of the splicing machinery in PanNETs and identify the putative relevance of NOVA1 in tumor development/progression, which could provide novel avenues to develop diagnostic biomarkers and therapeutic tools for this pathology.

Role of the Ghrelin System in Colitis and Hepatitis as Risk Factors for Inflammatory-Related Cancers

It is not known exactly what leads to the development of colorectal cancer (CRC) and hepatocellular carcinoma (HCC), but there are specific risk factors that increase the probability of their occurrence. The unclear pathogenesis, too-late diagnosis, poor prognosis as a result of high recurrence and metastasis rates, and repeatedly ineffective therapy of both cancers continue to challenge both basic science and practical medicine. The ghrelin system, which is comprised of ghrelin and alternative peptides (e.g., obestatin), growth hormone secretagogue receptors (GHS-Rs), and ghrelin-O-acyl-transferase (GOAT), plays an important role in the physiology and pathology of the gastrointestinal (GI) tract. It promotes various physiological effects, including energy metabolism and amelioration of inflammation. The ghrelin system plays a role in the pathogenesis of inflammatory bowel diseases (IBDs), which are well known risk factors for the development of CRC, as well as inflammatory liver diseases which can trigger the development of HCC. Colitis-associated cancer serves as a prototype of inflammation-associated cancers. Little is known about the role of the ghrelin system in the mechanisms of transformation of chronic inflammation to low- and high-grade dysplasia, and, finally, to CRC. HCC is also associated with chronic inflammation and fibrosis arising from different etiologies, including alcoholic and nonalcoholic fatty liver diseases (NAFLD), and/or hepatitis B (HBV) and hepatitis C virus (HCV) infections. However, the exact role of ghrelin in the progression of the chronic inflammatory lesions into HCC is still unknown. The aim of this review is to summarize findings on the role of the ghrelin system in inflammatory bowel and liver diseases in order to better understand the impact of this system on the development of inflammatory-related cancers, namely CRC and HCC.

Dysregulation of splicing variants and spliceosome components in breast cancer

The dysregulation of the splicing process has emerged as a novel hallmark of metabolic and tumor pathologies. In breast cancer (BCa), which represents the most diagnosed cancer type among women worldwide, the generation and/or dysregulation of several oncogenic splicing variants have been described. This is the case of the splicing variants of HER2, ER, BRCA1, or the recently identified by our group, In1-ghrelin and SST5TMD4, which exhibit oncogenic roles, increasing the malignancy, poor prognosis, and resistance to treatment of BCa. This altered expression of oncogenic splicing variants has been closely linked with the dysregulation of the elements belonging to the macromolecular machinery that controls the splicing process (spliceosome components and the associated splicing factors). In this review, we compile the current knowledge demonstrating the altered expression of splicing variants and spliceosomal components in BCa, showing the existence of a growing body of evidence supporting the close implication of the alteration in the splicing process in mammary tumorigenesis.

Multiple roles of ghrelin in breast cancer

Breast cancer is one of the most threatening malignant tumors in women worldwide; hence, investigators are continually performing novel research in this field. However, an accurate prediction of its prognosis and postoperative recovery remains difficult. The severity of breast cancer is patient-specific and affected by several health factors; thus, unknown mechanisms may affect its progression. This article analyzes existing literature on breast cancer, ranging from the discovery of ghrelin to its present use, and aims to provide a reference for future research into breast cancer mechanisms and treatment-plan improvement. Various parts of ghrelin have been associated with breast cancer by direct or indirect evidence. The ghrelin system may encompass the direction of expanding breast cancer treatment methods and prognostic indicators. Therefore, we compiled almost all studies on the relationship between the ghrelin system and breast cancer, including unacylated ghrelin, its GHRL gene, ghrelin O-acyltransferase, the receptor growth hormone secretagogue receptor, and several splice variants of ghrelin to lay the foundation for future research.

Role of the Ghrelin System in Colorectal Cancer

The ghrelin system contains several components (e.g., ghrelin with growing number of alternative peptides, growth hormone secretagogue receptors (GHS-Rs), and ghrelin-O-acyl-transferase (GOAT) and participates in regulation of a number of key processes of gastrointestinal (GI) tract cancer progression, including cell proliferation, migration, invasion, apoptosis, inflammation, and angiogenesis. However, its exact role in promoting or inhibiting cancer progression is still unclear. Colorectal cancer (CRC) is one of the most common human malignancies worldwide. Molecular studies suggest an autocrine/paracrine mechanism for the secretion of ghrelin in colorectal carcinogenesis and its contribution to its initial stages. However, the signalling pathways of CRC development involving the ghrelin system are poorly understood. Potential mechanisms of colon carcinogenesis involving components of the ghrelin system were previously described in an animal model and in in vitro studies. However, the diagnostic–prognostic role of serum ghrelin concentrations, tissue expression, or genetic changes of this system in various stages of CRC progression remains an open case. Thus, the aim of this study is to discuss the role of the ghrelin system in colon carcinogenesis, diagnostics and CRC prognostics, as well as the results of studies on the use of ghrelin and its analogues in the therapy of CRC-related syndromes (e.g., cachexia and sarcopenia).

Ghrelin and Cancer: Examining the Roles of the Ghrelin Axis in Tumor Growth and Progression

Ghrelin, a hormone produced and secreted from the stomach, is prim arily known as an appetite stimulant. Recently, it has emerged as a potential regulator/biomarker of cancer progression. Inconsistent results on this subject make this body of literature difficult to interpret. Here, we attempt to identify commonalities in the relationships between ghrelin and various cancers, and summarize important considerations for future research. The main players in the ghrelin family axis are unacylated ghrelin (UAG), acylated ghrelin (AG), the enzyme ghrelin O-acyltransferase (GOAT), and the growth hormone secretagogue receptor (GHSR). GOAT is responsible for the acylation of ghrelin, after which ghrelin can bind to the functional ghrelin receptor GHSR-1a to initiate the activation cascade. Splice variants of ghrelin also exist, with the most prominent being In1-ghrelin. In this review, we focus primarily on the potential of In1-ghrelin as a biomarker for cancer progression, the unique characteristics of UAG and AG, the importance of the two known receptor variants GHSR-1a and 1b, as well as the possible mechanisms through which the ghrelin axis acts. Further understanding of the role of the ghrelin axis in tumor cell proliferation could lead to the development of novel therapeutic approaches for various cancers.

Sarcopenia and Ghrelin System in the Clinical Outcome and Prognosis of Gastroenteropancreatic Neuroendocrine Neoplasms

Simple Summary

Malnutrition and sarcopenia affect clinical outcomes in cancer patients. Nutritional evaluation in patients with neuroendocrine neoplasms (NENs) is not routinely performed. Currently, the evaluation of sarcopenia using CT scans is the gold standard in cancer patients, additionally, anthropometric, biochemical and molecular analysis of patients with gastroenteropancreatic NENs at diagnosis was perfomed. The expression levels of key ghrelin system components were assessed in 63 tumor samples. Results: Nutritional parameters were similar in GEP-NEN tumors of different origin. Relapsed disease was associated with decreased BMI. Patients who presented with weight loss at diagnosis had significantly lower overall survival (108 (25–302) vs. 263 (79–136) months). Ghrelin O-acyltransferase (GOAT) enzyme expression was higher in these patients. The prevalence of sarcopenia using CT images reached 87.2%. Mortality was observed only in patients with sarcopenia. Muscle evaluation was correlated with biochemical parameters but not with the expression of ghrelin system components. Conclusion: Survival is related to the nutritional status of patients with GEP-NENs and also to the molecular expression of some relevant ghrelin system components. Routine nutritional evaluation should be performed in these patients, in order to prescribe appropriate nutritional support, when necessary, for increasing quality of life and improving clinical outcomes.

Abstract

Background: Malnutrition and sarcopenia affect clinical outcomes and treatment response in cancer patients. Patients with neuroendocrine neoplasms (NENs) may present with additional symptoms related to tumor localization in the gastrointestinal tract and hormone secretion, increasing the risk and effects of sarcopenia. Aim: To explore the presence of malnutrition and sarcopenia in gastroenteropancreatic (GEP)-NEN patients, their relation to tumor characteristics, patient outcomes, survival and the molecular expression of ghrelin system components in the tumor. Patients and methods: One-hundred-and-four patients were included. Anthropometric, biochemical and CT-scans at diagnosis were evaluated. The expression levels of key ghrelin system components were assessed in 63 tumor samples. Results: Nutritional parameters were similar in GEP-NEN tumors of different origin. Relapsed disease was associated with decreased BMI. Patients who presented with weight loss at diagnosis had significantly lower overall survival (108 (25–302) vs. 263 (79–136) months). Ghrelin O-acyltransferase (GOAT) enzyme expression was higher in these patients. The prevalence of sarcopenia using CT images reached 87.2%. Mortality was observed only in patients with sarcopenia. Muscle evaluation was correlated with biochemical parameters but not with the expression of ghrelin system components. Conclusion: Survival is related to the nutritional status of patients with GEP-NENs and also to the molecular expression of some relevant ghrelin system components. Routine nutritional evaluation should be performed in these patients, in order to prescribe appropriate nutritional support, when necessary, for increasing quality of life and improving clinical outcomes.

In1-Ghrelin Splicing Variant as a Key Element in the Pathophysiological Association Between Obesity and Prostate Cancer

CONTEXT

Recent studies emphasize the importance of considering the metabolic status to develop personalized medicine approaches. This is especially relevant in prostate cancer (PCa), wherein the diagnostic capability of prostate-specific antigen (PSA) dramatically drops when considering patients with PSA levels ranging from 3 to 10 ng/mL, the so-called grey zone. Hence, additional noninvasive diagnostic and/or prognostic PCa biomarkers are urgently needed, especially in the metabolic-status context.

OBJECTIVE

To assess the potential relation of urine In1-ghrelin (a ghrelin-splicing variant) levels with metabolic-related/pathological conditions (eg, obesity, diabetes, body mass index, insulin and glucose levels) and to define its potential clinical value in PCa (diagnostic/prognostic capacity) and relationship with PCa risk in patients with PSA in the grey zone.

METHODS

Urine In1-ghrelin levels were measured by radioimmunoassay in a clinically, metabolically, pathologically well-characterized cohort of patients without (n = 397) and with (n = 213) PCa with PSA in the grey zone.

RESULTS

Key obesity-related factors associated with PCa risk (BMI, diabetes, glucose and insulin levels) were strongly correlated to In1-ghrelin levels. Importantly, In1-ghrelin levels were higher in PCa patients compared to control patients with suspect of PCa but negative biopsy). Moreover, high In1-ghrelin levels were associated with increased PCa risk and linked to PCa aggressiveness (eg, tumor stage, lymphovascular invasion). In1-ghrelin levels added significant diagnostic value to a clinical model consisting of age, suspicious digital rectal exam, previous biopsy, and PSA levels. Furthermore, a multivariate model consisting of clinical and metabolic variables, including In1-ghrelin levels, showed high specificity and sensitivity to diagnose PCa (area under the receiver operating characteristic curve = 0.740).

CONCLUSIONS

Urine In1-ghrelin levels are associated with obesity-related factors and PCa risk and aggressiveness and could represent a novel and valuable noninvasive PCa biomarker, as well as a potential link in the pathophysiological relationship between obesity and PCa.

GHSR methylation-dependent expression of a variant ligand and receptor of the ghrelin system induces thymoma tumorigenesis

Our previous study reported that the DNA methylation of growth hormone secretagogue receptor (GHSR) was significantly higher in thymoma or thymic carcinoma (TC) than in normal thymic tissue samples. Thymic epithelial tumors (TETs) with higher GHSR DNA methylation were associated with significantly worse prognosis than those with lower levels of DNA methylation. Diversified components of the ghrelin-GHSR axis may exert opposing effects in cancer progression, depending on the cancer type in question. However, the precise function of the axis remains unclear. In the present study, the mRNA expression of five key components of the ghrelin system [native ligand ghrelin, variant ligand In-1 ghrelin, native receptor GHSR1a, variant receptor GHSR1b and acylation enzyme ghrelin O-acyltransferase (GOAT)] were examined in 58 TET samples by reverse transcription-quantitative PCR, and protein expression of GHSR1a and GHSR1b was assessed in 20 TETs using immunohistochemistry. The results revealed that In-1 ghrelin, GHSR1b (variant forms) and GOAT were more strongly expressed in thymoma compared with thymic-adjacent tissue. By contrast, no significant differences were observed in the expression of ghrelin and GHSR1a (native forms) between thymoma and thymic tissue. The mRNA expression of In-1 ghrelin and GHSR1b (variant forms) was positively associated with GHSR methylation in thymoma tissue samples. However, a relationship was not found between ghrelin, GHSR1a or GOAT expression (native forms) and GHSR methylation in thymoma. Immunohistochemical analysis revealed that mRNA expression of GHSR1a and GHSR1b generally correlated with expression of the corresponding protein, and that the expression of GHSR1b was increased in advanced-stage TETs. These results indicate that the DNA methylation of GHSR is associated with a shift from native expression (ghrelin and GHSR1a) to variant expression (In-1 ghrelin and GHSR1b), which induces the tumorigenesis of thymoma, but not TC.

GIST and Ghrelin: To Be or Not to Be?

BACKGROUND

Ghrelin is the orexigenic hormone secreted mainly by the stomach. Its involvement in neoplastic development has been studied in gastrointestinal adenocarcinomas. Our paper aims to evaluate the influence of the ghrelin axis in gastrointestinal stromal tumors (GISTs).

MATERIALS AND METHODS

The study design included two groups of patients, 46 with gastric GISTs and 30 with obesity. Archived tissue samples were evaluated for the presence of gastritis and H. pylori. Immunohistochemical expression of ghrelin and its receptor (GHS-R) was assessed.

RESULTS

All GISTs showed absent immunohistochemical expression for ghrelin, while GHS-R displayed a particular pattern, with notable differences in intensity (p = 0.0256) and percentage of stained cells (p < 0.00001) in the periphery vs. core of tumors. Positive ghrelin expression was lower in the gastric mucosa of the first group compared to the second group (p < 0.001).

CONCLUSION

The ghrelin axis can influence GISTs carcinogenesis through activation of GHS-R. A previously described direct autocrine/paracrine mechanism is not supported by our findings.

Ghrelin and its role in gastrointestinal tract tumors (Review)

Ghrelin, an orexigenic hormone, is a peptide that binds to the growth hormone secretagogue receptor; it is secreted mainly by enteroendocrine cells in the oxyntic glands of the stomach. Ghrelin serves a role in both local and systemic physiological processes, and is implicated in various pathologies, including neoplasia, with tissue expression in several types of malignancies in both in vitro and in vivo studies. However, the precise implications of the ghrelin axis in metastasis, invasion and cancer progression regulation has yet to be established. In the case of gastrointestinal (GI) tract malignancies, ghrelin has shown potential to become a prognostic factor or even a therapeutic target, although data in the literature are inconsistent and unsystematic, with reports untailored to a specific histological subtype of cancer or a particular localization. The evaluation of immunohistochemical expression shows a limited outlook owing to the low number of cases analyzed, and in vivo analyses have conflicting data regarding differences in ghrelin serum levels in patients with cancer. The aim of this review was to examine the relationship between ghrelin and GI tract malignancies to demonstrate the inconsistencies in current results and to highlight its clinical significance in the outcome of these patients.

Appetite-regulating hormones-leptin, adiponectin and ghrelin-and the development of prostate cancer: a systematic review and exploratory meta-analysis

BACKGROUND

Obesity has been proposed as a risk factor for prostate cancer (PCa). In obesity, serum levels of the appetite-regulating hormones-leptin, adiponectin, and ghrelin-become deregulated.

OBJECTIVE

To explore whether serum levels of appetite-regulating hormones associate with the incidence of PCa, the incidence of advanced disease, or PCa-specific mortality.

METHODS

PRISMA guidelines were followed. A systematic search for relevant articles published until March 2019 was performed using the databases PubMed, EMBASE, and Web of Science. Observational studies with data on serum levels of leptin, adiponectin, or ghrelin and PCa outcome were included. Meta-analysis was used to combine risk estimates. Meta-relative risks (mRRs) were calculated using random effects models. When available, raw data was pooled. Publication bias was assessed by funnel plot and Begg's test.

RESULTS

Thirty-five studies were eligible for inclusion. The qualitative analysis indicated that leptin was not consistently associated with any PCa outcome, although several cohorts reported decreased adiponectin levels in men who later developed advanced PCa. Based on the meta-analysis, there was no significant effect of leptin on PCa incidence (mRR = 0.93 (95% CI 0.75-1.16), p = 0.52) or advanced PCa (mRR = 0.90 (95% CI 0.74-1.10), p = 0.30). There were insufficient studies to estimate the mRR of PCa incidence for men with the highest levels of adiponectin. The combined risk of advanced PCa for men with the highest levels of adiponectin was reduced but did not reach significance (mRR = 0.81 (95% CI 0.61-1.08), p = 0.15).

CONCLUSIONS

The current evidence does not suggest an association between leptin and PCa outcome. However, there may be an inverse association between adiponectin and the incidence of advanced PCa that should be investigated by further studies. Serum ghrelin has not been largely investigated.

Splicing Machinery is Dysregulated in Pituitary Neuroendocrine Tumors and is Associated with Aggressiveness Features

Pituitary neuroendocrine tumors (PitNETs) constitute approximately 15% of all brain tumors, and most have a sporadic origin. Recent studies suggest that altered alternative splicing and, consequently, appearance of aberrant splicing variants, is a common feature of most tumor pathologies. Moreover, spliceosome is considered an attractive therapeutic target in tumor pathologies, and the inhibition of SF3B1 (e.g., using pladienolide-B) has been shown to exert antitumor effects. Therefore, we aimed to analyze the expression levels of selected splicing-machinery components in 261 PitNETs (somatotropinomas/non-functioning PitNETS/corticotropinomas/prolactinomas) and evaluated the direct effects of pladienolide-B in cell proliferation/viability/hormone secretion in human PitNETs cell cultures and pituitary cell lines (AtT-20/GH3). Results revealed a severe dysregulation of splicing-machinery components in all the PitNET subtypes compared to normal pituitaries and a unique fingerprint of splicing-machinery components that accurately discriminate between normal and tumor tissue in each PitNET subtype. Moreover, expression of specific components was associated with key clinical parameters. Interestingly, certain components were commonly dysregulated throughout all PitNET subtypes. Finally, pladienolide-B reduced cell proliferation/viability/hormone secretion in PitNET cell cultures and cell lines. Altogether, our data demonstrate a drastic dysregulation of the splicing-machinery in PitNETs that might be associated to their tumorigenesis, paving the way to explore the use of specific splicing-machinery components as novel diagnostic/prognostic and therapeutic targets in PitNETs.

Peptides derived from the extracellular domain of the somatostatin receptor splicing variant SST5TMD4 increase malignancy in multiple cancer cell types

Extracellular fragments derived from plasma membrane receptors can play relevant roles in the development/progression of tumor pathologies, thereby offering novel diagnostic or therapeutic opportunities. The truncated variant of somatostatin receptor subtype-5, SST5TMD4, is an aberrantly spliced receptor with 4 transmembrane domains, highly overexpressed in several tumor types, whose C-terminal tail is exposed towards the extracellular matrix, and could therefore be the substrate for proteolytic enzymes. In silico analysis implemented herein predicted 2 possible cleavage sites for metalloproteases MMP2, 9, 14, and 16 in its sequence, which could generate 3 releasable peptides. Of note, expression of those MMPs was directly correlated with SST5TMD4 in several cancer-derived cell lines (ie neuroendocrine tumors and prostate, breast, and liver cancers). Moreover, incubation with SST5TMD4-derived peptides enhanced malignancy features in all cancer cell types tested (ie proliferation, migration, etc.) and blunted the antiproliferative response to somatostatin in QGP-1 cells, acting probably through PI3K/AKT and/or MEK/ERK signaling pathways and the modulation of key cancer-associated genes (eg MMPs, MKI67, ACTR2/3, CD24/44). These results suggest that SST5TMD4-derived peptides could contribute to the strong oncogenic role of SST5TMD4 observed in multiple tumor pathologies, and, therefore, represent potential candidates to identify novel diagnostic, prognostic, or therapeutic targets in cancer.

Type 2 Diabetes in Neuroendocrine Tumors: Are Biguanides and Statins Part of the Solution?

CONTEXT

Biguanides and statins exert beneficial effects on various cancer types. Their precise effects and underlying molecular mechanisms are poorly understood.

MATERIALS AND METHODS

We analyzed the relationship between metabolic syndrome and histological, epidemiological, and prognosis variables in two cohorts of patients with neuroendocrine tumors (NETs): those with lung carcinoids (LCs; n = 81) and those with gastroenteropancreatic NET (GEP-NET; n = 100). Biguanide and statin antitumor effects were investigated by evaluating proliferation, migration, secretion, gene expression, and involved molecular pathways in BON1/QGP1 cell cultures.

RESULTS

Pleura invasion was higher (LCs group; P < 0.05) and tumor diameter tended to be increased (GEP-NET group) in patients with type 2 diabetes (T2DM) than in those without. Somatostatin and ghrelin systems mRNA levels differed in tumor tissue of patients with T2DM taking metformin or not. Biguanides decreased proliferation rate in BON1/QGP1 cells; the effects of statins on proliferation rate depended on the statin and cell types, and time. Specifically, only simvastatin and atorvastatin decreased proliferation in BON1 cells, whereas all statins decreased proliferation rate in QGP1 cells. Metformin and simvastatin decreased migration capacity in BON1 cells; biguanides decreased serotonin secretion in BON1 cells. Phenformin increased apoptosis in BON1/QGP1 cells; simvastatin increased apoptosis in QGP1 cells. These antitumor effects likely involved altered expression of key genes related to cancer aggressiveness.

CONCLUSION

A clear inhibitory effect of biguanides and statins was seen on NET-cell aggressiveness. Our results invite additional exploration of the potential therapeutic role of these drugs in treatment of patients with NETs.

Ghrelin-O-Acyltransferase (GOAT) Enzyme as a Novel Potential Biomarker in Gastroenteropancreatic Neuroendocrine Tumors

OBJECTIVES

The association between the presence and alterations of the components of the ghrelin system and the development and progression of neuroendocrine tumors (NETs) is still controversial and remains unclear.

METHODS

Here, we systematically evaluated the expression levels (by quantitative-PCR) of key ghrelin system components of in gastroenteropancreatic (GEP)-NETs, as compared to non-tumor adjacent (NTA; n = 42) and normal tissues (NT; n = 14). Then, we analyzed their putative associations with clinical-histological characteristics.

RESULTS

The results indicate that ghrelin and its receptor GHSR1a are present in a high proportion of normal tissues, while the enzyme ghrelin-O-acyltransferase (GOAT) and the splicing variants In1-ghrelin and GHSR1b were present in a lower proportion of normal tissues. In contrast, all ghrelin system components were present in a high proportion of tumor and NTA tissues. GOAT was significantly overexpressed (by quantitative-PCR (qPCR)) in tumor samples compared to NTA, while a trend was found for ghrelin, In1-ghrelin and GHSR1a. In addition, expression of these components displayed significant correlations with key clinical parameters. The marked overexpression of GOAT in tumor samples compared to NTA regions was confirmed by IHC, revealing that this enzyme is particularly overexpressed in gastrointestinal NETs, where it is directly correlated with tumor diameter.

CONCLUSIONS

These results provide novel information on the presence and potential pathophysiological implications of the ghrelin system components in GEP-NETs, wherein GOAT might represent a novel diagnostic biomarker.

Multilayered heterogeneity as an intrinsic hallmark of neuroendocrine tumors

Neuroendocrine tumors (NETs) comprise a complex and highly heterogeneous group of neoplasms that can arise all over the body, originating from neuroendocrine cells. NETs are characterized by a general lack of symptoms until they are in advanced phase, and early biomarkers are not as available and useful as required. Heterogeneity is an intrinsic, pivotal feature of NETs that derives from diverse causes and ultimately shapes tumor fate. The different layers that conform NET heterogeneity include a wide range of distinct characteristics, from the mere location of the tumor to its clinical and functional features, and from its cellular properties, to the core signaling and (epi)genetic components defining the molecular signature of the tumor. The importance of this heterogeneity resides in that it translates into a high variability among tumors and, hence, patients, which hinders a more precise diagnosis and prognosis and more efficacious treatment of these diseases. In this review, we highlight the significance of this heterogeneity as an intrinsic hallmark of NETs, its repercussion on clinical approaches and tumor management, and some of the possible factors associated to such heterogeneity, including epigenetic and genetic elements, post-transcriptional regulation, or splicing alterations. Notwithstanding, heterogeneity can also represent a valuable and actionable feature, towards improving medical approaches based on personalized medicine. We conclude that NETs can no longer be viewed as a single disease entity and that their diagnosis, prognosis and treatment must reflect and incorporate this heterogeneity.

In1-ghrelin splicing variant is associated with reduced disease-free survival of breast cancer patients and increases malignancy of breast cancer cells lines

Ghrelin gene generates several variants that regulate multiple pathophysiological functions, including tumor-related processes. In1-ghrelin is a splicing variant that was previously shown to be overexpressed in breast cancer (BCa), where it correlated with proliferation markers; however, its possible association with clinical outcome of BCa patients and underlying mechanisms are still unknown. To address this issue, expression levels and clinical associations of In1-ghrelin were analyzed in a cohort of 117 BCa samples. Additionally, a battery of cellular and molecular assays was implemented using two BCa cell lines (MCF-7 and MDA-MB-231), wherein the role of In1-ghrelin on proliferation, migration, dedifferentiation and signaling pathways was explored. The results generated revealed that high expression of In1-ghrelin in BCa samples was associated with lymph node metastasis and reduced disease-free survival. Indeed, In1-ghrelin overexpression stimulated proliferation and migration in MCF-7 and MDA-MB-231 cells. Similar results were found by treating MDA-MB-231 and MCF-7 with In1-ghrelin-derived peptides. Conversely, In1-ghrelin silencing decreased proliferation and migration capacities of MDA-MB-231. Furthermore, In1-ghrelin (but not ghrelin) overexpression increased the capacity to form mammospheres in both cell lines. These effects could be associated with activation of MAPK-ERK, Jag1/Notch, Wnt/β-catenin and/or TGF-β1 pathways. Altogether, our data indicate that In1-ghrelin could play relevant functional roles in the regulation of BCa development and progression and may provide insights to identify novel biomarkers and new therapeutic approaches for this pathology.

Clinical and functional implication of the components of somatostatin system in gastroenteropancreatic neuroendocrine tumors

PURPOSE

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) comprise a heterogeneous group of malignancies often presenting with metastasis at diagnosis and whose clinical outcome is difficult to predict. Somatostatin (SST) analogs (SSAs) provide a valuable pharmacological tool to palliate hormonal symptoms, and control progression in some NETs. However, many patients do not respond to SSAs or develop resistance, and there are many uncertainties regarding pathophysiology of SST and its receptors (sst1-sst5) in GEP-NETs.

METHODS

The expression of SST system components in GEP-NETs was determined, compared with that of non-tumor adjacent and normal tissues and correlated with clinical and histological characteristics. Specifically, 58 patients with GEP-NETs and 14 normal samples were included. Cell viability in NET cell lines was determined in response to specific SSAs.

RESULTS

Normal samples and non-tumor adjacent tissues presented a similar expression profile, with appreciable expression of sst2 and sst3, and a lower expression of the other receptors. In contrast, cortistatin, sst1, sst4, and sst5 were overexpressed in tumors, while sst3 and sst4 seemed overexpressed in less differentiated tumors. Some SST system components were related to vascular/nerve invasion and metastasis. In vitro, sst1 and sst3 agonists reduced viability in BON-1 cells, while they, similar to octreotide and pasireotide, increased viability in QGP-1 cells.

CONCLUSIONS

These results provide novel information on SST system pathophysiology in GEP-NETs, including relevant associations with clinical-histological parameters, which might help to better understand the intrinsic heterogeneity of NETs and to identify novel biomarkers and/or targets with potential prognostic and/or therapeutic value for GEP-NETs patients.

Somatostatin receptor subtype 1 as a potential diagnostic marker and therapeutic target in prostate cancer

BACKGROUND

Prostate cancer (PCa) is a highly prevalent neoplasia that is strongly influenced by the endocrine system. Somatostatin (SST) and its five receptors (sst1-5 encoded by SSTR1-5 genes) comprise a pleiotropic system present in most endocrine-related cancers, some of which are successfully treated with SST analogs. Interestingly, it has been reported that SSTR1 is overexpressed in PCa, but its regulation, functional role, and clinical implications are still poorly known.

METHODS

PCa specimens (n = 52) from biopsies and control prostates from cystoprostatectomies (n = 12), as well as in silico databases were used to evaluate SSTR1 and miRNAs expression. In vitro studies in 22Rv1 PCa cells were implemented to explore the regulation of SSTR1/sst1 by different miRNAs, and to evaluate the consequences of SSTR1/sst1 overexpression, silencing and/or activation [with the specific BIM-23926 sst1 agonist (IPSEN)] on cell-proliferation, migration, signaling-pathways, and androgen-signaling.

RESULTS

We found that SSTR1 is overexpressed in multiple cohorts of PCa samples, as compared with normal prostate tissues, wherein it correlates with androgen receptor (AR) expression, and appears to be associated with aggressiveness (metastasis). Furthermore, our data revealed that SSTR1/sst1 expression might be regulated by specific miRNAs in PCa, including miR-24, which is downregulated in PCa samples and correlates inversely with SSTR1 expression. In vitro studies indicated that treatment with the BIM-23926 sst1 agonist, as well as SSTR1 overexpression, decreased, whereas SSTR1 silencing increased, cell-proliferation in 22Rv1 cells, likely through the regulation of PI3K/AKT-CCND3 signaling-pathway. Importantly, sst1 action was also able to modulate androgen/AR activity, and reduced PSA secretion from PCa cell lines.

CONCLUSIONS

Altogether, our results indicate that SSTR1 is overexpressed in PCa, where it can exert a relevant pathophysiological role by decreasing cell-proliferation and PSA secretion. Therefore, sst1, possibly in combination with miR-24, could be used as a novel tool to explore therapeutic targets in PCa.

The oncogenic role of the In1-ghrelin splicing variant in prostate cancer aggressiveness

Background

The Ghrelin-system is a complex, pleiotropic family composed of several peptides, including native-ghrelin and its In1-ghrelin splicing variant, and receptors (GHSR 1a/b), which are dysregulated in various endocrine-related tumors, where they associate to pathophysiological features, but the presence, functional role, and mechanisms of actions of In1-ghrelin splicing variant in prostate-cancer (PCa), is completely unexplored. Herein, we aimed to determine the presence of key ghrelin-system components (native-ghrelin, In1-ghrelin, GHSR1a/1b) and their potential pathophysiological role in prostate cancer (PCa).

Methods

In1-ghrelin and native-ghrelin expression was evaluated by qPCR in prostate tissues from patients with high PCa-risk (n = 52; fresh-tumoral biopsies), and healthy-prostates (n = 12; from cystoprostatectomies) and correlated with clinical parameters using Spearman-test. In addition, In1-ghrelin and native-ghrelin was measured in plasma from an additional cohort of PCa-patients with different risk levels (n = 30) and control-healthy patients (n = 20). In vivo functional (proliferation/migration) and mechanistic (gene expression/signaling-pathways) assays were performed in PCa-cell lines in response to In1-ghrelin and native-ghrelin treatment, overexpression and/or silencing. Finally, tumor progression was monitored in nude-mice injected with PCa-cells overexpressing In1-ghrelin, native-ghrelin and empty vector (control).

Results

In1-ghrelin, but not native-ghrelin, was overexpressed in high-risk PCa-samples compared to normal-prostate (NP), and this expression correlated with that of PSA. Conversely, GHSR1a/1b expression was virtually absent. Remarkably, plasmatic In1-ghrelin, but not native-ghrelin, levels were also higher in PCa-patients compared to healthy-controls. Furthermore, In1-ghrelin treatment/overexpression, and to a much lesser extent native-ghrelin, increased aggressiveness features (cell-proliferation, migration and PSA secretion) of NP and PCa cells. Consistently, nude-mice injected with PC-3-cells stably-transfected with In1-ghrelin, but not native-ghrelin, presented larger tumors. These effects were likely mediated by ERK1/2-signaling activation and involved altered expression of key oncogenes/tumor suppressor genes. Finally, In1-ghrelin silencing reduced cell-proliferation and PSA secretion from PCa cells.

Conclusions

Altogether, our results indicate that In1-ghrelin levels (in tissue) and circulating levels (in plasma) are increased in PCa where it can regulate key pathophysiological processes, thus suggesting that In1-ghrelin may represent a novel biomarker and a new therapeutic target in PCa.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0713-9) contains supplementary material, which is available to authorized users.

The components of somatostatin and ghrelin systems are altered in neuroendocrine lung carcinoids and associated to clinical-histological features

BACKGROUND

Lung carcinoids (LCs) are rare tumors that comprise 1-5% of lung malignancies but represent 20-30% of neuroendocrine tumors. Their incidence is progressively increasing and a better characterization of these tumors is required. Alterations in somatostatin (SST)/cortistatin (CORT) and ghrelin systems have been associated to development/progression of various endocrine-related cancers, wherein they may become useful diagnostic, prognostic and therapeutic biomarkers.

OBJECTIVES

We aimed to evaluate the expression levels of ghrelin and SST/CORT system components in LCs, as well as to explore their putative relationship with histological/clinical characteristics.

PATIENTS AND METHODS

An observational retrospective study was performed; 75 LC patients with clinical/histological characteristics were included. Samples from 46 patients were processed to isolate mRNA from tumor and adjacent non-tumor region, and the expression levels of SST/CORT and ghrelin systems components, determined by quantitative-PCR, were compared to those of 7 normal lung tissues.

RESULTS

Patient cohort was characterized by mean age 53±15 years, 48% males, 34% with tobacco exposure; 71.4/28.6% typical/atypical carcinoids, 21.7% incidental tumors, 4.3% functioning tumors, 17.7% with metastasis. SST/CORT and ghrelin system components were expressed at variable levels in a high proportion of tumors, as well as in adjacent non-tumor tissues, while a lower proportion of normal lung samples also expressed these molecules. A gradation was observed from normal non-neoplastic lung tissues, non-tumor adjacent tissue and LCs, being SST, sst4, sst5, GHS-R1a and GHS-R1b overexpressed in tumor tissue compared to normal tissue. Importantly, several SST/CORT and ghrelin system components displayed significant correlations with relevant clinical parameters, such as necrosis, peritumoral and vascular invasion, or metastasis.

CONCLUSION

Altogether, these data reveal a prominent, widespread expression of key SST/CORT/ghrelin system components in LCs, where they display clinical-histological correlations, which could provide novel, valuable markers for NET patient management.

Metformin Reduces Prostate Tumor Growth, in a Diet-Dependent Manner, by Modulating Multiple Signaling Pathways

Prostate-cancer is strongly influenced by obesity, wherein metformin could represent a promising treatment; however, the endocrine metabolic/cellular/molecular mechanisms underlying these associations and effects are still unclear. To determine the beneficial antitumoral effects of metformin on prostate cancer progression/aggressiveness and the relative contribution of high-fat diet (HFD; independently of obesity), we used HFD-fed immunosuppressed mice inoculated with PC3 cells (which exhibited partial resistance to diet-induced obesity) compared with low-fat diet (LFD)-fed control mice. Moreover, gene expression analysis was performed on cancer-associated genes in the xenografted tumors, and the antitumorigenic role of metformin on tumoral (PC3/22Rv1/LNCaP) and normal (RWPE1) prostate cells was evaluated. The results demonstrate that HFD is associated with enhanced prostate cancer growth irrespective of body weight gain and endocrine metabolic dysregulations and that metformin can reduce prostate cancer growth under LFD but more prominently under HFD, acting through the modulation of several tumoral-associated processes (e.g., cell cycle, apoptosis, and/or necrosis). Moreover, the actions observed in vivo could be mediated by the modulation of the local expression of GH/IGF1 axis components. Finally, it was demonstrated that metformin had disparate effects on proliferation, migration, and prostate-specific antigen secretion from different cell lines. Altogether, these data reveal that metformin inhibits prostate cancer growth under LFD and, specially, under HFD conditions through multiple metabolic/tumoral signaling pathways.Implications: The current study linking dietary influence on metformin-regulated signaling pathways and antitumoral response provides new and critical insight on environment-host interactions in cancer and therapy. Mol Cancer Res; 15(7); 862-74. ©2017 AACR.

Ghrelin O-acyltransferase (GOAT) enzyme is overexpressed in prostate cancer, and its levels are associated with patient's metabolic status: Potential value as a non-invasive biomarker

Ghrelin-O-acyltransferase (GOAT) is the key enzyme regulating ghrelin activity, and has been proposed as a potential therapeutic target for obesity/diabetes and as a biomarker in some endocrine-related cancers. However, GOAT presence and putative role in prostate-cancer (PCa) is largely unknown. Here, we demonstrate, for the first time, that GOAT is overexpressed (mRNA/protein-level) in prostatic tissues (n = 52) and plasma/urine-samples (n = 85) of PCa-patients, compared with matched controls [healthy prostate tissues (n = 12) and plasma/urine-samples from BMI-matched controls (n = 28), respectively]. Interestingly, GOAT levels in PCa-patients correlated with aggressiveness and metabolic conditions (i.e. diabetes). Actually, GOAT expression was regulated by metabolic inputs (i.e. In1-ghrelin, insulin/IGF-I) in cultured normal prostate cells and PCa-cell lines. Importantly, ROC-curve analysis unveiled a valuable diagnostic potential for GOAT to discriminate PCa at the tissue/plasma/urine-level with high sensitivity/specificity, particularly in non-diabetic individuals. Moreover, we discovered that GOAT is secreted by PCa-cells, and that its levels are higher in urine samples from a stimulated post-massage vs. pre-massage prostate-test. In conclusion, plasmatic GOAT levels exhibit high specificity/sensitivity to predict PCa-presence compared with other PCa-biomarkers, especially in non-diabetic individuals, suggesting that GOAT holds potential as a novel non-invasive PCa-biomarker.

Polymorphisms in MEN1 and DRD2 genes are associated with the occurrence and characteristics of pituitary adenomas

OBJECTIVE

Although pituitary adenomas (PAs) affect a significant proportion of the population, only a fraction have the potential to become clinically relevant during an individual's lifetime, causing hormonal imbalance or complications due to mass effect. The overwhelming majority of cases are sporadic and without a clear familial history, and the genotype-phenotype correlation in PA patients is poorly understood. Our aim was to investigate the involvement of genes known for their role in familial cases on drug response and tumor suppression in the development and pathology of PAs in a patient group from Latvia.

DESIGN

The study included 143 cases and 354 controls, we investigated the role of single-nucleotide polymorphisms (SNPs) in seven genes (SSTR2, SSTR5, DRD2, MEN1, AIP, GNAS, and PRKAR1A) associated with pituitary tumor occurrence, phenotype, and clinical symptoms.

METHODS

Genotyping of 96 tag and nonsynonymous SNPs was performed in the genomic regions of interest.

RESULTS

We discovered a significant association (OR=17.8, CI 0.95=2.18-145.5, P=0.0002) between a rare MEN1 mutation (rs2959656) and clinically active adenoma in our patients. Additionally, rs7131056 at DRD2 was associated with a higher occurrence of extrasellar growth in patients with prolactinoma and somatotropinoma (OR=2.79, CI 0.95=1.58-4.95, P=0.0004).

CONCLUSIONS

rs2959656, a nonsynonymous variant in MEN1, is associated with the development of clinically active PA. Furthermore, rs7131056 in DRD2 contributes to either faster growth of the adenoma or reduced symptomatic presentation, allowing PAs to become larger before detection.