VEGF secretion by neuroendocrine tumor cells is inhibited by octreotide and by inhibitors of the PI3K/AKT/mTOR pathway

Concomitant inhibition of PI3K/mTOR signaling pathways boosts antiproliferative effects of lanreotide in bronchopulmonary neuroendocrine tumor cells

Introduction: Somatostatin analogues (SSAs) are commonly used in the treatment of hormone hypersecretion in neuroendocrine tumors (NETs), however the extent to which they inhibit proliferation is much discussed. Objective: We studied the antiproliferative effects of novel SSA lanreotide in bronchopulmonary NETs (BP-NETs). We focused on assessing whether pretreating cells with inhibitors for phosphatidylinositol 3-kinase (PI3K) and mammalian target for rapamycin (mTOR) could enhance the antiproliferative effects of lanreotide. Methods: BP-NET cell lines NCI-H720 and NCI-H727 were treated with PI3K inhibitor BYL719 (alpelisib), mTOR inhibitor everolimus and SSA lanreotide to determine the effect on NET differentiation markers, cell survival, proliferation and alterations in cancer-associated pathways. NT-3 cells, previously reported to express somatostatin receptors (SSTRs) natively, were used as control for SSTR expression. Results: SSTR2 was upregulated in NCI-H720 and NT-3 cells upon treatment with BYL719. Additionally, combination treatment consisting of BYL719 and everolimus plus lanreotide tested in NCI-H720 and NCI-H727 led to diminished cell proliferation in a dose-dependent manner. Production of proteins activating cell death mechanisms was also induced. Notably, a multiplexed gene expression analysis performed on NCI-H720 revealed that BYL719 plus lanreotide had a stronger effect on the downregulation of mitogens than lanreotide alone. Discussion/Conclusion: We report a widespread analysis of changes in BP-NET cell lines at the genetic/protein expression level in response to combination of lanreotide with pretreatment consisting of BYL719 and everolimus. Interestingly, SSTR expression reinduction could be exploited in therapeutic and diagnostic applications. The overall results of this study support the evaluation of combination-based therapies using lanreotide in preclinical studies to further increase its antiproliferative effect and ultimately facilitate its use in high-grade tumors.

Metastatic Pheochromocytoma and Paraganglioma: Somatostatin Receptor 2 Expression, Genetics, and Therapeutic Responses

CONTEXT

Pheochromocytomas and paragangliomas (PPGLs) with pathogenic mutations in the succinate dehydrogenase subunit B (SDHB) are associated with a high metastatic risk. Somatostatin receptor 2 (SSTR2)-dependent imaging is the most sensitive imaging modality for SDHB-related PPGLs, suggesting that SSTR2 expression is a significant cell surface therapeutic biomarker of such tumors.

OBJECTIVE

Exploration of the relationship between SSTR2 immunoreactivity and SDHB immunoreactivity, mutational status, and clinical behavior of PPGLs. Evaluation of SSTR-based therapies in metastatic PPGLs.

METHODS

Retrospective analysis of a multicenter cohort of PPGLs at 6 specialized Endocrine Tumor Centers in Germany, The Netherlands, and Switzerland. Patients with PPGLs participating in the ENSAT registry were included. Clinical data were extracted from medical records, and immunohistochemistry (IHC) for SDHB and SSTR2 was performed in patients with available tumor tissue. Immunoreactivity of SSTR2 was investigated using Volante scores. The main outcome measure was the association of SSTR2 IHC positivity with genetic and clinical-pathological features of PPGLs.

RESULTS

Of 202 patients with PPGLs, 50% were SSTR2 positive. SSTR2 positivity was significantly associated with SDHB- and SDHx-related PPGLs, with the strongest SSTR2 staining intensity in SDHB-related PPGLs (P = .01). Moreover, SSTR2 expression was significantly associated with metastatic disease independent of SDHB/SDHx mutation status (P < .001). In metastatic PPGLs, the disease control rate with first-line SSTR-based radionuclide therapy was 67% (n = 22, n = 11 SDHx), and with first-line "cold" somatostatin analogs 100% (n = 6, n = 3 SDHx).

CONCLUSION

SSTR2 expression was independently associated with SDHB/SDHx mutations and metastatic disease. We confirm a high disease control rate of somatostatin receptor-based therapies in metastatic PPGLs.

A novel GRK3-HDAC2 regulatory pathway is a key direct link between neuroendocrine differentiation and angiogenesis in prostate cancer progression

The mechanisms underlying the progression of prostate cancer (PCa) to neuroendocrine prostate cancer (NEPC), an aggressive PCa variant, are largely unclear. Two prominent NEPC phenotypes are elevated NE marker expression and heightened angiogenesis. Identifying the still elusive direct molecular links connecting angiogenesis and neuroendocrine differentiation (NED) is crucial for our understanding and targeting of NEPC. Here we found that histone deacetylase 2 (HDAC2), whose role in NEPC has not been reported, is one of the most upregulated epigenetic regulators in NEPC. HDAC2 promotes both NED and angiogenesis. G protein-coupled receptor kinase 3 (GRK3), also upregulated in NEPC, is a critical promoter for both phenotypes too. Of note, GRK3 phosphorylates HDAC2 at S394, which enhances HDAC2's epigenetic repression of potent anti-angiogenic factor Thrombospondin 1 (TSP1) and master NE-repressor RE1 Silencing Transcription Factor (REST). Intriguingly, REST suppresses angiogenesis while TSP1 suppresses NE marker expression in PCa cells, indicative of their novel functions and their synergy in cross-repressing the two phenotypes. Furthermore, the GRK3-HDAC2 pathway is activated by androgen deprivation therapy and hypoxia, both known to promote NED and angiogenesis in PCa. These results indicate that NED and angiogenesis converge on GRK3-enhanced HDAC2 suppression of REST and TSP1, which constitutes a key missing link between two prominent phenotypes of NEPC.

Somatostatin analogues in treatment-refractory meningioma: a systematic review with meta-analysis of individual patient data

Treatment-refractory meningiomas have a dismal prognosis and limited treatment options. Meningiomas express high-densities of somatostatin receptors (SSTR), thus potentially susceptible to antitumorigenic effects of somatostatin analogues (SSA). Evidence for SSA in meningiomas is scarce, and it is unclear if published literature would either (1) support wider use of SSA, if (2) more evidence is desirable, or if (3) available evidence is sufficient to discard SSA. We addressed the need for more evidence with a systematic review and meta-analysis. We performed an individual patient data (IPD) meta-analysis. Main outcomes were toxicity, best radiological response, progression-free survival, and overall survival. We applied multivariable logistic regression models to estimate the effect of SSA on the probability of obtaining radiological disease control. The predictive performance was evaluated using area under the curve and Brier scores. We included 16 studies and compiled IPD from 8/9 of all previous cohorts. Quality of evidence was overall ranked "very low." Stable disease was reported in 58% of patients as best radiological response. Per 100 mg increase in total SSA dosage, the odds ratios for obtaining radiological disease control was 1.42 (1.11 to 1.81, P = 0.005) and 1.44 (1.00 to 2.08, P = 0.05) for patients treated with SSA as monodrug therapy vs SSA in combination with everolimus, respectively. Low quality of evidence impeded exact quantification of treatment efficacy, and the association between response and treatment may represent reverse causality. Yet, the SSA treatment was well tolerated, and beneficial effect cannot be disqualified. A prospective trial without bias from inconsistent study designs is warranted to assess SSA therapy for well-defined meningioma subgroups.

Myeloid ecotropic viral integration site-1 inhibition promotes apoptosis, suppresses proliferation of acute myeloid leukemia cells, accentuates the effects of anticancer drugs

To investigate the effects of myeloid ecotropic viral integration site-1 (MEIS1) on the proliferation and apoptosis of acute myeloid leukemia (AML) cells and the anticancer effects of the drug, we screened Kasumi-6, KG-1, and Kasumi-1 cells using quantitative reverse transcription polymerase chain reaction. Kasumi-6 and Kasumi-1 cells were subjected to human antigen R (HuR)-mediated interference (IV). Hexokinase 2 (HK2) expression and phosphorylation of protein kinase B (p-AKT) and mammalian target of rapamycin (p-mTOR) were observed with Western blotting. Cell proliferation was assessed using Cell Counting Kit-8, apoptosis was examined using Hoechst 33,258 staining, and glucose uptake was detected with a colorimetric biochemical assay kit. We found that, among the three cell lines tested, MEIS1 expression was highest in Kasumi-1 cells, which were therefore selected for subsequent experiments. Kasumi-1 cells receiving IV showed significantly decreased proliferation (p < 0.05) and increased apoptosis compared to the control group. Compared with the controls, IV significantly increased the expression of HK2, p-AKT, p-mTOR, multidrug resistance-associated protein 1 and P-glycoprotein (P < 0.05), but decreased glucose uptake. Treatment with adriamycin, daunorubicin and imatinib resulted in a progressive increase in inhibition of cell proliferation, with the IV group showing the highest inhibition rate among the three groups (P < 0.05). Thus, inhibition of MEIS1 activity promoted apoptosis, inhibited the proliferation of Kasumi-1 and Kasumi-6 cells, and increaseed the anticancer effect of the drugs, suggesting that inhibition of MEIS1 may be a potential strategy for the treatment of AML.

Negative Modulation of the Angiogenic Cascade Induced by Allosteric Kinesin Eg5 Inhibitors in a Gastric Adenocarcinoma In Vitro Model

Eg5 is a kinesin essential in bipolar spindle formation, overexpressed in tumours, thus representing a new target in cancer therapy. We aimed at evaluating the anti-cancer activity of Eg5 thiadiazoline inhibitors 2 and 41 on gastric adenocarcinoma cells (AGS), focusing on the modulation of angiogenic signalling. Docking studies confirmed a similar interaction with Eg5 to that of the parent compound K858. Thiadiazolines were also tested in combination with Hesperidin (HSD). Cell cycle analysis reveals a reduction of G1 and S phase percentages when 41 is administered as well as HSD in combination with K858. Western blot reveals Eg5 inhibitors capability to reduce PI3K, p-AKT/Akt and p-Erk/Erk expressions; p-Akt/Akt ratio is even more decreased in HSD+2 sample than the p-Erk/Erk ratio in HSD+41 or K858. VEGF expression is reduced when HSD+2 and HSD+41 are administered with respect to compounds alone, after 72 h. ANGPT2 gene expression increases in cells treated with 41 and HSD+2 compared to K858. The wound-healing assay highlights a reduction in the cut in HSD+2 sample compared to 2 and HSD. Thus, Eg5 inhibitors appear to modulate angiogenic signalling by controlling VEGF activity even better if combined with HSD. Overall, Eg5 inhibitors can represent a promising starting point to develop innovative anti-cancer strategies.

Targeting translation regulators improves cancer therapy

Deregulation of protein synthesis may be involved in multiple aspects of cancer, such as gene expression, signal transduction and drive specific cell biological responses, resulting in promoting cancer growth, invasion and metastasis. Study the molecular mechanisms about translational control may help us to find more effective anti-cancer drugs and develop novel therapeutic opportunities. Recently, the researchers had focused on targeting translational machinery to overcome cancer, and various small molecular inhibitors targeting translation factors or pathways have been tested in clinical trials and exhibited improving outcomes in several cancer types. There is no doubt that an insight into the class of translation regulation protein would provide new target for pharmacologic intervention and further provide opportunities to develop novel anti-tumor therapeutic interventions. In this review, we summarized the developments of translational control in cancer survival and progression et al, and highlighted the therapeutic approach targeted translation regulation to overcome the cancer.

Metastatic pancreatic neuroendocrine tumors have decreased somatostatin expression and increased Akt signaling

BACKGROUND

Patients with pancreatic neuroendocrine tumors often present with metastases, which reduce survival. Molecular features associated with pancreatic neuroendocrine tumor tumorigenesis have been reported, but mechanisms of metastasis remain incompletely understood.

METHODS

RNA sequencing was performed on primary and metastatic pancreatic neuroendocrine tumors from 43 patients. Differentially expressed genes were identified, and quantitative polymerase chain reaction used to confirm expression differences. BON cells were transfected with short interfering RNAs and short hairpin RNAs to create knockdowns. Expression changes were confirmed by quantitative polymerase chain reaction, cell viability assessed, and protein levels evaluated by Western blot and immunofluorescence.

RESULTS

Nodal and hepatic metastases had decreased expression of somatostatin compared with primary tumors (P = .003). Quantitative polymerase chain reaction in a validation cohort confirmed 5.3-fold lower somatostatin expression in hepatic metastases (P = .043) with no difference in somatostatin receptor, synaptophysin, or chromogranin A expression. Somatostatin knockdown in BON cells increased cell metabolic activity, viability, and growth. Somatostatin-knockdown cells had significantly higher levels of phosphorylated Akt protein and higher mTOR compared with controls.

CONCLUSION

Pancreatic neuroendocrine tumor metastases have lower expression of somatostatin than primary tumors, and somatostatin knockdown increased growth in pancreatic neuroendocrine tumor cell lines. This was associated with increased activation of Akt, identifying this pathway as a potential mechanism by which loss of somatostatin expression promotes the metastatic phenotype.

Pharmacokinetic analysis of [68Ga]Ga-DOTA-TOC PET in meningiomas for assessment of in vivo somatostatin receptor subtype 2

PURPOSE

DOTA-D-Phe¹-Tyr³-octreotide with gallium-68 ([⁶⁸Ga]Ga-DOTA-TOC) is one of the PET tracers that forms the basis for peptide receptor radionuclide therapy based on somatostatin receptor subtype 2 (SSTR2) expression in meningiomas. Yet, the quantitative relationship between [⁶⁸Ga]Ga-DOTA-TOC accumulation and SSTR2 is unknown. We conducted a correlative analysis of a range of [⁶⁸Ga]Ga-DOTA-TOC PET metric(s) as imaging surrogate(s) of the receptor binding in meningiomas by correlating the PET results with SSTR2 expression from surgical specimens. We additionally investigated possible influences of secondary biological factors such as vascularization, inflammation and proliferation.

METHODS

Fifteen patients with MRI-presumed or recurrent meningiomas underwent a 60-min dynamic [⁶⁸Ga]Ga-DOTA-TOC PET/CT before surgery. The PET data comprised maximum and mean standardized uptake values (SUV_max, SUV_mean) with and without normalization to reference regions, and quantitative measurements derived from kinetic modelling using a reversible two-tissue compartment model with the fractional blood volume (V_B). Expressions of SSTR2 and proliferation (Ki-67, phosphohistone-H3, proliferating cell nuclear antigen) were determined by immunohistochemistry and/or quantitative polymerase chain reaction (qPCR), while biomarkers of vascularization (vascular endothelial growth factor A (VEGFA), endothelial marker CD34) and inflammation (cytokine interleukin-18, microglia/macrophage-specific marker CD68) by qPCR.

RESULTS

Histopathology revealed 12 World Health Organization (WHO) grade I and three WHO grade II meningiomas showing no link to SSTR2. The majority of [⁶⁸Ga]Ga-DOTA-TOC PET metrics showed significant associations with SSTR2 protein, while all PET metrics were positively correlated with SSTR2 mRNA with the best results for mean tumour-to-blood ratio (TBR_mean) (r = 0.757, P = 0.001) and SUV_mean (r = 0.714, P = 0.003). Significant positive correlations were also found between [⁶⁸Ga]Ga-DOTA-TOC PET metrics, and VEGFA and V_B. SSTR2 mRNA was moderately correlated with VEGFA (r = 0.539, P = 0.038). Neither [⁶⁸Ga]Ga-DOTA-TOC PET metrics nor SSTR2 were correlated with proliferation or inflammation.

CONCLUSION

[⁶⁸Ga]Ga-DOTA-TOC accumulation in meningiomas is associated with SSTR2 binding and vascularization with TBR_mean being the best PET metric for assessing SSTR2.

In vitro anti-echinococcal activity of octreotide: Additive effect of metformin linked to autophagy

Cystic echinococcosis (CE) is a worldwide zoonosis caused by the Echinococcus granulosus larval stage. The currently available therapy for this disease is based on benzimidazoles, which are rarely curative and cause several adverse effects. Therefore, new treatment options are needed. Octreotide (Oct) is a somatostatin analogue which exhibits anti-proliferative and anti-secretory effects over several cancer cell lines expressing somatostatin receptors. Here, we assessed the in vitro pharmacological effect of Oct against the E. granulosus larval stage. The drug caused a significant dose-dependent decrease in the viability of both protoscoleces and metacestodes. SEM and TEM analysis showed ultrastructural damage in both larval forms under drug treatment. Based on this, we investigated the possible presence of an Oct binding receptor in the parasite. The putative somatostatin/allatostatin-like receptor (Eg-s/ast) conserves the characteristic topology and signature sequences of the prototype somatostatin receptor common to vertebrates and is expressed in both metacestodes and protoscoleces. Moreover, Oct treated-parasites showed the presence of autophagic structures and a significant increase in transcriptional expression of autophagy key genes such as Eg-atg6, Eg-atg8, Eg-atg12 and Eg-atg16. In addition, by in toto immunolocalization assays, an increase in the punctate pattern and Eg-Atg8 protein expression was detected in Oct-treated metacestodes. Subsequently, the combination of Oct and Met had an additive effect on the viability of both larval forms. Our results provide additional evidence for the participation of PI3K/AKT/TOR/autophagy pathway in the Echinococcus survival and suggest the concomitant use of these drugs as potential therapeutic agents in treating of CE.

Optimized functional and structural design of dual-target LMRAP, a bifunctional fusion protein with a 25-amino-acid antitumor peptide and GnRH Fc fragment

To develop fusion protein of a GnRH Fc fragment and the integrin targeting AP25 antitumor peptide for GnRH receptor-expressing cancer therapy. The LMRAP fusion protein was constructed. A transwell invasion assay was performed. The gene mRNA and protein levels of GnRHR-I, α5β1, and αvβ3 in different cancer cell lines were assessed. Cell proliferation was measured using a cell counting kit-8. An antagonist assay was performed on GnRH receptors. Anti-tumor activity was evaluated with a mouse xenograft tumor model. Immunohistochemistry (IHC) was applied to detect CD31 and CD34 expressions. Pharmacokinetic characteristics were determined with an indirect competition ELISA. The developed bifunctional fusion protein LMRAP not only inhibited HUVEC invasion, but also inhibited proliferation of GnRHR-I, α5β1, and αvβ3 high expression cancer cells. The IC₅₀ for LMRAP in the GnRH receptor was 6.235 × 10⁻⁴ mol/L. LMRAP significantly inhibited human prostate cancer cell line 22RV1 proliferation in vivo and in vitro. LMRAP significantly inhibited CD31 and CD34 expressions. The elimination half-life of the fusion protein LMRAP was 33 h in rats. The fusion protein made of a GnRH Fc fragment and the integrin targeting AP25 peptide retained the bifunctional biological activity of GnRHR blocking, angiogenesis inhibition, prolonged half-life and good tolerance.

Molecular Links Between Angiogenesis and Neuroendocrine Phenotypes in Prostate Cancer Progression

As a common therapy for prostate cancer, androgen deprivation therapy (ADT) is effective for the majority of patients. However, prolonged ADT promotes drug resistance and progression to an aggressive variant with reduced androgen receptor signaling, so called neuroendocrine prostate cancer (NEPC). Until present, NEPC is still poorly understood, and lethal with no effective treatments. Elevated expression of neuroendocrine related markers and increased angiogenesis are two prominent phenotypes of NEPC, and both of them are positively associated with cancers progression. However, direct molecular links between the two phenotypes in NEPC and their mechanisms remain largely unclear. Their elucidation should substantially expand our knowledge in NEPC. This knowledge, in turn, would facilitate the development of effective NEPC treatments. We recently showed that a single critical pathway regulates both ADT-enhanced angiogenesis and elevated expression of neuroendocrine markers. This pathway consists of CREB1, EZH2, and TSP1. Here, we seek new insights to identify molecules common to pathways promoting angiogenesis and neuroendocrine phenotypes in prostate cancer. To this end, our focus is to summarize the literature on proteins reported to regulate both neuroendocrine marker expression and angiogenesis as potential molecular links. These proteins, often described in separate biological contexts or diseases, include AURKA and AURKB, CHGA, CREB1, EZH2, FOXA2, GRK3, HIF1, IL-6, MYCN, ONECUT2, p53, RET, and RB1. We also present the current efforts in prostate cancer or other diseases to target some of these proteins, which warrants testing for NEPC, given the urgent unmet need in treating this aggressive variant of prostate cancer.

Heterogeneity of Vascular Endothelial Cells, De Novo Arteriogenesis and Therapeutic Implications in Pancreatic Neuroendocrine Tumors

Arteriogenesis supplies oxygen and nutrients in the tumor microenvironment (TME), which may play an important role in tumor growth and metastasis. Pancreatic neuroendocrine tumors (pNETs) are the second most common pancreatic malignancy and are frequently metastatic on presentation. Nearly a third of pNETs secrete bioactive substances causing debilitating symptoms. Current treatment options for metastatic pNETs are limited. Importantly, these tumors are highly vascularized and heterogeneous neoplasms, in which the heterogeneity of vascular endothelial cells (ECs) and de novo arteriogenesis may be critical for their progression. Current anti-angiogenetic targeted treatments have not shown substantial clinical benefits, and they are poorly tolerated. This review article describes EC heterogeneity and heterogeneous tumor-associated ECs (TAECs) in the TME and emphasizes the concept of de novo arteriogenesis in the TME. The authors also emphasize the challenges of current antiangiogenic therapy in pNETs and discuss the potential of tumor arteriogenesis as a novel therapeutic target. Finally, the authors prospect the clinical potential of targeting the FoxO1-CD36-Notch pathway that is associated with both pNET progression and arteriogenesis and provide insights into the clinical implications of targeting plasticity of cancer stem cells (CSCs) and vascular niche, particularly the arteriolar niche within the TME in pNETs, which will also provide insights into other types of cancer, including breast cancer, lung cancer, and malignant melanoma.

Scutellarin inhibits the invasive potential of malignant melanoma cells through the suppression epithelial-mesenchymal transition and angiogenesis via the PI3K/Akt/mTOR signaling pathway

Malignant melanoma is the leading cause of death from skin disease, due in large part to its propensity to metastasize. Scutellarin is an active flavone extracted from traditional Chinese herb Erigeron breviscapus (Vant.) Hand. Mazz. Recent studies have reported that scutellarin can be utilized to treat various types of tumors. In this study, we investigated the effects of scutellarin on melanoma cancer cell invasive potential and the molecular mechanisms underlying these effects using A375 melanoma cells lines. The in-vitro antitumor activity of scutellarin was evaluated by CCK-8 assay, wound-healing assay, transwell assays, adhesion assays, and tube formation assays to assess the cell viability, migration, invasion, adhesion, and angiogenesis, respectively. Also, western blotting assay was used to assess the level of PI3K/Akt/mTOR signaling pathway proteins in A375 cells. We found that scutellarin significantly inhibited melanoma cell lines and HUVECs viability in a time- and concentration-dependent manners. Additionally, scutellarin effectively suppressed tumor cell migration, invasion, adhesion through the suppression of EMT and angiogenesis by inhibiting the PI3K/Akt/mTOR signaling pathway. These results indicated that scutellarin could markedly inhibit the invasive potential of melanoma cell lines by suppressing the EMT and angiogenesis through the PI3K/Akt/mTOR signaling pathway. It suggests that scutellarin might be a potential compound in malignant melanoma treatment.

Antibody array strategy for human growth factor secretome profiling of GH-secreting adenomas

PURPOSES

To test if the antibody array strategy could be utilized to simultaneously detect the secretion of multiple growth factors by human pituitary GH-adenomas and to measure octreotide-induced alterations.

METHODS

Specimens of human pituitary adenomas were cultured and incubated with or without octreotide for 24 h. Conditional media were analyzed by human growth factor antibody array and VEGF concentrations were measured by ELISA. Media were also analyzed for GH concentrations. p21 expression levels were examined by Western blot of the specimens lysates.

RESULTS

The antibody arrays successfully identified growth factors secreted by GH-adenomas in vitro. Octreotide treatment induced both elevations and reductions in growth factors secretion. GH response to octreotide was measured, and in this small-sized study resistant and sensitive GH-adenomas presented with no unique secretome pattern of each of the groups. Octreotide-induced VEGF alterations analyzed by the antibody array and by ELISA were not fully matched.

CONCLUSIONS

This study suggests that the broad proteomic strategy of antibody arrays may be utilized to study the growth factors secretion pattern of GH-adenomas and its regulation by somatostatin analogs or other compounds.

Long noncoding RNA C2dat1 protects H9c2 cells against hypoxia injury by downregulating miR-22

Myocardial ischemia is accompanied with hypoxia injury in myocardial cells. Long noncoding RNAs (lncRNA) CAMK2D-associated transcript 1 (C2dat1) C2dat1) has been linked with several ischemic diseases. However, the investigation regarding its role in myocardial ischemia is relatively rare. The aim of this study was to examine the role of C2dat1 in hypoxia response in H9c2 cells. H9c2 cells were subjected to hypoxia to evoke cell damage. Expressions of C2dat1, miR-22, and VEGF in H9c2 cells were altered by transfection, and then cell survival, migration, and invasion were respectively assessed posttransfection. Regulatory relationship between C2dat1, miR-22, and VEGF, as well as the involvement of PI3K/AKT/mTOR and JAK/STAT3 pathways in H9c2 cells injury was then studied. C2dat1 upregulation ameliorated hypoxia injury in H9c2 cells due to the increased viability, migration, and invasion, as well as the decreased apoptosis. miR-22 was negatively regulated by C2dat1. The effects of C2dat1 on H9c2 cells injured by hypoxia were attenuated when miR-22 was overexpressed. VEGF was a target gene of miR-22, and VEGF exerted similar protective effects to C2dat1. Finally, we found that silence of C2dat1 deactivated PI3K/AKT/mTOR and JAK/STAT3 pathways via regulating miR-22 and its downstream gene VEGF. C2dat1-miR-22-VEGF axis could regulate hypoxia injury in H9c2 cells. C2dat1 alleviated hypoxia injury possibly via downregulating miR-22, then upregulating VEGF, which further enhancing the activation of PI3K/AKT/mTOR and JAK/STAT3 pathways.

Resistance to targeted treatment of gastroenteropancreatic neuroendocrine tumors

The mammalian target of rapamycin (mTOR) is part of the phosphoinositide-3-kinase (PI3K)/protein kinase B (Akt)/mTOR signaling. The PI3K/Akt/mTOR pathway has a pivotal role in the oncogenesis of neuroendocrine tumors (NETs). In addition, vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) drive angiogenesis in NETs and therefore contributes to neuroendocrine tumor development. Hence, mTOR and angiogenesis inhibitors have been developed. Everolimus, a first-generation mTOR inhibitor, has shown significant survival benefit in advanced gastroenteropancreatic NETs. Sunitinib, a pan-tyrosine kinase inhibitor that targets the VEGF receptor, has proven to increase progression-free survival in advanced pancreatic NETs. Nevertheless, primary and acquired resistance to rapalogs and sunitinib has limited the clinical benefit for NET patients. Despite the identification of multiple molecular mechanisms of resistance, no predictive biomarker has made it to the clinic. This review is focused on the mTOR signaling and angiogenesis in NET, the molecular mechanisms of primary and acquired resistance to everolimus and sunitinib and how to overcome this resistance by alternative drug compounds.

Biomarkers and polymorphisms in pancreatic neuroendocrine tumors treated with sunitinib

Several circulating biomarkers and single nucleotide polymorphisms (SNPs) have been correlated with efficacy and tolerability to antiangiogenic agents. These associations remain unexplored in well-differentiated, metastatic pancreatic neuroendocrine tumors treated with the multitargeted tyrosine kinase inhibitor sunitinib. We have assessed the effect on tumor response at 6 months, overall survival, progression-free survival and safety of 14 SNPs, and 6 soluble proteins. Forty-three patients were recruited. Two SNPs in the vascular endothelial growth factor receptor 3 (VEGFR-3) gene predicted lower overall survival: rs307826 with hazard ratio (HR) 3.67 (confidence interval [CI] 95%, 1.35-10.00) and rs307821 with HR 3.84 (CI 95%, 1.47-10.0). Interleukin-6 was associated with increased mortality: HR 1.06 (CI 95%, 1.01-1.12), and osteopontin was associated with shorter PFS: HR 1.087 (1.01-1.16), independently of Ki-67. Furthermore, levels of osteopontin remained higher at the end of the study in patients considered non-responders: 38.5 ng/mL vs. responders: 18.7 ng/mL, p-value=0.039. Dynamic upward variations were also observed with respect to IL-8 levels in sunitinib-refractory individuals: 28.5 pg/mL at baseline vs. 38.3 pg/mL at 3 months, p-value=0.024. In conclusion, two VEGFR-3 SNPs as well as various serum biomarkers were associated with diverse clinical outcomes in patients with well-differentiated pancreatic neuroendocrine tumors treated with sunitinib.

SSTR2A expression in medullary thyroid carcinoma is correlated with longer survival

PURPOSE

Medullary thyroid carcinoma (MTC) derives from the parafollicular C-cells of the thyroid gland. Somatostatin receptors (SSTRs) are expressed in various neuroendocrine tumours including MTC. The aim of this study was to evaluate SSTR2A as a prognostic factor for MTC, to study distribution of SSTR2A expression within tumours and to compare expression of SSTR2A between primary tumours and corresponding lymph node metastases.

METHODS

Patients who underwent surgery between 1988 and 2014 for MTC from five tertiary referral centres in The Netherlands were included. In total, primary tumours of 114 patients and lymph node metastases of 34 patients were analysed for expression of SSTR2A using a tissue microarray, and correlated with clinicopathological variables and survival.

RESULTS

The mean age of patients was 45.5 years (SD 16.2), 55 patients were male (49.5%). Primary tumours of 58 patients (50.9%) showed SSTR2A expression. In multivariate Cox-regression analysis, SSTR2A positivity correlated independently with better overall survival (OS) (HR 0.3; 95% CI 0.1-1.0). In stage IV MTC patients, 10-year survival rates for SSTR2A-negative and positive patients were 43% and 96%, respectively. In 53.9% of patients with lymph node metastases, expression in primary tumour and lymph node metastases differed.

CONCLUSION

SSTR2A expression is correlated with longer OS in MTC, especially for stage IV patients, suggesting that SSTR2A expression might be a useful prognostic factor in MTC. The SSTR2A status of the primary MTC does not predict expression in lymph node metastases.

Efficacy and safety of ramucirumab-containing chemotherapy in patients with pretreated metastatic gastric neuroendocrine carcinoma

BACKGROUND

Ramucirumab (RAM), a monoclonal antibody for vascular endothelial growth factor 2 (VEGFR2), has been effective for advanced gastric adenocarcinoma (AC). However, little is known about the efficacy of RAM-containing chemotherapy (RAM-CTx) in gastric neuroendocrine carcinoma (G-NEC).

METHODS

We retrospectively analysed and compared the clinical outcomes of patients (pts) with G-NEC receiving RAM-CTx, G-NEC receiving CTx without RAM and AC receiving RAM-CTx in our hospital. G-NEC was defined by neuroendocrine carcinoma features, regardless of the proportion, based on histology and neuroendocrine markers (synaptophysin, chromogranin A or CD56). VEGFR2 expression in tumour vessels was evaluated in archival primary G-NEC tissues by immunohistochemistry using the same anti-VEGFR2 primary antibody and scoring scheme (vascular VEGFR2 H-score) as in the REGARD trial.

RESULTS

Seventeen G-NEC receiving RAM-CTx, 13 G-NEC receiving CTx without RAM and 173 AC pts receiving RAM-CTx were analysed. The overall response rate (59% vs 8 % vs 28%), progression-free survival (median 7.7 vs 1.8 vs 3.3 months) and overall survival (median 16.1 vs 8.6 vs 9.6 months) were significantly better in pts with G-NEC receiving RAM-CTx than G-NEC receiving CTx without RAM or AC receiving RAM-CTx. No severe or unexpected adverse events occurred. The median vascular VEGFR2 H-score, based on available G-NEC tissues from 12 pts receiving RAM-CTx, was 220 (range 150-260), which was markedly higher than that reported on AC tissues from the REGARD trial as historical control (median 35, range 0-240).

CONCLUSIONS

RAM-CTx showed a promising activity without severe or unexpected safety profile in pts with G-NEC. This may in part be explained by higher vascular VEGFR2 expression in G-NEC tissues.

Androgen deprivation promotes neuroendocrine differentiation and angiogenesis through CREB-EZH2-TSP1 pathway in prostate cancers

The incidence of aggressive neuroendocrine prostate cancers (NEPC) related to androgen-deprivation therapy (ADT) is rising. NEPC is still poorly understood, such as its neuroendocrine differentiation (NED) and angiogenic phenotypes. Here we reveal that NED and angiogenesis are molecularly connected through EZH2 (enhancer of zeste homolog 2). NED and angiogenesis are both regulated by ADT-activated CREB (cAMP response element-binding protein) that in turn enhances EZH2 activity. We also uncover anti-angiogenic factor TSP1 (thrombospondin-1, THBS1) as a direct target of EZH2 epigenetic repression. TSP1 is downregulated in advanced prostate cancer patient samples and negatively correlates with NE markers and EZH2. Furthermore, castration activates the CREB/EZH2 axis, concordantly affecting TSP1, angiogenesis and NE phenotypes in tumor xenografts. Notably, repressing CREB inhibits the CREB/EZH2 axis, tumor growth, NED, and angiogenesis in vivo. Taken together, we elucidate a new critical pathway, consisting of CREB/EZH2/TSP1, underlying ADT-enhanced NED and angiogenesis during prostate cancer progression.

α7 Nicotinic Acetylcholine Receptor Regulates the Function and Viability of L Cells

Enteroendocrine L cells secrete the incretin hormone glucagon-like peptide-1 (GLP-1), and they also express the α7 nicotinic acetylcholine receptor (α7nAChR), which may regulate GLP-1 secretion. Here, GTS-21, a selective α7nAChR agonist, was used to examine the effect of α7nAChR activation in L-cell lines, mouse intestinal primary cell cultures, and C57BL/6 mice. GTS-21 stimulated GLP-1 secretion in vitro, and this effect was attenuated by an α7nAChR antagonist or by α7nAChR-specific small interfering RNA. Under in vitro cell culture conditions of glucotoxicity, GTS-21 restored GLP-1 secretion and improved L-cell viability while also acting in vivo to raise levels of circulating GLP-1 in mice. To assess potential signaling mechanisms underlying these actions of GTS-21, we first monitored Ca2+, cAMP, and phosphatidylinositol 3-kinase (PI3K) activity. As expected for a GLP-1 secretagogue promoting Ca2+ influx through α7nAChR cation channels, [Ca2+]i increased in response to GTS-21, but [cAMP]i was unchanged. Surprisingly, pharmacological inhibition of growth factor signaling pathways revealed that GTS-21 also acts on the PI3K-protein kinase B-mammalian target of rapamycin pathway to promote L-cell viability. Moreover, the Ca2+ chelator BAPTA-AM counteracted GTS-21‒stimulated PI3K activity, thereby indicating unexpected crosstalk of L-cell Ca2+ and growth factor signaling pathways. Collectively, these data demonstrate that α7nAChR activation enhances GLP-1 secretion by increasing levels of cytosolic Ca2+ while also revealing Ca2+- and PI3K-dependent processes of α7nAChR activation that promote L-cell survival.

Predictive Markers of Response to Everolimus and Sunitinib in Neuroendocrine Tumors

Neuroendocrine tumors (NETs) represent a large and heterogeneous group of malignancies with various biological and clinical characteristics, depending on the site of origin and the grade of tumor proliferation. In NETs, as in other cancer types, molecularly targeted therapies have radically changed the therapeutic landscape. Recently two targeted agents, the mammalian target of rapamycin inhibitor everolimus and the tyrosine kinase inhibitor sunitinib, have both demonstrated significantly prolonged progression free survival in patients with advanced pancreatic NETs. Despite these important therapeutic developments, there are still significant limitations to the use of these agents due to the lack of accurate biomarkers for predicting tumor response and efficacy of therapy. In this review, we provide an overview of the current clinical data for the evaluation of predictive factors of response to/efficacy of everolimus and sunitinib in advanced pancreatic NETs. Surrogate indicators discussed include circulating and tissue markers, as well as non-invasive imaging techniques.

Irinotecan plus cisplatin followed by octreotide long-acting release maintenance treatment in advanced gastroenteropancreatic neuroendocrine carcinoma: IPO-NEC study

There have been very few prospective studies of first-line chemotherapy on advanced gastroenteropancreatic neuroendocrine carcinoma (GEP-NEC). This phase II study assessed the activity and safety of irinotecan plus cisplatin (IP) followed by octreotide long-acting release (LAR) maintenance treatment in advanced GEP-NEC. Forty patients were treated and eighteen patients (45.0%) had a partial response. The median progression-free survival (PFS) and overall survival (OS) were 5.7 months and 12.9 months, respectively. Because GEP-NECs are heterogeneous, a subgroup analysis was conducted by dividing all patients into a high proliferation neuroendocrine tumor (NET) group (well differentiated neuroendocrine neoplasms with a Ki-67 level between 20-60%) or a poorly differentiated NEC (PDNEC) group. Compared with the PDNEC group, the patients in high proliferation NET group had a lower response rate (0% versus 51.4%) but longer PFS (8.9 versus 5.7 months) and received more octreotide LAR treatment (median cycles, 7 versus 3). The most common toxicities included grade 3/4 leukopenia/neutropenia (60%), nausea/vomiting (17.5%) and diarrhea (12.5%). Therefore, IP is an active regimen in patients with advanced GEP-PDNEC and should probably not be given to patients with advanced high proliferative NET. The benefit of octreotide LAR maintenance therapy on high proliferation NETs requires further study.

Exosomes serve as nanoparticles to suppress tumor growth and angiogenesis in gastric cancer by delivering hepatocyte growth factor siRNA

Exosomes derived from cells have been found to mediate signal transduction between cells and to act as efficient carriers to deliver drugs and small RNA. Hepatocyte growth factor (HGF) is known to promote the growth of both cancer cells and vascular cells, and the HGF‐cMET pathway is a potential clinical target. Here, we characterized the inhibitory effect of HGF siRNA on tumor growth and angiogenesis in gastric cancer. In addition, we showed that HGF siRNA packed in exosomes can be transported into cancer cells, where it dramatically downregulates HGF expression. A cell co‐culture model was used to show that exosomes loaded with HGF siRNA suppress proliferation and migration of both cancer cells and vascular cells. Moreover, exosomes were able to transfer HGF siRNA in vivo, decreasing the growth rates of tumors and blood vessels. The results of our study demonstrate that exosomes have potential for use in targeted cancer therapy by delivering siRNA.

Molecular challenges of neuroendocrine tumors

Neuroendocrine tumors (NETs) are a very heterogeneous group that are thought to originate from the cells of the endocrine and nervous systems. These tumors develop in a number of organs, predominantly in the gastrointestinal and pulmonary systems. Clinical detection and diagnosis are reliable at the late stages when metastatic spread has occurred. However, traditional conventional therapies such as radiation and chemotherapy are not effective. In the majority of cases even surgical resection at that stage is unlikely to produce promising reusults. NETs present a serious clinical challenge, as the survival rates remain low, and as these rare tumors are very difficult to study, novel approaches and therapies are required. This review will highlight the important points of accumulated knowledge covering the molecular aspects of the role of neuroendocrine cells, hormonal peptides, the reasons for ectopic hormone production in NET, neuropeptides and epigenetic regulation as well as the other challenging questions that require further understanding.

Antitumor activity and inhibitory effects on cancer stem cell-like properties of Adeno-associated virus (AAV) -mediated Bmi-1 interference driven by Bmi-1 promoter for gastric cancer

Bmi-1 is aberrantly activated in various cancers and plays a vital role in maintaining the self-renewal of stem cells. Our previous research revealed that Bmi-1 was overexpressed in gastric cancer (GC) and it's overexpression was an independent negative prognostic factor, suggesting it can be a therapeutic target. The main purpose of this investigation was to explore the antitumor activity of Bmi-1 interference driven by its own promoter (Ad-Bmi-1i) for GC. In this study, we used adenoviral vector to deliver Bmi-1 shRNA driven by its own promoter to treat GC. Our results revealed that Ad-Bmi-1i could selectively silence Bmi-1 in GC cells which overexpress Bmi-1 and suppress the malignant phenotypes and stem-like properties of GC cells in vitro and in vivo. Moreover, direct injection of Ad-Bmi-1i into xenografts suppressed tumor growth and destroyed cancer cells in vivo. Ad-Bmi-1i inhibited the proliferation of GC cells mainly via inducing senescence in vitro, but it suppressed tumor through inducing senescence and apoptosis, and inhibiting angiogenesis in vivo. Bmi-1 knockdown by Ad-Bmi-1i downregulated VEGF via inhibiting AKT activity. These results suggest that Ad-Bmi-1i not only inhibits tumor growth and stem cell-like phenotype by inducing cellular senescence directly, but also has an indirect anti-tumor activity by anti-angiogenesis effects via regulating PTEN/AKT/VEGF pathway. Transfer of gene interference guided by its own promoter by an adeno-associated virus (AAV) vector might be a potent antitumor approach for cancer therapy.

Tumor microenvironment of gastroenteropancreatic neuroendocrine neoplasms

Tumor microenvironment provides a unique environment for tumor development, where the biology behavior of tumor cells is regulated not only by their genetics but also by the surrounding environment. Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) originating from the neuroendocrine cells of the gastroenteropancreatic system are characterized by a propensity to secrete a variety of peptide hormones and biogenic amines. The symptoms of GEP-NENs at early stages are often atypical, thus delaying the diagnosis. A further understanding of the pathobiology of GEP-NENs on the basis of studies on GEP-NENs tumor microenvironment can provide new evidence for clinical diagnosis and treatment. This review aims to introduce different cell types, several proteins involved in extracellular matrix remodeling, some growth factors, and chromogranin A (CgA) in the tumor microenvironment of GEP-NENs, in order to highlight their indispensable roles in GEP-NENs progression.

The preliminary radiogenomics association between MR perfusion imaging parameters and genomic biomarkers, and their predictive performance of overall survival in patients with glioblastoma

The radiogenomics association of neovascularization is important for overall survival (OS) in glioblastoma patients and remains unclear. The purpose of this study is to assess the association between MR perfusion imaging derived parameters and genomic biomarkers of glioblastoma, and to evaluate their prognostic value. This retrospective study enrolled 41 patients with newly diagnosed glioblastoma. The mean and maximal relative cerebral blood volume (rCBV) ratio (rCBV_mean and rCBV_max), derived from MR perfusion weighted imaging, of the enhancing tumor, as well as maximal rCBV ratio of peri-enhancing tumor area (rCBV_peri-tumor) were measured. The ki-67 labeling index, mammalian target of rapamycin (mTOR) activation, epidermal growth factor receptor (EGFR) amplification, isocitrate dehydrogenase (IDH) mutation and TP53 were assessed. There was a significant correlation between rCBV_max and mTOR based on Pearson's correlations with Benjamini-Hochberg adjustment for controlling false discovery rate, p = 0.047. The rCBV_peri-tumor showed significant correlation with mTOR (p = 0.0183) after adjustment of gender and EGFR status. The mean rCBV_peri-tumor value of the patients with OS shorter than 14 months was significantly higher than patients with OS longer than 14 months, p = 0.002. The rCBV_peri-tumor and age were the two strongest predictors of OS (hazard ratio = 1.29 and 1.063 respectively) by Cox regression analysis. This study showed that hemodynamic abnormalities of glioblastoma were associated with genomics activation status of mTOR-EGFR pathway, however, the radiogenomics associations are different in enhancing and peri-enhancing area of glioblastoma. The rCBV_peri-tumor has better prognostic value than genomic biomarkers alone.

Anti-proliferative and anti-secretory effects of everolimus on human pancreatic neuroendocrine tumors primary cultures: is there any benefit from combination with somatostatin analogs?

Therapeutic management of gastroenteropancreatic neuroendocrine tumors (GEP-NETs) is challenging. The mammalian target of rapamycin (mTOR) inhibitor everolimus recently obtained approval from the Food and Drug Administration for the treatment of patients with advanced pancreatic neuroendocrine tumors (pNETs). Despite its promising antitumor efficacy observed in cell lines, clinical benefit for patients is unsatisfactory. The limited therapeutic potential of everolimus in cancer cells has been attributed to Akt activation due to feedback loops relief following mTOR inhibition. Combined inhibition of Akt might then improve everolimus antitumoral effect. In this regard, the somatostatin analog (SSA) octreotide has been shown to repress the PI3K/Akt pathway in some tumor cell lines. Moreover, SSAs are well tolerated and routinely used to reduce symptoms caused by peptide release in patients carrying functional GEP-NETs. We have recently established and characterized primary cultures of human pNETs and demonstrated the anti-proliferative effects of both octreotide and pasireotide. In this study, we aim at determining the antitumor efficacy of everolimus alone or in combination with the SSAs octreotide and pasireotide in primary cultures of pNETs. Everolimus reduced both Chromogranin A secretion and cell viability and upregulated Akt activity in single treatment. Its anti-proliferative and anti-secretory efficacy was not improved combined with the SSAs. Both SSAs did not overcome everolimus-induced Akt upregulation. Furthermore, caspase-dependent apoptosis induced by SSAs was lost in combined treatments. These molecular events provide the first evidence supporting the lack of marked benefit in patients co-treated with everolimus and SSA.

The Antiproliferative Role of Lanreotide in Controlling Growth of Neuroendocrine Tumors: A Systematic Review

BACKGROUND

Neuroendocrine tumors (NETs) are a heterogeneous group of tumors, with >50% of cases involving the gastrointestinal system or pancreas. Somatostatin analogs (SSAs) are used for treating NET-related secretory syndromes and, more recently, for their antiproliferative effects. We conducted a systematic review of published literature on the antiproliferative efficacy and safety of the SSA lanreotide Autogel in the management of NETs to gain a fuller understanding of the evidence and identify future areas of research.

METHODS

Searches were conducted in PubMed up to March 16, 2016, and in the proceedings of four congresses from 2013 to 2016.

RESULTS

Screening of 1,132 publications identified in the searches found 40 relevant publications, including 27 full-length publications and 13 congress abstracts. Twenty-four of these publications reported antiproliferative efficacy data for lanreotide Autogel. The CLARINET study showed that 120 mg lanreotide Autogel every 4 weeks improves progression-free survival (PFS) in patients with gastroenteropancreatic (GEP)-NETs, with grade 1 or grade 2 (Ki-67 <10%) disease, providing class I evidence of its antiproliferative effects. The CLARINET open-label extension study reported a median PFS of 32.8 months with lanreotide Autogel. Other smaller studies generally support CLARINET.

CONCLUSION

Current clinical evidence shows that lanreotide Autogel has good antiproliferative activity with favorable safety and tolerability in patients with GEP-NETs, suggesting it should be considered as an early first-line treatment in this population. Further studies are needed to assess the potential benefits of higher doses and the use of lanreotide Autogel in combination therapy and as maintenance therapy in the absence of disease progression following other therapies. The Oncologist 2017;22:272-285 IMPLICATIONS FOR PRACTICE: This review presents the current clinical evidence for the antiproliferative activity of lanreotide Autogel in patients with midgut or pancreatic neuroendocrine tumors (NETs) and shows its effectiveness, safety, and tolerability in these patient populations. By systematically presenting all the clinical evidence, the review adds to existing publications by discussing results in a broad range of settings. The review also indicates future directions for investigation of the use of lanreotide Autogel in NETs originating in other locations, in combination therapy, or as maintenance therapy in progressive disease.

New therapeutic approaches to metastatic gastroenteropancreatic neuroendocrine tumors: A glimpse into the future

Neuroendocrine (NE) gastroenteropancreatic tumors are a heterogeneous group of neoplasias arising from neuroendocrine cells of the embryological gut. Their incidence have increased significantly over the past 3 decades probably due to the improvements in imaging and diagnosis. The recent advances in molecular biology have translated into an expansion of therapeutic approaches to these patients. Somatostatin analogs, which initially were approved for control of hormonal syndromes, have recently been proven to inhibit tumor growth. Several new drugs such as antiangiogenics and others targeting mammalian target of rapamycin pathways have been approved to treat progressive pancreatic neuroendocrine tumors (NETs) although their role in non-pancreatic is still controversial. The treatment of NETs requires a coordinated multidisciplinary approach. The management of localized NETs primarily involves surgical resection followed by surveillance. However, the treatment of unresectable and/or metastatic disease may involve a combination of surgical resection, systemic therapy, and liver-directed therapies with the goal of alleviating symptoms of peptide release and controlling tumor growth. This article will review the current therapeutic strategies for metastatic gastroenteropancreatic NETs and will take a glimpse into the future approaches.

Octreotide therapy in meningiomas: in vitro study, clinical correlation, and literature review

OBJECTIVE Meningiomas express somatostatin receptor subtype 2 (SST2), which is targeted by the somatostatin analog octreotide. However, to date, using somatostatin analog therapy for the treatment of these tumors in clinical practice has been debated. This study aims to clarify the in vitro effects of octreotide on meningiomas for precise clinical applications. METHODS The effects of octreotide were analyzed in a large series of 80 meningiomas, including 31 World Health Organization (WHO) Grade II and 4 WHO Grade III tumors, using fresh primary cell cultures to study the impact on cell viability, apoptosis, and signal transduction pathways. RESULTS SST2 mRNA was detected in 100% of the tested meningiomas at levels similar to those observed in other SST2-expressing tumors, neuroendocrine tumors, or pituitary adenomas. Octreotide significantly decreased cell proliferation in 88% of meningiomas but did not induce cell death. On average, cell proliferation was more inhibited in the meningioma group expressing a high level of SST2 than in the low-SST2 group. Moreover, octreotide response was positively correlated to the level of merlin protein and inversely correlated to the level of phosphorylated p70-S6 kinase, a downstream effector of the PI3K/Akt/mammalian target of rapamycin (mTOR) pathway. Octreotide inhibited Akt phosphorylation and activated tyrosine phosphatase without impacting the extracellular regulated kinase (ERK) pathway. CONCLUSIONS Octreotide acts exclusively as an antiproliferative agent and does not promote apoptosis in meningioma in vitro. Therefore, in vivo, octreotide is likely to limit tumor growth rather than induce tumor shrinkage. A meta-analysis of the literature reveals an interest in octreotide for the treatment of WHO Grade I tumors, particularly those in the skull base for which the 6-month progression-free survival level reached 92%. Moreover, somatostatin analogs, which are well-tolerated drugs, could be of interest for use as co-targeting therapies for aggressive meningiomas.

Osteonecrosis of the jaw associated with ziv-aflibercept

Medication-related osteonecrosis of the jaw (MRONJ) has been associated with medications that include bisphosphonates (BPs), denosumab, bevacizumab and sunitinib. Ziv-aflibercept is a recombinant human vascular endothelial growth factor (VEGF) receptor which has been used to treat patients with various advanced solid tumors. We report three patients without a history of the use of medications known to cause MRONJ presenting with jaw osteonecrosis typical for MRONJ following therapy with ziv-aflibercept. All patients had metastatic gastrointestinal cancer treated with ziv-aflibercept and were evaluated for MRONJ because of exposed bone in the oral cavity. None of the patients had received antiresorptive therapies or any other medication known to cause MRONJ, and none had received radiation therapy to the jaws. Patients were aged 43, 51, 63 and all were males. Patients received 7, 16 and 23 cycles of ziv-aflibercept treatment and developed necrotic bone. All three patients presented with mandibular involvement, with two reporting pain. Patients were managed with anti-microbial mouth rinse, antibiotics and non-surgical sequestrectomy and followed up for 1.5, 2, and 2 months; two patients became asymptomatic while one patient continued to have pain. These three reported patients with a history of ziv-aflibercept therapy and no reported use of other medications known to cause MRONJ developed exposed necrotic bone of the jaw. We believe that ziv-aflibercept is another medication that can potentially cause MRONJ probably through its anti-VEGF activity, similar to bevacizumab and sunitinib.

The pivotal role of mammalian target of rapamycin inhibition in the treatment of patients with neuroendocrine tumors

Significant advances have been made toward understanding the biology of neuroendocrine tumors (NET) in terms of defining prognosis and improving clinical management; however, many unmet needs remain. The treatment landscape for NET has evolved, with the approval of the targeted agents everolimus and sunitinib for the treatment of advanced pancreatic NET in 2011 followed by the approval of everolimus for the treatment of advanced nonfunctional gastrointestinal and lung NET in 2016. Mammalian target of rapamycin (mTOR) and components of the mTOR pathway play pivotal roles in NET pathogenesis. Effects of the mTOR inhibitor everolimus have been well documented in preclinical and clinical studies, both as monotherapy and combination therapy. mTOR inhibition as backbone therapy within the NET treatment landscape is a focus of continuing research, which includes evaluation of the growing armamentarium of approved and investigational agents as potential combination partners. Data evaluating the clinical benefits of agents targeting mTOR and related pathways (alone and in combination) in the treatment of patients with NET continue to increase. Many of the findings to date are encouraging.

The effects of somatostatin analogue therapy on pituitary tumor volume in patients with acromegaly

INTRODUCTION

In nearly all cases, acromegaly is caused by excess GH from a pituitary adenoma, resulting in elevated circulating levels of GH and, subsequently, IGF-1. Treatment goals are to eliminate morbidity and restore the increased mortality to normal rates. Therapeutic strategies aim to minimize tumor mass and normalize GH and IGF-1 levels. Somatostatin analogues are the medical treatment of choice in acromegaly, as first-line or post-surgical therapy, and have proven efficacy in pituitary tumor volume reduction (TVR).

METHODS

Here we review the effects of somatostatin analogue therapy on pituitary tumor volume in patients with acromegaly.

RESULTS

TVR with somatostatin analogues may be mediated by direct anti-proliferative effects via activation of somatostatin receptors, or by indirect effects, such as angiogenesis inhibition, and is more pronounced when they are administered as first-line therapy. Various studies of first-line treatment with octreotide LAR have shown significant TVR in ≥73% of patients. First-line treatment with lanreotide Autogel has shown evidence of TVR, although more studies are needed. In a recent randomized, double-blind, 12-month trial in 358 medical-treatment-naïve acromegaly patients, significant TVR was achieved by 81% of patients administered pasireotide LAR and 77% administered octreotide LAR. Pre-operative somatostatin analogue therapy may also induce TVR and improve post-operative disease control compared with surgery alone. TVR is progressive with prolonged treatment, and decreased IGF-1 levels may be its best predictor, followed by age and degree of GH decrease. However, TVR does not always correlate with degree of biochemical control.

CONCLUSION

Somatostatin analogues (first- or second-line treatment) are the mainstay of medical therapy and, as first-line medical therapy, are associated with significant pituitary TVR in most patients.

Filamin-A is required to mediate SST2 effects in pancreatic neuroendocrine tumours

Somatostatin receptor type 2 (SST2) is the main pharmacological target of somatostatin (SS) analogues widely used in patients with pancreatic neuroendocrine tumours (P-NETs), this treatment being ineffective in a subset of patients. Since it has been demonstrated that Filamin A (FLNA) is involved in mediating GPCR expression, membrane anchoring and signalling, we investigated the role of this cytoskeleton protein in SST2 expression and signalling, angiogenesis, cell adhesion and cell migration in human P-NETs and in QGP1 cell line. We demonstrated that FLNA silencing was not able to affect SST2 expression in P-NET cells in basal conditions. Conversely, a significant reduction in SST2 expression (-43 ± 21%, P < 0.05 vs untreated cells) was observed in FLNA silenced QGP1 cells after long term SST2 activation with BIM23120. Moreover, the inhibitory effect of BIM23120 on cyclin D1 expression (-46 ± 18%, P < 0.05 vs untreated cells), P-ERK1/2 levels (-42 ± 14%; P < 0.05 vs untreated cells), cAMP accumulation (-24 ± 3%, P < 0.05 vs untreated cells), VEGF expression (-31 ± 5%, P < 0.01 vs untreated cells) and in vitro release (-40 ± 24%, P < 0.05 vs untreated cells) was completely lost after FLNA silencing. Interestingly, BIM23120 promoted cell adhesion (+86 ± 45%, P < 0.05 vs untreated cells) and inhibited cell migration (-24 ± 2%, P < 0.00001 vs untreated cells) in P-NETs cells and these effects were abolished in FLNA silenced cells. In conclusion, we demonstrated that FLNA plays a crucial role in SST2 expression and signalling, angiogenesis, cell adhesion and cell migration in P-NETs and in QGP1 cell line, suggesting a possible role of FLNA in determining the different responsiveness to SS analogues observed in P-NET patients.

Temozolomide-based combination for advanced neuroendocrine neoplasms: a systematic review of the literature

BACKGROUND

In this systematic review, we explored the value of using temozolomide (TMZ)-based combinations for advanced neuroendocrine neoplasms (NENs).

METHODS

Database search were conducted using the terms 'NENs' and 'TMZ' and 'systemic therapy.' Outcomes of interest included progression-free survival and overall survival, toxicities and tumor response.

RESULTS

In total, 16 trials including 348 patients were included. Median progression-free survival ranged from 6 to 31 months. The disease control rate ranged from 65 to 100%. Frequently reported grade 3/4 toxicities were leukopenia, lymphopenia and elevated transaminases.

CONCLUSION

The published clinical data suggest that TMZ-based combination with some anticancer agents (especially capecitabine) could be an effective treatment option for advanced low-intermediate grade NENs.

Presence of sst5TMD4, a truncated splice variant of the somatostatin receptor subtype 5, is associated to features of increased aggressiveness in pancreatic neuroendocrine tumors

Purpose

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are rare and heterogeneous tumors, and their biological behavior is not well known. We studied the presence and potential functional roles of somatostatin receptors (sst1-5), focusing particularly on the truncated variants (sst5TMD4, sst5TMD5) and on their relationships with the angiogenic system (Ang/Tie-2 and VEGF) in human GEP-NETs.

Experimental Design

We evaluated 42 tumor tissue samples (26 primary/16 metastatic) from 26 patients with GEP-NETs, and 30 non-tumoral tissues (26 from adjacent non-tumor regions and 4 from normal controls) from a single center. Expression of sst1-5, sst5TMD4, sst5TMD5, Ang1-2, Tie-2 and VEGF was analyzed using real-time qPCR, immunofluorescence and immunohistochemistry. Expression levels were associated with tumor characteristics and clinical outcomes. Functional role of sst5TMD4 was analyzed in GEP-NET cell lines.

Results

sst1 exhibited the highest expression in GEP-NET, whilst sst2 was the most frequently observed sst-subtype (90.2%). Expression levels of sst1, sst2, sst3, sst5TMD4, and sst5TMD5 were significantly higher in tumor tissues compared to their adjacent non-tumoral tissue. Lymph-node metastases expressed higher levels of sst5TMD4 than in its corresponding primary tumor tissue. sst5TMD4 was also significantly higher in intestinal tumor tissues from patients with residual disease of intestinal origin compared to those with non-residual disease. Functional assays demonstrated that the presence of sst5TMD4 was associated to enhanced malignant features in GEP-NET cells. Angiogenic markers correlated positively with sst5TMD4, which was confirmed by immunohistochemical/fluorescence studies.

Conclusions

sst5TMD4 is overexpressed in GEP-NETs and is associated to enhanced aggressiveness, suggesting its potential value as biomarker and target in GEP-NETs.

Dual inhibition of mTOR pathway and VEGF signalling in neuroendocrine neoplasms: from bench to bedside

After years of limited progress in the treatment of neuroendocrine neoplasms (NENs), an increasing number of therapeutic targets have recently emerged as potential tools to improve disease outcome. The mammalian target of rapamycin (mTOR) pathway and vascular endothelial growth factor (VEGF) signalling are implicated in the regulation of cell growth, proliferation, neo-angiogenesis and tumour cell spread. Their combined blockade, in a simultaneous or sequential strategy, represents an intriguing biological rationale to overcome the onset of resistance mechanisms. However, is becoming increasingly imperative to find the optimal sequential strategy according to the best toxicity profile, and also to identify predictive biomarkers. We will provide an overview of the pre-clinical and clinical data relating to mTOR pathway/VEGF signalling as a potential targets of treatment in NENs.

Phase II clinical trial of pasireotide long-acting repeatable in patients with metastatic neuroendocrine tumors

Pasireotide long-acting repeatable (LAR) is a novel somatostatin analog (SSA) with avid binding affinity to somatostatin receptor subtypes 1, 2, 3 (SSTR1,2,3) and 5 (SSTR5). Results from preclinical studies indicate that pasireotide can inhibit neuroendocrine tumor (NET) growth more robustly than octreotide in vitro. This open-label, phase II study assessed the clinical activity of pasireotide in treatment-naïve patients with metastatic grade 1 or 2 NETs. Patients with metastatic pancreatic and extra-pancreatic NETs were treated with pasireotide LAR (60 mg every 4 weeks). Previous systemic therapy, including octreotide and lanreotide, was not permitted. Tumor assessments were performed every 3 months using Response Evaluation Criteria in Solid Tumors (RECIST) criteria. The primary endpoint was progression-free survival (PFS). The secondary endpoints included overall survival (OS), overall radiographic response rate (ORR), and safety. Twenty-nine patients were treated with pasireotide LAR (60 mg every 4 weeks) and 28 were evaluable for response. The median PFS was 11 months. The most favorable effect was observed in patients with low hepatic tumor burden, normal baseline chromogranin A, and high tumoral SSTR5 expression. Median OS has not been reached; the 30-month OS rate was 70%. The best radiographic response was partial response in one patient (4%), stable disease in 17 patients (60%), and progressive disease in ten patients (36%). Although grade 3/4 toxicities were rare, pasireotide LAR treatment was associated with a 79% rate of hyperglycemia including 14% grade 3 hyperglycemia. Although pasireotide appears to be an effective antiproliferative agent in the treatment of advanced NETs, the high incidence of hyperglycemia raises concerns regarding its suitability as a first-line systemic agent in unselected patients. SSTR5 expression is a potentially predictive biomarker for response.

MicroRNA-26a suppresses angiogenesis in human hepatocellular carcinoma by targeting hepatocyte growth factor-cMet pathway

MicroRNA (miR)-26a can suppress tumor growth and metastasis of hepatocellular carcinoma (HCC). Since angiogenesis is important for tumor growth and metastasis, we investigated the possible roles of miR-26a in tumor angiogenesis. Down-regulation of miR-26a was found to correlate with an increased angiogenic potential of HCC. Through gain- and loss-of-function studies, miR-26a was demonstrated to significantly inhibit vascular endothelial growth factor A (VEGFA) expression in HCC cells and then suppress the promoting effects of HCC cells on in vitro proliferation, migration, and capillary tube formation of endothelial cells, as well as in vivo tumor angiogenesis of HCC. Hepatocyte growth factor (HGF) was identified as a target of miR-26a. HGF simulation antagonized the effects induced by miR-26a up-regulation. In contrast, silencing HGF induced similar effects to miR-26a. We further found that miR-26a exerted its antiangiogenesis function, at least in part, by inhibiting HGF-hepatocyte growth factor receptor (cMet) and its downstream signaling pathway, in turn, suppressing VEGFA production in HCC cells and impairing VEGFR2-signaling in endothelial cells. HCC patients who had high miR-26a, low HGF, low VEGFA, or low microvessel density (MVD) in tumor tissues had a better prognosis with longer overall survival (OS) and time to recurrence (TTR). In multivariate analysis, miR-26a, or in combination with HGF, was demonstrated to be an independent prognostic indicator for OS and TTR of HCC patients.

CONCLUSION

miR-26a could suppress tumor angiogenesis of HCC through HGF-cMet signaling, and it is a new hopeful therapeutic target and prognostic marker for HCC.

Targeting PI3K/Akt/mTOR Signaling in Cancer

The phosphatidylinositol-3-kinase (PI3K)/Akt and the mammalian target of rapamycin (mTOR) signaling pathways are two pathways crucial to many aspects of cell growth and survival, in physiological as well as in pathological conditions (e.g., cancer). Indeed, they are so interconnected that, in a certain sense, they could be regarded as a single, unique pathway. In this paper, after a general overview of the biological significance and the main components of these pathways, we address the present status of the development of specific PI3K, Akt, and mTOR inhibitors, from already registered medicines to novel compounds that are just leaving the laboratory bench.

Angiogenesis and vascular maturation in neuroendocrine tumors

Neuroendocrine tumors (NETs) are highly vascularized, but the process of proliferation and maturation of vascular structures during tumor development and progression has remained unknown. We examined the structural alterations of intratumoral blood vessels in human gastroenteropancreatic NET. Microvessel density was evaluated using the endothelial cell markers vasohibin-1 (VASH-1), CD31, and endoglin in 135 cases. Double immunohistochemistry staining was performed to localize endothelium and pericytes on the same vessels using the pericyte marker nestin. The ratio of Ki-67/CD31 was significantly correlated with that of VASH-1/CD31 positivity (P<.001), indicating that the ratio of VASH-1/CD31 also reflects the status of neovascularization in NET. This ratio was higher in NET than in its nonneoplastic counterpart (P=.10) and tended to increase according to World Health Organization (WHO) grade, although the differences were not statistically significant (P=.32). The ratio of VASH-1/nestin-positive vessels, representing the maturation of neovessels, was also significantly higher in NET than in its nonneoplastic counterparts (P=.003). Among WHO grades, the ratio increased from grade 1 to grade 2 (P=.36) and decreased in neuroendocrine carcinoma (P=.34). Our results demonstrated that VASH-1/CD31 can be an ideal immunohistochemical marker for characterizing neovascularization in NET. The VASH-1/CD31 content increased with WHO grade, and the vessels covered by pericytes decreased in higher grades. These structural changes in the vessels are considered to play an important role in inducing tumor-cell proliferation.