Somatostatin inhibits the production of vascular endothelial growth factor in human glioma cells

Glioma and Peptidergic Systems: Oncogenic and Anticancer Peptides

Glioma cells overexpress different peptide receptors that are useful for research, diagnosis, management, and treatment of the disease. Oncogenic peptides favor the proliferation, migration, and invasion of glioma cells, as well as angiogenesis, whereas anticancer peptides exert antiproliferative, antimigration, and anti-angiogenic effects against gliomas. Other peptides exert a dual effect on gliomas, that is, both proliferative and antiproliferative actions. Peptidergic systems are therapeutic targets, as peptide receptor antagonists/peptides or peptide receptor agonists can be administered to treat gliomas. Other anticancer strategies exerting beneficial effects against gliomas are discussed herein, and future research lines to be developed for gliomas are also suggested. Despite the large amount of data supporting the involvement of peptides in glioma progression, no anticancer drugs targeting peptidergic systems are currently available in clinical practice to treat gliomas.

Circulating Angiogenic Markers in Gastroenteropancreatic Neuroendocrine Neoplasms: A Systematic Review

Background: Neuroendocrine neoplasms are a heterogeneous group of tumors that raise challenges in terms of diagnosis, treatment and monitoring. Despite continuous efforts, no biomarker has showed satisfying accuracy in predicting outcome or response to treatment. Methods: We conducted a systematic review to determine relevant circulating biomarkers for angiogenesis in neuroendocrine tumors. We searched three databases (Pubmed, Embase, Web of Science) using the keywords “neuroendocrine” and “biomarkers”, plus specific biomarkers were searched by full and abbreviated name. From a total of 2448 publications, 11 articles met the eligibility criteria. Results: VEGF is the most potent and the most studied angiogenic molecule, but results were highly controversial. Placental growth factor, Angiopoietin 2 and IL-8 were the most consistent markers in predicting poor outcome and aggressive disease behavior. Conclusions: There is no robust evidence so far to sustain the use of angiogenic biomarkers in routine practice, although the results show promising leads.

The Never-Ending History of Octreotide in Thymic Tumors: A Vintage or A Contemporary Drug?

Simple Summary

Thymic epithelial tumors are rare tumors frequently associated with paraneoplastic syndromes, the most common being myasthenia gravis and pure red cell aplasia. While patients with limited-stage cancer can often undergo resolutive surgery, advanced surgically unresectable and metastatic tumors can be refractory to first-line platinum-based treatment and represent a medical challenge. Somatostatin receptor expression was documented in thymic tumors both in vivo and in vitro and represents the rationale for therapeutic use. Despite single-case reports and three single-arm phase II studies, as well as the inclusion of somatostatin analogs in National Comprehensive Cancer Network guidelines, the role of these drugs in thymic epithelial tumors is still rather undefined.

Abstract

Thymic epithelial tumors are rare tumors usually presenting as a mass located in the anterior mediastinum and/or with symptoms deriving from associated paraneoplastic syndromes. Unresectable platinum-refractory tumors are often treated with alternative regimens, including chemotherapeutic agents as well as chemo-free regimens. The most popular unconventional therapy is represented by the somatostatin analog octreotide, which can be used alone or with prednisone. The in vivo expression of somatostatin receptors documented by imaging with indium-labeled octreotide or gallium-68 Dotapeptides, the successful use of octreotide and prednisone in a chemo-refractory patient, and, thereafter, the experiences from a case series have enforced the idea that this treatment merits consideration—as proved by its inclusion in the National Comprehensive Cancer Network guidelines. In the present review, we analyze the preclinical basis for the therapeutic use of somatostatin and prednisone in refractory thymic tumors and discuss the available studies looking at future perspectives.

The impact of SST2 trafficking and signaling in the treatment of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (Pan-NETs), are heterogeneous neoplasms, whose incidence and prevalence are increasing worldwide. Pan-NETs are characterized by the expression of somatostatin receptors (SSTs). In particular, SST2 is the most widely distributed SST in NETs, thus representing the main molecular target for somatostatin analogs (SSAs). SSAs are currently approved for the treatment of well-differentiated NETs, and radionuclide-labeled SSAs are used for diagnostic and treatment purposes. SSAs, by binding to SSTs, have been shown to inhibit hormone secretion and thus provide control of hypersecretion symptoms, when present, and inhibit tumor proliferation. After SSA binding to SST2, the fate of the receptor is determined by trafficking mechanisms, crucial for the response to endogenous or pharmacological ligands. Although SST2 acts mostly through G protein-dependent mechanism, receptor-ligand complex endocytosis and receptor trafficking further regulate its function. SST2 mediates the decrease of hormone secretion via a G protein-dependent mechanism, culminating with the inhibition of adenylyl cyclase and calcium channels; it also inhibits cell proliferation and increases apoptosis through the modulation of protein tyrosine phosphatases. Moreover, SST2 inhibits angiogenesis and cell migration. In this respect, the cross-talk between SST2 and its interacting proteins, including Filamin A (FLNA) and aryl hydrocarbon receptor-interacting protein (AIP), plays a crucial role for SST2 signaling and responsiveness to SSAs. This review will focus on recent studies from our and other groups that have investigated the trafficking and signaling of SST2 in Pan-NETs, in order to provide insights into the mechanisms underlying tumor responsiveness to pharmacological treatments.

By Reducing Production of Vascular Endothelial Growth Factor Octreotide Improves the Peritoneal Vascular Alterations Induced by Hypertonic Peritoneal Dialysis Solution

Objective

Chronic peritoneal dialysis (PD) may eventually result in vascular alterations of varying degree, which lead to progressive reduction in dialytic efficacy. Although the pathogenesis has not been elucidated yet, vascular endothelial growth factor (VEGF) has been proposed to play a central role in the process leading to vascular alterations.

Design

Rats were allocated to three groups: no treatment, intraperitoneal introduction of hypertonic PD solution alone, and intraperitoneal introduction of hypertonic PD solution plus octreotide. After 4 weeks, a 1-hour peritoneal equilibration test (PET) was performed. Dialysate-to-plasma urea ratio (D/P urea), glucose reabsorption (D1/D0 glucose), ultrafiltration volume (UF), and levels of dialysate protein and VEGF were determined. Peritoneal membrane histology was evaluated by light microscopy.

Results

Compared with the control group, rats treated with hypertonic PD solution showed dramatically deranged peritoneal function tests (UF: 5.8 ± 0.9 mL vs 1.3 ± 0.6 mL; D/P urea: 0.49 ± 0.1 vs 0.74 ± 0.04; D1/D0 glucose: 0.55 ± 0.05 vs 0.34 ± 0.06) and morphology (thickness: 4.6 ± 0.4 μ vs 62 ± 12 μ; neovascularisation: 0.1 ± 0.3 vessels per field vs 2.2 ± 0.3 vessels per field). Similarly, a higher level of VEGF was found in the rats treated with hypertonic PD solution. In rats treated with hypertonic solution plus octreotide, peritoneal thickness was not completely reduced (25 ± 5 μ), but peritoneal functions were protected (UF: 4.0 ± 0.5 mL; D/P urea: 0.58 ± 0.02; D1/D0 glucose: 0.51 ± 0.02). Moreover, VEGF level and neoangiogenesis were significantly less in the octreotide group than in the group treated with hypertonic dextrose alone.

Conclusion

Our data document that, by increasing the production of VEGF, a high glucose concentration can cause vascular alterations within the peritoneal membrane. Octreotide can protect against the vascular alterations and preserve peritoneal function by inhibiting overexpression of VEGF and regulating the inflammatory response in the peritoneum.

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.

The Role of Somatostatin in Vasogenic Meningioma Associated Brain Edema

Many tumors, including meningiomas, express somatostatin receptors, suggesting the application of somatostatin analogues for therapy and diagnosis. Sixty percent of meningiomas are associated with perilesional edema, whose development seems to be related to the vascular endothelial growth factor, although it requires an efficient pial blood supply. However, in several neoplastic models, other mediators seem to cooperate with vascular endothelial growth factor in regulating angiogenesis. We evaluated somatostatin receptors (sst2) in relation to the possibility that somatostatin analogues may influence vascular endothelial growth factor production with reduction of edema. Of 35 studied meningiomas, 21 presented peritumoural edema. Vascular endothelial growth factor, microvascular density and pial blood supply were significantly related to the edema (P = 0.0001, P = 0.0001, P = 0.0005). Similarly, a relation was found between sst2 and microvascular density (r = 0.58, P <0.001) and between sst2 and vascular endothelial growth factor expression (P = 0.03). This suggests that somatostatin analogues may be relevant for the treatment of meningiomas.

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 truncated somatostatin receptor sst5TMD4 stimulates the angiogenic process and is associated to lymphatic metastasis and disease-free survival in breast cancer patients

The truncated somatostatin receptor sst5TMD4 is associated with poor prognosis in breast cancer and increases breast cancer cell malignancy. Here, we examined the cellular/molecular mechanisms underlying this association, aiming to identify new molecular tools to improve diagnosis, prognosis or therapy. A gene expression array comparing sst5TMD4 stably-transfected MCF-7 cells and their controls (empty-plasmid) revealed the existence of profound alterations in the expression of genes involved in key tumoral processes, such as cell survival or angiogenesis. Moreover, sst5TMD4-overexpressing MCF-7 and MDA-MB-231 cells demonstrated increased expression/production of pro-angiogenic factors and enhanced capacity to form mammospheres. Consistently, sst5TMD4-expressing MCF-7 cells induced xenografted tumors with higher VEGF levels and elevated number of blood vessels. Importantly, sst5TMD4 was expressed in a subset of breast cancers, where it correlated with angiogenic markers, lymphatic metastasis, and reduced disease-free survival. These results, coupled to our previous data, support a relevant role of sst5TMD4 in the angiogenic process and reinforce the role of sst5TMD4 in breast cancer malignancy and metastatic potential, supporting its possible utility to develop new molecular biomarkers and drug therapies for these tumors.

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.

Somatostatin analogs for gastric carcinoids: For many, but not all

Gastric carcinoids (GCs) are classified as: type I, related to hypergastrinemia due to chronic atrophic gastritis (CAG), type II, associated with Zollinger-Ellison syndrome in multiple endocrine neoplasia type 1, and type III, which is normogastrinemic. The management of type-I gastric carcinoids (GC1s) is still debated, because of their relatively benign course. According to the European Neuroendocrine Tumor Society guidelines endoscopic resection is indicated whenever possible; however, it is not often feasible because of the presence of a multifocal disease, large lesions, submucosal invasion or, rarely, lymph node involvement. Therefore, somatostatin analogs (SSAs) have been proposed as treatment for GC1s in view of their antisecretive, antiproliferative and antiangiogenic effects. However, in view of the high cost of this therapy, its possible side effects and the relatively benign course of the disease, SSAs should be reserved to specific subsets of “high risk patients”, i.e., those patients with multifocal or recurrent GCs. Indeed, it is reasonable that, after the development of a gastric neuroendocrine neoplasm in patients with a chronic predisposing condition (such as CAG), other enterochromaffin-like cells can undergo neoplastic proliferation, being chronically stimulated by hypergastrinemia. Therefore, definite indications to SSAs treatment should be established in order to avoid the undertreatment or overtreatment of GCs.

Construction of an expression vector for production and purification of human somatostatin in Escherichia coli

Somatostatin/growth hormone-inhibiting hormone is the peptide that inhibits secretion of somatotropin/growth hormone. Solid-phase synthesis methods are being currently used to produce somatostatin. Recombinant peptide synthesis is widely described for the production of small proteins and peptides; however, the production at industrial scale of peptides for biopharmaceutical applications is limited for economic reasons. Here, we propose the use of a new pGB-SMT plasmid to produce Somatostatin, as a C-terminal fusion protein with a Kluyveromyces lactis β-galactosidase fragment. To facilitate removal of that fragment by CNBr cleavage, a methionine residue was introduced at the N-terminal of the hormone peptide. The use of this construction enables an IPTG-free expression system. The suitability of this procedure has been assessed in a 15 l scale-up experiment yielding almost 300 mg, with purity >99 % and it is being implemented for commercial scale. The plasmid pGB-SMT here described is an alternative option for a cheap and high expression of other short peptide hormones.

Synergistic antitumor activities of docetaxel and octreotide associated with apoptotic-upregulation in castration-resistant prostate cancer

Androgen deprivation therapy has become the fist-line treatment of metastatic prostate cancer; however, progression to castrate resistance disease occurs in the majority of patients. Thus, there is an urgent need for improvements in therapy for castration-resistant prostate cancer. The aims of the present study were to determine the efficacy somatostatin analogue octreotide (OCT) combined with a low dose of docetaxel (DTX) using castration resistant prostate cancer cells and to investigate the involved molecular mechanisms in vitro. The anti-proliferative and synergism potential effects were determined by MTT assay. Induction of apoptosis was analyzed employing annexing V and propidium iodide staining and flow cytometry. VEGFA, CASP9, CASP3 and ABCB1 gene expression was evaluated by RT-PCR and Q-RT-PCR analysis. OCT in combination with DTX treatments on DU145 cell migration was also evaluated. Investigation revealed that combined administration of DTX and OCT had significant, synergistically greater cytotoxicity than DTX or OCT treatment alone. The combination of the two drugs caused a more marked increase in apoptosis and resulted in greater suppression of invasive potential than either individual agent. There was obvious increase in caspase 3 expression in the OCT alone and two-drug combined treatment groups, however, VEGFA expression was markedly suppressed in them. These results support the conclusion that somatostatin analogues combined with docetaxel may enhance the chemotherapy efficacies through multiple mechanisms in castration-resistant PCa cell line. This work provides a preclinical rationale for the therapeutic strategies to improve the treatment in castrate resistance disease.

An expression signature of the angiogenic response in gastrointestinal neuroendocrine tumours: correlation with tumour phenotype and survival outcomes

Background:

Gastroenteropancreatic neuroendocrine tumours (GEP-NETs) are heterogeneous with respect to biological behaviour and prognosis. As angiogenesis is a renowned pathogenic hallmark as well as a therapeutic target, we aimed to investigate the prognostic and clinico-pathological role of tissue markers of hypoxia and angiogenesis in GEP-NETs.

Methods:

Tissue microarray (TMA) blocks were constructed with 86 tumours diagnosed from 1988 to 2010. Tissue microarray sections were immunostained for hypoxia inducible factor 1α (Hif-1α), vascular endothelial growth factor-A (VEGF-A), carbonic anhydrase IX (Ca-IX) and somatostatin receptors (SSTR) 1–5, Ki-67 and CD31. Biomarker expression was correlated with clinico-pathological variables and tested for survival prediction using Kaplan–Meier and Cox regression methods.

Results:

Eighty-six consecutive cases were included: 51% male, median age 51 (range 16–82), 68% presenting with a pancreatic primary, 95% well differentiated, 51% metastatic. Higher grading (P=0.03), advanced stage (P<0.001), high Hif-1α and low SSTR-2 expression (P=0.03) predicted for shorter overall survival (OS) on univariate analyses. Stage, SSTR-2 and Hif-1α expression were confirmed as multivariate predictors of OS. Median OS for patients with SSTR-2+/Hif-1α-tumours was not reached after median follow up of 8.8 years, whereas SSTR-2-/Hif-1α+ GEP-NETs had a median survival of only 4.2 years (P=0.006).

Conclusion:

We have identified a coherent expression signature by immunohistochemistry that can be used for patient stratification and to optimise treatment decisions in GEP-NETs independently from stage and grading. Tumours with preserved SSTR-2 and low Hif-1α expression have an indolent phenotype and may be offered less aggressive management and less stringent follow up.

The case of a patient affected by primary gliosarcoma and neuroendocrine pancreatic cancer with prolonged survival

Primary gliosarcoma (PGS) is a rare neoplasm with a poor prognosis. It is considered as a variant of glioblastoma multiforme (GBM) and as a grade IV neoplasm. There is little evidence on the optimal therapy for this disease: treatment of PGS includes surgery, radiotherapy and chemotherapy, and often the same treatment used for GBM is employed for PGS. Several studies have demonstrated that somatostatin receptors are overexpressed in gliomas; somatostatin analogues could therefore also be employed in this mixed form but to date the experience reported in the literature is unclear and there are no studies about the use of these agents in PGS. We present the case of a patient affected by both PGS and neuroendocrine pancreatic cancer. The case is interesting for the prolonged survival and for the stabilization of disease obtained during therapy with somatostatin analogues.

Digestive neuroendocrine tumors (DNET): the era of targeted therapies

Neuroendocrine tumors (NETs) are a heterogeneous group of malignancies. Therapeutic options depend on location of the primitive tumor, its expandability, its hormonal symptoms and its differentiation. Though relatively rare, with an increasing incidence and a high prevalence digestive neuroendocrine tumors (DNETs) are ranked just behind colorectal cancer as the most common digestive cancers in developed countries. Three main therapeutic axes have been individualized in the field of well-differentiated DNETs (corresponding to grades 1 and 2 of new WHO classification 2010), firstly, antitumor activity of somatostatin analogs, particularly in slowly progressive metastatic DNETs with limited hepatic invasion, secondly, targeting angiogenesis in these hypervascular tumors and thirdly targeting the mTOR pathway involved in DNETs carcinogenesis. As a consequence of two major randomized phase III trials in 2011, sunitinib and everolimus have been considered as new therapeutic options for well-differentiated, advanced and progressive pancreatic NETs. For everolimus, another phase III study, although non-significant with the chosen criteria, showed effectiveness notably against small intestine NETs. These targeted therapies are new therapeutic weapons in management of well-differentiated DNETs, but its exact role in care strategy, in comparison with other treatments (somatostatin analogs, chemo-embolization, chemotherapy...) deserves to be precise in the future.

Somatostatin analogs regress endometriotic implants in rats by decreasing implant levels of vascular endothelial growth factor and matrix metaloproteinase 9

OBJECTIVE

To examine the effect of somatostatin analogs on surgically induced endometriosis in rat models.

STUDY DESIGN

Endometrial tissue was implanted onto the abdominal peritoneum of 26 rats that were randomized into 3 groups. The rats in group 1(n = 9) were subcutaneously administered with 0.02 mg/kg/d of octreotide (a short-acting analog)for 28 days . The rats in group 2 (n = 8) were subcutaneously injected with 20 mg/kg of a single dose of a long-acting analogue lanreotide The rats in group 3 were given no medication and served as controls (n = 9).

RESULTS

Mean volume and histologic score of implants in groups 1 (P < .01 and P < .05, respectively) and 2 (P < .01and P < .05, respectively) were significantly lower than that in group 3. There were significant reductions in vascular endothelial growth factor (VEGF) and matrix metalloproteinase 9 (MMP-9) immunoreactivities in group 1 (0.67 ± 0.50 and 1.22 ± 0.44, respectively; both P < .01) and group 2 (0.71 ± 0.48 and 0.86 ± 0.69, respectively; both P < .01) when compared with the control group (1.78 ± 0.83 and 2.11 ± 0.78, respectively).

CONCLUSION

Somatostatin analogs has regressed significantly the size of the endometriotic implants and caused atrophy of these lesions in rats by decreasing explant levels of VEGF and MMP-9.

Somatostatin and somatostatin analogues reduce PDGF-induced endometrial cell proliferation and motility

BACKGROUND

Endometriosis is characterized by ectopic implantation of endometrial cells, which show increased proliferation and migration. Somatostatin (SST) and its analogues inhibit normal and cancer cell growth and motility through the SST receptors, sst1-5. Cortistatin (CST), which displays high structural and functional homology with SST, binds all ssts, as well as MrgX2. Our objective was to investigate the gene expression of the SST/CST system and to determine the effect of SST and its analogues on platelet-derived growth factor (PDGF)-induced proliferation and motility in telomerase-immortalized human endometrial stromal cell (T HESC) line and in primary endometrial stromal cell (ESCs) isolated from human endometriotic tissues.

METHODS

Ectopic endometrial tissues were collected from women (n= 23) undergoing laparoscopic surgery for endometriosis (Stage III/IV). Gene expression was evaluated by real-time PCR, cell motility by wound healing assay, protein expression and β-actin rearrangement by immunofluorescence, cell proliferation by the Alamar blue assay and ERK1/2 and Akt phosphorylation by western blot.

RESULTS

Human endometriotic tissues, primary ESCs and T HESCs expressed SST, CST and ssts. SST, its analogues SOM230 and octreotide, as well as CST, counteracted PDGF-induced proliferation and migration in both ESCs and T HESCs. SST also inhibited vascular endothelial growth factor and metalloprotease-2 mRNA expression, and reduced basal and PDGF-induced ERK1/2 phosphorylation.

CONCLUSION

These results indicate that the SST/CST system is expressed in endometriotic tissues and cells. The inhibitory effects of SST and its analogues on PDGF-induced proliferation and motility suggest that these peptides may represent promising tools in the treatment of endometriosis.

Long acting somatostatin analogues in combination to antineoplastic agents in the treatment of small cell lung cancer patients

BACKGROUND

Long acting somatostatin analogues combined with platinum analogues have demonstrated an antiproliferative effect on growth of human SCLC xenographs.

METHOD

130 previously untreated SCLC patients--54 with limited disease (LD) and positive somatostatin receptors were included in the study. All patients performed 111In-Octreotide scanning before chemotherapy (CHT), every 3 months and up to 4 times. All patients were treated with paclitaxel 190 mg/m2+carboplatin AUC=5.5 for up to 6 cycles. 47/130 patients (Group A, control group) received only CHT. Forty eight hours after each CHT 43/130 patients (Group B) were also administered 30 mg somatuline® (lanreotide) by a single subcutaneous (s.c.) injection to stimulate somatostatin receptors (SSTRS) for 2 weeks. 40/130 patients (Group C) received 60 mg somatuline® autogel to stimulate SSTRS for 4 weeks. Patients in Groups A and B after the completion of the CHT continued maintenance therapy with somatuline. NSE, IGF1, VEGFA, VEGFC, VEGFR2, HER2 levels were monitored. In histological samples Bcl-2 and VEGF were also explored by immunohistochemistry.

RESULTS

No statistically significant differences were observed between the 3 Groups regarding LD and extensive disease (ED) patient ratios, age and PS. Group B had a survival benefit in comparison to Groups A and C (p=0.029). LD patients of Group B had a significant benefit compared to Groups A and C (p=0.012, Breslow test). In LD Group B had a significant longer TTP (p=0.02) in comparison to Groups A and C. Adverse effects had no statistically significant difference between the Groups and toxicity was well managed.

INTERPRETATION

Long acting somatostatin analogues could be used as an additive therapy in combination to antineoplastic agents in patients positive for somatostatin receptors. A dose of 30 mg improved survival only in LD SCLC patients.

Near-infrared molecular imaging of tumors via chemokine receptors CXCR4 and CXCR7

The chemokine CXCL12/SDF-1 and its receptors CXCR4 and CXCR7 play a major role in tumor invasion, proliferation and metastasis. Since both receptors are overexpressed on distinct tumor cells and on the tumor vasculature, we evaluated their potential as targets for detection of cancers by molecular imaging. We synthesized conjugates of CXCL12 and the near-infrared (NIR) fluorescent dye IRDye(®)800CW, tested their selectivity, sensitivity and biological activity in vitro and their feasibility to visualize tumors in vivo. Purified CXCL12-conjugates detected in vitro as low as 500 A764 human glioma cells or MCF-7 breast cancer cells that express CXCR7 alone or together with CXCR4. Binding was time- and concentration-dependent, and the label could be competitively displaced by the native peptide. Control conjugates with bovine serum albumin or lactalbumin failed to label the cells. In mice, the conjugate distributed rapidly. After 1-92 h, subcutaneous tumors of human MCF-7 and A764 cells in immunodeficient mice were detected with high sensitivity. Background was observed in particular in liver within the first 24 h, but also skull and hind limbs yielded some background. Overall, fluorescent CXCL12-conjugates are sensitive and selective probes to detect solid and metastatic tumors by targeting tumor cells and tumor vasculature.

Serum vascular endothelial growth factor (VEGF) is elevated in GH deficient adults

OBJECTIVE

GHD adults exhibit a number of adverse surrogate markers of vascular risk culminating in excess vascular morbidity and mortality. Vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMPs) have been implicated in the pathogenesis of a number of vascular morbidities. Furthermore, serum levels decrease following GH replacement in GHD adults, though it remains unclear if levels are significantly elevated in untreated individuals.

DESIGN

A cross-sectional case-control study.

METHODS

We measured fasting serum VEGF, MMP2, and MMP9 in 27 patients with GHD, 24 with partial GHD (GHI), and 25 sex- and age-matched controls.

RESULTS

GHD (483±334 vs 326±180ng/l, P=0.04), but not GHI (354±192 vs 326±180ng/l, P=n/s) adults had significantly elevated VEGF levels compared with controls. Neither MMP2, nor MMP9 levels were elevated in the patient groups. Serum VEGF levels correlated positively with LDL-cholesterol (R=0.34, P=0.004) and serum MMP9 values (R=0.36, P=0.002), and negatively with IGF-I values, however, no correlation was observed with MMP2. Multiple regression analysis with VEGF levels as the dependent variable, and age, gender, % fat mass, LDL-C, insulin and IGF-I as independent variables revealed VEGF levels to be dependent on LDL-C alone (P=0.003, R=0.36).

CONCLUSION

GHD adults have elevated VEGF levels, which correlate with MMP9 levels. Both VEGF and MMP9 are associated with vascular pathologies and may provide insight in to the pathophysiological mechanisms underlying the increased vascular morbidity and mortality observed in GHD adults.

Inhibition of tumor growth by quercetin with increase of survival and prevention of cachexia in Walker 256 tumor-bearing rats

Quercetin, a flavonoid abundantly present in fruit, vegetables, wine and tea, has revealed several properties such as antioxidant, antiproliferative and anticancer. Cachexia is a poorly understood syndrome present in already compromised cancer patients, decreasing the quality of life and increasing mortality. Many studies have been performed in an attempt to discover an effective treatment for cachexia, but none of the tested therapies has fulfilled expectations. The objective of the present study was to analyze the effect of quercetin in the therapeutic treatment of cachexia and reversion of tumor growth in rats bearing Walker 256 carcinosarcoma (W256). Rats bearing W256 were treated daily with I.P. quercetin injections, at different doses (10, 15, 25 and 35 mg/kg). The results show that 10 mg/kg quercetin inhibited tumor growth by about 50% (ED(50)) when compared with controls (CTR). Moreover, two animals of this group presented complete tumor regression. Matrix metalloproteinase-2 (MMP-2) activity and vascular endothelial growth factor (VEGF) expression decreased in rats bearing W256 treated with 10 mg/kg quercetin when compared with CTR. Thus, the inhibition of tumor growth, survival increase, decrease of MMP-2 and VEGF levels and reduction of cachexia in animals treated with quercetin strongly support the anticancer function of this flavonoid.

Advances in the therapy of gastroenteropancreatic-neuroendocrine tumours (GEP-NETs)

Neuroendocrine tumours (NET) of the digestive tract comprise a broad range of malignancies. The therapeutic approach to these tumours has not evolved as it did in other tumour types in the last two decades. The deeper knowledge of the underlying molecular biology behind the growth of neuroendocrine cells has brought much information to light. We now know that somatostatin analogues may not only be considered as symptomatic treatment but also as antitumour agents. Sunitinib, a tyrosine kinase (TK) inhibitor with antiangiogenic and antitumoural properties, has been shown to induce significant improvement in progression-free survival in a randomised trial conducted in well-differentiated pancreatic islet-cell NETs. The relevance of the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway seems to be crucial in gastroenteropancreatic (GEP)-NETs. In fact, mTOR inhibitors have shown activity in uncontrolled trials, and large, randomised trial results will be available shortly. In this article, we summarise the most recent available data on medical therapy for GEPNETs.

The chemokine receptor CXCR7 is highly expressed in human glioma cells and mediates antiapoptotic effects

The chemokine CXCL12/stromal cell-derived factor-1 and its receptor CXCR4 play a major role in tumor invasion, proliferation, and metastasis. Recently, CXCR7 was identified as a novel, alternate receptor for CXCL12 and CXCL11/I-TAC. Because both chemokines are expressed abundantly in human astrocytomas and glioblastomas, we investigated the occurrence and function of both receptors in astroglial tumors. In situ, CXCR7 is highly expressed on tumor endothelial, microglial, and glioma cells whereas CXCR4 has a much more restricted localization; CXCL12 is often colocalized with CXCR7. CXCR7 transcription in tumor homogenates increased with malignancy. In vitro, CXCR7 was highly expressed in all glioma cell lines investigated whereas CXCR4 was only scarcely transcribed on one of eight lines. In contrast, a tumor stem-like cell line preferentially expressed CXCR4 which diminished upon differentiation, whereas CXCR7 increased drastically. Stimulation of CXCR7-positive glioma cells (CXCR4- and CXCR3-negative) by CXCL12 induced transient phosphorylation of extracellular signal-regulated kinases Erk1/2, indicating that the receptor is functionally active. The phosphoinositide-specific phospholipase C inhibitor U73122 effectively inhibited Erk activation and suggests that the mitogen-activated protein kinase pathway is activated indirectly. Whereas proliferation and migration were little influenced, chemokine stimulation prevented camptothecin- and temozolomide-induced apoptosis. The selective CXCR7 antagonist CCX733 reduced the antiapoptotic effects of CXCL12 as shown by nuclear (Nicoletti) staining, caspase-3/7 activity assays, and cleavage of poly(ADP-ribose) polymerase-1. Thus, CXCR7 is a functional receptor for CXCL12 in astrocytomas/glioblastomas and mediates resistance to drug-induced apoptosis. Whereas CXCR7 is found on "differentiated" glioma cells, the alternate receptor CXCR4 is also localized on glioma stem-like cells.

A randomized, double-masked controlled clinical trial of Sandostatin long-acting release depot in patients with postsurgical cystoid macular edema

PURPOSE

The purpose of this study was to evaluate the safety and efficacy of octreotide, a somatostatin analog, for treatment of postsurgical cystoid macular edema.

METHODS

Twenty-one patients with chronic, refractory postsurgical cystoid macular edema and Early Treatment Diabetic Retinopathy Study best-corrected visual acuity of 20/25 to 20/400 were randomized 2:1 to 30 mg monthly intramuscular octreotide or placebo. Outcome measures were visual acuity (primary) and macular thickness and fluorescein angiographic leakage (secondary).

RESULTS

Fourteen eyes received octreotide and seven eyes received placebo. Mean duration of cystoid macular edema was 2.65 and 1.99 years for Sandostatin long-acting release and placebo groups, respectively. Visual acuity at 6 months improved > or =2 lines in 7 of 14 eyes (50%) in the treatment group and 0 of 7 eyes in the placebo group (P = 0.046). Improvement in retinal thickening and angiographic leakage occurred in 3 of 13 eyes (23.1%) and 3 of 14 eyes (21.4%) of the treatment group, respectively, and in 1 of 7 eyes (14.3%) (P = 1.0 compared with the treatment group) and 0 of 7 eyes in the placebo group (P = 0.52 compared with the treatment group). The three eyes that improved in all parameters were treated with octreotide.

CONCLUSION

Although there were no statistically significant differences between both groups in retinal thickening or angiographic leakage, octreotide-treated patients were more likely to experience a > or =2-line improvement in visual acuity. However, this observation cannot be generalized because of the small sample size.

Differential efficacy of SSTR1, -2, and -5 agonists in the inhibition of C6 glioma growth in nude mice

Somatostatin receptors (SSTR1-5) mediate antiproliferative effects. In C6 rat glioma cells, somatostatin is cytostatic in vitro via phosphotyrosine phosphatase-dependent inhibition of ERK1/2 activity mediated by SSTR1, -2, and -5. Here we analyzed the effects of SSTR activation on C6 glioma growth in vivo and the intracellular mechanisms involved, comparing somatostatin effects with selective agonists for SSTR1, -2, and -5 (BIM-23745, BIM-23120, BIM-23206) or receptor biselective compounds (SSTR1 and -2, BIM-23704; and SSTR2 and -5, BIM-23190). Nude mice subcutaneously xenografted with C6 cells were treated with somatostatin, SSTR agonists (50 μg, twice/day), or vehicle. Tumor growth was evaluated every 3 days for 19 days. The intracellular pathways responsible of SSTR effects in vivo were evaluated measuring Ki-67, phospho-ERK1/2, and p27(kip1) expression by immunohistochemistry in sections from explanted tumors. Somatostatin and SSTR1, -2, and -5 agonists strongly inhibited in vivo C6 tumor growth, intratumoral neovessel formation, Ki-67 expression, and ERK1/2 phosphorylation and induced upregulation of p27(Kip1), whereas only a modest activation of caspase-3 was observed. Somatostatin (acting on SSTR1, -2, and -5) displayed the highest efficacy; SSTR5 selective agonist showed a stronger effect than SSTR1 agonist, and SSTR2 agonist was less effective. On the other hand, SSTR1 and -2 agonists maximally reduced tumor neovascularization. The combined activation of SSTR1 and -2 showed a synergistic activity, reaching a higher efficacy than BIM-23206, whereas the simultaneous activation of SSTR2 and -5 resulted in a response resembling SSTR5 effects. Thus the simultaneous activation of different SSTRs inhibits glioma cell proliferation in vivo through both direct cytotostatic and antiangiogenic effects.

In vitro precursor-directed synthesis of polyketide analogues with coenzyme a regeneration for the development of antiangiogenic agents

Polyketide analogues are produced via in vitro reconstruction of a precursor-directed polyketide biosynthetic pathway. Malonyl-CoA synthetase (MCS) was used in conjunction with chalcone synthase (CHS), thereby allowing efficient use of synthetic starter molecules and malonate as extender. Coenzyme-A was recycled up to 50 times. The use of a simple immobilization procedure resulted in up to a 30-fold higher yield of pyrone CHS products than that obtained with the free enzyme solutions.

A somatostatin analogue, octreotide, inhibits the occurrence of second primary tumors and lung metastasis after resection of hepatocellular carcinoma in mice

Occurrence of second primary tumors and metastasis remains the major obstacles to prolonged survival of patients with primary hepatocellular carcinoma (HCC). A somatostatin analogue, octreotide, has been previously reported to inhibit the growth of human HCC xenografts in nude mice through its anti-angiogenic activity. It is therefore important to investigate whether octreotide could prevent second primary hepatomas or distant metastasis following resection of primary HCC. In this study, nude mice, bearing the human HCC xenografts with highly metastatic potential (LCI-D20) in the left liver lobe, underwent tumor resection, and received intraperitoneal administration of octreotide or saline as a control for 35 consecutive days. Compared with the control group, octreotide at the doses of 100 and 200 microg/kg/day significantly inhibited the growth (P < 0.001 and P < 0.001, respectively) and incidence of second primary tumors (P = 0.016 and P = 0.001, respectively), decreased lung metastasis (P < 0.001 and P < 0.001, respectively), and prolonged the life span (P = 0.029 and P = 0.006, respectively). Moreover, intratumoral angiogenesis quantified by microvessel density as well as serum and tissue vascular endothelial growth factor (VEGF) levels were considerably decreased in octreotide-treated animals compared to the control animals. These findings suggest that octreotide may prevent the occurrence of second primary hepatomas and lung metastasis after resection of primary HCC, which may be partially attributed to down-regulation of VEGF and subsequent reduction in tumor angiogenesis. Octreotide administration may be useful as an adjuvant therapy to improve survival of patients with HCC.

VEGFR-3/Flt-4 mediates proliferation and chemotaxis in glial precursor cells

Neuronal and vascular cells share common chemical signals. Vascular endothelial growth factor (VEGF)-C and -D and their receptor VEGFR-3/Flt-4 mediate lymphangiogenesis, but they occur also in the brain. Quantitative RT-PCR of mouse brain tissues and cultivated cells showed that the VEGFR-3 gene is highest transcribed in postnatal brain and in glial precursor cells whereas VEGF-C and -D are variably produced by different neuronal and glial cells. In neurospheres (neural stem cells) VEGFR-3 was induced by differentiation with platelet-derived growth factor (PDGF). In functional studies with an A2B5- and nestin-positive, O4-negative murine glial precursor cell line, VEGF-C and -D stimulated phosphorylation of the kinases Erk1/2; this signal transduction was inhibited by UO126. Both peptides induced the proliferation of glial precursor cells which could be inhibited by UO126. Furthermore, VEGF-D considerably enhanced their migration into an open space in a wound-healing assay. These results show that VEGF-C/-D together with its receptor VEGFR-3 provides an auto-/paracrine growth and chemotactic system for glial precursors in the developing brain.

Somatostatin receptors 1, 2, and 5 cooperate in the somatostatin inhibition of C6 glioma cell proliferation in vitro via a phosphotyrosine phosphatase-eta-dependent inhibition of extracellularly regulated kinase-1/2

Somatostatin inhibits cell proliferation through the activation of five receptors (SSTR1-5) expressed in normal and cancer cells. We analyzed the role of individual SSTRs in the antiproliferative activity of somatostatin in C6 rat glioma cells. Somatostatin dose-dependently inhibited C6 proliferation, an effect mimicked, with different efficacy or potency, by BIM-23745, BIM-23120, BIM-23206 (agonists for SSTR1, -2, and -5) and octreotide. The activation of SSTR3 was ineffective, although all SSTRs are functionally active, as demonstrated by the inhibition of cAMP production. All SSTRs induced cytostatic effects through the activation of the phosphotyrosine phosphatase PTPeta and the inhibition of ERK1/2. For possible synergism between SSTR subtypes, we tested the effects of the combined treatment with two agonists (SSTR1+2 or SSTR2+5) or bifunctional compounds. The simultaneous activation of SSTR1 and SSTR2 slightly increased the efficacy of the individual compounds with an IC50 in between the single receptor activation. SSTR2+5 activation displayed a pattern of response superimposable to that of the SSTR5 agonist alone (low potency and higher efficacy, as compared with BIM-23120). The simultaneous activation of SSTR1, -2, and -5 resulted in a response similar to somatostatin. In conclusion, the cytostatic effects of somatostatin in C6 cells are mediated by the SSTR1, -2, and -5 through the same intracellular pathway: activation of PTPeta and inhibition of ERK1/2 activity. Somatostatin is more effective than the individual agonists. The combined activation of SSTR1 and -2 shows a partial synergism as far as antiproliferative activity, whereas SSTR2 and -5 activation results in a response resembling the SSTR5 effects.

Antitumor effects of somatostatin

Since its discovery three decades ago as an inhibitor of GH release from the pituitary gland, somatostatin has attracted much attention because of its functional role in the regulation of a wide variety of physiological functions in the brain, pituitary, pancreas, gastrointestinal tract, adrenals, thyroid, kidney and immune system. In addition to its negative role in the control of endocrine and exocrine secretions, somatostatin and analogs also exert inhibitory effects on the proliferation and survival of normal and tumor cells. Over the past 15 years, studies have begun to reveal some of the molecular mechanisms underlying the antitumor activity of somatostatin. This review covers the present knowledge in the antitumor effect of somatostatin and analogs and discusses the perspectives of novel clinical strategies based on somatostatin receptor sst2 gene transfer therapy.

Targeting vascular endothelial growth factor in advanced carcinoid tumor: a random assignment phase II study of depot octreotide with bevacizumab and pegylated interferon alpha-2b

PURPOSE

Effective systemic therapy for advanced carcinoid is lacking. The combination of bevacizumab (BEV) and pegylated (PEG) interferon alpha-2b was evaluated among patients with metastatic or unresectable carcinoid tumors.

PATIENTS AND METHODS

Forty-four patients on stable doses of octreotide were randomly assigned to 18 weeks of treatment with bevacizumab or PEG interferon alpha-2b. At disease progression (PD) or at the end of 18 weeks (whichever occurred earlier), patients received bevacizumab plus PEG interferon until progression. Functional computer tomography (CT) scans were performed to measure effect on tumor blood flow.

RESULTS

In the bevacizumab arm, four patients (18%) achieved confirmed partial response (PR), 17 patients (77%) had stable disease (SD), and one patient (5%) had PD. In the PEG interferon arm, 15 patients (68%) had SD and six patients (27%) had PD. Progression-free survival (PFS) rates after 18 weeks of monotherapy were 95% in bevacizumab versus 68% on the PEG interferon arm. The overall median PFS for all 44 patients is 63 weeks. Compared with paired baseline measurements on functional CT scans, we observed a 49% (P < .01) and 28% (P < .01) decrease in tumor blood flow at day 2 and week 18 among patients treated with bevacizumab. No significant changes in tumor blood flow were observed following PEG interferon. PEG interferon alpha-2b treatment was associated with decrease in plasma basic fibroblast growth factor (bFGF; P = .04) and increase in plasma interleukin-18 (IL-18; P < .01). No significant changes in bFGF or IL-18 following treatment with bevacizumab were observed.

CONCLUSION

Bevacizumab therapy resulted in objective responses, reduction of tumor blood flow, and longer PFS in patients with carcinoid than PEG interferon treatment.

Trophic factors in the carotid body

The aim of the present study is to provide a review of the expression and action of trophic factors in the carotid body. In glomic type I cells, the following factors have been identified: brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor, artemin, ciliary neurotrophic factor, insulin-like growth factors-I and -II, basic fibroblast growth factor, epidermal growth factor, transforming growth factor-alpha and -beta1, interleukin-1beta and -6, tumour necrosis factor-alpha, vascular endothelial growth factor, and endothelin-1 (ET-1). Growth factor receptors in the above cells include p75LNGFR, TrkA, TrkB, RET, GDNF family receptors alpha1-3, gp130, IL-6Ralpha, EGFR, FGFR1, IL1-RI, TNF-RI, VEGFR-1 and -2, ETA and ETB receptors, and PDGFR-alpha. Differential local expression of growth factors and corresponding receptors plays a role in pre- and postnatal development of the carotid body. Their local actions contribute toward producing the morphologic and molecular changes associated with chronic hypoxia and/or hypertension, such as cellular hyperplasia, extracellular matrix expansion, changes in channel densities, and neurotransmitter patterns. Neurotrophic factor production is also considered to play a key role in the therapeutic effects of intracerebral carotid body grafts in Parkinson's disease. Future research should also focus on trophic actions on carotid body type I cells by peptide neuromodulators, which are known to be present in the carotid body and to show trophic effects on other cell populations, that is, angiotensin II, adrenomedullin, bombesin, calcitonin, calcitonin gene-related peptide, cholecystokinin, erythropoietin, galanin, opioids, pituitary adenylate cyclase-activating polypeptide, atrial natriuretic peptide, somatostatin, tachykinins, neuropeptide Y, neurotensin, and vasoactive intestinal peptide.

In vitro antiangiogenic activity of selective somatostatin subtype-1 receptor agonists

BACKGROUND

Endothelial cells of human blood vessels (arteries and veins) show high levels of somatostatin subtype-1 receptor (sst(1)). The aim of the present study is to investigate the inhibitory effects of novel somatostatin analogs, highly selective for human sst(1), on in vitro angiogenesis and their modulation of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 (VEGFR-2) expression.

MATERIALS AND METHODS

Somatostatin analogs BIM-23745 and BIM-23926 were tested for their ability to prevent proliferation and migration of human endothelial HMEC-1 cells, to modulate VEGF and VEGFR-2 expression and to inhibit sprouting of microvessels from cultured human placental vessel explants in fibrin matrix for 28 days.

RESULTS

The somatostatin sst(1 )receptor-selective agonists, BIM-23745 and BIM-23926 showed a suppression of endothelial proliferation (e.g. 10(-6) M BIM-23475, 40.0 +/- 2.1% vs. 100% of controls; 10(-7) M BIM-23926, 55.3 +/- 3.3% vs. 100% of controls), migration (e.g. 10(-7) M BIM-23475, 35.0 +/- 1.56% vs. 100% of controls; 10(-7) M BIM-23926, 53.7 +/- 1.77% vs. 100% of controls) and microvessel sprouting (e.g. 10(-8) M BIM-23475, 42.8 +/- 5.6% vs. 100% of controls; 10(-7) M BIM-23926, 17.2 +/- 11.8% vs. 100% of controls). A small but significant percentage of cells exposed to BIM-23745 and BIM-23926 for 24 h and for 72 h presented typical apoptotic morphology. Moreover, both the analogs significantly inhibit VEGF and VEGFR-2 gene expression in endothelial cells grown for 144 h in a fibrin matrix and the VEGF secretion in conditioned media.

CONCLUSIONS

The inhibition of endothelial activities suggests potential therapeutic utility for administration of somatostatin sst(1 )receptor-selective agonists in the proliferative diseases involving angiogenesis.

Nonclassic Endogenous Novel Regulators of Angiogenesis

Angiogenesis, the process through which new blood vessels arise from preexisting ones, is regulated by several "classic" factors, among which the most studied are vascular endothelial growth factor (VEGF) and fibroblast growth factor-2 (FGF-2). In recent years, investigations showed that, in addition to the classic factors, numerous endogenous peptides play a relevant regulatory role in angiogenesis. Such regulatory peptides, each of which exerts well-known specific biological activities, are present, along with their receptors, in the blood vessels and may take part in the control of the "angiogenic switch." An in vivo and in vitro proangiogenic effect has been demonstrated for erythropoietin, angiotensin II (ANG-II), endothelins (ETs), adrenomedullin (AM), proadrenomedullin N-terminal 20 peptide (PAMP), urotensin-II, leptin, adiponectin, resistin, neuropeptide-Y, vasoactive intestinal peptide (VIP), pituitary adenylate cyclase-activating polypeptide (PACAP), and substance P. There is evidence that the angiogenic action of some of these peptides is at least partly mediated by their stimulating effect on VEGF (ANG-II, ETs, PAMP, resistin, VIP and PACAP) and/or FGF-2 systems (PAMP and leptin). AM raises the expression of VEGF in endothelial cells, but VEGF blockade does not affect the proangiogenic action of AM. Other endogenous peptides have been reported to exert an in vivo and in vitro antiangiogenic action. These include somatostatin and natriuretic peptides, which suppress the VEGF system, and ghrelin, that antagonizes FGF-2 effects. Investigations on "nonclassic" regulators of angiogenesis could open new perspectives in the therapy of diseases coupled to dysregulation of angiogenesis.

Clinical and In vitro Studies of Imatinib in Advanced Carcinoid Tumors

PURPOSE

Effective systemic therapy options for carcinoid tumors are lacking. We conducted in vitro studies and a phase II clinical trial to explore the activity of imatinib in carcinoid tumors.

EXPERIMENTAL DESIGN

Cells of the human bronchial carcinoid cell line NCI-H727 and the human pancreatic carcinoid cell line BON-1 were treated with increasing concentrations of imatinib using standard procedures to assess in vitro growth-inhibitory activity. A clinical trial using a two-stage phase II design to assess the response rate and safety profile of imatinib at a dose of 400 mg given twice daily in patients with advanced carcinoid tumors was completed.

RESULTS

In both cell lines, there was a dose- and time-dependent cytotoxic effect. The clinical trial enrolled 27 evaluable patients. Median duration on trial was 16 weeks. One patient had a partial response, 17 had stable disease, and 9 had progressive disease by the Response Evaluation Criteria in Solid Tumors criteria. Median progression-free survival time was 24 weeks. Median overall survival is 36 months. Seven patients who achieved a biochemical response had a superior progression-free survival time compared with patients without biochemical response (115 weeks compared with 24 weeks; P = 0.003). An increase in plasma basic fibroblast growth factor was associated with a shorter progression-free survival duration (P = 0.02).

CONCLUSIONS

Our data suggest that imatinib is active in vitro and has a modest clinical activity in carcinoid patients. Changes in tumor markers may help select patients who are likely to benefit from therapy.

Cannabinoid receptors in human astroglial tumors

In animal models, cannabinoids are reported to inhibit the growth of tumors, including gliomas. These effects have been claimed to be mediated via cannabinoid receptors 1 and 2 (CB1, CB2). To elucidate a possible relevance for treatment of human gliomas, we investigated receptor subtype expression in surgical material of solid human astrocytomas, gliomas and cultivated glioma cells by quantitative reverse transcriptase polymerase chain reaction, western blot and immunohistochemistry and assayed their functionality. In normal brain, cultivated glioma cells and solid tumors, CB1 mRNA was expressed to a much greater extent than CB2, which in some samples was even undetectable. Expression of both receptor subtypes was unrelated to malignancy, varied between patients, and was not significantly increased in relation to normal brain tissues. In normal brain, CB1 protein was localized on astroglial and other cell types; in gliomas, it was found on astroglial/glioma cells. CB2 protein was detected on microglial cells/macrophages but rarely on astroglial cells. Functionally, CB1 receptor agonists reduced elevated cyclic AMP levels and slightly reduced proliferation of glioma cells in vitro, but did not induce apoptosis. We conclude that cannabinoid therapy of human gliomas targets not only receptors on tumor, but also on other cell types. Therefore, complex and potential side-effects should be considered carefully.

Flavonoids and vitamin E reduce the release of the angiogenic peptide vascular endothelial growth factor from human tumor cells

Neoangiogenesis is required for tumor development and progression. Many solid tumors induce vascular proliferation by production of angiogenic factors, prominently vascular endothelial growth factor (VEGF). Because nutrition is a causative factor for tumor prevention and promotion, we determined whether secondary plant constituents, i.e., flavonoids, tocopherols, curcumin, and other substances regulate VEGF in human tumor cells in vitro. VEGF release (concurrent with synthesis) from MDA human breast cancer cells and, for comparison, U-343 and U-118 glioma cells was measured by ELISA. Of 21 compounds tested, 9 showed significant inhibitory activity at 0.1 micromol/L in MDA human breast cancer cells. The rank order of inhibitory potency was naringin > rutin > alpha-tocopheryl succinate (alpha-TOS) > lovastatin > apigenin > genistein > alpha-tocopherol >or= kaempferol > gamma-tocopherol; chrysin and curcumin were inactive except at a concentration of 100 micromol/L. Glioma cells were similarly sensitive, with U343 more than U118, especially for alpha-TOS and tocopherols. Among the tocopherol derivatives, alpha-TOS (0.1 micromol/L) was the most effective in reducing VEGF release. Overall, the glycosylated flavonoids (i.e., naringin, a constituent of citrus fruits, and rutin, a constituent of cranberries) induced the greatest response to treatment at the lowest concentration in MDA human breast cancer cells. Inhibition of VEGF release by flavonoids, tocopherols, and lovastatin in these models of neoplastic cells suggests a novel mechanism for mammary cancer prevention.

Inhibitory effects of small interfering RNA on expression of somatostatin gener

AIM: To research inhibitory effects of small interfering RNA (siRNA) on the expression of somatostatin gene.

METHODS: According to the gene sequence of somatostatin in GenBank, we designed the siRNA-targeted templates and synthesized siRNA using T7 RiboMAX Express RNAi System in vitro. The obtained siRNA was then transfected into gastric cancer cell line SGC-7901. Reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemical techniques were used to detect the expression of somatostatin at both mRNA and protein levels.

RESULTS: The target siRNA with a length of 21 bp was successfully synthesized. Before transfection, somatostatin was strongly and positively expressed in gastric cancer cell line SGC-7901, locating at the cytoplasm. Forty-eight hours after transfection , somatostatin expression was markedly inhibited and the inhibitory rate in siRNA-transfected cells was significantly higher than that in the cells transfected with empty vector and non-transfected cells (49.71% ± 0.056% vs 10.49% ± 0.021%, 0%, both P < 0.01).

CONCLUSION: siRNA can inhibit the expression of somatostatin specifically.

Angiogenesis in gliomas: biology and molecular pathophysiology

Glioblastoma multiforme (GBM) is characterized by exuberant angiogenesis, a key event in tumor growth and progression. The pathologic mechanisms driving this change and the biological behavior of gliomas remain unclear. One mechanism may involve cooption of native blood vessels by glioma cells inducing expression of angiopoietin-2 by endothelial cells. Subsequently, vascular apoptosis and involution leads to necrosis and hypoxia. This in turn induces angiogenesis that is associated with expression of hypoxia-inducible factor (HIF)-1alpha and vascular endothelial growth factor (VEGF) in perinecrotic pseudopalisading glioma cells. Here we review the molecular and cellular mechanisms implicated in HIF-1-dependent and HIF-1-independent glioma-associated angiogenesis. In GBMs, both tumor hypoxia and genetic alterations commonly occur and act together to induce the expression of HIF-1. The angiogenic response of the tumor to HIF-1 is mediated by HIF-1-regulated target genes leading to the upregulation of several proangiogenic factors such as VEGF and other adaptive response molecules. Understanding the roles of these regulatory processes in tumor neovascularization, tumor growth and progression, and resistance to therapy will ultimately lead to the development of improved antiangiogenic therapies for GBMs.

Angiogenesis in gliomas: imaging and experimental therapeutics

Much of the interest in angiogenesis and hypoxia has led to investigating diagnostic imaging methodologies and developing efficacious agents against angiogenesis in gliomas. In many ways, because of the cytostatic effects of these agents on tumor growth and tumor-associated endothelial cells, the effects of therapy are not immediately evident. Hence finding clinically applicable imaging tools and pathologic surrogate markers is an important step in translating glioma biology to therapeutics. There are a variety of strategies in the approach to experimental therapeutics that target the hypoxia-inducible factor pathway, the endogenous antiangiogenic and proangiogenic factors and their receptors, adhesion molecules, matrix proteases and cytokines, and the existing vasculature. We discuss the rationale for antiangiogenesis as a treatment strategy, the preclinical and clinical assessment of antiangiogenic interventions and finally focus on the various treatment strategies, including combining antiangiogenic drugs with radiation and chemotherapy.

TGF-β, Neuronal Stem Cells and Glioblastoma

Transforming growth factor beta (TGF-beta) signaling leads to a number of biological end points involving cell growth, differentiation, and morphogenesis. Typically, the cellular effect accompanies an induction of mesodermal cell fate and inhibition of neural cell differentiation. However, during pathological conditions, these defined effects of TGF-beta can be reversed; for example, the growth-inhibitory effect is replaced with its tumor promoting ability. A multitude of factors and cross-signaling pathways have been reported to be involved in modulating the dual effects of TGF-beta. In this review, we focus on the potential role of TGF-beta signal transduction during development of neural progenitor cells and its relation to glioblastoma development from neural stem cells.

Endocrine tumours of the gastrointestinal tract. Somatostatin receptors as tools for diagnosis and therapy: molecular aspects

Somatostatin is a neuropeptide that acts as an endogenous inhibitor of various cellular functions including endocrine and exocrine secretions and the proliferation of normal and tumour cells. Its action is mediated by a family of G-protein-coupled receptors (sst1-sst5) that are widely distributed in normal and tumour cells. Gastroenteropancreatic endocrine tumours express multiple somatostatin receptors, sst2 being clearly predominant. These receptors represent the molecular basis for the clinical use of somatostatin analogues in the treatment of endocrine tumours and their in vivo localisation. This review covers current knowledge in somatostatin receptor biology and signalling.