Stimulation of proliferation of U138-MG glioblastoma cells by gastrin-releasing peptide in combination with agents that enhance cAMP signaling

Chitosan-coated magnetic graphene oxide for targeted delivery of doxorubicin as a nanomedicine approach to treat glioblastoma

In this study, magnetic graphene oxide (mGO) was first prepared and modified with chitosan to prepare chitosan-coated mGO (mGOC). Gastrin-releasing peptide (GRP)-conjugated mGOC (mGOCG) was then prepared from mGOC. The chemo drug doxorubicin (DOX) was adsorbed to mGOCG surface for dual active/magnetic targeted drug delivery. The DOX loading to mGOCG is 1.71 mg/mg, and drug release is pH-sensitive to facilitate drug delivery in endosomes. In vitro studies confirmed enhanced mGOCG endocytosis by U87 glioblastoma cells, with which enhanced cytotoxicity towards cancer cells could be achieved. This could be revealed from the drastically reduced half-maximal inhibitory concentration of mGOCG/DOX compared with DOX and mGOC/DOX. Furthermore, mGOCG/DOX can be localized under the influence of a magnetic field (MF) to exert this cytotoxic effect. An orthotopic brain tumor model by implanting U87 cells in the intracranial area of BALB/c nude mice was used to study the in vivo anti-tumor efficacy by intravenous injection of different samples and followed with bioluminescence imaging. The tumor size in the mGOCG/DOX + MF group demonstrated the best potency to suppress tumor growth and prolong animal survival time compared with mGOCG/DOX, mGOC/DOX, or DOX groups, indicating this new dual-targeting delivery system for DOX can effectively treat glioblastoma.

Interactions of Nanoscale Self-Assembled Peptide-Based Assemblies with Glioblastoma Cell Models and Spheroids

Peptide nanoassemblies have garnered remarkable importance in the development of novel nanoscale biomaterials for drug delivery into tumor cells. Taking advantage of receptor mediated recognition of two known peptides, angiopep-2 (TFFYGGSRGKRNNFKTEEY) and A-COOP-K (ACGLSGLC10 VAK) that bind to the over-expressed receptors low density lipoprotein (LRP-1) and fatty acid binding protein (FABP3) respectively, we have developed new peptide conjugates by combining the anti-inflammatory, antitumor compound azelaic acid with angiopep-2, which efficiently self-assembled into nanofibers. Those nanofibers were then functionalized with the A-COOP-K sequence and formed supramolecular hierarchical structures that were found to entrap the chemotherapeutic drug doxorubicin efficaciously. Furthermore, the nanoassemblies were found to release the drug in a dose-dependent manner and showed a stepwise increase over a period of 2 weeks under acidic conditions. Two cell lines (U-87-MG and U-138-MG) were utilized as models for glioblastoma cells grown in the presence of serum and under serum-free conditions to mimic the growth conditions of natural tumors. The drug entrapped assemblies were found to inhibit the cell proliferation of both U-87 and U-138MG glioblastoma cells. Three dimensional spheroids of different sizes were grown to mimic the tumors and evaluate the efficacy of drug release and internalization. Our results indicated that the nanoassemblies were found to have higher internalization of DOX and were well-spread throughout the spheroids grown, particularly under serum-free conditions. The nanoassemblies also displayed blood-brain barrier penetration when tested with a multicellular in vitro model. Such self-assembled nanostructures with targeting ability may provide a suitable platform for the development of new peptide-based biomaterials that can provide more insights about the mechanistic approach for drug delivery for not only 2D cell cultures but also 3D tumoroids that mimic the tumor microenvironments.

Development of a time-resolved fluorescence immunoassay based on immunomagnetic beads for gastrin-17

OBJECTIVE

In this study, a novel, simple, and rapid immunoassay for the determination of gastrin-17 (G-17) in human serum was established by combining immunomagnetic beads with time-resolved fluorescence immunoassay (TRFIA).

METHODS

Immunomagnetic beads were coated with anti-G-17 M01 antibody, anti-G-17 M02 antibody was labeled with Eu³⁺ chelates. The concentration of G-17 in the serum was detected with the double-antibody sandwich method.

RESULTS

The limit of background(LOB), limit of detection (LOD), and limit of quantification (LOQ) were 0.09, 0.104, and 0.39 pmol/L, respectively. The detection range of G-17-TRFIA was 0.39-100 pmol/L. The average intra- and inter-assay coefficients of variation (CV) were 5.95%-9.07% and 6.09%-8.14%, respectively. The recoveries for the serum samples ranged from 94.70% to 100.95%. The specificity of our G-17-TRFIA was acceptable. The correlation coefficient between G-17-TRFIA and commercial G-17-ELISA methods was R² = 0.9092.

CONCLUSIONS

A novel G-17-TRFIA detection method was successfully established to provide a reference for the early diagnosis of patients with atrophic gastritis in clinical research.

Magnetic and GRPR-targeted reduced graphene oxide/doxorubicin nanocomposite for dual-targeted chemo-photothermal cancer therapy

Herein, we design a rGO-based magnetic nanocomposite by decorating rGO with citrate-coated magnetic nanoparticles (CMNP). The magnetic rGO (mrGO) was modified by phospholipid-polyethylene glycol to prepare PEGylated mrGO, for conjugating with gastrin-releasing peptide receptor (GRPR)-binding peptide (mrGOG). The anticancer drug doxorubicin (DOX) was bound to mrGO (mrGOG) by π-π stacking for drug delivery triggered by the low pH value in the endosome. The mrGOG showed enhanced photothermal effect under NIR irradiation, endorsing its role for dual targeted DOX delivery. With efficient DOX release in the endosomal environment and heat generation from light absorption in the NIR range, mrGOG/DOX could be used for combination chemo-photothermal therapy after intracellular uptake by cancer cells. We characterized the physico-chemical as well as biological properties of the synthesized nanocomposites. The mrGOG is stable in biological buffer solution, showing high biocompatibility and minimum hemolytic properties. Using U87 glioblastoma cells, we confirmed the magnetic drug targeting effect in vitro for selective cancer cell killing. The peptide ligand-mediated targeted delivery increases the efficiency of intracellular uptake of both nanocomposite and DOX up to ~3 times due to the over-expressed GRPR on U87 surface, leading to higher cytotoxicity. The increased cytotoxicity using mrGOG over mrGO was shown from a decreased IC₅₀ value (0.70 to 0.48 μg/mL) and an increased cell apoptosis rate (19.8% to 47.1%). The IC₅₀ and apoptosis rate changed further to 0.19 μg/mL and 76.8% in combination with NIR laser irradiation, with the photothermal effect supported from upregulation of heat shock protein HSP70 expression. Using U87 tumor xenograft model created in nude mice, we demonstrated that magnetic guidance after intravenous delivery of mrGOG/DOX could significantly reduce tumor size and prolong animal survival over free DOX and non-magnetic guided groups. Augmented with NIR laser treatment for 5 min, the anti-cancer efficacy significantly improves with elevated cell apoptosis and reduced cell proliferation. Together with safety profiles from hematological as well as major organ histological analysis of treated animals, the mrGOG nanocomposite is an effective nanomaterial for combination chemo-photothermal cancer therapy.

Bombesin Receptor Family Activation and CNS/Neural Tumors: Review of Evidence Supporting Possible Role for Novel Targeted Therapy

G-protein-coupled receptors (GPCRs) are increasingly being considered as possible therapeutic targets in cancers. Activation of GPCR on tumors can have prominent growth effects, and GPCRs are frequently over-/ectopically expressed on tumors and thus can be used for targeted therapy. CNS/neural tumors are receiving increasing attention using this approach. Gliomas are the most frequent primary malignant brain/CNS tumor with glioblastoma having a 10-year survival <1%; neuroblastomas are the most common extracranial solid tumor in children with long-term survival<40%, and medulloblastomas are less common, but one subgroup has a 5-year survival <60%. Thus, there is an increased need for more effective treatments of these tumors. The Bombesin-receptor family (BnRs) is one of the GPCRs that are most frequently over/ectopically expressed by common tumors and is receiving particular attention as a possible therapeutic target in several tumors, particularly in prostate, breast, and lung cancer. We review in this paper evidence suggesting why a similar approach in some CNS/neural tumors (gliomas, neuroblastomas, medulloblastomas) should also be considered.

Analysis of serum gastrin-17 and Helicobacter pylori antibody in healthy Chinese population

BACKGROUND

Gastrin-17 (G-17) and Helicobacter pylori (H pylori) antibody are widely used in the screening of gastric diseases, especially in gastric cancer. In this study, we aimed to evaluate the value of G-17 and H pylori antibody in gastric disease screening.

METHODS

Healthy males and females (1368 and 1212, respectively) aged between 21-80 years were recruited for the study. Serum G-17 value was measured using ELISA, and H pylori antibodies were measured using Western blotting. Statistical analyses were performed using the chi-square, Mann-Whitney U, and Kruskal-Wallis H tests.

RESULTS

Serum G-17 level was higher in the H pylori-positive group than in the negative group. Serum G-17 level was higher in the type 1 H pylori-positive group than in the type 2 H pylori-positive group. Further, serum G-17 level was higher in females than in males and showed significant differences among different age-groups, with changes in trend proportional to the age. The positive rate of H pylori infection in all the subjects was 58.29% and did not show a significant difference between males and females. However, it showed significant differences among different age-groups, with the changing trend proportional to the age.

CONCLUSION

Analysis of serum G-17 level and H pylori antibody typing is valuable in gastric disease screening. Every laboratory should establish its own reference interval for G-17 level.

Neuroendocrine regulation of cholangiocarcinoma: A status quo review

Increasing studies have demonstrated that neuroendocrine system is involved in the development and progression of cholangiocarcinoma. The neuroendocrine hormones, neurotransmitters and neuropeptides regulate cholangiocarcinoma via affecting pathophysiology of tumor cells. The developing interaction and interplay between neuroendocrine-associated factors and tumor cells provide novel insights into neural control of tumorigenesis and reveal potential therapeutic effect on patients with cholangiocarcinoma. Herein we reviewed the latest findings and achievements which demonstrate the close interactions between neuroendocrine regulation and progression of cholangiocarcinoma. Also, future therapeutic approaches targeting neuroendocrine-associated factors are discussed which may help improve management and treatment of cholangiocarcinoma.

Gastrin-Releasing Peptide Receptor Knockdown Induces Senescence in Glioblastoma Cells

Glioblastoma multiforme (GBM) is the most aggressive type of brain tumor, characterized by excessive cell proliferation, resistance to apoptosis, and invasiveness. Due to resistance to currently available treatment options, the prognosis for patients with GBM is very dismal. The activation of gastrin-releasing peptide receptors (GRPR) stimulates GBM cell proliferation, whereas GRPR antagonists induce antiproliferative effects in in vitro and in vivo experimental models of GBM. However, the role of GRPR in regulating other aspects of GBM cell function related to tumor progression remains poorly understood, and previous studies have not used RNA interference techniques as tools to examine GRPR function in GBM. Here, we found that stable GRPR knockdown by a lentiviral vector using a short hairpin interfering RNA sequence in human A172 GBM cells resulted in increased cell size and altered cell cycle dynamics consistent with cell senescence. These changes were accompanied by increases in the content of p53, p21, and p16, activation of epidermal growth factor receptors (EGFR), and a reduction in p38 content. These results increase our understanding of GRPR regulation of GBM cells and further support that GRPR may be a relevant therapeutic target in GBM.

68Ga-NOTA-Aca-BBN(7-14) PET/CT in Healthy Volunteers and Glioma Patients

This work was designed to study the safety, biodistribution, and radiation dosimetry of a gastrin-releasing peptide receptor (GRPR)-targeting, (68)Ga-labeled bombesin (BBN) peptide derivative PET tracer, NOTA-Aca-BBN(7-14) (denoted as (68)Ga-BBN) in healthy volunteers and to assess the level of receptor expression in glioma patients.

METHODS

Four healthy volunteers (2 male and 2 female) underwent whole-body PET/CT at multiple time points after a bolus injection of (68)Ga-BBN (111 ± 148 MBq). Regions of interest were drawn manually over major organs, and time-activity curves were obtained. Dosimetry was calculated using the OLINDA/EXM software. Twelve patients with glioma diagnosed by contrast-enhanced MRI underwent PET/CT at 30-45 min after (68)Ga-BBN injection. Within 1 wk afterward, the tumor was surgically removed and immunohistochemical staining of tumor samples against GRPR was performed and correlated with the PET/CT results.

RESULTS

(68)Ga-BBN was well tolerated in all healthy volunteers, with no adverse symptoms being noticed or reported. (68)Ga-BBN cleared rapidly from the circulation and was excreted mainly through the kidneys and urinary tract. The total effective dose equivalent and effective dose were 0.0335 ± 0.0079 and 0.0276 ± 0.0066 mSv/MBq, respectively. In glioma patients, all MRI-identified lesions showed high signal intensity on (68)Ga-BBN PET/CT. SUVmax and SUVmean were 2.08 ± 0.58 and 1.32 ± 0.37, respectively. With normal brain tissue as background, tumor-to-background ratios were 24.0 ± 8.85 and 13.4 ± 4.54 based on SUVmax and SUVmean, respectively. The immunohistochemical staining confirmed a positive correlation between SUV and GRPR expression level (r(2) = 0.71, P < 0.001).

CONCLUSION

(68)Ga-BBN is a PET tracer with favorable pharmacokinetics and a favorable dosimetry profile. It has the potential to evaluate GRPR expression in glioma patients and guide GRPR-targeted therapy of glioma.

Insights into bombesin receptors and ligands: Highlighting recent advances

This following article is written for Prof. Abba Kastin's Festschrift, to add to the tribute to his important role in the advancement of the role of peptides in physiological, as well as pathophysiological processes. There have been many advances during the 35 years of his prominent role in the Peptide field, not only as editor of the journal Peptides, but also as a scientific investigator and editor of two volumes of the Handbook of Biological Active Peptides [146,147]. Similar to the advances with many different peptides, during this 35 year period, there have been much progress made in the understanding of the pharmacology, cell biology and the role of (bombesin) Bn receptors and their ligands in various disease states, since the original isolation of bombesin from skin of the European frog Bombina bombina in 1970 [76]. This paper will briefly review some of these advances over the time period of Prof. Kastin 35 years in the peptide field concentrating on the advances since 2007 when many of the results from earlier studies were summarized [128,129]. It is appropriate to do this because there have been 280 articles published in Peptides during this time on bombesin-related peptides and it accounts for almost 5% of all publications. Furthermore, 22 Bn publications we have been involved in have been published in either Peptides [14,39,55,58,81,92,93,119,152,216,225,226,231,280,302,309,355,361,362] or in Prof. Kastin's Handbook of Biological Active Peptides [137,138,331].

A comprehensive evaluation of fasting serum gastrin-17 as a predictor of diseased stomach in Chinese population

BACKGROUND AND AIM

Fasting serum gastrin-17 (FsG17) is considered as a noninvasive biomarker reflecting the structure and functional status of gastric mucosa, but its clinical utility remains unclear. This study aimed to evaluate FsG17 comprehensively: establish the ranges and cut-off points of FsG17 levels in different gastric diseases, identify their influencing factors, and investigate the accuracy of FsG17 for identifying diseased stomach.

METHODS

The study included 4064 participants from Northern China between 2008 and 2013. FsG17 and serum Helicobacter pylori IgG antibody levels were measured by enzyme-linked immunosorbent assay. Diagnostic accuracy was assessed by receiver operator characteristic curves. Multivariate logistic regression analysis was performed to determine the best predictors of gastric histopathological conditions.

RESULTS

Median FsG17 levels in healthy, non-atrophic, atrophic, and cancerous stomachs were 1.8, 4.0, 3.8, and 6.1 pmol/l, respectively. Age, smoking status, alcohol consumption, H. pylori infection, and predominant lesion site were factors that affected FsG17 levels. The optimal cut-off values for FsG17 were 3.0 pmol/l (sensitivity of 59.3% and specificity of 67.3%) for discriminating between healthy stomach and diseased stomach and 10.7 pmol/l (sensitivity of 37% and specificity of 83.7%) for discriminating between cancerous stomach and cancer-free stomach; the screening accuracy was higher (sensitivity of 50.0% and specificity of 83.0%) for gastric cancer in the corpus. Multivariate analysis showed that FsG17, gender, age, and H. pylori infection were independent predictors of cancerous stomach.

CONCLUSION

With the progression from health stomach to malignancy, FsG17 levels significantly increased and were influenced by other factors. FsG17 combined with age, gender, and H. pylori infection could distinguish between cancerous stomach and cancer-free stomach. The results will enhance our understanding of the potential clinical utility of FsG17.

Gastrin-releasing peptide receptor signaling in the integration of stress and memory

Neuropeptides act as signaling molecules that regulate a range of aspects of brain function. Gastrin-releasing peptide (GRP) is a 27-amino acid mammalian neuropeptide, homolog of the amphibian peptide bombesin. GRP acts by binding to the GRP receptor (GRPR, also called BB2), a member of the G-protein coupled receptor (GPCR) superfamily. GRP produced by neurons in the central nervous system (CNS) plays a role in synaptic transmission by activating GRPRs located on postsynaptic membranes, influencing several aspects of brain function. Here we review the role of GRP/GRPR as a system mediating both stress responses and the formation and expression of memories for fearful events. GRPR signaling might integrate the processing of stress and fear with synaptic plasticity and memory, serving as an important component of the set of neurobiological systems underlying the enhancement of memory storage by aversive information.

EGFRvIII stimulates glioma growth and invasion through PKA-dependent serine phosphorylation of Dock180

Glioblastomas (GBMs), the most common and malignant brain tumors, are highly resistant to current therapies. The failure of targeted therapies against aberrantly activated oncogenic signaling, such as that of the EGFR-PI3K/Akt pathway, underscores the urgent need to understand alternative downstream pathways and to identify new molecular targets for the development of more effective treatments for gliomas. Here, we report that EGFRvIII (ΔEGFR/de2-7EGFR), a constitutively active EGFR mutant that is frequently co-overexpressed with EGFR in clinical GBM tumors, promotes glioma growth and invasion through protein kinase A (PKA)-dependent phosphorylation of Dock180, a bipartite guanine nucleotide exchange factor (GEF) for Rac1. We demonstrate that EGFRvIII induces serine phosphorylation of Dock180, stimulates Rac1 activation and glioma cell migration. Treatments of glioma cells using the PKA inhibitors H-89 and KT5720, overexpression of a PKA inhibitor (PKI), and in vitro PKA kinase assays show that EGFRvIII induction of serine phosphorylation of Dock180 is PKA-dependent. Significantly, PKA induces phosphorylation of Dock180 at amino acid residue S1250 that resides within its Rac1-activating DHR-2 domain. Expression of the Dock180(S1250L) mutant, but not wild type Dock180(WT), protein in EGFRvIII-expressing glioma cells inhibited receptor-stimulated cell proliferation, survival, migration in vitro and glioma tumor growth and invasion in vivo. Together, our findings describe a novel mechanism by which EGFRvIII drives glioma tumorigenesis and invasion through PKA-dependent phosphorylation of Dock180, thereby suggesting that targeting EGFRvIII-PKA-Dock180-Rac1 signaling axis could provide a novel pathway to develop potential therapeutic strategies for malignant gliomas.

Benzoquinones and terphenyl compounds as phosphodiesterase-4B inhibitors from a fungus of the order Chaetothyriales (MSX 47445)

Three bioactive compounds were isolated from an organic extract of an ascomycete fungus of the order Chaetothyriales (MSX 47445) using bioactivity-directed fractionation as part of a search for anticancer leads from filamentous fungi. Of these, two were benzoquinones [betulinan A (1) and betulinan C (3)], and the third was a terphenyl compound, BTH-II0204-207:A (2). The structures were elucidated using a set of spectroscopic and spectrometric techniques; the structure of the new compound (3) was confirmed via single-crystal X-ray diffraction. Compounds 1-3 were evaluated for cytotoxicity against a human cancer cell panel, for antimicrobial activity against Staphylococcus aureus and Candida albicans, and for phosphodiesterase (PDE4B2) inhibitory activities. The putative binding mode of 1-3 with PDE4B2 was examined using a validated docking protocol, and the binding and enzyme inhibitory activities were correlated.

Effects of Lonomia obliqua caterpillar venom upon the proliferation and viability of cell lines

Many active principles produced by animals, plants and microorganisms have been employed in the development of new drugs for the treatment of human diseases. Among animals known to produce pharmacologically active molecules that interfere in human cell physiology, the caterpillar Lonomia obliqua has become the focus of toxicological studies due to recent findings about its venom constituents. The objective of this study was to investigate the effects of L. obliqua venom upon the viability and the proliferation of different cell lineages and to propose mechanisms for the herein observed induction of cell proliferation in glioma cell lines. MTT analyses indicate that L. obliqua venom increases the viability of tumor cell lines U138-MG and HT-29; on the other hand, it inhibits the viability of V-79 nontumor cells. Cell count based on the trypan blue exclusion method suggests a proliferating activity of the venom upon U138-MG cells. Exposure of U138-MG to crude venom extract led to a decrease in the production of nitric oxide, and activation of the cAMP signaling pathway inhibited the effects of the venom, indicating that these mechanisms may influence cell proliferation triggered by the venom. Despite the proliferative effects of crude venom on U138-MG and HT-29 cell cultures, a protein purified from L. obliqua hemolymph previously shown to have cytoprotective activity had no effect on U138-MG and HT-29; however, this same protein increased the viability of V-79 cells that had previously been exposed to the cytotoxic activity of the crude venom extract. This study indicates that the venom and the antiapoptotic protein act differently and have different effects on cell cultures, depending on the cell line analyzed. Biomolecules displaying either mitogenic or cytotoxic activities are of great biotechnological interest. Further studies encompassing the purification of active principles from L. obliqua venom are necessary to further elucidate its effects on different cell types.

Influence of GRPR and BDNF/TrkB signaling on the viability of breast and gynecologic cancer cells

Neuropeptide and neurotrophin receptors are increasingly important molecular targets in cancer. Scientific findings indicate that compounds blocking gastrin-releasing peptide receptors (GRPR) or tropomyosin receptor kinase (Trk) receptors are likely to have antiproliferative activities against cancer cells. The present study aimed to demonstrate that, in contrast to previous findings, GRPR activation reduces, whereas its blockade increases the viability of breast, ovarian and cervical cancer cell lines. However, consistent with previous studies, Trk inhibition was demonstrated to reduce the viability of these cells. MCF-7 (breast), OVCAR-3 (ovarian) and HeLa (cervical) human cancer cell lines were treated with GRP, the GRPR antagonists RC-3095 and RC-3940-II, brain-derived neurotrophic factor (BDNF) and the Trk antagonist K252α. Cell viability was measured by the MTT assay. Expression of GRPR and BDNF was confirmed with reverse transcription-polymerase chain reaction (RT-PCR). GRP reduced, whereas RC-3940-II enhanced the viability of the three cell lines. Treatment with K252α inhibited the viability of the cell lines, while BDNF increased the viability of OVCAR-3 cells. The results supported the hypothesis that GRPR and BDNF/TrkB signaling regulates cancer cell viability. Most importantly, these findings are the first to demonstrate that GRPR blockade can stimulate, rather than inhibits the viability of breast and gynecologic cancer cell lines.

BDNF/TrkB signaling protects HT-29 human colon cancer cells from EGFR inhibition

The clinical success of targeted treatment of colorectal cancer (CRC) is often limited by resistance to anti-epidermal growth factor receptor (EGFR) therapy. The neurotrophin brain-derived neurotrophic factor (BDNF) and its receptor TrkB have recently emerged as anticancer targets, and we have previously shown increased BDNF levels in CRC tumor samples. Here we report the findings from in vitro experiments suggesting that BDNF/TrkB signaling can protect CRC cells from the antitumor effects of EGFR blockade. The anti-EGFR monoclonal antibody cetuximab reduced both cell proliferation and the mRNA expression of BDNF and TrkB in human HT-29 CRC cells. The inhibitory effect of cetuximab on cell proliferation and survival was counteracted by the addition of human recombinant BDNF. Finally, the Trk inhibitor K252a synergistically enhanced the effect of cetuximab on cell proliferation, and this effect was blocked by BDNF. These results provide the first evidence that increased BDNF/TrkB signaling might play a role in resistance to EGFR blockade. Moreover, it is possible that targeting TrkB could potentiate the anticancer effects of anti-EGFR therapy.

Gastrin-releasing peptide receptors in the central nervous system: role in brain function and as a drug target

Neuropeptides acting on specific cell membrane receptors of the G protein-coupled receptor (GPCR) superfamily regulate a range of important aspects of nervous and neuroendocrine function. Gastrin-releasing peptide (GRP) is a mammalian neuropeptide that binds to the GRP receptor (GRPR, BB2). Increasing evidence indicates that GRPR-mediated signaling in the central nervous system (CNS) plays an important role in regulating brain function, including aspects related to emotional responses, social interaction, memory, and feeding behavior. In addition, some alterations in GRP or GRPR expression or function have been described in patients with neurodegenerative, neurodevelopmental, and psychiatric disorders, as well as in brain tumors. Findings from preclinical models are consistent with the view that the GRPR might play a role in brain disorders, and raise the possibility that GRPR agonists might ameliorate cognitive and social deficits associated with neurological diseases, while antagonists may reduce anxiety and inhibit the growth of some types of brain cancer. Further preclinical and translational studies evaluating the potential therapeutic effects of GRPR ligands are warranted.

Restoring soluble guanylyl cyclase expression and function blocks the aggressive course of glioma

The NO and cGMP signaling pathways are of broad physiological and pathological significance. We compared the NO/soluble guanylyl cyclase (sGC)/cGMP pathway in human glioma tissues and cell lines with that of healthy control samples and demonstrated that sGC expression is significantly lower in glioma preparations. Our analysis of GEO databases (National Cancer Institute) further revealed a statistically significant reduction of sGC transcript levels in human glioma specimens. On the other hand, the expression levels of particulate (membrane) guanylyl cyclases (pGC) and cGMP-specific phosphodiesterase (PDE) were intact in the glioma cells that we have tested. Pharmacologically manipulating endogenous cGMP generation in glioma cells through either stimulating pGC by ANP/BNP, or blocking PDE by 3-isobutyl-1-methylxanthine/zaprinast caused significant inhibition of proliferation and colony formation of glioma cells. Genetically restoring sGC expression also correlated inversely with glioma cells growth. Orthotopic implantation of glioma cells transfected with an active mutant form of sGC (sGCα1β1(Cys105)) in athymic mice increased the survival time by 4-fold over the control. Histological analysis of xenografts overexpressing α1β1(Cys105) sGC revealed changes in cellular architecture that resemble the morphology of normal cells. In addition, a decrease in angiogenesis contributed to glioma inhibition by sGC/cGMP therapy. Our study proposes the new concept that suppressed expression of sGC, a key enzyme in the NO/cGMP pathway, may be associated with an aggressive course of glioma. The sGC/cGMP signaling-targeted therapy may be a favorable alternative to chemotherapy and radiotherapy for glioma and perhaps other tumors.

BDNF/TrkB content and interaction with gastrin-releasing peptide receptor blockade in colorectal cancer

OBJECTIVE

Neurotrophin and neuropeptide pathways are emerging targets in cancer. Here we show that brain-derived neurotrophic factor (BDNF) and its receptor, TrkB, are present in colorectal cancer and that BDNF levels are increased in tumors compared to nontumor tissue. In addition, we investigate the role of BDNF in influencing the response of colorectal cancer cells to inhibition of gastrin-releasing peptide receptors (GRPR).

METHODS

Fresh-frozen sporadic colorectal adenocarcinoma specimens and adjacent nonneoplastic tissue from 30 patients, as well as paraffin-embedded colorectal cancer samples from 21 patients, were used in this study. Cell proliferation and mRNA and protein levels were examined in HT-29 or SW620 cells treated with a GRPR antagonist, human recombinant BDNF (hrBDNF), a Trk antagonist K252a, or cetuximab.

RESULTS

Expression of BDNF and TrkB was detected in tumor samples and cell lines. BDNF levels were higher in tumor samples compared to nonneoplastic tissue. BDNF expression and secretion were increased by GRPR blockade in HT-29 cells through a mechanism dependent on epidermal growth factor receptors. Treatment with hrBDNF prevented the effect of GRPR blockade on cell proliferation, whereas a Trk inhibitor reduced proliferation.

CONCLUSIONS

BDNF and TrkB are present in colorectal cancer and might contribute to resistance to GRPR antagonists.

Endogenously generated 2-arachidonoylglycerol plays an inhibitory role in bombesin-induced activation of central adrenomedullary outflow in rats

We previously reported the involvement of brain diacylglycerol lipase and cyclooxygenase in intracerebroventricularly (i.c.v.) administered bombesin-induced secretion of noradrenaline and adrenaline from the adrenal medulla in rats. Diacylglycerol can be hydrolyzed by diacylglycerol lipase into 2-arachidonoylglycerol, which may be further hydrolyzed by monoacylglycerol lipase into arachidonic acid, a substrate of cyclooxygenase. 2-Arachidonoylglycerol is a major endocannabinoid, which can inhibit synaptic transmission by presynaptic cannabinoid CB(1) receptors. Released 2-arachidonoylglycerol is rapidly inactivated by uptake into cells and enzymatic hydrolysis. In the present study, we examined the involvement of brain 2-arachidonoylglycerol and its regulatory role in the bombesin-induced central activation of adrenomedullary outflow using anesthetized rats. The elevation of plasma noradrenaline and adrenaline induced by a sub-maximal dose of bombesin (1 nmol/animal, i.c.v.) was reduced by MAFP (monoacylglycerol lipase inhibitor) (0.28 and 0.7 μmol/animal, i.c.v.), JZL184 (selective monoacylglycerol lipase inhibitor) (0.7 and 1.4 μmol/animal, i.c.v.), ACEA (CB(1) receptor agonist) (0.7 and 1.4 μmol/animal, i.c.v.) and AM 404 (endocannabinoid uptake-inhibitor) (80 and 250 nmol/animal, i.c.v.), while AM 251 (CB(1) receptor antagonist) (90 and 180 nmol/animal, i.c.v.) potentiated the response induced by a small dose of bombesin (0.1 nmol/animal, i.c.v.). These results suggest a possibility that 2-arachidonoylglycerol is endogenously generated in the brain during bombesin-induced activation of central adrenomedullary outflow, thereby inhibiting the peptide-induced response by activation of brain CB(1) receptors in rats.

Current and emerging molecular targets in glioma

Gliomas are the most common and lethal neurological cancers. Despite research efforts, the prognosis for patients with malignant gliomas remains poor. Advances in the understanding of cellular and molecular alterations in gliomas have led to the emergence of experimental molecularly targeted therapies. This article summarizes recent progress in the development of targeted therapies for glioma, focusing on emerging molecular targets, including neuropeptide and neurotrophin pathways, glutamate receptors, epigenetic mechanisms and glioma stem cell targets. Recent clinical trials of small molecules and antibodies targeted at growth factor pathways and intracellular signaling cascades are also discussed.

National Science and Technology Institute for Translational Medicine (INCT-TM): advancing the field of translational medicine and mental health

OBJECTIVE

Translational medicine has been described as the integrated application of innovative pharmacology tools, biomarkers, clinical methods, clinical technologies and study designs to improve the understanding of medical disorders. In medicine, translational research offers an opportunity for applying the findings obtained from basic research to every-day clinical applications. The National Science and Technology Institute for Translational Medicine is comprised of six member institutions (Universidade Federal do Rio Grande do Sul, Universidade de São Paulo-Ribeirão Preto, Universidade Federal do Rio de Janeiro, Pontifícia Universidade Católica do Rio Grande do Sul, Universidade Estadual de Santa Catarina and a core facility that serves all centers). The objectives of the project are divided into four areas: Institutional, Research, Human Resources and Technology for the Community and Productive Sector.

METHOD

In this manuscript, we describe some of the approaches used to attain the main objectives of the National Science and Technology Institute for Translational Medicine, which include the development of 1) animal models for bipolar disorder; 2) strategies to investigate neurobehavioral function and cognitive dysfunction associated with brain disorders; 3) experimental models of brain function and behavior, neuropsychiatric disorders, cell proliferation, and cancer; 4) Simulated Public Speaking and 5) Virtual reality simulation for inducing panic disorder and agoraphobia.

CONCLUSION

The main focus of the National Science and Technology Institute for Translational Medicine is the development of more useful methods that allow for a better application of basic research-based knowledge to the medical field.

Mangiferin, a naturally occurring glucoxilxanthone improves long-term object recognition memory in rats

Mangiferin (2-beta-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone) is a xanthone widely distributed in higher plants showing antioxidative, antiviral, anticancer, antidiabetic, immunomodulatory, hepatoprotective, and analgesic effects. In the present study, we have investigated the effects of systemic administration of mangiferin on behavioral outcomes of neurological function in normal rats. A single intraperitoneal injection of mangiferin (10, 50, or 100mg/kg body weight) enhanced novel object recognition (NOR) memory when given immediately post-training. The administration of mangiferin 6h post-training did not affect NOR memory. There were no significant differences between groups in the total time exploring both objects, indicating that mangiferin did not affect locomotion or motivation. Mangiferin stimulated cell proliferation and induced a significant increase in the supernatant levels of nerve growth factor (NGF) and tumor necrosis factor (TNF)-alpha in vitro in human U138-MG glioblastoma cells. The results indicate that mangiferin enhances recognition memory through a mechanism that might involve an increase in neurotrophin and cytokine levels.

Regulation and signaling of human bombesin receptors and their biological effects

PURPOSE OF REVIEW

This review will highlight recent advances in the understanding of molecular mechanisms by which mammalian bombesin receptors are regulated and which intracellular signaling pathways have been characterized to mediate agonist-dependent receptor biological effects.

RECENT FINDINGS

Mammalian bombesin receptors have been demonstrated to be involved in a larger array of physiological and pathophysiological conditions than previously reported. Pharmacological experiments in vitro and in vivo as well as utilization of animals genetically deficient of the gastrin-releasing peptide receptor demonstrated roles in memory and fear behavior, lung development and injury, small intestinal cell repair, autocrine tumor growth, and mediating signals for pruritus and penile reflexes. Intracellular signaling studies predominantly of the gastrin-releasing peptide receptor owing to its frequent overexpression in some human malignancies showed that PI3 kinase activation is an important mechanism of cell proliferation. Tumor cell treatment including gastrin-releasing peptide receptor antagonists combined with inhibition of epidermal growth factor receptor resulted in an additive effect on blocking cell proliferation. Novel molecular mechanisms of the orphan bombesin receptor subtype-3 and gastrin-releasing peptide receptor gene regulation have been elucidated.

SUMMARY

Inhibition of gastrin-releasing peptide receptor signaling in human malignancies represents an attractive target for pharmacological treatment. Novel functions of bombesin related peptides have been identified including processes in the central nervous system, lung and intestinal tract.

Advances of gastrin-releasing peptide receptor in treatment of tumors

The mammalian gastrin-releasing peptide (GRP), known as autocrine growth factors in tumors, is involved in the pathogenesis and progression of many human malignant tumors, and high expression of its receptor, GRPR, in a large spectrum of human cancers gives support to the conclusion that GRPR is a new molecular target in experimental and clinical cancer therapy. GRPRs may be potential carriers for cytotoxins, immunotoxins or radioactive compounds. Moreover, blocking gastrin-releasing peptide receptor signaling pathways by means of antisence oligonucleotide, RNA interference and its antagonists has exhibited impressive antitumor activity.