Somatostatin inhibits colon cancer cell growth through cyclooxygenase-2 downregulation. Br J Pharmacol. 2008;155:198-209. [PMID: 18587421 DOI: 10.1038/bjp.2008.268]

Octreotide attenuates intestinal barrier damage by maintaining basal autophagy in Caco2 cells

The intestinal mucosal barrier is of great importance for maintaining the stability of the internal environment, which is closely related to the occurrence and development of intestinal inflammation. Octreotide (OCT) has potential applicable clinical value for treating intestinal injury according to previous studies, but the underlying molecular mechanisms have remained elusive. This article is based on a cell model of inflammation induced by lipopolysaccharide (LPS), aiming to explore the effects of OCT in protecting intestinal mucosal barrier function. A Cell Counting Kit‑8 assay was used to determine cell viability and evaluate the effectiveness of OCT. Gene silencing technology was used to reveal the mediated effect of somatostatin receptor 2 (SSTR2). The changes in intestinal permeability were detected through trans‑epithelial electrical resistance and fluorescein isothiocyanate‑dextran 4 experiments, and the alterations in tight junction proteins were detected using immunoblotting and reverse transcription fluorescence‑quantitative PCR technology. Autophagosomes were observed by electron microscopy and the dynamic changes of the autophagy process were characterized by light chain (LC)3‑II/LC3‑I conversion and autophagic flow. The results indicated that SSTR2‑dependent OCT can prevent the decrease in cell activity. After LPS treatment, the permeability of monolayer cells decreased and intercellular tight junctions were disrupted, resulting in a decrease in tight junction protein zona occludens 1 in cells. The level of autophagy‑related protein LC3 was altered to varying degrees at different times. These abnormal changes gradually returned to normal levels after the combined application of LPS and SSTR2‑dependent OCT, confirming the role of OCT in protecting intestinal barrier function. These experimental results suggest that OCT maintains basal autophagy and cell activity mediated by SSTR2 in intestinal epithelial cells, thereby preventing the intestinal barrier dysfunction in inflammation injury.

Modulation of faecal miRNAs highlights the preventive effects of a Mediterranean low-inflammatory dietary intervention

BACKGROUND

Dietary interventions have been proposed as therapeutic approaches for several diseases, including cancer. A low-inflammatory Mediterranean dietary intervention, conducted as a pilot study in subjects with Familial Adenomatous Polyposis (FAP), reduced markers of local and systemic inflammation. We aim to determine whether this diet may modulate faecal microRNA (miRNA) and gene expression in the gut.

METHODS

Changes in the faecal miRNome were evaluated by small RNA sequencing at baseline (T0), after the three-month intervention (T1), and after an additional three months (T2). Changes in the transcriptome of healthy rectal mucosa and adenomas were evaluated by RNA sequencing at T0 and T2. The identification of validated miRNA-gene interactions and functional analysis of miRNA targets were performed using in silico approaches.

RESULTS

Twenty-seven subjects were included in this study. It was observed that the diet modulated 29 faecal miRNAs (p < 0.01; |log2 Fold Change|>1), and this modulation persisted for three months after the intervention. Levels of miR-3612-3p and miR-941 correlated with the adherence to the diet, miR-3670 and miR-4252-5p with faecal calprotectin, and miR-3670 and miR-6867 with serum calprotectin. Seventy genes were differentially expressed between adenoma and normal tissue, and most were different before the dietary intervention but reached similar levels after the diet. Functional enrichment analysis identified the proinflammatory ERK1/2, cell cycle regulation, and nutrient response pathways as commonly regulated by the modulated miRNAs and genes.

CONCLUSIONS

Faecal miRNAs modulated by the dietary intervention target genes that participate in inflammation. Changes in levels of miRNAs and genes with oncogenic and tumour suppressor functions further support the potential cancer-preventive effect of the low-inflammatory Mediterranean diet.

CLINICAL TRIAL NUMBER REGISTRATION

NCT04552405, Registered in ClinicalTrials.gov.

Remission of organ failure in patients with predicted severe acute pancreatitis treated by somatostation, octreotide and cyclooxygenase-2 inhibitors

BACKGROUND

/Objectives: Persistent organ failure (OF) in severe acute pancreatitis (SAP) is caused by activation of cytokine cascades, resulting in inflammatory injury. Anti-inflammation may be helpful in OF remission in early SAP. To assess the efficacy of anti-inflammatory regimens for OF prevention and remission in patients with predicted SAP and display clinical doctors' acceptance of these strategies, we conducted this retrospective study in the real world.

METHODS

Clinical data of patients with predicted SAP from 2010 to 2017 were retrospectively reviewed. Cases were divided into conventional support (C), C+ somatostatin/octreotide (C + S/O), and C + S/O + Cyclooxygenase-2-inhibitors (C + S/O + COX-2-I). The occurrence of SAP, OF, changes of proportion for three strategies, length of hospital stay, meperidine injection, and cytokine levels were compared. The constituent ratios of the three schemes over eight years were evaluated.

RESULTS

A total of 580 cases (C = 124, C + S/O = 290, C + S/O + COX-2-I = 166) were included. The occurrences of SAP in the C + S/O (28.3 %) and C + S/O + COX-2-I (18.1 %) groups were significantly lower than that in C group (60.5 %, P < 0.001), mainly by reducing persistent respiratory failure (P < 0.001) and renal failure (P = 0.002). C + S/O and C + S/O + COX-2-I regimens significantly decreased new onset OF and enhanced OF amelioration within 48 h when compared with C treatment (P < 0.001) in patients with OF score <2 and ≥ 2 on admission, respectively. C + S/O and C + S/O + COX-2-I as compared with C group significantly decrease OF occurrences in a multivariate logistic regression analysis (P < 0.05).

CONCLUSIONS

Somatostatin or its analogs and cyclooxygenase-2 inhibitors are promising for OF prevention and remission in patients with predicted SAP. The acceptance of combined strategies in the real world has increased, and the occurrence of SAP has decreased annually.

Somatostatin and Somatostatin Receptors in Tumour Biology

Somatostatin (SST), a growth hormone inhibitory peptide, is expressed in endocrine and non-endocrine tissues, immune cells and the central nervous system (CNS). Post-release from secretory or immune cells, the first most appreciated role that SST exhibits is the antiproliferative effect in target tissue that served as a potential therapeutic intervention in various tumours of different origins. The SST-mediated in vivo and/or in vitro antiproliferative effect in the tumour is considered direct via activation of five different somatostatin receptor subtypes (SSTR1-5), which are well expressed in most tumours and often more than one receptor in a single cell. Second, the indirect effect is associated with the regulation of growth factors. SSTR subtypes are crucial in tumour diagnosis and prognosis. In this review, with the recent development of new SST analogues and receptor-specific agonists with emerging functional consequences of signaling pathways are promising therapeutic avenues in tumours of different origins that are discussed.

The Galaninergic System: A Target for Cancer Treatment

Simple Summary

Peptidergic systems play an important role in cancer progression. The galaninergic system (the peptide galanin and its receptors: galanin 1, 2 and 3) is involved in tumorigenesis, the invasion and migration of tumor cells and angiogenesis and it has been correlated with tumor stage/subtypes, metastasis and recurrence rate in many types of cancer. Galanin exerts a dual action in tumor cells: a proliferative or an antiproliferative effect depending on the galanin receptor involved in these mechanisms. Galanin receptors could be used in certain tumors as therapeutic targets and diagnostic markers for treatment, prognosis and surgical outcome. This review shows the importance of the galaninergic system in the development of tumors and suggests future promising clinical antitumor applications using galanin agonists or antagonists.

Abstract

The aim of this review is to show the involvement of the galaninergic system in neuroendocrine (phaeochromocytomas, insulinomas, neuroblastic tumors, pituitary tumors, small-cell lung cancer) and non-neuroendocrine (gastric cancer, colorectal cancer, head and neck squamous cell carcinoma, glioma) tumors. The galaninergic system is involved in tumorigenesis, invasion/migration of tumor cells and angiogenesis, and this system has been correlated with tumor size/stage/subtypes, metastasis and recurrence rate. In the galaninergic system, epigenetic mechanisms have been related with carcinogenesis and recurrence rate. Galanin (GAL) exerts both proliferative and antiproliferative actions in tumor cells. GAL receptors (GALRs) mediate different signal transduction pathways and actions, depending on the particular G protein involved and the tumor cell type. In general, the activation of GAL₁R promoted an antiproliferative effect, whereas the activation of GAL₂R induced antiproliferative or proliferative actions. GALRs could be used in certain tumors as therapeutic targets and diagnostic markers for treatment, prognosis and surgical outcome. The current data show the importance of the galaninergic system in the development of certain tumors and suggest future potential clinical antitumor applications using GAL agonists or antagonists.

Somatostatin and Its Receptor System in Colorectal Cancer

Somatostatin (SST)/somatotropin release-inhibiting factor (SRIF) is a well-known neuropeptide, widely distributed in the central and peripheral nervous systems, that regulates the endocrine system and affects neurotransmission via interaction with five SST receptors (SST1-5). In the gastrointestinal tract, the main SST-producing cells include intestinal enteroendocrine cells (EECs) restricted to the mucosa, and neurons of the submucosal and myenteric plexuses. The action of the SRIF system is based on the inhibition of endocrine and exocrine secretion, as well as the proliferative responses of target cells. The SST1–5 share common signaling pathways, and are not only widely expressed on normal tissues, but also frequently overexpressed by several tumors, particularly neuroendocrine neoplasms (NENs). Furthermore, the SRIF system represents the only peptide/G protein-coupled receptor (GPCR) system with multiple approved clinical applications for the diagnosis and treatment of several NENs. The role of the SRIF system in the histogenesis of colorectal cancer (CRC) subtypes (e.g., adenocarcinoma and signet ring-cell carcinoma), as well as diagnosis and prognosis of mixed adenoneuroendocrine carcinoma (MANEC) and pure adenocarcinoma, is poorly understood. Moreover, the impact of the SRIF system signaling on CRC cell proliferation and its potential role in the progression of this cancer remains unknown. Therefore, this review summarizes the recent collective knowledge and understanding of the clinical significance of the SRIF system signaling in CRC, aiming to evaluate the potential role of its components in CRC histogenesis, diagnosis, and potential therapy.

The Neurotensinergic System: A Target for Cancer Treatment

BACKGROUND

The scientific interest regarding the involvement of peptides in cancer has increased in the last years. In tumor cells the overexpression of peptides and their receptors is known and new therapeutic targets for the treatment of cancer have been suggested. The overexpression of the neurotensinergic system has been associated with poor prognosis, tumor size, higher tumor aggressiveness, increased relapse risk and worse sensitivity to chemotherapy agents.

OBJECTIVE

The aim of this review is to update the findings regarding the involvement of the neurotensinergic system in cancer to suggest anticancer therapeutic strategies targeting this system. The neurotensin (NT) precursor, NT and its receptors (NTR) and the involvement of the neurotensinergic system in lung, breast, prostate, gastric, colon, liver and pancreatic cancers, glioblastoma, neuroendocrine tumors and B-cell leukemia will be mentioned and discussed as well as the signaling pathways mediated by NT. Some research lines to be developed in the future will be suggested such as: molecules regulating the expression of the NT precursor, influence of the diet in the development of tumors, molecules and signaling pathways activated by NT and antitumor therapeutic strategies targeting the neurotensinergic system.

CONCLUSION

NT, via the NTR, exerts oncogenic (tumor cell proliferation, invasion, migration, angiogenesis) and antiapoptotic effects, whereas NTR antagonists inhibit these effects. NTR expression can be used as a diagnostic tool/therapeutic target and the administration of NTR antagonists as antitumor drugs could be a therapeutic strategy to treat tumors overexpressing NTR.

The Neuropeptide System and Colorectal Cancer Liver Metastases: Mechanisms and Management

Colorectal cancer (CRC), classified as the third most prevalent cancer worldwide, remains to be a clinical and research challenge. It is estimated that ~50% of CRC patients die from distant metastases, with treatment of this complication still posing significant difficulties. While liver metastasis (LM) cascade is known in the literature, its mechanisms are still unclear and remain studied in different research models. A connection is suggested between nervous system dysfunctions and a range of Neurotransmitters (Nts) (including Neuropeptides, NPs), Neurotrophins (Ntt) and their receptors (Rs) in CRC liver metastasis development. Studies on the role of NP/NP-Rs in the progression and metastasis of CRC, show the complexity of brain–tumor interactions, caused by their different forms of release to the extracellular environment (endocrine, autocrine, paracrine and neurocrine). Many stages of LM are connected to the activity of pro-inflammatory, e.g., Corticotropin-releasing Hormone Receptor 1 (CRHR1), Neuropeptide Y (NPY) and Neurotensin (NT), anti-inflammatory, e.g., Calcitonin Gene-related Peptide (CGRP), CRHR2 and Vasoactive Intestinal Polypeptide (VIP) or dual role neuropeptides, e.g., Substance P (SP). The regulation of the local immunological profile (e.g., CRH/CRHRs), dysfunctions of enteroprotective role of NPs on epithelial cells (e.g., NT/NT-R), as well as structural-functional changes in enteric nervous system innervation of the tumor are also important. More research is needed to understand the exact mechanisms of communication between the neurons and tumor cells. The knowledge on the mechanisms regulating tumor growth and different stages of metastasis, as well as effects of the action of a numerous group of Nts/NPs/Ntt as growth factors, have implications for future therapeutic strategies. To obtain the best treatment outcomes, it is important to use signaling pathways common for many NPs, as well to develop a range of broad-spectrum antagonists. This review aims to summarize the current knowledge on the importance of neuroactive molecules in the promotion of the invasion-metastasis cascade in CRC, as well as the improvements of clinical management of CRC liver metastasis.

The Neuropeptide System and Colorectal Cancer Liver Metastases: Mechanisms and Management

Colorectal cancer (CRC), classified as the third most prevalent cancer worldwide, remains to be a clinical and research challenge. It is estimated that ~50% of CRC patients die from distant metastases, with treatment of this complication still posing significant difficulties. While liver metastasis (LM) cascade is known in the literature, its mechanisms are still unclear and remain studied in different research models. A connection is suggested between nervous system dysfunctions and a range of Neurotransmitters (Nts) (including Neuropeptides, NPs), Neurotrophins (Ntt) and their receptors (Rs) in CRC liver metastasis development. Studies on the role of NP/NP-Rs in the progression and metastasis of CRC, show the complexity of brain–tumor interactions, caused by their different forms of release to the extracellular environment (endocrine, autocrine, paracrine and neurocrine). Many stages of LM are connected to the activity of pro-inflammatory, e.g., Corticotropin-releasing Hormone Receptor 1 (CRHR1), Neuropeptide Y (NPY) and Neurotensin (NT), anti-inflammatory, e.g., Calcitonin Gene-related Peptide (CGRP), CRHR2 and Vasoactive Intestinal Polypeptide (VIP) or dual role neuropeptides, e.g., Substance P (SP). The regulation of the local immunological profile (e.g., CRH/CRHRs), dysfunctions of enteroprotective role of NPs on epithelial cells (e.g., NT/NT-R), as well as structural-functional changes in enteric nervous system innervation of the tumor are also important. More research is needed to understand the exact mechanisms of communication between the neurons and tumor cells. The knowledge on the mechanisms regulating tumor growth and different stages of metastasis, as well as effects of the action of a numerous group of Nts/NPs/Ntt as growth factors, have implications for future therapeutic strategies. To obtain the best treatment outcomes, it is important to use signaling pathways common for many NPs, as well to develop a range of broad-spectrum antagonists. This review aims to summarize the current knowledge on the importance of neuroactive molecules in the promotion of the invasion-metastasis cascade in CRC, as well as the improvements of clinical management of CRC liver metastasis.

Colorectal Cancer Invasion and Atrophy of the Enteric Nervous System: Potential Feedback and Impact on Cancer Progression

Colorectal cancer (CRC) invasion within the large intestine wall results in the replacement of normal tissue architecture by tumour mass. Cancer cells digest the extracellular matrix (ECM) by the release of proteolytic enzymes. The disintegration of matrix ground substance activates several deposited growth factors which stimulate cell proliferation. Stromal (mainly fibroblasts), immune and cancer cells dominate in this area and become involved in a network of multimodal interactions which significantly induce proliferation of colon cancer cells, inhibit their apoptosis and promote their spreading within the local tumour microenvironment. Cancer invasion destroys nerve fibres and neurons of the local enteric nervous system (ENS) and induces subsequent atrophy of the submucosal and myenteric plexuses in areas adjacent to the cancer boundary. Interestingly, the reduction of plexuses' size is accompanied by the increased number of galanin-immunoreactive neurons and increased galanin content in parts of the colon located close to the tumour. Galanin, a neuroprotective peptide, may inhibit the extrinsic pathway of apoptosis and in this way promote cancer cell survival. The possible role of acetylcholine and some ENS neuropeptides was also discussed. Invasion of cancer cells spreads along nerve fibres with the involvement of locally-released neutrophins which promote, via their specific receptors, cancer cell proliferation and pro-survival signalling pathways. Thus, during CRC development cancer cells and neurons of the ENS release many neurotransmitters/neuropeptides which affect key cellular signalling pathways promoting cancer cell proliferation and pro-survival phenotype. The multiple interactions between ENS neurons, cancer cells and other cell types present in the colon wall increase cancer cell invasiveness and have a negative impact on the course of CRC.

Cetuximab Conjugated with Octreotide and Entrapped Calcium Alginate-beads for Targeting Somatostatin Receptors

There is a need to formulate oral cetuximab (CTX) for targeting colorectal cancer, which is reported to express somatostatin receptors (SSTRs). Therefore, coating CTX with a somatostatin analogue such as octreotide (OCT) is beneficial. Alginate was used to coat CTX to facilitate delivery to the gastrointestinal tract (GIT). This study aimed to deliver CTX conjugated with OCT in the form of microparticles as a GIT-targeted SSTR therapy. Both CTX and OCT were conjugated using a solvent evaporation method and the conjugated CTX-OCT was then loaded onto Ca-alginate-beads (CTX-OCT-Alg), which were characterized for drug interactions using differential scanning calorimetry (DSC), and Fourier transform infrared spectra (FTIR). Moreover, the morphology of formulated beads was examined using a scanning electron microscope (SEM). The drug content and release profile were studied using UV spectroscopy. Finally, in vitro cytotoxicity of all compounds was evaluated. The results showed homogenous conjugated CTX-OCT with a diameter of 0.4 mm. DSC showed a delay in the OCT peak that appeared after 200 °C due to small polymer interaction that shifted the OCT peak. Moreover, FTIR showed no prominent interaction. SEM showed clear empty cavities in the plain Ca-alginate-beads, while CTX-OCT-Alg showed occupied beads without cavities. CTX-OCT-Alg had a negligible release in 0.1 N HCl, while the CTX-OCT was completely released after 300 min in phosphate buffer pH 7.4. All formulations showed good antiproliferative activity compared with free drugs. The formulated CTX-OCT-Alg are a promising platform for targeting colorectal cancer through GIT.

Somatostatin Analogs in Clinical Practice: a Review

Somatostatin analogs are an invaluable therapeutic option in the diagnosis and treatment of somatotropinomas, thyrotropinomas, and functioning and non-functioning gastroenteropancreatic neuroendocrine tumors. They should also be considered an effective and safe therapeutic alternative to corticotropinomas, gonadotropinomas, and prolactinomas resistant to dopamine agonists. Somatostatin analogs have also shown to be useful in the treatment of other endocrine diseases (congenital hyperinsulinism, Graves’ orbitopathy, diabetic retinopathy, diabetic macular edema), non-endocrine tumors (breast, colon, prostate, lung, and hepatocellular), and digestive diseases (chronic refractory diarrhea, hepatorenal polycystosis, gastrointestinal hemorrhage, dumping syndrome, and intestinal fistula).

Preclinical study of a new 177Lu-labeled somatostatin receptor antagonist in HT-29 human colorectal cancer cells

OBJECTIVES

Somatostatin receptor-positive neuroendocrine tumors have been targeted using various peptide analogs radiolabeled with therapeutic radionuclides for years. The better biomedical properties of radioantagonists as higher tumor uptake make these radioligands more attractive than agonists for somatostatin receptor-targeted radionuclide therapy. In this study, we tried to evaluate the efficiency of Luthetium-177 (177Lu) radiolabeled DOTA-Peptide 2 (177Lu-DOTA-Peptide 2) as a new radioantagonist in HT-29 human colorectal cancer in vitro and in vivo.

METHODS

DOTA conjugated antagonistic peptide with the sequence of p-Cl-Phe-Cyclo(D-Cys-L-BzThi-D-Aph-Lys-Thr-Cys)-D-Tyr-NH2 (DOTA-Peptide 2) was labeled with 177Lu. In vitro assays (saturation binding assay and internalization test) and animal biodistribution were performed in human colon adenocarcinoma cells (HT-29) and HT-29 tumor-bearing nude mice.

RESULTS

177Lu-DOTA-Peptide 2 showed high stability in acetate buffer and human plasma (>97%). Antagonistic property of 177Lu-DOTA-Peptide 2 was confirmed by low internalization in HT-29 cells (<5%). The desired dissociation constant (Kd =11.14 nM) and effective tumor uptake (10.89 percentage of injected dose per gram of tumor) showed high binding affinity of 177Lu-DOTA-Peptide 2 to somatostatin receptors.

CONCLUSION

177Lu-DOTA-Peptide 2 demonstrated selective and high binding affinity to somatostatin receptors overexpressed on the surface of HT-29 cancer cells, which could make this radiopeptide suitable for somatostatin receptor-targeted radionuclide therapy.

A case of gallbladder neuroendocrine carcinoma diagnosed preoperatively using somatostatin receptor scintigraphy

Gallbladder neuroendocrine carcinoma (NEC) is a rare gallbladder tumor. The current report is a case of a patient preoperatively diagnosed with gallbladder NEC using somatostatin receptor scintigraphy (SRS). A 63-year-old man was admitted to our hospital by a family doctor after abdominal ultrasonography revealed thickened walls of the neck of his gallbladder. At Kagoshima University Hospital, CT and MRI of the abdomen and endoscopic ultrasonography confirmed the thickening of the walls of the neck of the gallbladder. However, it did not resemble a typical gallbladder cancer or tumor, such as a neuroendocrine tumor or malignant lymphoma. Positron emission tomography and SRS showed abnormal accumulation at the tumor site. Endoscopic retrograde cholangiopancreatography was performed, adenocarcinoma was suspected based on intra-gallbladder bile cytology, and a cholecystectomy with lymphadenectomy was performed. The postoperative pathological diagnosis was small cell NEC (pT3a, N0, M0, stage II). Immunohistochemistry indicated that the gallbladder tumor cells were positive for synaptophysin, chromogranin A, and cluster of differentiation (CD) 56, and negative for somatostatin receptors (SSTR) 2 and 5. Gene expression assays revealed the expression of all SSTR subtypes (SSTR1-5) in the tumor. Generally, NECs exhibit poor accumulation in SRS, however, the results of the current case suggest that SRS may be useful in the preoperative diagnosis of NEC.

Pasireotide in the treatment of neuroendocrine tumors: a review of the literature

Somatostatin analogs have an important role in the medical therapy of neuroendocrine tumors (NETs). Octreotide and lanreotide, both somatostatin analogs binding with high affinity for the somatostatin receptor (SSTR)2, can control symptoms in functional NETs. In addition, these compounds, because of their antiproliferative effects, can stabilize growth of well-differentiated NETs. Pasireotide is a novel multireceptor-targeted somatostatin analog with high affinity for SSTR1, 2, 3, and 5. This review provides an overview of the state of the art of pasireotide in the treatment of NETs, with the aim of addressing clinical relevance and future perspectives for this molecule in the management of NETs.

Development of Colorectal-Targeted Dietary Supplement Tablets Containing Natural Purple Rice Bran Oil as a Colorectal Chemopreventive

Colorectal cancer occurs due to various factors. The important risks are dietary lifestyle and inflammatory bowel diseases, such as Crohn’s disease and ulcerative colitis. It has been found that the inhibitory enzyme cyclooxygenase-2 (COX-2) in the colorectal region can potentially reduce the risk of colorectal cancer. The present study investigated rice bran oil from natural purple rice bran, which exhibits antioxidant and anti-inflammatory activity. This study aimed to evaluate the bioactive compound content of natural purple rice bran oil (NPRBO) derived from native Thai purple rice and the anti-inflammatory activity of NPRBO in colorectal cancer cells, and to develop a colorectal delivery platform in the form of film-coated tablets. NPRBO from the rice bran of five different Thai purple rice cultivars, namely Khao’ Gam Leum-Phua (KGLP), Khao’ Gam Boung (KGB), Khao’ Gam Thor (KGT), Khao’ Gam Pah E-Kaw (KGPEK), and Khao’ Niaw Dam (KND), were extracted using the supercritical carbon dioxide extraction technique. The amount of γ-oryzanol (ORY), tocotrienols, and tocopherols present in NPRBOs and the in vitro anti-inflammatory activity of NPRBO were investigated. The highest anti-inflammatory NPRBO was transformed into a dry and free-flowing powder by liquisolid techniques. Then, it was compressed into core tablets and coated with Eudragit^®L100 and Eudragit^® NE30D. The in vitro release study of the film-coated NPRBO tablets was performed in three-phase simulated gastrointestinal media. The cultivar KGLP was superior to the other samples in terms of the ORY, tocotrienol and tocopherol contents and anti-inflammatory activity. Aerosil^® was the most suitable absorbent for transforming NPRBO into a free-flowing powder and was used to prepare the NPRBO core tablets. The in vitro KGLP-NPRBO film-coated tablet release profile showed that no ORY was released at gastric pH while 85% of ORY was released at pH 7.4 after 6 h; this would be expected to occur in the colorectal area. Therefore, this study demonstrates the potential of KGLP-NPRBO to prevent colorectal cancer via a specific colorectal dietary supplement delivery system.

Promoter hypermethylation-related reduced somatostatin production promotes uncontrolled cell proliferation in colorectal cancer

BACKGROUND

Somatostatin (SST) has anti-proliferative and pro-apoptotic effects. Our aims were to analyze and compare the SST expression during normal aging and colorectal carcinogenesis at mRNA and protein levels. Furthermore, we tested the methylation status of SST in biopsy samples, and the cell growth inhibitory effect of the SST analogue octreotide in human colorectal adenocarcinoma cell line.

METHODS

Colonic samples were collected from healthy children (n1 = 6), healthy adults (n2 = 41) and colorectal cancer patients (CRCs) (n3 = 34) for SST mRNA expression analysis, using HGU133 Plus2.0 microarrays. Results were validated both on original (n1 = 6; n2 = 6; n3 = 6) and independent samples ((n1 = 6; n2 = 6; n3 = 6) by real-time PCR. SST expressing cells were detected by immunohistochemistry on colonic biopsy samples (n1 = 14; n2 = 20; n3 = 23). The effect of octreotide on cell growth was tested on Caco-2 cell line. SST methylation percentage in biopsy samples (n1 = 5; n2 = 5; n3 = 9) was defined using methylation-sensitive restriction enzyme digestion.

RESULTS

In case of normal aging SST mRNA expression did not alter, but decreased in cancer (p < 0.05). The ratio of SST immunoreactive cells was significantly higher in children (0.70% ± 0.79%) compared to CRC (0% ± 0%) (p < 0.05). Octreotide significantly increased the proportion of apoptotic Caco-2 cells. SST showed significantly higher methylation level in tumor samples (30.2% ± 11.6%) compared to healthy young individuals (3.5% ± 1.9%) (p < 0.05).

CONCLUSIONS

In cancerous colonic mucosa the reduced SST production may contribute to the uncontrolled cell proliferation. Our observation that in colon cancer cells octreotide significantly enhanced cell death and attenuated cell proliferation suggests that SST may act as a regulator of epithelial cell kinetics. The inhibition of SST expression in CRC can be epigenetically regulated by promoter hypermethylation.

Opioids, Neutral Endopeptidase, its Inhibitors and Cancer: Is There a Relationship among them?

The role of endogenous animal opioids in the biology of cancer is widely recognized but poorly understood. This is, among others, because of the short half-life of these peptides, which are quickly inactivated by endopeptidases, e.g., neutral endopeptidase (NEP, CD10). It has been established that NEP is engaged in the modulation of the tumor microenvironment, among others that of colon cancer, by exerting influence on cell growth factors, the extracellular matrix and other biologically active substances. Although there are some discrepancies among the findings on the role of both opioids and NEP in cancer development, authors agree that their role seems to depend on the origin, stage and grade of tumor, and even on the method of examination. Moreover, recently, natural inhibitors of NEP, such as sialorphin, opiorphin and spinorphin have been detected. Their analgesic activity has been established. It is interesting to ask whether there is a relationship among opioid peptides, tumor-associated NEP and its inhibitors.

Adiponectin as novel regulator of cell proliferation in human glioblastoma

Adiponectin (Acrp30) is an adipocyte-secreted hormone with pleiotropic metabolic effects, whose reduced levels were related to development and progression of several malignancies. We looked at the presence of Acrp30 receptors in human glioblastomas (GBM), hypothesizing a role for Acrp30 also in this untreatable cancer. Here we demonstrate that human GBM express Acrp30 receptors (AdipoR1 and AdipoR2), which are often co-expressed in GBM samples (70% of the analyzed tumors). To investigate the effects of Acrp30 on GBM growth, we used human GBM cell lines U87-MG and U251, expressing both AdipoR1 and AdipoR2 receptors. In these cells, Acrp30 treatment inhibits DNA synthesis and cell proliferation rate, inducing arrest in G1 phase of the cell cycle. These effects were correlated to a sustained activation of ERK1/2 and Akt kinases, upon Acrp30 treatment. Our results suggest that Acrp30 may represent a novel endogenous negative regulator of GBM cell proliferation, to be evaluated for the possible development of novel pharmacological approaches.

Somatostatin ameliorates lipopolysaccharide-induced tight junction damage via the ERK-MAPK pathway in Caco2 cells

Dysfunction of the epithelial barrier is an important pathogenic factor of inflammatory bowel disease and other inflammatory conditions of the gut. Somatostatin (SST) has been demonstrated to reduce local and systemic inflammation reactions and maintain the integrity of the blood-brain barrier (BBB). To determine the beneficial effect of SST on lipopolysaccharide (LPS)-induced damage of the tight junction (TJ) and its mechanisms, Caco2 cells pretreated with SST (1nM) or MEK inhibitor U0126 (10μM) were exposed to LPS. LPS significantly reduced the expression of TJ proteins in a dose-dependent way. LPS (100μg/ml) greatly induced Caco2 monolayer barrier dysfunction by decreasing transepithelial resistance and increasing epithelial permeability. Pretreatment with SST effectively improved the barrier dysfunction of Caco2 cells. SST significantly increased the expression of TJ proteins occludin and ZO-1 and inhibited the redistribution of TJ proteins due to LPS stimulation. Furthermore, SST decreased the LPS-induced phosphorylation of ERK1/2, and a selective MEK inhibitor markedly protected the barrier function against LPS disturbance by blocking the activation of the ERK-MAPK pathway in Caco2 cells. Besides, LPS significantly increased the mRNA level of SSTR5, which was partly inhibited by pretreatment with SST. In conclusion, the present study indicates that SST protects the Caco2 monolayer barrier against LPS-induced tight junction breakdown by down-regulating the activation of the ERK-MAPK pathway and suppression the activation of SSTR5.

Comparative study of somatostatin-human serum albumin fusion proteins and natural somatostatin on receptor binding, internalization and activation

Albumin fusion technology, the combination of small molecular proteins or peptides with human serum albumin (HSA), is an effective method for improving the medicinal values of natural small molecular proteins or peptides. However, comparative studies between HSA-fusion proteins or peptides and the parent small molecules in biological and molecular mechanisms are less reported. In this study, we examined the binding property of two novel somatostatin-HSA fusion proteins, (SST14)₂-HSA and (SST28)₂-HSA, to human SSTRs in stably expressing SSTR1-5 HEK 293 cells; observed the regulation of receptor internalization and internalized receptor recycling; and detected the receptors activation of HSA fusion proteins in stably expressing SSTR2- and SSTR3-EGFP cells. We showed that both somatostatin-HSA fusion proteins had high affinity to all five SSTRs, stimulated the ERK1/2 phosphorylation and persistently inhibited the accumulation of forskolin-stimulated cAMP in SSTR2- and SSTR3-expressing cells; but were less potent than the synthetic somatostatin-14 (SST-14). Our experiments also showed that somatostatin-HSA fusion proteins did not induce the receptors internalization; rather, they accelerated the recycling of the internalized receptors induced by SST-14 to the plasma membrane. Our results indicated that somatostatin-HSA fusion proteins, different from SST-14, exhibit some particular properties in binding, regulating, and activating somatostatin receptors.

Effect of endogenous and exogenous gastrin on PGE2 and EGF expression in dimethylhydrazine-induced colorectal cancer in rats

AIM: To examine the effect of endogenous and exogenous gastrin on the expression of epidermal growth factor (EGF) and prostaglandin E₂ (PGE₂) in dimethylhydrazine-induced colorectal cancer in rats to explore the role of gastrin (GAS), cyclooxygenase (COX)-2, EGF, PGE₂, and EGF receptor (EGFR) in colorectal cancer.

METHODS: One hundred and forty rats were randomly divided into seven groups: DMH+GAS, DMH+PPI, DMH, DMH+GAS+PGL, DMH+PPI+PGL, DMH+PGL, and control group. The concentrations of GAS, EGF and PGE₂ in serum and large intestine tissue homogenate were determined by radioimmunoassay. The expression of COX-2 and EGFR in the large intestine tissue was detected by immunohistochemistry and quantified by optical density analysis.

RESULTS: The concentrations of GAS (pg/mL) in serum and large intestine tissue homogenate were significantly higher in the DMH+GAS (15.59 ± 2.90, 0.38 ± 0.11) and DMH+GAS+PGL (15.31 ± 5.66, 0.35 ± 0.10) groups than in the control group (8.64 ± 2.36, 0.16 ± 0.03) (all P < 0.05), and in DMH+PPI (20.50 ± 3.71, 0.45 ± 0.13) and DMH+PPI+PGL (19.90 ± 5.10, 0.37 ± 0.11) groups than in the DMH (13.12 ± 3.47, 0.19 ± 0.04), DMH+PGL (11.45 ± 5.13, 0.20 ± 0.05) and blank control groups (all P < 0.05). The concentrations of EGF (ng/mL) in serum and large intestine tissue homogenate were significantly higher in the DMH+GAS (4.26 ± 0.92, 0.011 ± 0.005) and DMH+GAS+PGL (4.29 ± 0.50, 0.009 ± 0.005) groups than in the control group (2.91 ± 0.54, 0.002 ± 0.0007) (all P < 0.05), and in DMH+PPI (5.20 ± 1.03, 0.015 ± 0.007) and DMH+PPI+PGL (5.13 ± 0.50, 0.011 ± 0.007) groups than in the DMH (3.76 ± 1.47, 0.004 ± 0.002), DMH+PGL (3.59 ± 1.12, 0.002 ± 0.0018) and control groups (all P < 0.05). The concentrations of PGE₂ (pg/mL) in serum and large intestine tissue homogenate were higher in the DMH+GAS (76.03 ± 60.75, 2.74 ± 0.76) and DMH+PPI (70.29 ± 66.58, 2.42 ± 0.89) groups than in other groups, but the differences were not statistically significant (all P > 0.05). Serum and tissue concentrations of GAS (32.06 pg/mg ± 15.84 pg/mg, 0.73 pg/mg ± 0.31 pg/mg), EGF (4.48 ng/mg ± 1.13 ng/mg, 0.045 ng/mg ± 0.020 ng/mg), PGE₂ (99.05 pg/mg ± 60.80 pg/mg, 4.27 pg/mg ± 1.17 pg/mg) in adenocarcinoma were higher than those in the control group (all P < 0.05). The IA of EGFR (17161.67 ± 9851.33) and COX-2 (21403.33 ± 11377.25) in the adenocarcinoma group was higher than that in the adenoma (5154.00 ± 2744.13, 7291.60 ± 2849.12) and control (3327.11 ± 1880.44, 4822.90 ± 2340.89) groups (all P < 0.05). The positive rates of EGFR (66.7%) and COX-2 (81.5%) expression in the adenocarcinoma group was higher than those in the control group (0%, 30%) (all P < 0.05).

CONCLUSION: Endogenous and exogenous gastrin could induce the expression of EGF and stimulate the secretion of PGE₂ in colorectal cancer. PGL does not inhibit the effect of GAS on EGF. GAS, EGF, PGE₂, EGFR, and COX-2 play an important role in the formation of colorectal cancer. EGFR and COX-2 are involved in the proliferation of colorectal tumors.

Peptide receptor targeting in cancer: the somatostatin paradigm

Peptide receptors involved in pathophysiological processes represent promising therapeutic targets. Neuropeptide somatostatin (SST) is produced by specialized cells in a large number of human organs and tissues. SST primarily acts as inhibitor of endocrine and exocrine secretion via the activation of five G-protein-coupled receptors, named sst1–5, while in central nervous system, SST acts as a neurotransmitter/neuromodulator, regulating locomotory and cognitive functions. Critical points of SST/SST receptor biology, such as signaling pathways of individual receptor subtypes, homo- and heterodimerization, trafficking, and cross-talk with growth factor receptors, have been extensively studied, although functions associated with several pathological conditions, including cancer, are still not completely unraveled. Importantly, SST exerts antiproliferative and antiangiogenic effects on cancer cells in vitro, and on experimental tumors in vivo. Moreover, SST agonists are clinically effective as antitumor agents for pituitary adenomas and gastro-pancreatic neuroendocrine tumors. However, SST receptors being expressed by tumor cells of various tumor histotypes, their pharmacological use is potentially extendible to other cancer types, although to date no significant results have been obtained. In this paper the most recent findings on the expression and functional roles of SST and SST receptors in tumor cells are discussed.

Immunohistochemical expression of somatostatin receptor subtypes 2 and 5 in colorectal cancer

BACKGROUND

  To determine the immunohistochemical expression levels of the somatostatin receptor subtypes 2 and 5 (Sst2 and Sst5) in patients with colorectal cancer (CRC) and to investigate the association of Sst2 and Sst5 expression with clinicopathological parameters.

MATERIALS AND METHODS

  A retrospective analysis of formalin-fixed and paraffin-embedded CRC surgical specimens from 81 patients assessed by immunohistochemistry for Sst2 and Sst5 expression.

RESULTS

  Sst2 and Sst5 expression levels showed significant, negative association with CRC invasion and liver metastasis (P values < 0·05) while Sst2 also showed significantly increased expression in lower-grade tumours as well as in tumours located in the rectum (P values < 0·05). Patients with CRC expressing either Sst2 or Sst5 had significantly longer survival rates (P values < 0·05), although Sst expression was not found to be an independent predictor of survival after controlling for other known prognostic clinicopathological variables (P values > 0·05).

CONCLUSIONS

  The present data confirm the relationship of Sst2 and Sst5 expression levels with reduced tumour aggressiveness.

Somatostatin receptors in non-neuroendocrine malignancies: the potential role of somatostatin analogs in solid tumors

Somatostatin receptors (sstrs) are G-protein-coupled receptors that mediate various physiological effects when activated by the neuropeptide somatostatin or its synthetic analogs. In addition to the well-documented antisecretory effects of sstr2-preferential somatostatin analogs octreotide and lanreotide, ligand binding to sstr initiates an inhibitory action on tumor growth. This effect may result from both indirect actions (suppression of growth factors and growth-promoting hormones [e.g., GH/IGF-1 axis] and inhibition of angiogenesis) and direct actions (activation of antigrowth activities [e.g., apoptosis]). As solid tumor cells express multiple sstrs, there is a rationale to evaluate the potential antitumor effects of pasireotide (SOM230), a multireceptor-targeted somatostatin analog with high binding affinity for sstr1–3 and sstr5. Pasireotide reduces systemic IGF-1 levels more potently than currently available somatostatin analogs and has been well tolerated in clinical trials.