Epidermal growth factor (EGF) regulates normal and tumor cell proliferation via epidermal growth factor receptor (EGFR) phosphorylation, homo- or heterodimerization and activation of ...mitogen-activated protein kinases (MAPKs) and PI3K/AKT cell survival pathways. In contrast, SST via activation of five different receptor subtypes inhibits cell proliferation and has been potential target in tumor treatment. To gain further insight for the effect of SSTRs on EGFR activated signaling, we determine the role of SSTR1 and SSTR1/5 in human embryonic kidney (HEK) 293 cells. We here demonstrate that cells transfected with SSTR1 or SSTR1/5 negatively regulates EGF mediated effects attributed to the inhibition of EGFR phosphorylation, MAPKs as well as the cell survival signaling. Furthermore, SSTR effects were significantly enhanced in cells when EGFR was knock down using siRNA or treated with selective antagonist (AG1478). Most importantly, the presence of SSTR in addition to modulating signaling pathways leads to the dissociation of the constitutive and EGF induced heteromeric complex of EGFR/ErbB2. Furthermore, cells cotransfected with SSTR1/5 display pronounced effect of SST on the signaling and dissociation of the EGFR/ErbB2 heteromeric complex than the cells expressing SSTR1 alone. Taken together this study provides the first evidence that the presence of SSTR controls EGF mediated cell survival pathway via dissociation of ErbB heteromeric complex. We propose that the activation of SSTR and blockade of EGFR might serve novel therapeutic approach in inhibition of tumor proliferation.
► In this study we demonstrate the activation of SSTRs inhibits epidermal growth factor mediated EGFR phosphorylation and mitogen-activated protein kinases. ► The presence of SSTRs blocks the epidermal growth factor mediated PI3K/AKT cell survival pathway. ► SSTRs in receptor-specific manner impede the epidermal growth factor stimulated heterodimerization between EGFR and ErbB2.
In the present experimental investigation, the specimens were fabricated using 3D printing (fused deposition modeling) and injection molding techniques. The process parameters were optimized to ...fabricate the good quality polylactic acid (PLA) specimens as per ASTM standards. The effect of variation (80, 90, and 100%) of the infill density on the mechanical performance of developed specimens was analyzed. The mechanical behavior of the fabricated specimens was compared in the context of tensile, flexural, and impact properties. The thermal stability and crystallinity of the PLA specimens have been investigated using thermogravimetric and XRD analysis, respectively. After tensile testing, the surface of the fractured specimens was observed using a scanning electron microscope. The tensile and flexural strength of the 3D-printed specimens was superior to the injection-molded specimens. An improvement in stiffness of the 3D-printed specimens has been observed. Moreover, the printed specimens showed better thermal stability than the molded specimens. There was no significant variation in the crystallinity of the printed and molded specimens. It can be concluded that the tensile, flexural, and thermal responses of the 3D-printed specimens are better than injection-molded specimens at the optimal combination of process parameters.
Breast cancer is the most commonly diagnosed cancer and a leading cause of cancer-related death among women worldwide. Somatostatin (SST) and Cannabinoids have an anti-proliferative and pro-apoptotic ...effect, but the mechanisms of their actions remain elusive. In the present study, we have evaluated the effects of SST, Cannabidiol (CBD) alone or in combination on receptor expression, cell proliferation and apoptosis and related downstream signalling pathways in MDA-MB-231 and MCF-7 breast cancer cells. The results presented here demonstrate the cell type and agonist-dependent changes in receptor expression at the cell membrane, inhibition of cell proliferation and increased apoptosis following treatment with SST and CBD alone and in combination. In comparison to MDA-MB-231 cells, MCF-7 cells treated with SST alone and in combination with CBD exhibited inhibition of phosphorylated Protein Kinase B (pAKT) and phosphorylated-Phosphoinositide 3-Kinase (pPI3K) expression. Importantly, inhibition of PI3K/AKT activation was accompanied by enhanced PTEN expression in MCF-7 cells. These results highlight the possible interaction between SSTR and CBR subtypes with the implication in the modulation of receptor expression, cell viability and signal transduction pathways in a breast cancer cell type-dependent manner.
•Breast cancer is the leading cause of cancer-related death among women worldwide.•Somatostatin and Cannabinoids displayed an anti-proliferative and pro-apoptotic effect in the cancer cell lines.•SST with or without CBD exhibited inhibition of signalling pathways associated with cell proliferation.•Our results indicate the possibility of SSTRs and CBRs crosstalk as novel therapeutic target in breast cancer treatment.
Glaucoma is characterized by progressive damage of the retinal ganglion cells (RGCs), resulting in irreversible vision loss. Cannabinoids (CBs) ameliorate several factors that contribute to the ...progression of glaucoma, including increased intraocular pressure (IOP), degeneration of RGC and optical nerve (ON) damage. However, a direct correlation of specific CBs with the molecular events pertaining to glaucoma pathology is not well established. Therefore, this study aims to evaluate the role of cannabinol (CBN) on RGC protection, modulation of IOP, and its effects on the level of extracellular matrix (ECM) proteins using both in vitro and in vivo models of glaucoma.
When exposed to elevated hydrostatic pressure, CBN, in a dose-dependent manner, protected differentiated mouse 661W retinal ganglion precursor-like cells from pressure-induced toxicity. In human trabecular meshwork cells (hTM), CBN attenuated changes in the ECM proteins, including fibronectin and α-smooth muscle actin (α-SMA), as well as mitogen-activated protein kinases (phospho-ERK1/2) in the presence or absence of transforming growth factor-beta 2 (TGF-β2) induced stress. Ocular pharmacokinetic parameters were evaluated post-intravitreal (IVT) CBN delivery in vivo. Furthermore, we demonstrated that IVT-administered CBN improved pattern electroretinogram (pERG) amplitudes and reduced IOP in a rat episcleral vein laser photocoagulation model of glaucoma.
CBN promotes neuroprotection, abrogates changes in ECM protein, and normalizes the IOP levels in the eye. Therefore, our observations in the present study indicate a therapeutic potential for CBN in the treatment of glaucoma.
•The role of CBN in glaucoma pathology was evaluated using in vitro and in vivo experimental models.•CBN promotes 661W cell survival and abrogates changes in ECM protein expression in hTM cells.•CBN lowers IOP and normalizes pERG in rat episcleral vein laser photocoagulation glaucoma model.•These results suggest CBN as a potential therapeutic intervention for patients with glaucoma.
Lung cancer is the most common cause of cancer deaths, its global incidence is rising, and continuing rises are predicted. The potential to diagnose lung cancers based on the determination of ...volatile organic compounds (VOCs) in human breath has been attracting increasing attention with the development of new techniques and methodologies. However, despite many reports of VOC profiling in lung cancer patients, little is known about how specific biomarkers relate to the biochemical pathways involved in lung cancer development, and there is still no reliable method for diagnosing lung cancer at the early stages. This review summarizes some of the latest methods used for monitoring biomarkers in lung cancer patients, which could be applicable for clinical diagnosis. Techniques for capturing and pre-concentrating biomarkers, and the technologies used for subsequently determining them, are also discussed.
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•Methods for determination of volatile organic compounds (VOC).•VOC as potential markers for early diagnosis of lung cancer.•Review of sample pretreatment and analytical methods used.
Somatostatin receptor (SSTR) expression is positively correlated with tumor size and inversely correlated with epidermal growth factor receptor (ErbB) levels and tumor differentiation. In the present ...study, we compared SSTR1-5 and ErbB1-4 mRNA and protein expression in two breast cancer cell lines: MCF-7 (ER+) and MDA-MB-231 (ERalpha-).
All five SSTRs and four ErbBs were variably expressed as both cell surface and cytoplasmic proteins. In both cell lines, SSTR4 and SSTR1 were highly expressed, followed by SSTR2 and SSTR5 with SSTR3 being the least expressed subtype, at the protein level. ErbBs were variably expressed with ErbB1 as the predominant subtype in both cell lines. ErbB1 is followed by ErbB3, ErbB2 and ErbB4 in MCF-7 at both the protein and mRNA levels. In MDA-MB-231 cells, ErbB1 is followed by ErbB2, ErbB4 and ErbB3. Our results indicate significant correlations at the level of mRNA and protein expression in a cell and receptor-specific manner. Using indirect immunofluorescence, we found that, in MCF-7 cells, SSTR5 was the most prominent subtype coexpressed with ErbBs followed by SSTR3, SSTR4, SSTR1 and SSTR2, respectively. In MDA-MB-231 cells, SSTR1 colocalized strongly with ErbBs followed by SSTR5, SSTR4, SSTR3 and SSTR2. ErbBs displayed higher levels of colocalization amongst themselves in MCF-7 cells than in MDA-MB-231 cells.
These findings may explain the poor response to endocrine therapy in ER-cancer. Differential distribution of SSTR subtypes with ErbBs in breast cancer cells in a receptor-specific manner may be considered as a novel diagnosis for breast tumors.
Somatostatin and Somatostatin Receptors Kumar, Ujendra; Grant, Michael
Cellular Peptide Hormone Synthesis and Secretory Pathways,
01/2010, Letnik:
50
Book Chapter, Journal Article
The biological effects of somatostatin (SST) were first encountered unexpectedly in the late 1960s in two unrelated studies, one by Krulich et al. (1968) who reported on a growth hormone ...(GH)-releasing inhibitory substance from hypothalamic extracts, and the other, by Hellman and Lernmark (1969), on the presence of a potent insulin inhibitory factor from the extracts of pigeon pancreatic islets. However, the inhibitory substance was not officially identified until 1973 by Guillemin’s group (Brazeau et al. 1973). In both synthetic and naturally occurring forms, this tetradecapeptide, originally coined as somatotropin release-inhibitory factor (SRIF, SST-14) was shown by Brazeau et al. to be the substance controlling hypothalamic GH release. This single achievement not only pioneered SST research but was also duly recognized, as Guillemin shared the 1977 Nobel Prize in Medicine. The following years bequeathed an exponential increase in SST-related studies. It soon became clear that SST-synthesis was not restricted to the hypothalamus. Its production is widely distributed throughout the central nervous system (CNS), peripheral neurons, the gastrointestinal tract, and the pancreatic islets of Langerhans (Luft et al. 1974; Arimura et al. 1975; Dubois 1975; Hokfelt et al. 1975; Orci et al. 1975; Pelletier et al. 1975; Polak et al. 1975; Patel and Reichlin 1978). In fact, SST-like immunoreactivity can be found throughout various tissues of vertebrates and invertebrates, including the plant kingdom (Patel 1992; Tostivint et al. 2004). Given its broad anatomical distribution, it is no wonder that SST produces a wide spectrum of biological effects. Generally regarded as an inhibitory factor, SST can function either locally on neighboring cells or distantly through the circulation, to regulate such physiological processes as glandular secretion, neurotransmission, smooth muscle contractility, nutrient absorption, and cell division (Reichlin 1983a, b; Patel 1992, 1999; Patel et al. 2001; Barnett 2003).
Somatostatin (SST) is a multifunctional peptide and involves in several neurodegenerative diseases.
N
-Methyl-
d
-asparate (NMDA) receptor agonist quinolinic acid (QUIN)-induced neurotoxicity mimics ...an experimental model of Huntington’s disease that is characterized by the selective preservation of medium-sized aspiny interneurons and degeneration of medium-sized spiny projection neurons in striatum. In QUIN- and NMDA-induced neurotoxicity, increased expression of SST and messenger RNA levels along with SST release in culture medium is generally observed. However, the molecular mechanisms and the functional consequences of increased SST are still obscure. In the present study, the role of SST was determined using immunoneutralization and immunoblockade of SST in cultured striatal neurons upon QUIN- and NMDA-induced neurotoxicity. The immunoblockade of SST with antisense oligonucleotides and immunoabsorption of released SST with specific antibodies potentiate QUIN- and NMDA-induced neuronal cell death. NADPH–diaphorase positive neurons that are selectively spared in several processes of neurodegeneration result in severe damage upon immunoblockade or immunoabsorption of SST. In addition, exogenous SST along with QUIN and NMDA provides selective preservation of projection neurons, which are selectively susceptible in excitotoxicity. Neuroprotective effect of SST is completely blocked by pertussis toxins, suggesting the role of somatostatin receptors. Taken together, these results provide first evidence that the presence of SST is a unique feature for the selective sparing of medium sized aspiny interneurons in excitotoxicity.
Somatostatin (SST) analogs have been successfully used in the medical treatment of acromegaly, caused by GH hypersecreting pituitary adenomas. Patients on SST analogs rarely develop tachyphylaxis ...despite years of continuous administration. It has been recently proposed that a functional association between SST receptor (SSTR) subtypes 2 and 5 exists to account for this behavior; however, a physical interaction has yet to be identified. Using both coimmunoprecipitation and photobleaching fluorescence resonance energy transfer microscopy techniques, we determined that SSTR2 and SSTR5 heterodimerize. Surprisingly, selective activation of SSTR2 and not SSTR5, or their costimulation, modulates the association. The SSTR2-selective agonist L-779,976 is more efficacious at inhibiting adenylate cyclase, activating ERK1/2, and inducing the cyclin-dependent kinase inhibitor p27Kip1 in cells expressing both SSTR2 and SSTR5 compared with SSTR2 alone. Furthermore, cell growth inhibition by L-779,976 treatment was markedly extended in coexpressing cells. Trafficking of SSTR2 is also affected upon heterodimerization, an attribute corresponding to modifications in β-arrestin association kinetics. Activation of SSTR2 results in the recruitment and stable association of β-arrestin, followed by receptor internalization and intracellular receptor pooling. In contrast, heterodimerization increases the recycling rate of internalized SSTR2 by destabilizing its interaction with β-arrestin. Given that SST analogs show preferential binding to SSTR2, these data provide a mechanism for their effectiveness in controlling pituitary tumors and the absence of tolerance seen in patients undergoing long-term administration.
Highlights • SSTR5 and CB1R exist as constitutive heterodimers in rat brain regions and cotransfected HEK-293 cells. • Concurrent receptor activation leads to preferential disruption of SSTR5/CB1R ...heterodimer and formation of SSTR5 homodimer. • SSTR5 plays the major role in the regulation of cAMP/PKA/ERK1/2 signaling pathways in cotransfected cells. • Time course of PI3K phosphorylation is altered upon concurrent receptor activation.
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