1
|
Nguyen DH. Role of Endorphins in Breast Cancer Pathogenesis and Recovery. ADVANCES IN NEUROBIOLOGY 2024; 35:87-106. [PMID: 38874719 DOI: 10.1007/978-3-031-45493-6_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2024]
Abstract
Understanding the relationship between stress and breast cancer development is essential to preventing and alleviating the cancer. Recent research has shed light on the cognitive, physiological, cellular, and molecular underpinnings of how the endorphin pathway and stress pathway affect breast cancer. This chapter consists of two parts. Part 1 will discuss the role of endorphins in breast cancer development. This includes a discussion of three topics: (1) the neurophysiological effect of endorphins on breast tumor growth in vivo, along with further experiments that will deepen our knowledge of how β-endorphin affects breast cancer; (2) how both the opioid receptor and somatostatin receptor classes alter intracellular signaling in breast cancer cells; and (3) genetic alleles in the opioid signaling pathway that are correlated with increased breast cancer risk. Part 2 will discuss the role of endorphins in recovery from breast cancer. This includes a discussion of three topics: (1) the relationship between breast cancer diagnosis and depression; (2) the effectiveness of cognitive behavioral therapy in reducing stress in breast cancer patients; and (3) the effect of psychotherapy and exercise on preserving telomere length in breast cancer patients.
Collapse
Affiliation(s)
- David H Nguyen
- BrainScanology, Inc, Concord, CA, USA.
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
| |
Collapse
|
2
|
Milewska-Kranc A, Ćwikła JB, Kolasinska-Ćwikła A. The Role of Receptor-Ligand Interaction in Somatostatin Signaling Pathways: Implications for Neuroendocrine Tumors. Cancers (Basel) 2023; 16:116. [PMID: 38201544 PMCID: PMC10778465 DOI: 10.3390/cancers16010116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/19/2023] [Accepted: 12/22/2023] [Indexed: 01/12/2024] Open
Abstract
Neuroendocrine tumors (NETs) arise from neuroendocrine cells and manifest in diverse organs. Key players in their regulation are somatostatin and its receptors (SSTR1-SSTR5). Understanding receptor-ligand interactions and signaling pathways is vital for elucidating their role in tumor development and therapeutic potential. This review highlights SSTR characteristics, localization, and expression in tissues, impacting physiological functions. Mechanisms of somatostatin and synthetic analogue binding to SSTRs, their selectivity, and their affinity were analyzed. Upon activation, somatostatin initiates intricate intracellular signaling, involving cAMP, PLC, and MAP kinases and influencing growth, differentiation, survival, and hormone secretion in NETs. This review explores SSTR expression in different tumor types, examining receptor activation effects on cancer cells. SSTRs' significance as therapeutic targets is discussed. Additionally, somatostatin and analogues' role in hormone secretion regulation, tumor growth, and survival is emphasized, presenting relevant therapeutic examples. In conclusion, this review advances the knowledge of receptor-ligand interactions and signaling pathways in somatostatin receptors, with potential for improved neuroendocrine tumor treatments.
Collapse
Affiliation(s)
| | - Jarosław B. Ćwikła
- School of Medicine, University of Warmia and Mazury, Aleja Warszawska 30, 10-082 Olsztyn, Poland
- Diagnostic Therapeutic Center–Gammed, Lelechowska 5, 02-351 Warsaw, Poland
| | | |
Collapse
|
3
|
Sosa LDV, Picech F, Perez P, Gutierrez S, Leal RB, De Paul A, Torres A, Petiti JP. Regulation of FGF2-induced proliferation by inhibitory GPCR in normal pituitary cells. Front Endocrinol (Lausanne) 2023; 14:1183151. [PMID: 37576961 PMCID: PMC10414184 DOI: 10.3389/fendo.2023.1183151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 07/13/2023] [Indexed: 08/15/2023] Open
Abstract
Introduction Intracellular communication is essential for the maintenance of the anterior pituitary gland plasticity. The aim of this study was to evaluate whether GPCR-Gαi modulates basic fibroblast growth factor (FGF2)-induced proliferative activity in normal pituitary cell populations. Methods Anterior pituitary primary cell cultures from Wistar female rats were treated with FGF2 (10ng/mL) or somatostatin analog (SSTa, 100nM) alone or co-incubated with or without the inhibitors of GPCR-Gαi, pertussis toxin (PTX, 500nM), MEK inhibitor (U0126, 100µM) or PI3K inhibitor (LY 294002, 10 μM). Results FGF2 increased and SSTa decreased the lactotroph and somatotroph BrdU uptak2e (p<0.05) whereas the FGF2-induced S-phase entry was prevented by SSTa co-incubation in both cell types, with these effects being reverted by PTX, U0126 or LY294002 pre-incubation. The inhibition of lactotroph and somatotroph mitosis was associated with a downregulation of c-Jun expression, a decrease of phosphorylated (p) ERK and pAKT. Furthermore, SSTa was observed to inhibit the S-phase entry induced by FGF2, resulting in a further increase in the number of cells in the G1 phase and a concomitant reduction in the number of cells in the S phases (p< 0.05), effects related to a decrease of cyclin D1 expression and an increase in the expression of the cell cycle inhibitors p27 and p21. Discussion In summary, the GPCR-Gαi activated by SSTa blocked the pro-proliferative effect of FGF2 in normal pituitary cells via a MEK-dependent mechanism, which acts as a mediator of both anti and pro-mitogenic signals, that may regulate the principal effectors of the G1 to S-phase transition.
Collapse
Affiliation(s)
- Liliana del V. Sosa
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
| | - Florencia Picech
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
| | - Pablo Perez
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
| | - Silvina Gutierrez
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
| | - Rodrigo Bainy Leal
- Universidade Federal de Santa Catarina, Florianópolis, Departamento de Bioquímica e Programa de Pós-graduação em Bioquímica, Centro de Ciências Biológicas, Santa Catarina, Brazil
| | - Ana De Paul
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
| | - Alicia Torres
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
| | - Juan Pablo Petiti
- Universidad Nacional de Córdoba, Facultad de Ciencias Médicas, Centro de Microscopía Electrónica, Córdoba, Argentina
- Consejo Nacional de Investigaciones Científicas Técnicas (CONICET), Instituto de Investigaciones en Ciencias de la Salud (INICSA), Córdoba, Argentina
| |
Collapse
|
4
|
Anti-inflammatory Effect of Somatostatin Analogue Octreotide on Rheumatoid Arthritis Synoviocytes. Inflammation 2018; 41:1648-1660. [DOI: 10.1007/s10753-018-0808-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
|
5
|
War SA, Kim B, Kumar U. Human somatostatin receptor-3 distinctively induces apoptosis in MCF-7 and cell cycle arrest in MDA-MB-231 breast cancer cells. Mol Cell Endocrinol 2015; 413:129-44. [PMID: 26112183 DOI: 10.1016/j.mce.2015.06.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 06/12/2015] [Accepted: 06/17/2015] [Indexed: 12/29/2022]
Abstract
Somatostatin (SST) mediates cytostatic and pro-apoptotic effects through five somatostatin receptors (SSTR1-5). The modest clinical benefits of SST analogs in cancers of different origin such as breast cancer are attributed to diminished SSTRs expression at tumor sites. In the present study, SSTR3 was overexpressed in MCF-7 and MDA-MB-231, and analyzed for downstream signaling molecules associated with cytostatic and cytotoxic effect. Cells overexpressing SSTR3 displayed inhibition of EGF induced proliferation and enhanced antiproliferative effect of SSTR3-specific agonist in comparison to non-transfected cells. SSTR3 overexpression in MCF-7 cells (R3-MCF-7) constitutively enhanced TUNEL staining, PARP-1 and p27(Kip1) expression suggesting apoptosis and cell-cycle arrest. Conversely, R3-MB-231 cells with SSTR3 overexpression exerted cytostatic and were devoid of any cytotoxic effects. The expression of PTP-1C and the status of ERK1/2, p38 and PI3K phosphorylation was modulated in a cell-specific manner. These findings provide new insights in understanding the antiproliferative role of SSTR3 in breast tumor biology.
Collapse
Affiliation(s)
- Sajad A War
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Brian Kim
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Ujendra Kumar
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
| |
Collapse
|
6
|
Misawa K, Misawa Y, Kondo H, Mochizuki D, Imai A, Fukushima H, Uehara T, Kanazawa T, Mineta H. Aberrant methylation inactivates somatostatin and somatostatin receptor type 1 in head and neck squamous cell carcinoma. PLoS One 2015; 10:e0118588. [PMID: 25734919 PMCID: PMC4348545 DOI: 10.1371/journal.pone.0118588] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 01/21/2015] [Indexed: 01/16/2023] Open
Abstract
PURPOSE The aim of this study was to define somatostatin (SST) and somatostatin receptor type 1 (SSTR1) methylation profiles for head and neck squamous cell carcinoma (HNSCC) tumors at diagnosis and follow up and to evaluate their prognostic significance and value as a biomarker. METHODS Gene expression was measured by quantitative RT-PCR. Promoter methylation status was determined by quantitative methylation-specific PCR (Q-MSP) in HNSCC. RESULTS Methylation was associated with transcription inhibition. SST methylation in 81% of HNSCC tumor specimens significantly correlated with tumor size (P = 0.043), stage (P = 0.008), galanin receptor type 2 (GALR2) methylation (P = 0.041), and tachykinin-1 (TAC1) (P = 0.040). SSTR1 hypermethylation in 64% of cases was correlated with tumor size (P = 0.037), stage (P = 0.037), SST methylation (P < 0.001), and expression of galanin (P = 0.03), GALR2 (P = 0.014), TAC1 (P = 0.023), and tachykinin receptor type 1 (TACR1) (P = 0.003). SST and SSTR1 promoter hypermethylation showed highly discriminating receiver operator characteristic curve profiles, which clearly distinguished HNSCC from adjacent normal mucosal tissues. Concurrent hypermethylation of galanin and SSTR1 promoters correlated with reduced disease-free survival (log-rank test, P = 0.0001). Among patients with oral cavity and oropharynx cancer, methylation of both SST and SSTR1 promoters correlated with reduced disease-free survival (log-rank test, P = 0.028). In multivariate logistic-regression analysis, concomitant methylation of galanin and SSTR1 was associated with an odds ratio for recurrence of 12.53 (95% CI, 2.62 to 59.8; P = 0.002). CONCLUSIONS CpG hypermethylation is a likely mechanism of SST and SSTR1 gene inactivation, supporting the hypothesis that SST and SSTR1 play a role in the tumorigenesis of HNSCC and that this hypermethylation may serve as an important biomarker.
Collapse
MESH Headings
- Adult
- Aged
- Aged, 80 and over
- Biomarkers, Tumor/genetics
- Biomarkers, Tumor/metabolism
- Carcinoma, Squamous Cell/diagnosis
- Carcinoma, Squamous Cell/genetics
- Carcinoma, Squamous Cell/mortality
- Carcinoma, Squamous Cell/pathology
- CpG Islands
- DNA Methylation
- Female
- Galanin/genetics
- Galanin/metabolism
- Gene Expression Regulation, Neoplastic
- Head and Neck Neoplasms/diagnosis
- Head and Neck Neoplasms/genetics
- Head and Neck Neoplasms/mortality
- Head and Neck Neoplasms/pathology
- Humans
- Male
- Middle Aged
- Mouth Neoplasms/diagnosis
- Mouth Neoplasms/genetics
- Mouth Neoplasms/mortality
- Mouth Neoplasms/pathology
- Neoplasm Staging
- Odds Ratio
- Oropharyngeal Neoplasms/diagnosis
- Oropharyngeal Neoplasms/genetics
- Oropharyngeal Neoplasms/mortality
- Oropharyngeal Neoplasms/pathology
- Promoter Regions, Genetic
- Receptor, Galanin, Type 2/genetics
- Receptor, Galanin, Type 2/metabolism
- Receptors, Somatostatin/genetics
- Receptors, Somatostatin/metabolism
- Retrospective Studies
- Risk Factors
- Somatostatin/genetics
- Somatostatin/metabolism
- Squamous Cell Carcinoma of Head and Neck
- Survival Analysis
- Tachykinins/genetics
- Tachykinins/metabolism
- Transcription, Genetic
Collapse
Affiliation(s)
- Kiyoshi Misawa
- Department of Otolaryngology/Head and Neck Surgery, Hamamatsu University School of Medicine, Shizuoka, Japan
- * E-mail:
| | - Yuki Misawa
- Department of Otolaryngology/Head and Neck Surgery, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Haruki Kondo
- Department of Otolaryngology/Head and Neck Surgery, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Daiki Mochizuki
- Department of Otolaryngology/Head and Neck Surgery, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Atsushi Imai
- Department of Otolaryngology/Head and Neck Surgery, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Hirofumi Fukushima
- Department of Head and Neck, Cancer Institute Hospital of Japanese Foundation for Cancer Research, Tokyo, Japan
| | - Takayuki Uehara
- Department of Otorhinolaryngology, Head and Neck Surgery, Graduate school of Medicine, University of the Ryukyus, Okinawa, Japan
| | - Takeharu Kanazawa
- Department of Otolaryngology/Head and Neck Surgery, Jichi Medical University, Shimotsuke, Japan
| | - Hiroyuki Mineta
- Department of Otolaryngology/Head and Neck Surgery, Hamamatsu University School of Medicine, Shizuoka, Japan
| |
Collapse
|
7
|
Tiscornia MM, González HS, Lorenzati MA, Zapata PD. Association Between Methylation of SHP-1 Isoform I and SSTR2A Promoter Regions with Breast and Prostate Carcinoma Development. Cancer Invest 2015; 33:61-9. [DOI: 10.3109/07357907.2014.1001892] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
8
|
Stumm R. Somatostatin receptor sst2 reduces Akt activity and aggravates hypoxic/ischemic death in cerebral cortical neurons. Neuropharmacology 2014; 77:249-56. [DOI: 10.1016/j.neuropharm.2013.10.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 09/16/2013] [Accepted: 10/07/2013] [Indexed: 10/26/2022]
|
9
|
Kharmate G, Rajput PS, Lin YC, Kumar U. Inhibition of tumor promoting signals by activation of SSTR2 and opioid receptors in human breast cancer cells. Cancer Cell Int 2013; 13:93. [PMID: 24059654 PMCID: PMC3852783 DOI: 10.1186/1475-2867-13-93] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 08/23/2013] [Indexed: 12/31/2022] Open
Abstract
Background Somatostatin receptors (SSTRs) and opioid receptors (ORs) belong to the superfamily of G-protein coupled receptors and function as negative regulators of cell proliferation in breast cancer. In the present study, we determined the changes in SSTR subtype 2 (SSTR2) and μ, δ and κ-ORs expression, signaling cascades and apoptosis in three different breast cancer cells namely MCF-7, MDA-MB231 and T47D. Methods Immunocytochemistry and western blot analysis were employed to study the colocalization and changes in MAPKs (ERK1/2 and p38), cell survival pathway (PI3K/AKT) and tumor suppressor proteins (PTEN and p53) in breast cancer cell lines. The nature of cell death upon activation of SSTR2 or OR was analysed using flow cytometry analysis. Results The activation of SSTR2 and ORs modulate MAPKs (ERK1/2 and p38) in cell dependent and possibly estrogen receptor (ER) dependent manner. The activation of tumor suppressor proteins phosphatase and tensin homolog (PTEN) and p53 antagonized the PI3K/AKT cell survival pathway. Flow cytometry analyses reveal increased necrosis as opposed to apoptosis in MCF-7 and T47D cells when compared to ER negative MDA-MB231 cells. Furthermore, receptor and agonist dependent expression of ORs in SSTR2 immunoprecipitate suggest that SSTR2 and ORs might interact as heterodimers and inhibit epidermal growth factor receptor phosphorylation. Conclusion Taken together, findings indicate a new role for SSTR2/ORs in modulation of signaling pathways involved in cancer progression and provide novel therapeutic approaches in breast cancer treatment.
Collapse
Affiliation(s)
- Geetanjali Kharmate
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC V6T1Z3, Canada.
| | | | | | | |
Collapse
|
10
|
Peptide receptor targeting in cancer: the somatostatin paradigm. INTERNATIONAL JOURNAL OF PEPTIDES 2013; 2013:926295. [PMID: 23476673 PMCID: PMC3582104 DOI: 10.1155/2013/926295] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Revised: 12/10/2012] [Accepted: 12/28/2012] [Indexed: 02/06/2023]
Abstract
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.
Collapse
|
11
|
G Protein-Coupled Receptors in cancer: biochemical interactions and drug design. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 115:143-73. [PMID: 23415094 DOI: 10.1016/b978-0-12-394587-7.00004-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
G Protein-Coupled Receptors (GPCRs) share the same topology made of seven-transmembrane segments and represent the largest family of membrane receptors. Initially associated with signal transduction in differentiated cells, GPCRs and heterotrimeric G proteins were shown to behave as proto-oncogenes whose overexpression or activating mutations confer transforming properties. The first part of this review focuses on the link between biochemical interactions of a GPCR with other receptors, such as dimerization or multiprotein complexes, and their oncogenic properties. Alteration of these interactions or deregulation of transduction cascades can promote uncontrolled cell proliferation or cell transformation that leads to tumorigenicity and malignancy. The second part concerns the design of drugs specifically targeting these complex interactions and their promise in cancer therapy.
Collapse
|
12
|
Pavel M. Translation of molecular pathways into clinical trials of neuroendocrine tumors. Neuroendocrinology 2013; 97:99-112. [PMID: 22508344 DOI: 10.1159/000336089] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 12/08/2011] [Indexed: 12/20/2022]
Abstract
Current treatment options for neuroendocrine tumors (NET) include somatostatin analogs, interferon-α, peptide receptor-targeted therapy and cytotoxic chemotherapy. Most patients undergo sequential therapies since these drugs are active only in subpopulations of patients and for a limited period of time. There is a need for novel drugs that are capable of amelioration of symptomatology (syndromic control) and/or tumor growth control. A number of diverse signaling pathways are involved in the pathogenesis of NET and tumor growth, thus many potential targets are available for drug targeting. Targeted therapies therefore represent an appropriate developmental therapeutic strategy given the multiplicity of potential targets in NET. These include but are not limited to: inhibitory or activating G protein-coupled receptors, receptor tyrosine kinases, ligands, and intracellular targets such as the mammalian target of rapamycin (mTOR). Numerous drugs that utilize single or multiple targets are currently in clinical development. Recently, two target-directed agents, the multiple tyrosine kinase inhibitor sunitinib and the mTOR inhibitor everolimus, have been approved for the treatment of progressive pancreatic NET. This review provides a broad overview of established and potential molecular targets in NET, summarizes data from phase II and III clinical trials with targeted drugs and outlines future therapeutic directions.
Collapse
Affiliation(s)
- Marianne Pavel
- Department of Hepatology and Gastroenterology, Charité University Medicine, Berlin, Germany
| |
Collapse
|
13
|
War SA, Kumar U. Coexpression of human somatostatin receptor-2 (SSTR2) and SSTR3 modulates antiproliferative signaling and apoptosis. J Mol Signal 2012; 7:5. [PMID: 22651821 PMCID: PMC3403965 DOI: 10.1186/1750-2187-7-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Accepted: 05/31/2012] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Somatostatin (SST) via five Gi coupled receptors namely SSTR1-5 is known to inhibit cell proliferation by cytostatic and cytotoxic mechanisms. Heterodimerization plays a crucial role in modulating the signal transduction pathways of SSTR subtypes. In the present study, we investigated human SSTR2/SSTR3 heterodimerization, internalization, MAPK signaling, cell proliferation and apoptosis in HEK-293 cells in response to SST and specific agonists for SSTR2 and SSTR3. RESULTS Although in basal conditions, SSTR2 and SSTR3 colocalize at the plasma membrane and exhibit heterodimerization, the cell surface distribution of both receptors decreased upon agonist activation and was accompanied by a parallel increase in intracellular colocalization. Receptors activation by SST and specific agonists significantly decreased cAMP levels in cotransfected cells in comparison to control. Agonist-mediated modulation of pERK1/2 was time and concentration-dependent, and pronounced in serum-deprived conditions. pERK1/2 was inhibited in response to SST; conversely receptor-specific agonist treatment caused inhibition at lower concentration and activation at higher concentration. Strikingly, ERK1/2 phosphorylation was sustained upon prolonged treatment with SST but not with receptor-specific agonists. On the other hand, SST and receptor-specific agonists modulated p38 phosphorylation time-dependently. The receptor activation in cotransfected cells exhibits Gi-dependent inhibition of cell proliferation attributed to increased PARP-1 expression and TUNEL staining, whereas induction of p21 and p27Kip1 suggests a cytostatic effect. CONCLUSION Our study provides new insights in SSTR2/SSTR3 mediated signaling which might help in better understanding of the molecular interactions involving SSTRs in tumor biology.
Collapse
Affiliation(s)
- Sajad A War
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.
| | | |
Collapse
|
14
|
Somvanshi RK, Kumar U. Pathophysiology of GPCR Homo- and Heterodimerization: Special Emphasis on Somatostatin Receptors. Pharmaceuticals (Basel) 2012; 5:417-46. [PMID: 24281555 PMCID: PMC3763651 DOI: 10.3390/ph5050417] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 04/18/2012] [Accepted: 04/19/2012] [Indexed: 12/19/2022] Open
Abstract
G-protein coupled receptors (GPCRs) are cell surface proteins responsible for translating >80% of extracellular reception to intracellular signals. The extracellular information in the form of neurotransmitters, peptides, ions, odorants etc is converted to intracellular signals via a wide variety of effector molecules activating distinct downstream signaling pathways. All GPCRs share common structural features including an extracellular N-terminal, seven-transmembrane domains (TMs) linked by extracellular/intracellular loops and the C-terminal tail. Recent studies have shown that most GPCRs function as dimers (homo- and/or heterodimers) or even higher order of oligomers. Protein-protein interaction among GPCRs and other receptor proteins play a critical role in the modulation of receptor pharmacology and functions. Although ~50% of the current drugs available in the market target GPCRs, still many GPCRs remain unexplored as potential therapeutic targets, opening immense possibility to discover the role of GPCRs in pathophysiological conditions. This review explores the existing information and future possibilities of GPCRs as tools in clinical pharmacology and is specifically focused for the role of somatostatin receptors (SSTRs) in pathophysiology of diseases and as the potential candidate for drug discovery.
Collapse
Affiliation(s)
- Rishi K Somvanshi
- Faculty of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, The University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.
| | | |
Collapse
|
15
|
Kumar U. Cross-talk and modulation of signaling between somatostatin and growth factor receptors. Endocrine 2011; 40:168-80. [PMID: 21870170 DOI: 10.1007/s12020-011-9524-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 08/11/2011] [Indexed: 12/19/2022]
Abstract
The process of homo- and/or heterodimerization of G-protein coupled receptors (GPCRs) and receptor tyrosine kinase (RTK) families are crucial for implicating the fundamental properties of receptor proteins including receptor expression, trafficking, and desensitization as well as signal transduction. The members of GPCR and RTK family constitute largest cell surface receptor proteins and regulate physiological functions of cells in response to external and internal stimuli. Notably, GPCRs and RTKs play major role in regulation of several key cellular functions which are associated with several pathological conditions including cancer biology, neurodegenerative and cardiovascular diseases. The focus of this review is to highlight the recent findings on the possible cross-talk between somatostatin receptors (members of GPCR family) and growth factor receptors like epidermal growth factor receptors (members of RTK family). Furthermore, functional consequences of such an interaction in modulation of signaling pathways linked to pathological conditions specifically in cancer are discussed.
Collapse
Affiliation(s)
- Ujendra Kumar
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.
| |
Collapse
|