Regulation of prostate cancer by hormone-responsive G protein-coupled receptors

Nanotherapeutics for prostate cancer treatment: A comprehensive review

Prostate cancer (PCa) is the most prevalent solid organ malignancy and seriously affects male health. The adverse effects of prostate cancer therapeutics can cause secondary damage to patients. Nanotherapeutics, which have special targeting abilities and controlled therapeutic release profiles, may serve as alternative agents for PCa treatment. At present, many nanotherapeutics have been developed to treat PCa and have shown better treatment effects in animals than traditional therapeutics. Although PCa nanotherapeutics are highly attractive, few successful cases have been reported in clinical practice. To help researchers design valuable nanotherapeutics for PCa treatment and avoid useless efforts, herein, we first reviewed the strategies and challenges involved in prostate cancer treatment. Subsequently, we presented a comprehensive review of nanotherapeutics for PCa treatment, including their targeting methods, controlled release strategies, therapeutic approaches and mechanisms. Finally, we proposed the future prospects of nanotherapeutics for PCa treatment.

SNPs-Panel Polymorphism Variations in GHRL and GHSR Genes Are Not Associated with Prostate Cancer

Prostate cancer (PCa) is a major public health problem worldwide. Recent studies have suggested that ghrelin and its receptor could be involved in the susceptibility to several cancers such as PCa, leading to their use as an important predictive way for the clinical progression and prognosis of cancer. However, conflicting results of single nucleotide polymorphisms (SNPs) with ghrelin (GHRL) and its receptor (GHSR) genes were demonstrated in different studies. Thus, the present case-control study was undertaken to investigate the association of GHRL and GHSR polymorphisms with the susceptibility to sporadic PCa. A cohort of 120 PCa patients and 95 healthy subjects were enrolled in this study. Genotyping of six SNPs was performed: three tag SNPs in GHRL (rs696217, rs4684677, rs3491141) and three tag SNPs in the GHSR (rs2922126, rs572169, rs2948694) using TaqMan. The allele and genotype distribution, as well as haplotypes frequencies and linked disequilibrium (LD), were established. Multifactor dimensionality reduction (MDR) analysis was used to study gene-gene interactions between the six SNPs. Our results showed no significant association of the target polymorphisms with PCa (p > 0.05). Nevertheless, SNPs are often just markers that help identify or delimit specific genomic regions that may harbour functional variants rather than the variants causing the disease. Furthermore, we found that one GHSR rs2922126, namely the TT genotype, was significantly more frequent in PCa patients than in controls (p = 0.040). These data suggest that this genotype could be a PCa susceptibility genotype. MDR analyses revealed that the rs2922126 and rs572169 combination was the best model, with 81.08% accuracy (p = 0.0001) for predicting susceptibility to PCa. The results also showed a precision of 98.1% (p < 0.0001) and a PR-AUC of 1.00. Our findings provide new insights into the influence of GHRL and GHSR polymorphisms and significant evidence for gene-gene interactions in PCa susceptibility, and they may guide clinical decision-making to prevent overtreatment and enhance patients' quality of life.

Whole-exome sequencing of Indian prostate cancer reveals a novel therapeutic target: POLQ

PURPOSE

Prostate cancer is the second most common cancer diagnosed worldwide and the third most common cancer among men in India. This study's objective was to characterise the mutational landscape of Indian prostate cancer using whole-exome sequencing to identify population-specific polymorphisms.

METHODS

Whole-exome sequencing was performed of 58 treatment-naive primary prostate tumors of Indian origin. Multiple computational and statistical analyses were used to profile the known common mutations, other deleterious mutations, driver genes, prognostic biomarkers, and gene signatures unique to each clinical parameter. Cox analysis was performed to validate survival-associated genes. McNemar test identified genes significant to recurrence and receiver-operating characteristic (ROC) analysis was conducted to determine its accuracy. OncodriveCLUSTL algorithm was used to deduce driver genes. The druggable target identified was modeled with its known inhibitor using Autodock.

RESULTS

TP53 was the most commonly mutated gene in our cohort. Three novel deleterious variants unique to the Indian prostate cancer subtype were identified: POLQ, FTHL17, and OR8G1. COX regression analysis identified ACSM5, a mitochondrial gene responsible for survival. CYLC1 gene, which encodes for sperm head cytoskeletal protein, was identified as an unfavorable prognostic biomarker indicative of recurrence. The novel POLQ mutant, also identified as a driver gene, was evaluated as the druggable target in this study. POLQ, a DNA repair enzyme implicated in various cancer types, is overexpressed and is associated with a poor prognosis. The mutant POLQ was subjected to structural analysis and modeled with its known inhibitor novobiocin resulting in decreased binding efficiency necessitating the development of a better drug.

CONCLUSION

In this pilot study, the molecular profiling using multiple computational and statistical analyses revealed distinct polymorphisms in the Indian prostate cancer cohort. The mutational signatures identified provide a valuable resource for prognostic stratification and targeted treatment strategies for Indian prostate cancer patients. The DNA repair enzyme, POLQ, was identified as the druggable target in this study.

Transcriptomic response to GnRH down regulation by RNA interference in clam Ruditapes philippinarum, suggest possible role in reproductive function

Gonadotropin-releasing hormone (GnRH) plays a key role in the control of the reproductive axis in vertebrates, however, little is known about its function in reproductive endocrine regulation in molluscs. In the present study, RNA-seq was used to construct transcriptomes of Ruditapes philippinarum testis and ovaries of control and GnRH suppressed individuals using RNA interference. GnRH suppression caused 112 and 169 enriched KEGG pathways in testis and ovary, with 92 pathways in common in both comparisons. The most enriched KEGG pathways occurred in the "Oxidative phosphorylation", "Dorso-ventral axis formation", "Thyroid hormone synthesis" and "Oxytocin signaling pathway" etc. A total of 1838 genes in testis and 358 genes in ovaries were detected differentially expressed in GnRH suppressed clams. Among the differentially expressed genes, a suit of genes related to regulation of steroid hormones synthesis and gonadal development, were found in both ovary and testis with RNAi of GnRH. These results suggest that GnRH may play an important role in reproductive function in bivalves. This study provides a preliminary basis for studying the function and regulatory mechanism of GnRH in bivalves.

DNA-methylation and genomic copy number in primary tumors and corresponding lymph node metastases in prostate cancer from patients with low and high Gleason score

Purpose

In prostate cancer, the indication to irradiate the pelvic lymphatic pathways in clinical node-negative patients is solely based on clinical nomograms. To define biological risk patterns of lymphatic spread, we studied DNA-methylation and genomic copy number in primary tumors and corresponding lymph nodes metastases.

Methods/Patients

DNA-methylation and genomic copy number profiles of primary tumors (PT) and paired synchronous lymph node metastases (LN) from Gleason Score (GS)-6/7a (n = 20 LN-positive, n = 20 LN-negative) and GS-9/10 patients (LN-positive n = 20) after prostatectomy and lymphonodectomy were analyzed.

Results

GS-6/7a pN0 PTs and GS-6/7a pN1 PTs differed in histone H3K27me3/H3K9me3 mediated methylation. PTs compared to LNs, in both, GS-6/7a pN1 and GS-9/10 pN1 patients showed large differences in DNA-methylation mediated by histones H3K4me1/2, in addition to copy number changes of chromosomal regions 11q13.1, 14q11.2 and 15q26.1. Between GS-6/7a pN1 and GS-9/10 pN1 patients, methylation levels differed more when comparing LNs than PTs. 16q21-22.1 was specifically lost in GS-9/10 pN0 PTs. Immune system-related pathways characterized the differences between PTs and LNs in both GS-6/7a pN1 and GS-9/10 pN1 patients. Comparing PTs and LKs between GS-6/7a pN1 and GS-9/10 pN1 patients revealed altered transmembrane and G-protein-coupled receptor signaling.

Conclusions

Our data suggest that progression of prostate cancer, including lymphatic spread, is associated with histone-mediated DNA-methylation and we hypothesize a methylation signature predicting lymphatic spread in GS-6/7a patients from primary tumors. Lymphatic spread in GS-6/7a patients, flanked by DNA-methylation and CNA alterations, appears to be more complex than in GS-9/10 patients, in whom the primary tumors already appear to bear lymph node metastasis-enabling alterations.

Inhibition of signaling downstream of beta-2 adrenoceptor by propranolol in prostate cancer cells

BACKGROUND

There is accumulating evidence that propranolol, an antagonist of beta-1 and beta-2 adrenoreceptors, extends survival of patients with prostate cancer; yet it is not known whether propranolol inhibits beta-adrenergic signaling in prostate cancer cells, or systemic effects of propranolol play the leading role in slowing down cancer progression. Recently initiated clinical studies offer a possibility to test whether administration of propranolol inhibits signaling pathways in prostate tumors, however, there is limited information on the dynamics of signaling pathways activated downstream of beta-2 adrenoreceptors in prostate cancer cells and on the inactivation of these pathways upon propranolol administration.

METHODS

Western blot analysis was used to test the effects of epinephrine and propranolol on activation of protein kinase (PKA) signaling in mouse prostates and PKA, extracellular signal-regulated kinase (ERK), and protein kinase B/AKT (AKT) signaling in prostate cancer cell lines.

RESULTS

In prostate cancer cell lines epinephrine induced robust phosphorylation of PKA substrates pS133CREB and pS157VASP that was evident 2 min after treatments and lasted for 3-6 h. Epinephrine induced phosphorylation of AKT in PTEN-positive 22Rv1 cells, whereas changes of constitutive AKT phosphorylation were minimal in PTEN-negative PC3, C42, and LNCaP cells. A modest short-term increase of pERK in response to epinephrine was observed in all tested cell lines. Incubation of prostate cancer cells with 10-fold molar excess of propranolol for 30 min inhibited all downstream pathways activated by epinephrine. Subjecting mice to immobilization stress induced phosphorylation of S133CREB, whereas injection of propranolol at 1.5 mg/kg prevented the stress-induced phosphorylation.

CONCLUSIONS

The analysis of pS133CREB and pS157VASP allows measuring activation of PKA signaling downstream of beta-2 adrenoreceptors. Presented results on the ratio of propranolol/epinephrine and the time needed to inhibit signaling downstream of beta-2 adrenoreceptors will help to design clinical studies that examine the effects of propranolol on prostate tumors.

Whole-exome sequencing reveals a comprehensive germline mutation landscape and identifies twelve novel predisposition genes in Chinese prostate cancer patients

Prostate cancer is the most inheritable cancer with approximately 42% of disease risk attributed to inherited factors by studies of twins, indicating the importance of additional genetic screening to identify predisposition variants. However, only DNA damage repair (DDR) genes have been investigated thoroughly in prostate cancer. To determine the comprehensive germline mutation landscape in Chinese prostate cancer patients, we performed whole exome sequencing in 100 Han Chinese patients with prostate cancer in Hong Kong and identified deleterious germline mutations. A total of 36 deleterious germline variants in 25 genes were identified in 29% patients. Variants were found in eight pathways, including DNA methylation, DDR, and tyrosine-protein kinase. These findings were validated in an independent Chinese cohort of 167 patients with prostate cancer in Shanghai. Seven common deleterious-variant-containing genes were found in discovery cohort (7/25, 28%) and validation cohort (7/28, 25%) with three genes not described before (LDLR, MYH7 and SUGCT) and four genes previously reported (FANCI, ITGA6, PABPC1 and RAD54B). When comparing with that of a cohort of East Asian healthy individuals, 12 non-DDR novel potential predisposition genes (ADGRG1, CHD4, DNMT3A, ERBB3, GRHL1, HMBS, LDLR, MYH7, MYO6, NT5C2, NUP98 and SUGCT) were identified using the discovery and validation cohorts, which have not been previously reported in prostate cancer patients in all ethnic groups. Taken together, this study reveals a comprehensive germline mutation landscape in Chinese prostate cancer patients and discovers 12 novel non-DDR predisposition genes to lay the groundwork for the optimization of genetic screening.

Prostate cancer is the most inheritable cancer with about 42% of disease risk attributed to inherited factors, indicating the importance of additional genetic screening to identify predisposition variants. However, only DNA damage repair (DDR) genes have been studied thoroughly in prostate cancer. To determine the comprehensive germline mutation landscape in Chinese prostate cancer patients, we performed whole exome sequencing in 100 Han Chinese patients with prostate cancer in Hong Kong and identified deleterious germline mutations. A total of 36 deleterious germline variants in 25 genes were identified in 29% patients. Variants were found in eight pathways, including DNA methylation, DDR, and tyrosine-protein kinase. These findings were validated in an independent Chinese cohort of 167 patients with prostate cancer in Shanghai. Seven common deleterious-variant-containing genes were found in discovery cohort and validation cohort with three genes not described before (LDLR, MYH7 and SUGCT) and four genes previously reported. When comparing with that of a cohort of East Asian healthy individuals, 12 non-DDR novel potential predisposition genes were identified using the discovery and validation cohorts, which have not been previously reported in prostate cancer patients in all ethnic groups.

Overview of human 20 alpha-hydroxysteroid dehydrogenase (AKR1C1): Functions, regulation, and structural insights of inhibitors

Human aldo-keto reductase family 1C1 (AKR1C1) is an important enzyme involved in human hormone metabolism, which is mainly responsible for the metabolism of progesterone in the human body. AKR1C1 is highly expressed and has an important relationship with the occurrence and development of various diseases, especially some cancers related to hormone metabolism. Nowadays, many inhibitors against AKR1C1 have been discovered, including some synthetic compounds and natural products, which have certain inhibitory activity against AKR1C1 at the target level. Here we briefly reviewed the physiological and pathological functions of AKR1C1 and the relationship with the disease, and then summarized the development of AKR1C1 inhibitors, elucidated the interaction between inhibitors and AKR1C1 through molecular docking results and existing co-crystal structures. Finally, we discussed the design ideals of selective AKR1C1 inhibitors from the perspective of AKR1C1 structure, discussed the prospects of AKR1C1 in the treatment of human diseases in terms of biomarkers, pre-receptor regulation and single nucleotide polymorphisms, aiming to provide new ideas for drug research targeting AKR1C1.

Orexins/Hypocretins and Cancer: A Neuropeptide as Emerging Target

Over 20 years ago, orexin neuropeptides (Orexin-A/hypocretin-1 and Orexin-B/hypocretins-2) produced from the same precursor in hypothalamus were identified. These two neurotransmitters and their receptors (OX1R and OX1R), present in the central and peripheral nervous system, play a major role in wakefulness but also in drug addiction, food consumption, homeostasis, hormone secretion, reproductive function, lipolysis and blood pressure regulation. With respect to these biological functions, orexins were involved in various pathologies encompassing narcolepsy, neurodegenerative diseases, chronic inflammations, metabolic syndrome and cancers. The expression of OX1R in various cancers including colon, pancreas and prostate cancers associated with its ability to induce a proapoptotic activity in tumor cells, suggested that the orexins/OX1R system could have a promising therapeutic role. The present review summarizes the relationship between cancers and orexins/OX1R system as an emerging target.

A Review of the Pathophysiological Mechanisms Underlying Castration-resistant Prostate Cancer

Androgen deprivation therapy or ADT is one of the cornerstones of management of locally advanced or metastatic prostate cancer, alongside radiation therapy. However, despite early response, most advanced prostate cancers progress into an androgen unresponsive or castrate resistant state, which hitherto remains an incurable entity and the second leading cause of cancer-related mortality in men in the US. Recent advances have uncovered multiple complex and intermingled mechanisms underlying this transformation. While most of these mechanisms revolve around androgen receptor (AR) signaling, novel pathways which act independently of the androgen axis are also being discovered. The aim of this article is to review the pathophysiological mechanisms that help bypass the apoptotic effects of ADT to create castrate resistance. The article discusses castrate resistance mechanisms under two categories: 1. Direct AR dependent pathways such as amplification or gain of function mutations in AR, development of functional splice variants, posttranslational regulation, and pro-oncogenic modulation in the expression of coactivators vs corepressors of AR. 2. Ancillary pathways involving RAS/MAP kinase, TGF-beta/SMAD pathway, FGF signaling, JAK/STAT pathway, Wnt-Beta catenin and hedgehog signaling as well as the role of cell adhesion molecules and G-protein coupled receptors. miRNAs are also briefly discussed. Understanding the mechanisms involved in the development and progression of castration-resistant prostate cancer is paramount to the development of targeted agents to overcome these mechanisms. A number of targeted agents are currently in development. As we strive for more personalized treatment across oncology care, treatment regimens will need to be tailored based on the type of CRPC and the underlying mechanism of castration resistance.

A Decade's Progress in the Development of Molecular Imaging Agents Targeting the Growth Hormone Secretagogue Receptor

The growth hormone secretagogue receptor 1a (GHSR), also called the ghrelin receptor, is a G protein-coupled receptor known to play an important metabolic role in the regulation of various physiological processes, including energy expenditure, growth hormone secretion, and cell proliferation. This receptor has been implicated in numerous health issues including obesity, gastrointestinal disorders, type II diabetes, and regulation of body weight in patients with Prader-Willi syndrome, and there has been growing interest in studying its mechanism of behavior to unlock further applications of GHSR-targeted therapeutics. In addition, the GHSR is expressed in various types of cancer including prostate, breast, and testicular cancers, while aberrant expression has been reported in cardiac disease. Targeted molecular imaging of the GHSR could provide insights into its role in biological processes related to these disease states. Over the past decade, imaging probes targeting this receptor have been discovered for the imaging modalities PET, SPECT, and optical imaging. High-affinity analogues of ghrelin, the endogenous ligand for the GHSR, as well as small molecule inhibitors have been developed and evaluated both in vitro and in pre-clinical models. This review provides a comprehensive overview of the molecular imaging agents targeting the GHSR reported to the end of 2019.

Targeting CPT1B as a potential therapeutic strategy in castration-resistant and enzalutamide-resistant prostate cancer

BACKGROUND

Prostate cancer is characterized by aberrant lipid metabolism, including elevated fatty acid oxidation. Carnitine palmitoyltransferase 1B (CPT1B) catalyzes the rate-limiting step of fatty acid oxidation. This study aimed to determine if CPT1B has a critical role in prostate cancer progression and to identify its regulatory mechanism.

METHODS

CPT1B expression data from The Cancer Genome Atlas and Gene Expression Omnibus databases was compared with patient survival data. A tissue microarray was constructed with 60 samples of prostate cancer and immunohistochemically stained for CPT1B. Castration-resistant prostate cancer (CRPC) cell lines 22RV1 and C4-2 in which CPT1B expression had been stably knocked down were established; and cell proliferation, cell cycle distribution, and invasion were investigated by Cell Counting Kit-8 (CCK-8) and colony formation assays, flow cytometry, and Transwell assays, respectively. To examine the impact of androgen receptor (AR) inhibition on CPT1B expression, JASPAR CORE was searched to identify AR-binding sites in CPT1B. Dual luciferase and ChIP assays were performed to confirm CPT1B activity and AR binding, respectively. Differentially expressed genes (DEGs) in prostate cancer underwent gene set enrichment analysis (GSEA). Enzalutamide-resistant C4-2 cells were generated and the mechanism of enzalutamide resistance and downstream signaling pathway changes of CPT1B to C4-2 was explored through CCK-8 test.

RESULTS

CPT1B expression was upregulated in human prostate cancer compared with normal prostate tissue and was associated with poor disease-free survival and overall survival. Silencing of CPT1B resulted in downregulated cell proliferation, reduced S-phase distribution, and lower invasive ability, whereas the opposite was observed in CRPC cells overexpressing CPTB1. DEGS in prostate cancer were correlated with G-protein-coupled receptor signaling, molecular transducer activity, and calcium ion binding. AR may regulate CPT1B expression and activity via specific binding sites, as confirmed by dual luciferase and ChIP assays. The CCK-8 experiment demonstrated that CPT1B overexpression in C4-2 cells did not significantly increase the ability of enzalutamide resistance. However, overexpression of CPT1B in C4-2R cells significantly increased the enzalutamide resistance. Upregulation of CPT1B expression increased AKT expression and phosphorylation.

CONCLUSIONS

CPT1B is upregulated in prostate cancer and is correlated with poor prognosis, indicating its potential as a biomarker. AR inhibits the transcription of CPT1B. In the CRPC cell line, overexpression of CPT1B alone cannot promote enzalutamide resistance, but in the drug-resistant line C4-2R, overexpression of CPT1B can promote the resistance of C4-2R to enzalutamide.

Molecular chaperones and G protein-coupled receptor maturation and pharmacology

G protein-coupled receptors (GPCRs) are highly conserved versatile signaling molecules located at the plasma membrane that respond to diverse extracellular signals. They regulate almost all physiological processes in the vertebrates. About 35% of current drugs target these receptors. Mutations in these genes have been identified as causes of numerous diseases. The seven transmembrane domain structure of GPCRs implies that the folding of these transmembrane proteins is extremely complicated and difficult. Indeed, many wild type GPCRs are not folded optimally. The most common defect in genetic diseases caused by GPCR mutations is misfolding and failure to reach the plasma membrane where it functions. General molecular chaperones aid the folding of all proteins, including GPCRs, by preventing aggregation, promoting folding and disaggregating small aggregates. Some GPCRs need additional receptor-specific chaperones to assist their folding. Many of these receptor-specific chaperones interact with additional receptors and alter receptor pharmacology, expanding the understanding of these chaperone proteins.

Overview of AKR1C3: Inhibitor Achievements and Disease Insights

Human aldo-keto reductase family 1 member C3 (AKR1C3) is known as a hormone activity regulator and prostaglandin F (PGF) synthase that regulates the occupancy of hormone receptors and cell proliferation. Because of the overexpression in metabolic diseases and various hormone-dependent and -independent carcinomas, as well as the emergence of clinical drug resistance, an increasing number of studies have investigated AKR1C3 inhibitors. Here, we briefly review the physiological and pathological function of AKR1C3 and then summarize the recent development of selective AKR1C3 inhibitors. We propose our viewpoints on the current problems associated with AKR1C3 inhibitors with the aim of providing a reference for future drug discovery and potential therapeutic perspectives on novel, potent, selective AKR1C3 inhibitors.

Identification of FOS as a Candidate Risk Gene for Liver Cancer by Integrated Bioinformatic Analysis

Liver cancer is a lethal disease that is associated with poor prognosis. In order to identify the functionally important genes associated with liver cancer that may reveal novel therapeutic avenues, we performed integrated analysis to profile miRNA and mRNA expression levels for liver tumors compared to normal samples in The Cancer Genome Atlas (TCGA) database. We identified 405 differentially expressed genes and 233 differentially expressed miRNAs in tumor samples compared with controls. In addition, we also performed the pathway analysis and found that mitogen-activated protein kinases (MAPKs) and G-protein coupled receptor (GPCR) pathway were two of the top significant pathway nodes dysregulated in liver cancer. Furthermore, by examining these signaling networks, we discovered that FOS (Fos proto-oncogene, AP-1 transcription factor subunit), LAMC2 (laminin subunit gamma 2), and CALML3 (calmodulin like 3) were the most significant gene nodes with high degrees involved in liver cancer. The expression and disease prediction accuracy of FOS, LAMC2, CALML3, and their interacting miRNAs were further performed using a HCC cohort. Finally, we investigated the prognostic significance of FOS in another HCC cohort. Patients with higher FOS expression displayed significantly shorter time to recurrence (TTR) and overall survival (OS) compared with patients with lower expression. Collectively, our study demonstrates that FOS is a potential prognostic marker for liver cancer that may reveal a novel therapeutic avenue in this lethal disease.

Atypical chemokine receptors in tumor cell growth and metastasis

Atypical chemokine receptors (ACKRs) are seven-transmembrane cell surface protein receptors expressed in immune cells, normal mesenchymal cells, and several tumor cells. As of this writing, six ACKRs have been characterized by diverse activities. They bind both cysteine-cysteine (CC) type and cysteine-X-cysteine (CXC)-type chemokines, either alone, or together with a ligand bound-functional G-protein coupled (typical) chemokine receptor. The major structural difference between ACKRs and typical chemokine receptors is the substituted DRYLAIV amino acid motif in the second intracellular loop of the ACKR. Due to this substitution, these receptors cannot bind Gαi-type G-proteins responsible for intracellular calcium mobilization and cellular chemotaxis. Although initially characterized as non-signaling transmembrane receptors (decoy receptors) that attenuate ligand-induced signaling by GPCRs, studies of all ACKRs have shown ligand-independent and ligand-dependent transmembrane signaling in both non-tumor and tumor cells. The precise function and mechanism of the differential expression of ACKRs in many tumors are not understood well. The use of antagonists of ACKRs ligands has shown limited antitumor potential; however, depleting ACKR expression resulted in a reduction in experimental tumor growth and metastasis. The ACKRs represent a unique class of transmembrane signaling proteins that regulate growth, survival, and metastatic processes in tumor cells, affecting multiple pathways of tumor growth. Therefore, closer investigations of ACKRs have a high potential for identifying therapeutics which affect the intracellular signaling, preferentially via the ligand-independent mechanism.

Attribution of Ghrelin to Cancer; Attempts to Unravel an Apparent Controversy

Ghrelin is an endogenous peptide hormone mainly produced in the stomach. It has been known to regulate energy homeostasis, stimulate secretion of growth hormone, and mediate many other physiologic effects. Various effects attributed to ghrelin contribute to many aspects of cancer development and progression. Accordingly, a large body of evidence has emerged about the association of ghrelin with several types of cancer in scales of cell-line, animal, and human studies. However, existing data are controversial. This controversy occurs in two main domains: one is the controversial results in local effects of ghrelin on different types of human cancer cell-lines; the second is the apparent disagreement in the results of in-vitro and clinical studies that investigated ghrelin association to one type of cancer. These inconsistencies have hampered the indications to consider ghrelin as a potential tumor biomarker or therapeutic agent in cancer patients. Previous studies have reviewed different parts of current literature about the ghrelin-cancer relationship. Although they have highlighted these controversial results in various ways, no specific recommendations have been given to address it. In this study, we comprehensively reviewed in-vitro, in-vivo, and clinical studies and attempted to use the following approaches to unravel the inconsistencies detected: (a) to distinguish local and systemic effects of ghrelin in interpreting its summary clinical role in each cancer; (b) scrutinizing factors that regulate local effects of ghrelin and could justify different effects of ghrelin on different cancer cell-lines. These approaches could have notable implications for future in-vitro and clinical studies.

The Anti-tumoral Properties of Orexin/Hypocretin Hypothalamic Neuropeptides: An Unexpected Therapeutic Role

Orexins (OxA and OxB) also termed hypocretins are hypothalamic neuropeptides involved in central nervous system (CNS) to control the sleep/wake process which is mediated by two G protein-coupled receptor subtypes, OX1R, and OX2R. Beside these central effects, orexins also play a role in various peripheral organs such as the intestine, pancreas, adrenal glands, kidney, adipose tissue and reproductive tract.In the past few years, an unexpected anti-tumoral role of orexins mediated by a new signaling pathway involving the presence of two immunoreceptor tyrosine-based inhibitory motifs (ITIM) in both orexin receptors subtypes, the recruitment of the phosphotyrosine phosphatase SHP2 and the induction of mitochondrial apoptosis has been elucidated. In the present review, we will discuss the anti-tumoral effect of orexin/OXR system in colon, pancreas, prostate and other cancers, and its interest as a possible therapeutic target.