Adrenomedullin prevents apoptosis in prostate cancer cells

The Role of Cytokines in Activation of Tumour-promoting Pathways and Emergence of Cancer Drug Resistance

Scientists are constantly researching and launching potential chemotherapeutic agents as an irreplaceable weapon to fight the battle against cancer. Despite remarkable advancement over the past several decades to wipe out cancer through early diagnosis, proper prevention, and timely treatment, cancer is not ready to give up and leave the battleground. It continuously tries to find some other way to give a tough fight for its survival, either by escaping from the effect of chemotherapeutic drugs or utilising its own chemical messengers like cytokines to ensure resistance. Cytokines play a significant role in cancer cell growth and progression, and the present article highlights their substantial contribution to mechanisms of resistance toward therapeutic drugs. Multiple clinical studies have even described the importance of specific cytokines released from cancer cells as well as stromal cells in conferring resistance. Herein, we discuss the different mechanism behind drug resistance and the crosstalk between tumor development and cytokines release and their contribution to showing resistance towards chemotherapeutics. As a part of this review, different approaches to cytokines profile have been identified and employed to successfully target new evolving mechanisms of resistance and their possible treatment options.

Targeting Adrenomedullin in Oncology: A Feasible Strategy With Potential as Much More Than an Alternative Anti-Angiogenic Therapy

The development, maintenance and metastasis of solid tumors are highly dependent on the formation of blood and lymphatic vessels from pre-existing ones through a series of processes that are respectively known as angiogenesis and lymphangiogenesis. Both are mediated by specific growth-stimulating molecules, such as the vascular endothelial growth factor (VEGF) and adrenomedullin (AM), secreted by diverse cell types which involve not only the cancerogenic ones, but also those constituting the tumor stroma (i.e., macrophages, pericytes, fibroblasts, and endothelial cells). In this sense, anti-angiogenic therapy represents a clinically-validated strategy in oncology. Current therapeutic approaches are mainly based on VEGF-targeting agents, which, unfortunately, are usually limited by toxicity and/or tumor-acquired resistance. AM is a ubiquitous peptide hormone mainly secreted in the endothelium with an important involvement in blood vessel development and cardiovascular homeostasis. In this review, we will introduce the state-of-the-art in terms of AM physiology, while putting a special focus on its pro-tumorigenic role, and discuss its potential as a therapeutic target in oncology. A large amount of research has evidenced AM overexpression in a vast majority of solid tumors and a correlation between AM levels and disease stage, progression and/or vascular density has been observed. The analysis presented here indicates that the involvement of AM in the pathogenesis of cancer arises from: 1) direct promotion of cell proliferation and survival; 2) increased vascularization and the subsequent supply of nutrients and oxygen to the tumor; 3) and/or alteration of the cell phenotype into a more aggressive one. Furthermore, we have performed a deep scrutiny of the pathophysiological prominence of each of the AM receptors (AM₁ and AM₂) in different cancers, highlighting their differential locations and functions, as well as regulatory mechanisms. From the therapeutic point of view, we summarize here an exhaustive series of preclinical studies showing a reduction of tumor angiogenesis, metastasis and growth following treatment with AM-neutralizing antibodies, AM receptor antagonists, or AM receptor interference. Anti-AM therapy is a promising strategy to be explored in oncology, not only as an anti-angiogenic alternative in the context of acquired resistance to VEGF treatment, but also as a potential anti-metastatic approach.

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.

Growth factors mediated cell signalling in prostate cancer progression: Implications in discovery of anti-prostate cancer agents

Cancer is one of the leading causes of mortality amongst world's population, in which prostate cancer is one of the most encountered malignancies among men. Globally, it is the sixth leading cause of cancer-related death in men. Prostate cancer is more prevalent in the developed world and is increasing at alarming rates in the developing countries. Prostate cancer is mostly a very sluggish progressing disease, caused by the overproduction of steroidal hormones like dihydrotestosterone or due to over-expression of enzymes such as 5-α-reductase. Various studies have revealed that growth factors play a crucial role in the progression of prostate cancer as they act either by directly elevating the level of steroidal hormones or upregulating enzyme efficacy by the active feedback mechanism. Presently, treatment options for prostate cancer include radiotherapy, surgery and chemotherapy. If treatment is done with prevailing traditional chemotherapy; it leads to resistance and development of androgen-independent prostate cancer that further complicates the situation with no cure option left. The current review article is an attempt to cover and establish an understanding of some major signalling pathways intervened through survival factors (IGF-1R), growth factors (TGF-α, EGF), Wnt, Hedgehog, interleukin, cytokinins and death factor receptor which are frequently dysregulated in prostate cancer. This will enable the researchers to design and develop better therapeutic strategies targeting growth factors and their cross talks mediated prostate cancer cell signalling.

Hypoxia-induced apoptosis is blocked by adrenomedullin via upregulation of Bcl-2 in human osteosarcoma cells

Adrenomedullin (ADM), a multifunctional regulatory peptide, is potentially induced by hypoxia in physiological and pathological tissues, including many types of malignant tumors. Recent research has demonstrated that ADM expression is highly associated with the prognosis and disease severity of human osteosarcoma. However, the effect of ADM on the apoptosis of osteosarcoma cells and its possible mechanism remain to be elucidated. In the present study, we observed that mRNA and protein levels of ADM were increased in human osteosarcoma SOSP-F5M2 cells under a hypoxic microenvironment induced by cobalt chloride (CoCl2) in a time-dependent manner. Treatment with ADM significantly blunted hypoxic-induced apoptosis, evaluated by Hoechst 33342 staining and Annexin V-FITC/PI labeling. The expression of B-cell lymphoma-2 (Bcl-2) was increased by administration of ADM; meanwhile, this effect was reversed by exogenously adding U0126, a selective inhibitor of MEK or ADM22-52 (ADM-specific receptor antagonist). These results demonstrated that ADM acted as a survival factor to inhibit hypoxic-induced apoptosis via interacting with its receptors CRLR-RAMP (2,3) in osteosarcoma cells. The anti-apoptotic function of ADM was found to be mediated by upregulation of the expression of Bcl-2 partially through activation of the MEK/ERK1/2 signaling pathway. Therefore, targeting of the ADM/ADM acceptors/ERK1/2/Bcl-2 pathway may provide a potential strategy through which to induce the apoptosis of osteosarcoma cells.

Adrenomedullin and tumour microenvironment

Adrenomedullin (AM) is a regulatory peptide whose involvement in tumour progression is becoming more relevant with recent studies. AM is produced and secreted by the tumour cells but also by numerous stromal cells including macrophages, mast cells, endothelial cells, and vascular smooth muscle cells. Most cancer patients present high levels of circulating AM and in some cases these higher levels correlate with a worst prognosis. In some cases it has been shown that the high AM levels return to normal following surgical removal of the tumour, thus indicating the tumour as the source of this excessive production of AM. Expression of this peptide is a good investment for the tumour cell since AM acts as an autocrine/paracrine growth factor, prevents apoptosis-mediated cell death, increases tumour cell motility and metastasis, induces angiogenesis, and blocks immunosurveillance by inhibiting the immune system. In addition, AM expression gets rapidly activated by hypoxia through a HIF-1α mediated mechanism, thus characterizing AM as a major survival factor for tumour cells. Accordingly, a number of studies have shown that inhibition of this peptide or its receptors results in a significant reduction in tumour progression. In conclusion, AM is a great target for drug development and new drugs interfering with this system are being developed.

The orexin type 1 receptor is overexpressed in advanced prostate cancer with a neuroendocrine differentiation, and mediates apoptosis

AIM

In the present study, we have examined the presence of orexins and their receptors in prostate cancer (CaP) and investigated their effects on the apoptosis of prostate cancer cells.

METHODS

We have localised the orexin type 1 and 2 receptors (OX1R and OX2R) and orexin A (OxA) in CaP sections of various grades and we have quantified tumour cells containing OX1R. Expression of OX1R was evaluated in the androgeno-dependent (AD) LNCaP and the androgeno-independent (AI) DU145 prostate cancer cells submitted or not to a neuroendocrine differentiation. The effects of orexins on the apoptosis and viability of DU145 cells were also investigated.

RESULTS

OX1R is strongly expressed in carcinomatous foci exhibiting a neuroendocrine differentiation, and the number of OX1R-stained cancer cells increases with the grade of the CaP. In contrast, OX2R is only detected in scattered malignant cells in high grade CaP. OX1R is expressed in the AI DU145 cells but is undetectable in the LNCaP cells. Acquisition of a neuroendocrine phenotype by the DU145 cells is associated with an overexpression of OX1R. Orexins induce the apoptosis of DU145 cells submitted to a neuroendocrine differentiation.

CONCLUSION

The present data indicate that OX1R-driven apoptosis is overexpressed in AI CaP exhibiting a neuroendocrine differentiation opening a gate for novel therapies for these aggressive cancers which are incurable until now.

Novel biological effects of alloferon and its selected analogues: structure-activity study

The subject of this paper is a search for new biological properties of alloferon (H-His-Gly-Val-Ser-Gly-His-Gly-Gln-His-Gly-Val-His-Gly-OH) and a series of its analogues. The studies on structure/activity relationship in alloferon, the synthesis of a series of 28 analogues were performed. The analogues were modified at position 1 or 6, and other were oligopeptides with a shortened peptide sequence. Biological effects of the peptides were evaluated by the pro-apoptotic action in vivo on haemocytes of Tenebrio molitor and in the cardiotropic test in vitro on the heart of T. molitor and Zophobas atratus. In the in vivo bioassays, new biological activities of alloferon and its analogues were discovered. In haemocytotoxic bioassay, alloferon strongly induces T. molitor haemocytes to undergo apoptosis at a dose of 10 nM. Moreover, [Phe(p-NH2)(1)]-, [Tyr(6)]- and [1-10]-alloferon exhibit a two-fold increase of caspases activation in comparison with the alloferon. However, alloferon and its analogues show a weak cardiostimulatory activity in Z. atratus but the heart of T. molitor is not sensitive to these peptides. The results obtained here suggest that alloferon plays pleiotropic functions in insects.

Adrenomedullin expression in epithelial ovarian cancers and promotes HO8910 cell migration associated with upregulating integrin α5β1 and phosphorylating FAK and paxillin

Background

Epithelial ovarian cancer (EOC) is one of the leading causes of cancer deaths in women worldwide. Adrenomedullin (AM) is a multifunctional peptide which presents in various kinds of tumors.

Methods

In this study, we characterized the expression and function of AM in epithelial ovarian cancer using immunohistochemistry staining. Exogenous AM and small interfering RNA (siRNA) specific for AM receptor CRLR were treated to EOC cell line HO8910. Wound healing assay and flow cytometry were used to measure the migration ability and expression of integrin α5 of HO8910 cells after above treatments. Western blot was used to examine the phosphorylation of FAK and paxillin.

Results

We found that patients with high AM expression showed a higher incidence of metastasis, larger residual size of tumors after cytoreduction and shorter disease-free and overall survival time. Exogenous AM induced ovarian cancer cell migration in time- and dose- dependent manners. AM upregulated the expression of integrin α5 and phosphorylation of FAK, paxillin as well.

Conclusions

Our results suggested that AM contributed to the progression of EOC and had additional roles in EOC cell migration by activating the integrin α5β1 signaling pathway. Therefore, we presumed that AM could be a potential molecular therapeutic target for ovarian carcinoma.

Adrenomedullin production is increased in colorectal adenocarcinomas; its relation to matrix metalloproteinase-9

Adrenomedullin (AM) is highly expressed in various cancer cell lines, suggesting a possible association with cancer growth. In the present study, we examined the expression and/or concentration of AM, its related peptide, adrenomedullin2/intermedin (AM2/IMD) and their receptors in human colorectal cancer and the surrounding normal tissue. In addition, we assessed the correlation between the expression of AM and AM2/IMD with that of vascular endothelial growth factor (VEGF)-A and matrix metalloproteinase (MMP)-9. Using a specific immunoradiometric assay, we found that AM concentrations were 2-11-fold higher in colorectal cancer tissues than in the surrounding normal tissues. Moreover, real-time quantitative RT-PCR showed that the expression levels of preproAM (+548%), preproAM2/IMD (+2674%), calcitonin receptor-like receptor (CLR) (+518%), receptor activity modifying protein (RAMP)2 (+281%), RAMP3 (+178%), VEGF-A (+277%) and MMP-9 (+864%) mRNAs were significantly higher in cancer tissues than in the surrounding normal tissues, and there was a positive correlation between the gene expressions of MMP-9 and preproAM (r=0.352; p=0.005), but not with preproAM2/IMD (r=0.041, p=0.406). Both AM and AM2/IMD immunoreactivity were detected mainly within cancer cells, whereas MMP-9 immunoreactivity was mostly seen in the surrounding stroma. These findings suggest that AM produced in colorectal tumors acts in concert with MMP-9 in the stroma to contribute to the pathogenesis of colorectal cancer.

Role of different inflammatory and tumor biomarkers in the development of ulcerative colitis-associated carcinogenesis

BACKGROUND

Colorectal cancer (CRC) is the most severe complication in inflammatory bowel disease (IBD). In the present study we investigated different mechanistic links between chronic colonic inflammation and its progression to adenocarcinoma. Along these lines, given that adrenomedullin (AM) has been implicated in carcinogenesis, we also analyzed changes in its colonic expression.

METHODS

Mice were exposed to 5, 10, and 15 cycles of dextran sulfate sodium (DSS); each cycle consisted of 0.7% DSS for 1 week followed by distilled water for 10 days. After each period, macroscopic and histological studies, as well as characterization of inflammatory and tumor biomarkers, were carried out.

RESULTS

The disease activity index (DAI) showed that the disease was present from the third cycle and it gradually increased during the course of DSS treatment. Macroscopic tumors were only seen after 15 cycles, and microscopic study showed that inflammation, dysplasia, and adenocarcinomas correlated with DSS cycles. β-Catenin and proliferating cell nuclear antigen expressions progressively increased in animals treated with the different cycles of DSS. TNF-α and IFN-γ showed the highest production at the tenth cycle. COX-2, mPGES-1, and iNOS levels were also appreciably higher at the fifth and tenth cycles. Moreover, we observed a progressive enhancement in AM expression and changes in its intracellular location during the progression of the disease.

CONCLUSIONS

Our results show an early induction of proinflammatory factors, which may contribute to the development of colon cancer, as well as demonstrate, for the first time, the expression of AM in IBD-derived CRC.

Adrenomedullin promotes cell cycle transit and up-regulates cyclin D1 protein level in human glioblastoma cells through the activation of c-Jun/JNK/AP-1 signal transduction pathway

Adrenomedullin is a secreted peptide hormone with multiple functions. Although a number of reports have indicated that adrenomedullin may be involved in tumor progression, its mechanism of action remains obscure. In this study, we have analysed the signal transduction pathway activated by adrenomedullin in human glioma cells. Our results revealed that adrenomedullin induced the phosphorylation of both c-Jun and JNK in glioblastoma cells. Silencing JNK expression with siRNA reversed the phosphorylation of c-Jun induced by adrenomedullin, indicating that JNK is responsible of c-Jun activation. In addition, electrophoretic mobility-shift assays showed that the increase in phosphorylation of c-Jun was associated with increased AP-1 DNA binding activity. Supershift assays and co-immunoprecipitation demonstrated that c-Jun and JunD are part of the AP-1 complex, indicating that activated c-Jun is dimerized with JunD in response to adrenomedullin. Furthermore, adrenomedullin was shown to promote cell transit beyond cell cycle phases with a concomittant increase in cyclin D1 protein level, suggesting that adrenomedullin effects cell proliferation through up-regulation of cyclin D1. The inhibition of JNK activation or the suppression of c-Jun or JunD expression with siRNA impaired the effects of adrenomedullin on cell proliferation and on cyclin D1. Taken together, these data demonstrate that activation of cJun/JNK pathway is involved in the growth regulatory activity of adrenomedullin in glioblastoma cells.

Nonclassic Endogenous Novel Regulators of Angiogenesis

Angiogenesis, the process through which new blood vessels arise from preexisting ones, is regulated by several "classic" factors, among which the most studied are vascular endothelial growth factor (VEGF) and fibroblast growth factor-2 (FGF-2). In recent years, investigations showed that, in addition to the classic factors, numerous endogenous peptides play a relevant regulatory role in angiogenesis. Such regulatory peptides, each of which exerts well-known specific biological activities, are present, along with their receptors, in the blood vessels and may take part in the control of the "angiogenic switch." An in vivo and in vitro proangiogenic effect has been demonstrated for erythropoietin, angiotensin II (ANG-II), endothelins (ETs), adrenomedullin (AM), proadrenomedullin N-terminal 20 peptide (PAMP), urotensin-II, leptin, adiponectin, resistin, neuropeptide-Y, vasoactive intestinal peptide (VIP), pituitary adenylate cyclase-activating polypeptide (PACAP), and substance P. There is evidence that the angiogenic action of some of these peptides is at least partly mediated by their stimulating effect on VEGF (ANG-II, ETs, PAMP, resistin, VIP and PACAP) and/or FGF-2 systems (PAMP and leptin). AM raises the expression of VEGF in endothelial cells, but VEGF blockade does not affect the proangiogenic action of AM. Other endogenous peptides have been reported to exert an in vivo and in vitro antiangiogenic action. These include somatostatin and natriuretic peptides, which suppress the VEGF system, and ghrelin, that antagonizes FGF-2 effects. Investigations on "nonclassic" regulators of angiogenesis could open new perspectives in the therapy of diseases coupled to dysregulation of angiogenesis.

Methylseleninic acid enhances the effect of etoposide to inhibit prostate cancer growthin vivo

New therapeutic agents are needed for the treatment of androgen-independent prostate cancer (PrCa). We have investigated the effect of methylseleninic acid (MSA) on tumor stage-specific prostate cells derived from the C3 (1)/Tag model for PrCa: Pr111, a slow-growing and nontumorigenic cell line isolated from a prostate intraepithelial neoplasia lesion; Pr14, a tumorigenic line derived from a primary tumor; and Pr14C1, a sub-clone of Pr14 explanted from a lung metastasis. We demonstrate that MSA strongly inhibits cell growth and induces apoptosis in C3 (1)/Tag tumor cells, in a dose-dependent manner. A decrease in phosphorylated ERK1/2 and AKT was also found in tumor cells, but not in Pr111. Microarray analysis using affymetrix showed that the number of genes with an altered expression in tumor cells is significantly higher (p < 0.01) than in nontumoral cells. Pathways analyses revealed a decrease in the expression of genes involved in metabolism (Fabp5, Cyba), signal transduction (ERK, AKT), angiogenesis (neuropilin-1, Flt-4) and transcription (cAMP response element-binding protein) in tumor cells. The expression of neuropilin-1, a protein involved in VEGF signaling and tumor angiogenesis, was 97-fold repressed in Pr14 cells treated with MSA. Combination treatments using low doses of etoposide or taxotere (docetaxel), plus low doses of MSA revealed a strong enhancement of cell growth inhibition and apoptosis in tumor cells. Our in vivo studies using Pr14 cells xenografted into nude mice demonstrated that MSA significantly enhances the chemotherapeutical effect of etoposide, resulting in 78.3% tumor growth inhibition. These results suggest that MSA could be used against PrCa to enhance the effect of etoposide.

Adrenomedullin: a new and promising target for drug discovery

Adrenomedullin (AM) is a 52 amino acid peptide that plays a critical role in several diseases such as hypertension, cancer, diabetes, cardiovascular and renal disorders, among others. Interestingly, AM behaves as a protective agent against some pathologies, yet is a stimulating factor for other disorders. Thus, AM can be considered as a new and promising target for the design of non-peptidic modulators that could be useful for the treatment of those pathologies, by regulating AM levels or the activity of AM. A full decade on from its discovery, much more is known about AM molecular biology and pharmacology, but this knowledge still needs to be applied to the development of clinically useful drugs.