BRADYKININ INDUCED MITOGENESIS OF ANDROGEN INDEPENDENT PROSTATE CANCER CELLS

GPCR-Gα13 Involvement in Mitochondrial Function, Oxidative Stress, and Prostate Cancer

Gα13 and Gα12, encoded by the GNA13 and GNA12 genes, respectively, are members of the G12 family of Gα proteins that, along with their associated Gβγ subunits, mediate signaling from specific G protein-coupled receptors (GPCRs). Advanced prostate cancers have increased expression of GPCRs such as CXC Motif Chemokine Receptor 4 (CXCR4), lysophosphatidic acid receptor (LPAR), and protease activated receptor 1 (PAR-1). These GPCRs signal through either the G12 family, or through Gα13 exclusively, often in addition to other G proteins. The effect of Gα13 can be distinct from that of Gα12, and the role of Gα13 in prostate cancer initiation and progression is largely unexplored. The oncogenic effect of Gα13 on cell migration and invasion in prostate cancer has been characterized, but little is known about other biological processes such as mitochondrial function and oxidative stress. Current knowledge on the link between Gα13 and oxidative stress is based on animal studies in which GPCR-Gα13 signaling decreased superoxide levels, and the overexpression of constitutively active Gα13 promoted antioxidant gene activation. In human samples, mitochondrial superoxide dismutase 2 (SOD2) correlates with prostate cancer risk and prognostic Gleason grade. However, overexpression of SOD2 in prostate cancer cells yielded conflicting results on cell growth and survival under basal versus oxidative stress conditions. Hence, it is necessary to explore the effect of Gα13 on prostate cancer tumorigenesis, as well as the effect of Gα13 on SOD2 in prostate cancer cell growth under oxidative stress conditions.

Bradykinin B1 Receptor Affects Tumor-Associated Macrophage Activity and Glioblastoma Progression

Bradykinin is a small active peptide and is considered an inflammatory mediator in several pathological conditions. Bradykinin exerts its effects by coupling to its receptors, including bradykinin B1 (B1R) and bradykinin B2. B1R has been implicated in the development of various cancers. Our previous study reported that B1R promoted glioblastoma (GBM) development by supporting the migration and invasion of GBM cells. However, the mechanisms underlying the effects of B1R on tumor-associated macrophages (TAMs) and GBM progression remain unknown. Accordingly, to explore the regulatory effects of B1R overexpression (OE) in GBM on tumor-associated immune cells and tumor progression, we constructed a B1R wild-type plasmid and developed a B1R OE model. The results reveal that B1R OE in GBM promoted the expression of ICAM-1 and VCAM-1-cell adhesion molecules-in GBM. Moreover, B1R OE enhanced GBM cell migration ability and monocyte attachment. B1R also regulated the production of the protumorigenic cytokines and chemokines IL-6, IL-8, CXCL11, and CCL5 in GBM, which contributed to tumor progression. We additionally noted that B1R OE in GBM increased the expression of CD68 in TAMs. Furthermore, B1R OE reduced the level of reactive oxygen species in GBM cells by upregulating heme oxygenase-1, an endogenous antioxidant protein, thereby protecting GBM cells from oxidative stress. Notably, B1R OE upregulated the expression of programmed death-ligand 1 in both GBM cells and macrophages, thus providing resistance against T-cell response. B1R OE in GBM also promoted tumor growth and reduced survival rates in an intracranial xenograft mouse model. These results indicate that B1R expression in GBM promotes TAM activity and modulates GBM progression. Therefore, B1R could be an effective target for therapeutic methods in GBM.

Bradykinin and Neurotensin Analogues as Potential Compounds in Colon Cancer Therapy

Colorectal cancer (CRC) is one of the most lethal malignancies worldwide, so the attempts to find novel therapeutic approaches are necessary. The aim of our study was to analyze how chemical modifications influence physical, chemical, and biological properties of the two peptides, namely, bradykinin (BK) and neurotensin (NT). For this purpose, we used fourteen modified peptides, and their anti-cancers features were analyzed on the HCT116 CRC cell line. Our results confirmed that the spherical mode of a CRC cell line culture better reflects the natural tumour microenvironment. We observed that the size of the colonospheres was markedly reduced following treatment with some BK and NT analogues. The proportion of CD133+ cancer stem cells (CSCs) in colonospheres decreased following incubation with the aforementioned peptides. In our research, we found two groups of these peptides. The first group influenced all the analyzed cellular features, while the second seemed to include the most promising peptides that lowered the count of CD133+ CSCs with parallel substantial reduction in CRC cells viability. These analogues need further analysis to uncover their overall anti-cancer potential.

An overview of kinin mediated events in cancer progression and therapeutic applications

Kinins are bioactive peptides generated in the inflammatory milieu of the tissue microenvironment, which is involved in cancer progression and inflammatory response. Kinins signals through activation of two G-protein coupled receptors; inducible Bradykinin Receptor B1 (B1R) and constitutive receptor B2 (B2R). Activation of kinin receptors and its cross-talk with receptor tyrosine kinases activates multiple signaling pathways, including ERK/MAPK, PI3K, PKC, and p38 pathways regulating cancer hallmarks. Perturbations of the kinin-mediated events are implicated in various aspects of cancer invasion, matrix remodeling, and metastasis. In the tumor microenvironment, kinins initiate fibroblast activation, mesenchymal stem cell interactions, and recruitment of immune cells. Albeit the precise nature of kinin function in the metastasis and tumor microenvironment are not completely clear yet, several kinin receptor antagonists show anti-metastatic potential. Here, we showcase an overview of the complex biology of kinins and their role in cancer pathogenesis and therapeutic aspects.

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.

Bradykinin Promotes Cell Proliferation, Migration, Invasion, and Tumor Growth of Gastric Cancer Through ERK Signaling Pathway

Bradykinin (BK) has been reported to be involved in the progression of diverse types of cancer. In the present study, we investigated the possible role of BK in cell proliferation, migration, invasion, and tumor growth of gastric cancer (GC). Cell proliferation was evaluated by MTT assays. Cell migration and invasion were assessed by Transwell assays. Tumor growth of nude mice was detected by establishing subcutaneous xenograft tumor model. Silencing of bradykinin B1 receptor (B1R) and the bradykinin B2 receptor (B2R) was performed by transfecting cells with si-B1R and si-B2R, respectively. The protein expression levels of phospho-ERK1/2 (p-ERK1/2), matrix metalloproteinase (MMP)-2, MMP-9, and E-Cadherin were examined by Western blot. Data revealed that BK promoted cell proliferation, migration, invasion, and the in vivo tumor growth of GC cells SGC-7901 and HGC-27. Furthermore, BK elevated the protein levels of p-ERK1/2, MMP-2, and MMP-9, but reduced E-Cadherin. In addition, by repressing B2R using si-B2R or inhibiting ERK signaling pathway using PD98059, BK-mediated promotion of cell proliferation, migration, and invasion and upregulation of p-ERK1/2, MMP-2/9, as well as downregulation of E-Cadherin were attenuated. Taken together, the present study demonstrated that BK promoted cell proliferation, migration, invasion, and tumor growth by binding to B2R via ERK signaling pathway. Our findings may provide promising options for the further treatment of GC. J. Cell. Biochem. 118: 4444-4453, 2017. © 2017 Wiley Periodicals, Inc.

ATP/pH Dual Responsive Nanoparticle with d-[des-Arg10 ]Kallidin Mediated Efficient In Vivo Targeting Drug Delivery

Inflammation has been reported as one significant hallmark of breast cancer in relation to tumor development, metastasis, and invasion. The bradykinin receptor 1 (B1R) is highly expressed on inflammatory breast tumor cells thus providing a promising targeting site for tumor recognition and sufficient receptor mediated endocytosis. In this study, the authors evaluate the targeting efficiency of l-form and d-form [des-Arg¹⁰ ]kallidin both in vitro and in vivo. To further improve the drug delivery efficiency, the authors establish a dandelion like nanoparticle by combining the polymeric drug conjugates and aptamer complex together. The doxorubicin conjugated polymer is complexed with adenosine-5'-triphosphate (ATP) sensitive hybridized aptamer in self-assembly process by intercalating into the double strand scaffolds. The acid labile conjugating bond and ATP sensitive aptamer endow the nanoparticle with dual responsiveness to intracellular milieu, thus triggering a quick drug release in tumor cells. Remarkable therapeutic effects and tuned in vivo pharmacokinetics profiles are shown by the aptamer complexed drug conjugates nanoparticle with B1R active targeting modification. Therefore the strategies of B1R targeting and ATP/pH dual-responsiveness nanoparticle help achieve enhanced drug accumulation within tumor cells and efficient chemotherapy for breast cancer.

Targeting cells of the myeloid lineage attenuates pain and disease progression in a prostate model of bone cancer

Tumor cells frequently metastasize to bone where they can generate cancer-induced bone pain (CIBP) that can be difficult to fully control using available therapies. Here, we explored whether PLX3397, a high-affinity small molecular antagonist that binds to and inhibits phosphorylation of colony-stimulating factor-1 receptor, the tyrosine-protein kinase c-Kit, and the FMS-like tyrosine kinase 3, can reduce CIBP. These 3 targets all regulate the proliferation and function of a subset of the myeloid cells including macrophages, osteoclasts, and mast cells. Preliminary experiments show that PLX3397 attenuated inflammatory pain after formalin injection into the hind paw of the rat. As there is an inflammatory component in CIBP, involving macrophages and osteoclasts, the effect of PLX3397 was explored in a prostate model of CIBP where skeletal pain, cancer cell proliferation, tumor metastasis, and bone remodeling could be monitored in the same animal. Administration of PLX3397 was initiated on day 14 after prostate cancer cell injection when the tumor was well established, and tumor-induced bone remodeling was first evident. Over the next 6 weeks, sustained administration of PLX3397 attenuated CIBP behaviors by approximately 50% and was equally efficacious in reducing tumor cell growth, formation of new tumor colonies in bone, and pathological tumor-induced bone remodeling. Developing a better understanding of potential effects that analgesic therapies have on the tumor itself may allow the development of therapies that not only better control the pain but also positively impact disease progression and overall survival in patients with bone cancer.

Pain in the cancer patient: different pain characteristics CHANGE pharmacological treatment requirements

Twenty years ago, the main barriers to successful cancer pain management were poor assessment by physicians, and patients' reluctance to report pain and take opioids. Those barriers are almost exactly the same today. Cancer pain remains under-treated; in Europe, almost three-quarters of cancer patients experience pain, and almost a quarter of those with moderate to severe pain do not receive any analgesic medication. Yet it has been suggested that pain management could be improved simply by ensuring that every consultation includes the patient's rating of pain, that the physician pays attention to this rating, and a plan is agreed to increase analgesia when it is inadequate. After outlining current concepts of carcinogenesis in some detail, this paper describes different methods of classifying and diagnosing cancer pain and the extent of current under-treatment. Key points are made regarding cancer pain management. Firstly, the pain may be caused by multiple different mechanisms and therapy should reflect those underlying mechanisms - rather than being simply based on pain intensity as recommended by the WHO three-step ladder. Secondly, a multidisciplinary approach is required which combines both pharmacological and non-pharmacological treatment, such as psychotherapy, exercise therapy and electrostimulation. The choice of analgesic agent and its route of administration are considered, along with various interventional procedures and the requirements of palliative care. Special attention is paid to the treatment of breakthrough pain (particularly with fast-acting fentanyl formulations, which have pharmacokinetic profiles that closely match those of breakthrough pain episodes) and chemotherapy-induced neuropathic pain, which affects around one third of patients who receive chemotherapy. Finally, the point is made that medical education should place a greater emphasis on pain therapy, both at undergraduate and postgraduate level.

The role of kinin receptors in cancer and therapeutic opportunities

Kinins are generated within inflammatory tissue microenvironments, where they exert diverse functions, including cell proliferation, leukocyte activation, cell migration, endothelial cell activation and nociception. These pleiotropic functions depend on signaling through two cross talking receptors, the constitutively expressed kinin receptor 2 (B2R) and the inducible kinin receptor 1 (B1R). We have reviewed evidence, which supports the concept that kinin receptors, especially kinin receptor 1, are promising targets for cancer therapy, since (1) many tumor cells express aberrantly high levels of these receptors; (2) some cancers produce kinins and use them as autocrine factors to stimulate their growth; (3) activation of kinin receptors leads to activation of macrophages, dendritic cells and other cells from the tumor microenvironment; (4) kinins have pro-angiogenic properties; (5) kinin receptors have been implicated in cancer migration, invasion and metastasis; and (6) selective antagonists for either B1R or B2R have shown anti-proliferative, anti-inflammatory, anti-angiogenic and anti-migratory properties. The multiple cross talks between kinin receptors and renin-angiotensin system (RAS) as well as its implications for targeting KKS or RAS for the treatment of malignancies are also discussed. It is expected that B1R antagonists would interfere less with housekeeping functions and therefore would be attractive compounds to treat selected types of cancer. Reliable clinical studies are needed to establish the translatability of these data to human settings and the usefulness of kinin receptor antagonists.

Interaction between bradykinin and natriuretic peptides via RGS protein activation in HEK-293 cells

In this study, the interaction of natriuretic peptides (NP) and bradykinin (BK) signaling pathways was identified by measuring membrane potential (V(m)) and intracellular Ca(2+) using the patch-clamp technique and flow cytometry in HEK-293 cells. BK and NP receptor mRNA was identified using RT-PCR. BK (100 nM) depolarized cells activating bradykinin receptor type 2 (B(2)R) and Ca(2+)-dependent Cl(-) channels inhibitable by 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB; 10 μM). The BK-induced Ca(2+) signal was blocked by the B(2)R inhibitor HOE 140. [Des-Arg(9)]-bradykinin, an activator of B(1)R, had no effect on intracellular Ca(2+). NP [atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), C-type natriuretic peptide (CNP), and urodilatin] depolarized HEK-293 cells inhibiting K(+) channels. ANP, urodilatin, BNP [binding to natriuretic peptide receptor (NPR)-A] and 8-bromo-(8-Br)-cGMP inhibited the BK-induced depolarization while CNP (binding to NPR-Bi) failed to do so. The inhibitory effect on BK-triggered depolarization could be reversed by blocking PKG using the specific inhibitor KT 5823. BK-stimulated depolarization as well as Ca(2+) signaling was completely blocked by the phospholipase C (PLC) inhibitor U-73122 (10 nM). The inositol 1,4,5-trisphosphate receptor blocker 2-aminoethoxydiphenyl borate (2-APB; 50 μM) completely inhibited the BK-induced Ca(2+) signaling. UTP, another activator of the PLC-mediated Ca(2+) signaling pathway, was blocked by U-73122 as well but not by 8-Br-cGMP, indicating an intermediate regulatory step for NP via PKG in BK signaling such as regulators of G-protein signaling (RGS) proteins. When RGS proteins were inhibited by CCG-63802 in the presence of BK and 8-Br-cGMP, cells started to depolarize again. In conclusion, as natural antagonists of the B(2)R signaling pathway, NP may also positively interact in pathological conditions caused by BK.

Antitumor mechanisms of targeting the PDK1 pathway in head and neck cancer

G-protein-coupled receptors (GPCR) activate the epidermal growth factor receptor (EGFR) and mediate EGFR-independent signaling pathways to promote the growth of a variety of cancers, including head and neck squamous cell carcinoma (HNSCC). Identification of the common signaling mechanisms involved in GPCR-induced EGFR-dependent and EGFR-independent processes will facilitate the development of more therapeutic strategies. In this study, we hypothesized that phosphoinositide-dependent kinase 1 (PDK1) contributes to GPCR-EGFR cross-talk and signaling in the absence of EGFR and suggests that inhibition of the PDK1 pathway may be effective in the treatment of HNSCC. The contribution of PDK1 to the EGFR-dependent and EGFR-independent signaling in HNSCC was determined using RNA interference, a kinase-dead mutant, and pharmacologic inhibition. In vivo xenografts studies were also carried out to determine the efficacy of targeting PDK1 alone or in combination with the U.S. Food and Drug Administration-approved EGFR inhibitor cetuximab. PDK1 contributed to both GPCR-induced EGFR activation and cell growth. PDK1 also mediated activation of p70S6K in the absence of EGFR. Blockade of PDK1 with a small molecule inhibitor (AR-12) abrogated HNSCC growth, induced apoptosis, and enhanced the antiproliferative effects of EGFR tyrosine kinase inhibitors in vitro. HNSCC xenografts expressing kinase-dead PDK1 showed increased sensitivity to cetuximab compared with vector-transfected controls. Administration of AR-12 substantially decreased HNSCC tumor growth in vivo. These cumulative results show that PDK1 is a common signaling intermediate in GPCR-EGFR cross-talk and EGFR-independent signaling, and in which targeting the PDK1 pathway may represent a rational therapeutic strategy to enhance clinical responses to EGFR inhibitors in HNSCC.

GPRC6A regulates prostate cancer progression

BACKGROUND

GPRC6A is a nutrient sensing GPCR that is activated in vitro by a variety of ligands, including amino acids, calcium, zinc, osteocalcin (OC), and testosterone. The association between nutritional factors and risk of prostate cancer, the finding of increased expression of OC in prostate cancer cells, and the association between GPRC6A and risk of prostate cancer in Japanese men implicates a role of GPRC6A in prostate cancer.

METHODS

We examined if GPRC6A is expressed in human prostate cancer cell lines and used siRNA-mediated knockdown GPRC6A expression in prostate cancer cells to explore the function of GPRC6A in vitro. To assess the role of GPRC6A in prostate cancer progression in vivo, we intercrossed Gprc6a(-/-) mice onto the TRAMP mouse prostate cancer model.

RESULTS

GPRC6A transcripts were markedly increased in prostate cancer cell lines 22Rv1, PC-3, and LNCaP, compared to the normal prostate RWPE-1 cell line. In addition, a panel of GPRC6A ligands, including calcium, OC, and arginine, exhibited in prostate cancer cell lines a dose-dependent stimulation of ERK activity, cell proliferation, chemotaxis, and prostate specific antigen and Runx2 gene expression. These responses were inhibited by siRNA-mediated knockdown of GPRC6A. Finally, transfer of Gprc6a deficiency onto a TRAMP mouse model of prostate cancer significantly retarded prostate cancer progression and improved survival of compound Gprc6a(-/-) /TRAMP mice.

CONCLUSIONS

GPRC6A is a novel molecular target for regulating prostate growth and cancer progression. Increments in GPRC6A may augment the ability of prostate cancer cells to proliferate in response to dietary and bone derived ligands.

The bradykinin B1 receptor antagonist R-954 inhibits Ehrlich tumor growth in rodents

The present study investigated the effects of a new bradykinin B(1) receptor antagonist, R-954, on the development of Ehrlich ascitic tumor (EAT) induced by the intraperitoneal inoculation of EAT cells in mice and the formation of a solid tumor by the subcutaneous injection of the cells in rat paw. The development of the tumor was associated with an increase in mouse total cell counts in bone marrow (10.8-fold), ascitic fluid (14.6-fold), and blood (12.6-fold). R-954 (2mg/kg, s.c.) significantly reduced the ascitic fluid volume (63.7%) and the mouse weight gain (30.5%) after 10 consecutive days of treatment. The B(1) antagonist as well as the anti-neoplasic drug vincristine also significantly inhibited the increase in total cell count in bone marrow, ascitic fluid, and blood. R-954 reduced significantly the total protein extravasation (57.3%), the production of nitric oxide (56%), PGE(2) production (82%), and TNFα release (85.7%) in mice peritoneal cavity whereas vincristine reduced the release of these inflammatory mediators by 84-94%. The increase in paw edema after intraplantar injection of EAT cells was reduced by approximately 52% by either R-954 or vincristine treatment. In conclusion, this study presents for the first time the antitumoral activity of a new bradykinin B(1) receptor antagonist on ascitic and solid tumors induced by Ehrlich cell inoculation in mice and rats.

Peptide hormone regulation of angiogenesis

It is now apparent that regulation of blood vessel growth contributes to the classical actions of hormones on development, growth, and reproduction. Endothelial cells are ideally positioned to respond to hormones, which act in concert with locally produced chemical mediators to regulate their growth, motility, function, and survival. Hormones affect angiogenesis either directly through actions on endothelial cells or indirectly by regulating proangiogenic factors like vascular endothelial growth factor. Importantly, the local microenvironment of endothelial cells can determine the outcome of hormone action on angiogenesis. Members of the growth hormone/prolactin/placental lactogen, the renin-angiotensin, and the kallikrein-kinin systems that exert stimulatory effects on angiogenesis can acquire antiangiogenic properties after undergoing proteolytic cleavage. In view of the opposing effects of hormonal fragments and precursor molecules, the regulation of the proteases responsible for specific protein cleavage represents an efficient mechanism for balancing angiogenesis. This review presents an overview of the actions on angiogenesis of the above-mentioned peptide hormonal families and addresses how specific proteolysis alters the final outcome of these actions in the context of health and disease.

Activin receptor signaling regulates prostatic epithelial cell adhesion and viability

Mutational changes coupled with endocrine, paracrine, and/or autocrine signals regulate cell division during carcinogenesis. The hormone signals remain undefined, although the absolute requirement in vitro for fetal serum indicates the necessity for a fetal serum factor(s) in cell proliferation. Using prostatic cancer cell (PCC) lines as a model of cancer cell proliferation, we have identified the fetal serum component activin A and its signaling through the activin receptor type II (ActRII), as necessary, although not sufficient, for PCC proliferation. Activin A induced Smad2 phosphorylation and PCC proliferation, but only in the presence of fetal bovine serum (FBS). Conversely, activin A antibodies and inhibin A suppressed FBS-induced PCC proliferation confirming activin A as one of multiple serum components required for PCC proliferation. Basic fibroblast growth factor was subsequently shown to synergize activin A-induced PCC proliferation. Inhibition of ActRII signaling using a blocking antibody or antisense-P decreased mature ActRII expression, Smad2 phosphorylation, and the apparent viability of PCCs and neuroblastoma cells grown in FBS. Suppression of ActRII signaling in PCC and neuroblastoma cells did not induce apoptosis as indicated by the ratio of active/inactive caspase 3 but did correlate with increased cell detachment and ADAM-15 expression, a disintegrin whose expression is strongly correlated with prostatic metastasis. These findings indicate that ActRII signaling is required for PCC and neuroblastoma cell viability, with ActRII mediating cell fate via the regulation of cell adhesion. That ActRII signaling governs both cell viability and cell adhesion has important implications for developing therapeutic strategies to regulate cancer growth and metastasis.

Remnant lipoproteins stimulate proliferation and activate MAPK and Akt signaling pathways via G protein-coupled receptor in PC-3 prostate cancer cells

BACKGROUND

Hypertriglyceridemia was recently shown to be a risk factor for prostate cancer; however, there are only a few reports about the relationship between prostate cancer and TG (triglycerides) rich lipoproteins. Remnant lipoproteins (RLP) are TG-rich lipoproteins, which are produced by the hydrolysis of very low density lipoproteins and chylomicrons. We examined the direct effect of RLP on the proliferation and signal transduction of prostate cancer cells.

METHODS

RLP were isolated from human serum with an immunoaffinity mixed gel containing anti-apoA-1 and anti-apoB-100. We evaluated RLP-induced cell proliferation by using MTS assay. Moreover we examined the direct effect of RLP on the MAPK and Akt signal transductions which are reported to be correlated with prostate cancer by using Western blotting.

RESULTS

Incubation in the presence of RLP for 48 h induced the proliferation of prostate cancer PC-3 cells more significantly than prostate cancer LNCaP cells and human prostate stromal cells. In PC-3 cells, RLP also induced the phosphorylation of MEK/ERK via a G protein-coupled receptor-protein kinase C dependent pathway. Moreover, activation of Akt pathway was observed after RLP treatment of PC-3.

CONCLUSION

These findings suggested that hypertriglyceridemia, especially remnant hyperlipoproteinemia, might be one of the progressive factors for prostate cancer.

New bradykinin analogues substituted in positions 7 and 8 with sterically restricted 1-aminocyclopentane-1-carboxylic acid

A sterically constrained non-coded amino acid, 1-aminocyclopentane-1-carboxylic acid (Apc), was introduced in position 7 or 8 of the bradykinin (BK) B(2) receptor antagonist, [D-Arg(0), Hyp(3), Thi(5, 8), D-Phe(7)]BK, previously synthesized by Stewart's group. This modification is believed to reduce the flexibility of the peptides, thereby forcing the peptide backbone and side chains to adopt specific orientations. Apc substitution was combined with acylation of the N-terminus with 1-adamantaneacetic acid (Aaa). The activity of four new analogues was assayed in isolated rat uterus and in rat blood pressure tests. The results clearly demonstrated that the Apc residue inserted in position 7 led to a reduction of antagonistic properties in the rat uterus assay or even restored the agonism in the blood pressure test, whereas Apc at position 8 enhanced antagonistic potency in both the tests. In both cases, acylation of the N-terminus led to the enhancement of the antagonistic potency. On the basis of these findings, new potent and selective B(2) blockers might be designed.

New Bradykinin Analogues Modified in the C-Terminal Part with Sterically Restricted 1-Aminocyclohexane-1-carboxylic Acid

In the present work, a sterically constrained noncoded amino acid, 1-aminocyclohexane-1-carboxylic acid (Acc), was substituted in position 8 of the peptide chain of bradykinin (BK) and position 6, 7, or 8 of its B2 receptor antagonist [D-Arg0,Hyp3,Thi,(5,8)D-Phe7]BK, previously synthesized by Stewart's group, to reduce the flexibility of the peptides, thus forcing the peptide backbone and side chains to adopt specific orientations. Knowing that acylation of the N-terminus of several known B2 blockers with a variety of bulky groups has consistently improved their antagonistic potency in the rat blood pressure assay, the Acc substituted analogues were also synthesized in the N-acylated form with 1-adamantaneacetic acid (Aaa). The activity of eight new analogues was assayed in isolated rat uterus and in rat blood pressure tests. The results clearly demonstrated the importance of the position in the peptide chain into which the sterically restricted Acc residue was inserted. Meanwhile, Acc at positions 6 and 7 led to reduction of antagonistic qualities or even restored the agonism, respectively. Acc at position 8 enhanced antagonistic qualities in both tests. The Acc at position 8 of BK strongly reduced the agonistic potency. In most cases acylation of the N-terminus led either to enhancement of antagonistic potencies or to further decrease of agonistic potency. Our findings offer new possibilities for designing new potent and selective B2 blockers.

Discovery of 2-Arylthiazolidine-4-carboxylic Acid Amides as a New Class of Cytotoxic Agents for Prostate Cancer†

To improve the selectivity and antiproliferative activity of previously reported serine amide phosphates (SAPs), we designed a new series of 4-thiazolidinone amides, in which the 4-thiazolidinone moiety was introduced as a phosphate mimic. However, these 4-thiazolidinone derivatives demonstrated less cytotoxicity in prostate cancer cells despite improved selectivity over RH7777 cells. To further optimize the thiazolidinone analogues in terms of cytotoxicity and selectivity, we made closely related structural modifications, which led us to the discovery of a new class of 2-arylthiazolidine-4-carboxylic acid amides. These compounds were potent cytotoxic agents with IC(50) values in the low micromolar concentration range and demonstrated enhanced selectivity in receptor-negative cells compared to SAPs and 4-thiazolidinone amides.

Pharmacological characterization of canine bradykinin receptors in prostatic culture and in isolated prostate

The objective of this study was to characterize pharmacologically bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg, BK) receptors in the canine prostate. Primary cultures of canine prostate stromal (PS) and epithelial cells (PE) were established and then characterized using cell-specific antibodies (actin, vimentin and cytokeratin). Cultured cells were assayed for BK receptors using fluorometric imaging plate reader assays. In addition, isolated strips of the canine prostate were studied for BK-induced isometric contraction. PS cells were labeled only with anti-actin and -vimentin antibodies, while the anti-cytokeratin antibodies labeled only the PE cells. In cultured prostate cells, the BK receptor 2 (B2)-preferring agonist BK induced mobilization of intracellular Ca(2+) in a concentration-dependent manner with potencies (log[EC(50)]mid R:PE, pEC(50)) of 8.72+/-0.12 in PS and 8.75+/-0.06 in PE cells. In contrast, the BK receptor 1 (B1)-selective agonist [des-Arg(9)]BK (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe) did not elicit any significant effect (pEC(50)<5) on Ca(2+) responses. BK agonism (10 nm) was inhibited by HOE-140 (D-arginyl-L-arginyl-L-prolyl-trans-4-hydroxy-L-prolylglycyl-3-(2-thienyl)-L-alanyl-L-seryl-D-1,2,3,4-tetrahhydro-3-isoquinolinecarbonyl-L-(2a,3b,7ab)-octahydro-1H-indole-2-carbonyl-L-arginine), a B2-selective antagonist, with a log[IC(50)] (pIC(50)) of 8.11+/-0.19 and 9.23+/-0.20 in PS and PE cells, respectively. [des-Arg(10)]HOE-140 (d-arginyl-l-arginlyl-l-prolyl-trans-4-hydroxy-l-prolylglycyl-3-(2-thienyl)-L-alanyl-L-seryl-D-1,2,3,4-tetrahydro-3-isoquinolinecarbonyl-L-(2a, 3b,7ab)-octahydro-1H-indole-2-carbonyl), a B1-selective antagonist, displayed weak antagonism with pIC(50) values of 4.87+/-0.23 and 6.38+/-0.16 in PS and PE cells, respectively. Isolated tissue strips of the canine prostate contracted to BK (10 microm) but not to [des-Arg(9)]BK (10 microm). BK-induced contractility was attenuated by HOE-140 (1 microm). In conclusion, canine prostates express functional B2 receptors, with no apparent B1 receptor subtypes.

Pharmacological and functional characterization of bradykinin B2 receptor in human prostate

The objective of this study was to pharmacologically characterize bradykinin receptors, a component of the kallikrein-kinin system, in normal human prostate cells. In primary cultured human prostate stromal cells, bradykinin, but not [des-Arg9]bradykinin or [des-Arg10]kallidin, produced calcium mobilization or inositol phosphates accumulation with potencies (pEC50) of 8.8+/-0.2 and 8.2+/-0.2, respectively. This was consistent with abundance of bradykinin B2 mRNA over bradykinin B1 mRNA in prostate stromal cells. Although the prostate epithelial cells (prostate epithelium, BPH-1, and PC-3) expressed mRNA for bradykinin B2 receptors (albeit in lesser amounts than stromal cells), bradykinin was not functionally efficacious in the epithelial cells. Increasing concentrations of D-arginyl-L-arginyl-L-prolyl-trans-4-hydroxy-L-prolylglycyl-3-(2-thienyl)-L-alanyl-L-seryl-D-1,2,3,4-tetrahhydro-3-isoquinolinecarbonyl-L-(2alpha,3beta,7alphabeta)-octahydro-1H-indole-2-carbonyl-L-arginine (HOE-140), a bradykinin B2-selective peptide antagonist, attenuated bradykinin concentration-response curves in human prostate stromal cells with apparent estimate of affinity similar to that for the human bradykinin B2 receptor. Bradykinin (10 nM) caused proliferation of prostate stromal cells and phosphorylated extracellular signal-regulated kinases (ERK-1 and ERK-2) that were blocked by HOE-140 (1 microM). This study demonstrated that, in primary cultures of normal human prostate stromal cells, bradykinin activates bradykinin B2 receptors that may play a significant role in proliferation via activation of ERK-1/2 pathways.

Lysophosphatidic acid promotes survival of androgen-insensitive prostate cancer PC3 cells via activation of NF-kappaB

BACKGROUND

Dysregulated cell survival contributes to the poor efficacy of many chemotherapeutic regimens for patients with advanced prostate cancer. In this study we examined ability of the lipid growth factor lysophosphatidic acid (LPA), a G protein-coupled receptor (GPCR) ligand, to promote prostate cell survival.

METHODS

PC3 cells were used as a model to study mechanisms involved in survival of androgen-insensitive prostate cancer cells. Cell survival was measured by FACS analysis of cell cycle parameters after propidium iodide or annexin V and 7-AAD immunostaining. Activation state of nuclear facor-kappaB (NF-kappaB) was determined biochemically by nuclear translocation and transcriptional activation. Human tissue was analyzed for nuclear expression of NF-kappaB by immunohistochemistry.

RESULTS

Molecular dissection of the LPA-regulated PC3 cell survival revealed the sequential phosphorylation of Akt, IkappaB, and transcriptional activation of NF-kappaB. Both Akt and NF-kappaB were required to escape serum deprivation-induced cell death since their inhibition abrogated the LPA-mediated PC3 cell survival. Data from archival human tissue show that NF-kappaB is constitutively activated in prostate cancers, but not in benign prostate tissues.

CONCLUSIONS

Targeted disruption of the LPA receptor-Akt-NF-kappaB signaling axis may be effective for the treatment of androgen-insensitive prostate cancer.

Involvement of MAP-kinase, PI3-kinase and EGF-receptor in the stimulatory effect of Neurotensin on DNA synthesis in PC3 cells

The mechanism by which neurotensin (NT) promotes the growth of prostate cancer epithelial cells is not yet defined. Here, androgen-independent PC3 cells, which express high levels of the type 1 NT-receptor (NTR1), are used to examine the involvement of epidermal growth factor receptor (EGFR), mitogen-activated protein kinases (ERK, SAPK/JNK and p38), PI3 kinase and PKC in the mitogenic effect of NT. NT dose dependently (0.1-30 nM) enhanced phosphorylation of EGFR, ERK and Akt, reaching maximal levels within 3 min as measured by Western blotting. These effects were associated with an accumulation of EGF-like substance(s) in the medium (assayed by EGFR binding) and a 2-fold increase in DNA synthesis (assayed by [3H]thymidine incorporation). The DNA synthesis enhancement by NT was non-additive with that of EGF. The NT-induced stimulation of EGFR/ERK/Akt phosphorylation and DNA synthesis was inhibited by EGFR-tyrosine kinase inhibitors (AG1478, PD153035), metallo-endopeptidase inhibitor phosphoramidon and by heparin, but not by neutralizing anti-EGF antibody. Thus, transactivation of EGFR by NT involved heparin-binding EGF (HB-EGF or amphiregulin) rather than EGF. The effects of NT on EGFR/ERK/Akt activation and DNA synthesis were attenuated by PLC-inhibitor (U73122), PKC-inhibitors (bisindolylmaleimide, staurosporine, rottlerin), MEK inhibitor (U0126) and PI3 kinase inhibitors (wortmannin, LY 294002). We conclude that NT stimulated mitogenesis in PC3 cells by a PKC-dependent ligand-mediated transactivation of EGFR, which led to stimulation of the Raf-MEK-ERK pathway in a PI3 kinase-dependent manner.

Interleukin 6 mediates the lysophosphatidic acid-regulated cross-talk between stromal and epithelial prostate cancer cells

The interaction between stromal and epithelial cells is critical for the initiation and progression of prostate cancer, but the molecular determinants responsible for the cross-talk between these two cell types remain largely unknown. Here, we used a co-culture cell assay to identify messengers involved in the cross-talk between human prostate stromal PS30 and epithelial LNCaP cells. Stimulation with lysophosphatidic acid (LPA) activates the mitogenic ERK signaling pathway in PS30, but not LNCaP, cells. The co-culture of PS30 and LNCaP cells results in the activation of ERK in LNCaP cells and that is further increased in response to stimulation with LPA. Physiologic relevance of the interaction between PS30 and LNCaP cells is demonstrated using LNCaP xenograft tumor assays. Animals implanted with a mixture of both cell types develop larger tumors with higher frequency compared with those injected with LNCaP cells alone. Conditioned medium transfer experiments reveal the PS30-derived inducing factor is soluble and promotes mitogenic ERK and STAT3 signaling pathways in LNCaP cells. Protein analysis demonstrates that treatment of the PS30 cells with LPA induces synthesis of interleukin 6 (IL-6). Antibody neutralization experiments reveal that IL-6 is responsible for the LPA-induced mitogenic signaling and growth of the LNCaP cells. Our findings reveal that the LPA-regulated secretion of IL-6 is an important messenger linking stromal and epithelial prostate cells, which may be exploited for the effective treatment of patients with advanced prostate cancer.

Bradykinin antagonists: discovery and development

Practical bradykinin antagonists were discovered in 1984 by Vavrek and Stewart and reported in "Peptides." At that time there was already much evidence for involvement of bradykinin in inflammation and pain, so the specific, competitive antagonists were widely accepted and applied. The key to conversion of bradykinin into an antagonist was replacement of the proline residue at position 7 with a D-aromatic amino acid. Other modifications converted the initial weak antagonists into modern peptides which are totally resistant to all degrading enzymes, are orally available, and have been used in clinical trials. Non-peptide bradykinin antagonists have also been developed.

G Proteins in Cancer: The Prostate Cancer Paradigm

Signal transduction research investigating mechanisms of androgen-independent prostate cancer cell proliferation has historically focused on the role of androgen and peptide growth factor receptors. More recent work has raised the idea that intracellular signaling mechanisms triggered by extracellular hormonal factors acting through heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) can also mediate and sustain this pathologic process. Prostate cancer patients with advanced disease express elevated levels of GPCRs and GPCR ligands, suggesting that the GPCR system is activated in the cancerous gland and may contribute to tumor growth. Importantly, inhibition of G protein signaling attenuates prostate cancer cell growth in animal models. The nature of intracellular signaling pathways mediating mitogenic effects of GPCRs in prostate cancer is poorly defined, although the G protein-dependent activation of the Ras-to-mitogen-activated protein kinase pathway has emerged as a critical regulatory event. Activated GPCRs may also exert their mitogenic effects in the prostate by activating the androgen receptor.

Mitogenic signalling by B2 bradykinin receptor in epithelial breast cells

The kinin peptides are released during inflammation and are amongst the most potent known mediators of vasodilatation, pain, and oedema. A role in the modulation or induction of healthy breast tissue growth has been postulated for tissue kallikrein present in human milk. Moreover, tissue kallikrein was found in malignant human breast tissue and bradykinin (BK) stimulates the proliferation of immortalised breast cancer cells. Aim of the present article was to investigate whether BK also exerts mitogenic activity in normal breast epithelial cells and partially characterise the signalling machinery involved. Results show that BK increased up to 2-fold the 24 h proliferation of breast epithelial cells in primary culture, and that the BK B2 receptor (not B1) inhibitor alone fully blocked the BK response. Intracellular effects of B2 stimulation were the following: (a) the increase of free intracellular Ca(2+) concentration by a mechanism dependent upon the phospholipase C (PLC) activity; (b) the cytosol-to-membrane translocation of conventional (PKC)-alpha and -beta isozymes, novel PKC-delta, -epsilon, and -eta isozymes; (c) the phosphorylation of the extracellular-regulated kinase 1 and 2 (ERK1/2); and (d) the stimulation of the expression of c-Fos protein. EGF, a well known stimulator of cell proliferation, regulated the proliferative response in human epithelial breast cells to the same extent of BK. The effects of BK on proliferation, ERK1/2 phosphorylation, and c-Fos expression were abolished by GF109203X, which inhibits PKC-delta isozyme. Conversely, Gö6976, an inhibitor of PKC-alpha and -beta isozymes, and the 18-h treatment of cells with PMA, that led to the complete down-regulation of PKC-alpha, -beta, -epsilon, and -eta, but not of PKC-delta, did not have any effect, thereby indicating that the PKC-delta mediates the mitogenic signalling of BK. Phosphoinositide 3-kinase (PI3K), tyrosine kinase of the epidermal growth factor receptor (EGFR), and mitogen activated protein kinase kinases (MEK) inhibitors were also tested. The results suggest that EGFR, PI3K, and ERK are required for the proliferative effects of BK. In addition, the BK induced cytosol-to-membrane translocation of PKC-delta was blocked by PI3K inhibition, suggesting that PI3K is upstream to PKC-delta. In conclusion, BK has mitogenic actions in cultured human epithelial breast cells; the activation of PKC-delta through B2 receptor acts in concert with ERK and PI3K pathways to induce cell proliferation.

Targeting Gbetagamma signaling to inhibit prostate tumor formation and growth

Prostate cancer starts as androgen-dependent malignancy and responds initially to androgen ablative therapy. Beneficial effects of androgen ablation, however, are often temporary and the cancer reappears as androgen-independent tumor, suggesting the existence of additional factors responsible for progression of the disease. Attention has focused on receptor tyrosine kinases as the growth mediators of androgen-independent prostate cancer; overexpression of epidermal growth factor receptors or their ligand heparin-bound epidermal growth factor, for example, promotes transition to androgen independence. Emerging data demonstrate involvement of another class of cell membrane-anchored receptors, the heterotrimeric guanine-binding (G) protein-coupled receptors (GPCRs) in prostate cancer. In vitro, stimulation of many endogenous GPCRs induces mitogenic signaling and growth of prostate cancer cells. The GPCRs transduce mitogenic signals via activated G proteins in the form of Galpha-GTP and Gbetagamma subunits. Here, we show that expression of a Gbetagamma inhibitor peptide derived from carboxy terminus of G protein-coupled receptor kinase 2 obliterates serum-regulated prostate cancer cell growth in vitro and prevents prostate tumor formation in vivo. We also demonstrate that inhibition of Gbetagamma signaling retards growth of existing prostate tumors by inducing cell death. These data establish a central role for heterotrimeric G proteins in prostate cancer and suggest targeted inhibition of Gbetagamma signaling may serve as specific molecular therapy tool to limit pathologic growth of advanced prostate cancer.

Synergistic antiproliferative and apoptotic effects induced by epidermal growth factor receptor and protein kinase a inhibitors in human prostatic cancer cell lines

Our results revealed that the blockade of epidermal growth factor receptor (EGFR) tyrosine kinase and protein kinase A (PKA) signaling pathways by specific inhibitors (PD153035 and Rp-cAMPs) leads to a synergistic inhibition of EGF- and serum-stimulated growth of human prostatic cancer cells (LNCaP, DU145 and PC3) concomitant with an arrest in the G1 phase of cellular cycle. Of particular interest, the combination of PD153035 and Rp-cAMPs also caused a more substantial apoptotic/necrotic death of these prostatic cancer cells as compared to drugs alone. Moreover, we observed that the inhibition of acidic sphingomyelinase and caspase cascades results in a marked reduction of DNA fragmentation and apoptotic death induced by PD153035, alone or in combination with Rp-cAMPs, in EGF stimulated PC3 cells. This suggests that these agents might mediate their cytotoxic effects at least in part via the ceramide generation and activation of caspase signaling pathways. N-oleoylethanolamine (OE), an inhibitor of acidic ceramidase, consistently potentiated the apoptotic effects of PD153035 in all the prostatic cancer cell lines tested. Additionally, the cellular ceramide content estimated for PC3 cells was increased after treatment with PD153035, alone or in combination, at a lower dose with OE and Rp-cAMPs. The synergistic apoptotic effect of PD153035 plus Rp-cAMPs induced in PC3 was also accompanied by a significant rate of mitochondrial membrane depolarization and release of cytochrome c into cytosol as compared to drugs alone. Combined, the results indicated that the simultaneous inhibition of EGFR and PKA signaling cascades might lead to a more massive apoptotic death of metastatic prostatic cancer cells by increasing ceramide accumulation and activating of caspase cascade of a mitochondrial dependent manner.

New advances on prostate carcinogenesis and therapies: involvement of EGF-EGFR transduction system

The prostate cancers (PCs) are among the major causes of death because therapeutic treatments are not effective against advanced and metastatic forms of this cellular hyperproliferative disorder. In fact, although androgen-deprivation therapies permit to cure localized PC forms, the metastatic PC cells have acquired multiple functional features that confer to them resistance to ionizing radiations and anticarcinogenic drugs currently used in therapy. The present review describes last advances on molecular mechanisms that might be responsible for sustained growth and survival of PC cells. In particular, emphasis is on intracellular signaling cascades which are involved in the mitogenic and antiapoptotic effects of epidermal growth factor EGF-EGFR system. Of therapeutic interest, recent advances and prospects for development of new treatments against incurable forms of metastatic PC forms are also discussed.

Lysophosphatidic acid-regulated mitogenic ERK signaling in androgen-insensitive prostate cancer PC-3 cells

Advanced and recurrent prostate tumors contain elevated levels of activated extracellular signal-regulated kinases 1 and 2 (ERK) in comparison to early-stage or benign specimens, and inhibition of ERK activation attenuates growth factor-dependent proliferation of prostate cells, suggesting a potential regulatory role for ERK in prostate tumorigenesis. Factors responsible for ERK activation in prostate cells are not well defined. Here, we show positive cooperative interaction between the G protein-coupled lysophosphatidic acid (LPA) and tyrosine kinase epidermal growth factor (EGF) receptors in androgen-insensitive prostate cancer PC-3 cells. Pre-treatment of the PC-3 cells with LPA decreases the dose of EGF required to elicit maximal activation of EGFR. Furthermore, treatment with LPA alone induces the rapid (maximal signal within 2 min) tyrosine phosphorylation of EGFR, and subsequent (maximal signal after 5 min) activation of ERK, suggesting that EGFR activation precedes ERK phosphorylation and may constitute a required component for signal relay from the LPA receptor to ERK. Accordingly, we show that inhibition of EGFR kinase activity attenuates the LPA-regulated ERK activation. In addition, we find that the LPA-regulated tyrosine phosphorylation of EGFR and activation of ERK are attenuated by batimastat, a generic inhibitor of matrix metalloproteinases (MMP). However, unlike the situation in fibroblasts, we find that the LPA-induced transactivation of EGFR in PC-3 cells is not mediated by shedding of heparin-binding EGF. Together, our data show that LPA and EGF cooperate to induce mitogenic signaling in prostate cancer cells in an MMP-regulated activation of the ERK pathway.