Renin-angiotensin system is an important factor in hormone refractory prostate cancer

Association between 19 medication use and risk of common cancers: A cross-sectional and Mendelian randomisation study

Background

Previous studies have yielded inconsistent results concerning drug use and the risk of cancers. We conducted a large-scale cross-sectional study and a two-sample Mendelian randomisation (MR) study to reveal the causal effect between the use of 19 medications and the risk of four common cancers (breast, lung, colorectal, and prostate).

Methods

We obtained information on medication use and cancer diagnosis from National Health and Nutrition Examination Survey participants. After propensity score matching, we conducted survey-weighted multivariate logistic regression and restricted cubic spline analysis to assess the observed correlation between medication use and cancer while adjusting for multiple covariates. We also performed MR analysis to investigate causality based on summary data from genome-wide association studies on medication use and cancers. We performed sensitivity analyses, replication analysis, genetic correlation analysis, and reverse MR analysis to improve the reliability of MR findings.

Results

We found that the use of agents acting on the renin-angiotensin system was associated with reduced risk of prostate cancer (odds ratio (OR) = 0.42; 95% confidence interval (CI) = 0.27-0.63, P < 0.001), and there was a nonlinear association of 'decrease-to-increase-to-decrease' (P < 0.0001). The random-effects inverse variance weighted (IVW) model-based primary MR analysis (OR = 0.94, 95% CI = 0.91-0.97, P = 0.0007) and replication MR analysis (OR = 0.90, 95% CI = 0.85-0.96, P = 0.0006) both provided robust evidence of the causality of genetic liability for the use of agents acting on the renin-angiotensin system on a decreased risk of prostate cancer.

Conclusions

Our study provides robust evidence that the use of drugs acting on the renin-angiotensin system can reduce prostate cancer risk. Given the high prevalence of prostate cancer, these findings have important implications for drug selection and prostate cancer prevention in patients with cardiovascular disease.

EGCG oxidation-derived polymers induce apoptosis in digestive tract cancer cells via regulating the renin-angiotensin system

Green tea polyphenol (-)-Epigallocatechin-3-gallate (EGCG) has been well studied for its biological activities in the prevention of chronic diseases. However, the biological activities of EGCG oxidation-derived polymers remain unclear. Previously, we found that these polymers accumulated in intraperitoneal tissues after intraperitoneal injection and gained an advantage over native EGCG in increasing insulin sensitivity via regulating the renin-angiotensin system (RAS) in type 2 diabetic mice. The present study determined the pro-apoptosis activities and anticancer mechanisms of the EGCG oxidation-derived polymer preparation (the >10 kDa EGCG polymers) in digestive tract cancer cells. Upon incubation of the >10 kDa EGCG polymers with CaCo2 colon cancer cells, these polymers coated the cell surface and regulated multiple components of the RAS in favor of cancer inhibition, including the downregulation of angiotensin-converting enzyme (ACE), angiotensin-II (AngII) and AngII receptor type 1 (AT1R) in the pro-tumor axis, as well as the upregulation of angiotensin-converting enzyme 2 (ACE2) and angiotensin1-7 (Ang(1-7)) in the anti-tumor axis. The treatment also markedly increased angiotensinogen (AGT), which is the precursor of the angiotensin peptides. The regulation of these RAS components occurred prior to apoptosis. Similar pro-apoptotic mechanisms of the >10 kDa EGCG polymers, were also observed in TCA8113 oral cancer cells. The >10 kDa EGCG polymers exhibited compromised activities in scavenging or initiating reactive oxygen species compared to EGCG, but gained a higher reactivity toward sulfhydryl groups, including protein cysteine thiols. We propose that the polymers bind onto the cell surface and regulate multiple RAS components by reacting with the sulfhydryl groups on the ectodomains of transmembrane proteins.

The renin-angiotensin-aldosterone system (RAAS) signaling pathways and cancer: foes versus allies

The renin-angiotensin-aldosterone system (RAAS), is an old system with new fundamental roles in cancer biology which influences cell growth, migration, death, and metastasis. RAAS signaling enhances cell proliferation in malignancy directly and indirectly by affecting tumor cells and modulating angiogenesis. Cancer development may be influenced by the balance between the ACE/Ang II/AT1R and the ACE2/Ang 1-7/Mas receptor pathways. The interactions between Ang II/AT1R and Ang I/AT2R as well as Ang1-7/Mas and alamandine/MrgD receptors in the RAAS pathway can significantly impact the development of cancer. Ang I/AT2R, Ang1-7/Mas, and alamandine/MrgD interactions can have anticancer effects while Ang II/AT1R interactions can be involved in the development of cancer. Evidence suggests that inhibitors of the RAAS, which are conventionally used to treat cardiovascular diseases, may be beneficial in cancer therapies.Herein, we aim to provide a thorough description of the elements of RAAS and their molecular play in cancer. Alongside this, the role of RAAS components in sex-dependent cancers as well as GI cancers will be discussed with the hope of enlightening new venues for adjuvant cancer treatment.

Metabolic pathways enriched according to ERG status are associated with biochemical recurrence in Hispanic/Latino patients with prostate cancer

BACKGROUND

The role of ERG-status molecular subtyping in prognosis of prostate cancer (PCa) is still under debate. In this study, we identified differentially expressed genes (DEGs) according to ERG-status to explore their enriched pathways and implications in prognosis in Hispanic/Latino PCa patients.

METHODS

RNA from 78 Hispanic PCa tissues from radical prostatectomies (RP) were used for RNA-sequencing. ERG_high /ERG_low tumor groups were determined based on the 1.5-fold change median expression in non-tumor samples. DEGs with a False Discovery Rate (FDR) < 0.01 and a fold change >2 were identified between ERG_high and ERG_low tumors and submitted to enrichment analysis in MetaCore. Survival and association analyses were performed to evaluate biochemical recurrence (BCR)-free survival.

RESULTS

The identification of 150 DEGs between ERG_high and ERG_low tumors revealed clustering of most of the non-BCR cases (60%) into de ERG_high group and most of the BCR cases (60.8%) in ERG_low group. Kaplan-Meier survival curves showed a worst BCR-free survival for ERG_low patients, and a significant reduced risk of BCR was observed for ERG_high cases (OR = 0.29 (95%CI, 0.10-0.8)). Enrichment pathway analysis identified metabolic-related pathways, such as the renin-angiotensin system and angiotensin maturation system, the linoleic acid metabolism, and polyamines metabolism in these ERG groups.

CONCLUSIONS

ERG_low tumor cases were associated with poor BCR-free survival in our Hispanic/Latino patients, with metabolism-related pathways altered in the BCR progression.

IMPACT

Our findings suggest the need to dissect the role of diet, metabolism, and lifestyle as risk factors for more aggressive PCa subtypes.

The Hippo signalling pathway and its implications in human health and diseases

As an evolutionarily conserved signalling network, the Hippo pathway plays a crucial role in the regulation of numerous biological processes. Thus, substantial efforts have been made to understand the upstream signals that influence the activity of the Hippo pathway, as well as its physiological functions, such as cell proliferation and differentiation, organ growth, embryogenesis, and tissue regeneration/wound healing. However, dysregulation of the Hippo pathway can cause a variety of diseases, including cancer, eye diseases, cardiac diseases, pulmonary diseases, renal diseases, hepatic diseases, and immune dysfunction. Therefore, therapeutic strategies that target dysregulated Hippo components might be promising approaches for the treatment of a wide spectrum of diseases. Here, we review the key components and upstream signals of the Hippo pathway, as well as the critical physiological functions controlled by the Hippo pathway. Additionally, diseases associated with alterations in the Hippo pathway and potential therapies targeting Hippo components will be discussed.

Angiotensin-converting Enzyme Inhibitors and Angiotensin Receptor Blockers as Potential Therapeutic Options for Pancreatic Cancer

The renin-angiotensin system (RAS) has been reported to have a role in carcinogenesis, and therefore it may be of value as a potential therapeutic target in inhibiting tumor growth. It has been shown that inhibition of RAS via angiotensin I-converting enzyme inhibitors (ACEIs) and angiotensin II type-1 receptor (ARBs) inhibitors may have a protective effect against several malignancies. Here, we provide an overview of the potential value of the RAS pathway and targeting via ACE/ARB inhibitors in pancreatic cancer. Whilst the potential role of RAS as a target for the treatment of pancreatic cancer has been reported, the use of candesartan with gemcitabine failed to improve outcomes in pancreatic cancer. Another study of 1-3 years using ARB was found to reduce the risk of pancreatic cancer. In line with these trials, others have demonstrated that the ARBs in combination with gemcitabine might improve clinical outcomes in patients with advanced pancreatic cancer. Prospective trials are warranted to investigate this hypothesis.

Genomic pan-cancer classification using image-based deep learning

Accurate cancer type classification based on genetic mutation can significantly facilitate cancer-related diagnosis. However, existing methods usually use feature selection combined with simple classifiers to quantify key mutated genes, resulting in poor classification performance. To circumvent this problem, a novel image-based deep learning strategy is employed to distinguish different types of cancer. Unlike conventional methods, we first convert gene mutation data containing single nucleotide polymorphisms, insertions and deletions into a genetic mutation map, and then apply the deep learning networks to classify different cancer types based on the mutation map. We outline these methods and present results obtained in training VGG-16, Inception-v3, ResNet-50 and Inception-ResNet-v2 neural networks to classify 36 types of cancer from 9047 patient samples. Our approach achieves overall higher accuracy (over 95%) compared with other widely adopted classification methods. Furthermore, we demonstrate the application of a Guided Grad-CAM visualization to generate heatmaps and identify the top-ranked tumor-type-specific genes and pathways. Experimental results on prostate and breast cancer demonstrate our method can be applied to various types of cancer. Powered by the deep learning, this approach can potentially provide a new solution for pan-cancer classification and cancer driver gene discovery. The source code and datasets supporting the study is available at https://github.com/yetaoyu/Genomic-pan-cancer-classification.

YAP and endothelin-1 signaling: an emerging alliance in cancer

The rational making the G protein-coupled receptors (GPCR) the centerpiece of targeted therapies is fueled by the awareness that GPCR-initiated signaling acts as pivotal driver of the early stages of progression in a broad landscape of human malignancies. The endothelin-1 (ET-1) receptors (ET-1R), known as ET_A receptor (ET_AR) and ET_B receptor (ET_BR) that belong to the GPCR superfamily, affect both cancer initiation and progression in a variety of cancer types. By the cross-talking with multiple signaling pathways mainly through the scaffold protein β-arrestin1 (β-arr1), ET-1R axis cooperates with an array of molecular determinants, including transcription factors and co-factors, strongly affecting tumor cell fate and behavior. In this scenario, recent findings shed light on the interplay between ET-1 and the Hippo pathway. In ET_AR highly expressing tumors ET-1 axis induces the de-phosphorylation and nuclear accumulation of the Hippo pathway downstream effectors, the paralogous transcriptional cofactors Yes-associated protein (YAP) and Transcriptional coactivator with PDZ-binding motif (TAZ). Recent evidence have discovered that ET-1R/β-arr1 axis instigates a transcriptional interplay involving YAP and mutant p53 proteins, which share a common gene signature and cooperate in a oncogenic signaling network. Mechanistically, YAP and mutp53 are enrolled in nuclear complexes that turn on a highly selective YAP/mutp53-dependent transcriptional response. Notably, ET-1R blockade by the FDA approved dual ET-1 receptor antagonist macitentan interferes with ET-1R/YAP/mutp53 signaling interplay, through the simultaneous suppression of YAP and mutp53 functions, hampering metastasis and therapy resistance. Based on these evidences, we aim to review the recent findings linking the GPCR signaling, as for ET-1R, to YAP/TAZ signaling, underlining the clinical relevance of the blockade of such signaling network in the tumor and microenvironmental contexts. In particular, we debate the clinical implications regarding the use of dual ET-1R antagonists to blunt gain of function activity of mutant p53 proteins and thereby considering them as a potential therapeutic option for mutant p53 cancers. The identification of ET-1R/β-arr1-intertwined and bi-directional signaling pathways as targetable vulnerabilities, may open new therapeutic approaches able to disable the ET-1R-orchestrated YAP/mutp53 signaling network in both tumor and stromal cells and concurrently sensitizes to high-efficacy combined therapeutics.

Renin angiotensin system genes are biomarkers for personalized treatment of acute myeloid leukemia with Doxorubicin as well as etoposide

Despite the availability of various treatment protocols, response to therapy in patients with Acute Myeloid Leukemia (AML) remains largely unpredictable. Transcriptomic profiling studies have thus far revealed the presence of molecular subtypes of AML that are not accounted for by standard clinical parameters or by routinely used biomarkers. Such molecular subtypes of AML are predicted to vary in response to chemotherapy or targeted therapy. The Renin-Angiotensin System (RAS) is an important group of proteins that play a critical role in regulating blood pressure, vascular resistance and fluid/electrolyte balance. RAS pathway genes are also known to be present locally in tissues such as the bone marrow, where they play an important role in leukemic hematopoiesis. In this study, we asked if the RAS genes could be utilized to predict drug responses in patients with AML. We show that the combined in silico analysis of up to five RAS genes can reliably predict sensitivity to Doxorubicin as well as Etoposide in AML. The same genes could also predict sensitivity to Doxorubicin when tested in vitro. Additionally, gene set enrichment analysis revealed enrichment of TNF-alpha and type-I IFN response genes among sensitive, and TGF-beta and fibronectin related genes in resistant cancer cells. However, this does not seem to reflect an epithelial to mesenchymal transition per se. We also identified that RAS genes can stratify patients with AML into subtypes with distinct prognosis. Together, our results demonstrate that genes present in RAS are biomarkers for drug sensitivity and the prognostication of AML.

Development of a novel [18 F]fluorobenzyl derivative of the AT1 receptor antagonist Candesartan

Candesartan is a clinically approved angiotensin II type 1 receptor (AT₁ R)-blocker that selectively binds AT₁ Rs in high affinity. We report here the radiosynthesis and automation of the novel [¹⁸ F]fluorobenzyl derivative of Candesartan using the Sonogashira cross-coupling reaction. [¹⁸ F]Fluorobenzyl-Candesartan ([¹⁸ F]7) was developed from 4-[¹⁸ F]fluoroiodobenzene ([¹⁸ F]FIB) that was conjugated with alkyne-trityl-candesartan with the assistance of a Pd (PPh₃ )₄ /CuI catalyst followed by acid deprotection. The three-step two-reactor 2-HPLC purification process was automated resulting in >90% pure [¹⁸ F]7 in a RCY of 4.6 ± 1.1% (decay corrected from EOB) and molar activities of 1,406-5,513 GBq/mmol. [¹⁸ F]FIB was reproducibly obtained by direct radiofluorination of the mono-iodinated triphenylsulfonium salt in the presence of K222/K₂ CO₃ in an ~30% yield (decay-corrected). [¹⁸ F]7 was stable (>97%) up to 4 h in solution and up to 1 h in rat plasma at 37°C. However, the use of Sonogashira cross-coupling reaction to produce [¹⁸ F]7 in high yields and molar activities was found to be challenging for routine use in radiochemistry labs.

Synthesis and Evaluation of [18F]FEtLos and [18F]AMBF3Los as Novel 18F-Labelled Losartan Derivatives for Molecular Imaging of Angiotensin II Type 1 Receptors

Losartan is widely used in clinics to treat cardiovascular related diseases by selectively blocking the angiotensin II type 1 receptors (AT₁Rs), which regulate the renin-angiotensin system (RAS). Therefore, monitoring the physiological and pathological biodistribution of AT₁R using positron emission tomography (PET) might be a valuable tool to assess the functionality of RAS. Herein, we describe the synthesis and characterization of two novel losartan derivatives PET tracers, [¹⁸F]fluoroethyl-losartan ([¹⁸F]FEtLos) and [¹⁸F]ammoniomethyltrifluoroborate-losartan ([¹⁸F]AMBF₃Los). [¹⁸F]FEtLos was radiolabeled by ¹⁸F-fluoroalkylation of losartan potassium using the prosthetic group 2-[¹⁸F]fluoroethyl tosylate; whereas [¹⁸F]AMBF₃Los was prepared following an one-step ¹⁸F-¹⁹F isotopic exchange reaction, in an overall yield of 2.7 ± 0.9% and 11 ± 4%, respectively, with high radiochemical purity (>95%). Binding competition assays in AT₁R-expressing membranes showed that AMBF₃Los presented an almost equivalent binding affinity (K_i 7.9 nM) as the cold reference Losartan (K_i 1.5 nM), unlike FEtLos (K_i 2000 nM). In vitro and in vivo assays showed that [¹⁸F]AMBF₃Los displayed a good binding affinity for AT₁R-overexpressing CHO cells and was able to specifically bind to renal AT₁R. Hence, our data demonstrate [¹⁸F]AMBF₃Los as a new tool for PET imaging of AT₁R with possible applications for the diagnosis of cardiovascular, inflammatory and cancer diseases.

Angiotensin receptor autoantibodies as exposures that modify disease progression: Cross sectional, longitudinal and in vitro studies of prostate cancer

Circulating angiotensin type I receptor (AT1R) agonistic autoantibodies (AT1RaAbs) that bind and chronically activate the receptor have been associated with a number of diseases suggesting that while the autoantibodies are not necessarily causative they may promote disease progression. The prostate has a local renin angiotensin system. The current study examines associations between AT1RaAbs and prostate cancer (PCA), disease-free survival (DFS), overall survival (OS) and AT1RaAb effects on PCA cell phenotype. In a cross-sectional set of serum obtained from 151 men diagnosed with PCA, nonmalignant prostate disease or no disease, higher serum AT1RaAb levels were associated with PCA and non-organ confined PCA. The odds ratio for PCA was 6.3 (95% confidence interval 2.2 to 18) for a positive 1:1600 titer and 18 (95% confidence interval 6.9 to 45) at AT1RaAb levels > 1.04 μg/ml, (p < 0.0001). In a longitudinal set of pre-diagnosis samples from 109 men, DFS hazard ratios of 2.2 (95% confidence interval 1.4 to 3.5) and 1.6 (95% confidence interval 1.0 to 2.5) for most proximal to diagnosis and most distal to diagnosis samples, respectively, were found for high versus low AT1RaAb groups. Hazard ratios for OS in most proximal and distal samples were 2.4 (95% confidence interval 1.6 to 3.6) and 1.8 (95% confidence interval 1.1 to 2.8), respectively. Accelerated failure modeling of survival indicated that a 1 μg/ml increase in AT1RaAb levels was associated with a reduction of DFS and OS by 20% at the most proximal time point and by 15% at the most distal time points. Adjusting for age, did not affect the association with DFS in proximal samples but changed distal time point DFS and OS to a 10% decrease for every 1 μg/ml increase in AT1RaAb. Additional adjustments for body mass index, systolic blood pressure and prostate-specific antigen did not appreciably alter these associations. AT1RaAb treatment of PC3, DU145, and LNCaP cells significantly increased the maximal growth rate approximately 2-fold and invasiveness approximately 3-fold. Conclusions: These observations provide evidence supporting AT1RaAbs as exposures that may modify prostate cancer progression and indicate they may be predictive markers for risk stratification.

Association of ACE I/D and AGTR1 A1166C Gene Polymorphisms and Risk of Uterine Leiomyoma: A Case-Control Study

Objective:

Uterine leiomyoma (UL) can be considered as the most common benign gynecological tumors of the smooth muscle cells in the myometrium. They are likely to be associated with infertility and recurrent abortion as well as obstructed labor and post-partum hemorrhage. Moreover, altered vascular-related genes can be linked to developing leiomyoma. Polymorphisms of the angiotensin-converting enzyme (ACE) gene are associated with some vascular diseases. The present study was carried out to investigate the association of ACE I/D and AGTR1A1166C gene polymorphisms and the risk of uterine leiomyoma in a sample of Iranian population.

Methods:

The study was carried out on a total of 413 women divided into 202 patients with diagnosed uterine leiomyomas and a control group of 211. Genotyping was performed using the PCR or PCR-RFLP methods.

Results:

The ID and DD genotypes of ACE I/D polymorphism were associated with 2 and 2.9 fold higher risk of UL compared to II genotype (OR, 2 [95% CI, 1.3 to 3.2]; P = 0.004 and OR, 2.9 [95% CI, 1.6 to 5]; P = 0.0002). The frequencies of ACE D alleles were 53.7% in women with UL and 40.3% in controls, which were observed to be statistically different (P < 0.0001). The alleles and genotypes of AGTR1 A1166C polymorphism were not different between UL and control women (P=0.9).

Conclusion:

The ACE ID and DD genotypes were associated with a higher risk of UL. No relationship was found between AGTR1A1166C polymorphism and UL.

Therapeutic Targeting of Cancer Stem Cells via Modulation of the Renin-Angiotensin System

Cancer stem cells (CSCs) are proposed to be the cells that initiate tumorigenesis and maintain tumor development due to their self-renewal and multipotency properties. CSCs have been identified in many cancer types and are thought to be responsible for treatment resistance, metastasis, and recurrence. As such, targeting CSCs specifically should result in durable cancer treatment. One potential option for targeting CSCs is by manipulation of the renin-angiotensin system (RAS) and pathways that converge on the RAS with numerous inexpensive medications currently in common clinical use. In addition to its crucial role in cardiovascular and body fluid homeostasis, the RAS is vital for stem cell maintenance and differentiation and plays a role in tumorigenesis and cancer prevention, suggesting that these roles may converge and result in modulation of CSC function by the RAS. In support of this, components of the RAS have been shown to be expressed in many cancer types and have been more recently localized to the CSCs in some tumors. Given these roles of the RAS in tumor development, clinical trials using RAS inhibitors either singly or in combination with other therapies are underway in different cancer types. This review outlines the roles of the RAS, with respect to CSCs, and suggests that the presence of components of the RAS in CSCs could offer an avenue for therapeutic targeting using RAS modulators. Due to the nature of the RAS and its crosstalk with numerous other signaling pathways, a systems approach using traditional RAS inhibitors in combination with inhibitors of bypass loops of the RAS and other signaling pathways that converge on the RAS may offer a novel therapeutic approach to cancer treatment.

(Pro)renin Receptor Expression Increases throughout the Colorectal Adenoma-Adenocarcinoma Sequence and It Is Associated with Worse Colorectal Cancer Prognosis

(Pro)renin receptor (PRR) is a protein that takes part in several signaling pathways such as Renin Angiotensin System and Wnt signalling. Its biological role has recently been related to cancer progression and in this study, we investigated its relevance in colorectal cancer (CRC). To that end, we analysed the immunohistochemical expression of PRR in adenomatous polyps and CRCs from the same patients (n = 42), and in primary tumours and nodal and liver metastases from advanced CRC patients (n = 294). In addition, the soluble fraction of PRR was measured by ELISA in plasma samples from 161 CRC patients. The results showed that PRR expression was gradually augmented along the uninvolved mucosa-adenoma-adenocarcinoma sequence. Besides, the stronger expression of PRR in primary tumours was markedly associated with local tumour extent and the onset of metastases. Moreover, PRR expression in both primary and distant metastases was associated with worse 5- and 10-year survival of CRC patients. Plasmatic PRR levels did not change with respect to controls and were not associated with CRC aggressiveness. These results suggest a key role of PRR in the development and progression of CRC and a potential use of this protein as a new prognostic biomarker and/or therapeutic target for this disease.

GPCR-Hippo Signaling in Cancer

The Hippo signaling pathway is involved in tissue size regulation and tumorigenesis. Genetic deletion or aberrant expression of some Hippo pathway genes lead to enhanced cell proliferation, tumorigenesis, and cancer metastasis. Recently, multiple studies have identified a wide range of upstream regulators of the Hippo pathway, including mechanical cues and ligands of G protein-coupled receptors (GPCRs). Through the activation related G proteins and possibly rearrangements of actin cytoskeleton, GPCR signaling can potently modulate the phosphorylation states and activity of YAP and TAZ, two homologous oncogenic transcriptional co-activators, and major effectors of the Hippo pathway. Herein, we summarize the network, regulation, and functions of GPCR-Hippo signaling, and we will also discuss potential anti-cancer therapies targeting GPCR-YAP signaling.

Chemopreventive effects of angiotensin II receptor type 2 agonist on prostate carcinogenesis by the down-regulation of the androgen receptor

We recently reported that angiotensin II receptor blockers (ARBs) have chemopreventive and chemotherapeutic potential against prostate cancer via the reduction of androgen receptor (AR) expression. In this study, we investigated the effects of the angiotensin II receptor type 2 (AT2R) agonist Compound 21 (C21), which is expected to play similar roles to an ARB, on prostate carcinogenesis using the transgenic rat for adenocarcinoma of prostate (TRAP) model previously established in our laboratory. In vitro analyses of the cell growth, Western blotting and reporter gene assays were performed using LNCaP cells. TRAP rats at 6 weeks of age were randomly divided into 3 groups of 12 animals each and treated with C21 at 1 or 2 mg/kg/day in drinking water for 12 weeks. C21 reduced the proliferation activity of prostate cancer cells and down-regulated the PSA promoter activity and the AR protein expression. We discovered that C21 inhibited the progression of prostate carcinogenesis in TRAP rats and decreased the incidence of adenocarcinoma in the lateral prostate. A significant increase in the apoptotic index with activation of caspase 3 and 7 were observed by immunohistochemistry and Western blotting analyses. C21 also down-regulated the expression of AR significantly in TRAP rat prostate. C21 decreased the expression of AR and reduced the proliferation activity effectively in prostate cancer cells and TRAP rat prostate. These findings suggest that AT2R agonist may be a candidate novel chemopreventive agent against human prostate cancer.

Effects of testosterone and 17β‑estradiol on angiotensin‑induced changes in tyrosine kinase activity in the androgen‑independent human prostate cancer cell line, DU145

Angiotensin II (AngII), the main peptide of the renin‑angiotensin system (RAS), is involved in the proliferation of different types of cells, normal and pathological as well. The protein tyrosine kinases (PTKs) play an important role in the growth, differentiation and apoptosis of cells. AngII action depends on the hormonal milieu of the cell, and on sex steroid influence. Angiotensin 1‑7 (Ang1‑7), metabolite of AngII, shows opposite action to AngII in cells. The present study aimed to examine the influence of 17β‑estradiol and testosterone on AngII and Ang1‑7 action on PTK activity in androgen‑independent humane prostate cancer cell line DU145. Cell cultures of human prostate cancer DU145 cells were used as a source of PTKs. Cultures were exposed to different concentrations of AngII (5x10‑11 to 5x10‑9 M). The incubation with hormones lasted 15 min to limit the genomic effects of steroids. In the phosphorylation reaction, we used γ32P‑ATP as a donor of phosphate and a synthetic peptide, Poly(Glu, Tyr) (4:1), as a substrate. The specific activities of PTKs were defined as pmol of 32P incorporated into 1 mg of exogenous Poly(Glu, Tyr) per minute (pmol/mg/min). Our findings suggest that testosterone and 17β‑estradiol may change the effects of angiotensins in a rapid non‑genomic way, probably via membrane‑located receptors. The most significant change was caused by testosterone, whose effect was most significant on changes caused by Ang1‑7. AngII‑induced changes in phosphorylation appeared to be insensitive to the presence of testosterone, but were modified by 17β‑estradiol.

Alterations in Gene Expression of Components of the Renin-Angiotensin System and Its Related Enzymes in Lung Cancer

Objectives

The study assessed the existence and significance of associations between the expression of fifteen renin-angiotensin system component genes and lung adenocarcinoma.

Materials and Methods

NCBI's built-in statistical tool, GEO2R, was used to calculate Student's t-tests for the associations found in a DNA expression study of adenocarcinoma and matched healthy lung tissue samples. The raw data was processed with GeneSpring™ and then used to generate figures with and without Sidak's multiple comparison correction.

Results

Ten genes were found to be significantly associated with adenocarcinoma. Seven of these associations remained statistically significant after correction for multiple comparisons. Notably, AGTR2, which encodes the AT₂ angiotensin II receptor subtype, was significantly underexpressed in adenocarcinoma tissue (p < 0.01). AGTR1, ACE, ENPEP, MME, and PRCP, which encode the AT₁ angiotensin II receptor, angiotensin-converting enzyme, aminopeptidase N, neprilysin, and prolylcarboxypeptidase, respectively, were also underexpressed. AGT, which encodes angiotensinogen, the angiotensin peptide precursor, was overexpressed in adenocarcinoma tissue.

Conclusion

The results suggest an association between the expression of the genes for renin-angiotensin system-related proteins and adenocarcinoma. While further research is necessary to conclusively demonstrate a link between the renin-angiotensin system and lung cancers, the results suggest that the renin-angiotensin system plays a role in the pathology of adenocarcinoma.

The ACE2/Angiotensin-(1-7)/Mas Receptor Axis: Pleiotropic Roles in Cancer

Cancer remains one of the most common causes of death and disability and represents a major economic burden in industrialized nations. The renin-angiotensin system (RAS) has been well-recognized as one of the most important regulators of both normal and pathological physiological processes in the brain, kidney, heart, and blood vessels. The activation of the angiotensin-converting enzyme 2/angiotensin-(1–7)/mitochondrial assembly receptor [ACE2/Ang-(1–7)/MasR] axis, which is one component of the RAS, has recently been identified as a critical component of pulmonary systems, gastric mucosa, and cancer. However, the ability of the ACE2/Ang-(1–7)/MasR axis to suppress or promote cancer has not been fully elucidated. In this review, we focus on recent experimental and clinical studies investigating the basic properties, roles, and mechanisms of ACE2, Ang-(1–7), and the MasR, as well as the axis pathway, to provide insights into possible therapeutic strategies for treating cancer that target the ACE2/Ang-(1–7)/MasR axis.

Regulation of the prorenin - angiotensin system by oxygen and miRNAs; parallels between placentation and tumour development?

Tissue renin-angiotensin systems (RASs) are involved in tissue growth and development as they are important regulators of angiogenesis, cell proliferation and migration. The placental RAS is most highly expressed in early gestation, at a time when the oxygen tension within the conceptus is reduced, and plays a key role in placental growth and development. Similar to the placenta, tumour development relies on proliferation, angiogenesis and invasion in order to grow and metastasize. The RAS is known to be upregulated in a variety of solid tumours, including ovarian, endometrial, cervical, breast and prostate. This review explores the roles of oxygen and microRNAs in regulating the normal expression of the placental RAS, providing insight into regulation of its development as well as the development of disease states in which the RAS is overexpressed. We propose that the placental RAS is downregulated by microRNAs that are suppressed during the physiologically normal 'hypoxic' phase of early placentation. Suppression of these miRNAs allows the placental RAS to stimulate placental growth and angiogenesis. We propose that similar mechanisms may be at play in solid tumours, which are characterised by hypoxia.

Enhanced mesenteric arterial responsiveness to angiotensin II is androgen receptor-dependent in prenatally protein-restricted adult female rat offspring

Gestational protein restriction results in intrauterine growth restriction and hypertension in adult female growth-restricted rats. Enhanced vascular responsiveness to angiotensin II is observed, and blockade of the renin-angiotensin system abolishes hypertension in adult growth-restricted rats, suggesting that the renin-angiotensin system contributes to intrauterine growth restriction-induced hypertension. Moreover, growth-restricted adult rats have higher plasma testosterone levels, and antiandrogen treatment abolishes hypertension, indicating an important role for testosterone. We hypothesized that androgens may play a pivotal role in the enhanced responsiveness to Ang II and hypertension. Female offspring of pregnant rats fed 20% protein (control) or 6% protein diet (protein restricted), at 6 mo of age, were studied. Plasma testosterone and mean arterial pressure in protein-restricted offspring were significantly higher compared to controls. Flutamide treatment (10 mg/kg/day subcutaneously for 10 days) reduced mean arterial pressure in protein-restricted offspring but was without significant effect in controls. Vascular Agtr1/Agtr2 ratio was significantly higher in protein-restricted offspring, an effect that was reversed by flutamide. Flutamide treatment did not have any effect on Agtr1/Agtr2 ratio in controls. Enhanced contractile response to angiotensin II in mesenteric arteries was observed in protein-restricted offspring compared with control. Flutamide treatment reversed the enhanced contractile response to angiotensin II in protein-restricted offspring without significant effect in controls. Vascular reactivity to phenylephrine was similar between the control and protein-restricted offspring with and without flutamide treatment, suggesting that enhanced contractile response and flutamide's reversal effect is specific to angiotensin II. These results suggest that prenatally protein-restricted rats exhibit an enhanced responsiveness to angiotensin II that is testosterone-dependent.

Enalapril and ASS inhibit tumor growth in a transgenic mouse model of islet cell tumors

Accumulating evidence suggests a role for angiotensin-converting enzymes involving the angiotensin II-receptor 1 (AT1-R) and the cyclooxygenase pathway in carcinogenesis. The effects of ASS and enalapril were assessed in vitro and in a transgenic mouse model of pancreatic neuroendocrine neoplasms (pNENs). The effects of enalapril and ASS on proliferation and expression of the AGTR1A and its target gene vascular endothelial growth factor (Vegfa) were assessed in the neuroendocrine cell line BON1. Rip1-Tag2 mice were treated daily with either 0.6 mg/kg bodyweight of enalapril i.p., 20 mg/kg bodyweight of ASS i.p., or a vehicle in a prevention (weeks 5-12) and a survival group (week 5 till death). Tumor surface, weight of pancreatic glands, immunostaining for AT1-R and nuclear factor kappa beta (NFKB), and mice survival were analyzed. In addition, sections from human specimens of 20 insulinomas, ten gastrinomas, and 12 non-functional pNENs were evaluated for AT1-R and NFKB (NFKB1) expression and grouped according to the current WHO classification. Proliferation was significantly inhibited by enalapril and ASS in BON1 cells, with the combination being the most effective. Treatment with enalapril and ASS led to significant downregulation of known target genes Vegf and Rela at RNA level. Tumor growth was significantly inhibited by enalapril and ASS in the prevention group displayed by a reduction of tumor size (84%/67%) and number (30%/45%). Furthermore, daily treatment with enalapril and ASS prolonged the overall median survival compared with vehicle-treated Rip1-Tag2 (107 days) mice by 9 and 17 days (P=0.016 and P=0.013). The AT1-R and the inflammatory transcription factor NFKB were abolished completely upon enalapril and ASS treatment. AT1-R and NFKB expressions were observed in 80% of human pNENs. Enalapril and ASS may provide an approach for chemoprevention and treatment of pNENs.

Effect of an angiotensin II type 1 receptor blocker on caveolin-1 expression in prostate cancer cells

INTRODUCTION

Caveolin-1, the major structural protein of caveolae, interacts directly with the AT1 receptor. The biological functions of caveolin-1 in cancer are compound, multifaceted, and depend on cell type, tumour grade and cancer stage. The AT1-R-caveolin complex in caveolae may coordinate angiotensin II (Ang II) induced signalling. The aim of this study was to determine the effect of the angiotensin II receptor type 1 blocker candesartan on caveolin expression in human metastatic prostate adenocarcinoma cells PC-3.

MATERIAL AND METHODS

WST-1 and BrdU assays were used as indicators of cell viability and proliferation after angiotensin II and/or candesartan stimulation. Real-time RT-PCR and western blot were used to study the effect of Ang II and/or candesartan on the expression of Cav-1 and AT1-R in PC-3 cells.

RESULTS

We found that the expression of caveolin-1 mRNA in the PC-3 cells treated with CV was significantly decreased in comparison with the control (2.9 ±0.17, 4.7 ±0.6, p < 0.05), whereas a higher caveolin-1 mRNA expression was observed in those after Ang II treatment (6.0 ±0.43, 4.7 ±0.6, p < 0.05). Protein analysis indicate that the expression of caveolin-1 protein in the PC-3 cells treated with candesartan was significantly decreased when compared with the control (0.69 ±0.05, 1.6 ±0.12, p < 0.05), whereas higher caveolin-1 protein expression was observed after Ang II treatment (2.5 ±0.20, 1.6 ±0.12, p < 0.05).

CONCLUSIONS

These results provide new information on the action of candesartan and may improve the knowledge about AT1 receptor inhibitors, which can be potentially useful in prostate cancer therapy.

Expression and role of the angiotensin II AT2 receptor in human prostate tissue: in search of a new therapeutic option for prostate cancer

BACKGROUND

Evidence shows that angiotensin II type 1 receptor (AT1R) blockers may be associated with improved outcome in prostate cancer patients. It has been proposed that part of this effect could be due to angiotensin II type 2 receptor (AT2R) activation, the only active angiotensin II receptor in this situation. This study aimed to characterize the localization and expression of AT2R in prostate tissues and to assess its role on cell morphology and number in prostatic epithelial cells in primary culture.

METHODS

AT2R and its AT2R-interacting protein (ATIP) expression were assessed on non-tumoral and tumoral human prostate using tissue microarray immunohistochemistry, binding assay, and Western blotting. AT2R effect on cell number was measured in primary cultures of epithelial cells from non-tumoral human prostate.

RESULTS

AT2R was localized at the level of the acinar epithelial layer and its expression decreased in cancers with a Gleason score 6 or higher. In contrast, ATIP expression increased with cancer progression. Treatment of primary cell cultures from non-tumoral prostate tissues with C21/M024, a selective AT2R agonist, alone or in co-incubation with losartan, an AT1R antagonist, significantly decreased cell number compared to untreated cells.

CONCLUSIONS

AT2R and ATIP are present in non-tumoral human prostate tissues and differentially regulated according to Gleason score. The decrease in non-tumoral prostate cell number upon selective AT2R stimulation suggests that AT2R may have a protective role against prostate cancer development. Treatment with a selective AT2R agonist could represent a new approach for prostate cancer prevention or for patients on active surveillance.

The renin angiotensin system regulates Kupffer cells in colorectal liver metastases

Blockade of the renin angiotensin system (RAS) can inhibit tumor growth and this may be mediated via undefined immunomodulatory actions. This study investigated the effects of RAS blockade on liver macrophages (Kupffer cells; KCs) in an orthotopic murine model of colorectal cancer (CRC) liver metastases. Here we showed that pharmacological targeting of the RAS [ANG II (31.25 µg/kg/h i.p.), ANG-(1-7) (24 µg/kg/h i.p.) or the ACE inhibitor; captopril (750 mg/kg/d i.p.)] altered endogenous KC numbers in the tumor-bearing liver throughout metastatic growth. Captopril, and to a lesser extent ANG-(1-7), increased KC numbers in the liver but not tumor. KCs were found to express the key RAS components: ACE and AT1R. Treatment with captopril and ANG II increased the number of AT1R-expressing KCs, although total KC numbers were not affected by ANG II. Captopril (0.1 µM) also increased macrophage invasion in vitro. Additionally, captopril was administered with KC depletion before tumor induction (day 0) or at established metastatic growth (day 18) using gadolinium chloride (GdCl 3; 20 mg/kg). Livers were collected at day 21 and quantitative stereology used as a measure of tumor burden. Captopril reduced growth of CRC liver metastases. However, when captopril was combined with early KC depletion (day 0) tumor growth was significantly increased compared with captopril alone. In contrast, late KC depletion (day 18) failed to influence the anti-tumor effects of captopril. The result of these studies suggests that manipulation of the RAS can alter KC numbers and may subsequently influence progression of CRC liver metastases.

Angiotensin-(1-7) reduces proliferation and angiogenesis of human prostate cancer xenografts with a decrease in angiogenic factors and an increase in sFlt-1

BACKGROUND

Prostate cancer is the most frequently diagnosed malignancy and the second-leading cause of cancer death in men. The purpose of this study was to determine the anti-proliferative and anti-angiogenic efficacy of angiotensin-(1-7) [Ang-(1-7)], an endogenous peptide hormone, in human prostate cancer xenografts.

METHODS

Human LNCaP prostate cancer cells were injected into the flank of athymic mice and tumors were treated with Ang-(1-7) for 54 days. Tumor growth and angiogenesis were determined by immunohistochemistry and western blot hybridization.

RESULTS

Ang-(1-7) markedly reduced the volume and wet weight of LNCaP xenograft tumors. Histological analysis of tumor sections from saline-treated mice showed increased Ki67 immunoreactivity and enhanced phosphorylation of the MAP kinases ERK1/2 compared to tumors from Ang-(1-7)-treated mice, suggesting that the heptapeptide reduces cell proliferation. Intratumoral vessel density was decreased in Ang-(1-7)-treated mice with an associated reduction in vascular endothelial growth factor (VEGF) and placental growth factor (PlGF), suggesting that the heptapeptide attenuates vascularization by reducing angiogenic factors. Ang-(1-7) administration markedly increased the soluble fraction of VEGF receptor 1 (sFlt-1), with a concomitant reduction in VEGF receptors 1 and 2. sFlt-1 serves as a decoy receptor that traps VEGF and PlGF, making the ligands unavailable to membrane-bound VEGF receptors and preventing activation of pro-angiogenic signaling.

CONCLUSIONS

The decrease in PlGF and VEGF coupled with the increase in sFlt-1 suggests that Ang-(1-7) may serve as a novel anti-angiogenic therapy for prostate cancer. Further, the pleiotropic mechanisms of action by Ang-(1-7) may limit angiogenic resistance that occurs with VEGF inhibitors or receptor blockers.

Therapeutic targeting of angiotensin II receptor type 1 to regulate androgen receptor in prostate cancer

BACKGROUND

With the limited strategies for curative treatment of castration-resistant prostate cancer (CRPC), public interest has focused on the potential prevention of prostate cancer. Recent studies have demonstrated that an angiotensin II receptor blocker (ARB) has the potential to decrease serum prostate-specific antigen (PSA) level and improve performance status in CRPC patients. These facts prompted us to investigate the direct effects of ARBs on prostate cancer growth and progression.

METHODS

Transgenic rat for adenocarcinoma of prostate (TRAP) model established in our laboratory was used. TRAP rats of 3 weeks of age received ARB (telmisartan or candesartan) at the concentration of 2 or 10 mg/kg/day in drinking water for 12 weeks. In vitro analyses for cell growth, ubiquitylation or reporter gene assay were performed using LNCaP cells.

RESULTS

We found that both telmisartan and candesartan attenuated prostate carcinogenesis in TRAP rats by augmentation of apoptosis resulting from activation of caspases, inactivation of p38 MAPK and down-regulation of the androgen receptor (AR). Further, microarray analysis demonstrated up-regulation of estrogen receptor β (ERβ) by ARB treatment. In both parental and androgen-independent LNCaP cells, ARB inhibited both cell growth and AR-mediated transcriptional activity. ARB also exerted a mild additional effect on AR-mediated transcriptional activation by the ERβ up-regulation. An intervention study revealed that PSA progression was prolonged in prostate cancer patients given an ARB compared with placebo control.

CONCLUSION

These data provide a new concept that ARBs are promising potential chemopreventive and chemotherapeutic agents for prostate cancer.

Similarities and differences between effects of angiotensin III and angiotensin II on human prostate cancer cell migration and proliferation

Proliferation plays a critical role in tumor growth when cell migration is essential to invasion. The effect of Ang III and Ang II was evaluated on these important processes. Changes in the migration potential of prostate cancer cells were investigated using Wound Healing Test and a Transwell Migration Chamber with a 3 μm pore size. Cell proliferation was measured with a BrdU Assay and Countess Automated Cell Counter, thus determining the influence of angiotensins on hormone-dependent (LNCaP) and hormone-independent (DU-145) human prostate cancer lines. The influence of Ang III and Ang II on classic receptors may be inhibited by Losartan or PD123319. Test peptide modulation of the AT1 and AT2 receptors was examined by Western Blot and fluorescent immunocytochemistry. The results indicate that Ang III promotes the migration of both LNCaP and DU-145 lines, whereas Ang II stimulates this process only in androgen-independent cells. Both angiotensin peptides can induce prostate cancer cell proliferation in a time- and dose-dependent manner. The obtained results show that Ang III and Ang II can modify the expression of classic receptors, particularly AT2. These results suggest that the investigated peptide can modulate cell migration and proliferation in prostate cancer cells. Angiotensins probably have a greater influence on proliferation in the early-stage prostate cancer model than hormone-independent cell lines. Assume also that Ang II can enhance the migration tendency aggressive prostate cancer cells, while Ang III does so more effective in non-metastatic cells.

Angiotensin-converting enzyme insertion/deletion polymorphism and the risk of prostate cancer in the Han population of China

As a main effector in the renin-angiotensin system, the angiotensin II plays a critical role in cell proliferation and angiogenesis. The change between angiotensin II and its precursor is conducted by the angiotensin-converting enzyme. The association between angiotensin-converting enzyme insertion/deletion polymorphism and the activity of angiotensin-converting enzyme was testified. Furthermore, previous researches proved the association between angiotensin-converting enzyme activity and the risk of prostate cancer. Therefore, we conducted a case-control study in the Han population of China to elaborate the relation between the angiotensin-converting enzyme insertion/deletion polymorphism and prostate cancer. DNA was extracted from blood samples collected from 189 pathologically diagnosed prostate cancer patients and 290 cancer-free subjects. The angiotensin-converting enzyme insertion/deletion genotype was determined by polymerase chain reaction analysis. Stratified analyses on age (<71 or ≥ 71), cancer stage (localized or advanced), Gleason score (<7 or ≥ 7) and PSA level (<20 ng/ml or ≥ 20 ng/ml) were performed. We found the II genotype (OR = 0.304 95%CI (0.180,0.515), P < 0.001) and I allele (OR = 0.547 95%CI(0.421,0.711), P < 0.001) were associated with a decreased risk of prostate cancer compared with the DD genotype and D allele. The DD genotype was related to patients with aggressive stage of prostate cancer (OR = 2.214 95%CI(1.169, 4.194), P = 0.014) and patients diagnosed of prostate cancer at a relatively early age (OR = 0.513 95%CI(0.272, 0.965), P = 0.037). The results of our experiment supported the hypothesis that the angiotensin-converting enzyme insertion/deletion polymorphism, a potential risk factor in carcinogenesis, played an important role in the Han population of China.

Regulation of androgen receptor expression through angiotensin II type 1 receptor in prostate cancer cells

BACKGROUND

Although the local renin-angiotensin system (RAS) of the prostate gland is related to cell proliferation and angiogenesis, the detailed mechanism remains unclear. We examined the effects of the angiotensin II type 1 receptor (AT1R) on androgen receptor (AR) expression in prostate cancer cells.

METHODS

AR modulation by AT1R was examined by Western blot analysis, luciferase assay, and Immunocytochemical staining. The influence of AR expression by angiotensin II (Ang-II) and AT1R inhibition using siRNA was determined. Furthermore, using angiotensinogen or AT1R knockout (KO) mice, we performed quantitative real-time PCR to investigate the expression of AR.

RESULTS

Ang-II induced cell proliferation with enhancement of AR, prostate specific antigen (PSA), NF-κB, and c-myc, and the activity of AR and PSA promoter. Cell proliferation of LNCaP transfected with AT1R siRNA was decreased by 75% at 7 days by inhibition of AR, PSA, NF-κB, and c-myc. Immunocytochemical staining confirmed the suppression of AR translocation into the nucleus in AT1R siRNA cells. AT1R KO mice showed a decrease in AR expression in the prostate gland. We also found that the expression level of AT1R could modulate the transcriptional level of AR by affecting NF-κB and c-myc expression.

CONCLUSIONS

Knocking down of the AT1R protein resulted in significant inhibition of cell growth, associated with a marked decrease of AR protein. These results indicate that inhibition of AT1R has the potential to influence AR expression in prostate cells, and is anticipated to contribute to the development of novel therapeutic agents for prostate cancer.

The renin-angiotensin system and cancer: old dog, new tricks

For cancers to develop, sustain and spread, the appropriation of key homeostatic physiological systems that influence cell growth, migration and death, as well as inflammation and the expansion of vascular networks are required. There is accumulating molecular and in vivo evidence to indicate that the expression and actions of the renin-angiotensin system (RAS) influence malignancy and also predict that RAS inhibitors, which are currently used to treat hypertension and cardiovascular disease, might augment cancer therapies. To appreciate this potential hegemony of the RAS in cancer, an expanded comprehension of the cellular actions of this system is needed, as well as a greater focus on translational and in vivo research.

Angiotensin II up-regulates PAX2 oncogene expression and activity in prostate cancer via the angiotensin II type I receptor

BACKGROUND

Paired homeobox 2 gene (PAX2) is a transcriptional regulator, aberrantly expressed in prostate cancer cells and its down-regulation promotes cell death in these cells. The molecular mechanisms of tumor progression by PAX2 over-expression are still unclear. However, it has been reported that angiotensin-II (A-II) induces cell growth in prostate cancer via A-II type 1 receptor (AT1R) and is mediated by the phosphorylation of mitogen activated protein kinase (MAPK) as well as signal transducer and activator of transcription 3 (STAT3).

METHODS

Here we have demonstrated that A-II up-regulates PAX2 expression in prostate epithelial cells and prostate cancer cell lines resulting in increased cell growth. Furthermore, AT1R receptor antagonist losartan was shown to inhibit A-II induced PAX2 expression in prostate cancer. Moreover, analysis using pharmacological inhibitors against MEK1/2, ERK1/2, JAK-II, and phospho-STAT3 demonstrated that AT1R-mediated stimulatory effect of A-II on PAX2 expression was regulated in part by the phosphorylation of ERK1/2, JAK II, and STAT3 pathways. In addition, we have showed that down-regulation of PAX2 by an AT1R antagonist as well as JAK-II and STAT3 inhibitors suppress prostate cancer cell growth.

RESULTS

Collectively, these findings show for the first time that the renin-angiotensin system (RAS) may promote prostate tumorigenesis via up-regulation of PAX2 expression.

CONCLUSIONS

Therefore, PAX2 may be a novel therapeutic target for the treatment of carcinomas such as prostate cancer via the down-regulation of its expression by targeting the AT1R signaling pathways.

Role of the renin-angiotensin system in prostate cancer

Prostate cancer is highly prevalent in Western society, and its early stages can be controlled by androgen ablation therapy. However, the cancer eventually regresses to an androgen-independent state for which there is no effective treatment. The renin-angiotensin system (RAS), in particular the octapeptide angiotensin II, is now recognised to have important effects on growth factor signalling and cell growth in addition to its well known actions on blood pressure, fluid homeostasis and electrolyte balance. All components of the RAS have been recently identified in the prostate, consistent with the expression of a local RAS system in this tissue. This review focuses on the role of the RAS in the prostate, and the possibility that this pathway may be a potential therapeutic target for the treatment of prostate cancer and other prostatic diseases.

Angiotensin inhibition and malignancies: a review

After an early report that patients treated with angiotensin-converting enzyme (ACE) inhibitors had a lower than expected incidence of cancers, there was a large number of publications investigating the possible pathophysiological mechanism mediating this effect, as well as population studies comparing the incidence of cancers in patients treated with agents inhibiting the renin-angiotensin system with their incidence in the general population. Several mechanisms are proposed to explain a potential anti-tumour activity of such agents in vitro in experimental animal models. However, the population studies are mostly inconclusive, although they do suggest a possible interaction between ACE genotypes and susceptibility to altered behaviour of certain tumours.

Evaluation of role of angiotensin III and aminopeptidases in prostate cancer cells

BACKGROUND

The aim of this study was to perform a comprehensive evaluation of angiotensin III (Ang-III) and related converting enzymes, aminopeptidase A (APA) and N (APN), in prostate cancer.

METHODS

We investigated the effects of Ang-III on the in vitro growth of human prostate cancer cells and the expression of APA and APN in cells treated with Ang-III or hormonal agents. Furthermore, we performed real-time quantitative PCR to investigate the expression pattern of APA and APN in 86 prostate tissue samples including normal prostate, untreated and hormone refractory prostate cancer (HRPC).

RESULTS

Ang-III stimulated cell proliferation, and the proliferative effect was inhibited by olmesartan, an AT(1) receptor blocker (ARB). Western blot analysis showed that phosphorylation of mitogen-activated protein kinase (MAPK) was enhanced by Ang-III and inhibited by olmesartan. APN mRNA level in HRPC was significantly lower than that in normal prostate and untreated prostate cancer tissue. In LNCaP cells, APN expression was augmented by Ang-III, whereas APA expression was not modulated. Hormonal agents, such as estradiol (E2) and dexamethasone (Dex), enhanced APA expression, but did not modulate APN expression in LNCaP cells.

CONCLUSIONS

Our results suggest that Ang-III and related converting enzymes contribute to cell proliferation of prostate cancer, and may be implicated in cancer progression.

Functional angiotensin II type 2 receptors inhibit growth factor signaling in LNCaP and PC3 prostate cancer cell lines

BACKGROUND

There is clear evidence of a tissue-based renin-angiotensin system in the prostate and studies to date suggest that AT(1)-receptor blocking drugs inhibit the growth of some prostate cancer cell lines and delay the development of prostate cancer. The present studies examine the action of Ang II in two prostate cancer cell lines and report the presence of functional AT(2)-receptors that regulate the actions of growth factors.

METHODS

Immunohistochemistry was used to identify the presence of Ang II and QPCR techniques to examine AT(1)- and AT(2)-receptor mRNA expression in androgen-dependent (LNCaP) and independent (PC3) cell lines. The effects of AT(1)- and AT(2)-receptor activation upon EGF-induced DNA synthesis and ERK2 phosphorylation in these cells were also examined.

RESULTS

Functional AT(2)-receptors together with Ang II were identified in both cell lines and stimulation of these receptors inhibited EGF-induced DNA synthesis and ERK2 phosphorylation. AT(1)-receptors, although present in both cell lines, were only functional in LNCaP cells where activation stimulated DNA synthesis.

CONCLUSIONS

Functional AT(2)-receptors are present and have the capacity to inhibit EGF-induced prostate cancer cell growth in LNCaP and fast growing androgen-independent PC3 cell lines, whereas functional AT(1)-receptors are found only in LNCaP cells where their activation stimulates DNA synthesis.

Androgen increases AT1a receptor expression in abdominal aortas to promote angiotensin II-induced AAAs in apolipoprotein E-deficient mice

OBJECTIVE

Castration of male apolipoprotein E-deficient (apoE-/-) mice reduces angiotensin II (Ang II)-induced abdominal aorta aneurysms (AAAs) to that of female mice. The purpose of this study was to determine whether this reduction is attributable to androgen-mediated regulation of aortic Ang II type 1A receptors (AT1aR).

METHODS AND RESULTS

AT1aR mRNA abundance in the AAA-prone region of abdominal aortas was 8-fold greater compared to thoracic aortas of male but not female mice. AT1aR mRNA abundance decreased after castration in abdominal but not thoracic aortas of male mice. Dihydrotestosterone (DHT, 0.16 mg/d) administration to castrated male mice restored AT1aR mRNA abundance in abdominal aortas but had no effect in thoracic aortas. DHT also increased AT1aR mRNA abundance in abdominal aortas from female mice. Castrated male or female apoE-/- mice were administered DHT during infusion of saline or Ang II (1000 ng/kg/min for 28 days). DHT administration did not alter serum cholesterol concentrations, lipoprotein distributions, or atherosclerotic lesion areas in either male or female mice. However, administration of DHT increased AAA incidence in male (27% placebo versus 75% DHT) and female mice (28% placebo versus 64% DHT).

CONCLUSIONS

Androgen promotes AT1aR mRNA abundance in abdominal aortas associated with increased Ang II-induced AAAs.

Significance of chemoprevention for prostate cancer development: experimental in vivo approaches to chemoprevention

Prostate cancer is the most common tumor in men in Western countries and mortality in Asian countries from the disease appears to be constantly increasing. Characteristics include (i) frequent discovery of latent carcinoma, even in countries with low incidences of clinical cancer; (ii) very long time to clinically significant cancer; (iii) few patients under 50 years of age (primarily a disease of elderly men); (iv) strong influences of environmental factors such as food; (v) temporal effectiveness of androgen deprival therapy; and (vi) no effective therapeutic approaches once hormone-refractory neoplasms have developed. Therefore prostate cancer is particularly indicated for preventive efforts, especially chemoprevention. Several large-scale chemoprevention trials have in fact been conducted and some have found suppressive effects. However, not all have been proven to have benefit. Experimental preclinical investigations, particularly using animal models, are recommended to find better chemopreventive agents with less adverse effects. Data using rat models have generated very interesting findings from which mechanism-based strategies can be proposed. In the present report the importance of chemoprevention of prostate cancer will be discussed using the data on human and rat prostate cancer development.

Angiotension II receptor 1 blocker modifies the expression of apoptosis-related proteins and transforming growth factor-beta1 in prostate tissue of spontaneously hypertensive rats

OBJECTIVE

To assess whether angiotensin II (Ang II), important in hypertension and highly expressed in benign prostatic hyperplasia (BPH), is involved in prostate growth, by analysing changes in the histological composition, tissue apoptotic status and level of transforming growth factor-beta1 (TGFbeta1) induced by an Ang II type 1 receptor blocker, losartan, in the prostates of spontaneously hypertensive (SH) rats.

MATERIALS AND METHODS

We assessed four groups of six rats each: normotensive Wistar-Kyoto counterparts of SH rats; untreated SH rats; SH rats given low-dose losartan (10 mg/kg/day for 10 weeks); and SH given high-dose losartan (30 mg/kg/day for 10 weeks). We evaluated the histological composition and expression of TGFbeta1 and apoptosis-related proteins, i.e. Bax and the 116-kDa poly (adenosine diphosphate-ribose) polymerase (PARP), by Western blotting in the rat prostate ventral lobes.

RESULTS

Compared with Wistar-Kyoto rats, untreated SH rats had a significantly increased epithelium component in the prostate (P < 0.01), but with losartan treatment, SH rats showed less of the epithelium component than untreated rats (P < 0.01 for both low- and high-dose losartan). Western-blot analysis showed a significantly increased level of Bax in high-dose losartan-treated rats (P < 0.01). The expression of 116 kDa PARP was also decreased in these rats (P < 0.01), which suggests increased caspase-3 activity. In addition, TGFbeta1 levels were significantly elevated in high-dose losartan-treated rats (P < 0.01).

CONCLUSION

These results show that losartan can induce apoptosis of prostate epithelium and increase the TGFbeta1 expression in SH rats, suggesting that Ang II stimulation might be involved in the pathogenesis of BPH, which might correlate with the regulation of TGFbeta1 expression.

Regulation of prostate cancer cell growth and PSA expression by angiotensin II receptor blocker with peroxisome proliferator-activated receptor gamma ligand like action

BACKGROUND

We previously reported that angiotensin II (AII) activated the proliferation of prostate cancer cells, and its antagonist, an AII receptor type 1 (AT1R) blocker (ARB), inhibited the proliferation of prostate cancer in vitro and in vivo. In the present study, we investigated whether telmisartan, an ARB, has a unique feature as a peroxisome proliferator-activated receptor gamma (PPARgamma) ligand, and its suppressive potential on prostate cancer cells.

METHODS

Cell count or MTT assay were carried out for growth suppression of prostate cancer cells. Phosphorylation of mitogen-activated protein kinase (MAPK), specific expression of prostate specific antigen (PSA) and AT1R were investigated by western blot. To confirm the PPARgamma activity of ARBs, luciferase assay using PSA promoter and PPARgamma response elements (PPRE) plasmids was performed.

RESULTS

The results showed that cell proliferation and signal transduction were inhibited by telmisartan treatment. Also, inhibition of PSA expression by telmisartan was confirmed by western blot and luciferase assay, indicating that an ARB acted in a similar way such as an anti-androgenic agent in prostate cancer cells.

CONCLUSION

The present study showed ARBs, especially those possessing a PPARgamma ligand-like structure, have a potential antagonistic effect on androgen-dependent and -independent prostate cancer.

G-protein-coupled receptors and cancer

G-protein-coupled receptors (GPCRs), the largest family of cell-surface molecules involved in signal transmission, have recently emerged as crucial players in tumour growth and metastasis. Malignant cells often hijack the normal physiological functions of GPCRs to survive, proliferate autonomously, evade the immune system, increase their blood supply, invade their surrounding tissues and disseminate to other organs. This Review will address our current understanding of the many roles of GPCRs and their signalling circuitry in tumour progression and metastasis. We will also discuss how interfering with GPCRs might provide unique opportunities for cancer prevention and treatment.

Angiotensin II type 1 receptor antagonist as an angiogenic inhibitor in prostate cancer

BACKGROUND

Angiotensin II (AII) type 1 receptor (AT1R) antagonists are used widely as antihypertensive agents, and long-term AT1R blockade may have a protective effect against cancer. We previously demonstrated that specific AT1R blockade with candesartan, an AT1R antagonist, inhibited vascular endothelial growth factor (VEGF) production and dramatically decreased lung metastasis of renal cancer by inhibiting tumor angiogenesis. This study was then undertaken to investigate the effects of AT1R blockade using candesartan in prostate cancer (PCa).

METHODS

We first determined whether hormone-independence is associated with tumor angiogenesis and AT1R expression. Accordingly, we postulated that AT1R blockade may affect angiogenesis in androgen-independent PCa rather than in androgen-dependent PCa, and investigated the effects of AII and candesartan on PCa cell lines and a tumor xenograft model.

RESULTS

A human hormone-refractory PCa (HRPC) and C4-2 androgen-independent PCa cell line showed significantly higher expression of VEGF, MVD, and AT1R than did human androgen-dependent PCa and an LNCaP androgen-dependent PCa cell line. In vitro, AII and candesartan did not directly affect the proliferation of LNCaP and C4-2 cells, but candesartan significantly suppressed VEGF production in C4-2 cells. In vivo, candesartan significantly suppressed VEGF expression, serum PSA concentration and tumor growth (1.1 +/- 0.2, 45.0 +/- 17.6 ng/ml, 235.8 +/- 37.4 mm(3)) in C4-2 xenografts in castrated mice, compared with the controls (2.4 +/- 0.6, 376.7 +/- 74.2 ng/ml, 830.8 +/- 147.6 mm(3)).

CONCLUSIONS

Candesartan exerted preventive effects on HRPC, rather than on androgen-sensitive PCa, through the inhibition of tumor angiogenesis.

Immunohistochemical analysis of low-grade and high-grade prostate carcinoma: relative changes of parathyroid hormone-related protein and its parathyroid hormone 1 receptor, osteoprotegerin and receptor activator of nuclear factor-kB ligand

AIM

To investigate multiple bone cytokines produced by prostate carcinoma (PCa) as a novel strategy to differentiate potential aggressiveness in localised PCa using immunohistochemical analysis.

METHODS

A total of 47 cases of PCa undergoing radical prostatectomy or transurethral prostatic resection at our institution (Fundación Jiménez Díaz (Grupo Capio), Madrid, Spain) between January 1991 and June 1998 were identified as low-grade (< or =4; n = 22) or high-grade (> or =7, excluding 7 (3+4) cases; n = 25) PCa according to Gleason grade. PCa specimens were immunostained for: parathyroid hormone (PTH)-related protein (PTHrP), the PTH1 receptor, osteoprotegerin and receptor activator of nuclear factor-kappa B ligand (RANKL), as well as Ki67 (a proliferation marker) and CD34 (an angiogenesis marker).

RESULTS

PCa samples showed an increased immunostaining for both osteoprotegerin and RANKL, associated with tumour grade and PTHrP positivity, in the tumoral epithelium. Using a score value of 4-corresponding to moderate staining - as cut-off, the best sensitivity value was for PTHrP (with C-terminal antiserum C6; 100 %); wheras the best specificity value was for RANKL (95 %).

CONCLUSIONS

All the evaluated factors are overexpressed mainly in the high-grade tumours. Our findings indicate that, in most patients with PCa (with Ki67 values between 1% and 9%), sequential determination of C-terminal PTHrP and RANKL immunoreactivities is a useful approach to discriminate low-grade and high-grade tumours.