Localisation of renin-angiotensin system (RAS) components in breast

Beyond blood pressure, fluid and electrolyte homeostasis - Role of the renin angiotensin aldosterone system in the interplay between metabolic diseases and breast cancer

The classical renin angiotensin aldosterone system (RAAS), as well as the recently described counter-regulatory or non-canonical RAAS have been well characterized for their role in cardiovascular homeostasis. Moreover, extensive research has been conducted over the past decades on both paracrine and the endocrine roles of local RAAS in various metabolic regulations and in chronic diseases. Clinical evidence from patients on RAAS blockers as well as pre-clinical studies using rodent models of genetic manipulations of RAAS genes documented that this system may play important roles in the interplay between metabolic diseases and cancer, namely breast cancer. Some of these studies suggest potential therapeutic applications and repurposing of RAAS inhibitors for these diseases. In this review, we discuss the mechanisms by which RAAS is involved in the pathogenesis of metabolic diseases such as obesity and type-2 diabetes as well as the role of this system in the initiation, expansion and/or progression of breast cancer, especially in the context of metabolic diseases.

Investigating the association of Angiotensin II Type I Receptor A1166C Polymorphism with Breast Cancer Risk in the Pakistani Population

The polymorphisms of the Renin-Angiotensin System are related to many disorders like diabetes, cardiovascular disease, and different types of cancer. Among all the polymorphisms related to AGTR1, A1166C has been associated with several disorders, including cardiovascular diseases and breast cancer. This study was conducted to discover the association of AGTR1 polymorphism (A1166C) Renin-Angiotensin and its effect on the development and progression of breast cancer in the Pakistani population. One hundred forty participants, including seventy diagnosed breast cancer patients and seventy healthy individuals, were included in this study and genotyped with an allele-specific polymerase chain reaction. The most frequent genotype in healthy participants and breast cancer patients was CC. An insignificant (p value>0.05) risk of breast cancer was found with A1166C polymorphism in codominant (CC vs. AA OR=1.200 [0.256-5.631] and AC vs. AA 0.941 [OR=0.223-3.976]), dominant (OR=1.00 [0.240-4.167]), recessive (OR=1.230 [0.593-2.552]) and additive models (OR=1.028 [0.533-1.983]) of general population genotypes. Nonetheless, when the AA genotype was considered a reference group, a significant association was found between AC and CC genotypes and invasive ductal and ductal carcinoma development in breast cancer patients. In conclusion, this study demonstrated no significant association between AGTR1 (A1166C) polymorphism and breast cancer risk.

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.

Angiotensin II and Angiotensin Receptors 1 and 2-Multifunctional System in Cells Biology, What Do We Know?

For years, the renin-angiotensin system (RAS) has been perceived as a system whose role is to primarily modulate the functioning of the cardiovascular system. Years of research into the role of RAS have provided the necessary data to confirm that the role of RAS is very complex and not limited to the cardiovascular system. The presence of individual elements of the renin-angiotensin (RA) system allows to control many processes, ranging from the memorization to pro-cancer processes. Maintaining the proportions between the individual axes of the RA system allows for achieving a balance, often called homeostasis. Thus, any disturbance in the expression or activity of individual RAS elements leads to pathophysiological processes.

Antihypertensive Drugs and Risk of Cancer: Between Scylla and Charybdis

Antihypertensive drugs namely angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, calcium channel blockers, beta blockers, and diuretics are among the most clearly documented regimens worldwide with an overall cardioprotective benefit. Given that malignancy is the second leading cause of mortality, numerous observational studies aimed to investigate the carcinogenic potential of these agents with conflicting results. The purpose of this review was to summarize current data in an effort to explore rare side effects and new mechanisms linking antihypertensive drugs with the risk of developing cancer.

Evaluating the benefits of renin-angiotensin system inhibitors as cancer treatments

G-protein-coupled receptors (GPCRs) are the largest and most diverse group of cellular membrane receptors identified and characterized. It is estimated that 30 to 50% of marketed drugs target these receptors. The angiotensin II receptor type 1 (AT1R) is a GPCR which signals in response to systemic alterations of the peptide hormone angiotensin II (AngII) in circulation. The enzyme responsible for converting AngI to AngII is the angiotensin-converting enzyme (ACE). Specific inhibitors for the AT1R (more commonly known as AT1R blockers or antagonists) and ACE are well characterized for their effects on the cardiovascular system. Combined with the extensive clinical data available on patient tolerance of AT1R blockers (ARBs) and ACE inhibitors (ACEIs), as well as their non-classical roles in cancer, the notion of repurposing this class of medications as cancer treatment(s) is explored in the current review. Given that AngII-dependent AT1R activity directly regulates angiogenesis, remodeling of vasculature, pro-inflammatory responses, stem cell programming and hematopoiesis, and electrolyte balance; the modulation of these processes with pharmacologically well characterized medications could present a valuable complementary treatment option for cancer patients.

Association of AGTR1 (A1166C) and ACE (I/D) Polymorphisms with Breast Cancer Risk in North Indian Population

Renin angiotensin system (RAS) comprising Angiotensin converting enzyme (ACE), Angiotensin II (Ang II) and its receptor Angiotensin II receptor type I (AGTR1), plays a critical role in several diseases including cancer. A single nucleotide polymorphism (SNP) A1166C located in 3' untranslated region (UTR) of AGTR1 and an insertion/deletion (I/D) polymorphism present in intron 16 of ACE gene have been associated with many diseases, but their association with Breast cancer (BCa) is still debatable. Here, we for the first time investigated the association of these polymorphisms in a North Indian BCa cohort including 161 patients and 152 healthy women. The polymorphisms were evaluated by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) respectively. The association between these polymorphisms and BCa risk was estimated by calculating Odds Ratio (OR) and chi-square (χ2) test. The DD genotype/D allele of ACE (I/D) polymorphism and "AC and CC" genotype/C allele of AGTR1 (A1166C) polymorphism were associated with higher risk of BCa when evaluated independently. Furthermore, interaction analysis of "AC and CC" and DD genotype and combination of "C and D" alleles of both polymorphisms revealed significantly greater BCa risk than that observed independently. Conclusively, women harboring "AC or CC" genotype/C allele for AGTR1 (A1166C) polymorphism and DD genotype/D allele for ACE (I/D) polymorphisms have a predisposition to develop more aggressive disease with advanced staging and larger tumor size. Our study indicates importance of genetic screening based on these polymorphisms for women, who may have higher risk of BCa.

The angiotensin receptor blocker, Losartan, inhibits mammary tumor development and progression to invasive carcinoma

Drugs that target the Renin-Angiotensin System (RAS) have recently come into focus for their potential utility as cancer treatments. The use of Angiotensin Receptor Blockers (ARBs) and Angiotensin-Converting Enzyme (ACE) Inhibitors (ACEIs) to manage hypertension in cancer patients is correlated with improved survival outcomes for renal, prostate, breast and small cell lung cancer. Previous studies demonstrate that the Angiotensin Receptor Type I (AT₁R) is linked to breast cancer pathogenesis, with unbiased analysis of gene-expression studies identifying significant up-regulation of AGTR1, the gene encoding AT₁R in ER^+ve/HER2^−ve tumors correlating with poor prognosis. However, there is no evidence, so far, of the functional contribution of AT₁R to breast tumorigenesis. We explored the potential therapeutic benefit of ARB in a carcinogen-induced mouse model of breast cancer and clarified the mechanisms associated with its success.

Mammary tumors were induced with 7,12-dimethylbenz[α]antracene (DMBA) and medroxyprogesterone acetate (MPA) in female wild type mice and the effects of the ARB, Losartan treatment assessed in a preventative setting (n = 15 per group). Tumor histopathology was characterised by immunohistochemistry, real-time qPCR to detect gene expression signatures, and tumor cytokine levels measured with quantitative bioplex assays. AT₁R was detected with radiolabelled ligand binding assays in fresh frozen tumor samples.

We showed that therapeutic inhibition of AT₁R, with Losartan, resulted in a significant reduction in tumor burden; and no mammary tumor incidence in 20% of animals. We observed a significant reduction in tumor progression from DCIS to invasive cancer with Losartan treatment. This was associated with reduced tumor cell proliferation and a significant reduction in IL-6, pSTAT3 and TNFα levels. Analysis of tumor immune cell infiltrates, however, demonstrated no significant differences in the recruitment of lymphocytes or tumour-associated macrophages in Losartan or vehicle-treated mammary tumors.

Analysis of AT₁R expression with radiolabelled ligand binding assays in human breast cancer biopsies showed high AT₁R levels in 30% of invasive ductal carcinomas analysed. Furthermore, analysis of the TCGA database identified that high AT₁R expression to be associated with luminal breast cancer subtype.

Our in vivo data and analysis of human invasive ductal carcinoma samples identify the AT₁R is a potential therapeutic target in breast cancer, with the availability of a range of well-tolerated inhibitors currently used in clinics. We describe a novel signalling pathway critical in breast tumorigenesis, that may provide new therapeutic avenues to complement current treatments.

Angiotensin-(1-7) counteracts the transforming effects triggered by angiotensin II in breast cancer cells

Angiotensin (Ang) II, the main effector peptide of the renin-angiotensin system, has been implicated in multiple aspects of cancer progression such as proliferation, migration, invasion, angiogenesis and metastasis. Ang-(1-7), is a biologically active heptapeptide, generated predominantly from AngII by the enzymatic activity of angiotensin converting enzyme 2. Previous studies have shown that Ang-(1-7) counterbalances AngII actions in different pathophysiological settings. In this study, we have analysed the impact of Ang-(1-7) on AngII-induced pro-tumorigenic features on normal murine mammary epithelial cells NMuMG and breast cancer cells MDA-MB-231. AngII stimulated the activation of the survival factor AKT in NMuMG cells mainly through the AT1 receptor. This PI3K/AKT pathway activation also promoted epithelial–mesenchymal transition (EMT). Concomitant treatment of NMuMG cells with AngII and Ang-(1-7) completely abolished EMT features induced by AngII. Furthermore, Ang-(1-7) abrogated AngII induced migration and invasion of the MDA-MB-231 cells as well as pro-angiogenic events such as the stimulation of MMP-9 activity and VEGF expression. Together, these results demonstrate for the first time that Ang-(1-7) counteracts tumor aggressive signals stimulated by AngII in breast cancer cells emerging the peptide as a potential therapy to prevent breast cancer progression.

Loss of constitutive ABCB1 expression in breast cancer associated with worse prognosis

ABCB1 gene encodes an adenosine 5′-triphosphate–binding cassette transporter, which not only confers multidrug resistance phenotype in malignant cells, but is also present in several nonmalignant tissues. For the last thirty years, ABCB1 expression in breast cancer has been described by many authors, but the extent of expression differs among the studies, and there is no consensus regarding its potential role in carcinogenesis or in the tumor response to antineoplastic drugs. This study aimed to characterize the expression of ABCB1 in breast tumors as a function of genetic, clinical, and histopathological variables. The ABCB1 expression was also evaluated in nonmalignant mammary tissues adjacent to tumors and in benign lesions. The detection of ABCB1 protein was performed by immunohistochemistry in tissue specimens of excised breasts obtained from a prospective cohort of Brazilian women with breast cancer. The association of ABCB1 protein levels with ABCB1 mRNA, gene polymorphisms, and clinical and histopathological variables was also evaluated. The Kaplan–Meier curves and multivariate Cox regression analyses were conducted to identify independent predictors of disease-free survival of patients with breast cancer. ABCB1 was detected in 86.3% (656) of breast tumors, 98.8% (606) of nonmalignant mammary tissue adjacent to tumors, and 100% (28) of benign lesions. Reduced ABCB1 protein levels in breast tumors was associated with triple-negative subtype (adjusted odds ratio [OR_adj] =0.24; 95% confidence interval [CI] =0.13–0.45), lymph node status < pN2 (OR_adj =0.27; 95% CI =0.10–0.71), tumor size >2 cm (OR_adj =0.55; 95% CI =0.32–0.93), and hypertensive status (OR_adj =0.42; 95% CI =0.24–0.73), and it was significantly associated with shorter disease-free survival, either for all breast cancer patients (p log-rank =0.012; hazard ratio [HR] =3.46; 95% CI =1.21–9.91) or for those with triple-negative tumors (p log-rank =0.007; HR =11.41; 95% CI =1.29–100.67). The loss of constitutive ABCB1 expression in breast cancer, especially in triple-negative tumors, seems to indicate a subgroup of worse prognosis.

Tissue Renin-Angiotensin System in Lacrimal Gland Fibrosis in a Murine Model of Chronic Graft-Versus-Host Disease

Chronic graft-versus-host disease (cGVHD) is a serious complication known to occur after allogeneic hematopoietic stem cell transplantation. Clinical manifestation includes inflammation and fibrosis. Many peripheral tissues are capable of generating the renin-angiotensin system (RAS) components, called the tissue RAS, and have various roles in tissue-specific physiological and pathological functions of inflammation and fibrosis. This article reviews evidence for the presence of the tissue RAS in the normal mouse lacrimal gland, the role of the tissue RAS in the fibrotic pathogenesis of the lacrimal gland in cGVHD model mice, and the effect of angiotensin II receptor blockers on preventing lacrimal gland fibrosis. B10.D2→BALB/c (H-2d) major histocompatibility complex-compatible, minor histocompatibility antigen-mismatched mice were used as a model of cGVHD, which reflects the clinical and pathological symptoms of human cGVHD. We also describe the localization of RAS components in the normal mouse lacrimal gland. In addition, we characterize the inflammatory and fibrotic changes of the lacrimal gland in cGVHD model mice, demonstrate that fibroblasts strongly express angiotensin II, angiotensin II type 1 receptor (AT1R), and angiotensin II type 2 receptor, and show that mRNA expression of angiotensinogen increased in the lacrimal gland of cGVHD model mice. Inhibitory experiments revealed that lacrimal gland fibrosis was suppressed in mice treated with an AT1R blocker, but not in mice treated with an angiotensin II type 2 receptor blocker. Hence, we conclude that the tissue RAS is involved in the fibrotic pathogenesis of the lacrimal gland and that AT1R blockers have a therapeutic effect on lacrimal gland fibrosis in cGVHD model mice.

A Rat Model to Study the Effects of Diet-Induced Obesity on Radiation-Induced Mammary Carcinogenesis

A detailed understanding of the relationship between radiation-induced breast cancer and obesity is needed for appropriate risk management and to prevent the development of a secondary cancer in patients who have been treated with radiation. Our goal was to develop an animal model to study the relationship by combining two existing Sprague-Dawley rat models of radiation-induced mammary carcinogenesis and diet-induced obesity. Female rats were fed a high-fat diet for 4 weeks and categorized as obesity prone or obesity resistant based on their body weight at 7 weeks of age, at which time the rats were irradiated with 4 Gy. Control rats were fed a standard diet and irradiated at the same time and in the same manner. All rats were maintained on their initial diets and assessed for palpable mammary cancers once a week for the next 30 weeks. The obesity-prone rats were heavier than those in the other groups. The obesity-prone rats were also younger than the other animals at the first detection of mammary carcinomas and their carcinoma weights were greater. A tendency toward higher insulin and leptin blood levels were observed in the obesity-prone rats compared to the other two groups. Blood angiotensin II levels were elevated in the obesity-prone and obesity-resistant rats. Genes related to translation and oxidative phosphorylation were upregulated in the carcinomas of obesity-prone rats. Expression profiles from human breast cancers were used to validate this animal model. As angiotensin is potentially an important factor in obesity-related morbidities and breast cancer, a second set of rats was fed in a similar manner, irradiated and then treated with an angiotensin-receptor blocker, losartan and candesartan. Neither blocker altered mammary carcinogenesis; analyses of losartan-treated animals indicated that expression of renin in the renal cortex and of Agtr1a (angiotensin II receptor, type 1) in cancer tissue was significantly upregulated, suggesting the presence of compensating mechanisms for blocking angiotensin-receptor signaling. Thus, obesity-related elevation of insulin and leptin blood levels and an increase in available energy may facilitate sustained protein synthesis in cancer cells, which is required for rapid cancer development.

Overexpression of angiotensin II type 1 receptor in breast cancer cells induces epithelial-mesenchymal transition and promotes tumor growth and angiogenesis

The angiotensin II type I receptor (AGTR1) has been implicated in diverse aspects of human disease, from the regulation of blood pressure and cardiovascular homeostasis to cancer progression. We sought to investigate the role of AGTR1 in cell proliferation, epithelial-mesenchymal transition (EMT), migration, invasion, angiogenesis and tumor growth in the breast cancer cell line MCF7. Stable overexpression of AGTR1 was associated with accelerated cell proliferation, concomitant with increased expression of survival factors including poly(ADP-ribose) polymerase (PARP) and X-linked inhibitor of apoptosis (XIAP), as well as extracellular signal-regulated kinase (ERK) activation. AGTR1-overexpressing MCF7 cells were more aggressive than their parent line, with significantly increased activity in migration and invasion assays. These observations were associated with changes in EMT markers, including reduced E-cadherin expression and increased p-Smad3, Smad4 and Snail levels. Treatment with the AGTR1 antagonist losartan attenuated these effects. AGTR1 overexpression also accelerated tumor growth and increased Ki-67 expression in a xenograft model. This was associated with increased tumor angiogenesis, as evidenced by a significant increase in microvessels in the intratumoral and peritumoral areas, and enhanced tumor invasion, with the latter response associated with increased EMT marker expression and matrix metallopeptidase 9 (MMP-9) upregulation. In vivo administration of losartan significantly reduced both tumor growth and angiogenesis. Our findings suggest that AGTR1 plays a significant role in tumor aggressiveness, and its inhibition may have therapeutic implications.

Angiotensin II accelerates mammary gland development independently of high blood pressure in pregnancy-associated hypertensive mice

Angiotensin II (AngII) is a vasopressor hormone that has critical roles in maintenance of normal blood pressure and pathogenesis of cardiovascular diseases. We previously generated pregnancy-associated hypertensive (PAH) mice by mating female human angiotensinogen transgenic mice with male human renin transgenic mice. PAH mice exhibit hypertension in late pregnancy by overproducing AngII. A recent study demonstrated that angiotensin II type I (AT1) receptor is expressed in mammary epithelial cells and its signaling is critical for mammary gland involution after weaning. However, the role of AngII-AT1 receptor signaling in the development of mammary gland during pregnancy remains unclear. In this study, to investigate the role of AngII-AT1 receptor signaling in mammary gland development during pregnancy, we analyzed the mammary gland of PAH mice. Histological and gene expression analyses revealed that lobuloalveolar development was accelerated with increased milk protein production and lipid accumulation in the mammary gland of PAH mice. Furthermore, AT1 receptor blocker treatment suppressed acceleration of mammary gland development in PAH mice, while the treatment of hydralazine, another antihypertensive drug, did not. These data suggest that AngII-AT1 receptor-induced signaling accelerates mammary gland development during pregnancy through hypertension-independent mechanism.

G-protein coupled receptors of the renin-angiotensin system: new targets against breast cancer?

G-protein coupled receptors (GPCRs) constitute the largest family of membrane receptors, with high potential for drug discovery. These receptors can be activated by a panel of different ligands including ions, hormones, small molecules, and vasoactive peptides. Among those, angiotensins [angiotensin II (AngII) and angiotensin 1–7] are the major biologically active products of the classical and alternative renin-angiotensin system (RAS). These peptides bind and activate three different subtypes of GPCRs, namely AT1, AT2, and Mas receptors, to regulate cardiovascular functions. Over the past decade, the contribution of several RAS components in tumorigenesis has emerged as a novel important concept, AngII being considered as harmful and Ang1–7 as protective against cancer. Development of selective ligands targeting each RAS receptor may provide novel and efficient targeted therapeutic strategies against cancer. In this review, we focus on breast cancer to summarize current knowledge on angiotensin receptors (AT1, AT2, and Mas), and discuss the potential use of angiotensin receptor agonists and antagonists in clinics.

Association between AT1 and AT2 angiotensin II receptor expression with cell proliferation and angiogenesis in operable breast cancer

Angiotensin II (ANGII) has been associated with vascular proliferation in tumor and non-tumor models through its receptors AT1 and AT2. Our objective was to determine AT1 and AT2 receptor expression in operable breast cancer and its association with tumor grade, vascular density, and cellular proliferation. Seventy-seven surgically malignant breast tumors with no distant metastasis were included, and 7 benign lesions were used as controls. AT1 and AT2 receptor expression was determined by RT-PCR and immunohistochemistry (IHC) in 68 out of the 77 malignant lesions and in the 7 benign lesions. AT1 and AT2 receptor expression was detected in 35.3 and 25 % of cases, in both RT-PCR and IHC. Tumors that express AT1 showed an increase in T3 stage (92.3 vs. 7.7 % p < 0.001), mitotic index (4 ± 1 vs 2 ± 1, p = 0.05), vascular density (15 ± 3 vs 8 ± 5, p = 0.05), and cellular proliferation (85 ± 18 vs 55 ± 10, p = 0.01) versus AT1-negative lesions. Non-differences between clinical-pathologic variables and AT2 expression were found. AT1 receptor expression was associated to enhance angiogenesis and cellular proliferation rate, but no relationship with AT2 was found. ANGII and its peptides might play a role in the development and pathophysiology of breast cancer, and this could be valuable in the in the development of targeted therapies.

Expression of (pro)renin receptor in breast cancers and its effect on cancercell proliferation

(Pro)renin receptor ((P)RR) is a specific receptor for renin and prorenin. The aim of the present study is to clarify expression of (P)RR and pathophysiological roles of (P)RR in human breast carcinomas. (P)RR expression was studied in 69 clinical cases of breast carcinoma by immunohistochemistry.Effects of (P)RR on cell proliferation were examined in cultured human breast carcinoma cells using (P)RR specific small interference RNA. Immunohistochemistry showed that(P)RR immunoreactivity was detected in the breast carcinoma cells in 50 of 69 cases of breast carcinoma (72%). The analysis on association between (P)RR immunoreactivity and clinicopathological parameters showed that the number of (P)RR positive cases was significantly greater in Ki-67 (a cell proliferation marker)≥10% group than in Ki-67<10% group (P=0.02). (P)RR was expressed in 4 types of human breast carcinoma cell lines. (P)RR specific small interference RNA inhibited proliferation of both MCF-7 (ERα positive) and SK-BR-3 (ERα negative) cells. The present study has shown, for the first time, the expression of (P)RR in human breast carcinoma tissues and cultured breast carcinoma cell lines. These findings have raised the possibility that the blockade of the (P)RR signaling may be a novel therapeutic strategy against breast carcinomas.

Effect of angiotensin receptor blockade on prevention and reversion of tamoxifen-resistant phenotype in MCF-7 cells

Tamoxifen (TAM) is a standard adjuvant endocrine therapy in postmenopausal breast cancer patients, but innate or acquired TAM resistance has remained to be a therapeutic challenge for clinicians. The aim of this study was to explore the possible participation of renin-angiotensin system (RAS) in the acquisition of TAM resistance and try to prevent and regress the resistance using an angiotensin II receptor type-1 (AGTR1) blocker, losartan. Establishment of TAM-resistant (TAM-R) cells was accomplished by continuous exposure of MCF-7 cells to 1 μmol/L TAM. MTT (3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay was performed to determine cell growth. Moreover, messenger RNA (mRNA) expression levels of AGTR1 and angiotensin II receptor type-2 (AGTR2) were measured by quantitative real-time polymerase chain reaction. A significant increase of AGTR1 and AGTR2 transcripts was observed in TAM-R cells compared to MCF-7 cells. Interestingly, losartan-TAM combination effectively resensitized TAM-R cells to tamoxifen treatment by inducing cell death. Therefore, our findings suggest an important role of RAS in acquired TAM resistance and targeting of RAS by losartan may overcome TAM resistance phenomenon and provide a novel avenue for treatment of resistant breast cancers.

Vacuolar H+-ATPase: An Essential Multitasking Enzyme in Physiology and Pathophysiology

Vacuolar H+-ATPases (V-ATPases) are large multisubunit proton pumps that are required for housekeeping acidification of membrane-bound compartments in eukaryotic cells. Mammalian V-ATPases are composed of 13 different subunits. Their housekeeping functions include acidifying endosomes, lysosomes, phagosomes, compartments for uncoupling receptors and ligands, autophagosomes, and elements of the Golgi apparatus. Specialized cells, including osteoclasts, intercalated cells in the kidney and pancreatic beta cells, contain both the housekeeping V-ATPases and an additional subset of V-ATPases, which plays a cell type specific role. The specialized V-ATPases are typically marked by the inclusion of cell type specific isoforms of one or more of the subunits. Three human diseases caused by mutations of isoforms of subunits have been identified. Cancer cells utilize V-ATPases in unusual ways; characterization of V-ATPases may lead to new therapeutic modalities for the treatment of cancer. Two accessory proteins to the V-ATPase have been identified that regulate the proton pump. One is the (pro)renin receptor and data is emerging that indicates that V-ATPase may be intimately linked to renin/angiotensin signaling both systemically and locally. In summary, V-ATPases play vital housekeeping roles in eukaryotic cells. Specialized versions of the pump are required by specific organ systems and are involved in diseases.

Evaluation of (131)I-anti-angiotensin II type 1 receptor monoclonal antibody as a reporter for hepatocellular carcinoma

Background

Finding a specific agent is useful for early detection of tumor. Angiotensin II type 1 receptor (AT₁R) was reported to be elevated in a variety of tumors and participate in tumor progression. The aim of our study was to evaluate whether ¹³¹I-anti-AT₁R monoclonal antibody (mAb) is an efficient imaging reporter for the detection of hepatocellular carcinoma.

Methodology/Principal Findings

AT₁R mAb or isotype IgG was radioiodinated with ¹³¹I and the radiochemical purity and stability of the two imaging agents and the affinity of ¹³¹I-anti-AT₁R mAb against AT₁R were measured. 3.7 MBq ¹³¹I-anti-AT₁R mAb or isotype ¹³¹I-IgG was intravenously injected to mice with hepatocellular carcinoma through tail vein, and then the whole-body autoradiography and biodistribution of the two imaging agents and the pharmacokinetics of ¹³¹I-anti-AT₁R mAb were studied. ¹³¹I-anti-AT₁R mAb and ¹³¹I-IgG were successfully radioiodinated and both maintained more stable in serum than in saline. The ¹³¹I-anti-AT₁R mAb group showed much clearer whole-body images for observing hepatocellular carcinoma than the ¹³¹I-IgG group. The biodistributions of the two imaging agents suggested that hepatocellular carcinoma tissue uptook more ¹³¹I-anti-AT₁R mAb than other tissues (%ID/g = 1.82±0.40 and T/NT ratio = 7.67±0.64 at 48 h), whereas hepatocellular carcinoma tissue did not selectively uptake ¹³¹I-IgG (%ID/g = 0.42±0.06 and T/NT ratio = 1.33±0.08 at 48 h). The pharmacokinetics of ¹³¹I-anti-AT₁R mAb was in accordance with the two-compartment model, with a rapid distribution phase and a slow decline phase. These results were further verified by real-time RT-PCR, immunohistochemistry staining and Western blot.

Conclusions/Significance

¹³¹I-anti-AT₁R mAb may be a potential target for early detection of tumor.

Expression and clinical significance of angiotensin II type 1 receptor in human hepatocellular carcinoma

This study aimed to investigate the expression of angiotensin II type 1 receptor (AT-1R) mRNA and the AT-1R protein in human primary hepatocellular carcinoma (PHC), and to attempt to elucidate their association with pathological and clinical characteristics. Fresh tumor and normal liver tissues were obtained from 44 patients with PHC following hepatectomies. AT-1R mRNA levels were quantitatively analyzed by quantitative polymerase chain reaction (qPCR) while the protein levels were assessed by immunohistochemistry. The expression levels of AT-1R were observed in hepatocellular carcinoma tissues and normal liver tissues. The level of AT-1R protein expression in normal liver tissues was higher compared with that in PHC tissues (P=0.0033). The AT-1R mRNA levels were higher in patients with negative hepatitis B virus surface antigen (HBsAg), normal α-fetoprotein (AFP) levels and high tumor differentiation, compared with those in patients with positive HBsAg (P=0.0005), upregulated AFP levels (P=0.0008) and poor tumor differentiation (P=0.0290). No significant correlation was identified between the expression levels of AT-1R mRNA and general characteristics such as gender, age, cirrhotic nodules, tumor size, tumor encapsulation, tumor number, carcinoma embolus, tumor metastasis or tumor recurrence. Downregulated levels of AT-1R mRNA and AT-1R protein may indicate a poor prognosis for patients with PHC.

A functional siRNA screen identifies genes modulating angiotensin II-mediated EGFR transactivation

The angiotensin type 1 receptor (AT1R) transactivates the epidermal growth factor receptor (EGFR) to mediate cellular growth, however, the molecular mechanisms involved have not yet been resolved. To address this, we performed a functional siRNA screen of the human kinome in human mammary epithelial cells that demonstrate a robust AT1R-EGFR transactivation. We identified a suite of genes encoding proteins that both positively and negatively regulate AT1R-EGFR transactivation. Many candidates are components of EGFR signalling networks, whereas others, including TRIO, BMX and CHKA, have not been previously linked to EGFR transactivation. Individual knockdown of TRIO, BMX or CHKA attenuated tyrosine phosphorylation of the EGFR by angiotensin II stimulation, but this did not occur following direct stimulation of the EGFR with EGF, indicating that these proteins function between the activated AT1R and the EGFR. Further investigation of TRIO and CHKA revealed that their activity is likely to be required for AT1R-EGFR transactivation. CHKA also mediated EGFR transactivation in response to another G protein-coupled receptor (GPCR) ligand, thrombin, indicating a pervasive role for CHKA in GPCR-EGFR crosstalk. Our study reveals the power of unbiased, functional genomic screens to identify new signalling mediators important for tissue remodelling in cardiovascular disease and cancer.

Angiotensin-converting enzyme inhibitors enhance the effect of cyclooxygenase inhibitors on breast cancer: a nationwide case-control study

OBJECTIVES

Angiotensin-converting enzyme (ACE) inhibitors are first-line antihypertensive and potential cancer preventive agents. Interest in breast cancer prevention is growing, and more clinical evidence is needed regarding the effects of preventive therapy, alone or in combination.

METHODS

This was a nationwide case-control analysis from the Taiwan National health Insurance Research Database. We analyzed 16,847 female breast cancer patients (diagnosed between 1 January 2002 and 31 December 2008) and 50,541 matched individuals. Longitudinal exposure to ACE inhibitors and cyclooxygenase inhibitors was compared.

RESULTS

The risk of developing breast cancer among patients taking both aspirin and an ACE inhibitor decreased as the ACE inhibitor dose increased. Among patients receiving between 28 and 364 cumulative defined daily doses (cDDDs) of aspirin, the adjusted odds ratios (ORs) were 0.97 (0.90-1.06), 0.91 (0.82-1.03), and 0.79 (0.68-0.92) for women taking ACE inhibitors for 0-27, 28-364, and more than 365 cDDD, respectively. Among women receiving more than 365 cDDD of aspirin, the adjusted ORs were 0.91 (0.80-1.03), 0.81 (0.70-0.94), and 0.81 (0.71-0.92) as the ACE inhibitor dose increased, respectively. Women taking nonaspirin NSAIDs along with an ACE inhibitor had the same finding. Among women taking 28-364 cDDD of NSAIDs, the adjusted ORs were 0.85 (0.81-0.89), 0.87 (0.81-0.94), and 0.80 (0.73-0.88); for women receiving more than 365 cDDD of NSAIDs, the adjusted ORs were 0.68 (0.62-0.74), 0.61 (0.53-0.70), and 0.60 (0.52-0.70) as the ACE inhibitor dose increased, respectively.

CONCLUSION

The findings of this nationwide analysis support the hypothesis that ACE inhibitors enhance the antitumor effect of cyclooxygenase inhibitors on breast cancer.

Angiotensin modulates human mammary epithelial cell motility

INTRODUCTION

Angiotensin II is an effector peptide showing multiple physiological effects, such as regulation of vascular tone, tissue growth and remodelling. Postlactational involution of mammary gland involves changes such as high matrix metalloproteinase activity and release of bioactive fragments of fibronectin and laminin, which may be directly regulated by angiotensin II. The aim of the present study was to evaluate the influence of angiotensin II on proliferation, viability and motility of normal human mammary epithelial cells (184A1 cell line) and to determine the role of angiotensin II receptors in these processes.

MATERIALS AND METHODS

Real-time reverse transcription-PCR, western blot and gelatin zymography were used to study the effect of angiotensin II on the expression of angiotensin receptors and matrix metalloproteinases in 184A1 cells. WST-1, AlamarBlue and BrdU assays were used as indicators of cell viability and proliferation after angiotensin II stimulation. Boyden chamber assays and monolayer wound migration assay were used to evaluate in vitro the changes in cell adhesion, migration and invasion.

RESULTS

Angiotensin II increased motility of the 184A1 cells and the ability of wound closure. Modifications in cell-substrate adhesion systems and increased secretion and activity of matrix metalloproteinases were also observed. The effect of angiotensin II was abolished by blocking angiotensin type 1 receptor with specific inhibitors candesartan and losartan.

CONCLUSIONS

The results indicate that angiotensin II modulates cell behaviour via AT1-R and stimulates secretion of MMP-2 by human mammary epithelial cells.

Angiotensin II type 1 receptor (AT-1R) expression correlates with VEGF-A and VEGF-D expression in invasive ductal breast cancer

Recent studies point to the involvement of angiotensin II (Ang II) receptor type 1 (AT-1R) on processes of metastasing, stimulation of invasiveness and angiogenesis in tumours. In this study, the correlation between intensity of AT-1R expression and expression of lymph- and angiogenesis markers in invasive ductal breast cancers (IDC) was examined. Immunohistochemical studies (IHC) were performed on archival material of 102 IDC cases. Only 28 (27.5%) cases manifested low AT-1R expression while 74 (72.5%) cases demonstrated a moderate or pronounced AT-1R expression. Expression intensity of AT-1R was found to correlate with expressions of VEGF-A (r = 0.26; p = 0.008) and VEGF-D (r = 0.24; p = 0.015). Out of the examined markers of angiogenesis and lymphangiogenesis only the pronounced expression of VEGF-C was found to correlate with patient poor clinical outcome (p = 0.009). The positive correlation between AT-1R and VEGF-A and VEGF-D could point to stimulatory action of Ang II on their expression what might result in augmented lymph- and angiogenesis in IDC.

Angiotensin II facilitates breast cancer cell migration and metastasis

Breast cancer metastasis is a leading cause of death by malignancy in women worldwide. Efforts are being made to further characterize the rate-limiting steps of cancer metastasis, i.e. extravasation of circulating tumor cells and colonization of secondary organs. In this study, we investigated whether angiotensin II, a major vasoactive peptide both produced locally and released in the bloodstream, may trigger activating signals that contribute to cancer cell extravasation and metastasis. We used an experimental in vivo model of cancer metastasis in which bioluminescent breast tumor cells (D3H2LN) were injected intra-cardiacally into nude mice in order to recapitulate the late and essential steps of metastatic dissemination. Real-time intravital imaging studies revealed that angiotensin II accelerates the formation of metastatic foci at secondary sites. Pre-treatment of cancer cells with the peptide increases the number of mice with metastases, as well as the number and size of metastases per mouse. In vitro, angiotensin II contributes to each sequential step of cancer metastasis by promoting cancer cell adhesion to endothelial cells, trans-endothelial migration and tumor cell migration across extracellular matrix. At the molecular level, a total of 102 genes differentially expressed following angiotensin II pre-treatment were identified by comparative DNA microarray. Angiotensin II regulates two groups of connected genes related to its precursor angiotensinogen. Among those, up-regulated MMP2/MMP9 and ICAM1 stand at the crossroad of a network of genes involved in cell adhesion, migration and invasion. Our data suggest that targeting angiotensin II production or action may represent a valuable therapeutic option to prevent metastatic progression of invasive breast tumors.

The renin-angiotensin system in the breast and breast cancer

Much evidence now suggests that angiotensin II has roles in normal functions of the breast that may be altered or attenuated in cancer. Both angiotensin type 1 (AT1) and type 2 (AT2) receptors are present particularly in the secretory epithelium. Additionally, all the elements of a tissue renin-angiotensin system, angiotensinogen, prorenin and angiotensin-converting enzyme (ACE), are also present and distributed in different cell types in a manner suggesting a close relationship with sites of angiotensin II activity. These findings are consistent with the concept that stromal elements and myoepithelium are instrumental in maintaining normal epithelial structure and function. In disease, this system becomes disrupted, particularly in invasive carcinoma. Both AT1 and AT2 receptors are present in tumours and may be up-regulated in some. Experimentally, angiotensin II, acting via the AT1 receptor, increases tumour cell proliferation and angiogenesis, both these are inhibited by blocking its production or function. Epidemiological evidence on the effect of expression levels of ACE or the distribution of ACE or AT1 receptor variants in many types of cancer gives indirect support to these concepts. It is possible that there is a case for the therapeutic use of high doses of ACE inhibitors and AT1 receptor blockers in breast cancer, as there may be for AT2 receptor agonists, though this awaits full investigation. Attention is drawn to the possibility of blocking specific AT1-mediated intracellular signalling pathways, for example by AT1-directed antibodies, which exploit the possibility that the extracellular N-terminus of the AT1 receptor may have previously unsuspected signalling roles.

AT1 receptor blockade delays postlactational mammary gland involution: a novel role for the renin angiotensin system

Angiotensin II (AngII), the main effector peptide of the renin-angiotensin system (RAS), participates in multiple biological processes, including cell growth, apoptosis, and tissue remodeling. Since AngII activates, in different cell types, signal transducing pathways that are critical for mammary gland postlactational regression, we investigated the role of the RAS during this process. We found that exogenous administration of AngII in mammary glands of lactating Balb/c mice induced epithelium apoptosis [2.9±0.5% (control) vs. 9.6±1.1% (AngII); P < 0.001] and activation of the proapoptotic factor STAT3, an effect inhibited by irbesartan, an AT(1) receptor blocker. Subsequently, we studied the expression kinetics of RAS components during involution. We found that angiotensin-converting enzyme (ACE) mRNA expression peaked 6 h after weaning (5.7-fold; P<0.01), while induction of angiotensinogen and AT(1) and AT(2) receptors expression was detected 96 h after weaning (6.2-, 10-, and 6.2-fold increase, respectively; P<0.01). To assess the role of endogenously generated AngII, mice were treated with losartan, an AT(1) receptor blocker, during mammary involution. Mammary glands from losartan-treated mice showed activation of the survival factors AKT and BCL-(XL), significantly lower LIF and TNF-α mRNA expression (P<0.05), reduced apoptosis [12.1±2.1% (control) vs. 4.8±0.7% (losartan); P<0.001] and shedding of epithelial cells, inhibition of MMP-9 activity in a dose-dependent manner (80%; P<0.05; with losartan IC(50) value of 6.9 mg/kg/d] and lower collagen deposition and adipocyte invasion causing a delayed involution compared to vehicle-treated mice. Furthermore, mammary glands of forced weaned AT(1A)- and/or AT(1B)-deficient mice exhibited retarded apoptosis of epithelial cells [6.3±0.95% (WT) vs. 3.3±0.56% (AT(1A)/AT(1B) DKO); P<0.05] with remarkable delayed postlactational regression compared to wild-type animals. Taken together, these results strongly suggest that AngII, via the AT(1) receptor, plays a major role in mouse mammary gland involution identifying a novel role for the RAS. angiotensin system.

Inhibition of the renin-angiotensin system downregulates tissue factor and vascular endothelial growth factor in human breast carcinoma cells

INTRODUCTION

The renin-angiotensin system (RAS) promotes angiogenesis and growth of neoplastic cells. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor AT1 blockers may protect against cancer. Tissue factor (TF), for its involvement in tumor growth, angiogenesis, and metastasis is considered a hallmark of cancer progression. In this study we evaluated whether RAS blockade modulates TF constitutive expression by the metastatic breast carcinoma MDA-MB-231 cell line.

MATERIALS AND METHODS

Cell TF activity was assessed by one stage clotting time, TF and VEGF antigens and mRNA levels by ELISA and RT-PCR, respectively. AT(1) was detected by flow-cytometry and angiotensin-II levels by EIA.

RESULTS

Captopril reduced in a concentration-dependent way both the strong constitutive TF activity (983.2±55.2 vs. 686.7±135.1U/5×10(5) cells with 10μg/ml captopril) and antigen (32.3±5.9 vs. 13.2±6.6ng/ml) in MDA-MB-231. Similar results were observed with enalapril. AT1 was present on cell membrane and losartan, a competitive inhibitor of AT1, reduced TF expression to a degree similar as that exerted by ACE inhibitors. Moreover, captopril and losartan downregulated the constitutive mRNA TF expression by ~35%. Similar results were observed with anti-AT1 and angiotensin II antibodies. In addition, the constitutive VEGF antigen and mRNA levels were reduced in the presence of captopril or losartan, and an anti-VEGF antibody downregulated cell TF activity by ~40%.

CONCLUSIONS

These results could, at least in part, contribute to the discussion about the possible effects of ACE inhibitors and AT1 receptor antagonists in malignancy, and offer new clues to support their use for tumor control.

Analysis of the expression of angiotensin II type 1 receptor and VEGF in endometrial adenocarcinoma with different clinicopathological characteristics

In Poland, endometrial carcinoma takes second place after breast cancer among all cancers in women and is considered the most common genital cancer. It has been repeatedly reported that angiotensin is involved in the development and invasion of some cancers including breast, ovarian, and pancreatic ones. It is suggested that angiotensin two and its receptors are actively involved in tumour biology in endometrial adenocarcinoma. In the present study, we identify a possible relationship between the expression of AT1-R, AT2-R, ERα, and VEGF and clinicopathological characteristics of primary endometrial adenocarcinoma. We determined the above components both at the mRNA (real-time RT-PCR) and protein levels (Western Blot assay). Our results indicate that in patients with grade G3 adenocarcinoma, the expression of AT1-R significantly decreased in comparison with G1 patients (p = 0.034), but the level of ERα was the highest in G2 and the lowest in G3. Moreover, the level of VEGF mRNA significantly increased between G2 and G3 (p = 0.034). We also noted a significant correlation between the expression of AT1-R and AT2-R in FIGO stage 1 (R (s) = 0.9636; p = 0.0001) and that of AT2-R and VEGF (R (s) = 0.5377; p = 0.005). In grade G1 and G2 carcinoma, a significant correlation was also found between the expression of AT1-R and AT2-R (R (s) = 0.9924; p = 0.0001; R (s) = 0.8717, p = 0.0005, respectively), but in grade G1, a negative correlation was observed between AT1-R and VEGF (R (s) = -0.8945, p = 0.0005). Further studies are required to clarify the biological function of the angiotensin receptor in regulating VEGF expression in endometrial carcinoma.

RAS polymorphisms in cancerous and benign breast tissue

Recent information has revealed new roles in the angiogenic processes linked to the rennin-angiotensin system. To date few studies have been done on the association between RAS genes and cancer and the majority focus mainly on angiotensin I-converting enzyme (ACE). For breast cancer there are three reports that include the angiotensin II receptor, subtype 1 (AGTR1), only one for angiotensinogen (AGT) and none for renin gene (REN). In the present study we investigate whether REN (Bgll), AGT (M235T), ACE (A245T, Indel), and AGTR1 (A1166C) are associated with breast cancer. Polymorphisms were analysed by PCR and RFPLs or sequence specific assay in three groups: breast cancer, benign breast disease (BBD) and general population. REN polymorphism shows that homozygous for A allele have an increased risk for BBD. Differences in M235T genotype frequencies were significant with less heterozygous in breast cancer. With different risk values ACE indel was associated with BBD and breast cancer. Association of AGTR1 was observed only in the breast cancer group, where C allele carriers present a reduced risk. Results of this work supports previous observations on the possible involvement of this system in breast cancer but it also suggests a role in benign disease.

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/angiotensin II type I receptor (AT1R) signaling promotes MCF-7 breast cancer cells survival via PI3-kinase/Akt pathway

Angiotensin II (Ang II) is a bioactive peptide of the renin-angiotensin system, acting not only as a vasoconstrictor but also as a growth promoter via angiotensin II type 1 receptor (AT1R) in some cancer. In this study, we examined the mechanisms by which Ang II affected the cell proliferation in AT1R-positive MCF-7 human breast cancer cells. Ang II stimulated the growth of breast cancer cells in a dose- and time-dependent manner. The maximal proliferation effect on MCF-7 cells was obtained with 10(-4) M Ang II at 24 h. Losartan (10(-5) M, an AT1R antagonist) significantly decreased the level of Ang-II-induced proliferative effects, whereas PD123319 (10(-5) M, an AT2R antagonist) had no effects. Moreover, Ang II could significantly accelerate S-phase progression, which was inhibited by losartan (10(-5) M) or LY294002 (50 microM, a PI3-kinase inhibitor). In addition, Ang II caused rapid activation of p-Akt in a dose- and time-dependent manner. 10(-4) M Ang II induced a significant increase of p-Akt in 15 min. The peak level of p-Akt could be persisted for at least 6 h. Among the signaling molecules downstream of Akt, we revealed that Ang II also significantly upregulated CyclinD1, GSK3beta, and downregulated p27. Pretreatment with losartan (10(-5) M) or LY294002 (50 microM) could significantly suppress these effects of Ang II. These findings suggest that Ang II plays a role in the growth of AT1R-positive breast cancer cells through PI3-kinase/Akt pathway activation. Therefore, targeting Ang II/AT1R signaling could be a novel therapeutic for breast cancer.

Changes in the renin angiotensin system during the development of colorectal cancer liver metastases

BACKGROUND

Blockade of the renin angiotensin system (RAS) via angiotensin I converting enzyme (ACE) inhibition reduces growth of colorectal cancer (CRC) liver metastases in a mouse model. In this work we defined the expression of the various components of the RAS in both tumor and liver during the progression of this disease.

METHODS

Immunohistochemistry and quantitative RT-PCR was used to examine RAS expression in a mouse CRC liver metastases model. CRC metastases and liver tissue was assessed separately at key stages of CRC liver metastases development in untreated (control) mice and in mice treated with the ACE inhibitor captopril (750 mg/kg/day). Non-tumor induced (sham) mice indicated the effect of tumors on normal liver RAS. The statistical significance of multiple comparisons was determined using one-way analysis of variance followed by Bonferroni adjustment with SAS/STAT software.

RESULTS

Reduced volume of CRC liver metastases with captopril treatment was evident. Local RAS of CRC metastases differed from the surrounding liver, with lower angiotensin II type 1 receptor (AT1R) expression but increased ANG-(1-7) receptor (MasR) compared to the liver. The AT1R localised to cancer and stromal infiltrating cells, while other RAS receptors were detected in cancer cells only. Tumor induction led to an initial increase in AT1R and ACE expression while captopril treatment significantly increased ACE expression in the final stages of tumor growth. Conversely, captopril treatment decreased expression of AT1R and angiotensinogen.

CONCLUSIONS

These results demonstrate significant changes in RAS expression in the tumor-bearing captopril treated liver and in CRC metastases. The data suggests the existence of a tumor-specific RAS that can be independently targeted by RAS blockade.

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.

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.

Bladder cancer-associated gene expression signatures identified by profiling of exfoliated urothelia

Bladder cancer is the fifth most commonly diagnosed malignancy in the United States and one of the most prevalent worldwide. It harbors a probability of recurrence of >50%; thus, rigorous, long-term surveillance of patients is advocated. Flexible cystoscopy coupled with voided urine cytology is the primary diagnostic approach, but cystoscopy is an uncomfortable, invasive procedure and the sensitivity of voided urine cytology is poor in all but high-grade tumors. Thus, improvements in noninvasive urinalysis assessment strategies would benefit patients. We applied gene expression microarray analysis to exfoliated urothelia recovered from bladder washes obtained prospectively from 46 patients with subsequently confirmed presence or absence of bladder cancer. Data from microarrays containing 56,000 targets was subjected to a panel of statistical analyses to identify bladder cancer-associated gene signatures. Hierarchical clustering and supervised learning algorithms were used to classify samples on the basis of tumor burden. A differentially expressed geneset of 319 gene probes was associated with the presence of bladder cancer (P < 0.01), and visualization of protein interaction networks revealed vascular endothelial growth factor and angiotensinogen as pivotal factors in tumor cells. Supervised machine learning and a cross-validation approach were used to build a 14-gene molecular classifier that was able to classify patients with and without bladder cancer with an overall accuracy of 76%. Our results show that it is possible to achieve the detection of bladder cancer using molecular signatures present in exfoliated tumor urothelia. Further investigation and validation of the cancer-associated profiles may reveal important biomarkers for the noninvasive detection and surveillance of bladder cancer.

Potential role of Renin-Angiotensin-system for tumor angiogenesis in receptor negative breast cancer

OBJECTIVE

This study examined the potential role of Angiotensin II for the regulation of angiogenesis associated genes in receptor positive and negative human breast cancer.

METHODS

Expression of different Renin-Angiotensin system (RAS) components in human breast cancer tissue was investigated using immunofluorescence, and in a receptor positive (MCF-7) and receptor negative (MDA-MB 468) breast cancer cell line by performing immunocytochemistry and RT-PCR. Both cell lines were stimulated with Angiotensin II and Angiotensin II receptor type 1 (At(1)R) blocker Candesartan, and gene expression of vascular endothelial growth factor (VEGF), Angiopoietin 1 and 2 (Ang-1 and Ang-2), tissue inhibitor of matrix metalloproteinases 1 (TIMP-1), and hypoxia inducible transcription factor 2alpha (HIF-2alpha) were quantified by TaqMan-Real-Time PCR analysis.

RESULTS

RAS components, Angiotensinogen, Renin, Angiotensin I-converting enzyme (ACE), and At(1)R and At(2)R were expressed in hormone-receptor negative and positive human breast cancer tissue as well as in MDA-MB 468 and in MCF-7 human breast cancer cells. In addition, we found expression of VEGF, Ang-1, TIMP-1, and HIF-2alpha in both cell lines. However, only in receptor negative MDA-MB 468 cells, did Angiotensin II significantly increase gene expression of VEGF, HIF-2alpha, and TIMP-1. This effect was completely inhibited by Candesartan.

CONCLUSION

In conclusion, it is hypothesized that Angiotensin II may be involved in regulation of tumor angiogenesis especially in receptor negative breast cancer by regulation of angiogenesis associated genes via At(1)R. These findings are the first evidence for targeting tumor angiogenesis by inhibition of At(1)R in receptor negative human breast cancer cells and may lead to new therapeutical anticancer strategies based upon inhibition of At(1)R.