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

An Insight into GPCR and G-Proteins as Cancer Drivers

G-protein-coupled receptors (GPCRs) are the largest family of cell surface signaling receptors known to play a crucial role in various physiological functions, including tumor growth and metastasis. Various molecules such as hormones, lipids, peptides, and neurotransmitters activate GPCRs that enable the coupling of these receptors to highly specialized transducer proteins, called G-proteins, and initiate multiple signaling pathways. Integration of these intricate networks of signaling cascades leads to numerous biochemical responses involved in diverse pathophysiological activities, including cancer development. While several studies indicate the role of GPCRs in controlling various aspects of cancer progression such as tumor growth, invasion, migration, survival, and metastasis through its aberrant overexpression, mutations, or increased release of agonists, the explicit mechanisms of the involvement of GPCRs in cancer progression is still puzzling. This review provides an insight into the various responses mediated by GPCRs in the development of cancers, the molecular mechanisms involved and the novel pharmacological approaches currently preferred for the treatment of cancer. Thus, these findings extend the knowledge of GPCRs in cancer cells and help in the identification of therapeutics for cancer patients.

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.

Inflammation and NF-κB Signaling in Prostate Cancer: Mechanisms and Clinical Implications

Prostate cancer is a highly prevalent form of cancer that is usually slow-developing and benign. Due to its high prevalence, it is, however, still the second most common cause of death by cancer in men in the West. The higher prevalence of prostate cancer in the West might be due to elevated inflammation from metabolic syndrome or associated comorbidities. NF-κB activation and many other signals associated with inflammation are known to contribute to prostate cancer malignancy. Inflammatory signals have also been associated with the development of castration resistance and resistance against other androgen depletion strategies, which is a major therapeutic challenge. Here, we review the role of inflammation and its link with androgen signaling in prostate cancer. We further describe the role of NF-κB in prostate cancer cell survival and proliferation, major NF-κB signaling pathways in prostate cancer, and the crosstalk between NF-κB and androgen receptor signaling. Several NF-κB-induced risk factors in prostate cancer and their potential for therapeutic targeting in the clinic are described. A better understanding of the inflammatory mechanisms that control the development of prostate cancer and resistance to androgen-deprivation therapy will eventually lead to novel treatment options for patients.

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.

Bioactive natural products for chemoprevention and treatment of castration-resistant prostate cancer

Prostate cancer (PCa), a hormonally-driven cancer, ranks first in incidence and second in cancer related mortality in men in most Western industrialized countries. Androgen and androgen receptor (AR) are the dominant modulators of PCa growth. Over the last two decades multiple advancements in screening, treatment, surveillance and palliative care of PCa have significantly increased quality of life and survival following diagnosis. However, over 20% of patients initially diagnosed with PCa still develop an aggressive and treatment-refractory disease. Prevention or treatment for hormone-refractory PCa using bioactive compounds from marine sponges, mushrooms, and edible plants either as single agents or as adjuvants to existing therapy, has not been clinically successful. Major advancements have been made in the identification, testing and modification of the existing molecular structures of natural products. Additionally, conjugation of these compounds to novel matrices has enhanced their bio-availability; a big step towards bringing natural products to clinical trials. Natural products derived from edible plants (nutraceuticals), and common folk-medicines might offer advantages over synthetic compounds due to their broader range of targets, as compared to mostly single target synthetic anticancer compounds; e.g. kinase inhibitors. The use of synthetic inhibitors or antibodies that target a single aberrant molecule in cancer cells might be in part responsible for emergence of treatment refractory cancers. Nutraceuticals that target AR signaling (epigallocatechin gallate [EGCG], curcumin, and 5α-reductase inhibitors), AR synthesis (ericifolin, capsaicin and others) or AR degradation (betulinic acid, di-indolyl diamine, sulphoraphane, silibinin and others) are prime candidates for use as adjuvant or mono-therapies. Nutraceuticals target multiple pathophysiological mechanisms involved during cancer development and progression and thus have potential to simultaneously inhibit both prostate cancer growth and metastatic progression (e.g., inhibition of angiogenesis, epithelial-mesenchymal transition (EMT) and proliferation). Given their multi-targeting properties along with relatively lower systemic toxicity, these compounds offer significant therapeutic advantages for prevention and treatment of PCa. This review emphasizes the potential application of some of the well-researched natural compounds that target AR for prevention and therapy of PCa.

G protein-coupled receptors as promising cancer targets

G protein-coupled receptors (GPCRs) regulate an array of fundamental biological processes, such as growth, metabolism and homeostasis. Specifically, GPCRs are involved in cancer initiation and progression. However, compared with the involvement of the epidermal growth factor receptor in cancer, that of GPCRs have been largely ignored. Recent findings have implicated many GPCRs in tumorigenesis, tumor progression, invasion and metastasis. Moreover, GPCRs contribute to the establishment and maintenance of a microenvironment which is permissive for tumor formation and growth, including effects upon surrounding blood vessels, signaling molecules and the extracellular matrix. Thus, GPCRs are considered to be among the most useful drug targets against many solid cancers. Development of selective ligands targeting GPCRs may provide novel and effective treatment strategies against cancer and some anticancer compounds are now in clinical trials. Here, we focus on tumor related GPCRs, such as G protein-coupled receptor 30, the lysophosphatidic acid receptor, angiotensin receptors 1 and 2, the sphingosine 1-phosphate receptors and gastrin releasing peptide receptor. We also summarize their tissue distributions, activation and roles in tumorigenesis and discuss the potential use of GPCR agonists and antagonists in cancer therapy.

Renin-Angiotensin Inhibitors Decrease Recurrence after Transurethral Resection of Bladder Tumor in Patients with Nonmuscle Invasive Bladder Cancer

PURPOSE

Prior reports suggest that renin-angiotensin system inhibition may decrease nonmuscle invasive bladder cancer recurrence. We evaluated whether angiotensin converting enzyme inhibitor or angiotensin receptor blocker treatment at initial surgery was associated with decreased recurrence or progression in patients with nonmuscle invasive bladder cancer.

MATERIALS AND METHODS

Using an institutional bladder cancer database we identified 340 patients with data available on initial transurethral resection of bladder tumor. Progression was defined as an increase to stage T2. Cox proportional hazards models were used to evaluate associations with recurrence-free and progression-free survival.

RESULTS

Median patient age was 69.6 years. During a median followup of 3 years (IQR 1.3-6.1) 200 patients (59%) had recurrence and 14 (4.1%) had stage progression. Of those patients 143 were receiving angiotensin converting enzyme inhibitor/angiotensin receptor blockers at the time of the first transurethral resection. On univariate analysis factors associated with improved recurrence-free survival included carcinoma in situ (p = 0.040), bacillus Calmette-Guérin therapy (p = 0.003) and angiotensin converting enzyme inhibitor/angiotensin receptor blocker therapy (p = 0.009). Multivariate analysis demonstrated that patients treated with bacillus Calmette-Guérin therapy (HR 0.68, 95% CI 0.47-0.87, p = 0.002) or angiotensin converting enzyme inhibitor/angiotensin receptor blocker therapy (HR 0.61, 95% CI 0.45-0.84, p = 0.005) were less likely to experience tumor recurrence. The 5-year recurrence-free survival rate was 45.6% for patients treated with angiotensin converting enzyme inhibitor/angiotensin receptor blockers and 28.1% in those not treated with angiotensin converting enzyme inhibitor/angiotensin receptor blockers (p = 0.009). Subgroup analysis was performed to evaluate nonmuscle invasive bladder cancer pathology (Ta, T1 and carcinoma in situ) in 85 patients on bacillus Calmette-Guérin therapy alone and in 52 in whom it was combined with angiotensin converting enzyme inhibitor/angiotensin receptor blocker. Multivariate analysis revealed that patients treated with bacillus Calmette-Guérin alone (HR 2.19, 95% CI 1.01-4.77, p = 0.04) showed worse recurrence-free survival compared to patients treated with bacillus Calmette-Guérin and angiotensin converting enzyme inhibitor/angiotensin receptor blocker (stage Ta HR 0.45, 95% CI 0.21-0.98, p = 0.04).

CONCLUSIONS

Pharmacological inhibition of the renin-angiotensin system is associated with improved outcomes in patients with bladder cancer. Renin-angiotensin system inhibitor administration in nonmuscle invasive bladder cancer cases should be studied in a prospective randomized trial.

The evaluation of involvement of angiotensin II, its receptors, and androgen receptor in endometrial cancer

Endometrial cancer (EC) is the most common gynecological malignancy. Alterations of angiogenic factors including angiotensin (AngII) or VEGF are observed in EC. Expression of angiotensin receptor 1 (AT1) is correlated with EC. Moreover, the expression of VEGF is up-regulated by AngII. Androgens are involved in the pathogenesis of EC. Genetic variations in androgen receptor (AR) gene may increase EC risk. This review proved strong correlation among EC, AngII, its receptors and AR, where AT influence on AR and, as a result, induce the expression of genes related to carcinogenesis.

Beyond androgen deprivation: ancillary integrative strategies for targeting the androgen receptor addiction of prostate cancer

The large majority of clinical prostate cancers remain dependent on androgen receptor (AR) activity for proliferation even as they lose their responsiveness to androgen deprivation or antagonism. AR activity can be maintained in these circumstances by increased AR synthesis--often reflecting increased NF-κB activation; upregulation of signaling pathways that promote AR activity in the absence of androgens; and by emergence of AR mutations or splice variants lacking the ligand-binding domain, which render the AR constitutively active. Drugs targeting the N-terminal transactivating domain of the AR, some of which are now in preclinical development, can be expected to inhibit the activity not only of unmutated ARs but also of the mutant forms and splice variants selected for by androgen deprivation. Concurrent measures that suppress AR synthesis or boost AR turnover could be expected to complement the efficacy of such drugs. A number of nutraceuticals that show efficacy in prostate cancer xenograft models--including polyphenols from pomegranate, grape seed, and green tea, the crucifera metabolite diindolylmethane, and the hormone melatonin--have the potential to suppress AR synthesis via downregulation of NF-κB activity; clinical doses of salicylate may have analogous efficacy. The proteasomal turnover of the AR is abetted by diets with a high ratio of long-chain omega-3 to omega-6 fatty acids, which are beneficial in prostate cancer xenograft models; berberine and sulforaphane, by inhibiting AR's interaction with its chaperone Hsp90, likewise promote AR proteasomal degradation and retard growth of human prostate cancer in nude mice. Hinge region acetylation of the AR is required for optimal transactivational activity, and low micromolar concentrations of the catechin epigallocatechin-3-gallate (EGCG) can inhibit such acetylation--possibly explaining the ability of EGCG administration to suppress androgenic activity and cell proliferation in prostate cancer xenografts. Hence, it is proposed that regimens featuring an N-terminal domain-targeting drug, various nutraceuticals/drugs that downregulate NF-κB activity, and/or supplemental intakes of fish oil, berberine, sulforaphane, and EGCG have potential for blocking proliferation of prostate cancer by targeting its characteristic addiction to androgen receptor activity.

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.

Angiotensinogen promoter polymorphisms predict low diffusing capacity in U.S. and Spanish IPF cohorts

BACKGROUND

Single nucleotide polymorphisms (SNPs) in angiotensinogen (AGT) at positions -20 and -6 are associated with increased severity and progression of various fibrotic diseases. Our earlier work demonstrated that the progression of idiopathic pulmonary fibrosis (IPF) was associated with the A-6 allele. This study examined the hypothesis that the homozygous CC genotype at -20 and the AA genotype at -6 would confer worse measures of pulmonary function (measured by pulmonary function tests) in IPF.

METHODS

Multiple logistic regression analysis was applied to a NIH Lung Tissue Research Consortium cohort and a Spanish cohort, while also adjusting for covariates to determine the effects of these SNPs on measures of pulmonary function.

RESULTS

Analysis demonstrated that the CC genotype at -20 was strongly associated with reduced diffusing capacity in males in both cohorts (p = 0.0028 for LTRC and p = 0.017 for the Spanish cohort). In females, the AA genotype was significantly associated with lower FVC (p = 0.0082) and V alv (p = 0.022). In males, the haplotype CA at -20 and -6 in AGT was also strongly associated with reduced diffusing capacity in both cohorts.

CONCLUSIONS

This study is the first to demonstrate an association of AGT polymorphisms (-20A > C and -6G > A) with lower measures of pulmonary function in IPF. It is also the first to relate the effect of gender in lung fibrosis with polymorphisms in AGT.

Angiotensin receptor blockers and risk of prostate cancer among United States veterans

To address concerns regarding increased risk of prostate cancer (PrCA) among angiotensin receptor blocker (ARB) users, we used national retrospective data from the Department of Veterans Affairs (VA) through the Veterans Affairs Informatics and Computing Infrastructure. We identified a total of 543,824 unique Veterans who were classified into either ARB treated or not-treated in 1:15 ratio. The two groups were balanced using inverse probability of treatment weights. A double-robust cox-proportional hazards model was used to estimate the hazard ratio for PrCA incidence. To evaluate for a potential Gleason score stage migration, we conducted weighted Cochrane-Armitage test. Post weighting, the rates of PrCA in treated and not-treated groups were 506 (1.5%) and 8,269 (1.6%), respectively; representing a hazard ratio of (0.91, p-value .049). There was no significant difference in Gleason scores between the two groups. We found a small, but statistically significant, reduction in the incidence of clinically detected PrCA among patients assigned to receive ARB with no countervailing effect on degree of differentiation (as indicated by Gleason score). Findings from this study support Food and Drug Administration's recent conclusion that ARB use does not increase risk of incident PrCA.

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.

Androgen receptor is up-regulated by a BLT2-linked pathway to contribute to prostate cancer progression

The androgen receptor (AR) plays a central role in the development and progression of prostate cancer. AR expression is maintained throughout the progression of prostate cancer and is also associated with an aggressive, castration-resistant (CR) phenotype. Despite the critical roles of AR expression in prostate cancer progression, the exact signaling mechanism regulating AR expression remains unclear. In this study, we demonstrated that AR expression was increased by a low-affinity leukotriene B(4) receptor (BLT2)-linked pathway. We found that BLT2 was overexpressed in AR-positive prostate cancer cells, such as LNCaP cells, and BLT2 inhibition, using an inhibitor or siRNA knockdown, clearly attenuated AR expression and triggered apoptosis in these cells. These results suggest a role for BLT2 in AR expression and the survival of AR-positive prostate cancer cells. Moreover, we found that the NADPH oxidase family protein, Nox4, lay downstream of BLT2 and mediated the production of reactive oxygen species (ROS) and subsequent NF-κB stimulation, thereby inducing AR expression. Taken together, our results demonstrate that BLT2 plays a critical role in AR expression via a Nox4-ROS-NF-κB-linked pathway, thereby mediating the survival of AR-positive prostate cancer cells. Our findings point to BLT2 as a key regulator of AR expression and will contribute to the development of novel therapies for AR-positive prostate cancers, including androgen-responsive and CR prostate cancers.

GPCRs and cancer

G-protein-coupled receptors (GPCRs), which represent the largest gene family in the human genome, play a crucial role in multiple physiological functions as well as in tumor growth and metastasis. For instance, various molecules like hormones, lipids, peptides and neurotransmitters exert their biological effects by binding to these seven-transmembrane receptors coupled to heterotrimeric G-proteins, which are highly specialized transducers able to modulate diverse signaling pathways. Furthermore, numerous responses mediated by GPCRs are not dependent on a single biochemical route, but result from the integration of an intricate network of transduction cascades involved in many physiological activities and tumor development. This review highlights the emerging information on the various responses mediated by a selected choice of GPCRs and the molecular mechanisms by which these receptors exert a primary action in cancer progression. These findings provide a broad overview on the biological activity elicited by GPCRs in tumor cells and contribute to the identification of novel pharmacological approaches for cancer patients.

Regulation of monocyte chemoattractant protein-1 through angiotensin II type 1 receptor in prostate cancer

Monocyte chemoattractant protein-1 (MCP-1/CCL2) is reported to contribute to tumor progression and is regulated by the renin-angiotensin system in hypertensive disease. In this study, we investigated the clinical outcome of MCP-1 expression in patients with prostate cancer (CaP) and the regulation of MCP-1 through angiotensin II (AngII) type 1 receptor (AT1R) in CaP. Specimens were obtained from 138 CaP patients and analyzed by immunostaining for both MCP-1 and macrophages. We investigated the regulation of MCP-1 expression through AT1R both in vivo and in vitro using three human prostate cancer cell lines: LNCaP, C4-2, and C4-2AT6. Specimens with a high Gleason score (≥7) and a high pathological classification (≤pT3), and those with castration-resistant prostate cancer showed significantly higher MCP-1 expression and higher macrophage infiltration than low malignant potential CaP. High MCP-1 expression in CaP correlated significantly with high prostate-specific antigen (PSA) recurrence rates. AngII induced significantly higher MCP-1 levels in C4-2AT6 than in LNCaP, whereas AT1R blockade (ARB) inhibited MCP-1 production via the inhibition of the PI3K/Akt pathway in C4-2AT6. ARB also significantly suppressed MCP-1 expression in C4-2AT6 tumors. Our study is the first to demonstrate that both high MCP-1 expression and high macrophage infiltration in CaP specimens correlate with a high PSA recurrence rate and that ARB inhibits MCP-1 expression through the PI3K/Akt pathway and blocks macrophage infiltration in castration-resistant prostate cancer.

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.

Increased androgen receptor transcription: a cause of castration-resistant prostate cancer and a possible therapeutic target

Few effective therapies exist for the treatment of castration-resistant prostate cancer (CRPC). Recent evidence suggests that CRPC may be caused by augmented androgen/androgen receptor (AR) signaling, generally involving AR overexpression. Aberrant androgen/AR signaling associated with AR overexpression also plays a key role in prostate carcinogenesis. Although AR overexpression could be attributed to gene amplification, only 10-20% of CRPCs exhibit AR gene amplification, and aberrant AR expression in the remaining instances of CRPC is thought to be attributed to transcriptional, translational, and post-translational mechanisms. Overexpression of AR at the protein level, as well as the mRNA level, has been found in CRPC, suggesting a key role for transcriptional regulation of AR expression. Since the analysis of the AR promoter region in the 1990s, several transcription factors have been reported to regulate AR transcription. In this review, we discuss the molecules involved in the control of AR gene expression, with emphasis on its transcriptional control by transcription factors in prostate cancer. We also consider the therapeutic potential of targeting AR expression.