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

Elucidating the Role of Pro-renin Receptors in Pancreatic Ductal Adenocarcinoma Progression: A Novel Therapeutic Target in Cancer Therapy

Pancreatic cancer is a highly aggressive malignancy with a very poor prognosis. The 5- year survival in these patients is very low, and most patients develop drug resistance to current therapies, so additional studies are needed to identify the potential role of new drug targets for the treatment of pancreatic cancer. Recent investigations have been performed regarding the roles of pro-renin receptors (PRR) in the initiation and development of cancers. PRR is a component of the local renin-angiotensin system (RAS). Local tissue RAS has been known in diverse organ systems, including the pancreas. Various investigations have implicated that PRRs are associated with the upregulation of various signaling pathways, like the renin-angiotensin system pathway, PI3K/Akt/mTOR, and the Wnt-signaling pathways, to contribute to pathological conditions, including cancer. In this review, we presented an overview of the role of PRR in the progression of pancreatic adenocarcinoma.

Cellular senescence triggers intracellular acidification and lysosomal pH alkalinized via ATP6AP2 attenuation in breast cancer cells

Several chemotherapeutic drugs induce senescence in cancer cells; however, the mechanisms underlying intracellular pH dysregulation in senescent cells remain unclear. Adenosine triphosphatase H+ transporting accessory protein 2 (ATP6AP2) plays a critical role in maintaining pH homeostasis in cellular compartments. Herein, we report the regulatory role of ATP6AP2 in senescent breast cancer cells treated with doxorubicin (Doxo) and abemaciclib (Abe). A decline in ATP6AP2 triggers aberrant pH levels that impair lysosomal function and cause immune profile changes in senescent breast cancer cells. Doxo and Abe elicited a stable senescent phenotype and altered the expression of senescence-related genes. Additionally, senescent cells show altered inflammatory and immune transcriptional profiles due to reprogramming of the senescence-associated secretory phenotype. These findings elucidate ATP6AP2-mediated cellular pH regulation and suggest a potential link in immune profile alteration during therapy-induced senescence in breast cancer cells, providing insights into the mechanisms involved in the senescence response to anticancer therapy.

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.

Targeting the (pro)renin receptor in cancers: from signaling to pathophysiological effects

Cancer is a major public health problem, currently affecting hundreds of millions of people worldwide, and its clinical results are unpredictable, partly due to the lack of reliable biomarkers of cancer progression. Recently, it has been reported that (pro)renin receptor (PRR), as a new biomarker, plays an important role in different types of cancer, such as colorectal cancer, breast cancer, glioma, aldosterone-producing adenoma, endometrial cancer, urothelial cancer, and pancreatic ductal adenocarcinoma. In order to comprehensively and systematically understand the relationship and role of PRR with various cancers, this review will summarize the current research on targeting PRR in cancer from signaling to pathophysiological effects, including the correlation between PRR/sPRR expression level and different cancers, potential mechanisms regulated by PRR in the progress of cancers, and PRR in cancer treatment. PRR can be a novel and promising biomarker and potential therapeutic target for diagnosis, treatment, and prognosis in cancer, which is worthy of extensive development and application in clinics.

(Pro)renin receptor and insulin signaling regulate cell proliferation in MCF-7 breast cancer cells

(Pro)renin receptor [(P)RR] is related to both the renin-angiotensin system and V-ATPase with various functions including stimulation of cell proliferation. (P)RR is implicated in the pathophysiology of diabetes mellitus and cancer. Hyperinsulinemia is observed in obesity-related breast cancer. However, the relationship between (P)RR and insulin has not been clarified. We have therefore studied the effect of insulin on (P)RR expression, cell viability, and AKT phosphorylation under the conditions with and without (P)RR knockdown. Effects of insulin were studied in a human breast cancer cell line, MCF-7. Cell proliferation assay was performed by WST-8 assay. (P)RR expression was suppressed by (P)RR-specific siRNAs. The treated cells were analyzed by western blotting and real-time quantitative PCR analysis. Insulin stimulated proliferation of MCF-7 cells and increased (P)RR protein expression, but not (P)RR mRNA levels. Moreover, autophagy flux was suppressed by insulin. Suppression of (P)RR expression reduced cell number of MCF-7 cells and AKT phosphorylation significantly in both the presence and the absence of insulin, indicating that (P)RR is important for cell viability and AKT phosphorylation. In conclusion, insulin upregulates the level of (P)RR protein, which is important for cell viability, proliferation, AKT phosphorylation, and autophagy in breast cancer cells.

(Pro)renin Receptor Is a Novel Independent Prognostic Marker in Invasive Urothelial Carcinoma of the Bladder

Simple Summary

This is a novel description of (Pro)renin receptor (PRR) protein and its prognostic role in invasive urothelial cancer of the bladder. Using a tissue microarray, we investigated PRR expression and other immunohistochemical markers including p53, immune-checkpoint inhibition, and basal and luminal phenotypes in a series of patients with invasive urothelial carcinoma of the bladder treated with radical cystectomy. PRR expression is an independent prognostic marker and could be a potential target in urothelial carcinoma that should be further investigated.

Abstract

(Pro)renin receptor (PRR) is being investigated in several malignancies as it activates pathogenic pathways that contribute to cell proliferation, immunosuppressive microenvironments, and acquisition of aggressive neoplastic phenotypes. Its implication in urothelial cancer (UC) has not been evaluated so far. We retrospectively evaluate the prognostic role of PRR expression in a series of patients with invasive UC treated with radical cystectomy and other clinical and histopathological parameters including p53, markers of immune-checkpoint inhibition, and basal and luminal phenotypes evaluated by tissue microarray. Cox regression analyses using stepwise selection evaluated candidate prognostic factors and disease-specific survival. PRR was expressed in 77.3% of the primary tumors and in 70% of positive lymph nodes. PRR expression correlated with age (p = 0.006) and was associated with lower preoperatively hemoglobin levels. No other statistical association was evidenced with clinical and pathological variables (gender, ASA score, Charlson comorbidity index, grade, pT, pN) or immunohistochemical expressions evaluated (CK20, GA-TA3, CK5/6, CD44, PD-L1, PD-1, B7-H3, VISTA, and p53). PRR expression in primary tumors was associated with worse survival (log-rank, p = 0.008). Cox regression revealed that PRR expression (HR 1.85, 95% CI 1.22–2.8), pT (HR 7.02, 95% CI 2.68–18.39), pN (HR 2.3, 95% CI 1.27–4.19), and p53 expression (HR 1.95, 95% CI 1.1–3.45) were independent prognostic factors in this series. In conclusion, we describe PRR protein and its prognostic role in invasive UC for the first time. Likely mechanisms involved are MAPK/ERK activation, Wnt/β-catenin signaling, and v-ATPAse function.

Elevated (Pro)renin Receptor Expression by Anti-Cancer Drugs, Carboplatin and Paclitaxel, in Cultured Cancer Cells: Possible Involvement of Apoptosis and Autophagy

(Pro)renin receptor [(P)RR] is a component of the renin-angiotensin system and plays an essential role in the activity of vacuolar H⁺-ATPase and autophagy. (P)RR is expressed in cancer cells. However, the relationship among (P)RR, apoptosis and autophagy in the treatment of anti-cancer drugs has not been clarified. The aim of this study was to clarify the effects of anti-cancer drugs with autophagy-promoting activity on (P)RR expression in cancer cells. MCF-7 breast cancer cells and A549 lung cancer cells were treated with carboplatin or paclitaxel, and the expression of (P)RR, apoptosis markers and autophagy markers were assessed by RT-qPCR, western blot analysis and immunocytochemistry. Expression levels of (P)RR mRNA and soluble (P)RR protein were increased by carboplatin or paclitaxel in a dose-dependent manner. Immunofluorescence staining of (P)RR was increased in both MCF-7 and A549 cells treated by carboplatin or paclitaxel. Apoptosis induction was shown by elevated BAX/BCL2 mRNA levels and increased active caspase3-positive cells. Moreover, autophagy induction was confirmed by increased levels of autophagy-associated mRNAs and LC3B-II proteins. (P)RR knockdown by (P)RR-specific siRNA suppressed the cell viability in MCF-7 cells and A549 cells under the treatment of carboplatin or paclitaxel, suggesting that (P)RR deficiency inhibits the proliferation of cancer cells in a pathway different from carboplatin or paclitaxel. The present study showed that the expression of (P)RR mRNA and soluble (P)RR was increased by anti-cancer drugs with autophagy-promoting activity. Upregulated (P)RR and autophagy may constitute a stress adaptation that protects cancer cells from apoptosis.

The Soluble (Pro)Renin Receptor in Health and Diseases: Foe or Friend?

The (pro)renin receptor (PRR) is a single-transmembrane protein that regulates the local renin-angiotensin system and participates in various intracellular signaling pathways, thus exhibiting a significant physiopathologic relevance in cellular homeostasis. A soluble form of PRR (sPRR) is generated through protease-mediated cleavage of the full-length PRR and secreted into extracellular spaces. Accumulating evidence indicates pivotal biologic functions of sPRR in various physiopathological processes. sPRR may be a novel biomarker for multiple diseases. SIGNIFICANCE STATEMENT: Circulating sPRR concentrations are elevated in patients and animals under various physiopathological conditions. This minireview highlights recent advances in sPRR functions in health and pathophysiological conditions. Results suggest that sPRR may be a novel biomarker for multiple diseases, but further studies are needed to determine the diagnostic value of sPRR.

Serum soluble (pro)renin receptor level as a prognostic factor in patients undergoing maintenance hemodialysis

The (pro)renin receptor [(P)RR)] is a multifunctional protein that is cleaved to generate the soluble (P)RR [s(P)RR], reflecting the status of the tissue renin-angiotensin system and/or activity of the (P)RR. The serum s(P)RR level is associated with arteriosclerosis, independent of other risk factors, in patients undergoing hemodialysis (HD). This study was conducted to investigate whether the s(P)RR level was associated with new-onset cardiovascular events or malignant diseases and poor prognosis in patients undergoing HD. Overall, 258 patients [70 (61–76) years, 146 males] undergoing maintenance HD were prospectively followed up for 60 months. We investigated the relationships between s(P)RR levels and new-onset cardiovascular events/ malignant diseases and mortality during the follow-up period using Cox proportional hazard analyses. The cumulative incidence of new-onset cardiovascular events (P = 0.009) and deaths (P < 0.001), but not of malignant diseases, was significantly greater in patients with higher serum s(P)RR level (≥ 29.8 ng/ml) than in those with lower s(P)RR level (< 29.8 ng/ml). A high serum s(P)RR level was independently correlated with cardiovascular mortality (95% CI 1.001–1.083, P = 0.046). The serum s(P)RR level was associated with cardiovascular events and mortality, thus qualifying as a biomarker for identifying patients requiring intensive care.

Clinical Implications of (Pro)renin Receptor (PRR) Expression in Renal Tumours

(1) Background: Renal cancer is one of the most frequent malignancies in Western countries, with an unpredictable clinical outcome, partly due to its high heterogeneity and the scarcity of reliable biomarkers of tumour progression. (Pro)renin receptor (PRR) is a novel receptor of the renin–angiotensin system (RAS) that has been associated with the development and progression of some solid tumours by RAS-dependent and -independent mechanisms. (2) Methods: In this study, we analysed the immunohistochemical expression of PRR at the centre and border in a series of 83 clear-cell renal cell (CCRCCs), 19 papillary (PRCC) and 7 chromophobe (ChRCC) renal cell carcinomas, and the benign tumour renal oncocytoma (RO, n = 11). (3) Results: PRR is expressed in all the tumour subtypes, with higher mean staining intensity in ChRCCs and ROs. A high expression of PRR at the tumour centre and at the infiltrative front of CCRCC tissues is significantly associated with high grade, tumour diameter, local invasion and stage, and with high mortality risk by UCLA integrated staging system (UISS) scale. (4) Conclusions: These findings indicate that PRR is associated with the development and progression of renal tumours. Its potential as a novel biomarker for RCC diagnosis/prognosis and as a promising therapeutic target should be taken into account in the future.

(Pro)renin receptor/ATP6AP2 is required for autophagy and regulates proliferation in lung adenocarcinoma cells

(Pro)renin receptor ((P)RR)/ ATP6AP2 (ATPase, H⁺ transporting, lysosomal accessory protein 2) functions as an essential accessory subunit of vacuolar H⁺ -ATPase (V-ATPase). V-ATPase is necessary for lysosome function and autophagy. Autophagy is related to cell proliferation, migration and invasion of various cancer cells. In this study, we aim to clarify the relationship between (P)RR and autophagy in lung adenocarcinoma. Expression of (P)RR and Ki-67 (a proliferation marker) was studied in sixty-four adenocarcinoma cases by immunohistochemistry. Lung adenocarcinoma cell line, A549, was transfected with (P)RR-specific siRNA. Autophagy inhibitors, bafilomycin A1 and chloroquine, were used as positive controls. Cell proliferation and migration were measured by WST-8 assay and wound healing assay. Autophagosome markers, p62 and LC3, were analyzed by RT-qPCR, Western blot and immunocytochemistry. Immunohistochemistry showed that (P)RR was expressed in all adenocarcinoma tissues. The intensity of (P)RR immunoreactivity was significantly associated with Ki-67. Treatment of (P)RR-specific siRNA suppressed (P)RR expression and significantly reduced cell proliferation and migration as did the autophagy inhibitors. Western blot and immunocytochemistry showed that (P)RR-specific siRNA, as well as the autophagy inhibitors, induced p62 and LC3 accumulation in cytoplasmic granules. These results suggest that (P)RR is involved in cell proliferation and progression of lung adenocarcinoma via regulating autophagy.

ATP6AP2 is Overexpressed in Breast Cancer and Promotes Breast Cancer Progression

Background

Adenosine triphosphatase H+ transporting accessory protein 2 (ATP6AP2), also known as (pro)renin receptor, is implicated in tumorigenesis and the progression of several types of cancer. This study investigated the role of ATP6AP2 in breast cancer.

Methods

UALCAN and ONCOMINE datasets were utilized to compare transcript levels of ATP6AP2 in breast cancer and normal tissues. GOBO datasets were applied to examine ATP6AP2 expression in different breast cancer cell lines. We used the cBioPortal website to explore the gene alterations and copy number alterations of ATP6AP2 in breast cancer. Cell Counting Kit-8 and transwell assays were conducted to evaluate ATP6AP2 function in MCF-7 breast cancer cells. Finally, we used the cBioPortal website to establish the interaction network of ATP6AP2 in breast cancer and performed functional enrichment analysis based on Gene Ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways.

Results

ATP6AP2 was overexpressed in breast cancer tissues and breast cancer cell lines in the UALCAN, ONCOMINE, and GOBO datasets. The major type of ATP6AP2 alteration was mRNA upregulation. Moreover, ATP6AP2 was most highly expressed in luminal type breast cancer. Finally, ATP6AP2 knockdown reduced MCF-7 cell proliferation, invasion and migration. Functional enrichment analysis suggested that ATP6AP2 regulates several cancer-related pathways, especially the Wnt/β-catenin signaling pathway.

Conclusion

Applying multi-dimensional analytical methods, we demonstrate that ATP6AP2 is upregulated in breast cancer and may promote its development and progression.

Antiproliferative Effects of Monoclonal Antibodies against (Pro)Renin Receptor in Pancreatic Ductal Adenocarcinoma

We previously reported that silencing of the PRR gene, which encodes the (pro)renin receptor [(P)RR], significantly reduced Wnt/β-catenin-dependent development of pancreatic ductal adenocarcinoma (PDAC). Here, we examined the effects of a panel of blocking mAbs directed against the (P)RR extracellular domain on proliferation of the human PDAC cell lines PK-1 and PANC-1 in vitro and in vivo We observed that four rat anti-(P)RR mAbs induced accumulation of cells in the G₀-G₁-phase of the cell cycle and significantly reduced proliferation in vitro concomitant with an attenuation of Wnt/β-catenin signaling. Systemic administration of the anti-(P)RR mAbs to nude mice bearing subcutaneous PK-1 xenografts significantly decreased tumor expression of active β-catenin and the proliferation marker Ki-67, and reduced tumor growth. In contrast, treatment with the handle region peptide of (pro)renin did not inhibit tumor growth in vitro or in vivo, indicating that the effects of the anti-(P)RR mAbs were independent of the renin-angiotensin system. These data indicate that mAbs against human (P)RR can suppress PDAC cell proliferation by hindering activation of the Wnt/β-catenin signaling pathway. Thus, mAb-mediated (P)RR blockade could be an attractive therapeutic strategy for PDAC.

Increased soluble (pro)renin receptor protein by autophagy inhibition in cultured cancer cells

(Pro)renin receptor ((P)RR) regulates the renin-angiotensin system and functions as an essential accessory subunit of vacuolar H+ -ATPase. There is accumulating evidence that shows close relationship between (P)RR and autophagy. Soluble (P)RR consisting of the extracellular domain of (P)RR is generated from (P)RR by proteolytic enzymes. The aim of the present study was to clarify the influence of autophagy inhibition on soluble (P)RR expression in cancer cells. Autophagy was inhibited by treatment of bafilomycin A1 or chloroquine in MCF-7 and A549 cells for 72 hr. Western blot analysis showed that protein levels of soluble (P)RR were markedly elevated by autophagy inhibition, whereas no noticeable increases were observed in full-length (P)RR. Secretion of soluble (P)RR into the medium was increased dose-dependently by bafilomycin A1 or chloroquine. Autophagy inhibition was confirmed by enhanced accumulation of autophagy-related proteins, LC3, p62 and LAMP1 in intracellular vesicles. Increased amount of soluble (P)RR by autophagy inhibition was decreased by site-1 protease inhibitor, whereas no noticeable increase in site-1 protease immunoreactivity was observed in cells with autophagy inhibition by immunocytochemistry. These findings suggest that soluble (P)RR protein accumulates by autophagy inhibition, possibly because of the reduced degradation of soluble (P)RR in the intracellular vesicles during autophagy inhibition.

The (pro)renin receptor: a novel biomarker and potential therapeutic target for various cancers

BACKGROUND

The (pro) renin receptor ((P)RR) plays important roles in various pathways, such as the Wnt/β-catenin, renin-angiotensin system (RAS), MAPK/ERK and PI3K/AKT/mTOR pathways, that are involved in a wide range of physiological and pathological processes incorporating the tumorigenesis. However, our knowledge about (P) RR was mostly limited to its roles in cardiovascular and renal physiological functions and diseases. In the past 5 years, however, compelling evidence has revealed that (P) RR is aberrantly expressed in and contributes to the development of various cancers by different means. For instance, (P) RR was recently demonstrated to induce the oncogenesis of pancreatic, colorectal and brain cancers via the Wnt signaling, while promote the endometrial cancer and glioblastoma through the RAS.

METHODS

Combining with the deep analysis of big data from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases, this review updates and summarizes the recent studies about the newly recognized roles of (P) RR in the pathophysiological processes of cancer development and its detailed functions through related pathways, as well as the novel research progress of (P) RR in related fields including the development and application of soluble (P) RR detection kit and monoclonal (P) RR antibody.

RESULTS

This review provides an overview of the essential roles of (P) RR in the tumorigenesis and progression of various cancers and offers a translational outlook for the future research and clinical practices.

CONCLUSION

(P) RR in the tumor tissues and/or body fluids of patients may be a novel and promising biomarker and potential therapeutic target for diagnosis, treatment and prognosis prediction in various cancers. Video Abstract.

Recent Research Advances in Renin-Angiotensin-Aldosterone System Receptors

PURPOSE OF REVIEW

The renin-angiotensin-aldosterone system (RAAS) plays important roles in regulating blood pressure and body fluid, which contributes to the pathophysiology of hypertension and cardiovascular/renal diseases. However, accumulating evidence has further revealed the complexity of this signal transduction system, including direct interactions with other receptors and proteins. This review focuses on recent research advances in RAAS with an emphasis on its receptors.

RECENT FINDINGS

Both systemically and locally produced angiotensin II (Ang II) bind to Ang II type 1 receptor (AT1R) and elicit strong biological functions. Recent studies have shown that Ang II-induced activation of Ang II type 2 receptor (AT2R) elicits the opposite functions to those of AT1R. However, accumulating evidence has now expanded the components of RAAS, including (pro)renin receptor, angiotensin-converting enzyme 2, angiotensin 1-7, and Mas receptor. In addition, the signal transductions of AT1R and AT2R are regulated by not only Ang II but also its receptor-associated proteins such as AT1R-associated protein and AT2R-interacting protein. Recent studies have indicated that inappropriate activation of local mineralocorticoid receptor contributes to cardiovascular and renal tissue injuries through aldosterone-dependent and -independent mechanisms. Since the mechanisms of RAAS signal transduction still remain to be elucidated, further investigations are necessary to explore novel molecular mechanisms of the RAAS, which will provide alternative therapeutic agents other than existing RAAS blockers.

The (pro)renin receptor in health and disease

The (pro)renin receptor ((P)RR) was first identified as a single-transmembrane receptor in human kidneys and initially attracted attention owing to its potential role as a regulator of the tissue renin-angiotensin system (RAS). Subsequent studies found that the (P)RR is widely distributed in organs throughout the body, including the kidneys, heart, brain, eyes, placenta and the immune system, and has multifaceted functions in vivo. The (P)RR has roles in various physiological processes, such as the cell cycle, autophagy, acid-base balance, energy metabolism, embryonic development, T cell homeostasis, water balance, blood pressure regulation, cardiac remodelling and maintenance of podocyte structure. These roles of the (P)RR are mediated by its effects on important biological systems and pathways including the tissue RAS, vacuolar H⁺-ATPase, Wnt, partitioning defective homologue (Par) and tyrosine phosphorylation. In addition, the (P)RR has been reported to contribute to the pathogenesis of diseases such as fibrosis, hypertension, pre-eclampsia, diabetic microangiopathy, acute kidney injury, cardiovascular disease, cancer and obesity. Current evidence suggests that the (P)RR has key roles in the normal development and maintenance of vital organs and that dysfunction of the (P)RR is associated with diseases that are characterized by a disruption of the homeostasis of physiological functions.

Juxtaglomerular Cell Tumor: Reviewing a Cryptic Cause of Surgically Correctable Hypertension

Juxtaglomerular cell tumor (JGCT), or reninoma, is a typically benign neoplasm generally affecting adolescents and young adults due to modified smooth muscle cells from the afferent arteriole of the juxtaglomerular apparatus. Patients experience symptoms related to hypertension and hypoka-lemia due to renin-secretion by the tumor. MRI, PET, CT, and renal vein catheterizations can be used to capture JGCTs, with laparoscopic ultrasonography being most cost-efective. Surgical removal is the best option for management; electrolyte imbalances are a potential complication which may be assuaged via pre-surgical administration of aliskiren, a renin inhibitor. Considering the vast etiology for hypertension and rarity of JGCT, the diagnosing physician must have a high index of suspicion for JGCT. Early recognition and management can help prevent cardiovascular or pregnancy complications and fatalities, vascular invasion and metastasis, improve quality of life, and limit socioeconomic liabilities. Herein we review the epidemiology, genetics, histopathol-ogy, clinical presentation, and management of this rare condition. The impact of genetics on prognosis warrant further research.

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

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

(Pro)renin receptor promotes colorectal cancer through the Wnt/beta-catenin signalling pathway despite constitutive pathway component mutations

Background

Although constitutive activating mutations in the Wnt/β-catenin signalling pathway are important for colorectal cancer development, canonical signalling through Wnt ligands is essential for β-catenin activation. Here, we investigated the role of (pro)renin receptor ((P)RR), a component of the Wnt receptor complex, in the pathogenesis of colorectal cancer.

Methods

(P)RR silencing was performed in human colorectal cancer cells containing constitutive activating mutations in the Wnt/β-catenin pathway. (P)RR overexpression was induced in normal colon epithelial cells. Protein and mRNA levels of pathway components were detected, and Wnt signalling activity was measured using a β-catenin reporter. Cell proliferative activity and apoptosis were evaluated using WST-1 assay and flow cytometry. Xenografts were induced in nude mice.

Results

(P)RR expression was greater in colorectal cancer tissues and cells than in normal colorectal samples. Patients with strong (P)RR expression took more proportion in groups with poorly-differentiated, advanced and rapidly-progressing cancers. (P)RR silencing attenuated the pathway in colorectal cancer cells, impaired their proliferation in vitro and vivo. (P)RR overexpression enhanced the pathway and proliferation of normal colon epithelial cells.

Conclusions

Aberrant (P)RR expression promotes colorectal cancer through the Wnt/β-catenin signalling pathway despite constitutive pathway-activating mutations. (P)RR is a potential diagnostic and therapeutic target for colorectal cancer.

Soluble (Pro)renin Receptor and Obstructive Sleep Apnea Syndrome: Oxidative Stress in Brain?

(Pro)renin receptor ((P)RR) is a multi-functional molecule that is related to both the renin-angiotensin system (RAS) and vacuolar H⁺-ATPase (v-ATPase), an ATP-dependent multi-subunit proton pump. Soluble (P)RR (s(P)RR), which consists of the extracellular domain of (P)RR, is present in blood and urine. Elevated plasma s(P)RR concentrations are reported in patients with chronic kidney disease and pregnant women with hypertension or diabetes mellitus. In addition, we have shown that plasma s(P)RR concentrations are elevated in patients with obstructive sleep apnea syndrome (OSAS). Interestingly, the levels are elevated in parallel with the severity of OSAS, but are not related to the presence of hypertension or the status of the circulating RAS in OSAS. It is known that v-ATPase activity protects cells from endogenous oxidative stress, and loss of v-ATPase activity results in chronic oxidative stress. We hypothesize that hypoxia and subsequent oxidative stress, perhaps in the brain, may be one of the factors that elevate plasma s(P)RR levels in OSAS.

(Pro)renin receptor is crucial for glioma development via the Wnt/β-catenin signaling pathway

OBJECTIVE The (pro)renin receptor (PRR) plays an essential role in the early development of the central nervous system by activating the Wnt/β-catenin signaling pathway. The authors investigated the potential role of the PRR in the pathogenesis of glioma. METHODS The authors performed immunohistochemical analysis to detect both the PRR and isocitrate dehydrogenase 1 with mutations involving arginine 132 ( IDH1^R132H) in paraffin sections of 31 gliomas. Expression of the PRR and Wnt pathway components in cultured human glioma cell lines (U251MG, U87MG, and T98G) was measured using Western blotting. The effects of PRR short interfering RNA (siRNA) on glioma cell proliferation (WST-1 assay and direct cell counting) and apoptosis (flow cytometry and the caspase-3 assay) were also examined. RESULTS PRR expression was significantly higher in glioblastoma than in normal tissue or in lower grade glioma, regardless of IDH1^R132H mutation. PRR expression was also higher in human glioblastoma cell lines than in human astrocytes. PRR expression showed a significant positive correlation with the Ki-67 labeling index, while it had a significant negative correlation with the survival time of glioma patients. Treatment with PRR siRNA significantly reduced expression of Wnt2, activated β-catenin, and cyclin D1 by human glioblastoma cell lines, and it reduced the proliferative capacity of these cell lines and induced apoptosis. CONCLUSIONS This is the first evidence that the PRR has an important role in development of glioma by aberrant activation of the Wnt/β-catenin signaling pathway. This receptor may be both a prognostic marker and a therapeutic target for glioma.

Ubiquitous expression and multiple functions of biologically active peptides

Biologically active peptides are widely expressed throughout in human bodies. For example, endothelin-1 and adrenomedullin are expressed in almost all types of cells, including neurons, glial cells, fibroblasts, macrophages, cardiomyocytes, vascular endothelial cells, epithelial cells and cancer cells of various origins. Expression of both these peptides is induced by stimuli, such as hypoxia and inflammatory cytokines. They have a variety of biological functions, such as effects on brain function, hormone secretion, the cardiovascular system and cell proliferation. By contrast, orexins (hypocretins) and melanin-concentrating hormone (MCH) are specifically expressed in the hypothalamus, particularly in the lateral hypothalamus, although very low concentrations of these peptides are found in the peripheral tissues. Orexins and MCH play coordinated, but distinct physiological roles in the regulation of sleep-wake cycle, appetite, emotion and other brain functions. The cardiovascular system is regulated by cardiovascular peptides, such as natriuretic peptides, endothelins and angiotensin II. The renin-angiotensin system (RAS) is one of the most classical regulatory systems on blood pressure, electrolytes and kidney. (Pro)renin receptor is a novel member of the RAS and may be related to the pathophysiology of microvascular complications of hypertension and diabetes mellitus. Moreover, (pro)renin receptor forms a functional complex with vacuolar-type H(+)-ATPase, which plays an important physiological role in maintaining the acidic environment of intracellular compartments including secretory vesicles. Perhaps, the complex of (pro)renin receptor and vacuolar-type H(+)-ATPase may be important for the post-translational processing and secretion of many biologically active peptides.