Renin angiotensin system-regulating aminopeptidase activities in serum of pre- and postmenopausal women with breast cancer

Extracting Knowledge from Machine Learning Models to Diagnose Breast Cancer

This study explored the application of explainable machine learning models to enhance breast cancer diagnosis using serum biomarkers, contrary to many studies that focus on medical images and demographic data. The primary objective was to develop models that are not only accurate but also provide insights into the factors driving predictions, addressing the need for trustworthy AI in healthcare. Several classification models were evaluated, including OneR, JRIP, the FURIA, J48, the ADTree, and the Random Forest, all of which are known for their explainability. The dataset included a variety of biomarkers, such as electrolytes, metal ions, marker proteins, enzymes, lipid profiles, peptide hormones, steroid hormones, and hormone receptors. The Random Forest model achieved the highest accuracy at 99.401%, followed closely by JRIP, the FURIA, and the ADTree at 98.802%. OneR and J48 achieved 98.204% accuracy. Notably, the models identified oxytocin as a key predictive biomarker, with most models featuring it in their rules. Other significant parameters included GnRH, β-endorphin, vasopressin, IRAP, and APB, as well as factors like iron, cholinesterase, the total protein, progesterone, 5-nucleotidase, and the BMI, which are considered clinically relevant to breast cancer pathogenesis. This study discusses the roles of the identified parameters in cancer development, thus underscoring the potential of explainable machine learning models for enhancing early breast cancer diagnosis by focusing on explainability and the use of serum biomarkers.The combination of both can lead to improved early detection and personalized treatments, emphasizing the potential of these methods in clinical settings. The identified markers also provide additional research and therapeutic targets for breast cancer pathogenesis and a deep understanding of their interactions, advancing personalized approaches to breast cancer management.

Novel Peptide-drug Conjugate Melflufen Efficiently Eradicates Bortezomib-resistant Multiple Myeloma Cells Including Tumor-initiating Myeloma Progenitor Cells

Introduction of the proteasome inhibitor bortezomib has dramatically improved clinical outcomes in multiple myeloma. However, most patients become refractory to bortezomib-based therapies. On the molecular level, development of resistance to bortezomib in myeloma cells is accompanied by complex metabolic changes resulting in increased protein folding capacity, and less dependency on the proteasome. In this study, we show that aminopeptidase B, encoded by the RNPEP gene, is upregulated in bortezomib-resistant myeloma cell lines, and in a murine in vivo model. Moreover, increased RNPEP expression is associated with shorter survival in multiple myeloma patients previously treated with bortezomib-containing regimens. Additionally, expression is increased in plasma cell precursors, a B-lymphoid compartment previously associated with myeloma stem cells. We hypothesized that increased aminopeptidase B expression in aggressive myeloma clones may be used therapeutically toward elimination of the cells via the use of a novel peptide-drug conjugate, melphalan flufenamide (melflufen). Melflufen, a substrate of aminopeptidase B, efficiently eliminates bortezomib-resistant myeloma cells in vitro and in vivo, and completely suppresses clonogenic myeloma growth in vitro at subphysiological concentrations. Thus, melflufen represents a novel treatment option that is able to eradicate drug-resistant myeloma clones characterized by elevated aminopeptidase B expression.

Sex differences exist in brain renin-angiotensin system-regulating aminopeptidase activities in transplacental ethyl-nitrosourea-induced gliomas

INTRODUCTION

The renin angiotensin system (RAS) is emerging as an important target for the treatment of glioma. We had described that the local RAS is involved in vivo in tumor growth in the rat model of experimental C6 glioma implanted at the subcutaneous region, through the modification of several proteolytic regulatory enzymes of aminopeptidase type.

METHODS

We analyze RAS-regulating aminopeptidase activities in plasma and brain tissue of control male and female rats and rats with transplacental ethylnitrosourea-induced gliomas.

RESULTS

No differences were found either the mean total number of tumors per animal or the tumor volume between male and female animals. However, we have found increased levels in aspartyl aminopeptidase in both males and females and of aminopeptidase B only in males. On the contrary, decreased levels were found in aminopeptidase N and insulin-regulated aminopeptidase activities in both males and females, whereas aminopeptidase A only decreased in females. Decreased levels of aminopeptidase N, aminopeptidase B and insulin-regulated aminopeptidase were also shown in plasma of only female rats.

CONCLUSIONS

Under the complexity of RAS cascade, the changes found suggest the predominant actions of angiotensin III against a decreased action of angiotensin II and angiotensin IV. We conclude that angiotensin peptides are involved in tumor growth in this rat model of glioma and that their role in tumor growth can be analyzed through their corresponding proteolytic regulatory enzymes, which make them new and attractive therapeutic targets beyond the use or angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs).

2020 update on the renin-angiotensin-aldosterone system in pediatric kidney disease and its interactions with coronavirus

The last decade was crucial for our understanding of the renin-angiotensin-aldosterone system (RAAS) as a two-axis, counter-regulatory system, divided into the classical axis, formed by angiotensin-converting enzyme (ACE), angiotensin II (Ang II), and the angiotensin type 1 receptor (AT1R), and the alternative axis comprising angiotensin-converting enzyme 2 (ACE2), angiotensin-(1-7) (Ang-(1-7)), and the Mas receptor. Breakthrough discoveries also took place, with other RAAS endopeptides being described, including alamandine and angiotensin A. In this review, we characterize the two RAAS axes and the role of their components in pediatric kidney diseases, including childhood hypertension (HTN), pediatric glomerular diseases, congenital abnormalities of the kidney and urinary tract (CAKUT), and chronic kidney disease (CKD). We also present recent findings on potential interactions between the novel coronavirus, SARS-CoV-2, and components of the RAAS, as well as potential implications of coronavirus disease 2019 (COVID-19) for pediatric kidney diseases.

Insulin-Regulated Aminopeptidase in Women with Breast Cancer: A Role beyond the Regulation of Oxytocin and Vasopressin

Simple Summary

Insulin-regulated aminopeptidase (IRAP) is a well-known enzyme involved mainly in the regulation of the peptide hormones, oxytocin and vasopressin. However, this enzyme activity has hardly been analyzed in breast cancer patients. Additionally, the influence of both the hormonal status (pre or postmenopause) and the administration of neoadjuvant chemotherapy have rarely been studied. We show that there is a weak association between IRAP activity and the circulating levels of peptide hormones with variations depending on the hormonal status and the neoadjuvant treatment, and propose a role beyond oxytocin and vasopressin regulation that is related to the local mammary renin-angiotensin system and glucose transportation to the cells.

Abstract

Insulin-regulated aminopeptidase (IRAP) is the only enzyme known to cleave oxytocin and vasopressin; however, it is also the high-affinity binding site for angiotensin IV (AngIV) receptor type 4 (AT4) ligands and it is related to insulin-dependent glucose transporters through the translocation of the glucose transporter type 4 (GLUT4). Previous studies have demonstrated an association between IRAP activity and the number and size of mammary tumors in an animal model of breast cancer (BC). Also, a highly significant increase in IRAP activity has been found in BC tissue from women patients. Here, we found no changes in circulating IRAP in premenopausal (preMP) women, but it increased significantly in postmenopausal (postMP) women not treated with neoadjuvant chemotherapy (NACH). However, in women treated with NACH, IRAP activity increased in both preMP and postMP women. Two years of follow-up indicated lower levels of IRAP activity in untreated preMP women, but a return to control levels in untreated postMP women, while IRAP activity returned to control levels in women treated with NACH. Circulating oxytocin decreased in both preMP and postMP women during the follow-up period. Differences in Oxytocin appeared between preMP and postMP women treated with NACH, but not in women who were not treated with NACH. On the contrary, circulating vasopressin increased in untreated and treated preMP and postMP women, with most of the differences related to the hormonal status as well as the neoadjuvant treatment during the two year follow-up We propose that IRAP is involved in mechanisms related not only to oxytocin and/or vasopressin regulation, but also to the local mammary RAS through AngIV and its role in glucose transportation through the IRAP/GLUT4 system.

Neoadjuvant chemotherapy modifies serum pyrrolidone carboxypeptidase specific activity in women with breast cancer and influences circulating levels of GnRH and gonadotropins

PURPOSE

Functional studies have demonstrated that gonadotropin-releasing hormone (GnRH) regulates cell proliferation, apoptosis, and tissue remodeling. GnRH is metabolized by the proteolytic regulatory enzyme pyrrolidone carboxypeptidase (Pcp) (E.C. 3.4.19.3), which is an omega peptidase widely distributed in fluids and tissues. We previously reported a decrease in both rat and human Pcp activity in breast cancer, suggesting that GnRH may be an important local hormonal factor in the pathogenesis of breast cancer. Recently, we have described that postmenopausal women with breast cancer show lower levels of serum Pcp activity than control postmenopausal women. To determine the effect of neoadjuvant chemotherapy (NACT) on serum Pcp specific activity and circulating levels of GnRH, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and steroid hormones 17-ß-estradiol and progesterone in pre- and postmenopausal women diagnosed with infiltrating ductal carcinoma.

METHODS

Serum Pcp activity was measured fluorometrically using pyroglutamyl-ß-naphthylamide. Circulating GnRH levels were dosed using a commercial RIA kit. Circulating LH and FSH levels were measured by enzyme immunoassays. Levels of steroid hormones were measured in serum samples by dissociation-enhanced lanthanide fluorescence immunoassay.

RESULTS AND CONCLUSION

Our results show the effect of NACT on the hypothalamic-pituitary axis, with the consequent alteration of circulating gonadotropins in premenopausal women with breast cancer. However, the results obtained in postmenopausal women with breast cancer treated with NACT, that is, the significant decrease in the concentration of GnRH and FSH compared to control postmenopausal women, differ from those obtained for premenopausal women. The only difference between pre- and postmenopausal women is their hormonal profile at the beginning of the study, that is, the presence of menopause and the consequent alteration of the hypothalamic-pituitary-gonadal axis.

N-Terminal Modification of the Tetrapeptide Arg-Leu-Tyr-Glu, a Vascular Endothelial Growth Factor Receptor-2 (VEGFR-2) Antagonist, Improves Antitumor Activity by Increasing its Stability against Serum Peptidases

The tetrapeptide Arg-Leu-Tyr-Glu (RLYE), a vascular endothelial growth factor (VEGF) receptor-2 antagonist, has been used previously either alone or in combination with chemotherapeutic drugs for treating colorectal cancer in a mouse model. We analyzed the half-life of the peptide and found that because of degradation by aminopeptidases B and N, it had a short half-life of 1.2 hours in the serum. Therefore, to increase the stability and potency of the peptide, we designed the modified peptide, N-terminally acetylated RLYE (Ac-RLYE), which had a strongly stabilized half-life of 8.8 hours in serum compared with the original parent peptide. The IC50 value of Ac-RLYE for VEGF-A-induced endothelial cell migration decreased to approximately 37.1 pM from 89.1 pM for the parent peptide. Using a mouse xenograft tumor model, we demonstrated that Ac-RLYE was more potent than RLYE in inhibiting tumor angiogenesis and growth, improving vascular integrity and normalization through enhanced endothelial cell junctions and pericyte coverage of the tumor vasculature, and impeding the infiltration of macrophages into tumor and their polarization to the M2 phenotype. Furthermore, combined treatment of Ac-RLYE and irinotecan exhibited synergistic effects on M1-like macrophage activation and apoptosis and growth inhibition of tumor cells. These findings provide evidence that the N-terminal acetylation augments the therapeutic effect of RLYE in solid tumors via inhibition of tumor angiogenesis, improvement of tumor vessel integrity and normalization, and enhancement of the livery and efficacy of the coadministered chemotherapeutic drugs. SIGNIFICANCE STATEMENT: The results of this study demonstrate that the N-terminal acetylation of the tetrapeptide RLYE (Ac-RLYE), a novel vascular endothelial growth factor receptor-2 (VEGFR-2) inhibitor, significantly improves its serum stability, antiangiogenic activity, and vascular normalizing potency, resulting in enhanced therapeutic effect on solid tumors. Furthermore, the combined treatment of Ac-RLYE with the chemotherapeutic drug, irinotecan, synergistically enhanced its antitumor efficacy by improving the perfusion and delivery of the drug into the tumors and stimulating the conversion of the tumor-associated macrophages to an immunostimulatory M1-like antitumor phenotype.

Aspartyl Aminopeptidase Suppresses Proliferation, Invasion, and Stemness of Breast Cancer Cells via Targeting CD44

Although involved in diverse cancer processes, the function of aspartyl aminopeptidase (DNPEP) in breast cancer remains elusive. Here, we reported that DNPEP is significantly downregulated in breast cancer tissues. Overexpression of DNPEP resulted in decreased breast cancer cells proliferation, migration, and invasion, while DNPEP knockdown had the opposite effect. Interestingly, we showed that the reduced DNPEP levels were correlated with the elevated cluster of differentiation 44 (CD44) levels in breast cancer. DNPEP promoted CD44 ubiquitin-proteasome-independent degradation, which is dependent on the hydrolase activity of DNPEP. Ectopic DNPEP expression significantly suppressed the stemness properties of breast cancer cells. These results shed light on the prospect of DNPEP in manipulating breast cancer progression. Anat Rec, 302:2178-2185, 2019. © 2019 American Association for Anatomy.

Effects on estrogen-dependent and triple negative breast cancer cells growth of Ni(II), Zn(II) and Cd(II) complexes with the Schiff base derived from pyridine-2-carboxaldehyde and 5,6-diamino-1,3-dimethyluracil explored through the renin-angiotensin system (RAS)-regulating aminopeptidases

A series of Ni(II), Zn(II) and Cd(II) complexes with the Schiff base derived from the condensation 1:1 from pyridine-2-carboxaldehyde and 5,6-diamino-1,3-dimethyluracil (6-amino-1,3-dimethyl-5-[(pyridin-2-ylmethylidene)-amino]pyrimidine-2,4(1H,3H)-dione, DAAUPic) were synthesized and subsequently characterized by means of elemental analysis, FT-IR, NMR and nine of them by X-ray diffraction. Except the [Zn(μ-O,O'-AcO)(N⁵,N⁶,N^1F-DAAUPicH_-1)]₂ and [Cd(O,O'-NO₃)(μ-O⁴,(N⁵,N⁶,N^1F)-DAAUPicH_-1)(H₂O)]₂·2H₂O dimers and the [Cd(μ-S,N-SCN)(N⁵,N⁶,N^1F-DAAUPicH_-1)]_n chain-like polymer, all of them display monomeric molecular structures. The anticancer activity of compounds was also explored studying their effects on renin-angiotensin system (RAS)-regulating aminopeptidases on estrogen-dependent and triple negative breast cancer cell lines. At the concentrations used, some of the complexes showed different effects on (RAS) peptidases, which support the idea that their effects on cell growth/proliferation could be related to autocrine/paracrine regulatory functions of their corresponding peptide substrates.

A PCR-RFLP method for detection of the LNPEP encoding human insulin-regulated aminopeptidase (IRAP) rs4869317 polymorphism

Background & objectives:

Insulin regulated aminopeptidase (IRAP) has been related to certain pathologies such as breast cancer, Alzheimer's disease and septic shock. IRAP is encoded by the leucyl/cystinyl aminopeptidase (LNPEP) gene. The genetic variation in the LNPEP gene has been analyzed in relation with the mortality and vasopressin clearance in septic shock. The LNPEP rs4869317 SNP (single nucleotide polymorphism) was the most significantly associated SNP with vasopressinase activity, being TT genotype associated with increased mortality. The objective of the present study was to develop a simple method to allow a quick and affordable genotyping for the rs4869317 SNP of LNPEP gene.

Methods:

Blood DNA samples were obtained from randomly selected healthy volunteers (n=28). A pair of primers was designed to amplify an 834 bp region of the LNPEP gene containing the rs4869317 SNP. The two alleles (T or A) were detected by digestion of the PCR products with the PacI restriction endonuclease. This enzyme only cuts the PCR products when the adenine is present in the SNP.

Results:

All individuals showed RFPL (restriction fragment length polymorphism) fragments for the expected genotypes (TT, TA or AA). The methodology was validated by sequencing of the amplified DNAs from several ‘T/T’ and ‘A/A’ homozygotes and ‘T/A’ heterozygotes. The results from both methods showed agreement.

Interpretation & conclusions:

The PCR-RFLP is a simple and reliable method that allows a quick genotyping for the rs4869317 SNP of LNPEP gene. The study of this polymorphism could be useful in future investigations to analyze the role of genetic variants of IRAP in several physiological/pathological conditions.

Novel adipocyte aminopeptidases are selectively upregulated by insulin in healthy and obese rats

The lack of a complete assembly of the sensitivity of subcellular aminopeptidase (AP) activities to insulin in different pathophysiological conditions has hampered the complete view of the adipocyte metabolic pathways and its implications in these conditions. Here we investigated the influence of insulin on basic AP (APB), neutral puromycin-sensitive AP (PSA), and neutral puromycin-insensitive AP (APM) in high and low density microsomal and plasma membrane fractions from adipocytes of healthy and obese rats. Catalytic activities of these enzymes were fluorometrically monitoring in these fractions with or without insulin stimulus. Canonical traffic such as insulin-regulated AP was not detected for these novel adipocyte APs in healthy and obese rats. However, insulin increased APM in low density microsomal and plasma membrane fractions from healthy rats, APB in high density microsomal fraction from obese rats and PSA in plasma membrane fraction from healthy rats. A new concept of intracellular compartment-dependent upregulation of AP enzyme activities by insulin emerges from these data. This relatively selective regulation has pathophysiological significance, since these enzymes are well known to act as catalysts and receptor of peptides directly related to energy metabolism. Overall, the regulation of each one of these enzyme activities reflects certain dysfunction in obese individuals.

Adipocyte aminopeptidases in obesity and fasting

This study checked the existence of a diverse array of aminopeptidase (AP) enzymes in high (HDM) and low (LDM) density microsomal and plasma membrane (MF) fractions from adipocytes of control, monosodium glutamate obese and food deprived rats. Gene expression was detected for ArgAP, AspAP, MetAP, and two AlaAP (APM and PSA). APM and PSA had the highest catalytic efficiency, whereas AspAP the highest affinity. Subcellular distribution of AP activities depended on metabolic status. Comparing catalytic levels, AspAP in HDM, LDM and MF was absent in obese and control under food deprivation; PSA in LDM was 3.5-times higher in obese than in normally fed control and control and obese under food deprivation; MetAP in MF was 4.5-times higher in obese than in food deprived obese. Data show new AP enzymes genetically expressed in subcellular compartments of adipocytes, three of them with altered catalytic levels that respond to whole-body energetic demands.

Efficacy of parenteral administration of bee venom in experimental arthritis in the rat: a comparison with methotrexate

The use of bee venom (BV) to treat inflammation and pain in arthritis has become increasingly common. This study aimed to compare the effects of BV and methotrexate (MTX), the most used disease-modifying anti-rheumatic drug, in arthritic rats. Edema, erythema, cyanosis, hyperalgesia, reduction of the body mass gain, high circulating tumor necrosis factor alpha (TNF-α) and anti-type II collagen antibodies (AACII), and altered activity of basic (APB) and neutral (APN) aminopeptidases and dipeptidyl peptidase IV (DPPIV) are present in arthritic rats. MTX and/or BV do not affect AACII in healthy or arthritic individuals, but restores TNF-α to normal levels in arthritic rats. BV restores body mass gain to normal levels and MTX ameliorates body mass gain. BV contains DPPIV. BV restores APN in synovial fluid (SF) and in soluble fraction (S) from synovial tissue (ST), and DPPIV in solubilized membrane-bound fraction (M) from peripheral blood mononuclear cells (PBMCs). MTX restores APN of SF, as well as ameliorates APB of S-PBMCs, APN of S-ST and DPPIV of M-PBMCs. The combination therapy does not overcome the effects of BV or MTX alone on the peptidase activities. Edema is ameliorated by MTX or BV alone. MTX, but not BV, is effective in reducing hyperalgesia. Data show that anti-arthritic effects of BV at non-acupoints are not negligible when compared with MTX.

Altered Activity and Expression of Cytosolic Peptidases in Colorectal Cancer

BACKGROUND AND OBJECTIVE

The role of peptidases in carcinogenic processes and their potential usefulness as tumor markers in colorectal cancer (CRC) have been classically attributed to cell-surface enzymes. The objective of the present study was to analyze the activity and mRNA expression of three cytosolic peptidases in the CRC and to correlate the obtained results with classic histopathological parameters for tumor prognosis and survival.

METHODS

The activity and mRNA levels of puromycin-sensitive aminopeptidase (PSA), aminopeptidase B (APB) and pyroglutamyl-peptidase I (PGI) were measured by fluorimetric and quantitative RT-PCR methods in colorectal mucosa and tumor tissues and plasma samples from CRC patients (n=81).

RESULTS

1) PSA and APB activity was higher in adenomas and carcinomas than in the uninvolved mucosa. 2) mRNA levels of PSA and PGI was lower in tumors. 3) PGI activity in CRC tissue correlated negatively with histological grade, tumor size and 5-year overall survival of CRC patients. 4) Higher plasmatic APB activity was independently associated with better 5-year overall survival.

CONCLUSIONS

Data suggest that cytosolic peptidases may be involved in colorectal carcinogenesis and point to the determination of this enzymes as a valuable method in the determination of CRC prognosis.

Structural and theoretical studies on rhodium and iridium complexes with 5-nitrosopyrimidines. Effects on the proteolytic regulatory enzymes of the renin-angiotensin system in human tumoral brain cells

The reactions of [RhCl(CO)(PPh3)2], [RhCl(CO)2]2 and [IrCl(CO)(PPh3)2] with different 5-nitrosopyrimidines afforded sixteen complexes which have been structurally characterized by elemental analysis, IR and NMR ((1)H and (13)C) spectral methods and luminescence spectroscopy. The crystal and molecular structures of [Rh(III)Cl(VIOH-1)2(PPh3)], [Rh(III)Cl(DVIOH-1)2(PPh3)] and [Rh(II)(DVIOH-1)2(PPh3)2] have been established from single crystal x-ray structure analyses. The three complexes are six-coordinated with both violurato ligands into an equatorial N5,O4-bidentate fashion, but with different mutually arrangements. Theoretical studies were driven on the molecular structure of [Rh(III)Cl(VIOH-1)2(PPh3)] to assess the nature of the metal-ligand interaction as well as the foundations of the cis-trans (3L-2L) isomerism. An assortment of density functional (SOGGA11-X, B1LYP, B3LYP, B3LYP-D3 and wB97XD) has been used, all of them leading to a similar description of the target system. Thus, a topological analysis of the electronic density within AIM scheme and the study of the Mulliken charges yield a metal-ligand link of ionic character. Likewise, it has been proved that the cis-trans isomerism is mainly founded on that metal-ligand interaction with the relativistic effects playing a significant role. Although most of the compounds showed low direct toxicity against the human cell lines NB69 (neuroblastoma) and U373-MG (astroglioma), they differently modify in several ways the renin-angiotensin system (RAS)-regulating proteolytic regulatory enzymes aminopeptidase A (APA), aminopeptidase N (APN) and insulin-regulated aminopeptidase (IRAP). Therefore, these complexes could exert antitumor activity against both brain tumor types, acting through the paracrine regulating system mediated by tissue RAS rather than exerting a direct cytotoxic effect on tumor cells.

Identification and characterization of novel inhibitors of Mammalian aspartyl aminopeptidase

Aspartyl aminopeptidase (DNPEP) has been implicated in the control of angiotensin signaling and endosome trafficking, but its precise biologic roles remain incompletely defined. We performed a high-throughput screen of ∼25,000 small molecules to identify inhibitors of DNPEP for use as tools to study its biologic functions. Twenty-three confirmed hits inhibited DNPEP-catalyzed hydrolysis of angiotensin II with micromolar potency. A counter screen against glutamyl aminopeptidase (ENPEP), an enzyme with substrate specificity similar to that of DNPEP, identified eight DNPEP-selective inhibitors. Structure-activity relationships and modeling studies revealed structural features common to the identified inhibitors, including a metal-chelating group and a charged or polar moiety that could interact with portions of the enzyme active site. The compounds identified in this study should be valuable tools for elucidating DNPEP physiology.

Local thyroid renin-angiotensin system in experimental breast cancer

An association between breast cancer and thyroid dysfunction exists although the underlying mechanisms remain to be elucidated. Numerous studies have characterized the role of thyroid hormones in controlling the synthesis and secretion of renin-angiotensin system (RAS) components, but little information is available on the putative role of the local RAS on thyroid function.

AIMS

Here we analyze several soluble and membrane-bound RAS-regulating aminopeptidase activities in thyroid gland from rats with mammary tumors and the relationship with the circulating levels of thyroid stimulating hormone (TSH) and free thyroxin (fT4).

MAIN METHODS

We analyze soluble and membrane-bound RAS-regulating aminopeptidase activities fluorometrically using their corresponding aminoacyl-β-naphthylamide as the substrate.

KEY FINDINGS

We have found in rats with mammary tumors a concomitant change of thyroid RAS-regulating enzymes and thyroid hormone production.

SIGNIFICANCE

We suggest that existence of alterations in the regulatory mechanisms mediated by the angiotensins of the local tissue RAS as a consequence of the carcinogenic process which could act alone or in combination with alterations at a higher level of regulation such as the hypothalamus-pituitary axis.

Clinical impact of aspartyl aminopeptidase expression and activity in colorectal cancer

Aspartyl aminopeptidase (ASP; EC 3.4.11.21) is a widely distributed and abundant cytosolic enzyme that regulates bioactive peptides such as angiotensin II. It has been demonstrated that the expression and activity of this enzyme is modified in tissue and serum of patients with several types of cancer. However, the involvement of ASP in the neoplastic development and survival of patients with colorectal cancer (CRC) has not been analyzed to date. The activity and messenger RNA expression of ASP in tumor tissue (n = 71) and plasma (n = 40) of patients with CRC was analyzed prospectively using fluorometric and quantitative real-time polymerase chain reaction methods. Data obtained from tumor tissue were compared with those from the surrounding normal mucosa. Classic pathologic parameters (grade, stage, nodal invasion, distant metastases and perineural, lymphatic, and vascular invasion) were stratified following ASP data and analyzed for 5-year survival. ASP was upregulated in CRC tissues, and greater activity correlated significantly with the absence of lymph node metastases and with better overall survival. Inversely, greater plasmatic ASP activity was associated with worse overall and disease-free survival. Data suggest that ASP is involved in colorectal neoplasia and point to this enzyme as a potential useful diagnostic tool in clinical practice.