Clinical significance of the human acid phosphatases: a review

Phosphorescence, fluorescence, and colorimetric triple-mode sensor for the detection of acid phosphatase and corresponding inhibitor

Acid phosphatase (ACP) as a clinical diagnostic biomarker for several pathophysiological diseases has aroused widespread interest. Compared to commonly developed single-mode ACP detection technology, the multi-mode detection method with self-validation can provide more reliable results. Herein, we proposed a triple-mode phosphorescence, fluorescence, and colorimetric method for ACP detection in combination with CDs@SiO₂. HAuCl₄ with oxidase-like activity can catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to the blue oxide TMB (TMBox), offering absorption signals and quenching the phosphorescence and fluorescence of CDs@SiO₂ based on the internal filtration effect (IFE). ACP can hydrolyze ascorbic acid 2-phosphate (AAP) to yield ascorbic acid (AA), thereby reducing TMBox to TMB, triggering solution fading and restoring phosphorescence and fluorescence signals. When the ACP inhibitor malathion is present, the reduction of TMBox is hindered, which successively led to the suppression of CDs@SiO₂ phosphorescence and fluorescence signal recovery. According to these principles, triple-mode ACP (LOD = 0.0026 mU mL^-1) and malathion detections (LOD = 0.039 μg mL^-1) with favorable accuracy and sensitivity are realized. With simplicity, robustness, and versatility, the triple-mode sensor can be extended to the detection of the AAP hydrolase family and the screening of corresponding inhibitors.

Sensitive acid phosphatase assay based on light-activated specific oxidase mimic activity

Acid phosphatase (ACP) is a key marker in the diagnosis of many diseases. However, exploiting a simple and sensitive sensor for the real-time quantitative analysis of ACP is still challenging. Herein, we attempted to develop a sensitive colorimetric sensing strategy for the detection of ACP based on light-activated oxidase mimic property of carbon dots (CDs). The synthesized CDs were proved to be capable of intrinsic light-activated oxidase mimic activity, which could generate reactive oxygen species to oxidize chromogenic substrate under ultraviolet light stimulation. Interestingly, this light-activated oxidase mimic behavior would be effectively suppressed by the antioxidant ascorbic acid (AA), a product from the hydrolysis of 2-phospho-L-ascorbic acid trisodium (AAP) mediated by ACP. Based on the above property, a facile and sensitive colorimetric sensing method for ACP was developed. Under the optimal conditions, the linear range for ACP 0.1-5.5 U/L, and the detection limit was 0.056 U/L. Compared with conventional nanozyme based ACP assay systems, the catalytic activity of light-activated nanozyme could be conveniently regulated by switching the light on and off, which made it easier to precisely control the extent of the reaction and ensured the accuracy of the assay. In addition, the proposed sensing system would be readout directly by the naked eye or smartphone-based RGB analysis system, and have been successfully applied to analyze diluted in diluted fetal bovine serum and urine samples spiked with ACP. All these results indicated that this approach holds good promise for future applications in clinical analysis and point-of-care (POC) biosensor platforms.

Near-infrared (NIR) fluorescence-emitting small organic molecules for cancer imaging and therapy

We discuss recent advances made in the development of NIR fluorescence-emitting small organic molecules for tumor imaging and therapy.

Kinetic Studies of Newly Patented Aminoalkanol Derivatives with Potential Anticancer Activity as Competitive Inhibitors of Prostate Acid Phosphatase

BACKGROUND

Acid phosphatase and its regulation are important objects of biological and clinical research and play an important role in the development and treatment of prostate and bone diseases. The newly patented aminoalkanol (4-[2-hydroxy-3-(propan-2-ylamino)propyl]-1,7-dimethyl-8,9-diphenyl-4-azatricyclo[5.2.1.02,6]dec-8-ene-3,5,10-trione hydrochloride) (I) and (4-[3-(dimethylamino)-2-hydroxypropyl]-1,7-dimethyl-8,9-diphenyl-4-azatricyclo[5.2.1.02,6]dec-8-ene-3,5,10-trione hydrochloride) (II) derivatives have potential anticancer activity, and their influence on enzymatic activity can significantly impact the therapeutic effects of acid phosphatase against many diseases. Therefore, in this study, we investigated the action of compounds (I) and (II) on acid phosphatase.

METHODS

Capillary electrophoresis was used to evaluate the inhibition of acid phosphatase. Lineweaver-Burk plots were constructed to compare the Km of this enzyme in the presence of inhibitors (I) or (II) with the Km in solutions without these inhibitors.

RESULTS

Compound (I) showed a stronger competitive inhibition against acid phosphatase, whereas derivative (II) showed a weaker competitive type of inhibition. The detailed kinetic studies of these compounds showed that their type and strength of inhibition as well as affinity depend on the kind of substituent occurring in the main chemical molecule.

CONCLUSIONS

This study is of great importance because the disclosed inhibition of acid phosphatase by compounds (I) and (II) raises the question of whether these compounds could have any effect on the treatment possibilities of prostate diseases.

Polydopamine coated copper nanoclusters with aggregation-induced emission for fluorometric determination of phosphate ion and acid phosphatase activity

The preparation of aggregation-induced emission-type copper nanoclusters (CuNCs) capped with polydopamine (PDA) is described. PDA was formed via in situ polymerization of dopamine in the presence of alkaline polyethylenimine. The PDA-capped CuNCs (PDA-CuNCs) exhibit orange fluorescence with maximal emission at 580 nm upon excitation at 340 nm, a storage stability of at least 2 weeks, and a quantum yield (QY) of 2.54% in aqueous solution. The QY is 28-fold higher than that of sole CuNCs. The fluorescence of the PDA-CuNCs is quenched by Fe³⁺ ion while it is recovered by PO₄^3- due to its stronger affinity for Fe³⁺. On this basis, a fluorometric phosphate assay was developed that has a 1.5 nM detection limit and a linear range over 0.003-70 μM. The method was satisfactorily applied to the determination of phosphate in local tap water and human sera, and the results agreed well with those obtained by a colorimetric method. In the presence of acid phosphatase (ACP), PO₄^3- is produced by the catalytic hydrolysis of adenosine triphosphate (ACP substrate). Thus, a fluorogenic assay for screening ACP activity was established. Response is linear over the activity range 0.0012-25 U L^-1, with a detection limit of 0.001 U L^-1 (at S/N = 3). Graphic abstract We proposed an effective polydopamine-templating strategy for the in situ synthesis of highly emissive and stable CuNCs and demonstrated its use as an ion-driven fluorescence switch for the determination of phosphate and acid phosphatase activity.

Proteomic Analysis Reveals that Topoisomerase 2A is Associated with Defective Sperm Head Morphology

Male infertility is widespread and estimated to affect 1 in 20 men. Although in some cases the etiology of the condition is well understood, for at least 50% of men, the underlying cause is yet to be classified. Male infertility, or subfertility, is often diagnosed by looking at total sperm produced, motility of the cells and overall morphology. Although counting spermatozoa and their associated motility is routine, morphology assessment is highly subjective, mainly because of the procedure being based on microscopic examination. A failure to diagnose male-infertility or sub-fertility has led to a situation where assisted conception is often used unnecessarily. As such, biomarkers of male infertility are needed to help establish a more consistent diagnosis. In the present study, we compared nuclear extracts from both high- and low-quality spermatozoa by LC-MS/MS based proteomic analysis. Our data shows that nuclear retention of specific proteins is a common facet among low-quality sperm cells. We demonstrate that the presence of Topoisomerase 2A in the sperm head is highly correlated to poor head morphology. Topoisomerase 2A is therefore a potential new biomarker for confirming male infertility in clinical practice.

Prostate-specific markers to identify rare prostate cancer cells in liquid biopsies

Despite improvements in early detection and advances in treatment, patients with prostate cancer continue to die from their disease. Minimal residual disease after primary definitive treatment can lead to relapse and distant metastases, and increasing evidence suggests that circulating tumour cells (CTCs) and bone marrow-derived disseminated tumour cells (BM-DTCs) can offer clinically relevant biological insights into prostate cancer dissemination and metastasis. Using epithelial markers to accurately detect CTCs and BM-DTCs is associated with difficulties, and prostate-specific markers are needed for the detection of these cells using rare cell assays. Putative prostate-specific markers have been identified, and an optimized strategy for staining rare cancer cells from liquid biopsies using these markers is required. The ideal prostate-specific marker will be expressed on every CTC or BM-DTC throughout disease progression (giving high sensitivity) and will not be expressed on non-prostate-cancer cells in the sample (giving high specificity). Some markers might not be specific enough to the prostate to be used as individual markers of prostate cancer cells, whereas others could be truly prostate-specific and would make ideal markers for use in rare cell assays. The goal of future studies is to use sensitive and specific prostate markers to consistently and reliably identify rare cancer cells.

Chronic exposure to microcystin-leucine-arginine promoted proliferation of prostate epithelial cells resulting in benign prostatic hyperplasia

Microcystin-leucine-arginine (MC-LR), as a most common and deleterious variant among all structural analogues of Microcystins (MCs), can cause male reproductive dysfunction. However, its toxic effects on prostate in adult mice have not been invested in detail. In this study, we observed that MC-LR could enter prostate tissues and induce focal hyperplasia and prostate inflammation. Moreover, increased levels of prostate specific antigen (PSA) and prostate acid phosphatase (PAP) in serum of mice following chronic exposure to MC-LR were detected. We also examined increased expression of forkhead box protein M1 (FOXM1) and PSA in human prostate epithelial cells (RWPE-1) treated with MC-LR at low levels, and FOXM1 could regulate PSA expression. Furthermore, MC-LR also induced expression of CyclinD1 via FOXM1/Wnt/β-catenin signaling pathways in RWPE-1 cells, promoting proliferation of prostate epithelial cells, resulting in prostatic hyperplasia in vivo. As a foreign substance, MC-LR also induced immune reaction in RWPE-1 cells mediated by NF-κB pathway, promoting production of pro-inflammatory cytokines and chemokines. Collectively, these findings demonstrated that MC-LR may induce prostatic hyperplasia and prostatitis in mice following chronic low-dose exposure to MC-LR. This work may provide new perspectives in developing new diagnosis and treatment strategies for MC-LR-induced prostatic toxicity.

Methodology and Applications of Disease Biomarker Identification in Human Serum

Biomarkers are biomolecules that serve as indicators of biological and pathological processes, or physiological and pharmacological responses to a drug treatment. Because of the high abundance of albumin and heterogeneity of plasma lipoproteins and glycoproteins, biomarkers are difficult to identify in human serum. Due to the clinical significance the identification of disease biomarkers in serum holds great promise for personalized medicine, especially for disease diagnosis and prognosis. This review summarizes some common and emerging proteomics techniques utilized in the separation of serum samples and identification of disease signatures. The practical application of each protein separation or identification technique is analyzed using specific examples. Biomarkers of cancers of prostate, breast, ovary, and lung in human serum have been reviewed, as well as those of heart disease, arthritis, asthma, and cystic fibrosis. Despite the advancement of technology few biomarkers have been approved by the Food and Drug Administration for disease diagnosis and prognosis due to the complexity of structure and function of protein biomarkers and lack of high sensitivity, specificity, and reproducibility for those putative biomarkers. The combination of different types of technologies and statistical analysis may provide more effective methods to identify and validate new disease biomarkers in blood.

Chitosan-stabilized platinum nanoparticles as effective oxidase mimics for colorimetric detection of acid phosphatase

Capping molecules on the surface of nanomaterials not only enhance the dispersion and stability of nanomaterials but also greatly facilitate their surface modification and biological applications. However, most capping molecules can severely block the active sites of the catalytic core, thereby decreasing the enzymatic activity of nanomaterial-based enzyme mimics. This work demonstrates the superiority of chitosan (Ch) as a capping molecule for synthesizing catalytic platinum nanoparticles (PtNPs). The experimental results show that Ch simultaneously exhibits an excellent stabilizing effect and enhances the oxidase-like activity of PtNPs. Kinetic studies indicate that Ch-PtNPs have a higher affinity for 3,3',5,5'-tetramethylbenzidine (TMB) than other kinds of oxidase mimics. Furthermore, the TMB chromogenic reaction catalyzed by Ch-PtNPs is found to be much faster in an acidic medium, thus adapting well to the optimal pH for acid phosphatase (ACP). Therefore, a novel colorimetric approach for ACP determination is developed for the first time, which is based on the Ch-PtNP-catalyzed oxidation of TMB, the inhibitory effect of ascorbic acid (AA) on the oxidase-like activity of Ch-PtNPs, and the ACP-catalyzed hydrolysis of AA 2-phosphate (AAP) into AA. The linear range for ACP is 0.25-2.5 U L^-1 and the limit of detection is measured to be 0.016 U L^-1. This new colorimetric method is utilized to detect ACP in real biological samples and to screen ACP inhibitors. We believe that these new PtNPs, which exhibit high colloidal stability, excellent catalytic performance, good biocompatibility, simple preparation, and easy modification, can be promising candidates for a broad range of applications in optical sensing, environmental monitoring, clinical diagnosis, and drug discovery.

Turn-On Colorimetric Platform for Dual Activity Detection of Acid and Alkaline Phosphatase in Human Whole Blood

The activity detection of acid phosphatase (ACP) and alkaline phosphatase (ALP) is of great importance to the diagnosis and prognosis of related diseases. In this work, we report for the first time a turn-on colorimetric platform for the activity detection of ACP and ALP, by exploiting Cu(BCDS)₂^2- (BCDS=bathocuproinedisulfonate) as the probe. The presence of ACP or ALP dephosphorylates the substrate ascorbic acid 2-phosphate to produce ascorbic acid, which then reduces Cu(BCDS)₂^2- into Cu(BCDS)₂^3- , leading to a turn-on spectral absorption at 484 nm and a dramatic color change of the solution from colorless to orange-red. The underlying metal-to-ligand charge-transfer mechanism has been demonstrated by quantum mechanical computations. This platform allows a rapid, sensitive readout of ACP and ALP activities within the dynamic range from 0 to 220 mU ml^-1 . In addition, it is highly immune to false-positive results and also highly selective. More importantly, it is applicable in the presence of human serum and even whole blood samples. These results demonstrate that our platform holds great potential in clinical practices and in the point-of-care analysis.

Ages at a Crime Scene: Simultaneous Estimation of the Time since Deposition and Age of Its Originator

Blood is a major contributor of evidence in investigations involving violent crimes because of the unique composition of proteins and low molecular weight compounds present in the circulatory system, which often serve as biomarkers in clinical diagnostics. It was recently shown that biomarkers present in blood can also identify characteristics of the originator, such as ethnicity and biological sex. A biocatalytic assay for on-site forensic investigations was developed to simultaneously identify the age range of the blood sample originator and the time since deposition (TSD) of the blood spot. For these two characteristics to be identified, the levels of alkaline phosphatase (ALP), a marker commonly used in clinical diagnostics corresponding to old and young originators, were monitored after deposition for up to 48 h to mimic a crime scene setting. ALP was chosen as the biomarker due to its age-dependent nature. The biocatalytic assay was used to determine the age range of the originator using human serum samples. By means of statistical tools for evaluation and the physiological levels of ALP in healthy people, the applicability of this assay in forensic science was shown for the simultaneous determination of the age of the originator and the TSD of the blood spot. The stability of ALP in serum allows for the differentiation between old and young originators up to 2 days after the sample was left under mimicked crime scene conditions.

Immunochemical Assays and Nucleic-Acid Detection Techniques for Clinical Diagnosis of Prostate Cancer

Prostate cancer (PCa) is a significant cause of morbidity and mortality and the most common cancer in men in Europe, North America, and some parts of Africa. The established methods for detecting PCa are normally based on tests using Prostate Specific Antigen (PSA) in blood, Prostate cancer antigen 3 (PCA3) in urine and tissue Alpha-methylacyl-CoA racemase (AMACR) as tumour markers in patient samples. Prior to the introduction of PSA in clinics, prostatic acid phosphatase (PAP) was the most widely used biomarker. An early diagnosis of PCa through the detection of these biomarkers requires the availability of simple, reliable, cost-effective and robust techniques. Immunoassays and nucleic acid detection techniques have experienced unprecedented growth in recent years and seem to be the most promising analytical tools. This growth has been driven in part by the surge in demand for near-patient-testing systems in clinical diagnosis. This article reviews immunochemical assays, and nucleic-acid detection techniques that have been used to clinically diagnose PCa.

Cellular prostatic acid phosphatase, a PTEN-functional homologue in prostate epithelia, functions as a prostate-specific tumor suppressor

The inactivation of tumor suppressor genes (TSGs) plays a vital role in the progression of human cancers. Nevertheless, those ubiquitous TSGs have been shown with limited roles in various stages of diverse carcinogenesis. Investigation on identifying unique TSG, especially for early stage of carcinogenesis, is imperative. As such, the search for organ-specific TSGs has emerged as a major strategy in cancer research. Prostate cancer (PCa) has the highest incidence in solid tumors in US males. Cellular prostatic acid phosphatase (cPAcP) is a prostate-specific differentiation antigen. Despite intensive studies over the past several decades on PAcP as a PCa biomarker, the role of cPAcP as a PCa-specific tumor suppressor has only recently been emerged and validated. The mechanism underlying the pivotal role of cPAcP as a prostate-specific TSG is, in part, due to its function as a protein tyrosine phosphatase (PTP) as well as a phosphoinositide phosphatase (PIP), an apparent functional homologue to phosphatase and tensin homolog (PTEN) in PCa cells. This review is focused on discussing the function of this authentic prostate-specific tumor suppressor and the mechanism behind the loss of cPAcP expression leading to prostate carcinogenesis. We review other phosphatases' roles as TSGs which regulate oncogenic PI3K signaling in PCa and discuss the functional similarity between cPAcP and PTEN in prostate carcinogenesis.

Human prostatic acid phosphatase: structure, function and regulation

Human prostatic acid phosphatase (PAcP) is a 100 kDa glycoprotein composed of two subunits. Recent advances demonstrate that cellular PAcP (cPAcP) functions as a protein tyrosine phosphatase by dephosphorylating ErbB-2/Neu/HER-2 at the phosphotyrosine residues in prostate cancer (PCa) cells, which results in reduced tumorigenicity. Further, the interaction of cPAcP and ErbB-2 regulates androgen sensitivity of PCa cells. Knockdown of cPAcP expression allows androgen-sensitive PCa cells to develop the castration-resistant phenotype, where cells proliferate under an androgen-reduced condition. Thus, cPAcP has a significant influence on PCa cell growth. Interestingly, promoter analysis suggests that PAcP expression can be regulated by NF-κB, via a novel binding sequence in an androgen-independent manner. Further understanding of PAcP function and regulation of expression will have a significant impact on understanding PCa progression and therapy.

Serum bone resorption markers after parathyroidectomy for renal hyperparathyroidism: correlation analyses for the cross-linked N-telopeptide of collagen I and tartrate-resistant acid phosphatase

Patients on long-term dialysis may develop secondary hyperparathyroidism (SHPT) with increased serum concentrations of bone resorption markers such as the cross-linked N-telopeptide of type I collagen (NTX) and type-5b tartrate-resistant acid phosphatase (TRAP). When SHPT proves refractory to treatment, parathyroidectomy (PTX) may be needed. Renal patients on maintenance HD who received PTX for refractory SHPT (n = 23) or who did not develop refractory SHPT (control subjects; n = 25) were followed prospectively for 4 weeks. Serum intact parathyroid hormone (iPTH), NTX, TRAP, and bone alkaline phosphatase (BAP) concentrations were measured serially and correlation analyses were performed. iPTH values decreased rapidly and dramatically. BAP values increased progressively with peak increases observed at 2 weeks after surgery. NTX and TRAP values decreased concurrently and progressively through 4 weeks following PTX. A significant correlation between TRAP and NTX values was observed before PTX but not at 4 weeks after PTX. Additionally, the fractional changes in serum TRAP were larger than those in serum NTX at all times examined after PTX. Serum iPTH, TRAP, and NTX values declined rapidly following PTX for SHPT. Serum TRAP values declined to greater degrees than serum NTX values throughout the 4-week period following PTX.

Biology and clinical significance of tartrate-resistant acid phosphatases: new perspectives on an old enzyme

Type 5 tartrate-resistant acid phosphatase (TRAP) has been a clinically relevant biomarker for about 50 years. It has always been a reliable and specific cytochemical marker for hairy cell leukemia and for differentiated cells of monocytic lineage. Only recently has the test for serum TRAP activity been accepted as sensitive and specific enough for clinical use as a marker of osteoclasts and bone resorption. This has come about through steady advances in knowledge about TRAP enzymology, structure, function, and molecular regulation and a consequent appreciation that TRAP isoforms 5a and 5b have very different clinical significance. As a measure of osteoclast number and bone resorption, TRAP 5b has diagnostic and prognostic applications in osteoporosis, cancers with bone metastasis, chronic renal failure, and perhaps other metabolic and pathologic bone diseases. Serum TRAP 5a, on the other hand, has no relationship to bone metabolism but seems instead to be a measure of activated macrophages and chronic inflammation. Exploration of the real clinical usefulness of serum TRAP 5a for diagnosis and disease management in a wide variety of chronic inflammatory diseases is only now beginning. This perspective traces the important basic scientific developments that have led up to the refinement of serum TRAP isoform immunoassays and their validation as biomarkers of disease. Many unanswered questions remain, providing a wealth of opportunity for continued research of this multifaceted enzyme.

Dietetic habits and quality of semen in Indian subjects

Dietetic habits revealed significant effect on seminal plasma vitamin B12 levels. The mean values for seminal plasma vitamin B12 activity in lactovegetarians from normozoospermic, oligozoospermic and azoospermic groups are significantly lower than the corresponding mean values observed in the nonvegetarian subjects. The mean vitamin B12 content of seminal plasma in azoospermic group was distinctly lower than the mean values in normozoospermic and oligozoospermic groups. However, seminal plasma vitamin B12 values showed no correlation with the sperm content of the corresponding semen in both normozoospermic and oligozoospermic subjects. Studies on sperm morphology and on biochemical parameters revealed no significant effect of the type of diet on sperm count, sperm motility, percentage abnormal sperms, seminal plasma total proteins, albumin, fructose, citric acid, acid and alkaline phosphatase activity in normozoospermic group.

Acid phosphatase activity may affect the tuber swelling by partially regulating sucrose-mediated sugar resorption in potato

APase activity is involved in regulating many physiological and developmental events by affecting the resorption process. In this study, we investigate the role of APase activity in tuber development in potato. APase activities were mainly localized in cytoplasm, gaps among cells and stroma of amyloplasts of parenchyma cells at the stage of tuber swelling. AP1, encoding a putative APase, was also highly expressed in swelling tubers and a low level of expression was observed in elongated stolons and matured tubers. Inhibition of APase activity by applying Brefeldin A, an inhibitor of APase production and secretion, significantly suppressed the tuber swelling and moderately affected the stolon elongation and the tuberization frequency. During tuber development, sucrose serves as the main soluble sugar for long-distance transportation and resorption. Moreover, inhibition of APase activity by Brefeldin A markedly reduced the sucrose content in tubers and further decreased the starch accumulation, suggesting that the function of APase in regulating the tuber swelling might be at least partially mediated by the sugar resorption. Exogenous sucrose treatments further indicate the important role of sucrose-mediated sugar resorption in tuber swelling. These results suggest that the APase activity might affect the tuber swelling by partially regulating the sucrose-mediated sugar resorption.

Proteomic approach for purification of seminal plasma proteins involved in tumor proliferation

Human seminal plasma contains a large array of proteins required for the normal physiology and metabolism of spermatozoa. These are mainly secreted from prostate epithelium, testes, and seminal vesicles. Fortunately, many of these are found to be present at elevated concentration in seminal plasma and act as a biomarker of different carcinomas as their levels are also enhanced in serum and are found to be involved in tumor progression and metastasis apart from fertility. The proteins which were overexpressed in the seminal plasma of prostate carcinoma patients were identified by 2-DE and MALDI-TOF/MS. We have designed a strategy to purify these four proteins prostate specific antigen (PSA), prostatic acid phosphatase (PAP), Zinc alpha2-glycoprotein (ZAG), and progastricsin (PG), together in homogeneity by using simple chromatographic techniques. Acidic and basic fractions of human seminal plasma were separated by ion exchange chromatography and further purified by gel permeation chromatography. Our results form a new and valuable resource for those attempting structure-based drug designing for prostate and other cancers where the amount of proteins is required in plenty and in native form.

Clinical Utility of Biochemical Markers of Bone Metabolism for Improving the Management of Patients with Advanced Multiple Myeloma

Osteolytic bone lesions from advanced multiple myeloma (MM) result in significant skeletal morbidity. Therefore, biochemical markers of bone metabolism, such as the N-terminal and C-terminal telopeptides of type I collagen, bone-specific alkaline phosphatase, and osteocalcin, have been investigated as tools for evaluating the extent of bone disease, risk of skeletal morbidity, and response to antiresorptive treatment. Several studies have shown that the majority of biochemical markers of bone metabolism are increased in patients with MM with osteolytic bone lesions, thus reflecting changes in bone metabolism associated with tumor growth. There is also a growing body of evidence that markers of bone metabolism correlate with the risk of skeletal complications, disease progression, and death. In addition, bone markers could potentially be used as a tool for early diagnosis of bone lesions. The aim of this review is to improve our understanding of bone markers as a clinical tool for the management of malignant bone disease in patients with MM.

Effects of Calcitriol on Type 5b Tartrate-Resistant Acid Phosphatase and Interleukin-6 in Secondary Hyperparathyroidism

BACKGROUND/AIMS

Secondary hyperparathyroidism (SHP) is characterized by high bone turnover and elevated serum bone remodeling markers. Elevation of serum interleukin-6 (IL-6) levels is also characteristic of end-stage renal disease. This study investigates the effects of intravenous calcitriol on serum bone resorptive markers, namely, type 5b tartrate-resistant acid phosphatase (TRACP5b) and IL-6 in patients with SHP.

METHODS

Intravenous calcitriol therapy was given for 16 weeks to 24 patients on maintenance hemodialysis with plasma intact parathyroid hormone (iPTH) levels >300 pg/ml. Blood was drawn at baseline and every 4 weeks for 16 weeks for determination of the levels of biochemical parameters, iPTH, IL-6 and bone remodeling markers, including bone-specific alkaline phosphatase (bAP) and TRACP5b.

RESULTS

Only 21 patients responded to the calcitriol therapy, with significant decrements in serum iPTH after 4 weeks of therapy and thereafter. After 16 weeks of calcitriol therapy, 21 patients had significant decrements in serum iPTH (707.9 +/- 317.8 vs. 205.0 +/- 63.1 pg/ml, p < 0.01). Prior to treatment, a significant correlation was found between increased levels of serum iPTH and IL-6 levels (r = 0.45, p < 0.05). After treatment, there was also a significant and parallel lowering of levels of serum iPTH, IL-6 (8.52 +/- 3.59 vs. 7.24 +/- 2.81 pg/ml, p < 0.01), bAP (54.68 +/- 36.17 vs. 24.55 +/- 13.84 U/l, p < 0.01) and TRACP5b (3.41 +/- 1.89 vs. 1.80 +/- 0.55 U/l, p < 0.01). Our results additionally showed significant positive correlationsbetween baseline levels of serum IL-6 and those of iPTH, bAP and TRACP5b. After 16 weeks of calcitriol treatment, the correlation between IL-6 and iPTH levels lost significance but levels of serum IL-6, bAP and TRACP5b remained significantly correlated.

CONCLUSIONS

Elevated levels of serum IL-6 and bone remodeling markers, namely, bAP and TRACP5b which are common features of SHP, are effectively suppressed by calcitriol therapy. This indicates that hyperparathyroidism not only accelerates bone remodeling but may also aggravate inflammation in patients on maintenance hemodialysis.

GAAAATATGATA-like elements in androgen-associated regulation of the prostatic acid phosphatase gene

Purpose of the study was to clarify molecular mechanisms behind tissue-specific and hormone-dependent gene expression using human prostatic acid phosphatase (hPAP) gene as a model. Regulatory region -734/+467 of hPAP gene induces transcription of a reporter gene in the prostate of transgenic mice. It contains five elements, A-E, homologous to GAAAATATGATA sequence, which is connected to prostate-specific and androgen-dependent gene expression. The significance of the C, D and E elements in the transcriptional regulation of hPAP gene was evaluated using reporter gene assays. The deletion of element C from the hPAP promoter constructs mainly decreased their transcriptional activity in the presence of androgen, while increased activity particularly in the absence of androgens was detected after removal of elements D and E. These events took place in transiently transfected prostatic LNCaP cells, but not in non-prostatic COS-1 cells. As a conclusion, the GAAAATATGATA-like elements are involved in the transcriptional regulation of hPAP promoter constructs in prostatic cells. These elements mediate both transcriptional activation and repression depending on the hormonal status of the cells and location of the element in the construct.

Clinical performance of immunoreactive tartrate-resistant acid phosphatase isoform 5b as a marker of bone resorption

Previous immunoassays developed for the measurement of serum tartrate-resistant acid phosphatase (TRACP) have lacked specificity for osteoclastic TRACP, TRACP 5b, or have not shown satisfactory clinical performance. The aim of this study was to evaluate the clinical performance of a novel immunocapture activity assay for TRACP 5b, in comparison to telopeptide fragments of type I collagen. Within-subject variability and the effect of feeding on TRACP 5b and telopeptides of type I collagen were assessed in 20 healthy premenopausal women. Diurnal variation of TRACP 5b and serum beta C-terminal cross-linked telopeptide of type I collagen (sbetaCTX) was assessed in 12 healthy postmenopausal women. Renal clearance was assessed in 19 end stage renal failure patients undergoing routine haemodialysis. Response to antiresorptive treatment and calcium supplementation was assessed in osteoporotic postmenopausal women treated with alendronate and calcium (n = 16) or with calcium alone (n = 7) for 24 weeks.Within-subject variability (CVi) of TRACP 5b was 6.6%, lower than CVi of urinary and serum telopeptides. TRACP 5b decreased by 2.4 +/- 0.8%, in response to feeding (P < 0.05) compared to 7.0 +/- 2.6% to 7.9 +/- 3.7% for urinary telopeptides (P < 0.05 to < 0.01) and 8.5 +/- 1.7% to 17.8 +/- 2.6% for serum telopeptides (P < 0.0001). The amplitude of the diurnal rhythm for TRACP 5b was small compared to that of sbetaCTX, 14 +/- 4% vs. 137 +/- 14%. Haemodialysis did not have a significant effect on TRACP 5b but reduced sbetaCTX by 46 +/- 4% (P < 0.0001). In response to alendronate, TRACP 5b decreased by 39 +/- 4% compared to 49 +/- 4% to 69 +/- 5% for urinary telopeptides and 75 +/- 8% for sbetaCTX. We conclude that TRACP 5b shows an attenuated response to antiresorptive therapy in comparison with other markers of bone resorption, but that this may be offset by lower biological variability. TRACP 5b may provide useful additional information about bone resorption.

Clinical review 165: Markers of bone remodeling in metastatic bone disease

Many cancers have a strong propensity to spread to bone. The processes involved in cancer dissemination to bone are complex and variable, and the changes in bone metabolism, once bony metastases have occurred, are usually profound. This review surveys the usefulness of bone markers in the diagnosis and follow-up of patients with malignant bone disease. In patients with established bone metastases, most markers of bone remodeling are abnormal compared with healthy controls or cancer patients without bone lesions. Although bone markers may have a potential as diagnostic tools in cancer patients, the available data do not allow final conclusions regarding the accuracy and validity of any of the presently used markers in the diagnosis of bone metastases. As regards monitoring of anticancer therapy, most markers of bone remodeling respond to active treatments. These indices therefore may have the potential to be used in the monitoring of antitumor therapies. However, most if not all of the available evidence on the use of bone markers in monitoring anticancer therapy is observational, and it remains unclear whether they have any beneficial effects on overall outcome. The same is true for their prognostic value, although evidence suggests that suppressed levels of bone formation or high rates of bone resorption are independent predictors of poor survival.

Development of immunoassays for type-5 tartrate-resistant acid phosphatase in human serum

BACKGROUND

Tartrate-resistant acid phosphatase (TRAP) is known as a marker of bone resorption. The purpose of this study was the development of a sensitive and specific immunoassay for TRAP.

METHODS

We have developed two types of immunoassays, enzyme-linked immunosorbent assay (ELISA) and immunoselective enzyme immunoassay (ISEA) using monoclonal antibodies to recombinant TRAP, for determination of TRAP in human serum. To evaluate assay performance, recovery and dilution tests were performed. Further, we determined serum TRAP levels of patients with secondary hyperparathyroidism at different pH conditions.

RESULTS

The detected ranges of ELISA and ISEA were between 0.08 and 5 microg/l and between 0.063 and 4 U/l. Different concentrations of TRAP added were recovered on average at 98.0% in ELISA and 102.9% in ISEA. In the serial dilution test, serum TRAP levels were on average at 101.6% and 109.6% of the expected values in ELISA and ISEA, respectively. The serum TRAP levels of patients with secondary hyperparathyroidism were significantly higher than those of normal controls in ELISA and ISEA. Similar TRAP levels were obtained in the conditions at pH 5.5 and 6.1 in ISEA.

CONCLUSION

The present findings suggest that our assay methods are applicable for clinical tests, and strengthen the idea that serum TRAP is useful as a marker for bone resorption.

Characterization and Purification of Acid Phosphatase from Ancient Human Bone

In this research, acid phosphatase was purified and characterized from approximately 3000-year-old human bones from archeological excavations. Using anion exchange chromatography, two isoenzymes, TrACP and TsACP, were isolated from the bone. TrACP and TsACP were eluted separately, with a concentration gradient, from a CM-sepharose column. The resulting TrACP was further purified on a cellulose phosphate column. The activity was determined by using pNPP as substrate. Additionally, protein was determined by the Bradford and Coomassie Brilliant Blue method. The optimum pHs of TsACP and TrACP were 6 and 5, respectively. The optimum temperatures were 0 and 10 degrees C, respectively. Molecular weights were measured by gel filtration chromatography. The isoenzyme purity was checked with SDS-PAGE. Finally, the effects of sodium molybdate and tartrate on isoenzyme activity were determined.

Acid phosphatases

Acid phosphatases (APs) are a family of enzymes that are widespread in nature, and can be found in many animal and plant species. Mystery surrounds the precise functional role of these molecular facilitators, despite much research. Yet, paradoxically, human APs have had considerable impact as tools of clinical investigation and intervention. One particular example is tartrate resistant acid phosphatase, which is detected in the serum in raised amounts accompanying pathological bone resorption. This article seeks to explore the identity and diversity of APs, and to demonstrate the relation between APs, human disease, and clinical diagnosis.

Dephosphorylation of MnDPDP and related compounds by acid and alkaline phosphatase

The enzymatic dephosphorylation of the magnetic resonance imaging contrast agent Teslascan was studied in in vitro experiments with acid phosphatase (prostatic, from human semen) and alkaline phosphatase (from human placenta). The active component, MnDPDP (manganese (II)-N,N'-dipyridoxylethylenediamine-N,N'-diacetate-5,5'-bis(phosphate), was dephosphorylated by both enzymes to the monophosphate MnDPMP and the totally dephosphorylated compound MnPLED. The corresponding zinc compound, ZnDPDP (which is a result of in vivo metabolism), was also dephosphorylated by both enzymes to ZnDPMP and ZnPLED. In separate experiments, both enzymes dephosphorylated MnDPMP and ZnDPMP. With the same amount of enzyme units, alkaline phosphatase was almost four times more active than acid phosphatase in dephosphorylating MnDPDP and ZnDPDP with only minor differences whether the substrate contained Mn or Zn. A similar difference in enzymatic activity was seen with the monophosphates, MnDPMP and ZnDPMP. This, taken together with the approximately 50 times higher activity of alkaline phosphatase than acid phosphatase in serum shows that alkaline phosphatase is responsible for most of the dephosphorylation of MnDPDP and its metabolites in vivo.

Tartrate-resistant Acid Phosphatase Isoform 5b as Serum Marker for Osteoclastic Activity

Background: Tartrate-resistant acid phosphatase (AcP) 5b is a marker of osteoclastic activity and bone resorption. Immunoassays for serum TRAcP may lack sensitivity and specificity because of the presence of non-bone isoform 5a. The purpose of this study was to isolate the serum isoforms, quantify their disease-related expressions, and test an improved immunoassay for TRAcP 5b.

Methods: We separated TRAcP isoforms chromatographically from pooled sera of healthy, rheumatoid arthritis (RA) and endstage renal disease (ESRD) subjects. TRAcP isoforms were identified by electrophoresis and quantified by biochemical and immunochemical assays. Serum TRAcP activity in healthy, RA, and ESRD cohorts was assessed at pH 5.5 and 6.1, and compared with bone alkaline phosphatase (BAP) and N-telopeptides of type I collagen (NTx).

Results: TRAcP isoforms 5a and 5b were present in all sera; 5b was identical to osteoclastic TRAcP. In serum from healthy subjects, 5a accounted for 87% of the enzyme protein but only 55% of the activity. In RA, both isoforms were increased two- to threefold in protein, but their specific activities were subnormal. In ESRD, only 5b was abnormal, being increased fivefold in protein and threefold in activity. In RA sera, TRAcP activity did not correlate with either BAP or NTx. In ESRD sera, TRAcP activity correlated with BAP and NTx only when measured at pH 6.1.

Conclusions: All sera contained both TRAcP isoforms 5a and 5b, but only 5b was present in bone. TRAcP isoform expression was variable in different diseases. Measurement of TRAcP activity at pH 6.1 improves the specificity of immunoassay for isoform 5b.

Interaction between protein tyrosine phosphatase and protein tyrosine kinase is involved in androgen-promoted growth of human prostate cancer cells

Steroid hormones play key roles in regulating cell proliferation and differentiation in targeting tissues. However, in advanced cancers, the steroid hormone regulation is frequently attenuated through a yet unknown mechanism even in the presence of functional steroid hormone receptors. We investigate the functional role of tyrosine phosphorylation signaling in the hormone-refractory growth of human prostate tumors. Initial studies demonstrate that the androgen-responsive phenotype of human prostate cancer cells associates with a low phosphotyrosine (p-Tyr) level of ErbB-2, which is regulated by cellular prostatic acid phosphatase (PAcP), a protein tyrosine phosphatase. In prostate cancer cells, the p-Tyr level, but not the protein level, of ErbB-2 inversely correlates with the androgen-responsiveness of cell proliferation. Androgen-stimulated cell growth concurs with a down-regulation of cellular PAcP, an elevated p-Tyr level of ErbB-2, and the activation of mitogen-activated protein kinases. Furthermore, only the ErbB-2 inhibitor AG 879, but not the EGFR inhibitor AG 1478, abolishes androgen-induced cell proliferation. Forced expression of ErbB-2 can also attenuate androgen promotion of cell growth. Data taken collectively conclude that in human prostate cancer cells, the tyrosine phosphorylation of ErbB-2 regulated by cellular PAcP plays a key role in regulating androgen-mediated proliferation signaling. Oncogene (2000).

Clinical Significance of Immunoassays for Type-5 Tartrate-resistant Acid Phosphatase

Background: Tartrate-resistant acid phosphatase (TRAP; EC 3.1.3.2) is a product of osteoclasts and a biochemical marker of bone resorption rate. However, erythrocytes and platelets contribute to total TRAP activity in serum, reducing the specificity of direct biochemical assays in serum. Osteoclast TRAP is also known as type-5 TRAP and is antigenically unique. Immunoassays are sought to improve the specificity and sensitivity of TRAP as a bone marker.

Methods: We developed two colorimetric microplate assays for type-5 TRAP: an enzyme capture immunoassay to measure antibody-bound enzymatic activity, and a two-site immunoassay to measure bound enzyme protein. Both use the same monoclonal antibody (14G6) to capture type-5 TRAP, which permits determination of specific activity of serum TRAP in health and disease.

Results: Both TRAP assays were linear from one-tenth to fivefold the mean value in 18 healthy subjects. In these subjects, the mean (SD) TRAP activity was 3.2 (0.54) U/L for the enzyme capture assay and 37 (13) μg/L for the two-site assay. Mean TRAP activity was not significantly increased in 64 patients with endstage renal disease requiring hemodialysis (HD) or 99 unselected patients with rheumatic diseases. By contrast, TRAP protein was increased in both the HD and rheumatic disease groups. The specific activity of TRAP in the 17 of 64 HD sera that had increased TRAP activity (0.088 U/μg) was similar to that in healthy subjects (0.091 U/μg). By contrast, the specific activity of TRAP in the 31 of 99 rheumatic sera with increased TRAP protein (0.035 U/μg) was significantly decreased.

Conclusions: Wide sample distributions for TRAP activity in HD patients and TRAP protein in rheumatic disease patients suggest the presence of subpopulations of HD patients with increased TRAP activity and of rheumatic patients with increased TRAP protein. Each assay for TRAP activity and protein may have its own biological significance and clinical applications in specific groups of patients.

Early metabolic changes in peripheral blood cells of renal transplant recipients treated with cyclosporine A

We histochemically examined (phosphatase acid-AcP, phosphatase alkaline-ALP, succinate dehydrogenase-SDH, lactate dehydrogenase-LDH) the peripheral blood of renal transplant recipients and controls before (day 0) and after Cyclosporine A (CsA) treatment (days 1, 2, 7 and 30). We wanted to detect the metabolic changes induced in the CsA resistant cells (leucocytes) by CsA and to evaluate the early effects determined by the drug. There was no difference in enzyme activities between the control group and renal patients before CsA treatment (day 0). AcP and ALP activity increased 1 day after CsA administration and became similar to the control by the day 30. LDH activity increased one day after CsA treatment and remained high during the treatment period (30 days), while SDH activity did not change. These enzymatic variations may suggest that the LDH enzyme is involved in the drug degradation as are other phosphatase and oxidoreductase enzymes (i.e. cytochrome P450). Moreover, the high activity of LDH, the enzyme responsible for interconversion of pyruvate in lactic acid, would indicate that anaerobic glycolysis is preferentially used in the pyruvate pathway. However, SDH did not seem to be directly involved in CsA metabolism. Our findings showed that the CsA treatment induced clear variations of the activity of the cellular phosphatase and oxidoreductase enzymes from the first days of drug administration. The variation of the enzymes studied and the appearance time and duration of the metabolic changes, may be markers of the cellular stress due to CsA internalization.

Characterization of monoclonal antibodies specific to human tartrate-resistant acid phosphatase

A major product of osteoclasts, tartrate-resistant acid phosphatase (TRAP) is an essential but insufficient enzyme for bone resorption. TRAP is an excellent cell marker for osteoclasts and macrophages and is being investigated as a serum marker for osteoclast activity in diseases of bone destruction. For decades, TRAP has also been used as a marker for hairy cell leukemia. Immunoassays for TRAP are sought to increase the sensitivity and specificity of the TRAP test for bone and hairy cells. Our laboratory recently developed a monoclonal antibody to TRAP (9C5) useful for immunohistochemical identification of TRAP-positive cells in paraffin sections. Herein, we characterize 9C5 in greater detail and report production of another anti-TRAP monoclonal antibody antibody (14G6) reactive with native, active enzyme antigen. Enzyme immunoassay, immunoprecipitation, western blot, and immunohistochemical analyses revealed the contrasting properties of 9C5 and 14G6. Antibody 9C5 reacts with a heat-denatured epitope and is suitable for denaturing western blot analysis and for immunohistochemistry. Antibody 14G6 reacts with a conformational determinant destroyed by heat and is suitable for immunoprecipitation of active TRAP, although 20% to 30% of activity is inhibited in the immune complexes. Having characterized several properties of these anti-TRAP antibodies, 9C5 and 14G6 may be useful for development of TRAP-specific immunoassays in bone pathology and hematology. They will certainly be of use for the study of biosynthesis, regulation, expression, and function of TRAP.

Abnormal acid phosphatases in neuronal ceroid-lipofuscinoses

Acid phosphatases in brain and cultured lymphoblasts from patients affected with neuronal ceroid-lipofuscinoses (NCL) were studied by starch gel electrophoresis. After electrophoresis the gel was incubated with 4-methyl umbelliferyl phosphate at pH 4.5 and the fluorescent reaction product was visualized under ultraviolet light. Control brain showed a single band with mobility of about 1 cm while NCL patients showed two additional fast moving bands. In the late-infantile, and in the adult form (Kufs disease), the middle band was prominent while the fast moving band was predominant in juvenile NCL. In long-term lymphoblasts, controls showed a single band of acid phosphatase activity while both juvenile and late-infantile NCL showed two additional fast moving bands. Obligate heterozygotes showed reduced levels of the fast moving bands. Fluorometric assay of acid phosphatase using 4-methylumbelliferyl phosphate as substrate showed a 2-fold increase in activity in the patients. The increased acid phosphatase activity is completely inhibited by tartrate. Lymphocyte hexosamnidase activities were unchanged in NCL patients lymphoblasts. Studies on brains of NCL patients and on cultured lymphoblasts from families with late-infantile and juvenile form of NCL showed that abnormal acid phosphatase is characteristic of NCL.