Blood Prostate-specific Antigen by Volume of Benign, Gleason Pattern 3 and 4 Prostate Tissue

OBJECTIVE

To evaluate how blood levels of prostate-specific antigen (PSA) relate to prostate volume of benign tissue, Gleason pattern 3 (GP3) and Gleason pattern 4 (GP4) cancer.

METHODS

The cohort included 2209 consecutive men undergoing radical prostatectomy at 2 academic institutions with pT2N0, Grade Group 1-4 prostate cancer and an undetectable postoperative PSA. Volume of benign, GP3, and GP4 were estimated. The primary analysis evaluated the association between PSA and volume of each type of tissue using multivariable linear regression. R2, a measure of explained variation, was calculated using a multivariable model.

RESULTS

Estimated contribution to PSA was 0.04/0.06 ng/mL/cc for benign, 0.08/0.14 ng/mL/cc for GP3, and 0.62/0.80 ng/ml/cc for GP4 for the 2 independent cohorts, respectively. GP4 was associated with 6 to 8-fold more PSA per cc compared to GP3 and 15-fold higher compared to benign tissue. We did not observe a difference between PSA per cc for GP3 vs. benign tissue (P = 0.2). R2 decreased only slightly when removing age (0.006/0.018), volume of benign tissue (0.051/0.054) or GP3 (0.014/0.023) from the model. When GP4 was removed, R2 decreased 0.051/0.310. PSA density (PSA divided by prostate volume) was associated with volume of GP4 but not GP3, after adjustment for benign volume.

CONCLUSION

Gleason pattern 4 cancer contributes considerably more to PSA and PSA density per unit volume compared to GP3 and benign tissue. Contributions from GP3 and benign are similar. Further research should examine the utility of determining clinical management recommendations by absolute volume of GP4 rather than the ratio of GP3 to GP4.

Technical Note: Newly Reformulated Total and Free PSA Immunoassay on Cobas e411 Analyzer Is Virtually Free from Biotin Interference

OBJECTIVE

Total and free prostate specific antigens (PSA) have been used as diagnostic markers for monitoring progress of therapy in patients with prostate cancer as well as for screening purpose. Roche total and free PSA immunoassay utilizes biotinylated antibody in assay design. As a result, both assays are affected by elevated serum biotin levels. Recently, Roche reformulated these assays to reduce biotin interference. We evaluated biotin interference in these products.

MATERIALS AND METHODS

We prepared three serum pools with one pool containing high amount of total PSA. Then aliquots of each serum pool were further supplemented with various concentrations of biotin (100-1500 ng/mL) followed by measuring both total and free PSA using Roche total and free PSA immunoassay and Cobas e411 analyzer.

RESULTS

We observed no significant interference of biotin in both total and free PSA assays up to biotin concentration of 1200 ng/mL.

CONCLUSION

We concluded that newly reformulated total and free PSA immunoassays are virtually free from biotin interference.

The electrochemical detection of prostate specific antigen on glassy carbon electrode modified with combinations of graphene quantum dots, cobalt phthalocyanine and an aptamer

Herein, a novel aptasensor is developed for the electrochemical detection of prostate specific antigen (PSA) on electrode surfaces modified using various combinations of a Cobalt phthalocyanine (CoPc), an aptamer and graphene quantum dots (GQDs). Electrochemical impedance spectroscopy (EIS) as well as differential pulse voltammetry (DPV) are employed for the detection of PSA. In both analytical techniques, linear calibration curves were observed at a concentration range of 1.2-2.0 pM. The glassy carbon electrode where CoPc and GQDs are placed on the electrode when non-covalently linked followed by addition of the aptamer (GQDs-CoPc(ππ)-aptamer (sequential)) showed the best performance with a limit of detection (LoD) as low as 0.66 pM when using DPV. The detection limits were much lower than the dangerous levels reported for PSA in males tested for prostate cancer. This electrode showed selectivity for PSA in the presence of bovine serum albumin, glucose and L-cysteine. The aptasensor showed good stability, reproducibility and repeatability, deeming it a promising early detection device for prostate cancer.

PSMA-D4 Radioligand for Targeted Therapy of Prostate Cancer: Synthesis, Characteristics and Preliminary Assessment of Biological Properties

A new PSMA ligand (PSMA-D4) containing the Glu-CO-Lys pharmacophore connected with a new linker system (L-Trp-4-Amc) and chelator DOTA was developed for radiolabeling with therapeutic radionuclides. Herein we describe the synthesis, radiolabeling, and preliminary biological evaluation of the novel PSMA-D4 ligand. Synthesized PSMA-D4 was characterized using TOF-ESI-MS, NMR, and HPLC methods. The novel compound was subject to molecular modeling with GCP-II to compare its binding mode to analogous reference compounds. The radiolabeling efficiency of PSMA-D4 with 177Lu, 90Y, 47Sc, and 225Ac was chromatographically tested. In vitro studies were carried out in PSMA-positive LNCaP tumor cells membranes. The ex vivo tissue distribution profile of the radioligands and Cerenkov luminescence imaging (CLI) was studied in LNCaP tumor-bearing mice. PSMA-D4 was synthesized in 24% yield and purity >97%. The radio complexes were obtained with high yields (>97%) and molar activity ranging from 0.11 to 17.2 GBq mcmol-1, depending on the radionuclide. In vitro assays confirmed high specific binding and affinity for all radiocomplexes. Biodistribution and imaging studies revealed high accumulation in LNCaP tumor xenografts and rapid clearance of radiocomplexes from blood and non-target tissues. These render PSMA-D4 a promising ligand for targeted therapy of prostate cancer (PCa) metastases.

Design, Synthesis, Computational, and Preclinical Evaluation of natTi/45Ti-Labeled Urea-Based Glutamate PSMA Ligand

Despite promising anti-cancer properties in vitro, all titanium-based pharmaceuticals have failed in vivo. Likewise, no target-specific positron emission tomography (PET) tracer based on the radionuclide ⁴⁵Ti has been developed, notwithstanding its excellent PET imaging properties. In this contribution, we present liquid–liquid extraction (LLE) in flow-based recovery and the purification of ⁴⁵Ti, computer-aided design, and the synthesis of a salan-^natTi/⁴⁵Ti-chelidamic acid (CA)-prostate-specific membrane antigen (PSMA) ligand containing the Glu-urea-Lys pharmacophore. The compound showed compromised serum stability, however, no visible PET signal from the PC3+ tumor was seen, while the ex vivo biodistribution measured the tumor accumulation at 1.1% ID/g. The in vivo instability was rationalized in terms of competitive citrate binding followed by Fe(III) transchelation. The strategy to improve the in vivo stability by implementing a unimolecular ligand design is presented.

Modular Synthesis of DOTA-Metal-Based PSMA-Targeted Imaging Agents for MRI and PET of Prostate Cancer

A practical, convergent synthesis of prostate-specific membrane antigen (PSMA) targeted imaging agents for MRI, PET, and SPECT of prostate cancer has been developed. In this approach, metals chelated to 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) were placed on the side chains of lysine early in the synthesis to form imaging modules. These are coupled to targeting modules, in this case consisting of the PSMA-binding urea DCL, bonded to an activated linker. The modular approach to targeted molecular imaging agents (TMIAs) offers distinct advantages. By chelating the MRI contrast metal Gd early, it doubles as a protecting group for DOTA. Standard coupling and deprotection steps may be utilized to assemble the modules into peptides, and the need for tri-tert-butyl protection of DOTA requiring removal by strong acid is averted. This enables mild conjugation of the imaging module to a wide variety of targeting agents in the final step. It was further discovered that two labile metals, La3+ or Ce3+ , can be used as placeholders in DOTA during the synthesis, then transmetalated in mild acid by Cu2+ , Ga3+ , In3+ , and Y3+ , metals used in PET/SPECT. This enables the efficient synthesis of nonradioactive analogues of targeted molecular imaging agents that may be transported or stored until needed. A simple and mild two-step transmetalation, involving de-metalation in dilute acid, followed by rapid chelation of the radioactive metal, may be conveniently performed later at the clinic to provide the TMIAs for PET or SPECT.

Colorimetric and Fluorescent Dual-Mode Immunoassay Based on Plasmon-Enhanced Fluorescence of Polymer Dots for Detection of PSA in Whole Blood

Although enormous efforts have been devoted to the development of new types of fluorometric immunochromatographic test strip (ICTS) with improved sensitivity over the past years, it still remains a big challenge to design ICTS with colorimetric and fluorescent bimodal signal readout for rapid yet accurate detection of cancer markers in a clinic. Scientists have tried to prepare bimodal reporters by combining fluorescent dyes with metal nanomaterials, but their fluorescence was easily quenched by metal nanomaterials through surface energy transfer, making dual colorimetric and fluorometric ICTS very difficult to be achieved. As compared to conventional fluorescent probes, semiconducting polymer dots (Pdots) exhibit extraordinary fluorescence brightness and facile surface functionalization, which are very suitable to be engineered as bimodal signal reporting reagents. Here, we integrated highly fluorescent Pdots with strongly plasmonic Au nanorods to form Pdot-Au hybrid nanocomposites with dual colorimetric and fluorescent readout abilities. We further utilized these nanohybrids in ICTS for qualitatively fast screening (colorimetry) as well as quantitatively accurate determination (fluorometry) of prostate-specific antigen (PSA) within 10 min. By taking advantage of the plasmon-enhanced fluorescence of Pdots on Au nanorods, this immunoassay possesses much better detection sensitivity of 1.07 pg/mL for PSA, which is at least 2 orders of magnitude lower than that of conventional fluorometric ICTS. Moreover, the direct detection of PSA from human whole blood collected without sample pretreatment makes this Pdot-based ICTS platform promising for on-site point-of-care diagnostics.

Ag/CdO NP-Engineered Magnetic Electrochemical Aptasensor for Prostatic Specific Antigen Detection

A simple magnetic electrochemical aptasensor was established for the detection of prostatic specific antigen (PSA). Ag/CdO nanoparticles (NPs) were fabricated and exhibited strong electroreduction peaks at -1.07 V, attributing to the electron transfer from Cd²⁺ to Cd⁰ and the superior electron transportation of Ag. Aptamer-modified Ag/CdO NPs were assembled on the surface of superparamagnetic Fe₃O₄/graphene oxide nanosheets (GO/Fe₃O₄ NSs) through the hydrophobic and π-π stacking interaction of aptamers and GO NSs. These assemblies possessed superior electroactive properties, efficient electron transfer, and superparamagnetic response and could serve as sensing units for PSA detection with the aid of a magnetic electrode. With increasing concentrations of PSA, the high affinity of aptamers to PSA enabled the dissociation of Ag/CdO NPs from GO/Fe₃O₄ NSs, decreasing the intensity of electroreduction peaks. The Ag/CdO NP-engineered magnetic electrochemical aptasensor achieved sensitive and accurate detection of PSA in the range of 50 pg/mL to 50 ng/mL. The limit of detection (LOD) was as low as 28 pg/mL. This developed protocol can be extended to a large set of strong electroactive labels for reliable tumor biomarker detection with high sensitivity and specificity.

Prostate-Specific Membrane Antigen PET Imaging in Prostate Cancer: Opportunities and Challenges

The aim of this systematic review was to describe the characteristics of prostate-specific membrane antigen (PSMA)-targeting PET and their clinical applications in prostate cancer patients. There have been major strides in the design, synthesis of PSMA-targeting PET tracers over the past several years. PSMA-targeting PET tracers can be categorized, according to positron emitters and targeting strategies for the PSMA. The majority of PSMA PET studies has been focused on patients with biochemical recurrence, but additional values of PSMA PET have also been investigated for use in primary staging, treatment planning, response evaluation, and PSMA radioligand therapy. PSMA PET is expected to bring improvements in the management of patients, but the impact of improved diagnosis by PSMA on overall survival remains unanswered. Many challenges still await PSMA PET to expedite the use in the clinical practice. At this early stage, prospective multicenter trials are needed to validate the effectiveness and usefulness of PSMA PET.

Biochemical Characteristics and Recent Biological Knowledge on Prostate-Specific Antigen

Since its identification in seminal fluid in 1971, much new information has been obtained about the biology and expression of prostate-specific antigen (PSA). PSA is a glycoprotein composed of 93% amino acids and 7% carbohydrates, with a molecular weight of about 30,000 Da. Functionally and structurally PSA is a kallikrein-like serine protease, and its physiologic role is degradation of the major proteins of seminal coagulum (semenogelin I and II, fibronectin), which leads to semen liquefaction. The PSA gene is located on the 13q region of chromosome 19, and it has a high degree of homology (more than 80%) with genes of the human glandular kallikrein (hKGK1). PSA production and expression are preferentially but not exclusively associated to the normal, benign hyperplastic and cancerous tissues of the prostate. In fact, it has been demonstrated that PSA is also present in accessory male sex glands and breast cancer. It was recently reported that PSA was also present in milk of lactating women. Many factors may influence PSA synthesis and production, and among them the most important are androgen, retinoic acid and growth factor stimulation. Significant advances have been recently made as regards the molecular isoforms of PSA. In the seminal fluid PSA seems partially bound to a serpine (protein C inhibitor), whereas in serum it is predominantly associated to α-1-antichymotrypsin and in a small quantity to α-2-macroglobulin. These new findings will have implications for the clinical application of PSA as a tumor marker for prostate cancer.

Development of molecules stimulating the activity of KLK3 - an update

Kallikrein-related peptidase-3 (KLK3, known also as prostate-specific antigen, PSA) is highly expressed in the prostate. KLK3 possess antiangiogenic activity, which we have found to be related to its proteolytic activity. Thus, it may be possible to slow down the growth of prostatic tumors by enhancing this activity. We have developed peptides that enhance the proteolytic activity of KLK3. As these peptides are degraded in circulation and rapidly excreted, we have started to modify them and have succeeded in creating bioactive and more stable pseudopeptides. We have also identified small molecules stimulating the activity of KLK3, especially in synergy with peptides.

Ultrasensitive Detection of Prostate-Specific Antigen and Thrombin Based on Gold-Upconversion Nanoparticle Assembled Pyramids

Self-assembled nanostructures have been used for the detection of numerous cancer biomarkers. In this study, a gold-upconversion-nanoparticle (Au-UCNP) pyramid based on aptamers is fabricated to simultaneously detect thrombin and prostate-specific antigen (PSA) using surface-enhanced Raman scattering (SERS) and fluorescence, respectively. The higher the concentration of thrombin, the lower the intensity of SERS. PSA connected with the PSA aptamer leads to an increase in fluorescence intensity. The limit of detection of thrombin and PSA reaches 57 × 10^-18 and 0.032 × 10^-18 m, respectively. In addition, the pyramid also exhibits great target specificity. The results of human serum target detection demonstrate that the Au-UCNP pyramid is an excellent choice for the quantitative determination of cancer biomarkers, and is feasible for the early diagnosis of cancer.

An Automated Micro-Total Immunoassay System for Measuring Cancer-Associated α2,3-linked Sialyl N-Glycan-Carrying Prostate-Specific Antigen May Improve the Accuracy of Prostate Cancer Diagnosis

The low specificity of the prostate-specific antigen (PSA) for early detection of prostate cancer (PCa) is a major issue worldwide. The aim of this study to examine whether the serum PCa-associated α2,3-linked sialyl N-glycan-carrying PSA (S2,3PSA) ratio measured by automated micro-total immunoassay systems (μTAS system) can be applied as a diagnostic marker of PCa. The μTAS system can utilize affinity-based separation involving noncovalent interaction between the immunocomplex of S2,3PSA and Maackia amurensis lectin to simultaneously determine concentrations of free PSA and S2,3PSA. To validate quantitative performance, both recombinant S2,3PSA and benign-associated α2,6-linked sialyl N-glycan-carrying PSA (S2,6PSA) purified from culture supernatant of PSA cDNA transiently-transfected Chinese hamster ovary (CHO)-K1 cells were used as standard protein. Between 2007 and 2016, fifty patients with biopsy-proven PCa were pair-matched for age and PSA levels, with the same number of benign prostatic hyperplasia (BPH) patients used to validate the diagnostic performance of serum S2,3PSA ratio. A recombinant S2,3PSA- and S2,6PSA-spiked sample was clearly discriminated by μTAS system. Limit of detection of S2,3PSA was 0.05 ng/mL and coefficient variation was less than 3.1%. The area under the curve (AUC) for detection of PCa for the S2,3PSA ratio (%S2,3PSA) with cutoff value 43.85% (AUC; 0.8340) was much superior to total PSA (AUC; 0.5062) using validation sample set. Although the present results are preliminary, the newly developed μTAS platform for measuring %S2,3PSA can achieve the required assay performance specifications for use in the practical and clinical setting and may improve the accuracy of PCa diagnosis. Additional validation studies are warranted.

Separation and dual detection of prostate cancer cells and protein biomarkers using a microchip device

Current efforts for the detection of prostate cancer using only prostate specific antigen are not ideal and indicate a need to develop new assays - using multiple targets - that can more accurately stratify disease states. We previously introduced a device capable of the concurrent detection of cellular and molecular markers from a single sample fluid. Here, an improved design, which achieves affinity as well as size-based separation of captured targets using antibody-conjugated magnetic beads and a silicon chip containing micro-apertures, is presented. Upon injection of the sample, the integration of magnetic attraction with the micro-aperture chip permits larger cell-bead complexes to be isolated in an upper chamber with the smaller protein-bead complexes and remaining beads passing through the micro-apertures into the lower chamber. This enhances captured cell purity for on chip quantification, allows the separate retrieval of captured cells and proteins for downstream analysis, and enables higher bead concentrations for improved multiplexed ligand targeting. Using LNCaP cells and prostate specific membrane antigen (PSMA) to model prostate cancer, the device was able to detect 34 pM of spiked PSMA and achieve a cell capture efficiency of 93% from culture media. LNCaP cells and PSMA were then spiked into diluted healthy human blood to mimic a cancer patient. The device enabled the detection of spiked PSMA (relative to endogenous PSMA) while recovering 85-90% of LNCaP cells which illustrated the potential of new assays for the diagnosis of prostate cancer.

The role of CD147 expression in prostate cancer: a systematic review and meta-analysis

BACKGROUND

There are a number of studies which show that expression of CD147 is increased significantly in prostate cancer (PCa). However, conflicting conclusions have also been reported by other researchers lately. In order to arrive at a clear conclusion, a meta-analysis of eligible studies was conducted.

MATERIALS AND METHODS

We searched PubMed, MEDLINE, Cochrane Library, and the China National Knowledge Infrastructure databases to identify all the published case-control studies on the relationship between the expression of CD147 and PCa until February 2016. In the end, a total of 930 patients in eight studies were included in the meta-analysis.

RESULTS

CD147 expression in the PCa patients increased significantly (odds ratio [OR], 4.65; 95% confidence interval [CI], 3.52-6.14; Z=10.79; P<0.05), but there was obvious heterogeneity between studies (I (2)=92.9%, P<0.05). Subgroup analysis showed that positive expression of CD147 was associated with PCa among the Asian population (OR, 21.01; 95% CI, 12.88-34.28; Z=12.19; P<0.05). Furthermore, it was significantly related to TNM stage (OR, 0.24; 95% CI, 0.17-0.35; Z=7.74; P<0.05), Gleason score (OR, 0.41; 95% CI, 0.31-0.56; Z=5.62; P<0.05), differentiation grade (OR, 0.27; 95% CI, 0.13-0.56; Z=3.47; P<0.05), and pretreatment serum prostate-specific antigen level (OR, 0.07; 95% CI, 0.03-0.16; Z=6.47; P<0.05).

CONCLUSION

Positive expression of CD147 was related to PCa, significant heterogeneity was not found between Asian studies, and the result became more significant. The positive expression of CD147 was significantly related to the clinicopathological characteristics of PCa. This suggests that CD147 plays an essential role in poor prognosis and recurrence prediction.

Photoacoustic imaging with an acoustic lens detects prostate cancer cells labeled with PSMA-targeting near-infrared dye-conjugates

There is an urgent need for sensitive and specific tools to accurately image early stage, organ-confined human prostate cancers to facilitate active surveillance and reduce unnecessary treatment. Recently, we developed an acoustic lens that enhances the sensitivity of photoacoustic imaging. Here, we report the use of this device in conjunction with two molecular imaging agents that specifically target the prostate-specific membrane antigen (PSMA) expressed on the tumor cell surface of most prostate cancers. We demonstrate successful imaging of phantoms containing cancer cells labeled with either of two different PSMA-targeting agents, the ribonucleic acid aptamer A10-3.2 and a urea-based peptidomimetic inhibitor, each linked to the near-infrared dye IRDye800CW. By specifically targeting cells with these agents linked to a dye chosen for optimal signal, we are able to discriminate prostate cancer cells that express PSMA.

Nanoparticle-mediated photothermal effect enables a new method for quantitative biochemical analysis using a thermometer

A new biomolecular quantitation method, nanoparticle-mediated photothermal bioassay, using a common thermometer as the signal reader was developed. Using an immunoassay as a proof of concept, iron oxide nanoparticles (NPs) captured in the sandwich-type assay system were transformed into a near-infrared (NIR) laser-driven photothermal agent, Prussian blue (PB) NPs, which acted as a photothermal probe to convert the assay signal into heat through the photothermal effect, thus allowing sensitive biomolecular quantitation using a thermometer. This is the first report of biomolecular quantitation using a thermometer and also serves as the first attempt to introduce the nanoparticle-mediated photothermal effect for bioassays.

Anti-angiogenic activity of PSA-derived peptides

BACKGROUND

PSA is a biomarker for diagnosis and management of prostate cancer. PSA is known to have anti-tumorigenic activities, however, the physiological role of PSA in prostate tumor progression is not well understood.

METHODS

Five candidate peptides identified based upon computer modeling of the PSA crystal structure and hydrophobicity were synthesized at >95% purity. The peptides in a linear form, and a constrained form forced by a di-sulfide bond joining the two ends of the peptide, were investigated for anti-angiogenic activity in HUVEC.

RESULTS

None of the five PSA-mimetic peptides exhibited PSA-like serine protease activity. Two of the peptides demonstrated significant anti-angiogenic activity in HUVEC based on (i) inhibition of cell migration and invasion; (ii) inhibition of tube formation in Matrigel; (iii) anti-angiogenic activity in a sprouting assay; and (iv) altered expression of pro- and anti-angiogenic growth factors. Constrained PSA-mimetic peptides had greater anti-angiogenic activity than the corresponding linearized form. Complexing of PSA with ACT eliminated PSA enzymatic activity and reduced anti-angiogenic activity. In contrast, ACT had no effect on the anti-angiogenic effects of the linear or constrained PSA-mimetic peptides. Modeling of the ACT-PSA complex demonstrated ACT sterically blocks the anti-angiogenic activity of the two bioactive peptides.

CONCLUSIONS

The interaction of a hydrophilic domain on the surface of the PSA molecule with a target on the cell membrane of prostate endothelial and epithelial cells was responsible for the anti-angiogenic or anti-tumorigenic activity of PSA: enzymatic activity was not associated with anti-angiogenic effects. Furthermore, since PSA and ACT are both expressed within the human prostate tissue microenvironment, the balance of their expression may represent a mechanism for endogenous regulation of tissue angiogenesis.

Total, free, and complexed prostate-specific antigen levels among US men, 2007-2010

BACKGROUND

Screening for prostate cancer using prostate-specific antigen (PSA) is common. Prostate cancer has been associated with higher total PSA (tPSA), lower free PSA (fPSA), lower percent free PSA (%fPSA), and higher complexed PSA (cPSA).

METHODS

Total, free and complexed PSAs were performed on 3251 men ≥40years in the 2007-2010 National Health and Nutrition Examination Survey. Distributions of the PSA tests were examined by age, race and ethnicity, and body mass index (BMI) groups. Percentages of men at PSA thresholds were examined.

RESULTS

Total PSA geometric mean was 0.96μg/l among men aged ≥40years and increased from 0.74μg/l for men 40-49years, to 1.82μg/l for men 80years and older. Non-Hispanic Whites had lower age-adjusted mean tPSA (1.03μg/l) and cPSA (0.56μg/l) than non-Hispanic Blacks (tPSA 1.25μg/l and cPSA 0.72μg/l). Obese men had lower age-adjusted mean total, free and complexed PSAs (0.94, 0.27, and 0.51μg/l, respectively) than men with normal BMI (tPSA 1.21, fPSA 0.32, and cPSA 0.68μg/l, respectively).

CONCLUSION

Total, free and complexed PSAs increased with age; tPSA and cPSAs were highest in non-Hispanic Blacks; and total, free, and complexed PSAs were lowest in obese men.

Chirality-based Au@Ag Nanorod Dimers Sensor for Ultrasensitive PSA Detection

A novel biosensor for ultrasensitive detection of prostate-specific antigen (PSA) was established based on gold nanorod (Au NR) dimers assembly. The circular dichroism signal was significantly amplified by a silver shell depositing on the surface of the Au NR dimers. A low limit of detection of 0.076 aM and high specificity were observed within the range of 0.1 to 50 aM target PSA. The developed biosensor has the potential to serve as a general platform for the detection of cancer biomarkers.

General strategy for biodetection in high ionic strength solutions using transistor-based nanoelectronic sensors

Transistor-based nanoelectronic sensors are capable of label-free real-time chemical and biological detection with high sensitivity and spatial resolution, although the short Debye screening length in high ionic strength solutions has made difficult applications relevant to physiological conditions. Here, we describe a new and general strategy to overcome this challenge for field-effect transistor (FET) sensors that involves incorporating a porous and biomolecule permeable polymer layer on the FET sensor. This polymer layer increases the effective screening length in the region immediately adjacent to the device surface and thereby enables detection of biomolecules in high ionic strength solutions in real-time. Studies of silicon nanowire field-effect transistors with additional polyethylene glycol (PEG) modification show that prostate specific antigen (PSA) can be readily detected in solutions with phosphate buffer (PB) concentrations as high as 150 mM, while similar devices without PEG modification only exhibit detectable signals for concentrations ≤10 mM. Concentration-dependent measurements exhibited real-time detection of PSA with a sensitivity of at least 10 nM in 100 mM PB with linear response up to the highest (1000 nM) PSA concentrations tested. The current work represents an important step toward general application of transistor-based nanoelectronic detectors for biochemical sensing in physiological environments and is expected to open up exciting opportunities for in vitro and in vivo biological sensing relevant to basic biology research through medicine.

Serum fucosylated prostate-specific antigen (PSA) improves the differentiation of aggressive from non-aggressive prostate cancers

BACKGROUND

Clinically, it is still challenging to differentiate aggressive from non-aggressive prostate cancers (Pca) by non-invasive approaches. Our recent studies showed that overexpression of alpha (1-6) fucosyltransferase played an important role in Pca cells. In this study, we have investigated levels of glycoproteins and their fucosylated glycoforms in sera of Pca patients, as well as the potential utility of fucosylated glycoproteins in the identification of aggressive Pca.

MATERIAL AND METHODS

Serum samples from histomorphology-proven Pca cases were included. Prostate-specific antigen (PSA), tissue inhibitor of metallopeptidase 1 (TIMP1) and tissue plasminogen activator (tPA), and their fucosylated glycoforms were captured by Aleuria Aurantia Lectin (AAL), followed by the multiplex magnetic bead-based immunoassay. The level of fucosylated glycoproteins was correlated with patients' Gleason score of the tumor.

RESULT

Among three fucosylated glycoproteins, the fucosylated PSA was significantly increased and correlated with the tumor Gleason score (p<0.05). The ratio of fucosylated PSA showed a marked increase in aggressive tumors in comparison to non-aggressive tumors. ROC analysis also showed an improved predictive power of fucosylated PSA in the identification of aggressive Pca.

CONCLUSIONS

Our data demonstrated that fucosylated PSA has a better predictive power to differentiate aggressive tumors from non-aggressive tumors, than that of native PSA and two other glycoproteins. The fucosylated PSA has the potential to be used as a surrogate biomarker.

Are hormonal contraceptive users more likely to misreport unprotected sex? Evidence from a biomarker validation study in Zimbabwe

We analyzed biomarker validation data of unprotected sex from women in Zimbabwe to determine whether condom and sexual behavior misreporting differs between users of different contraceptive methods. Self-reported sexual behavior was compared with the presence of prostate-specific antigen (PSA) in vaginal fluid, a biomarker of semen exposure. Of the 195 women who were PSA positive, 94 (48 %) reported no sex or only condom-protected sex. Hormonal contraceptive users misreported sexual behavior less than women using non-hormonal methods (45 vs. 67 %, P = 0.03). This misclassification pattern could have implications on the elevated risk of HIV infection associated with hormonal contraception in some studies.

Towards engineering hormone-binding globulins as drug delivery agents

The treatment of many diseases such as cancer requires the use of drugs that can cause severe side effects. Off-target toxicity can often be reduced simply by directing the drugs specifically to sites of diseases. Amidst increasingly sophisticated methods of targeted drug delivery, we observed that Nature has already evolved elegant means of sending biological molecules to where they are needed. One such example is corticosteroid binding globulin (CBG), the major carrier of the anti-inflammatory hormone, cortisol. Targeted release of cortisol is triggered by cleavage of CBG's reactive centre loop by elastase, a protease released by neutrophils in inflamed tissues. This work aimed to establish the feasibility of exploiting this mechanism to carry therapeutic agents to defined locations. The reactive centre loop of CBG was altered with site-directed mutagenesis to favour cleavage by other proteases, to alter the sites at which it would release its cargo. Mutagenesis succeeded in making CBG a substrate for either prostate specific antigen (PSA), a prostate-specific serine protease, or thrombin, a key protease in the blood coagulation cascade. PSA is conspicuously overproduced in prostatic hyperplasia and is, therefore, a good way of targeting hyperplastic prostate tissues. Thrombin is released during clotting and consequently is ideal for conferring specificity to thrombotic sites. Using fluorescence-based titration assays, we also showed that CBG can be engineered to bind a new compound, thyroxine-6-carboxyfluorescein, instead of its physiological ligand, cortisol, thereby demonstrating that it is possible to tailor the hormone binding site to deliver a therapeutic drug. In addition, we proved that the efficiency with which CBG releases bound ligand can be increased by introducing some well-placed mutations. This proof-of-concept study has raised the prospect of a novel means of targeted drug delivery, using the serpin conformational change to combat the problem of off-target effects in the treatment of diseases.

Direct ultrasensitive electrical detection of prostate cancer biomarkers with CMOS-compatible n- and p-type silicon nanowire sensor arrays

Sensitive and quantitative analysis of proteins is central to disease diagnosis, drug screening, and proteomic studies. Here, a label-free, real-time, simultaneous and ultrasensitive prostate-specific antigen (PSA) sensor was developed using CMOS-compatible silicon nanowire field effect transistors (SiNW FET). Highly responsive n- and p-type SiNW arrays were fabricated and integrated on a single chip with a complementary metal oxide semiconductor (CMOS) compatible anisotropic self-stop etching technique which eliminated the need for a hybrid method. The incorporated n- and p-type nanowires revealed complementary electrical response upon PSA binding, providing a unique means of internal control for sensing signal verification. The highly selective, simultaneous and multiplexed detection of PSA marker at attomolar concentrations, a level useful for clinical diagnosis of prostate cancer, was demonstrated. The detection ability was corroborated to be effective by comparing the detection results at different pH values. Furthermore, the real-time measurement was also carried out in a clinically relevant sample of blood serum, indicating the practicable development of rapid, robust, high-performance, and low-cost diagnostic systems.

Characterization of the prostate-specific antigen (PSA) catalytic mechanism: a pre-steady-state and steady-state study

Prostate-specific antigen (PSA), an enzyme of 30 kDa grouped in the kallikrein family is synthesized to high levels by normal and malignant prostate epithelial cells. Therefore, it is the main biomarker currently used for early diagnosis of prostate cancer. Here, presteady-state and steady-state kinetics of the PSA-catalyzed hydrolysis of the fluorogenic substrate Mu-His-Ser-Ser-Lys-Leu-Gln-AMC (spanning from pH 6.5 to pH 9.0, at 37.0°C) are reported. Steady-state kinetics display at every pH value a peculiar feature, represented by an initial "burst" phase of the fluorescence signal before steady-state conditions are taking place. This behavior, which has been already observed in other members of the kallikrein family, suggests the occurrence of a proteolytic mechanism wherefore the acylation step is faster than the deacylation process. This feature allows to detect the acyl intermediate, where the newly formed C-terminal carboxylic acid of the cleaved substrate forms an ester bond with the -OH group of the Ser195 catalytic residue, whereas the AMC product has been already released. Therefore, the pH-dependence of the two enzymatic steps (i.e., acylation and deacylation) has been separately characterized, allowing the determination of pKa values. On this basis, possible residues are tentatively identified in PSA, which might regulate these two steps by interacting with the two portions of the substrate.

[The practical application of marker -2proPSA and health index of prostate phi in diagnostics of prostate cancer]

The article demonstrates that prostate-specific antigen (PSA) has some limitations in detection of cancer of prostate. It was demonstrated that isoform of free PSA - 2proPSA has higher specificity in comparison with total PSA (tPSA) and percentage tPSA and free PSA (%free PSA) in detection of cancer of prostate. The application of Prostate Health Index including such indicators as -2PSA, free PSA and tPSA makes it possible to increase degree of detection of cancer of prostate, to increase specificity and to decrease number of optional biopsies. Besides, correlation was established between value of Prostate Health Index and degree of aggressiveness of forms of cancer of prostate.

Identification of a novel proteoform of prostate specific antigen (SNP-L132I) in clinical samples by multiple reaction monitoring

Prostate specific antigen (PSA) is a well-established tumor marker that is frequently employed as model biomarker in the development and evaluation of emerging quantitative proteomics techniques, partially as a result of wide access to commercialized immunoassays serving as "gold standards." We designed a multiple reaction monitoring (MRM) assay to detect PSA proteoforms in clinical samples (n = 72), utilizing the specificity and sensitivity of the method. We report, for the first time, a PSA proteoform coded by SNP-L132I (rs2003783) that was observed in nine samples in both heterozygous (n = 7) and homozygous (n = 2) expression profiles. Other isoforms of PSA, derived from protein databases, were not identified by four unique proteotypic tryptic peptides. We have also utilized our MRM assay for precise quantitative analysis of PSA concentrations in both seminal and blood plasma samples. The analytical performance was evaluated, and close agreement was noted between quantitations based on three selected peptides (LSEPAELTDAVK, IVGGWECEK, and SVILLGR) and a routinely used commercialized immunoassay. Additionally, we disclose that the peptide IVGGWECEK is shared with kallikrein-related peptidase 2 and therefore is not unique for PSA. Thus, we propose the use of another tryptic sequence (SVILLGR) for accurate MRM quantification of PSA in clinical samples.

PSA-responsive and PSMA-mediated multifunctional liposomes for targeted therapy of prostate cancer

In the hormone-refractory stage of prostate cancer (PC), the expression of prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) often remains highly active. Accumulating studies have demonstrated that these two proteins are attractive targets for specific delivery of functional molecules to advanced PC, not merely as potential sensitive markers for PC detection. In this study, we constructed a dual-modified liposome that incorporated PSA-responsive and PSMA-mediated liposomes and potentially offers double selectivity for PC. The folate moiety binds quickly to PSMA-positive tumors, and the PSA-responsive moiety is cleaved by PSA that was enriched in tumor tissues. The activated liposomes (folate and cell-penetrating peptides dual-modifications) are subsequently taken up by the tumor cells via polyarginine's penetrating effects and receptor-mediated endocytosis. To corroborate these assumptions, a series of experiments were conducted, including PSA-responsive peptide hydrolysis kinetics, cellular uptake, internalization mechanism and escape from endosomes in PC-3 and/or 22Rv1 cells, biodistribution and antitumor activity of siRNA-loaded liposomes after systemic administration, gene silencing and cell apoptosis in vitro and in vivo. The results reveal that multivalent interactions play a key role in enhancing PC cell recognition and uptake while reducing nonspecific uptake. The dual-modified liposomes carrying small interfering RNA (siRNA) have significant advantages over the control liposomes, including single-modified (folate, CPP, PSA-responsive only) and non-modified liposomes. The dual-modified liposomes elevated cellular uptake, downregulated expression of polo-like kinase 1 (PLK-1) and augmented cell apoptosis in prostate tumor cells. The entry of the dual-modified liposomes into 22Rv1 cells occurred via multiple endocytic pathways, including clathrin-mediated endocytosis and macropinocytosis, followed by an effective endosomal escape of the entrapped siRNA into the cytoplasm. In vivo studies conducted on a 22Rv1 xenograft murine model demonstrated that the dual-modified liposomes demonstrated the maximized accumulation, retention and knockdown of PLK-1 in tumor cells, as well as the strongest inhibition of tumor growth and induction of tumor cell apoptosis. In terms of targeting capacity and therapeutic potency, the combination of a PSA-responsive and PSMA-mediated liposome presents a promising platform for therapy and diagnosis of PSMA/PSA-positive PC.

[Histological changes of the prostate and acute urinary retention in patients with benign prostatic hyperplasia]

OBJECTIVE

To investigate the roles of prostatic infarction, prostatic inflammation and the type of prostatic hyperplasia in acute urinary retention (AUR) in patients with benign prostatic hyperplasia (BPH).

METHODS

We retrospectively analyzed 102 cases of BPH, 49 complicated by AUR and the other 53 without AUR. We compared the incidences of prostatic infarction and prostatic inflammation, the types of prostatic hyperplasia, the patients' age, the level of prostate specific antigen (PSA), the prostate volume, and international prostate symptom score (IPSS) between the AUR and non-AUR groups.

RESULTS

The PSA level was significantly increased in the AUR group as compared with the non-AUR group (P < 0.05). There were no statistically significant differences between the two groups in the mean age, prostate volume and IPSS (P > 0.05). The type of prostatic hyperplasia showed no correlation with AUR. The incidence rate of AUR was 5.620 and 2.326 times higher in the BPH patients with prostatic infarction and prostatic inflammation respectively than in those without (P < 0.05).

CONCLUSION

Prostatic infarction and prostatic inflammation are important risk factors of AUR in BPH patients.

PSMA-targeted theranostic nanoplex for prostate cancer therapy

Theranostic imaging, where diagnosis is combined with therapy, is particularly suitable for a disease that is as complex as cancer, especially now that genomic and proteomic profiling can provide an extensive "fingerprint" of each tumor. With such information, theranostic agents can be designed to personalize treatment and minimize damage to normal tissue. Here we have developed a nanoplex platform for theranostic imaging of prostate cancer (PCa). In these proof-of-principle studies, a therapeutic nanoplex containing multimodal imaging reporters was targeted to prostate-specific membrane antigen (PSMA), which is expressed on the cell surface of castrate-resistant PCa. The nanoplex was designed to deliver small interfering RNA (siRNA) along with a prodrug enzyme to PSMA-expressing tumors. Each component of the nanoplex was carefully selected to evaluate its diagnostic aspect of PSMA imaging and its therapeutic aspects of siRNA-mediated down-regulation of a target gene and the conversion of a prodrug to cytotoxic drug, using noninvasive multimodality imaging. Studies performed using two variants of human PC3-PCa cells and tumors, one with high PSMA expression level and another with negligible expression levels, demonstrated PSMA-specific uptake. In addition, down-regulation of the selected siRNA target, choline kinase (Chk), and the conversion of the nontoxic prodrug 5-fluorocytosine (5-FC) to cytotoxic 5-fluorouracil (5-FU) were also demonstrated with noninvasive imaging. The nanoplex was well-tolerated and did not induce liver or kidney toxicity or a significant immune response. The nanoplex platform described can be easily modified and applied to different cancers, receptors, and pathways to achieve theranostic imaging, as a single agent or in combination with other treatment modalities.

Quantitative RT-PCR analysis of PSA and prostate-specific membrane antigen mRNA to detect circulating tumor cells improves recurrence-free survival nomogram prediction after radical prostatectomy

BACKGROUND

Circulating tumor cell (CTC) analysis is a potential new biomarker in prostate cancer. We hypothesize that quantitative detection of CTCs in patients pre- and post-radical prostatectomy (RP) using quantitative TaqMan® fluorogenic RT-PCR will improve the accuracy of the Kattan nomogram to predict the probability of recurrence-free survival (RFS) post-RP.

METHODS

Ninty-two patients who underwent RP between 2004 and 2009 had venous blood samples taken pre- (Day - 1) and post-operatively (Day + 7). We performed quantitative Taqman® RT-PCR to detect circulating prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) mRNA. We calculated both the logarithmic ratio of Day + 7/Day - 1 for PSA (PSAr) and PSMA (PSMAr) expression (log(Day+7/Day-1) ) and the Kattan nomogram predicted probability of disease recurrence for each patient. We then analyzed how the AUC-ROC analysis for the Kattan nomogram prediction alone (K) compared to the addition of the PSAr and PSMAr in predicting 5-year RFS.

RESULTS

The mean age (years), PSA (ng/ml), and follow-up (mo) was 65.1, 9.13, and 72, respectively. The AUCs for K, PSAr + K, and PSMAr + K were 0.752 (95%CI 0.620-0.860), 0.830 (95%CI 0.740-0.911), and 0.837 (95%CI 0.613-0.923), respectively (P = 0.03). The Kattan 5-year PSA RFS was 75%. The actual 5-year PSA RFS survival rate was 77%.

CONCLUSIONS

Data from modern quantitative RT-PCR to detect circulating prostate-derived PSA and PSM mRNA pre- and post-RP improves the accuracy of the Kattan nomogram to predict biochemical recurrence.

Kinetic and structural studies on the interactions of heparin and proteins of human seminal plasma using surface plasmon resonance

Heparin is naturally occurring polysaccharides which interacts with seminal plasma proteins and regulate multiple steps in fertilization process. Qualitative and quantitative information regarding the affinity for heparin-seminal plasma proteins interactions is not generally well documented and there are no reports of a comprehensive analysis of these interactions in human seminal plasma. Such information should improve our understanding of how GAGs especially heparin present in the reproductive tract regulate fertilization. In this study, we use SPR to study interactions of heparin with various seminal plasma heparin-binding proteins (HBPs). HBPs like lactoferrin (LF), fibronectin fragment (FNIII), semenogelinI (SGI) and prostate specific antigen (PSA) all bind heparin with different binding kinetics and affinities. Kinetic data suggests that FNIII binds heparin with a high affinity (KD=3.2 nM), while PSA binds heparin with a micromolar affinity (KD=11.1 μM). Preincubation of SGI with heparin inhibits the binding of SGI to immobilized PSA in a dose-dependent manner, while FNIII incubated with heparin binds with an increased affinity to PSA. Solution-competition studies show that the minimum size of a heparin oligosaccharide capable of binding with PSA is greater than a tetrasaccharide, with LF and SGI is larger than a hexasaccharide and for FNIII is larger than an octasaccharide.

Isolation and detection of single molecules on paramagnetic beads using sequential fluid flows in microfabricated polymer array assemblies

We report a method for isolating individual paramagnetic beads in arrays of femtolitre-sized wells and detecting single enzyme-labeled proteins on these beads using sequential fluid flows in microfabricated polymer array assemblies. Arrays of femtolitre-sized wells were fabricated in cyclic olefin polymer (COP) using injection moulding based on DVD manufacturing. These arrays were bonded to a complementary fluidic structure that was also moulded in COP to create an enclosed device to allow delivery of liquids to the arrays. Enzyme-associated, paramagnetic beads suspended in aqueous solutions of enzyme substrate were delivered fluidically to the array such that one bead per well was loaded by gravity. A fluorocarbon oil was then flowed into the device to remove excess beads from the surface of the array, and to seal and isolate the femtolitre-sized wells containing beads and enzyme substrate. The device was then imaged using standard fluorescence imaging to determine which wells contained single enzyme molecules. The analytical performance of this device as the detector for digital ELISA compared favourably to the standard method, i.e., glass arrays mechanically sealed against a silicone gasket; prostate specific antigen (PSA) could be detected from 0.011 pg mL(-1) up to 100 pg mL(-1). The use of an enclosed fluidic device to isolate beads in single-molecule arrays offers a multitude of advantages for low-cost manufacturing, ease of automation, and instrument development to enable applications in biomarker validation and medical diagnosis.

Selective enrichment and sensitive detection of peptide and protein biomarkers in human serum using polymeric reverse micelles and MALDI-MS

Reverse-micelle forming amphiphilic homopolymers with carboxylic acid and quaternary amine substituents are used to selectively enrich biomarker peptides and protein fragments from human serum prior to matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis. After depletion of human serum albumin (HSA) and immunoglobulin G (IgG), low abundance peptide biomarkers can be selectively enriched and detected by MALDI-MS at clinically relevant concentrations by using the appropriate homopolymer(s) and extraction pH value(s). Three breast cancer peptide biomarkers, bradykinin, C4a, and ITIH(4), were chosen to test this new approach, and detection limits of 0.5 ng mL(-1), 0.08 ng mL(-1), and 0.2 ng mL(-1), respectively, were obtained. In addition, the amphiphilic homopolymers were used to detect prostate specific antigen (PSA) at concentrations as low as 0.5 ng mL(-1) by targeting a surrogate peptide fragment of this protein biomarker. Selective enrichment and sensitive MS detection of low abundance peptide/protein biomarkers by these polymeric reverse micelles should be a sensitive and straightforward approach for biomarker screening in human serum.

N-glycans of human protein C inhibitor: tissue-specific expression and function

Protein C inhibitor (PCI) is a serpin type of serine protease inhibitor that is found in many tissues and fluids in human, including blood plasma, seminal plasma and urine. This inhibitor displays an unusually broad protease specificity compared with other serpins. Previous studies have shown that the N-glycan(s) and the NH₂-terminus affect some blood-related functions of PCI. In this study, we have for the first time determined the N-glycan profile of seminal plasma PCI, by mass spectrometry. The N-glycan structures differed markedly compared with those of both blood-derived and urinary PCI, providing evidence that the N-glycans of PCI are expressed in a tissue-specific manner. The most abundant structure (m/z 2592.9) had a composition of Fuc₃Hex₅HexNAc₄, consistent with a core fucosylated bi-antennary glycan with terminal Lewis^x. A major serine protease in semen, prostate specific antigen (PSA), was used to evaluate the effects of N-glycans and the NH₂-terminus on a PCI function related to the reproductive tract. Second-order rate constants for PSA inhibition by PCI were 4.3±0.2 and 4.1±0.5 M⁻¹s⁻¹ for the natural full-length PCI and a form lacking six amino acids at the NH₂-terminus, respectively, whereas these constants were 4.8±0.1 and 29±7 M⁻¹s⁻¹ for the corresponding PNGase F-treated forms. The 7–8-fold higher rate constants obtained when both the N-glycans and the NH₂-terminus had been removed suggest that these structures jointly affect the rate of PSA inhibition, presumably by together hindering conformational changes of PCI required to bind to the catalytic pocket of PSA.

Crystal structure of human prostate-specific antigen in a sandwich antibody complex

Human prostate-specific antigen (PSA or human kallikrein-related peptidase 3) present in small quantities in the sera of healthy men becomes elevated in prostate cancer (PCa) and other prostate disorders. The ability to identify the free PSA fraction associated with PCa could increase the reliability of the PSA diagnostic test. Here we present the crystal structure of human PSA from seminal fluid in a sandwich complex with two monoclonal antibodies (mAbs). MAb 5D5A5 captures total PSA with exceptionally high affinity, and mAb 5D3D11 selectively discriminates between free PSA subforms that are more abundant in sera from patients with PCa. Although the antigen is not of seric origin, several insights into cancer diagnosis can be discerned from this complex. MAb 5D3D11 recognizes a PSA conformation different from that previously reported. Interacting with the kallikrein loop, the PSA N-linked glycan attached to asparagine 61 is an uncommonly complex sialated triantennary chain. O-linked glycosylation is observed at threonine 125. The description of how PSA subforms in prostatic fluid can be discriminated using pairs of antibodies is a first step in the design of new strategies that are capable of real discrimination among PSA subforms, which will lead to the formulation of more reliable diagnostic tests. In a companion article [Muller, B. H., Savatier, A., L'Hostis, G., Costa, N., Bossus, M., Michel, S., et al. (2011). In vitro affinity maturation of an anti-PSA antibody for prostate cancer diagnostic assay. J. Mol. Biol.], we describe engineering efforts to improve the affinity of mAb 5D3D11, a first step towards such goal.

[Usefulness of prostatic specific antigen (PSA) for diagnosis and staging of patients with prostate cancer]

The incorporation of prostatic specific antigen (PSA) to clinical practice revolutionized diagnosis and modified the epidemiology of prostate cancer(PCa). Although it lacks of many of the characteristics of an ideal tumor marker, it is the marker most used for diagnosis and follow up of any type of cancer. It represents the best clinical tool we currently have available for screening and staging of PCa. On the contrary, the greatest limitation PSA presents is its lack of tumor specificity. The use of PSA molecular derivatives and isoforms tries to solve, at least in part, its limitations. As a matter of fact, the use of % free PSA and PSAD significantly increases the test specificity for diagnosis and, the use of derivatives evaluating PSA temporary kinetics (PSAV and PSADT) represent very useful tools to estimate líquiprognosis during disease treatment and follow up. With the ongoing development of new markers for PCa, It is likely the role of PSA in diagnosis and staging of the disease will be modified.

A new method for non-labeling attomolar detection of diseases based on an individual gold nanorod immunosensor

Herein, we present the use of a single gold nanorod sensor for detection of diseases on an antibody-functionalized surface, based on antibody-antigen interaction and the localized surface plasmon resonance (LSPR) λ(max) shifts of the resonant Rayleigh light scattering spectra. By replacing the cetyltrimethylammonium bromide (CTAB), a tightly packed self-assembled monolayer of HS(CH(2))(11)(OCH(2)CH(2))(6)OCH(2)COOH(OEG(6)) has been successfully formed on the gold nanorod surface prior to the LSPR sensing, leading to the successful fabrication of individual gold nanorod immunosensors. Using prostate specific antigen (PSA) as a protein biomarker, the lowest concentration experimentally detected was as low as 111 aM, corresponding to a 2.79 nm LSPR λ(max) shift. These results indicate that the detection platform is very sensitive and outperforms detection limits of commercial tests for PSA so far. Correlatively, its detection limit can be equally compared to the assays based on DNA biobarcodes. This study shows that a gold nanorod has been used as a single nanobiosensor to detect antigens for the first time; and the detection method based on the resonant Rayleigh scattering spectrum of individual gold nanorods enables a simple, label-free detection with ultrahigh sensitivity.

Prostate-specific antigen/solvent interaction analysis: a preliminary evaluation of a new assay concept for detecting prostate cancer using urinary samples

OBJECTIVE

To provide preliminary clinical performance evaluation of a novel prostate cancer (CaP) assay, prostate-specific antigen/solvent interaction analysis (PSA/SIA) that focused on changes to the structure of PSA.

METHODS

Two-hundred twenty-two men undergoing prostate biopsy for accepted clinical criteria at 3 sites (University Hospitals Case Medical Center in Cleveland, Cleveland Clinic, and Veterans Administration Boston Healthcare System) were enrolled in institutional review board-approved study. Before transrectal ultrasound-guided biopsy, patients received digital rectal examination with systematic prostate massage followed by collection of urine. The PSA/SIA assay determined the relative partitioning of heterogeneous PSA isoform populations in urine between 2 aqueous phases. A structural index, K, whose numerical value is defined as the ratio of the concentration of all PSA isoforms, was determined by total PSA enzyme-linked immunosorbent assay and used to set a diagnostic threshold for CaP. Performance was assessed using receiver operating characteristic (ROC) analysis with biopsy as the gold standard.

RESULTS

Biopsies were pathologically classified as case (malignant, n=100) or control (benign, n=122). ROC performance demonstrated area under the curve=0.90 for PSA/SIA and 0.58 for serum total PSA. At a cutoff value of k=1.73, PSA/SIA displayed sensitivity=100%, specificity=80.3%, positive predictive value=80.6%, and negative predictive value=100%. No attempt was made in this preliminary study to further control patient population or selection criteria for biopsy, nor did we analytically investigate the type of structural differences in PSA that led to changes in k value.

CONCLUSION

PSA/SIA provides ratiometric information independently of PSA concentration. In this preliminary study, analysis of the overall structurally heterogeneous PSA isoform population using the SIA assay showed promising results to be further evaluated in future studies.

Specific cell targeting with nanobody conjugated branched gold nanoparticles for photothermal therapy

Branched gold nanoparticles are potential photothermal therapy agents because of their large absorption cross section in the near-infrared window. Upon laser irradiation they produce enough heat to destroy tumor cells. In this work, branched gold nanoparticles are biofunctionalized with nanobodies, the smallest fully functional antigen-binding fragments evolved from the variable domain, the VHH, of a camel heavy chain-only antibody. These nanobodies bind to the HER2 antigen which is highly expressed on breast and ovarian cancer cells. Flow cytometric analysis and dark field images of HER2 positive SKOV3 cells incubated with anti-HER2 conjugated branched gold nanoparticles show specific cell targeting. Laser irradiation studies reveal that HER2 positive SKOV3 cells exposed to the anti-HER2 targeted branched gold nanoparticles are destroyed after five minutes of laser treatment at 38 W/cm(2) using a 690 nm continuous wave laser. Starting from a nanoparticle optical density of 4, cell death is observed, whereas the control samples, nanoparticles with anti-PSA nanobodies, nanoparticles only, and laser only, do not show any cell death. These results suggest that this new type of bioconjugated branched gold nanoparticles are effective antigen-targeted photothermal therapeutic agents for cancer treatment.

Enzymatic triggered release of an HIV-1 entry inhibitor from prostate specific antigen degradable microparticles

This paper describes the design, construction and characterization of the first anti-HIV drug delivery system that is triggered to release its contents in the presence of human semen. Microgel particles were synthesized with a crosslinker containing a peptide substrate for the seminal serine protease prostate specific antigen (PSA) and were loaded with the HIV-1 entry inhibitor sodium poly(styrene-4-sulfonate) (pSS). The particles were composed of N-2-hydroxyproplymethacrylamide and bis-methacrylamide functionalized peptides based on the PSA substrates GISSFYSSK and GISSQYSSK. Exposure to human seminal plasma (HSP) degraded the microgel network and triggered the release of the entrapped antiviral polymer. Particles with the crosslinker composed of the substrate GISSFYSSK showed 17 times faster degradation in seminal plasma than that of the crosslinker composed of GISSQYSSK. The microgel particles containing 1 mol% GISSFYSSK peptide crosslinker showed complete degradation in 30 h in the presence of HSP at 37°C and pSS released from the microgels within 30 min reached a concentration of 10 μg/mL, equivalent to the published IC(90) for pSS. The released pSS inactivated HIV-1 in the presence of HSP. The solid phase synthesis of the crosslinkers, preparation of the particles by inverse microemulsion polymerization, HSP-triggered release of pSS and inactivation of HIV-1 studies are described.

Simultaneous analysis of glycosylated and sialylated prostate-specific antigen revealing differential distribution of glycosylated prostate-specific antigen isoforms in prostate cancer tissues

Aberrant protein glycosylation has been shown to be associated with disease progression and can be potentially useful as a biomarker if disease-specific glycosylation can be identified. However, high-throughput quantitative analysis of protein glycosylation derived from clinical specimens presents technical challenges due to the typically high complexity of biological samples. In this study, a mass spectrometry-based analytical method was developed to measure different glycosylated forms of glycoproteins from complex biological samples by coupling glycopeptide extraction strategy for specific glycosylation with selected reaction monitoring (SRM). Using this method, we monitored glycosylated and sialylated prostate-specific antigen (PSA) in prostate cancer and noncancer tissues. Results of this study demonstrated that the relative abundance of glycosylated PSA isoforms were not correlated with total PSA protein levels measured in the same prostate cancer tissue samples by clinical immunoassay. Furthermore, the sialylated PSA was differentially distributed in cancer and noncancer tissues. These data suggest that differently glycosylated isoforms of glycoproteins can be quantitatively analyzed and may provide unique information for clinically relevant studies.

A remote arene-binding site on prostate specific membrane antigen revealed by antibody-recruiting small molecules

Prostate specific membrane antigen (PSMA) is a membrane-bound glutamate carboxypeptidase overexpressed in many forms of prostate cancer. Our laboratory has recently disclosed a class of small molecules, called ARM-Ps (antibody-recruiting molecule targeting prostate cancer) that are capable of enhancing antibody-mediated immune recognition of prostate cancer cells. Interestingly, during the course of these studies, we found ARM-Ps to exhibit extraordinarily high potencies toward PSMA, compared to previously reported inhibitors. Here, we report in-depth biochemical, crystallographic, and computational investigations which elucidate the origin of the observed affinity enhancement. These studies reveal a previously unreported arene-binding site on PSMA, which we believe participates in an aromatic stacking interaction with ARMs. Although this site is composed of only a few amino acid residues, it drastically enhances small molecule binding affinity. These results provide critical insights into the design of PSMA-targeted small molecules for prostate cancer diagnosis and treatment; more broadly, the presence of similar arene-binding sites throughout the proteome could prove widely enabling in the optimization of small molecule-protein interactions.

TP53 gene mutations in prostate cancer progression

BACKGROUND

We assessed the predictive value of TP53 mutations and prostate-specific antigen (PSA) for tumor progression in prostate cancer (PCa) patients.

MATERIALS AND METHODS

Ninety tumor tissue samples of patients with PCa from radical prostatectomy were used. Tumor progression was estimated biochemically by the PSA level (> 0.2 microg/l) or by detection of metastases. Screening for TP53 mutations was performed by temperature gradient gel electrophoresis (TGGE) in exon-specific manner. Follow-up data were collected from medical protocols. Statistical analysis was performed by uni- and multivariate techniques.

RESULTS

In 32 out of 90 patients (35.6%), TP53 mutations were detected. Thirteen out of 32 patients (40.6%) with TP53 mutations and nine out of 58 patients (15.5%) with TP53 wild-type showed tumor progression after 25 and 45 months, respectively.

CONCLUSION

TP53 mutations in exon 7 and exon 8 are factors of tumor progression in PCa. Their contribution to tumor recurrence is more significant than tumor stage and pretherapeutic PSA level.

alpha1,2-Fucosylated and beta-N-acetylgalactosaminylated prostate-specific antigen as an efficient marker of prostatic cancer

A prostate-specific antigen (PSA) is widely used as a diagnostic marker for prostate cancer (PC) because of its high specificity. However, elevated serum PSA does not occur only in PC but also in benign prostatic hyperplasia (BPH). Since the structural changes of N-glycans during carcinogenesis are common phenomena, we investigated whether PC-specific N-glycans are linked to PSA. We first analyzed the carbohydrate structures of PSA derived from seminal fluid, serum of BPH and PC patients, and PC cell line, namely, LNCaP using eight lectin-immobilized columns and then with enzyme-linked immunosorbent assay (ELISA). The fraction of serum PSA from PC patients bound to both Fucalpha1-2Gal and betaGalNAc binding Trichosanthes japonica agglutinin-II (TJA-II) column, while that from BPH patients did not exhibit this binding ability, thereby implying that there is elevated expression of alpha1,2-fucosylation and beta-N-acetylgalactosaminylation of PSA during carcinogenesis. We then performed a real-time polymerase chain reaction (PCR) and confirmed that these structural changes were responsible for the elevated expression of fucosyltransferase I (FUT1) and beta-N-acetylgalactosaminyltransferase 4(B4GALNT4). Second, we measured TJA-II-bound PSA contents and the binding ratios of TJA-II column chromatography in serum PSA samples from 40 patients of both PC and BPH. The results indicated that both TJA-II-bound PSA content and TJA-II binding ratios (%) could be used to discriminate between PC and BPH with more than 95% probability, and TJA-II-bound PSA can be regarded as a potential marker of PC.

Evaluation of the ALiPHAT method for PC-IDMS and correlation of limits-of-detection with nonpolar surface area

PC-IDMS experiments for two peptides, laminin nonapeptide and the N-terminal tryptic peptide of prostate specific antigen, were performed utilizing a variety of alkylating reagents. These experiments were conducted to investigate how hydrophobicity influences the limits-of-detection (LOD) by altering their electrospray ionization response. Nonpolar surface areas were calculated for both peptides and all alkylating reagents to provide an estimate of the hydrophobicity of the differently alkylated peptides. Decreases in LOD by 2-fold were observed for both peptides between the best and worst performing combination of alkylating reagent. However, while an increase in hydrophobicity was found to aid in decreasing LOD to an extent, beyond a certain hydrophobicity, we observed a decrease.