Prostate-specific antigen and prostatic acid phosphatase: biomolecular and physiologic characteristics

Immunotherapy with GcMAF revisited - A critical overview of the research of Nobuto Yamamoto

This overview describes the research of Nobutu Yamamoto (Philadelphia) concerning immunotherapy with GcMAF for patients with cancer and for patients infected with pathogenic envelope viruses. GcMAF (Group-specific component Macrophage-Activating Factor) is a mammalian protein with an incredible potency to directly activate macrophages. Since the late 1980s Yamamoto's investigations were published in numerous journals but in order to understand the details of his research, a minute survey of many of his patents was required. But even then, regrettably, a precise description of his experiments was sometimes lacking. This overview tries to summarize all of Yamamoto's research on GcMAF, as well as some selected more recent papers from other investigators, who tried to verify and/or reproduce Yamamoto's reports. In my opinion the most important result of the GcMAF research deserves widespread renewed attention: human GcMAF injections (100 ng per week, intramuscular or intravenous) can help to cure patients with a great variety of cancers as well as patients infected with pathogenic envelope viruses like the human immunodeficiency virus 1 (HIV-1), influenza, measles and rubella (and maybe also SARS-CoV-2). From Yamamoto's data it can be calculated that GcMAF is a near-stoichiometric activator of macrophages. Yamamoto monitored the progress of his immunotherapy via the serum level of an enzyme called nagalase (α-N-acetylgalactosaminidase activity at pH 6). I have extensively discussed the properties and potential catalytic site of this enzyme activity in an Appendix entitled: "Search for the potential active site of the latent α-N-acetylgalactosaminidase activity in the glycoproteins of some envelope viruses".

Can Computed Tomography Perfusion Predict Treatment Response After Prostate Artery Embolization: A Feasibility Study

Prostate artery embolization (PAE) is an emerging therapy for benign prostatic hyperplasia (BPH). Optimal patient selection is an important step when introducing new treatments and several characteristics associated with a good clinical outcome has previously been proposed. However, no prognostic tool is yet available for PAE. Computed tomography perfusion is an imaging technique that provides hemodynamic parameters making it possible to estimate the prostatic blood flow (PBF). This study investigated the relationship between PBF and the response to PAE. A post hoc analysis including prostate-specific antigen (PSA) measurements before and 24-h after embolization from two prospective studies on sixteen patients undergoing PAE with BPH or prostate cancer were performed. The primary outcome was the correlation between baseline PBF and the change in PSA as a surrogate measure of treatment response. Prostate volume strongly correlated with treatment response and the response was greater with incremental amounts of injected embolic material. PBF was not associated with elevation in PSA and added no information that could guide patient selection.

Sexual differences in the sialomes of the zebra tick, Rhipicephalus pulchellus

Ticks rely exclusively on vertebrate blood for their survival. During feeding ticks inject into their hosts a sophisticated salivary potion that overcomes host hemostasis and adverse inflammatory responses. These mediators may also enhance pathogen transmission. Knowledge of the tick salivary protein repertoire may lead to vaccine targets to disrupt feeding and/or parasite transmission as well as to the discovery of novel pharmacological agents. Male saliva may also assist reproduction because males use their mouthparts to lubricate and introduce their spermatophores into the females' genital pore. The analyses of the sialomes of male and female ticks independently allow us to understand the strategy used by each gender to feed successfully. We sequenced cDNA libraries from pools of salivary glands from adult male and female Rhipicephalus pulchellus feeding at different time points, using the Illumina HiSeq protocol. De novo assembly of a total of 241,229,128 paired-end reads lead to extraction of 50,460 coding sequences (CDS), 11,277 of which had more than 75% coverage to known transcripts, or represented novel sequences, and were submitted to GenBank. Additionally, we generated the proteome, from the salivary gland extracts of male and female R. pulchellus, yielding a total of 454 and 2063 proteins respectively which were identified by one or more peptides with at least 95% confidence. The data set is presented as an annotated hyperlinked Excel spreadsheet, describing 121 putative secreted protein families. Female and male specific transcripts were identified.

BIOLOGICAL SIGNIFICANCE

This annotated R. pulchellus database represents a mining field for future experiments involving the resolution of time-dependent transcript expression in this tick species, as well as to define novel vaccine targets and discover novel pharmaceuticals. Gender specific proteins may represent different repertoires of pharmacological reagents to assist feeding by each sex, and in males may represent proteins that assist reproduction similarly to seminal proteins in other animals.

Knockdown of scavenger receptor class B type I reduces prostate specific antigen secretion and viability of prostate cancer cells

BACKGROUND

Scavenger Receptor Class B Type I (SR-BI) facilitates influx of cholesterol to the cell from lipoproteins in the circulation. This influx of cholesterol may be important for many cellular functions, including synthesis of androgens. Castration-resistant prostate cancer tumors are able to synthesize androgens de novo in order to supplement the loss of exogenous sources often induced by androgen deprivation therapy. Silencing of SR-BI may impact the ability of prostate cancer cells, particularly those of castration-resistant state, to maintain the intracellular supply of androgens by removing a supply of cholesterol.

METHODS

SR-BI expression was knocked down using small interfering RNA in LNCaP and C4-2 cells. The effect of down-regulation of SR-BI on PSA production, cell toxicity, and cell viability was measured in both cell types. In addition, compensatory cholesterol synthesis activity was measured using the radiolabeled precursor, (14) C-acetate.

RESULTS

SR-BI protein expression is higher basally in C4-2 cells than LNCaP cells. Silencing of SR-BI expression to greater than 85% reduced PSA production in LNCaP and C4-2 SRBI-KD cells by 55% and 58% compared to negative control cells, respectively. SR-BI-KD C4-2 cells demonstrated significantly reduced cell viability (>25%) compared the NC cells.

CONCLUSIONS

The down-regulation of SR-BI significantly impacts PSA production of prostate cancer cells, as well as the viability of C4-2 cells in the presence and absence of HDL. This may indicate a deficiency in cholesterol availability to the androgen synthesis pathway or may implicate a role for SR-BI in prostate cancer signal transduction pathways.

Attenuation of androgenic regulation by brefeldin A in androgen-responsive prostate cancer cells

OBJECTIVES

To investigate the effects of an antibiotic brefeldin A (BFA) on androgen-regulated cellular events in androgen-responsive prostate cancer cells, focusing on PSA (prostate-specific antigen) status, cell growth, and bioactivity of androgen receptor (AR).

MATERIALS AND METHODS

Androgen-responsive human prostate cancer LNCaP cells were employed and 5α-dihydrotestosterone (DHT) was used as an androgenic mediator to induce androgen-modulated cellular events. Effects of BFA on synthesis and secretion of PSA, cell growth, and AR activity were assessed using Tandem PSA assay, trypan blue exclusion method, and AR binding assay, respectively.

RESULTS

BFA (30 ng/ml) dramatically (90%) blocked secretion of PSA and also reduced cell growth by >75% under non-androgen-regulated condition. Under androgen-stimulated condition using DHT (1 nM), both the cellular and secreted PSA levels as well as cell growth was significantly elevated or stimulated by DHT (compared with controls); however, BFA was capable of completely inhibiting such DHT-stimulated cellular events. In addition, AR binding assay revealed that AR activity has been drastically (~90%) diminished by BFA, likely resulting in interruption of DHT-mediated events.

CONCLUSIONS

BFA is capable of attenuating androgenic regulation in LNCaP cells such as androgen-stimulated PSA synthesis/secretion and cell growth. This BFA-blocked androgen action appears to be primarily attributed to severe inactivation of AR with BFA because AR is a crucial factor for relaying androgenic messages (to DNA). Therefore, BFA could be considered a promising agent for a more effective treatment of hormone-dependent prostate cancer.

Chymotrypsin effects on the determination of sperm parameters and seminal biochemistry markers

BACKGROUND

Few reports of the effects of treatment with chymotrypsin on the determination of sperm parameters and seminal biochemistry markers are documented.

METHODS

Sperm parameters of 63 liquefied and 27 non-liquefied samples, untreated or treated with chymotrypsin, were evaluated using computer-assisted semen analysis. In addition, biochemistry markers such as gamma-glutamyltranspeptidase, alpha-glucosidase and fructose in 50 liquefied and 39 non-liquefied samples, untreated or treated with chymotrypsin, were determined.

RESULTS

Treatment with chymotrypsin had no effect on sperm concentration, motility, motility a and b, straightness, curvilinear velocity, straight line velocity, average path velocity and beat cross frequency in both liquefied and non-liquefied semen. However, linearity (p=0.025) decreased and the amplitude of the lateral head (p=0.029) increased significantly in non-liquefied semen after treatment with chymotrypsin. The levels of gamma-glutamyltranspeptidase, alpha-glucosidase and fructose in seminal plasma were unaffected by chymotrypsin, regardless of liquefaction status.

CONCLUSIONS

Chymotrypsin had no effects on the detection of sperm parameters and biochemistry markers, and could be used to treat non-liquefied samples before semen analysis in the andrology laboratory.

Advances in Prostate Cancer Immunotherapies

Prostate cancer is a major cause of mortality in men in the Western world. Although treatment of early stage prostate cancer with radiation therapy or prostatectomy is efficient in most cases, some patients develop a fatal hormone-refractory disease. Treatments in this case are limited to aggressive chemotherapies, which can reduce serum prostate-specific antigen (PSA) levels in some patients. Taxane- and platinum-compound-based chemotherapies produce a survival benefit of only a few months. Therefore, it is crucial to develop novel, well tolerated treatment strategies. Over the past years, immunotherapy of hormone-refractory prostate cancer has been studied in numerous clinical trials. The fact that the prostate is a non-essential organ makes prostate cancer an excellent target for immunotherapy. Administration of antibodies targeting the human epidermal growth factor receptor-2 or the prostate-specific membrane antigen led to stabilisation of PSA levels in several patients. Vaccination of prostate cancer patients with irradiated allogeneic prostate cell lines has demonstrated that whole cell-based vaccines can significantly attenuate increases in PSA. Two different recombinant viral expression vectors have been applied in prostate cancer treatment: poxvirus and adenovirus vectors. Both vaccines have the advantages of using a natural method to induce immune responses and achieving high levels of transgene expression. Vaccinia viruses in combination with recombinant fowlpox or canarypox virus have been used to express recombinant PSA. Several studies demonstrated that this approach is safe and can lead to stabilisation of PSA values. A very promising approach in prostate cancer immunotherapy is vaccination of patients with dendritic cells. Thereby, peptides, recombinant proteins, tumour lysates or messenger RNA have been used to deliver antigens to autologous dendritic cells. Loading of dendritic cells with up to five different peptides derived from multiple proteins expressed in prostate cancer demonstrated that cytotoxic T-cell responses could be elicited in prostate cancer patients. Sipuleucel-T (APC8015), an immunotherapy product consisting of antigen-presenting cells, loaded ex vivo with a recombinant fusion protein consisting of prostatic acid phosphatase linked to granulocyte-macrophage colony-stimulating factor, demonstrated in a phase III, placebo-controlled trial an improvement in median time to disease progression. The improvement in overall survival was 4.5 months for sipuleucel-T-treated patients compared with the placebo group. Although there is a minor increase in overall survival of metastatic prostate cancer patients with some approaches, more effective therapeutic strategies need to be developed.

Structure-guided design of peptidic ligand for human prostate specific antigen

Prostate specific antigen (PSA) is a member of kallikrein family having serine protease-like activity and acts as a prognostic marker of prostate carcinoma. Various studies have been performed on inhibition of PSA and such targeting requires the identification of highly selective peptide inhibitors. PSA was purified from human seminal plasma by rapid and efficient methods, and binding studies for various peptides were carried out by fluorescence spectroscopy and SPR. The 'S' of PSA is predominated by hydrophobic residues, and hence many hydrophobic peptides were used to determine their binding affinity to PSA by fluorescence spectroscopy. We observed that LLFW, FFKW, and KFW binds strongly to PSA, among them LLFW showed strong binding. SPR also showed strong binding affinity of PSA toward peptides with hydrophobic and basic residues. Among the peptides used, FWYS showed dramatic increase in binding affinity (10(-10) M). The peptides analyzed for binding studies, suggests that peptide with Trp residue along with basic or hydrophobic amino acids may be useful for designing specific inhibitors for PSA. The strong affinities of designed peptides for PSA can be a valuable tool for designing therapeutic agents for prostate carcinomas.

Oxytocin and the human prostate in health and disease

Oxytocin is a peptide hormone produced by the neurohypophysis. The discovery that the peptide is produced locally within the male and female reproductive tracts has raised the possibility that oxytocin may have paracrine and autocrine actions outside of the nervous system. Oxytocin and its receptor have been identified in the human prostate. The prostate is an androgen-dependent organ whose function is to secrete components of the seminal fluid. Oxytocin has been shown to modulate contractility of prostate tissue and also to regulate local concentrations of the biologically active androgens. Oxytocin has also been shown to regulate cell growth. Prostate disease is common and results from abnormal growth of the gland. Oxytocin concentrations are altered in both benign and malignant prostate diseases and in vitro studies suggest that the peptide may be involved in the pathophysiology of these diseases.

Quantitative analysis of hippostasin/KLK11 gene expression in cancerous and noncancerous prostatic tissues

OBJECTIVES

Hippostasin/kallikrein 11 (KLK11) is a member of the human kallikrein gene family, which includes prostate-specific antigen (PSA), human kallikrein 2 (hK2), and another 12 members, all localized on chromosome 19q13.4. Hippostasin has two alternative splicing isoforms, known as the brain type and prostate type. We have previously reported that the prostate-type isoform is not expressed in human prostate cancer cell lines.

METHODS

We compared the expression of hippostasin/KLK11 isoforms in 76 matched pairs of human normal and prostate cancer tissues by quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

The expression of both isoforms of KLK11 was 25% to 45% higher in cancer tissues compared with their normal counterparts. Regarding prostate-type KLK11, we identified a significant association between lower expression and higher tumor stage, Gleason score, and tumor grade. No such association was seen with the brain-type isoform.

CONCLUSIONS

: The expression of the prostate-type isoform of KLK11 is increased in prostate cancer. This parameter should be examined further as a new prognostic indicator of prostate cancer.

Quantitative analysis of macrophage inhibitory cytokine-1 (MIC-1) gene expression in human prostatic tissues

Macrophage inhibitory cytokine-1 (MIC-1) gene is a member of transforming growth factor-beta superfamily and was reported to be highly overexpressed in human prostate cancer using microarray technology. The aim of this study was to evaluate the quantitative expression of MIC-1 in malignant and benign prostate tissues and to associate expression levels with clinicopathological parameters of prostate cancer. Matched (paired) prostatic tissue samples from the cancerous and noncancerous parts of the same prostates were obtained from 66 patients who underwent radical prostatectomy. Quantitative RT-PCR was performed using SYBR Green I on the Roche LightCycler system. Macrophage inhibitory cytokine-1 gene overexpression in cancerous tissues was observed in 88% of cases, compared to noncancerous tissues (P<0.001). The expression level of MIC-1 in cancerous tissues was significantly higher than in noncancerous tissue (P<0.001). Higher expression of MIC-1 gene was significantly associated with higher Gleason score (P=0.004). The expression of the MIC-1 gene in prostate cancer is significantly higher than in noncancerous tissues, especially in more aggressive forms of the disease (Gleason score>5). This is in contrast to prostate-specific antigen that is downregulated in higher-grade tumours. The upregulation of MIC-1 in prostate cancer and in advanced and more aggressive prostatic tumours suggests that MIC-1 protein should be evaluated as a potential diagnostic and prognostic biomarker.

The human prostate cancer cell line LNCaP bears functional membrane testosterone receptors that increase PSA secretion and modify actin cytoskeleton

Recent findings have shown that, in addition to the genomic action of steroids, through intracellular receptors, short-time effects could be mediated through binding to membrane sites. In the present study of prostate cancer LNCaP cells, we report that dihydrotestosterone and the non-internalizable analog testosterone-BSA increase rapidly the release of prostate-specific antigen (PSA) in the culture medium. Membrane testosterone binding sites were identified through ligand binding on membrane preparations, flow cytometry, and confocal laser microscopy of the non-internalizable fluorescent analog testosterone-BSA-FITC, on whole cells. Binding on these sites is time- and concentration-dependent and specific for testosterone, presenting a KD of 10.9 nM and a number of 144 sites/mg protein (approximately 13000 sites/cell). Membrane sites differ immunologically for intracellular androgen receptors. The secretion of PSA after membrane testosterone receptor stimulation was inhibited after pretreatment with the actin cytoskeleton disrupting agent cytochalasin B. In addition, membrane testosterone binding modifies the intracellular dynamic equilibrium of monomeric to filamentous actin and remodels profoundly the actin cytoskeleton organization. These results are discussed in the context of a possible involvement of these sites in cancer chemotherapy.

Are serum hormones associated with the risk of prostate cancer? Prospective results from the Massachusetts Male Aging Study

OBJECTIVES

To determine whether prediagnostic serum hormones are predictive of prostate cancer risk in a sample of men 40 to 70 years old at baseline.

METHODS

Seventeen serum hormones, including androgens, estrogens, and adrenal and pituitary hormones, were measured at baseline (1987 to 1989) and used to predict incident prostate cancer by follow-up (1995 to 1997) using data from the Massachusetts Male Aging Study, a prospective, population-based random sample.

RESULTS

Seventy men (4%) of 1576 were diagnosed with prostate cancer between the baseline and follow-up periods (approximately 8 years). None of the hormones were associated with prostate cancer risk except for androstanediol glucuronide (AAG), which exhibited a nonlinear, inverse relationship with prostate cancer (P <0.003) when age, body mass index, alcohol use, dihydrotestosterone, and total prostate-specific antigen were controlled for. Men in the second, third, and fourth quartiles of AAG relative to the first were less likely to be diagnosed with prostate cancer, although only the comparison of the second versus the first achieved statistical significance (odds ratio 0.2, 99% confidence interval 0.04 to 0.6). No dose-response relationships were observed.

CONCLUSIONS

The lack of association with most hormones and the nonlinear association with AAG calls into question whether serum hormones collected during midlife are risk factors for prostate cancer.

Cloning and characterization of the alpha 1-antichymotrypsin produced by human prostate tissue

BACKGROUND

alpha 1-antichymotrypsin (ACT) forms stable complexes with prostate-specific antigen (PSA), a serine protease, and this complex is the major form of PSA in the blood circulation. alpha 1-antichymotrypsin occurs in the blood in approximately 10(5) molar excess to PSA, mainly due to hepatic production, but local prostatic production of ACT has been demonstrated by immunohistochemistry and in situ hybridization. The present study was performed to further characterize this prostate-produced ACT.

METHODS

The nucleotide structure of the prostatic transcript was determined from ACT coding clones isolated from prostatic cDNA. The occurrence of a prostatic ACT transcript was analyzed by Northern blot. RT-PCR was used to detect ACT transcripts in cultured prostatic cancer cells.

RESULTS

Screening of two prostatic cDNA libraries showed the frequency of ACT transcripts to be about 1 clone in 40,000. The cDNA sequence of prostatic ACT is identical to that of the previously published hepatic ACT. Northern blot analysis of mRNA extracted from prostatic tissue showed a single transcript of approximately 1.5 kb. RT-PCR analysis demonstrated an ACT transcript in cultured prostatic cancer cells.

CONCLUSIONS

In this study we provide further evidence for a local, prostatic production of ACT. The cDNA sequence data suggest that the peptide backbone of prostatic ACT is identical to the protein derived from the liver, and thus may be functional as a protease inhibitor.

E4, a new monoclonal antibody identifying a human prostatic cell surface antigen

The monoclonal antibody E4 (IgG2a, kappa) was raised by immunizing mice with dispersed cells obtained from human benign prostatic hyperplasia (BPH). The antibody identifies an antigen abundantly expressed in normal prostate epithelial cells, in benign epithelial prostatic cells and in well- and moderately well differentiated adenocarcinomas of the prostate, whereas poorly differentiated prostatic adenocarcinomas display somewhat less expression. Investigation of the human prostatic adenocarcinoma cell line DU 145 revealed E4 immunoreactivity localized to the cell surface. SDS-PAGE analysis under reducing conditions demonstrated an approximate molecular weight of 70,000 for the antigen. The highly specific reactivity with prostate tissue, as well as intense surface staining, especially in well- and moderately well differentiated prostatic adenocarcinomas, makes the E4 antibody a useful immunohistochemical marker and a possible candidate for future immunoscintigraphy and/or targeted radiotherapy.

Alteration of the hormonal bioactivity of parathyroid hormone-related protein (PTHrP) as a result of limited proteolysis by prostate-specific antigen

OBJECTIVES

To discover whether the proteolytic activity of prostate-specific antigen (PSA) affects the structure and function of parathyroid hormone-related protein (PTHrP), as both are abundant components of human seminal plasma.

METHODS

The ability of PTHrP to act as a substrate was studied by incubating a synthetic polypeptide, consisting of 34 amino acid residues of the amino-terminal domain of PTHrP, with purified PSA. The incubate was then analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, high-pressure liquid chromatography separation, amino-terminal peptide sequencing, and mass spectrometry. The physiologic effect of the proteolytic activity of PSA on PTHrP was studied by measuring any alteration in PTHrP (1-34)-induced elevation of cyclic adenosine monophosphate (cAMP) production by UMR-106 rat osteosarcoma cells in culture. All cell culture experiments were performed with PSA and PTHrP (1-34) at physiologic concentrations. RESULTS. Our data show that PSA proteolytically cleaves PTHrP (1-34) after either residue 22 or 23, generating three peptide fragments. Both cleavages occur carboxy terminally of a phenylalanine residue. The cAMP production in rat osteosarcoma cells, induced by the amino-terminal portion of PTHrP (1-34), as a result of its structural similarity with parathyroid hormone (PTH), was abated by PSA in a dose- and time-dependent fashion. In contrast, heat-inactivated PSA had no effect on cAMP production.

CONCLUSIONS

Our study demonstrates that PTHrP is a substrate for PSA. The cleavage of the amino-terminal portion of PTHrP completely disrupts its ability to interact with the PTH/PTHrP receptor and thus inhibits its PTH-like activity. The proteolytic processing of PTHrP by PSA may play an important role in the post-translational/post-secretional regulation of prostatic PTHrP activities, which are believed to include regulation of prostate growth and differentiation.

The effect of exogenous testosterone on total and free prostate specific antigen levels in healthy young men

PURPOSE

We evaluated the effect of exogenous testosterone administration on serum total and free prostate specific antigen (PSA) in healthy young men.

MATERIALS AND METHODS

Nine volunteers received either 100, 250 or 500 mg. testosterone by intramuscular injection each week for 15 weeks. Blood was drawn every other week for 28 weeks and at week 40. Serum total and free PSA, and total and free testosterone were measured and compared to baseline values.

RESULTS

Significant elevations in total and free testosterone occurred but no significant change in serum total and free PSA was detected.

CONCLUSIONS

Serum PSA is not responsive to elevated serum testosterone levels in healthy young men. PSA metabolism in the normal prostate is unclear but our findings may have implications for differentiation of pathological conditions of the human prostate.

Acid phosphatase: defining a role in androgen-independent prostate cancer

OBJECTIVES

In multivariable analysis, post-therapy change in prostate-specific antigen (PSA) was shown to be the most significant factor predictive of survival in patients with androgen-independent prostate cancer. To refine the model, we studied the patterns of change in acid phosphatase, alkaline phosphatase, and lactate dehydrogenase after treatment.

METHODS

One hundred seven patients with androgen-independent prostate cancer treated on seven different protocols in Memorial Sloan-Kettering Cancer Center were evaluated. For tumor-specific (acid phosphatase and PSA) and nontumor-specific (alkaline phosphatase and lactate dehydrogenase) enzymes, a minimum 50% or 80% decrease from baseline documented on three separate occasions a minimum of 6 weeks apart was required to categorize a patient as having a decline.

RESULTS

Nineteen patients (18%) had either a 50% decline in acid phosphatase or PSA, of whom 13 (68%) had a decline of both markers. Six (32%) patients showed discordance between the two parameters. Declines in PSA level typically preceded declines in acid phosphatase levels. The median survival of patients showing declines in both markers exceeded that of patients showing declines in PSA alone by 1 year. Although baseline measurements of alkaline phosphatase or lactate dehydrogenase did add additional prognostic information, post-therapy changes did not.

CONCLUSIONS

Post-therapy declines in PSA and acid phosphatase represent reproducible endpoints for clinical trials in androgen-independent disease. The requirement of a repeated and parallel decline in both markers may improve the results observed by monitoring declines in PSA alone. Monitoring the two parameters may allow the development of models that can be used as surrogate endpoints for response and survival in a disease in which reproducible measurements of response are lacking.

A recombinant vaccinia virus expressing human prostate-specific antigen (PSA): safety and immunogenicity in a non-human primate

Prostate-specific antigen (PSA) is a serine protease secreted by prostatic epithelial cells and is widely used as a marker for prostate cancer. The tissue specificity of PSA makes it a potential target for active specific immunotherapy, especially in prostate cancer patients who have undergone prostatectomy and in whom the only PSA-expressing tissue in the body resides in metastatic deposits. We report here the cloning, construction and immunological consequences of immunization of rhesus monkeys with a recombinant vaccinia virus expressing human PSA (designated rV-PSA). The prostate gland of the rhesus is structurally and functionally similar to the human prostate. While rodent and other mammalian species do not share homology with human PSA, there is 94% homology between the amino acid sequences of rhesus and human PSA. Immunization of rhesus monkeys with wild-type vaccinia virus or rV-PSA elicited the usual low-grade constitutional symptoms of vaccinia virus infection. There was no evidence of any adverse effects in any immunized monkeys. A short-lived PSA-specific IgM antibody response was noted in all rV-PSA immunized monkeys regardless of dose level. All monkeys receiving the 10(8)pfu dose of rV-PSA demonstrated PSA-specific T-cell responses that were maintained up to 270 days. No differences in anti-PSA immune responses or toxicity were observed in animals that received prostatectomy prior to immunization. Our results thus demonstrate the safety and immunogenicity of rV-PSA in a non-human primate and have implications for potential specific immunotherapy protocols using PSA as a target.

Generation, purification, and characterization of a recombinant source of human prostate-specific antigen

Human prostate-specific antigen (PSA), a 33- to 34-kDa serine proteinase with extensive homology to glandular kallikrein, is a single-chain glycoprotein that contains 7% carbohydrate. The presence of PSA in the serum of patients with prostatic cancer is widely employed as a marker of disease status. PSA has also been thought of as a possible target for use in active specific immunotherapy protocols. To date, the source of PSA employed has been seminal fluid from different individuals; this has raised concerns about differences among PSA batches for standardization of assays. This report is the first description of the production and the purification of a recombinant source of PSA using a baculovirus expression system. A baculovirus recombinant of the cDNA encoding the full length PSA was expressed in insect cells yielding two major immunoreactive products of 31 and 29 kDa. The latter size conforms to the molecular weight of a core preprotein deduced from the sequence of the cDNA insert. The larger protein represents the N-linked glycosylated form of the preprotein. Western blot analysis showed that both the glycosylated and aglycosylated forms of PSA reacted with a polyclonal and two different monoclonal antibodies specific for PSA. bV-PSA, like commercially available PSA, showed also low-molecular-weight immunoreactive products when culture supernatants were concentrated or taken through steps of purification. bV-PSA was purified to a final product consisting of a major 29-kDa protein and a minor 31-kDa protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostate-specific antigen and human glandular kallikrein: two kallikreins of the human prostate

Prostate-specific antigen (PSA) is a 33 kD protein synthesized in the epithelial cells of the prostate gland. It is a serine protease that belongs to the subgroup of kallikreins, among which it is very similar to a putative enzyme called human glandular kallikrein (hGK-1). Although the hGK-1 enzyme remains to be characterized in vivo, the hGK-1 gene is expressed in the same prostatic epithelial cells as the PSA gene. Expression of the PSA gene is under complex control and the steady-state level of PSA mRNA is increased by androgens, and decreased by epidermal growth factor and activation of protein kinase C. This suggests the existence of several regulatory elements within the cis-acting control elements of the PSA gene. As a seminal serine protease, PSA has been shown to digest the high molecular weight seminal vesicle protein, seminogelin. However, it is likely that this does not constitute the only natural substrate of PSA, as PSA has been shown to degrade insulin-like growth factor-binding protein-3. Serum PSA concentrations are frequently increased in patients with prostatic cancer, but this is also the case in patients with benign prostatic hyperplasia. Thus, PSA measurements alone are not useful as a screening tool for undiagnosed prostatic cancer. However, serum PSA concentrations can be successfully used together with other methods in diagnosing prostatic diseases and in monitoring the successfulness of treatments for prostatic cancer.

Tissue-type plasminogen activator level is decreased in human seminal plasma with abnormal liquefaction

OBJECTIVE

To determine plasminogen activators (PAs) and PA inhibitor levels in seminal plasma of patients attending an infertility clinic.

DESIGN

Quantification by immunologic method of PAs in seminal plasma.

SETTING

Patients of Department of Urology and Andrology, University Hospital, Nimes, France.

PATIENTS

Ninety-two men attending for assessment because of infertility.

INTERVENTIONS

Semen were collected by masturbation. Usual sperm parameters were determined; immediately after liquefaction, samples were snap-frozen at -85 degrees C until used for immunologic determination.

MAIN OUTCOME MEASURES

Tissue-type PA antigen, urokinase-type PA antigen, and type 1 PA inhibitor antigen levels in seminal plasma.

RESULTS

Median values of PA were 270 ng/mL (tissue-type PA) and 5.4 ng/mL (urokinase-type PA) in normozoospermia; 290 ng/mL (tissue-type PA) and 5.7 ng/mL (urokinase-type PA) in oligozoospermia; 325 ng/mL (tissue-type PA) and 3.5 ng/mL (urokinase-type PA) in oligoasthenozoospermia. Type 1 PA inhibitor antigen levels were often under detection limit. Tissue-type PA was 173.5 ng/mL in semen with abnormal liquefaction and 290 ng/mL in semen with normal liquefaction.

CONCLUSION

The study confirmed the presence of both types of PAs in seminal plasma, tissue-type PA being largely predominant. No difference was found in tissue-type PA, urokinase-type PA, or type 1 PA inhibitor antigen levels between normal and oligozoospermic semen nor between normal and asthenozoospermic semen. On the other hand, semen with abnormal liquefaction had significantly lower tissue-type PA level than normal semen.

Prostate volume in testosterone-treated and untreated hypogonadal men in comparison to age-matched normal controls

OBJECTIVE

The potential use of testosterone preparations for substitution therapy for ageing men and for male contraception, in addition to the well established substitution therapy of male hypogonadism, make increased testosterone use likely. However, little clinical information is available on the effect of testosterone therapy on the prostate in hypogonadal men.

DESIGN AND MEASUREMENTS

In a controlled cross-sectional study, prostate volume measured by transrectal ultrasonography, serum levels of prostate-specific antigen (PSA) and sex hormones, and uroflow parameters were determined.

PATIENTS

Three groups of age-matched men were enrolled in the study: 47 newly diagnosed hypogonadal men before testosterone treatment, 78 hypogonadal men with at least 6 months of effective testosterone therapy and 75 normal men.

RESULTS

Regression analysis revealed a significant positive correlation of prostate volume with age in normal men and testosterone-treated hypogonadal men, whereas no significant correlation was detected in untreated hypogonadal men. Prostate volume was significantly lower in untreated hypogonadal men (12.2 (11.0-13.5) ml) (mean (95% confidence limits)) compared to both other groups. However, no significant difference in prostate volume was detected between testosterone-treated hypogonadal men (21.3 (19.9-22.8) ml) and normal men (22.9 (21.4-24.4) ml). Similar results were obtained for PSA with comparable values in the testosterone-treated hypogonadal men (0.98 (0.88-1.10) micrograms/l) and normal men (1.02(0.91-1.14) micrograms/l), and significantly lower concentrations in the untreated hypogonadal men (0.64 (0.55-0.73) micrograms/l). No differences in uroflow parameters were detected between the three study groups.

CONCLUSIONS

Effective testosterone treatment of hypogonadal men results in prostate volume and prostate-specific antigen levels comparable to age-matched normal men. Therefore, testosterone-induced prostate growth should not preclude hypogonadal men from testosterone substitution therapy.

Prostatic specific antigen

PSA is a 34-kDa 240-amino-acid glycoprotein produced exclusively by prostatic epithelial cells. PSA is a serine protease, is a member of the kallikrein gene family, and has a high sequence homology with human glandular kallikrein. It has chymotrypsin-, trypsin-, and esterase-like activities. In the serum it is present mainly in a complex form with alpha 1-antichymotrypsin. It is secreted in the seminal plasma and is responsible for liquefaction of the seminal coagulum. The production of PSA proteins appears to be under the control of circulating androgens acting through the androgen receptors. The PSA gene is up-regulated predominantly by androgens at both the protein and mRNA levels. DRE causes minimal changes in the PSA level, while prostate massage, ultrasonography, systoscopic examination, and prostate biopsy can all cause clinically significant elevations. Other conditions, such as prostatitis, prostate intraepithelial neoplasia, acute urinary retention, and renal failure can also elevate the PSA level. The value of PSA as a screening tool is questionable because of the great deal of overlap in PSA levels between BPH and prostate cancer. However, if used in men over 50, in conjunction with DRE and/or ultrasonography, it may become a vital part of the early detection program. PSA's role in determining the clinical and pathological stage is also limited, in spite of the direct correlation between the pathological stage and the PSA level, because of great overlap in the PSA levels in various stages. The most important clinical utility of PSA is in monitoring patients after definitive therapy. PSA is most sensitive and reliable in the detection of a residual tumor, possibly recurrence, or disease progression following treatment, irrespective of the treatment modality. PSA can accurately predict the tumor status and can detect recurrence several months before its detection by any other method. PSA is also a very sensitive and specific immunohistochemical marker for tumors of prostatic origin. Compared to PAP, PSA is a more precise and meaningful marker in all clinical situations. With the development of ultrasensitive assays and the adoption of an international standard PSA calibrator, so that results from multicenter studies can be compared, PSA could become one of the most useful tumor marker in cancer biology.

Photobiological properties of hematoporphyrin diesters: evaluation for possible application in photochemotherapy of cancer

The dimethyl, diethyl, dipropyl, dibutyl, diamyl, dihexyl and diheptyl esters of hematoporphyrin (Hp) were synthesized and shown to be more strongly retained on a reverse phase (C18) high performance liquid chromatography column than most components of Photofrin II (PII) - the sensitizer used for photochemical treatment of cancer in the clinic. The Hp diesters were found to be less efficient than PII in sensitizing cells to photoinactivation. This was partly due to de-esterification of the Hp diesters by esterase activity in the serum. The de-esterification of the Hp diesters was highly dependent on the ester group, with Hp dimethyl ester (t1/2 for conversion to Hp monomethyl ester was 6 min) being de-esterified with a rate 500 times faster than that for Hp diheptyl ester. Incubation of NHIK 3025 cells with these dyes showed that the Hp diesters were all partly located in extranuclear spots and partly diffusely distributed in the cytoplasm. The fluorescing spots may be due to lysosomally located Hp diesters, since the lysosomal marker enzyme beta-Nacetyl-D-glucosaminidase was partly inactivated by Hp diesters and light.

The potential use of prostatic secretory protein of 94 amino acid residues (PSP94) as a serum marker for prostatic tumor

The serum concentrations of prostatic secretory protein of 94 amino acid residues (PSP94) as well as those of prostate-specific antigen (PSA) were determined in 40 patients with established prostatic carcinoma, prior to transurethral resection of the prostate. In a comparison with a control group of healthy men (n = 40) and a group of patients with histologically established benign prostatic hyperplasia (n = 40) no significant differences in PSP94 serum concentrations between the groups were observed. Similarly, correlations of PSP94 serum concentrations with prostatic carcinoma stages or grades were not detected. In contrast, and as expected, PSA behaved as a prostate tumor marker of known sensitivity and specificity. A correlation of PSP94 and PSA concentrations in sera of patients with benign prostatic hyperplasia and/or prostatic carcinoma could not be verified. PSP94 apparently does not fulfill the criteria of a serum marker for monitoring adenomas and/or carcinomas of the prostate.