Recombinant prostate specific antigen inhibits angiogenesis in vitro and in vivo

Kallikrein-related peptidases: mechanistic understanding for potential therapeutic targeting in cancer

INTRODUCTION

Human kallikrein-related peptidases (KLKs) represent a subgroup of 15 serine endopeptidases involved in various physiological processes and pathologies, including cancer.

AREAS COVERED

This review aims to provide a comprehensive overview of the KLK family, highlighting their genomic structure, expression profiles and substrate specificity. We explore the role of KLKs in tumorigenesis, emphasizing their potential as biomarkers and therapeutic targets in cancer treatment. The dysregulated activity of KLKs has been linked to various malignancies, making them promising candidates for cancer diagnostics and therapy.

EXPERT OPINION

: Recent advancements in understanding the mechanistic pathways of KLK-related tumorigenesis offer new prospects for developing targeted cancer treatments. Expert opinion suggests that while significant progress has been made, further research is necessary to fully exploit KLKs' potential in clinical applications.

Remodelling of the tumour microenvironment by the kallikrein-related peptidases

Kallikrein-related peptidases (KLKs) are critical regulators of the tumour microenvironment. KLKs are proteolytic enzymes regulating multiple functions of bioactive molecules including hormones and growth factors, membrane receptors and the extracellular matrix architecture involved in cancer progression and metastasis. Perturbations of the proteolytic cascade generated by these peptidases, and their downstream signalling actions, underlie tumour emergence or blockade of tumour growth. Recent studies have also revealed their role in tumour immune suppression and resistance to cancer therapy. Here, we present an overview of the complex biology of the KLK family and its context-dependent nature in cancer, and discuss the different therapeutic strategies available to potentially target these proteases.

KLK3 in the Regulation of Angiogenesis-Tumorigenic or Not?

In this focused review, we address the role of the kallikrein-related peptidase 3 (KLK3), also known as prostate-specific antigen (PSA), in the regulation of angiogenesis. Early studies suggest that KLK3 is able to inhibit angiogenic processes, which is most likely dependent on its proteolytic activity. However, more recent evidence suggests that KLK3 may also have an opposite role, mediated by the ability of KLK3 to activate the (lymph)angiogenic vascular endothelial growth factors VEGF-C and VEGF-D, further discussed in the review.

Role of extracellular vesicles from adipose tissue- and bone marrow-mesenchymal stromal cells in endothelial proliferation and chondrogenesis

The secretome of mesenchymal stromal cells (MSCs) derived from different tissue sources is considered an innovative therapeutic tool for regenerative medicine. Although adipose tissue‐and bone marrow‐derived MSCs (ADSCs and BMSCs, respectively) share many biological features, the different tissue origins can be mirrored by variations in their secretory profile, and in particular in the secreted extracellular vesicles (EVs). In this study, we carried out a detailed and comparative characterization of middle‐ and small‐sized EVs (mEVs and sEVs, respectively) released by either ADSCs or BMSCs. Their involvement in an endochondral ossification setting was investigated using ex vivo metatarsal culture models that allowed to explore both blood vessel sprouting and bone growth plate dynamics. Although EVs separated from both cell sources presented similar characteristics in terms of size, concentration, and marker expression, they exhibited different characteristics in terms of protein content and functional effects. ADSC‐EVs overexpressed pro‐angiogenic factors in comparison to the BMSC‐counterpart, and, consequently, they were able to induce a significant increase in endothelial cord outgrowth. On the other hand, BMSC‐EVs contained a higher amount of pro‐differentiation and chemotactic proteins, and they were able to prompt growth plate organization. The present study highlights the importance of selecting the appropriate cell source of EVs for targeted therapeutic applications.

KLK3 SNP-SNP interactions for prediction of prostate cancer aggressiveness

Risk classification for prostate cancer (PCa) aggressiveness and underlying mechanisms remain inadequate. Interactions between single nucleotide polymorphisms (SNPs) may provide a solution to fill these gaps. To identify SNP-SNP interactions in the four pathways (the angiogenesis-, mitochondria-, miRNA-, and androgen metabolism-related pathways) associated with PCa aggressiveness, we tested 8587 SNPs for 20,729 cases from the PCa consortium. We identified 3 KLK3 SNPs, and 1083 (P < 3.5 × 10-9) and 3145 (P < 1 × 10-5) SNP-SNP interaction pairs significantly associated with PCa aggressiveness. These SNP pairs associated with PCa aggressiveness were more significant than each of their constituent SNP individual effects. The majority (98.6%) of the 3145 pairs involved KLK3. The 3 most common gene-gene interactions were KLK3-COL4A1:COL4A2, KLK3-CDH13, and KLK3-TGFBR3. Predictions from the SNP interaction-based polygenic risk score based on 24 SNP pairs are promising. The prevalence of PCa aggressiveness was 49.8%, 21.9%, and 7.0% for the PCa cases from our cohort with the top 1%, middle 50%, and bottom 1% risk profiles. Potential biological functions of the identified KLK3 SNP-SNP interactions were supported by gene expression and protein-protein interaction results. Our findings suggest KLK3 SNP interactions may play an important role in PCa aggressiveness.

Efficacy and safety of Afalaza in men with symptomatic benign prostatic hyperplasia at risk of progression: a multicenter, double-blind, placebo-controlled, randomized clinical trial

Introduction

In order to investigate the efficacy and safety of Afalaza in men with benign prostatic hyperplasia (BPH) at risk of progression, this multicenter, double-blind, placebo-controlled, randomized clinical trial was performed. Derived by technological treatment of antibodies to prostate-specific antigen (PSA) and endothelial nitric oxide synthase (eNOs), Afalaza was previously proved to modulate its molecular targets. The mechanism of action of the drug is associated with the modulating effect of the antibiodies (RA-Abs) on the molecular targets (PSA and eNOS) by way of conformational changes.

Material and methods

A total of 249 patients aged 45–60 years with BPH and moderate lower urinary tract symptoms (LUTS), total prostate volume (TPV) ≥30 cm³, Qmax 10–15 ml/s, and serum PSA<4 ng/ml were randomly assigned to receive either Afalaza (n = 125) or placebo (n = 124) for 12 months. Changes in BPH/LUTS symptoms (according to the International Prostate Symptom Score), Qmax, TPV, PSA, BPH clinical progression, occurrence of acure urinary retention (AUR) events or BPH-related surgery were estimated as the study endpoints.

Results

IPSS mean change was -3.7 ±3.0 (95% CI -4.3 to -3.2) after 12 months of Afalaza (vs. -2.9 ±2.4; 95% CI -3.3 to -2.4 in placebo; р = 0.02). Qmax growth was 2.5 ±4.3 ml/s (vs. 1.4 ±3.3 in placebo; p = 0.049), TPV reduced by 11.8 ±16.0% (vs. 6.5 ±14.7%; p = 0.01, and PSA remained unchanged. Afalaza therapy resulted in a significant decrease in the total sum of BPH progression symptoms (p = 0.01). The maximum effect of Afalaza was registered after 12 months without a tendency to form a ‘plateau’. During the study, no patients experienced AUR or BPH-related surgery.

Conclusions

A 12-month course of Afalaza therapy is effective and safe for patients with BPH. The results of end points measurements revealed asignificant advantage of Afalaza compared to placebo in the overall symptoms benefit and a decline in the risk of BPH progression.

ClinicalTrials.gov: NCT01716104.

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.

TRPM8 inhibits endothelial cell migration via a non-channel function by trapping the small GTPase Rap1

Endothelial cell adhesion and migration are critical steps of the angiogenic process, whose dysfunction is associated with tumor growth and metastasis. The TRPM8 channel has recently been proposed to play a protective role in prostate cancer by impairing cell motility. However, the mechanisms by which it could influence vascular behavior are unknown. Here, we reveal a novel non-channel function for TRPM8 that unexpectedly acts as a Rap1 GTPase inhibitor, thereby inhibiting endothelial cell motility, independently of pore function. TRPM8 retains Rap1 intracellularly through direct protein-protein interaction, thus preventing its cytoplasm-plasma membrane trafficking. In turn, this mechanism impairs the activation of a major inside-out signaling pathway that triggers the conformational activation of integrin and, consequently, cell adhesion, migration, in vitro endothelial tube formation, and spheroid sprouting. Our results bring to light a novel, pore-independent molecular mechanism by which endogenous TRPM8 expression inhibits Rap1 GTPase and thus plays a critical role in the behavior of vascular endothelial cells by inhibiting migration.

Overexpression and purification of folded domain of prostate cancer related proteins MSMB and PSA

Overexpression of domains of a human protein using recombinant DNA technology has been challenging because individual domains intend to accumulate as non-soluble aggregate when expressed separately. Studies on identifying right sequences for a domain to be able to fold independently may help understand the folding pattern and underlying protein-engineering events to isolate the functional domains of a protein. In this report, individual domains of prostate cancer related biomarkers; MSMB and PSA were overexpressed in bacterial system and purified in their folded forms using affinity chromatography. The western blotting experiment using domain specific antibodies further confirmed these proteins. The designed nucleotide sequences domains were truncated using fold index software and folding were predicted by phyre2 and I-TASSER software. Other parameters were optimized for their overexpression and purification using Co-NTA affinity chromatography. Purified domains of each protein showed secondary structures such as α + β type for PSA, α/β and β type for the each domains of PSA and MSMB respectively. This is the first report on producing PSA and MSMB individual domains in functional folded forms. This study may help produce the folded domain of many such proteins to be used for better diagnostic purpose.

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.

Biomarker development, from bench to bedside

This review describes studies performed by our group and other laboratories in the field aimed at development of biomarkers not only for cancer but also for other diseases. The markers covered include tumor-associated trypsin inhibitor (TATI), tumor-associated trypsin (TAT), human chorionic gonadotropin (hCG), prostate-specific antigen (PSA) and their various molecular forms, their biology and diagnostic use. The discovery of TATI was the result of a hypothesis-driven project aimed at finding new biomarkers for ovarian cancer among urinary peptides. TATI has since proved to be a useful prognostic marker for several cancers. Recently, it has been named Serine Peptidase Inhibitor Kazal Type 1 (SPINK1) after being rediscovered by several groups as a tumor-associated peptide by gene expression profiling and proteomic techniques and shown to promote tumor development by stimulating the EGF receptor. To explain why a trypsin inhibitor is strongly expressed in some cancers, research focused on the protease that it inhibited led to the finding of tumor-associated trypsin (TAT). Elevated serum concentrations of TAT-2 were found in some cancer types, but fairly high background levels of pancreatic trypsinogen-2 limited the use of TAT-2 for cancer diagnostics. However, trypsinogen-2 and its complex with α1-protease inhibitor proved to be very sensitive and specific markers for pancreatitis. Studies on hCG were initiated by the need to develop more rapid and sensitive pregnancy tests. These studies showed that serum from men and non-pregnant women contains measurable concentrations of hCG derived from the pituitary. Subsequent development of assays for the subunits of hCG showed that the β subunit of hCG (hCGβ) is expressed at low concentrations by most cancers and that it is a strong prognostic marker. These studies led to the formation of a working group for standardization of hCG determinations and the development of new reference reagents for several molecular forms of hCG. The preparation of intact hCG has been adopted as the fifth international standard by WHO. Availability of several well-defined forms of hCG made it possible to characterize the epitopes of nearly 100 monoclonal antibodies. This will facilitate design of immunoassays with pre-defined specificity. Finally, the discovery of different forms of immunoreactive PSA in serum from a prostate cancer patient led to identification of the complex between PSA and α1-antichymotrypsin, and the use of assays for free and total PSA in serum for improved diagnosis of prostate cancer. Epitope mapping of PSA antibodies and establishment of PSA standards has facilitated establishment well-standardized assays for the various forms of PSA.

Kallikrein-related peptidases targeted therapies in prostate cancer: perspectives and challenges

INTRODUCTION

Despite the emergence of several new effective treatments for metastatic castration-resistant prostate cancer patients, disease progression inevitably occurs, leading scientific community to carefully look for novel therapeutic targets of prostate cancer. Kallikrein (KLK)-related peptidases have been demonstrated to facilitate prostate tumorigenesis and disease progression through the development of an oncogenic microenvironment for prostate cells.

AREAS COVERED

This review first summarizes the large amount of preclinical data showing the involvement of KLKs in prostate cancer pathobiology. In the second part, the authors assess the current status and future directions for KLK-targeted therapy and briefly describe the advances and challenges implicated in the design of effective manufactured drugs. The authors then focus on the preclinical data and on Phase I/II studies of the most promising KLK-targeted agents in prostate cancer. The drugs discussed here are divided on the basis of their mechanism of action: KLK-engineered inhibitors; KLK-activated pro-drugs; KLK-targeted microRNAs and small interfering RNAs(-/)small hairpin RNAs; KLK vaccines and antibodies.

EXPERT OPINION

Targeting KLK expression and/or activity could be a promising direction in prostate cancer treatment. Future human clinical trials will help us to evaluate the real benefits, toxicities and the consequent optimal use of KLK-targeted drugs, as mono-therapy or in combination regimens.

A Large-Scale Analysis of Genetic Variants within Putative miRNA Binding Sites in Prostate Cancer

Prostate cancer is the second most common malignancy among men worldwide. Genome-wide association studies have identified 100 risk variants for prostate cancer, which can explain approximately 33% of the familial risk of the disease. We hypothesized that a comprehensive analysis of genetic variations found within the 3' untranslated region of genes predicted to affect miRNA binding (miRSNP) can identify additional prostate cancer risk variants. We investigated the association between 2,169 miRSNPs and prostate cancer risk in a large-scale analysis of 22,301 cases and 22,320 controls of European ancestry from 23 participating studies. Twenty-two miRSNPs were associated (P<2.3×10(-5)) with risk of prostate cancer, 10 of which were within 7 genes previously not mapped by GWAS studies. Further, using miRNA mimics and reporter gene assays, we showed that miR-3162-5p has specific affinity for the KLK3 rs1058205 miRSNP T-allele, whereas miR-370 has greater affinity for the VAMP8 rs1010 miRSNP A-allele, validating their functional role.

SIGNIFICANCE

Findings from this large association study suggest that a focus on miRSNPs, including functional evaluation, can identify candidate risk loci below currently accepted statistical levels of genome-wide significance. Studies of miRNAs and their interactions with SNPs could provide further insights into the mechanisms of prostate cancer risk.

Proteolytic activity of prostate-specific antigen (PSA) towards protein substrates and effect of peptides stimulating PSA activity

Prostate-specific antigen (PSA or kallikrein-related peptidase-3, KLK3) exerts chymotrypsin-like proteolytic activity. The main biological function of PSA is the liquefaction of the clot formed after ejaculation by cleavage of semenogelins I and II in seminal fluid. PSA also cleaves several other substrates, which may explain its putative functions in prostate cancer and its antiangiogenic activity. We compared the proteolytic efficiency of PSA towards several protein and peptide substrates and studied the effect of peptides stimulating the activity of PSA with these substrates. An endothelial cell tube formation model was used to analyze the effect of PSA-degraded protein fragments on angiogenesis. We showed that PSA degrades semenogelins I and II much more efficiently than other previously identified protein substrates, e.g., fibronectin, galectin-3 and IGFBP-3. We identified nidogen-1 as a new substrate for PSA. Peptides B2 and C4 that stimulate the activity of PSA towards small peptide substrates also enhanced the proteolytic activity of PSA towards protein substrates. Nidogen-1, galectin-3 or their fragments produced by PSA did not have any effect on endothelial cell tube formation. Although PSA cleaves several other protein substrates, in addition to semenogelins, the physiological importance of this activity remains speculative. The PSA levels in prostate are very high, but several other highly active proteases, such as hK2 and trypsin, are also expressed in the prostate and may cleave protein substrates that are weakly cleaved by PSA.

Correlation between KLK6 expression and the clinicopathological features of glioma

Aim of the study

We measured the impact of changing KLK6 expression levels on the pathological grade of gliomas and on proliferation rate, cell cycle progression, and apoptosis in the U251 glioblastoma cell line.

Material and methods

The expression of KLK6 in 35 brain glioma tissues and adjacent noncancerous tissues was measured using real-time quantitative polymerase chain reaction (PCR) and the relationship between KLK6 expression and pathological grades was analysed.

Results

The KLK6 expression in U251 cells was silenced by a specific siRNA, and the effects on proliferation, the cell cycle, and apoptosis were compared to wild type cells. Expression of KLK6 was downregulated in gliomas relative to matched noncancerous tissue. There was no obvious relationship between patient sex, pathological grade, or tumour classification and the expression of KLK6. In the U251 cell line, cell proliferation was enhanced and the fractions of cells in the G2 and S phases were increased by siRNA-mediated KLK6 silencing.

Conclusions

Expression of KLK6 inhibits tumour growth. Decreased KLK6 expression may be a possible risk factor for glioma.

Reconnoitring the status of prostate specific antigen and its role in women

Prostate specific antigen is considered to be a tumour marker having maximum utility and specificity for prostate cancer since decades. After the discovery of methods to quantify different molecular fractions of prostate specific antigen (PSA), its usefulness in diagnosing early prostate cancer cases has increased tremendously. The "specificity" of PSA, is now challenged by many studies which proved that PSA, once believed to be secreted exclusively by prostatic epithelium, is also present in females. The exact biological role of extraprostatic PSA is still debatable though many theories substantiated by in vitro evidence has been put forward. With the advent of ultrasensitive analytical techniques, PSA is now quantifiable in female serum in its various molecular forms and this has led to many assumptions of it being useful as a marker in female breast cancers. In a similar scenario to prostate cancer, the ratio of free to total PSA is shown to be useful in detecting early breast cancer cases. It is also shown to be a good prognostic indicator and a predictor of response to therapy and recurrence. Apart from its role in breast cancer, it has been advocated to be a marker of hyper androgenic states in women like hirsutism and polycystic ovarian syndrome. Conflicting reports regarding the role of extra prostatic PSA is accumulating but it has been proven beyond doubt that PSA is no longer specific and confined to prostate gland. Various studies have registered that PSA is an ubiquitous molecule, secreted by hormone responsive organs and its synthesis is stimulated by androgens and progesterone but not oestrogens. In this article, a review of various literatures is done about the presence of extra prostatic PSA, its probable role in those sites as well as its utility as a tumour marker in breast cancer.

PSMA/PSA ratio evaluated by immunohistochemistry may improve diagnosis of prostate cancer

Prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) measured in serum are not fully satisfactory as biomarkers of prostate cancer (PC). Results obtained in this article indicated that PSMA/PSA ratio evaluated by immunohistochemistry in normal prostate (NP), benign prostatic hyperplasia (BPH), and PC at the individual level could be a useful tool for diagnosis and prognosis of PC. PSMA and PSA were equally expressed in NP and the PSMA/PSA ratio was 1.22 ± 0.15. Data also indicated that PSMA/PSA ratio fluctuates in BPH and PC compared to NP. In BPH, the PSMA/PSA ratio was around 0.47 ± 0.02, whereas it's significantly increased in PC, about 4.95 ± 0.83. In parallel, the highest PSMA/PSA ratio was associated with high intratumoral angiogenesis in PC patients with (PSMA+,PSA+) profile.

Prostate-specific kallikrein-related peptidases and their relation to prostate cancer biology and detection. Established relevance and emerging roles

Kallikreins are a family of serine proteases with a range of tissue-specific and essential proteolytic functions. Among the best studied are the prostate tissue-specific KLK2 and KLK3 genes and their secreted protease products, human kallikrein 2, hk2, and prostate-specific antigen (PSA). Members of the so-called classic kallikreins, these highly active trypsin-like serine proteases play established roles in human reproduction. Both hK2 and PSA expression is regulated by the androgen receptor which has a fundamental role in prostate tissue development and progression of disease. This feature, combined with the ability to sensitively detect different forms of these proteins in blood and biopsies, result in a crucially important biomarker for the presence and recurrence of cancer. Emerging evidence has begun to suggest a role for these kallikreins in critical vascular events. This review discusses the established and developing biological roles of hK2 and PSA, as well as the historical and advanced use of their detection to accurately and non-invasively detect and guide treatment of prostatic disease.

Peptides binding to prostate-specific antigen enhance its antiangiogenic activity

BACKGROUND

Proteolytically active prostate-specific antigen (PSA or kallikrein-related peptidase 3, KLK3) has been shown to exert antiangiogenic properties. High levels of PSA in prostatic tumors may thus slow down cancer progression by inhibiting angiogenesis. We hypothesize that factors stimulating the activity of PSA could be used to reduce prostate tumor growth. Using phage display, we have developed peptides C4 and B2 that stimulate the enzymatic activity of PSA. Our aim was to study whether these peptides enhance the antiangiogenic activity of PSA.

METHODS

We used an in vitro angiogenesis assay where human umbilical vein endothelial cells (HUVECs) form tubular networks when they are grown on Matrigel. Proteolytically active PSA and peptides that stimulate the activity of PSA were added to the cells. Endothelial cell tube formation was quantified and expressed as an angiogenesis index.

RESULTS

PSA reduced the angiogenesis index to ∼50% of controls both in serum-containing and serum-free medium. The addition of peptide C4 or B2 together with PSA caused a significant further decrease in angiogenesis index to ∼70% of that caused by PSA alone. A similar decrease in angiogenesis index was observed when PSA concentration was increased 2.4-fold of that used with peptides.

CONCLUSIONS

The inhibitory effect of PSA on tube formation can be enhanced by the addition of peptides that stimulate the activity of PSA. This supports our hypothesis that stimulation of PSA activity can be used to reduce angiogenesis and thereby inhibit prostate tumor growth.

Trypsin-like proteolytic contamination of commercially available psa purified from human seminal fluid

BACKGROUND

Prostate-Specific Antigen (PSA) is a serine protease whose expression is maintained in all stages of prostate cancer. A role for PSA in the pathobiology for prostate cancer has not been firmly established. Experimental studies to date support a role for PSA through mechanisms such as release or processing of growth factors and degradation of the extracellular matrix. Exposure of prostate cancer cells to exogenous PSA also results in gene expression changes. These in vitro and biochemical assays rely on the use of commercially available PSA. Contamination of these commercial preparations can significantly impact the results of these in vitro studies.

METHODS

We characterized PSA and trypsin-like activity of PSA preparations obtained from three commercial sources: Calbiochem, Fitzgerald, and AbD Serotec. Silver stained gels were used to compare the purity of each preparation and mass spectrometry was performed to characterize contaminating proteases.

RESULTS

PSA activity varied between PSA preparations with AbD Serotec PSA having highest degree of activity. Significant trypsin-like activity, which was inhibited by aprotinin, was observed in PSA preparations from Calbiochem and Fitzgerald, but not AbD Serotec. These former two PSA preparations also contained the greatest degree of non-PSA contaminants by silver stain and mass spectrometry.

CONCLUSIONS

Commercially available preparations of PSA contain contaminating proteins, including trypsin-like protease activity, that could potentially complicate the interpretation of results obtained from in vitro studies assessing PSA proteolysis of potential protein substrates and effects of PSA on gene expression.

Enzymatically active prostate-specific antigen promotes growth of human prostate cancers

BACKGROUND

Prostate specific antigen (PSA) is the best-known member of the kallikrein-related peptidase family, with an established role as a prostatic disease biomarker. Although it is produced at high levels by all stages of prostate cancer, it is uncertain if PSA plays a role in prostate cancer initiation and progression. We decided to investigate the impact of PSA and its enzymatic activity on tumor cell growth rates.

METHODS

A gene-specific shRNA lentiviral construct reduced endogenous PSA expression in the LNCaP human prostate cancer cell line. Resulting changes in growth rates in vitro and in vivo were determined. Using a mass spectroscopy-based approach, alterations to the LNCaP proteome due to reduced PSA were measured. Finally, to evaluate the importance of PSA's proteolytic activity, the PSA-null Du145 human prostate cancer cell line was engineered to express either enzymatically inactive pro-PSA (WT) or a furin-activated variant (FR) with high enzymatic activity. The resulting clones were evaluated for PSA-induced changes in growth rates in vivo and in vitro.

RESULTS

Lowered PSA levels dramatically reduced LNCaP growth rates. Expressing active PSA (FR), but not the inactive WT variant, conferred a growth advantage on Du145 cells. Proteomics analysis revealed global changes to the LNCaP proteome as a result of reduced PSA expression.

CONCLUSIONS

These studies demonstrate the importance of PSA to prostate cancer cell growth. We also show that the enzymatic activity of PSA confers an enhanced growth rate to human prostate cancer cells, suggesting a causal role in prostate cancer progression.

Enzymatic activity of free-prostate-specific antigen (f-PSA) is not required for some of its physiological activities

BACKGROUND

Prostate specific antigen (PSA) is a well known biomarker for early diagnosis and management of prostate cancer. Furthermore, PSA has been documented to have anti-angiogenic and anti-tumorigenic activities in both in vitro and in vivo studies. However, little is known about the molecular mechanism(s) involved in regulation of these processes, in particular the role of the serine-protease enzymatic activity of PSA.

METHODS

Enzymatic activity of PSA isolated directly from seminal plasma was inhibited specifically (>95%) by incubation with zinc2+ . Human umbilical vein endothelial cells (HUVEC) were utilized to compare/contrast the physiological effects of enzymatically active versus inactive PSA.

RESULTS

Equimolar concentrations of enzymatically active PSA and PSA enzymatically inactivated by incubation with Zn2+ had similar physiological effects on HUVEC, including inhibiting the gene expression of pro-angiogenic growth factors, like VEGF and bFGF, and up-regulation of expression of the anti-angiogenic growth factor IFN-γ; suppression of mRNA expression for markers of blood vessel development, like FAK, FLT, KDR, TWIST-1; P-38; inhibition of endothelial tube formation in the in vitro Matrigel Tube Formation Assay; and inhibition of endothelial cell invasion and migration properties.

DISCUSSION

Our data provides compelling evidence that the transcriptional regulatory and the anti-angiogenic activities of human PSA are independent of the innate enzymatic activity.

The discovery of compounds that stimulate the activity of kallikrein-related peptidase 3 (KLK3)

Kallikrein-related peptidase 3 (KLK3), also known as prostate-specific antigen (PSA), is the most useful biomarker for prostate cancer (PCa). KLK3 is suggested to play a role in regulating cancer growth through anti-angiogenic activity in vivo and in vitro. This feature, together with its specificity for prostate tissue, makes KLK3 an intriguing target for the design of new therapies for PCa. 3D pharmacophores for KLK3-stimulating compounds were generated based on peptides that bind specifically to KLK3 and increase its enzymatic activity. As a result of pharmacophore-based virtual screening, four small, drug-like compounds with affinity for KLK3 were discovered and validated by capillary differential scanning calorimetry. One of the compounds also stimulated the activity of KLK3, and is therefore the first published small molecule with such an activity.

A novel paradigm for potential drug-targets discovery: quantifying relationships of enzymes and cascade interactions of neighboring biological processes to identify drug-targets

Target discovery is the most crucial step in a modern drug discovery development. Our objective in this study is to propose a novel paradigm for a better discrimination of drug-targets and non-drug-targets with minimum disruptive side-effects under a biological pathway context. We introduce a novel metric, namely, "pathway closeness centrality", for each gene that jointly considers the relationships of its neighboring enzymes and cross-talks of biological processes, to evaluate its probability of being a drug-target. This metric could distinguish drug-targets with non-drug-targets. Genes with lower pathway closeness centrality values are prone to play marginal roles in biological processes and have less lethality risk, but appear to have tissue-specific expressions. Compared with traditional metrics, our method outperforms degree, betweenness and bridging centrality under the human pathway context. Analysis of the existing top 20 drugs with the most disruptive side-effects indicates that pathway closeness centrality is an appropriate index to predict the probability of the occurrence of adverse pharmacological effects. Case studies in prostate cancer and type 2 diabetes mellitus indicate that the pathway closeness centrality metric could distinguish likely drug-targets well from human pathways. Thus, our method is a promising tool to aid target identification in drug discovery.

Kallikreins on steroids: structure, function, and hormonal regulation of prostate-specific antigen and the extended kallikrein locus

The 15 members of the kallikrein-related serine peptidase (KLK) family have diverse tissue-specific expression profiles and putative proteolytic functions. The kallikrein family is also emerging as a rich source of disease biomarkers with KLK3, commonly known as prostate-specific antigen, being the current serum biomarker for prostate cancer. The kallikrein locus is also notable because it is extraordinarily responsive to steroids and other hormones. Indeed, at least 14 functional hormone response elements have been identified in the kallikrein locus. A more comprehensive understanding of the transcriptional regulation of kallikreins may help the field make more informed hypotheses about the physiological functions of kallikreins and their effectiveness as biomarkers. In this review, we describe the organization of the kallikrein locus and the structure of kallikrein genes and proteins. We also focus on the transcriptional regulation of kallikreins by androgens, progestins, glucocorticoids, mineralocorticoids, estrogens, and other hormones in animal models and human prostate, breast, and reproductive tract tissues. The interaction of the androgen receptor with androgen response elements in the promoter and enhancer of KLK2 and KLK3 is also summarized in detail. There is evidence that all kallikreins are regulated by multiple nuclear receptors. Yet, apart from KLK2 and KLK3, it is not clear whether all kallikreins are direct transcriptional targets. Therefore, we argue that gaining more detailed information about the mechanisms that regulate kallikrein expression should be a priority of future studies and that the kallikrein locus will continue to be an important model in the era of genome-wide analyses.

Prostate-specific antigen: an overlooked candidate for the targeted treatment and selective imaging of prostate cancer

The role of prostate-specific antigen (PSA) or kallikrein-related peptidase 3 (KLK3) as a biomarker for prostate cancer is well known; however, the precise physiological role of it's serine protease activity in prostate cancer remains a mystery. PSA is produced at high levels by both androgen-dependent and -independent prostate cancers. Studies have documented high levels of active PSA in the milieu surrounding osseous and soft tissue metastases. This evidence, coupled with growing experimental evidence, suggests that PSA plays an important role in the pathobiology of prostate cancer. These observations support the development of PSA-selective inhibitors as useful tools for the targeted treatment and imaging of prostate cancer. Here, we review the research that has been conducted to date on developing selective inhibitors for PSA. The different approaches used to determine PSA substrate specificity and for creating inhibitors are discussed. In addition, the unique active site characteristics of PSA and how these motifs aided our research in developing PSA targeted agents are highlighted.

Antiangiogenic properties of prostate-specific antigen (PSA)

The prostate produces high levels of prostate-specific antigen (PSA, also known as kallikrein-related peptidase 3, KLK3), which is a potential target for tumor imaging and treatment. Although serum PSA levels are elevated in prostate cancer, PSA expression is lower in malignant than in normal prostatic epithelium and it is further reduced in poorly differentiated tumors. PSA has been shown to inhibit angiogenesis both in in vitro and in vivo models. In this review we focus on our recent studies concerning the mechanism of the antiangiogenic function of PSA. We have recently shown that the antiangiogenic activity of PSA is related to its enzymatic activity. Inactive PSA isoforms do not have antiangiogenic activity as studied by a human umbelical vein endothelial cell (HUVEC) tube formation model. Furthermore, inhibition of PSA, either by a monoclonal antibody or small molecule inhibitors abolishes the effect of PSA, while a peptide that stimulates the activity of PSA enhances the antiangiogenic effect. We have analyzed changes in gene expression associated with the PSA induced reduction of tube formation in the HUVEC model. Several small changes were observed and they were found to be opposite to those associated with tube formation. Taken together, these studies suggest that PSA exerts antiantiogenic activity related to its enzymatic activity. Thus it might be associated with the slow growth of prostate cancer.

Association of prostate-specific antigen promoter genotype with clinical and histopathologic features of prostate cancer

The serum test for the secreted protease prostate-specific antigen (PSA) is the most widely used screening tool for prostate cancer. The PSA gene contains multiple functional and nonfunctional single nucleotide polymorphisms (SNP) in its promoter. We showed previously that the rs925013 G/A SNP, but not the rs266882 G/A SNP, was significantly associated with serum PSA in healthy men. In this study, we evaluated the association of the PSA promoter genotype with clinical data in a cohort of 1,224 men with prostate cancer. Previous work with a subset of this cohort has shown that percent high-grade (Gleason grades 4 and 5) cancer was the strongest predictor of biochemical recurrence (PSA relapse). We found a statistically significant association (P < 0.05) of the rs925013 SNP with several clinical and histomorphologic variables. The G allele was associated with higher serum PSA at diagnosis, higher percent Gleason grade 3 cancer, and lower percent high-grade and Gleason grade 4 cancer. The rs266882 SNP was modestly associated with PSA at diagnosis in a dominant model but was not associated with cancer grade. Neither SNP was associated with biochemical recurrence. The statistically significant predictors of biochemical recurrence were tumor location in the peripheral zone [odds ratio (OR), 10.71; 95% confidence interval (95% CI), 3.15-36.49], presence of any Gleason grade 4/5 cancer (OR, 4.26; 95% CI, 1.30-14.00), presence of any intraductal cancer (OR, 1.03; 95% CI, 1.00-1.04), and serum PSA at diagnosis (OR, 2.04; 95% CI, 1.50-2.77).

The Tissue Kallikrein Family of Serine Proteases: Functional Roles in Human Disease and Potential as Clinical Biomarkers

Prostate specific antigen (PSA) or human kallikrein 3 (hK3) has long been an effective biomarker for prostate cancer. Now, other members of the tissue kallikrein (KLK) gene family are fast becoming of clinical interest due to their potential as prognostic biomarkers. particularly for hormone dependent cancers. The tissue kallikreins are serine proteases that are encoded by highly conserved multi-gene family clusters in rodents and humans. The rat and mouse loci contain 10 and 25 functional genes, respectively, while the human locus at 19q 13.4 contains 15 genes. The structural organization and size of these genes are similar across species; all genes have 5 coding exons that encode a prepro-enzyme. Although the physiological activators of these zymogens have not been described, in vitro biochemical studies show that some kallikreins can auto-activate and others can activate each other, suggesting that the kallikreins may participate in an enzymatic cascade similar to that of the coagulation cascade. These genes are expressed, to varying degrees, in a wide range of tissues suggesting a functional involvement in a diverse range of physiological and pathophysiological processes. These include roles in normal skin desquamation and psoriatic lesions, tooth development, neural plasticity, and Alzheimer's disease (AD). Of particular interest is the expression of many kallikreins in prostate, ovarian, and breast cancers where they are emerging as useful prognostic indicators of disease progression.

Proteomic profiling of the effect of prostate-specific antigen on prostate cancer cells

BACKGROUND

Prostate-specific antigen (PSA) is a well-known biomarker for diagnosis and management of prostate cancer. PSA has been shown to have anti-angiogenic activity. We used the emerging proteomic research technology to identify proteins in prostate cancer cells whose expression is regulated by enzymatically active PSA.

METHODS

Differentially expressed proteins in PC-3M cells treated with PSA were analyzed by 2D-DIGE analysis and identified by HPLC-MS/MS and SEQUEST data mining. Biological network analysis was carried out using MetaCore integrated software designed for functional analysis of experimental data. Gene expression data for several regulated proteins were confirmed by real-time, quantitative PCR.

RESULTS

A total of 41 proteins were significantly (P < 0.05) changed in abundance in PC-3M cells in response to PSA treatment. Proteins from 26 gel-spots were identified. Many of the down-regulated proteins including N8 gene product long isoform, laminin receptor, vimentin, DJ-1 and Hsp60 are known to be involved in tumor progression.

DISCUSSION

The relevance of the level of PSA in prostate tissue microenvironment and its relation to tumor progression has not been elucidated. PSA has been shown to down-regulate several proteins that are known to have involvement in tumor progression. This suggests that normal physiological levels of PSA in prostate tissue microenvironment may be promoting non-angiogenic environment and its down-regulation may promote tumor growth.

Development of peptides specifically modulating the activity of KLK2 and KLK3

The prostate produces several proteases, the most abundant ones being kallikrein-related peptidase 3 (KLK3, PSA) and KLK2 (hK2), which are potential targets for tumor imaging and treatment. KLK3 expression is lower in malignant than in normal prostatic epithelium and it is further reduced in poorly differentiated tumors, in which the expression of KLK2 is increased. KLK3 has been shown to inhibit angiogenesis, whereas KLK2 may mediate tumor growth and invasion by participating in proteolytic cascades. Thus, it may be possible to control prostate cancer growth by modulating the proteolytic activity of KLK3 and KLK2. We have developed peptides that very specifically stimulate the activity of KLK3 or inhibit that of KLK2. Using these peptides we have established peptide-based methods for the determination of enzymatically active KLK3. The first-generation peptides are unstable in vivo and are rapidly cleared from the circulation. Currently we are modifying the peptides to make them suitable for in vivo applications. We have been able to considerably improve the stability of KLK2-binding peptides by cyclization. In this review we summarize the possible roles of KLK3 and KLK2 in prostate cancer and then concentrate on the development of peptides that modulate the activity of these proteases.

Novel small molecule inhibitors for prostate-specific antigen

BACKGROUND

Prostate-specific antigen (PSA or KLK3) has been shown to inhibit angiogenesis, but it might also have tumor promoting activities. Thus, it may be possible to modulate prostate cancer growth by stimulating or inhibiting the activity of PSA. To this end we have previously identified peptides that stimulate the activity of PSA. As peptides have several limitations as drug molecules, we screened a chemical library to find drug-like compounds that could be used to modulate the function(s) of PSA.

METHODS

Almost 50,000 compounds were analyzed for their ability to modulate PSA activity towards a fluorescent PSA-substrate. The ability of the most active compounds to affect the anti-angiogenic activity of PSA was analyzed by human umbilical vein endothelial cell (HUVEC) tube formation assay.

RESULTS

In the initial screening we identified two compounds that inhibited PSA activity. Based on these, similar compounds were selected and tested for activity to define structure-activity relationships. Several compounds with micromolar IC50-values were found, but they were not entirely specific towards PSA, e.g., they inhibited chymotrypsin, which has similar substrate specificity as PSA. However, it was possibly to improve the selectivity of the compounds towards PSA by small structural changes. These compounds inhibited the anti-angiogenic activity of PSA in the HUVEC model, proving that the proteolytic activity of PSA is essential for inhibition of angiogenesis.

CONCLUSIONS

We found several PSA inhibitors that could be useful tools for studying the role of PSA in cancer models and in normal physiology as showed in angiogenesis model.

Structural characterization and anti-angiogenic properties of prostate-specific antigen isoforms in seminal fluid

BACKGROUND

The prostate produces high levels of prostate-specific antigen (PSA), which has been shown to exert anti-angiogenic properties and thus might slow down prostate tumor growth. It has been suggested that the protease activity of PSA is not needed for its anti-angiogenic function. We have previously shown that seminal fluid contains both active and inactive, internally cleaved forms of PSA. The precise structural differences between these isoforms and their function are not known.

METHODS

To elucidate the structures, we purified PSA from seminal fluid and separated it by anion-exchange chromatography into six different isoforms, which were characterized by mass spectrometry. The anti-angiogenic activity of these PSA-isoforms was analyzed by human umbilical vein endothelial cell (HUVEC) tube formation assay.

RESULTS

The enzymatically active PSA-isoforms had an intact peptide moiety but could be separated into three isoforms based on differences in glycosylation. The major isoform contained PSA with a biantennary carbohydrate with terminal sialic acids on both antennae. The other active isoforms showed significant carbohydrate heterogeneity, containing one or no sialic acid. The inactive isoforms were internally cleaved at several different positions, but the fragments were held together by disulphide bonds. The enzymatic activity of PSA correlated with its inhibitory effect on the endothelial cell tube formation and the inhibition was dose-dependent at physiological concentrations, whereas enzymatically inactive internally cleaved PSA-isoforms had no effect.

CONCLUSIONS

Our results show that the anti-angiogenic effect of PSA is based on its proteolytic activity.

Gene expression changes associated with the anti-angiogenic activity of kallikrein-related peptidase 3 (KLK3) on human umbilical vein endothelial cells

Kallikrein-related peptidase 3 (KLK3, also known as prostate-specific antigen, PSA) is a chymotrypsin-like kallikrein that has anti-angiogenic properties. We have previously shown in a human umbilical vein endothelial cell (HUVEC) model that the anti-angiogenic effect of KLK3 is related to its enzyme activity. However, the mechanism of this effect remains to be clarified. To this end, we used a DNA microarray to study KLK3-induced changes in gene expression associated with reduction of HUVEC tube formation. Among the 41 000 genes studied, 311 were differentially expressed between control and KLK3-treated cells. These changes were enriched in several pathways, including those associated with proteasome, ubiquitin-mediated proteolysis, focal adhesion and regulation of the actin cytoskeleton. Furthermore, the changes were opposite to those previously described to occur during tubulogenesis. In conclusion, our results show that KLK3 induces gene expression changes in HUVECs. Although these changes might be relevant for the mechanism by which KLK3 exerts its anti-angiogenic activity, it cannot be judged from the present results whether they reflect the primary mechanism mediating the effect of KLK3 or are secondary to morphogenic differentiation.

Emerging roles of proteases in tumour suppression

Proteases have long been associated with cancer progression because of their ability to degrade extracellular matrices, which facilitates invasion and metastasis. However, recent studies have shown that these enzymes target a diversity of substrates and favour all steps of tumour evolution. Unexpectedly, the post-trial studies have also revealed proteases with tumour-suppressive effects. These effects are associated with more than 30 different enzymes that belong to three distinct protease classes. What are the clinical implications of these findings?

New insights into the functional mechanisms and clinical applications of the kallikrein-related peptidase family

The Kallikrein-related peptidase (KLK) family consists of fifteen conserved serine proteases that form the largest contiguous cluster of proteases in the human genome. While primarily recognized for their clinical utilities as potential disease biomarkers, new compelling evidence suggests that this family plays a significant role in various physiological processes, including skin desquamation, semen liquefaction, neural plasticity, and body fluid homeostasis. KLK activation is believed to be mediated through highly organized proteolytic cascades, regulated through a series of feedback loops, inhibitors, auto-degradation and internal cleavages. Gene expression is mainly hormone-dependent, even though transcriptional epigenetic regulation has also been reported. These regulatory mechanisms are integrated with various signaling pathways to mediate multiple functions. Dysregulation of these pathways has been implicated in a large number of neoplastic and non-neoplastic pathological conditions. This review highlights our current knowledge of structural/phylogenetic features, functional role and regulatory/signaling mechanisms of this important family of enzymes.

Does PSA play a role as a promoting agent during the initiation and/or progression of prostate cancer?

Prostate cancer cells, like normal prostate epithelial cells, produce high levels of the differentiation marker and serine protease prostate-specific antigen (PSA). PSA is used extensively as a biomarker to screen for prostate cancer, to detect recurrence following local therapies, and to follow response to systemic therapies for metastatic disease. While much is known about PSA's role as a biomarker, only a relatively few studies address the role played by PSA in the pathobiology of prostate cancer. Autopsy studies have documented that not only do prostate cancer cells maintain production of high amounts of PSA but they also maintain the enzymatic machinery required to process PSA to an enzymatically active form. A variety studies performed over the last 10 years have hinted at a role for PSA in growth, progression, and metastases of prostate cancer. A fuller understanding of PSA's functional role in prostate cancer biology, however, has been hampered by the lack of appropriate models and tools. Therefore, the purpose of this review is not to address issues related to PSA as a biomarker. Instead, by reviewing what is known about the genetics, biochemistry, and biology of PSA in normal and malignant prostate tissue, insights may be gained into the role PSA may be playing in the pathobiology of prostate cancer that can connect measurement of this biomarker to an understanding of the underlying etiology and progression of the disease.

The role of kallikrein-related peptidases in prostate cancer: potential involvement in an epithelial to mesenchymal transition

Several members of the kallikrein-related peptidase family of serine proteases have proteolytic activities that may affect cancer progression; however, the in vivo significance of these activities remains uncertain. We have demonstrated that expression of PSA or KLK4, but not KLK2, in PC-3 prostate cancer cells changed the cellular morphology from epithelial to spindle-shaped, markedly reduced E-cadherin expression, increased vimentin expression and increased cellular migration. These changes are indicative of an epithelial to mesenchymal transition (EMT), a process important in embryonic development and cancer progression. The potential novel role of kallikrein-related peptidases in this process is the focus of this brief review.

Recombinant kallikrein expression: site-specific integration for hK6 production in human cells

Kallikreins have been implicated in carcinogenesis and are promising biomarkers for the diagnosis and follow-up of various cancers. To evaluate the functions and clinical interest of kallikreins, it is important to be able to produce them as recombinant proteins. Here we summarize the various strategies used to produce kallikreins, emphasizing their advantages and limitations. We also describe an approach to achieve high-level production of kallikreins, such as hK6, with correct folding and activity, combining an expression system with targeted transgene integration and an efficient cultivation device to increase yield, the CELLine bioreactor. This novel method for recombinant kallikrein production will be useful to study their bio-pathological functions and to develop anti-bodies.

Kallikrein-related peptidase (KLK) family mRNA variants and protein isoforms in hormone-related cancers: do they have a function?

The kallikrein-related peptidase (KLK) gene family of 15 serine proteases encodes many proteins, including prostate specific antigen (PSA or KLK3), that are well described and/or are potential biomarkers for hormone-related cancers. Variant mRNA transcripts produced by alternative splicing, polyadenylation or AUG sites, or intron retention have been found for each of the KLK genes. The predicted protein for many of these alternative transcripts is different from that of the classical kallikrein-related peptidases and would not be an active serine protease. The majority of these novel protein isoforms have not been studied in vivo. The possible function(s) of the variant transcripts/protein isoforms and potential roles that they may play in hormone-related cancers are still unknown and are the focus of this short review.

The antiangiogenic tissue kallikrein pattern of endothelial cells in systemic sclerosis

OBJECTIVE

Postnatal angiogenesis relies on a proper response of endothelial cells to angiogenic stimuli. In systemic sclerosis (SSc), endothelial cells are unresponsive to angiogenic factors. Since circumstantial and experimental evidence points to tissue kallikreins as powerful effectors of the angiogenic response, we undertook this study to investigate the kallikrein pattern of normal and SSc endothelial cells in order to identify differences that can account for defective angiogenesis.

METHODS

Expression of 14 tissue kallikreins was studied by a microarray approach, by reverse transcription-polymerase chain reaction, and by Western blotting in endothelial cells isolated from the skin of clinically healthy subjects and SSc patients. Cell proliferation was quantified by direct cell counting. Invasion and capillary morphogenesis were evaluated in a Boyden chamber and in culture flasks layered with Matrigel. Cyclic nucleotide production was measured by enzyme immunoassay. MAP kinase and ERK activation were measured by Western blotting.

RESULTS

Endothelial cells from SSc patients showed poor expression of kallikreins 9, 11, and 12 compared with endothelial cells from normal subjects. Antibodies against the relevant kallikreins on normal endothelial cells revealed that while kallikreins 9, 11, and 12 induced cell growth, only kallikrein 12 regulated invasion and capillary morphogenesis. Buffering of kallikrein 12 with antibodies resulted in the acquisition of an SSc-like pattern by normal cells in in vitro angiogenesis. Reduction of cAMP and cGMP production and of ERK phosphorylation upon administration of antikallikrein antibodies revealed that the activity of kallikreins 9, 11, and 12 was mediated by kinins.

CONCLUSION

Reduction of tissue kallikreins 9, 11, and 12 may be relevant to reduced angiogenesis in SSc patients.