The new human tissue kallikrein gene family: structure, function, and association to disease

Distinct patterns of 1p and 19q alterations identify subtypes of human gliomas that have different prognoses

We studied the status of chromosomes 1 and 19 in 363 astrocytic and oligodendroglial tumors. Whereas the predominant pattern of copy number abnormality was a concurrent loss of the entire 1p and 19q regions (total 1p/19q loss) among oligodendroglial tumors and partial deletions of 1p and/or 19q in astrocytic tumors, a subset of apparently astrocytic tumors also had total 1p/19q loss. The presence of total 1p/19q loss was associated with longer survival of patients with all types of adult gliomas independent of age and diagnosis (P = .041). The most commonly deleted region on 19q in astrocytic tumors spans 885 kb in 19q13.33-q13.41, which is telomeric to the previously proposed region. Novel regions of homozygous deletion, including a part of DPYD (1p21.3) or the KLK cluster (19q13.33), were observed in anaplastic oligodendrogliomas. Amplifications encompassing AKT2 (19q13.2) or CCNE1 (19q12) were identified in some glioblastomas. Deletion mapping of the centromeric regions of 1p and 19q in the tumors that had total 1p/19q loss, indicating that the breakpoints lie centromeric to NOTCH2 within the pericentromeric regions of 1p and 19q. Thus, we show that the copy number abnormalities of 1p and 19q in human gliomas are complex and have distinct patterns that are prognostically predictive independent of age and pathological diagnosis. An accurate identification of total 1p/19q loss and discriminating this from other 1p/19q changes is, however, critical when the 1p/19q copy number status is used to stratify patients in clinical trials.

Reducing unnecessary biopsy during prostate cancer screening using a four-kallikrein panel: an independent replication

PURPOSE

We previously reported that a panel of four kallikrein forms in blood-total, free, and intact prostate-specific antigen (PSA) and kallikrein-related peptidase 2 (hK2)-can reduce unnecessary biopsy in previously unscreened men with elevated total PSA. We aimed to replicate our findings in a large, independent, representative, population-based cohort.

PATIENTS AND METHODS

The study cohort included 2,914 previously unscreened men undergoing biopsy as a result of elevated PSA (> or = 3 ng/mL) in the European Randomized Study of Screening for Prostate Cancer, Rotterdam, with 807 prostate cancers (28%) detected. The cohort was randomly divided 1:3 into a training and validation set. Levels of kallikrein markers were compared with biopsy outcome.

RESULTS

Addition of free PSA, intact PSA, and hK2 to a model containing total PSA and age improved the area under the curve from 0.64 to 0.76 and 0.70 to 0.78 for models without and with digital rectal examination results, respectively (P < .001 for both). Application of the panel to 1,000 men with elevated PSA would reduce the number of biopsies by 513 and miss 54 of 177 low-grade cancers and 12 of 100 high-grade cancers. Findings were robust to sensitivity analysis.

CONCLUSION

We have replicated our previously published finding that a panel of four kallikreins can predict the result of biopsy for prostate cancer in men with elevated PSA. Use of this panel would dramatically reduce biopsy rates. A small number of men with cancer would be advised against immediate biopsy, but these men would have predominately low-stage, low-grade disease.

Hemopressin and other bioactive peptides from cytosolic proteins: are these non-classical neuropeptides?

Peptides perform many roles in cell-cell signaling; examples include neuropeptides, hormones, and growth factors. Although the vast majority of known neuropeptides are produced in the secretory pathway, a number of bioactive peptides are derived from cytosolic proteins. For example, the hemopressins are a family of peptides derived from alpha and beta hemoglobin which bind to the CB1 cannabinoid receptor, functioning as agonists or antagonists/inverse agonists depending on the size of the peptide. However, the finding that peptides derived from cytosolic proteins can affect receptors does not prove that these peptides are true endogenous signaling molecules. In order for the hemopressins and other peptides derived from cytosolic proteins to be considered neuropeptide-like signaling molecules, they must be synthesized in brain, they must be secreted in levels sufficient to produce effects, and either their synthesis or secretion should be regulated. If these criteria are met, we propose the name "non-classical neuropeptide" for this category of cytosolic bioactive peptide. This would be analogous to the non-classical neurotransmitters, such as nitric oxide and anandamide, which are not stored in secretory vesicles and released upon stimulation but are synthesized upon stimulation and constitutively released. We review some examples of cytosolic peptides from various protein precursors, describe potential mechanisms of their biosynthesis and secretion, and discuss the possibility that these peptides are signaling molecules in the brain, focusing on the criteria that these peptides would have to fill in order to be considered non-classical neuropeptides.

Pathogenesis of ovarian cancer: clues from selected overexpressed genes

Ovarian cancer is the most malignant gynecologic neoplasm. Although new chemotherapeutic agents have improved patients' 5-year survival rate, the overall mortality of ovarian cancer has remained largely unchanged in the past several decades. The main reason for the lack of success in effectively treating ovarian cancer is our limited understanding of its etiology and the very few molecular diagnostic markers and therapeutic targets known so far. Identification and characterization of ovarian cancer-associated genes are fundamental for unveiling the pathogenesis of its initiation and progression, especially the development of recurrent diseases. As there are a vast number of genes for which molecular genetic changes and aberrant gene expression have been reported in ovarian cancer, this review will only focus on summarizing those exemplified genes that have been demonstrated to have biological functions in promoting ovarian cancer development and potential clinical significance. The genes to be discussed include nuclear proteins (Notch3, HBXAP [Rsf-1], NAC1 and NFkappaB), cytoplasmic proteins (fatty acid synthase and apolipoprotein E) and cell surface/secretory proteins (mucin-4, mesothelin, claudin, HLA-G, kallikrein and folate receptor and osteopontin). Since the study of ovarian cancer-associated genes is complicated by several factors unique to ovarian cancer, we will also present our views on the limitations and challenges of current ovarian cancer research.

Apatite reduces amelogenin proteolysis by MMP-20 and KLK4 in vitro

Two enamel proteases, matrix metalloproteinase-20 (MMP-20) and kallikrein 4 (KLK4), are known to cleave amelogenin and are necessary for proper enamel formation. However, the effect of hydroxyapatite (HAP) on the proteolytic activity of these enzymes remains unclear. To investigate whether apatite affects normal amelogenin proteolysis, we used 2 different isoforms of amelogenin combined with the appropriate enzymes to analyze proteolytic processing rates in the presence or absence of synthetic hydroxyapatite (HAP) crystals (N = 3). We found a distinct dose-dependent relationship between the amount of HAP present in the proteolysis mixture and the rate of rP172 degradation by rpMMP-20, whereas the effect of HAP on proteolysis of either rP172 or rP148 by rhKLK4 was less prominent.

Kallikrein expression and cathelicidin processing are independently controlled in keratinocytes by calcium, vitamin D(3), and retinoic acid

Cathelicidin has dual functions in the skin, acting as an innate antibiotic and as an immunomodulator in diseases such as rosacea and psoriasis. The serine proteases kallikrein 5 (KLK5) and kallikrein 7 (KLK7) control enzymatic processing of cathelicidin precursor in the skin and regulate the eventual function of the final forms of these peptides. We analyzed factors that control expression of KLK5 and KLK7 in normal human epidermal keratinocytes to better understand how these may influence cathelicidin processing and function. Increased extracellular calcium-induced KLK5 and KLK7 mRNA expression and protein release in a time-dependent manner that is similar to induction of differentiation markers such as keratin 10 and involucrin. However, 1,25(OH)(2) vitamin D(3), 9-cis retinoic acid (RA), and 13-cis RA also induced the KLKs, but the timing and pattern of KLK induction for each were different and distinct from changes in differentiation markers. Increased protease activity and differential processing of cathelicidin accompanied increased KLK expression. These findings show that the expression and activity of KLK are under fine control and can be distinctly influenced by variables such as differentiation, calcium, vitamin D, and RA. Thus, these variables may further control the functions of antimicrobial peptides in the skin.

A novel signaling pathway of tissue kallikrein in promoting keratinocyte migration: activation of proteinase-activated receptor 1 and epidermal growth factor receptor

Biological functions of tissue kallikrein (TK, KLK1) are mainly mediated by kinin generation and subsequent kinin B2 receptor activation. In this study, we investigated the potential role of TK and its signaling pathways in cultured human keratinocyte migration and in a rat skin wound healing model. Herein, we show that TK promoted cell migration and proliferation in a concentration- and time-dependent manner. Inactive TK or kinin had no significant effect on cell migration. Interestingly, cell migration induced by active TK was not blocked by icatibant or L-NAME, indicating an event independent of kinin B2 receptor and nitric oxide formation. TK's stimulatory effect on cell migration was inhibited by small interfering RNA for proteinase-activated receptor 1 (PAR(1)), and by PAR(1) inhibitor. TK-induced migration was associated with increased phosphorylation of epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase (ERK), which was blocked by inhibition of protein kinase C (PKC), Src, EGFR and ERK. TK-induced cell migration and EGFR phosphorylation were blocked by metalloproteinase (MMP) inhibitor, heparin, and antibodies against EGFR external domain, heparin-binding EGF-like growth factor (HB-EGF) and amphiregulin (AR). Local application of TK promoted skin wound healing in rats, whereas icatibant and EGFR inhibitor blocked TK's effect. Skin wound healing was further delayed by aprotinin and neutralizing TK antibody. This study demonstrates a novel role of TK in skin wound healing and uncovers new signaling pathways mediated by TK in promoting keratinocyte migration through activation of the PAR(1)-PKC-Src-MMP pathway and HB-EGF/AR shedding-dependent EGFR transactivation.

A completed KLK activome profile: investigation of activation profiles of KLK9, 10, and 15

We previously reported the activation profiles of the human kallikrein-related peptidases (KLKs) as determined from a KLK pro-peptide fusion-protein system. That report described the activity profiles of 12 of the 15 mature KLKs versus the 15 different pro-KLK sequences. The missing profiles in the prior report, involving KLK9, 10, and 15, are now described. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, mass spectrometry, and N-terminal sequence analyses show that KLK9 and 10 exhibit low hydrolytic activities towards all of the 15 pro-KLK sequences, while KLK15 exhibits significant activity towards both Arg- and Lys-containing KLK pro-sequences. The ability of KLK15 to activate pro-KLK8, 12, and 14 is confirmed using recombinant pro-KLK proteins, and shown to be significant for activation of pro-KLK8 and 14, but not 12. These additional data for KLK9, 10, and 15 now permit a completed KLK activome profile, using a KLK pro-peptide fusion-protein system, to be described. The results suggest that KLK15, once activated, can potentially feed back into additional pro-KLK activation pathways. Conversely, KLK9 and 10, once activated, are unlikely to participate in further pro-KLK activation pathways, although similar to KLK1 they may activate other bioactive peptides.

Association of TMPRSS2 and KLK11 gene expression levels with clinical progression of human prostate cancer

AIM

The aim of this study was to analyze the clinicopathological characteristics of TMPRSS2 and KLK11 gene expression levels in human prostate cancer (PCa), and to evaluate their clinical significance in the progression of PCa.

METHODS

The expression of prostate-type and brain-type isoforms of KLK11 gene, and TMPRSS2 gene was analyzed by quantitative reverse transcriptase-polymerase chain reaction (QRT-PCR) in 63 PCa tissues. The correlation of TMPRSS2 and KLK11 gene expression with the clinicopathological characteristics and with the prognosis of PCa was subsequently assessed.

RESULTS

The mean values of TMPRSS2 (3.91 +/- 0.78 in PCa vs. 0.26 +/- 0.04 in normal prostate tissues) and both isoforms of KLK11 (prostate-type: 3.63 +/- 0.42 in PCa vs. 0.49 +/- 0.07 in normal prostate tissues; brain-type: 3.11 +/- 0.30 in PCa vs. 0.46 +/- 0.05 in normal prostate tissues) were significantly higher in cancer tissues compared with their normal counterparts. We found a significant positive correlation between TMPRSS2 expression and tumor stage (P = 0.02), Gleason score (P = 0.008), and tumor grade (P = 0.016). Regarding prostate-type KLK11, we identified a significant association between lower expression and higher tumor stage (P = 0.009), Gleason score (P = 0.01), and tumor grade (P = 0.006). No such association was seen with the brain-type isoform. The survival rate of the patients with TMPRSS2-high/KLK11-low expression was lowest (P = 0.003).

CONCLUSION

The results suggest that the up-regulation of TMPRSS2 gene and the down-regulation of KLK11 gene in advanced and more aggressive tumors may open the feasibility of being used as biomarkers distinguishing the tumor aggressiveness as well as novel prognostic indicators for PCa.

Identification of lympho-epithelial Kazal-type inhibitor 2 in human skin as a kallikrein-related peptidase 5-specific protease inhibitor

Kallikreins-related peptidases (KLKs) are serine proteases and have been implicated in the desquamation process of the skin. Their activity is tightly controlled by epidermal protease inhibitors like the lympho-epithelial Kazal-type inhibitor (LEKTI). Defects of the LEKTI-encoding gene serine protease inhibitor Kazal type (Spink)5 lead to the absence of LEKTI and result in the genodermatose Netherton syndrome, which mimics the common skin disease atopic dermatitis. Since many KLKs are expressed in human skin with KLK5 being considered as one of the most important KLKs in skin desquamation, we proposed that more inhibitors are present in human skin. Herein, we purified from human stratum corneum by HPLC techniques a new KLK5-inhibiting peptide encoded by a member of the Spink family, designated as Spink9 located on chromosome 5p33.1. This peptide is highly homologous to LEKTI and was termed LEKTI-2. Recombinant LEKTI-2 inhibited KLK5 but not KLK7, 14 or other serine proteases tested including trypsin, plasmin and thrombin. Spink9 mRNA expression was detected in human skin samples and in cultured keratinocytes. LEKTI-2 immune-expression was focally localized at the stratum granulosum and stratum corneum at palmar and plantar sites in close localization to KLK5. At sites of plantar hyperkeratosis, LEKTI-2 expression was increased. We suggest that LEKTI-2 contributes to the regulation of the desquamation process in human skin by specifically inhibiting KLK5.

Over-expression of human kallikrein 11 is associated with poor prognosis in patients with low rectal carcinoma

AIM

The goal of this study was to analyze the expression of human kallikrein 11 (hK11) in low rectal carcinoma (LRC) tissues, as well as its association with the clinicopathologic features of LRC patients and its prognostic significance.

METHODS

Between January 1998 and January 2003, 126 patients with LRC were randomized to receive laparoscopic-assisted abdominoperineal resection (APR). Their hK11 expression levels were examined by immunostaining on paraffin-embedded tumor specimens. Then the association of hK11 expression with clinicopathologic characteristics and patients' prognosis was analyzed.

RESULTS

The positive degree of immunohistochemical staining in cancerous tissues (1.86 +/- 0.02) was higher than that in the control group (1.18 +/- 0.11, P = 0.008). Strong positive hK11 staining associated significantly with various clinicopathologic features, such as Dukes Staging (P < 0.001), histological differentiation grade (P = 0.003), CEA level (P = 0.01), lymph node metastasis (P < 0.001), and invasion depth (P = 0.002). Patients with weak hK11 positive expression showed better survival rates of 5-year follow-up than those with strong positive expression (80.85% for weak positive expression and 58.23% in strong positive expression, respectively; P < 0.01 for analyses). Using Cox regression analysis of the 126 patients, strong positive expression of hK11, Dukes Staging, lymph node metastasis, and invasion depth seemed to be independent prognostic indicators (P < 0.01, P = 0.02, P < 0.01 and P < 0.01, respectively).

CONCLUSION

hK11 may be another prognostic biomarker of LRC. Knowledge of hK11 expression in LRC tissues could contribute to the prediction of prognosis of LRC patients.

Enamel proteases reduce amelogenin-apatite binding

Organic matrix degradation and crystal maturation are extracellular events that occur simultaneously during enamel biomineralization. We hypothesized that enamel proteases control amelogenin-mineral interaction, which, in turn can affect crystal nucleation, organization, and growth. We used a recombinant amelogenin (rP172), a homolog of its major cleavage product (rP148), and a native amelogenin lacking both N- and C-termini (13k). We compared apatite binding affinity between amelogenins and their digest products during proteolysis. We further compared binding affinity among the 3 amelogenins using a Langmuir model for protein adsorption. Amelogenin-apatite binding affinity was progressively reduced with the proteolysis at the C- and N- termini by recombinant pig MMP-20 (rpMMP20) and recombinant human kallikrein-4 (rhKLK4), respectively. The binding affinity of amelogenin to apatite was found to be in the descending order of rP172, rP148, and 13k. Analysis of our data suggests that, before its complete degradation during enamel maturation, stepwise processing of amelogenin by MMP-20 and then KLK4 reduces amelogenin-apatite interaction.

Differential N-glycosylation of kallikrein 6 derived from ovarian cancer cells or the central nervous system

Ovarian cancer causes more deaths than any other gynecological disorder. Perturbed glycosylation is one of the hallmarks of this malignancy. Kallikrein 6 (KLK6) elevation in serum is a diagnostic and prognostic indicator in ovarian cancer. The majority of ovarian carcinomas express high levels of KLK6, which diffuses into the circulation. Under physiological conditions, KLK6 is expressed highly in the central nervous system and found at high levels in cerebrospinal fluid from where it enters the circulation. Our aim was to characterize and compare the N-glycosylation status of this protein in ovarian cancer ascites fluid and cerebrospinal fluid. Anion-exchange chromatography was used to reveal different post-translational modifications on the two isoforms. Mobility gel shift Western blot analysis coupled with glycosidase digestion showed that the molecular weight difference between the two isoforms was because of differential glycosylation patterns. The presence of a single N-glycosylation site on KLK6 was confirmed by site-directed mutagenesis. Using a Sambucus nigra agglutinin-monoclonal antibody sandwich enzyme-linked immunosorbent assay approach, it was shown that ovarian cancer-derived KLK6 was modified with alpha2-6-linked sialic acid. The structure and composition of glycans of both KLK6 isoforms was elucidated by glycopeptide monitoring with electrospray ionization-Orbitrap tandem mass spectrometry. Therefore, the extensive and almost exclusive sialylation of KLK6 from ovarian cancer cells could lead to the development of an improved biomarker for the early diagnosis of ovarian carcinoma.

Multivariate gene expression analysis reveals functional connectivity changes between normal/tumoral prostates

BACKGROUND

Prostate cancer is a leading cause of death in the male population, therefore, a comprehensive study about the genes and the molecular networks involved in the tumoral prostate process becomes necessary. In order to understand the biological process behind potential biomarkers, we have analyzed a set of 57 cDNA microarrays containing approximately 25,000 genes.

RESULTS

Principal Component Analysis (PCA) combined with the Maximum-entropy Linear Discriminant Analysis (MLDA) were applied in order to identify genes with the most discriminative information between normal and tumoral prostatic tissues. Data analysis was carried out using three different approaches, namely: (i) differences in gene expression levels between normal and tumoral conditions from an univariate point of view; (ii) in a multivariate fashion using MLDA; and (iii) with a dependence network approach. Our results show that malignant transformation in the prostatic tissue is more related to functional connectivity changes in their dependence networks than to differential gene expression. The MYLK, KLK2, KLK3, HAN11, LTF, CSRP1 and TGM4 genes presented significant changes in their functional connectivity between normal and tumoral conditions and were also classified as the top seven most informative genes for the prostate cancer genesis process by our discriminant analysis. Moreover, among the identified genes we found classically known biomarkers and genes which are closely related to tumoral prostate, such as KLK3 and KLK2 and several other potential ones.

CONCLUSION

We have demonstrated that changes in functional connectivity may be implicit in the biological process which renders some genes more informative to discriminate between normal and tumoral conditions. Using the proposed method, namely, MLDA, in order to analyze the multivariate characteristic of genes, it was possible to capture the changes in dependence networks which are related to cell transformation.

C19orf48 encodes a minor histocompatibility antigen recognized by CD8+ cytotoxic T cells from renal cell carcinoma patients

PURPOSE

Tumor regression has been observed in some patients with metastatic renal cell carcinoma (RCC) after nonmyeloablative allogeneic hematopoietic cell transplantation (HCT). Cellular and molecular characterization of antigens recognized by tumor-reactive T cells isolated from responding patients could potentially provide insight into the mechanisms of tumor regression.

EXPERIMENTAL DESIGN

CD8+ CTL clones that recognized a novel RCC-associated minor histocompatibility (H) antigen presented by HLA-A*0201 were isolated from two patients with metastatic RCC who experienced tumor regression or stable disease following nonmyeloablative allogeneic HCT. These clones were used to screen a cDNA library and isolate the unique cDNA encoding the antigen.

RESULTS

An alternative open reading frame in the C19orf48 gene located on chromosome 19q13 encodes the HLA-A*0201-restricted minor H antigen recognized by the RCC-reactive T cells. The differential T-cell recognition of donor- and recipient-derived target cells is attributable to a nonsynonymous single-nucleotide polymorphism within the nucleotide interval that encodes the antigenic peptide. Assays for gene expression and CTL recognition showed that the C19orf48-encoded peptide is widely expressed in renal tumors and solid tumors of other histologies. The antigenic peptide can be processed for CTL recognition via both TAP-dependent and TAP-independent pathways.

CONCLUSIONS

Donor T-cell responses against the HLA-A*0201-restricted minor H antigen encoded by C19orf48 may contribute to RCC regression after MHC-matched allogeneic HCT.

Human kallikrein 8 expression in salivary gland tumors

The human kallikrein 8 protein (KLK8) is expressed in many normal tissues including esophagus, skin, testis, tonsil, kidney, breast, and salivary gland, and is found in biological fluids including breast milk, amniotic fluid, seminal fluid and serum. It has also been shown to be a biomarker and prognostic factor for breast cancer. The aim of this study was to determine whether KLK8 is expressed in salivary gland tissues and salivary gland tumors (both benign and malignant), in order to compare normal with tumor tissues. Pleomorphic adenomas, adenoid cystic carcinomas, polymorphous low grade adenocarcinomas, acinic cell carcinomas, mucoepidermoid carcinomas, and adenocarcinomas NOS of both minor and major salivary glands were examined. The results of this study indicate that most salivary gland tumors show high levels of expression of KLK8.

Activation profiles of human kallikrein-related peptidases by proteases of the thrombostasis axis

The human kallikrein-related peptidases (KLKs) comprise 15 members (KLK1-15) and are the single largest family of serine proteases. The KLKs are utilized, or proposed, as clinically important biomarkers and therapeutic targets of interest in cancer and neurodegenerative disease. All KLKs appear to be secreted as inactive pro-forms (pro-KLKs) that are activated extracellularly by specific proteolytic release of their N-terminal pro-peptide. This processing is a key step in the regulation of KLK function. Much recent work has been devoted to elucidating the potential for activation cascades between members of the KLK family, with physiologically relevant KLK regulatory cascades now described in skin desquamation and semen liquefaction. Despite this expanding knowledge of KLK regulation, details regarding the potential for functional intersection of KLKs with other regulatory proteases are essentially unknown. To elucidate such interaction potential, we have characterized the ability of proteases associated with thrombostasis to hydrolyze the pro-peptide sequences of the KLK family using a previously described pro-KLK fusion protein system. A subset of positive hydrolysis results were subsequently quantified with proteolytic assays using intact recombinant pro-KLK proteins. Pro-KLK6 and 14 can be activated by both plasmin and uPA, with plasmin being the best activator of pro-KLK6 identified to date. Pro-KLK11 and 12 can be activated by a broad-spectrum of thrombostasis proteases, with thrombin exhibiting a high degree of selectivity for pro-KLK12. The results show that proteases of the thrombostasis family can efficiently activate specific pro-KLKs, demonstrating the potential for important regulatory interactions between these two major protease families.

Impact of cytogenetic and genomic aberrations of the kallikrein locus in ovarian cancer

The tissue kallikrein (KLK) genes are a new source for biomarkers in ovarian cancer. However, there has been no systematic analysis of copy number and structural rearrangements related to their protein expression. Chromosomal rearrangements and copy number changes of the KLK region were studied by FISH with protein levels measured by ELISA. Ovarian cancer and cell lines revealed the KLK region was subject to copy number imbalances or involved in unbalanced translocations and were associated with increased protein expression of KLKs 5, 6, 7, 8, 9, 10 and 11. In this initial study, we introduce the potential for long-range chromosomal effects and copy number as a mechanism for the previously reported aberrant expression of many KLK genes in ovarian cancers.

Characterization of global transcription profile of normal and HPV-immortalized keratinocytes and their response to TNF treatment

BACKGROUND

Persistent infection by high risk HPV types (e.g. HPV-16, -18, -31, and -45) is the main risk factor for development of cervical intraepithelial neoplasia and cervical cancer. Tumor necrosis factor (TNF) is a key mediator of epithelial cell inflammatory response and exerts a potent cytostatic effect on normal or HPV16, but not on HPV18 immortalized keratinocytes. Moreover, several cervical carcinoma-derived cell lines are resistant to TNF anti-proliferative effect suggesting that the acquisition of TNF-resistance may constitute an important step in HPV-mediated carcinogenesis. In the present study, we compared the gene expression profiles of normal and HPV16 or 18 immortalized human keratinocytes before and after treatment with TNF for 3 or 60 hours.

METHODS

In this study, we determined the transcriptional changes 3 and 60 hours after TNF treatment of normal, HPV16 and HPV18 immortalized keratinocytes by microarray analysis. The expression pattern of two genes observed by microarray was confirmed by Northern Blot. NF-kappaB activation was also determined by electrophoretic mobility shift assay (EMSA) using specific oligonucleotides and nuclear protein extracts.

RESULTS

We observed the differential expression of a common set of genes in two TNF-sensitive cell lines that differs from those modulated in TNF-resistant ones. This information was used to define genes whose differential expression could be associated with the differential response to TNF, such as: KLK7 (kallikrein 7), SOD2 (superoxide dismutase 2), 100P (S100 calcium binding protein P), PI3 (protease inhibitor 3, skin-derived), CSTA (cystatin A), RARRES1 (retinoic acid receptor responder 1), and LXN (latexin). The differential expression of the KLK7 and SOD2 transcripts was confirmed by Northern blot. Moreover, we observed that SOD2 expression correlates with the differential NF-kappaB activation exhibited by TNF-sensitive and TNF-resistant cells.

CONCLUSION

This is the first in depth analysis of the differential effect of TNF on normal and HPV16 or HPV18 immortalized keratinocytes. Our findings may be useful for the identification of genes involved in TNF resistance acquisition and candidate genes which deregulated expression may be associated with cervical disease establishment and/or progression.

Substrate specificity of human kallikreins 1 and 6 determined by phage display

The human tissue kallikrein (KLK) family contains 15 secreted serine proteases that are expressed in a wide range of tissues and have been implicated in different physiological functions and disease states. Of these, KLK1 has been shown to be involved in the regulation of multiple physiological processes such as blood pressure, smooth muscle contraction, and vascular cell growth. KLK6 is overexpressed in breast and ovarian cancer tissues and has been shown to cleave peptide derived from human myelin protein and Abeta amyloid peptide in vitro. Here we analyzed the substrate specificity of KLK1 and KLK6, by substrate phage display using a random octapeptide library. Consistent with earlier biochemical data, KLK1 was shown to exhibit both trypsin- and chymotrypsin-like selectivities with Tyr/Arg preferred at site P1, Ser/Arg strongly preferred at P1', and Phe/Leu at P2. KLK6 displayed trypsin-like activity, with the P1 position occupied only by Arg and a strong preference for Ser in P1'. Docking simulations of consensus peptide provide information on the identity of the enzyme residues that are responsible for substrate binding. Bioinformatic analysis suggested several putative KLK6 protein substrates, such as ionotropic glutamate receptor (GluR) and synphilin.

Frequent expression loss of Inter-alpha-trypsin inhibitor heavy chain (ITIH) genes in multiple human solid tumors: a systematic expression analysis

Background

The inter-alpha-trypsin inhibitors (ITI) are a family of plasma protease inhibitors, assembled from a light chain – bikunin, encoded by AMBP – and five homologous heavy chains (encoded by ITIH1, ITIH2, ITIH3, ITIH4, and ITIH5), contributing to extracellular matrix stability by covalent linkage to hyaluronan. So far, ITIH molecules have been shown to play a particularly important role in inflammation and carcinogenesis.

Methods

We systematically investigated differential gene expression of the ITIH gene family, as well as AMBP and the interacting partner TNFAIP6 in 13 different human tumor entities (of breast, endometrium, ovary, cervix, stomach, small intestine, colon, rectum, lung, thyroid, prostate, kidney, and pancreas) using cDNA dot blot analysis (Cancer Profiling Array, CPA), semiquantitative RT-PCR and immunohistochemistry.

Results

We found that ITIH genes are clearly downregulated in multiple human solid tumors, including breast, colon and lung cancer. Thus, ITIH genes may represent a family of putative tumor suppressor genes that should be analyzed in greater detail in the future. For an initial detailed analysis we chose ITIH2 expression in human breast cancer. Loss of ITIH2 expression in 70% of cases (n = 50, CPA) could be confirmed by real-time PCR in an additional set of breast cancers (n = 36). Next we studied ITIH2 expression on the protein level by analyzing a comprehensive tissue micro array including 185 invasive breast cancer specimens. We found a strong correlation (p < 0.001) between ITIH2 expression and estrogen receptor (ER) expression indicating that ER may be involved in the regulation of this ECM molecule.

Conclusion

Altogether, this is the first systematic analysis on the differential expression of ITIH genes in human cancer, showing frequent downregulation that may be associated with initiation and/or progression of these malignancies.

Validation and characterization of human kallikrein 11 as a serum marker for diagnosis of ovarian carcinoma

PURPOSE

The serum tumor marker CA 125 is elevated in most clinically advanced ovarian carcinomas, and currently, one of the most promising early detection strategies for ovarian cancer uses CA 125 level in conjunction with imaging. However, CA 125 is elevated in only 50% of early-stage ovarian cancer and is often elevated in women with benign ovarian tumors and other gynecologic diseases. Additional markers may improve on its individual performance if they increase sensitivity and specificity and are less sensitive to other gynecologic conditions. The human kallikrein 11 (hK11) marker has been reported to have favorable predictive value for ovarian cancer, although, by itself, it may be inferior to CA 125.

EXPERIMENTAL DESIGN

We here validate the performance of hK11 on an independent data set and further characterize its behavior in multiple types of controls. We also investigate its behavior when combined with CA 125 to form a composite marker. hK11 had not previously been evaluated on these serum samples. CA 125, hK11, and the composite marker were evaluated for their performance in identifying ovarian cancer and for temporal stability.

RESULTS

hK11 significantly distinguished ovarian cancer cases from healthy controls and is less sensitive to benign ovarian disease than is CA 125.

CONCLUSION

We conclude that hK11 is a valuable new biomarker for ovarian cancer and its temporal stability implies that it may do even better when used in a longitudinal screening program for early detection.

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.

A consolidated catalogue and graphical annotation of dbSNP polymorphisms in the human tissue kallikrein (KLK) locus

The human tissue kallikreins, 15 secreted serine proteases, may play diverse roles in pathophysiology. The National Center for Biotechnology Information's dbSNP was mined for polymorphisms located within the kallikrein (KLK) locus using custom-designed "ParSNPs" and "LocusAnnotator" software tools. Using "ParSNPs", a filterable catalogue of 1856 KLK polymorphisms (1023 validated) was generated. "LocusAnnotator" was used to annotate the KLK locus sequence with gene and polymorphism features. A second locus was examined to validate the use of both programs on a non-kallikrein locus. This report may assist in the informed selection of KLK polymorphisms for future association and biochemical studies in relation to disease. Furthermore, "ParSNPs" and "LocusAnnotator" are available at no cost from our website (www.acdcLab.org/annotations) to examine other loci.

Construction and identification of human tissue kallikrein gene eukaryotic expressing vector

To clone and sequence the human tissue kallikrein gene of Chinese, and to construct eukaryotic expression recombinant of KK, total RNA was extracted from human pancreas and human tissue kallikrein gene cDNA was amplified by PCR after reverse-transcription by using Oligo(dT) primer. The original kallikrein cDNA was recovered and filled with Klenow enzyme and inserted into KS plasmid. After restriction endonuclease digestion, KK cDNA was sequenced by ABI377 analyzer. Then the KK gene was amplified from pBluescript KSKK and inserted into pcDNA3. A sequence comparison showed that the cloned kallikrein gene was only one nucleotide different from that reported in the Genbank. The coding amino acid was Asp in the Genbank gene, while the coding amino acid of Chinese kallikrein gene was Asn. The KK cDNA fragment was inserted into the eukaryotic expression vector pcDNA3. The cloned kallikrein gene and the pcDNA3KK can be used for further study in gene therapy.. .

The autolytic regulation of human kallikrein-related peptidase 6

Human kallikrein-related peptidase 6 (KLK6) is a member of the kallikrein family of serine-type proteases, characterized as an arginine-specific digestive-type protease capable of degrading a wide-variety of extracellular matrix proteins. KLK6 has been proposed to be a useful biomarker for breast and ovarian cancer prognosis, is abundantly expressed in the CNS and cerebrospinal fluid, and is intimately associated with regions of active inflammatory demyelination in multiple sclerosis (MS) lesions. Inhibition of KLK6 results in delayed onset and reduced severity of symptoms associated with experimental autoimmune encephalomyelitis, suggesting a key effector role for this protease in CNS inflammatory disease. KLK6 has been shown to autolytically cleave internally, leading to inactivation and suggesting a negative feedback inhibition control mechanism. Alternatively, the ability of KLK6 to self-activate has also been reported, suggesting a positive feedback activation loop control mechanism. Activation of pro-KLK6 requires hydrolysis after a Lys residue; however, KLK6 exhibits 2 order of magnitude reduced affinity for hydrolysis after Lys versus Arg residues; therefore, the ability to autolytically activate has been called into question. In the present study the catalytic activity of KLK6 toward its pro-sequence and internal autolytic sequence is characterized. The results show that the ability of KLK6 to activate pro-KLK6 is essentially negligible when compared to the rate of the internal autolytic inactivation or to the ability of other proteases to activate pro-KLK6. The results thus show that the primary autolytic regulatory mechanism of KLK6 is negative feedback inhibition, and activation is likely achieved through the action of a separate protease.

Transcriptional upregulation of human tissue kallikrein 6 in ovarian cancer: clinical and mechanistic aspects

The human tissue kallikrein family (KLK for protein; KLK for gene) includes 15 members. Twelve kallikreins, including KLK6, are concurrently upregulated in ovarian cancer. However, the mechanism of this phenomenon remains unclear. In this study, we measured KLK6 expression in a large series of ovarian tissue cytosols and examined possible mechanisms of KLK6 up-regulation in ovarian cancer. Using a newly developed enzyme-linked immunosorbent assay (ELISA) with two monoclonal antibodies, we quantified KLK6 expression in ovarian tissue cytosols, and confirmed the upregulation of KLK6 in ovarian cancer and its unfavourable prognostic value. We then examined KLK6 mRNA expression using reverse transcription-polymerase chain reaction and established its good concordance with KLK6 protein expression. This finding suggested that the KLK6 gene is under transcriptional regulation. We then scrutinised a few mechanisms that could explain KLK6 upregulation. The relative abundance of two KLK6 mRNA transcripts was studied; we found the same differential expression pattern in all samples, regardless of KLK6 levels. Genomic mutation screening of all exons and the 5'-flanking region of the KLK6 gene identified two linked single-nucleotide polymorphisms in the 5'-untranslated region, but neither correlated with KLK6 expression. Ovarian cell lines were separately treated with five steroid hormones. None of the treatments produced significant effects on KLK6 expression. We conclude that KLK6 is transcriptionally upregulated in ovarian cancer, but probably not through alternative mRNA transcript expression, genomic mutation, or steroid hormone induction.

Large-scale and high-confidence proteomic analysis of human seminal plasma

BACKGROUND

The development of mass spectrometric (MS) techniques now allows the investigation of very complex protein mixtures ranging from subcellular structures to tissues. Body fluids are also popular targets of proteomic analysis because of their potential for biomarker discovery. Seminal plasma has not yet received much attention from the proteomics community but its characterization could provide a future reference for virtually all studies involving human sperm. The fluid is essential for the survival of spermatozoa and their successful journey through the female reproductive tract.

RESULTS

Here we report the high-confidence identification of 923 proteins in seminal fluid from a single individual. Fourier transform MS enabled parts per million mass accuracy, and two consecutive stages of MS fragmentation allowed confident identification of proteins even by single peptides. Analysis with GoMiner annotated two-thirds of the seminal fluid proteome and revealed a large number of extracellular proteins including many proteases. Other proteins originated from male accessory glands and have important roles in spermatozoan survival.

CONCLUSION

This high-confidence characterization of seminal plasma content provides an inventory of proteins with potential roles in fertilization. When combined with quantitative proteomics methodologies, it should be useful for studies of fertilization, male infertility, and prostatic and testicular cancers.

Human kallikrein 8 protein is a favorable prognostic marker in ovarian cancer

Human kallikrein 8 (hK8/neuropsin/ovasin; encoded by KLK8) is a steroid hormone-regulated secreted serine protease differentially expressed in ovarian carcinoma. KLK8 mRNA levels are associated with a favorable patient prognosis and hK8 protein levels are elevated in the sera of 62% ovarian cancer patients, suggesting that KLK8/hK8 is a prospective biomarker. Given the above, the aim of the present study was to determine if tissue hK8 bears any prognostic significance in ovarian cancer. Using a newly developed ELISA, hK8 was quantified in 136 ovarian tumor extracts and correlated with clinicopathologic variables and outcome [progression-free survival (PFS); overall survival (OS)] over a median follow-up period of 42 months. hK8 levels in ovarian tumor cytosols ranged from 0 to 478 ng/mg total protein, with a median of 30 ng/mg. An optimal cutoff value of 25.8 ng/mg total protein (74th percentile) was selected based on the ability of hK8 values to predict the PFS of the study population and to categorize tumors as hK8 positive or negative. Women with hK8-positive tumors most often had lower-grade tumors (G1), no residual tumor after surgery, and optimal debulking success (P < 0.05). Univariate and multivariate analyses revealed that patients with hK8-positive tumors had a significantly longer PFS and OS than hK8-negative patients (P < 0.05). Kaplan-Meier survival curves further confirmed a reduced risk of relapse and death in women with hK8-positive tumors (P = 0.001 and P = 0.014, respectively). These results indicate that hK8 is an independent marker of favorable prognosis in ovarian cancer.

Expression of human Kallikrein 14 (KLK14) in breast cancer is associated with higher tumour grades and positive nodal status

Human kallikrein 14 (KLK14) is a steroid hormone-regulated member of the tissue kallikrein family of serine proteases, for which a prognostic and diagnostic value in breast cancer has been suggested. To further characterise the value of KLK14 as a breast tumour marker, we have carefully analysed KLK14 expression in normal breast tissue and breast cancer both on the RNA level by real-time RT-PCR (n=39), and on the protein level (n=127) using a KLK14-specific antibody for immunohistochemistry. We correlated KLK14 protein expression data with available clinico-pathological parameters (mean follow-up time was 55 months) including patient prognosis. KLK14 RNA expression as quantified by real-time RT-PCR was significantly more abundant in breast tumours compared to normal breast tissue (P=0.027), an issue that had not been clarified recently. Concordantly with the RNA data, cytoplasmic KLK14 protein expression was significantly higher in invasive breast carcinomas compared to normal breast tissues (P=0.003). Furthermore, KLK14 protein expression was associated with higher tumour grade (P=0.041) and positive nodal status (P=0.045) but was not significantly associated with shortened disease-free or overall patient survival time in univariate analyses. We conclude that KLK14 is clearly overexpressed in breast cancer in comparison to normal breast tissues and is positively associated with conventional parameters of tumour aggressiveness, but due to a missing association with survival times, the use of KLK14 immunohistochemistry as a prognostic marker in breast cancer is questionable.

Clinicopathologic and biological significance of kallikrein 6 overexpression in human gastric cancer

PURPOSE

Human kallikrein genes (KLK) have been reported to be involved in human malignancies and several KLKs are promising biomarkers of prostate, ovarian, testicular, and breast cancers. Herein, we investigated the clinicopathologic and biological significance of KLK6 gene expression in human gastric cancer.

PATIENTS AND METHODS

Using real-time reverse transcription-PCR, we analyzed the KLK6 expression status with respect to various clinicopathologic variables in 66 patients with gastric cancer. In addition, we established a KLK6 stably suppressed gastric cancer cell line (MKN28) using small interfering RNA-mediated gene silencing, and investigated its effects on the cell proliferation rate, cell cycle, and invasiveness.

RESULTS

The KLK6 gene expression in cancerous tissue (0.37 +/- 0.53) was significantly (P < 0.000001) higher than that in noncancerous tissue (0.026 +/- 0.060). Elevated KLK6 expression was significantly associated with lymphatic invasion (P = 0.03). Furthermore, patients with a high KLK6 expression had a significantly poorer survival rate than those with a low KLK6 expression (P = 0.03). Therefore, we showed that KLK6 gene silencing with KLK6 small interfering RNA effectively suppressed the cell proliferation rate (P = 0.002), cell population in the S phase (P < 0.01), and invasiveness (P < 0.01) in comparison to mock-transfected cells.

CONCLUSIONS

The KLK6 gene is markedly overexpressed in gastric cancer tissue and its expression status may be a powerful prognostic indicator for patients with gastric cancer. Our findings also suggest that KLK6 may possibly be a novel target for gastric cancer therapy by gene-silencing procedures.

Purification and Characterization of Human Kallikrein 11, a Candidate Prostate and Ovarian Cancer Biomarker, from Seminal Plasma

PURPOSE

Preliminary data suggest that hK11 is a novel serum biomarker for prostate and ovarian cancer. To examine the enzymatic characteristics of hK11, we purified and functionally characterized native hK11 from seminal plasma.

EXPERIMENTAL DESIGN

hK11 was purified from seminal plasma by immunoaffinity chromatography and characterized by kinetic analysis, electrophoresis, Western blots, and mass spectrometry.

RESULTS

hK11 is present in seminal plasma at concentrations ranging from 2 to 37 microg/mL. Using immunoaffinity chromatography and reverse-phase high-performance liquid chromatography, we purified hK11 to homogeneity. In seminal plasma, hK11 is present as a free enzyme of approximately 40 kDa. About 40% of hK11 is enzymatically active, whereas the rest is inactivated by internal cleavage after Arg156 (Genbank accession no. AF164623), which generates two peptides of approximately 20 kDa, connected by internal disulfide bonds. Purified hK11 possesses trypsin-like activity and cleaves synthetic peptides after arginine but not lysine residues. It does not cleave chymotrypsin substrates. Antithrombin, alpha1-antichymotrypsin, alpha2-antiplasmin, and alpha1-antitrypsin have no effect on hK11 activity and do not form complexes with hK11 in vitro. The strongest inhibitor, APMSF, completely inhibited hK11 activity at a concentration of 2.5 mmol/L. Aprotinin and an hK11-specific monoclonal antibody inhibited hK11 activity up to 40%. Plasmin is a strong candidate for cleaving hK11 at Arg156.

CONCLUSION

This is the first report on purification and characterization of native hK11. We speculate that hK11, along with other kallikreins, proteases, and inhibitors, participates in a cascade enzymatic pathway responsible for semen liquefaction after ejaculation.

Androgen Receptor and Prostate-Specific Antigen Gene Polymorphisms and Breast Cancer in African-American Women

Several previous studies have found the CAG repeat polymorphism in exon 1 of the androgen receptor (AR) gene to be associated with breast cancer risk among some groups of Caucasian and Asian women. In a population-based case-control study of 488 African-American women (239 cases and 249 controls), we examined this polymorphism along with a polymorphism (-158 G/A) in an androgen-regulated gene (PSA) whose expression has been correlated with breast cancer prognosis. Overall, we did not observe any significant association between the CAG repeat polymorphism and breast cancer risk. However, among women with a first-degree family history of breast cancer, longer CAG repeats were associated with a significantly increased risk. Women carrying at least one longer allele [(CAG)n > or = 22] had a 3-fold increased risk compared to those with two shorter alleles (odds ratio, 3.18; 95% confidence interval, 1.08-9.36). There was no significant association between the PSA gene polymorphism and breast cancer risk, nor was there significant gene-gene interaction. In summary, our results further support that shorter CAG repeats (stronger AR transactivation activity) may reduce the risk of breast cancer, at least among some groups of women. Our data, however, are unable to provide evidence that PSA is the pathway through which the protective effect of androgens operates.

Clinical significance of human kallikrein gene 6 messenger RNA expression in colorectal cancer

PURPOSE

Human kallikrein gene 6 (KLK6) is a member of the human kallikrein gene family, and recent studies have found that many kallikreins have altered expression patterns in various malignancies. The purpose of the current study was to quantify the expression of KLK6 in malignant and benign colorectal tissues and to statistically analyze whether KLK6 expression levels correlate with clinicopathologic variables and prognosis in patients with colorectal cancer.

EXPERIMENTAL DESIGNS

Paired colorectal tissue samples from cancerous and corresponding noncancerous tissues were obtained from 63 patients with colorectal cancer who underwent surgical resection. Quantitative analyses of KLK6 mRNA expression were done using real-time quantitative reverse transcription-PCR.

RESULTS

KLK6 mRNA overexpression in cancerous tissues compared with normal counterparts was observed in 57 of 63 (90%) patients. The mean expression level of KLK6 mRNA in cancerous tissues was significantly higher than that in noncancerous tissues (P < 0.0001). Elevated KLK6 expression was significantly correlated with serosal invasion (P < 0.05), liver metastasis (P < 0.05), and advanced Duke's stage (P < 0.01). Furthermore, patients with high KLK6 expression had a significantly poorer actuarial overall survival than patients with low KLK6 expression (5-year overall survival rates: 54% and 73%, respectively, P < 0.05).

CONCLUSIONS

The results of this study indicated that KLK6 mRNA expression was significantly higher in cancerous than in noncancerous colorectal tissues, and high expression of KLK6 mRNA correlated with serosal invasion, liver metastasis, advanced Duke's stage, and a poor prognosis for patients with colorectal cancer.

Human kallikrein 6: a new potential serum biomarker for uterine serous papillary cancer

PURPOSE

The discovery of novel biomarkers might greatly contribute to improve clinical management and outcomes in uterine serous papillary carcinoma (USPC), a highly aggressive variant of endometrial cancer.

EXPERIMENTAL DESIGN

Human kallikrein 6 (hK6) gene expression levels were evaluated in 29 snap-frozen endometrial biopsies, including 13 USPC, 13 endometrioid carcinomas, and 3 normal endometrial cells by real-time PCR. Secretion of hK6 protein by 14 tumor cultures, including 3 USPC, 3 endometrioid carcinoma, 5 ovarian serous papillary carcinoma, and 3 cervical cancers, was measured using a sensitive ELISA. Finally, hK6 concentration in 79 serum and plasma samples from 22 healthy women, 20 women with benign diseases, 20 women with endometrioid carcinoma, and 17 USPC patients was studied.

RESULTS

hK6 gene expression levels were significantly higher in USPC when compared with endometrioid carcinoma (mean copy number by real-time PCR, 1,927 versus 239, USPC versus endometrioid carcinoma; P < 0.01). In vitro hK6 secretion was detected in all primary USPC cell lines tested (mean, 11.5 microg/L) and the secretion levels were similar to those found in primary ovarian serous papillary carcinoma cultures (mean, 9.6 microg/L). In contrast, no hK6 secretion was detectable in primary endometrioid carcinoma and cervical cancer cultures. hK6 serum and plasma concentrations (mean +/- SE) among normal healthy females (2.7 +/- 0.2 microg/L), patients with benign diseases (2.4 +/- 0.2 microg/L), and patients with endometrioid carcinoma (2.6 +/- 0.2 microg/L) were not significantly different. In contrast, serum and plasma hK6 values in USPC patients (6.1 +/- 1.1) were significantly higher than those in the noncancer group (P = 0.006), benign group (P = 0.003), and endometrioid carcinoma patients (P = 0.005).

CONCLUSIONS

hK6 is highly expressed in USPC and is released in the plasma and serum of USPC patients. hK6 may represent a novel biomarker for USPC for monitoring early disease recurrence and response to therapy.

High-resolution functional proteomics by active-site peptide profiling

Characterization and functional annotation of the large number of proteins predicted from genome sequencing projects poses a major scientific challenge. Whereas several proteomics techniques have been developed to quantify the abundance of proteins, these methods provide little information regarding protein function. Here, we present a gel-free platform that permits ultrasensitive, quantitative, and high-resolution analyses of protein activities in proteomes, including highly problematic samples such as undiluted plasma. We demonstrate the value of this platform for the discovery of both disease-related enzyme activities and specific inhibitors that target these proteins.

Increased circulating levels of tissue kallikrein in systemic sclerosis correlate with microvascular involvement

BACKGROUND

In systemic sclerosis (SSc) the lack of an angiogenic response to hypoxia may be due to inappropriate synthesis of angiogenic and angiostatic factors. Tissue kallikrein (t-kallikrein), regulating the kallikrein-kinin system and acting on the microcirculation, is a potent angiogenic agent, and kallistatin is its natural inhibitor.

OBJECTIVE

To evaluate, in patients with SSc, t-kallikrein and kallistatin levels and their correlation with clinical features and measures of microvascular involvement.

PATIENTS AND METHODS

Serum levels of t-kallikrein and kallistatin (ELISA) and t-kallikrein skin expression (immunohistochemistry) were studied in patients with SSc, and evaluated for subset (dSSc or lSSc), clinical and immunological features, and microvascular involvement (ulcers, telangiectasias, nailfold videocapillaroscopy).

RESULTS

Circulating levels of t-kallikrein were higher in SSc than in controls (p<0.001). T-kallikrein did not differ between lSSc and dSSc, although it was higher in lSSc than in controls (p<0.001).T-kallikrein levels were higher in patients with early and active capillaroscopic pattern than in those with late pattern (p = 0.019 and 0.023). Patients with giant capillaries and capillary microhaemorrhages had higher t-kallikrein concentrations than patients with architectural derangement (p = 0.04). No differences in kallistatin levels were detected between patients with SSc and controls, or between lSSc and dSSc. In early SSc skin, the presence of t-kallikrein was found in endothelial and in perivascular inflammatory cells, while no staining in skin of advanced SSc was detected.

CONCLUSION

T-kallikrein levels are increased in patients with SSc, particularly in lSSc, and are associated with early and active capillaroscopic patterns. T-kallikrein may play a part in SSc microvascular changes.

Human kallikrein gene 11 (KLK11) mRNA overexpression is associated with poor prognosis in patients with epithelial ovarian cancer

PURPOSE

The purpose of this study was to examine expression levels of the human tissue kallikrein 11 gene (KLK11) in epithelial ovarian tumors and to identify the relationship between KLK11 expression and patient survival.

EXPERIMENTAL DESIGN

KLK11 mRNA expression was examined by semiquantitative PCR in 64 epithelial ovarian tumors (7 adenomas, 6 low malignant potential tumors, and 51 adenocarcinomas) and in 10 normal ovaries. Semiquantitative PCR results were correlated with clinicopathologic variables and overall survival. cDNA from human normal tissues and tumor tissues was also analyzed.

RESULTS

KLK11 mRNA expression was detected in various human cancer tissues including breast, lung, colon, prostate, pancreas, and ovarian carcinoma. The mean value of relative KLK11 expression ratio was significantly higher in ovarian tumor samples than in normal ovary samples (compared with normal samples: adenoma, P = 0.0006; low malignant potential tumor, P = 0.0049; and carcinoma, P < 0.0001). No statistically significant associations between KLK11 mRNA expression level and clinical stage, histological type, or histological grade were observed. The log-rank test showed that high KLK11 mRNA expression and advanced clinical stage significantly correlated with poor patient survival (P = 0.0185 and P = 0.0043, respectively). High KLK11 mRNA expression and clinical stage remained significantly associated with overall survival (P = 0.0225 and P = 0.0202, respectively) after multivariate analysis.

CONCLUSIONS

KLK11 expression may play an important role in ovarian cancer development and act as an independent prognostic marker in ovarian cancer patients.

Three biomarkers identified from serum proteomic analysis for the detection of early stage ovarian cancer

Early detection remains the most promising approach to improve long-term survival of patients with ovarian cancer. In a five-center case-control study, serum proteomic expressions were analyzed on 153 patients with invasive epithelial ovarian cancer, 42 with other ovarian cancers, 166 with benign pelvic masses, and 142 healthy women. Data from patients with early stage ovarian cancer and healthy women at two centers were analyzed independently and the results cross-validated to discover potential biomarkers. The results were validated using the samples from two of the remaining centers. After protein identification, biomarkers for which an immunoassay was available were tested on samples from the fifth center, which included 41 healthy women, 41 patients with ovarian cancer, and 20 each with breast, colon, and prostate cancers. Three biomarkers were identified as follows: (a) apolipoprotein A1 (down-regulated in cancer); (b) a truncated form of transthyretin (down-regulated); and (c) a cleavage fragment of inter-alpha-trypsin inhibitor heavy chain H4 (up-regulated). In independent validation to detect early stage invasive epithelial ovarian cancer from healthy controls, the sensitivity of a multivariate model combining the three biomarkers and CA125 [74% (95% CI, 52-90%)] was higher than that of CA125 alone [65% (95% CI, 43-84%)] at a matched specificity of 97% (95% CI, 89-100%). When compared at a fixed sensitivity of 83% (95% CI, 61-95%), the specificity of the model [94% (95% CI, 85-98%)] was significantly better than that of CA125 alone [52% (95% CI, 39-65%)]. These biomarkers demonstrated the potential to improve the detection of early stage ovarian cancer.

Characterisation of human kallikrein 6/protease M expression in ovarian cancer

Kallikrein 6 (hK6, also known as protease M/zyme/neurosin) is a member of the human kallikrein gene family. We have previously cloned the cDNA for this gene by differential display and shown the overexpression of the mRNA in breast and ovarian primary tumour tissues and cell lines. To thoroughly characterise the expression of this kallikrein in ovarian cancer, we have developed a novel monoclonal antibody specific to hK6 and employed it in immunohistochemistry with a wide range of ovarian tumour samples. The expression was found elevated in 67 of 80 cases of ovarian tumour samples and there was a significant difference in the expression levels between normal and benign ovarian tissues and the borderline and invasive tumours (P<0.001). There was no difference of expression level between different subtypes of tumours. More significantly, high level of kallikrein 6 expression was found in many early-stage and low-grade tumours, and elevated hK6 proteins were found in benign epithelia coexisting with borderline and invasive tissues, suggesting that overexpression of hK6 is an early phenomenon in the development of ovarian cancer. Quantitative real-time reverse transcription–polymerase chain reactions also showed elevated kallikrein 6 mRNA expression in ovarian tumours. Genomic Southern analysis of 19 ovarian tumour samples suggested that gene amplification is one mechanism for the overexpression of hK6 in ovarian cancer.

Early detection and prognosis of ovarian cancer using serum YKL-40

PURPOSE

YKL-40 is a secreted glycoprotein (chitinase family). We compared YKL-40 with two ovarian cancer serum markers, CA125 and CA15-3, for the detection of early-stage ovarian cancer.

MATERIALS AND METHODS

Serum YKL-40 levels were assayed by enzyme-linked immunosorbent assay for 46 healthy subjects, 61 high-risk individuals, 33 patients with benign gynecologic processes, and 50 preoperative patients subsequently diagnosed with predominantly early-stage ovarian cancer. Serum CA125 and CA15-3 values were obtained.

RESULTS

Median YKL-40 level was 28 ng/mL (range, 15 to 166 ng/mL) for healthy subjects, 36 ng/mL (range, 9 to 69 ng/mL) for high-risk individuals without prior cancer, 44.5 ng/mL (range, 5 to 133 ng/mL) for high-risk patients with prior breast cancer, and 38 ng/mL (range, 5 to 67 ng/mL) for individuals with benign gynecologic processes (P = NS). Median preoperative YKL-40 level for ovarian cancer patients was 94 ng/mL (range, 17 to 517 ng/mL; P <.0001 compared with normal and high-risk). YKL-40 was elevated (>/= 62 ng/mL) in 36 (72%) of 50 patients compared with 23 (46%) of 50 and 13 (26%) of 50 patients for CA125 and CA15-3 (P <.008). Twenty (65%) of 31 early-stage patients had elevated serum YKL-40 levels compared with 11 (35%) of 31 and four (13%) of 31 patients for CA125 and CA15-3 (P =.039). YKL-40 levels increased with stage (P <.005), regardless of grade, histology, or patient age. Patients with early-stage tumors with YKL-40 values more than 80 ng/mL had a worse prognosis (71% recurrence v no recurrence [P =.034]).

CONCLUSION

YKL-40 may represent a novel marker for the detection of early-stage ovarian cancer. YKL-40 levels in early-stage patients may also predict disease recurrence and survival. The utility of YKL-40 in detection of early-stage ovarian cancer deserves further investigation.

Human Tissue Kallikreins: Physiologic Roles and Applications in Cancer

Tissue kallikreins are members of the S1 family (clan SA) of trypsin-like serine proteases and are present in at least six mammalian orders. In humans, tissue kallikreins (hK) are encoded by 15 structurally similar, steroid hormone–regulated genes (KLK) that colocalize to chromosome 19q13.4, representing the largest cluster of contiguous protease genes in the entire genome. hKs are widely expressed in diverse tissues and implicated in a range of normal physiologic functions from the regulation of blood pressure and electrolyte balance to tissue remodeling, prohormone processing, neural plasticity, and skin desquamation. Several lines of evidence suggest that hKs may be involved in cascade reactions and that cross-talk may exist with proteases of other catalytic classes. The proteolytic activity of hKs is regulated in several ways including zymogen activation, endogenous inhibitors, such as serpins, and via internal (auto)cleavage leading to inactivation. Dysregulated hK expression is associated with multiple diseases, primarily cancer. As a consequence, many kallikreins, in addition to hK3/PSA, have been identified as promising diagnostic and/or prognostic biomarkers for several cancer types, including ovarian, breast, and prostate. Recent data also suggest that hKs may be causally involved in carcinogenesis, particularly in tumor metastasis and invasion, and, thus, may represent attractive drug targets to consider for therapeutic intervention.

A genomic analysis of rat proteases and protease inhibitors

Proteases perform important roles in multiple biological and pathological processes. The availability of the rat genome sequence has facilitated the analysis of the complete protease repertoire or degradome of this model organism. The rat degradome consists of at least 626 proteases and homologs, which are distributed into 24 aspartic, 160 cysteine, 192 metallo, 221 serine, and 29 threonine proteases. This distribution is similar to that of the mouse degradome but is more complex than that of the human degradome composed of 561 proteases and homologs. This increased complexity of rat proteases mainly derives from the expansion of several families, including placental cathepsins, testases, kallikreins, and hematopoietic serine proteases, involved in reproductive or immunological functions. These protease families have also evolved differently in rat and mouse and may contribute to explain some functional differences between these closely related species. Likewise, genomic analysis of rat protease inhibitors has shown some differences with mouse protease inhibitors and the expansion of families of cysteine and serine protease inhibitors in rodents with respect to human. These comparative analyses may provide new views on the functional diversity of proteases and inhibitors and contribute to the development of innovative strategies for treating proteolysis diseases.

Human kallikrein 13 protein in ovarian cancer cytosols: a new favorable prognostic marker

PURPOSE

Human kallikrein 13 (hK13; encoded by the KLK13 gene) is a secreted serine protease expressed in endocrine tissues, including the prostate, testis, breast, and ovary. We have previously reported steroid hormone regulation of the KLK13 gene and its clinical value as a marker of favorable prognosis in breast cancer at the mRNA level. We hypothesized that hK13 may represent a potential biomarker for ovarian carcinomas.

PATIENTS AND METHODS

Using a newly developed enzyme-linked immunosorbent assay (ELISA), hK13 levels were quantified in 131 ovarian tumor extracts and correlated with various clinicopathological variables and outcome (progression-free survival [PFS], overall survival [OS]), over a median follow-up period of 42 months.

RESULTS

hK13 concentration in ovarian tumor cytosols ranged from 0 to 18.4 ng/mg of total protein. An optimal cutoff value of 0.13 ng/mg (67(th) percentile) was selected, based on the ability of hK13 values to predict the PFS of the study population, to categorize tumors as hK13-positive or negative. Women with hK13-positive tumors most often had early stage (stage I/II) disease, no residual tumor after surgery and optimal debulking success (P <.05). Univariate and multivariate Cox regression analyses revealed that patients with hK13-positive tumors had a significantly longer PFS and OS than hK13-negative patients (P <.05). Kaplan-Meier survival curves further confirmed a reduced risk of relapse and death in women with hK13-positive tumors (P =.007 and P =.002, respectively).

CONCLUSION

These results indicate that hK13 is an independent marker of favorable prognosis in ovarian cancer.

Kallikrein gene downregulation in breast cancer

Recent evidence suggests that many members of the human kallikrein gene family are differentially regulated in breast cancer and other endocrine-related malignancies. In this study, we utilised the serial analysis of gene expression (SAGE) and expressed sequence tag (EST) databases of the Cancer Genome Anatomy Project (CGAP) to perform in silico analyses of the expression pattern of the 15 human kallikrein genes in normal and cancerous breast tissues and cell lines using different analytical tools such as Virtual Northern blotting, Digital Differential Display and X-profiler. Our results indicate that at least four kallikrein genes (KLK5, 6, 8, 10) are downregulated in breast cancer. Probing eight normal and 24 breast cancer SAGE libraries with gene-specific tags for each of the above kallikreins indicated moderate-to-high expression densities in normal breast (27–319 tags per million; tpm, in two to five out of eight libraries), compared to no or low expression (0 – 34 tpm in zero to two libraries out of 24) in breast cancer. These data were verified by screening the EST databases, where all mRNA clones isolated for these genes, except for one in each, were from normal breast libraries, with no clones detected from breast cancer tissues or cell lines (with the exception of KLK8). X-profiler comparison of two pools of normal and breast cancer libraries further verified the presence of significant downregulation of expression levels of 4 of the kallikreins genes (KLK5, 6, 10, 12). We experimentally verified the downregulation of these four kallikreins (KLK5, 6, 8, 10 and 12) by RT – PCR analysis.

Prognostic value of the human kallikrein gene 15 expression in ovarian cancer

PURPOSE

KLK15 is a newly cloned human kallikrein gene. Many kallikreins were found to be differentially expressed in ovarian cancer. Like other kallikreins, KLK15 is regulated by steroid hormones in cancer cell lines. KLK15 is upregulated mainly by androgens and to a lesser extent by progestins. The purpose of this study was to examine the prognostic value of KLK15 in ovarian cancer tissues.

MATERIALS AND METHODS

We studied KLK15 expression by quantitative reverse transcriptase polymerase chain reaction (RT-PCR) in 168 consecutive patients with epithelial ovarian cancer. Ten patients with benign ovarian tumors were also included in the study. An optimal cutoff point equal to the 50th percentile was defined based on the ability of KLK15 to predict progression-free survival and overall survival of the study population.

RESULTS

KLK15 expression levels were significantly higher in cancerous tissues compared with benign tumors. Kaplan-Meier survival curves showed that KLK15 overexpression is a significant predictor of reduced progression-free survival (PFS; P <.001) and overall survival (OS; P <.009). Univariate and multivariate analyses indicate that KLK15 is an independent prognostic factor for PFS and OS. A weak positive correlation was found between KLK15 expression and serum CA-125 levels.

CONCLUSION

KLK15 expression, as assessed by quantitative RT-PCR, is an independent marker of unfavorable prognosis for ovarian cancer.

Human kallikrein 6 (hK6): a new potential serum biomarker for diagnosis and prognosis of ovarian carcinoma

PURPOSE

The discovery of new ovarian cancer biomarkers that are suitable for early disease diagnosis and prognosis may ultimately lead to improved patient management and outcomes.

PATIENTS AND METHODS

We measured, by immunoassay, human kallikrein 6 (hK6) concentration in serum of 97 apparently healthy women, 141 women with benign abdominal diseases, and 146 women with histologically proven primary ovarian carcinoma. We then calculated the diagnostic sensitivity and specificity of this test and examined the association of serum hK6 concentration with various clinicopathologic variables and patient survival.

RESULTS

Serum hK6 concentration between normal and benign disease patients was not different (mean, 2.9 and 3.1 micro g/L, respectively). However, hK6 in presurgical serum of ovarian cancer patients was highly elevated (mean, 6.8 micro g/L; P <.001). Serum hK6 decreased after surgery (to a mean of 3.9 micro g/L) in 68% of patients. The diagnostic sensitivity of serum hK6 at 90% and 95% specificity is 52% and 47%, respectively, in the whole patient population. For early stage disease (stage I or II), sensitivity is approximately 21% to 26%. When combined with CA-125, at 90% specificity, sensitivity increases to 72% (for all patients) and to 42% in stage I or II disease. Serum hK6 concentration correlates moderately with CA-125 and is higher in patients with late-stage, higher-grade disease and in patients with serous histotype. Preoperative serum hK6 concentration is a powerful predictor of disease-free and overall survival in both univariate and multivariate analyses.

CONCLUSIONS

Serum hK6 concentration seems to be a new biomarker for ovarian carcinoma and may have value for disease diagnosis and prognosis.

Biology of prostate-specific antigen

Prostate-specific antigen (PSA) is an androgen-regulated serine protease produced by both prostate epithelial cells and prostate cancer (PCa) and is the most commonly used serum marker for cancer. It is a member of the tissue kallikrein family, some of the members of which are also prostate specific. PSA is a major protein in semen, where its function is to cleave semenogelins in the seminal coagulum. PSA is secreted into prostatic ducts as an inactive 244-amino acid proenzyme (proPSA) that is activated by cleavage of seven N-terminal amino acids. PSA that enters the circulation intact is rapidly bound by protease inhibitors, primarily alpha1-antichymotrypsin, although a fraction is inactivated in the lumen by proteolysis and circulates as free PSA. This proteolytic inactivation, as well as the cleavage of proPSA to PSA, is less efficient in PCa. Serum total PSA levels are increased in PCa, and PSA screening has dramatically altered PCa presentation and management. Unfortunately, although high PSA levels are predictive of advanced PCa, a large fraction of organ-confined cancers present with much lower total PSA values that overlap those levels found in men without PCa. Measurement of free versus total PSA can increase specificity for PCa, and tests under development to measure forms of proPSA may further enhance the ability to detect early-stage PCa. PSA is also widely used to monitor responses to therapy and is under investigation as a therapeutic target. Finally, recent data indicate that there may be additional roles for PSA in the pathogenesis of PCa.

The androgen-regulated gene human kallikrein 15 (KLK15) is an independent and favourable prognostic marker for breast cancer

Many kallikrein genes were found to be differentially expressed in various malignancies, and prostate specific antigen (encoded by the KLK3 gene) is the best tumour marker for prostate cancer. Prostate specific antigen has recently been shown to be an independent favourable prognostic marker for breast cancer. KLK15 is newly discovered kallikrein gene that is located adjacent to KLK3 on chromosome 19q13.4. KLK15 has 41% similarity to KLK3 and the encoded protein, hK15, can activate pro-prostate specific antigen. We studied the expression of KLK15 by real-time quantitative reverse transcriptase-polymerase chain reaction in 202 tissues from patients with breast carcinoma of various stages, grades and histological types. KLK15 expression was found to be a significant predictor of progression-free survival (hazard ratio of 0.41 and P=0.011) and overall survival (hazard ratio of 0.34 and P=0.009). When all other known confounders were controlled in the multivariate analysis, KLK15 retained its prognostic significance. Higher concentrations of KLK15 mRNA were found more frequently in node negative patients (P=0.042). No association was found between KLK15 expression and any other clinicopathological variable. Further, KLK15 is an independent prognostic factor of progression-free survival and overall survival in the subgroup of patients with lower grade and those with oestrogen receptor and progesterone receptor negative tumours in both univariate and multivariate analysis. KLK15 levels of expression were slightly higher (although not statistically significant) in the oestrogen receptor negative and progesterone receptor negative subgroups of patients. KLK15 is up-regulated by androgens in breast cancer cell lines. Time-course and blocking experiments suggest that this regulation is mediated through the androgen receptor.

Quantitative analysis of human kallikrein gene 14 expression in breast tumours indicates association with poor prognosis

KLK14 (formerly known as KLK-L6) is a recently identified member of the human kallikrein gene family. This family harbours several genes aberrantly expressed in various cancers as well as established (PSA/hK3, hK2) and potential (hK6, hK10) cancer markers. Similar to other kallikrein genes, KLK14 was found to be regulated by steroid hormones, particularly androgens and progestins, in breast and ovarian cancer cell lines. Preliminary studies indicated that KLK14 is differentially expressed in breast, ovarian, prostatic and testicular tumours. Given the above, we determined the prognostic significance of KLK14 expression in breast cancer. We studied KLK14 expression in 178 histologically confirmed epithelial breast carcinomas by quantitative reverse transcription-polymerase chain reaction and correlated with clinicopathological variables (tumour stage, grade, histotype etc.) and with outcome (disease-free survival and overall survival), monitored over a median of 76 months. KLK14 mRNA levels ranged from 0 to 1,219 arbitrary units in breast cancer tissues, with a mean+/-s.e. of 136+/-22. An optimal cutoff value of 40.5 arbitrary units was selected, to categorise tumours as KLK14-positive or negative. Higher concentrations of KLK14 mRNA were more frequently found in patients with advanced stage (III) disease (P=0.032). No statistically significant association was found between KLK14 and the other clinicopathological variables. KLK14 overexpression was found to be a significant predictor of decreased disease-free survival (hazard ratio of 2.31, P=0.001) and overall survival (hazard ratio of 2.21, P=0.005). Cox multivariate analysis indicated that KLK14 was an independent prognostic indicator of disease-free survival and overall survival. KLK14 also has independent prognostic value in subgroups of patients with a tumour size </=2 cm and positive nodal, oestrogen receptor and progestin receptor status. We conclude that KLK14 expression, as assessed by quantitative reverse transcription-polymerase chain reaction, is an independent marker of unfavourable prognosis for breast cancer.