Human kallikrein 10 expression in normal tissues by immunohistochemistry

Kallikrein-related peptidases 6 and 10 are elevated in cerebrospinal fluid of patients with Alzheimer's disease and associated with CSF-TAU and FDG-PET

Background

Alterations in the expression of human kallikrein-related peptidases (KLKs) have been described in patients with Alzheimer’s disease (AD). We elucidated the suitability of KLK6, KLK8 and KLK10 to distinguish AD from NC and explored associations with established AD biomarkers.

Methods

KLK levels in cerebrospinal fluid (CSF), as determined by ELISA, were compared between 32 AD patients stratified to A/T/(N) system with evidence for amyloid pathology and of 23 normal controls with normal AD biomarkers. Associations between KLK levels and clinical severity, CSF and positron emission tomography (PET) based AD biomarkers were tested for.

Results

Levels of KLK6 and KLK10 were significantly increased in AD. KLK6 differed significantly between AD A+/T+/N+ and AD A+/T−/N+ or NC with an AUC of 0.922. CSF pTau and tTau levels were significantly associated with KLK6 in AD.

Conclusions

KLK6 deserves further investigations as a potential biomarker of Tau pathology in AD.

Electronic supplementary material

The online version of this article (10.1186/s40035-019-0168-6) contains supplementary material, which is available to authorized users.

Mining human cancer datasets for kallikrein expression in cancer: the 'KLK-CANMAP' Shiny web tool

The dysregulation of the serine-protease family kallikreins (KLKs), comprising 15 genes, has been reportedly associated with cancer. Their expression in several tissues and physiological fluids makes them potential candidates as biomarkers and therapeutic targets. There are several databases available to mine gene expression in cancer, which often include clinical and pathological data. However, these platforms present some limitations when comparing a specific set of genes and can generate considerable unwanted data. Here, several datasets that showed significant differential expression (p<0.01) in cancer vs. normal (n=118), metastasis vs. primary (n=15) and association with cancer survival (n=21) have been compiled in a user-friendly format from two open and/or publicly available databases Oncomine and OncoLnc for the 15 KLKs. The data have been included in a free web application tool: the KLK-CANMAP https://cancerbioinformatics.shinyapps.io/klk-canmap/. This tool integrates, analyses and visualises data and it was developed with the R Shiny framework. Using KLK-CANMAP box-plots, heatmaps and Kaplan-Meier graphs can be generated for the KLKs of interest. We believe this new cancer KLK focused web tool will benefit the KLK community by narrowing the data visualisation to only the genes of interest.

Clinical utility of kallikrein-related peptidases (KLK) in urogenital malignancies

Kallikrein-related peptidases (KLK), which represent a major tissue-associated proteolytic system, stand for a rich source of biomarkers that may allow molecular classification, early diagnosis and prognosis of human malignancies as well as prediction of response or failure to cancer-directed drugs. International research points to an important role of certain KLKs in female and male urogenital tract malignancies, in addition to cancers of the lung, brain, skin, head and neck, and the gastrointestinal tract. Regarding the female/male urogenital tract, remarkably, all of the KLKs are expressed in the normal prostate, testis, and kidney whereas the uterus, the ovary, and the urinary bladder are expressing a limited number of KLKs only. Most of the information regarding KLK expression in tumour-affected organs is available for ovarian cancer; all of the 12 KLKs tested so far were found to be elevated in the malignant state, depicting them as valuable biomarkers to distinguish between the normal and the cancerous phenotype. In contrast, for kidney cancer, a series of KLKs was found to be downregulated, while other KLKs were not expressed. Evidently, depending on the type of cancer or cancer stage, individual KLKs may show characteristics of a Janus-faced behaviour, by either expanding or inhibiting cancer progression and metastasis.

Clinical relevance of kallikrein-related peptidase 9, 10, 11, and 15 mRNA expression in advanced high-grade serous ovarian cancer

KLK9, 10, 11, and 15 may represent potential cancer biomarkers for evaluating ovarian cancer prognosis. In the present study, we selected a homogeneous cohort including 139 patients of advanced high-grade serous ovarian cancer (FIGO stage III/IV) and assessed the mRNA levels of KLK9, 10, 11, and 15 in tumor tissue by quantitative PCR. No significant associations of KLK9, 10, 11, and 15 mRNA with established clinical parameters (residual tumor mass, ascitic fluid volume) were found. Pronounced correlations between KLK10/KLK11 (rs = 0.647) and between KLK9/KLK15 (rs = 0.716) mRNA, but not between other combinations, indicate coordinate expression of distinct pairs of peptidases. In univariate Cox regression analysis, elevated KLK11 mRNA levels were significantly linked with prolonged overall survival (OS; p = 0.021) and progression-free survival (PFS; p = 0.008). KLK15 mRNA levels showed a trend towards significance in case of OS (p = 0.06); KLK9 and KLK10 mRNA expression levels were not associated with patients' outcome. In multivariable Cox analysis, KLK11 mRNA expression levels, apart from residual tumor mass, remained an independent predictive marker for OS (p = 0.007) and PFS (p = 0.015). Here, elevated KLK15 mRNA expression levels turned out to be significantly related to prolonged OS (p = 0.025) as well. High KLK11 but not the other KLK mRNA levels can be considered as strong independent favorable prognostic factor in this major ovarian cancer subtype.

Structural basis for the Zn2+ inhibition of the zymogen-like kallikrein-related peptidase 10

Although kallikrein-related peptidase 10 (KLK10) is expressed in a variety of human tissues and body fluids, knowledge of its physiological functions is fragmentary. Similarly, the pathophysiology of KLK10 in cancer is not well understood. In some cancer types, a role as tumor suppressor has been suggested, while in others elevated expression is associated with poor patient prognosis. Active human KLK10 exhibits a unique, three residue longer N-terminus with respect to other serine proteases and an extended 99-loop nearly as long as in tissue kallikrein KLK1. Crystal structures of recombinant ligand-free KLK10 and a Zn²⁺ bound form explain to some extent the mixed trypsin- and chymotrypsin-like substrate specificity. Zn²⁺-inhibition of KLK10 appears to be based on a unique mechanism, which involves direct binding and blocking of the catalytic triad. Since the disordered N-terminus and several loops adopt a zymogen-like conformation, the active protease conformation is very likely induced by interaction with the substrate, in particular at the S1 subsite and at the unusual Ser193 as part of the oxyanion hole. The KLK10 structures indicate that the N-terminus, the nearby 75-, 148-, and the 99-loops are connected in an allosteric network, which is present in other trypsin-like serine proteases with several variations.

NES1/KLK10 gene represses proliferation, enhances apoptosis and down-regulates glucose metabolism of PC3 prostate cancer cells

The normal epithelial cell-specific-1 (NES1) gene, also named as KLK10, is recognised as a novel putative tumour suppressor in breast cancer, but few studies have focused on the function of KLK10 in human prostate cancer. Our study confirms that the expression of KLK10 in prostate cancer tissue and cell lines (PC3, DU145, and LNCaP clone FGC) is low. Given that the androgen-independent growth characteristic of the PC3 cell line is more similar to clinical castration-resistant prostate cancer, we studied the role of KLK10 in PC3. In vitro and in vivo assays showed that over-expressing KLK10 in PC3 could decelerate tumour proliferation, which was accompanied with an increase in apoptosis and suppression of glucose metabolism. The related proteins, such as Bcl-2 and HK-2, were down-regulated subsequently. Furthermore, by up-regulating Bcl-2 or HK-2 respectively in the PC3-KLK10 cell line, we observed a subsequent increase of cell proliferation and a synchronous up-regulation of HK-2 and Bcl-2. Besides, KLK10 expression was also increased by Bcl-2 and HK-2, which suggests that there is a negative feedback loop between KLK10 and Bcl-2/HK-2. Thus, our results demonstrated that KLK10 may function as a tumour suppressor by repressing proliferation, enhancing apoptosis and decreasing glucose metabolism in PC3 cells.

Clinical significance of kallikrein-related peptidase (KLK10) mRNA expression in colorectal cancer

OBJECTIVES

Colorectal cancer (CRC) is one of the three most common cancers in both genders. Even though several biomarkers are in use in diagnosis and prognosis of the disease, they are marred by limited specificity and sensitivity. The human kallikrein-related peptidase 10 (KLK10) gene is a member of the human tissue kallikrein family. Because prostate specific antigen (PSA), the best biomarker for detecting and monitoring prostate cancer, is a member of this family, many other members, including KLK10, have been widely examined as novel biomarkers for different cancer types. In previous studies, KLK10 has been proposed as a diagnostic biomarker for ovarian carcinoma, while its methylation on exon 3 has been proposed as a prognostic marker for early-stage breast cancer patients. The purpose of this study was to analyse KLK10 mRNA expression and examine its prognostic value and potential clinical application as a novel molecular tissue biomarker in CRC.

DESIGN AND METHODS

The study group consisted of 190 colorectal samples. Total RNA was extracted from pulverised tissues and cDNA was prepared by reverse transcription. KLK10 was amplified by real-time PCR. B2M was used as a reference gene and HT-29 cells as positive control.

RESULTS

KLK10 expression was significantly higher in cancer tissues (P<0.001). Tumours of advanced TNM and Dukes' stage showed high KLK10 expression status (P=0.036; P=0.025). Patients with high KLK10 expression had a shorter disease-free and overall survival rates (P=0.014; P=0.020).

CONCLUSION

Our results suggest that KLK10 may serve as a new marker of unfavourable prognosis of colorectal cancer.

Zinc-rich inhibitor of apoptosis proteins (IAPs) as regulatory factors in the epithelium of normal and inflamed airways

Integrity of the airway epithelium (AE) is important in the context of inhaled allergens and noxious substances, particularly during asthma-related airway inflammation where there is increased vulnerability of the AE to cell death. Apoptosis involves a number of signaling pathways which activate procaspases leading to cleavage of critical substrates. Understanding the factors which regulate AE caspases is important for development of strategies to minimize AE damage and airway inflammation, and therefore to better control asthma. One such factor is the essential dietary metal zinc. Zinc deficiency results in enhanced AE apoptosis, and worsened airway inflammation. This has implications for asthma, where abnormalities in zinc homeostasis have been observed. Zinc is thought to suppress the steps involved in caspase-3 activation. One target of zinc is the family of inhibitor of apoptosis proteins (IAPs) which are endogenous regulators of caspases. More studies are needed to identify the roles of IAPs in regulating apoptosis in normal and inflamed airways and to study their interaction with labile zinc ions. This new information will provide a framework for future clinical studies aimed at monitoring and management of airway zinc levels as well as minimising airway damage and inflammation in asthma.

Kallikrein-related peptidase 10 expression in salivary gland tissues and tumours

OBJECTIVES

Kallikrein-related peptidase 10 (KLK10) has been implicated in the development of several types of cancer. The purpose of this study was to analyze the expression of KLK10 in 3 types of salivary gland tumour and normal salivary glands.

MATERIALS AND METHODS

A standard immunoperoxidase staining technique was used to assess the immunoexpression profile of KLK10 in normal salivary glands and 3 types of salivary gland tumour: pleomorphic adenoma, adenoid cystic carcinoma and mucoepidermoid carcinoma.

RESULTS

Pleomorphic adenomas showed significantly lower KLK10 levels than control tissues. Neither of the malignant tumours (adenoid cystic carcinoma and mucoepidermoid carcinoma) showed a significant alteration in the immunoreactive scores of KLK10 in comparison with the normal salivary gland tissues. KLK10 immunoreactive scores were comparable in adenoid cystic carcinoma and mucoepidermoid carcinoma. Pleomorphic adenoma had significantly lower levels of KLK10 than mucoepidermoid carcinoma.

CONCLUSIONS

The finding of lower KLK10 levels in pleomorphic adenoma suggests aberrant expression in a tumour that develops primarily from myoepithelial cells. A kallikrein cascade may play a role in the development and/or outcome of some salivary gland tumours.

Expression analysis and clinical evaluation of kallikrein-related peptidase 10 (KLK10) in colorectal cancer

Kallikrein-related peptidases (KLKs) represent a serine protease family having 15 members. KLK10 is a secreted protease with a trypsin-like activity. The function of KLK10 is poorly understood, although it has been suggested that KLK10 may function as a tumor suppressor gene. In human cancer, KLK10 gene shows organ-specific up- or down-regulation. Since KLKs are promising tumor biomarkers, the examination of KLK10 mRNA expression and its association with colorectal cancer (CRC) progression was studied using semi-quantitative PCR. One hundred and nineteen primary CRC specimens were examined for which follow-up information was available for a median period of 29 months (range, 1-104 months). KLK10 expression was found to be significantly associated with TNM stage (p=0.028). Cox proportional hazard regression model using univariate analysis revealed for the first time that high status KLK10 expression is a significant factor for disease-free survival (DFS; p=0.002) and overall survival (OS; p=0.026) of patients. Kaplan-Meier survival curves demonstrated that KLK10 expression of low status is significantly associated with longer DFS (p=0.001) as well as OS (p=0.021), suggesting that KLK10 gene expression may be used as a marker of unfavorable prognosis for CRC. As the epigenetics of cancer are unraveled, KLK10 may represent not only a novel biomarker, but also a promising future therapeutic target for the disease.

Immunohistochemical analysis of kallikrein-related peptidases in the normal kidney and renal tumors: potential clinical implications

Kallikrein-related peptidases (KLKs) have been shown to be differentially expressed in various malignancies and shown to be useful tumor markers. Previous immunohistochemistry (IHC) analysis demonstrated that KLKs 5, 6, 10, and 11 have a potential prognostic significance in renal cell carcinoma (RCC). To further explore the significance of KLKs, we examined KLKs 1, 6, 7, and 15 in different subtypes of renal tumors. KLK1 has stronger expression in high grade compared to low grade clear cell RCC. However, KLK6 and KLK7 show strong expression in low grade in contrast to high grade clear cell RCC. Furthermore, the expression of KLK7 can distinguish between oncocytoma and chromophobe RCC. Oncocytoma showed diffuse, strong granular cytoplasmic staining, but chromophobe RCC showed focal weak homogeneous cytoplasmic stain. The pattern of staining of different KLKs can also be helpful in differentiating some of the subtypes of renal tumors. Our results show the potential ability of KLKs to serve as diagnostic markers and expand previous data about the prognostic significance of KLKs in kidney cancer. In addition, our study is the first to show the ability of KLK staining to distinguish various types of kidney cancers when morphology is similar.

Analysis of human kallikrein 7 expression as a potential biomarker in cervical neoplasia

Overexpression of kallikrein 7, a proteolytic enzyme important for epithelial cell shedding, may be causally involved in carcinogenesis, particularly in tumor metastasis and invasion. In this study, we have evaluated hK7 (human kallikrein 7) protein levels by immunohistochemistry in 367 cervical histological samples including 35 cases of cervicitis, 31 low-grade cervical intraepithelial neoplasia, 51 high-grade cervical intraepithelial neoplasia (H-SIL), 197 squamous cervical carcinomas (SCC) and 53 cervical adenocarcinomas. We have observed that hK7 staining increased with the severity of cervical disease. Intense hK7 staining was found in 15.2% of cervicitis samples, in contrast to 55% of H-SIL and 68% of SCC. Moreover, 92.5% of adenocarcinomas also exhibited intense hK7 staining. Differences in the expression of hK7 could potentially be used as a biomarker for the characterization of different stages of cervical disease.

Frequent transcriptional inactivation of Kallikrein 10 gene by CpG island hypermethylation in non-small cell lung cancer

The role of Kallikrein 10 gene (KLK10) in non-small cell lung cancer (NSCLC) remains largely unknown. We determined the frequency and functional significance of KLK10 hypermethylation in NSCLC. The mRNA expression and methylation status of KLK10 in 78 pairs NSCLC specimens was explored. The biological effects of KLK10 were analyzed by transfection. The results showed that, KLK10 was significantly downregulated in NSCLC (57.7%, 45/78) as compared to non-cancer samples (P = 0.010). CpG island hypermethylation of KLK10 was detected in 46.2% (36/78) NSCLC tissues and was closely correlated with loss of transcript (P < 0.001). KLK10 methylation was associated with advanced stage (P = 0.013) and lymph metastasis (P = 0.015). Furthermore, demethylation treatment restored the expression of KLK10 in two lung adencarcinoma cell lines (A549, SPC-A1). Forced expression of KLK10 in A549 and SPC-A1 remarkably suppressed cells proliferation, migration in vitro and oncogenicity in vivo. Additionally, methylated KLK10 was detected in 38.7% (30/78) of plasma samples from cancer patients but rare in cancer-free controls (P < 0.001). In conclusion, KLK10 acts as a functional tumor suppressor gene in NSCLC, epigenetic inactivation of KLK10 is a common event contributing to NSCLC pathogenesis and may be used as a potential biomarker.

Proteins secreted by embryonic stem cells activate cardiomyocytes through ligand binding pathways

Human embryonic stem cells (hESC) underlie embryogenesis but paracrine signals associated with the process are unknown. This study was designed to 1) profile native proteins secreted by undifferentiated hESC and 2) determine their biological effects on primary neonatal cardiomyocytes. We utilized multi-analyte, immunochemical assays to characterize media conditioned by undifferentiated hESC versus unconditioned media. Expression profiling was performed on cardiomyocytes subjected to these different media conditions and altered transcripts were mapped to critical pathways. Thirty-two of 109 proteins were significantly elevated in conditioned media ranging in concentration from thrombospondin (57.2+/-5.0 ng/ml) to nerve growth factor (7.4+/-1.2pg/ml) and comprising chemokines, cytokines, growth factors, and proteins involved in cell adhesion and extracellular matrix remodeling. Conditioned media induced karyokinesis, cytokinesis and proliferation in mono- and binucleate cardiomyocytes. Pathway analysis revealed comprehensive activation of the ROCK 1 and 2 G-protein coupled receptor (GPCR) pathway associated with cytokinesis, and the RAS/RAF/MEK/ERK receptor tyrosine kinase (RTK) and JAK/STAT-cytokine pathway involved in cell cycle progression. These results provide a partial database of proteins secreted by pluripotent hESC that potentiate cell division in cardiomyocytes via a paracrine mechanism suggesting a potential role for these stem cell factors in cardiogenesis and cardiac repair.

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.

Co-expression of KLK6 and KLK10 as prognostic factors for survival in pancreatic ductal adenocarcinoma

Kallikreins play an important role in tumour microenvironment and as cancer biomarkers in different cancer entities. Previous studies suggested an upregulation of KLK10 and KLK6 in pancreatic ductal adenocarcinoma (PDAC). Therefore, we evaluated the clinicopathological role of these kallikreins and their value as biomarkers in PDAC.

Differential expression was validated by DNA-microarrays and immunohistochemistry in normal and malignant pancreatic tissues. Sera concentrations of both kallikreins were evaluated using ELISA. In silico analysis of possible protein interactions and gene silencing of KLK10 in vitro using siRNAs gave further insights in the pathomechanisms.

Gene expression analysis and immunohistochemistry demonstrated a strong expression for KLK10 and KLK6 in PDAC. Statistical analysis showed that co-expression of these kallikreins correlated with an R1-resection status (P=0.017) and worse outcome for overall survival (P=0.031). Multivariate analysis proofed that co-expression is an independent prognostic factor for survival (P=0.043). Importantly, KLK10 knockdown in AsPC-1 cells significantly reduced cell migration, whereas computational analysis suggested interaction of KLK6 with angiogenetic factors as an important mechanism.

Co-expression of KLK10 and KLK6 plays an unfavourable role in PDAC. Our results suggest that this effect is likely mediated by an interaction with the factors of the extracellular matrix and enhancement of cancer cell motility.

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.

Human kallikrein-related peptidase 12: antibody generation and immunohistochemical localization in prostatic tissues

BACKGROUND

Human tissue kallikrein-related peptidases (genes, KLKs; proteins, KLKs) are a subgroup of serine proteases present in a variety of tissues and biological fluids. A number of human tissue KLKs are established or candidate serologic biomarkers for prostate cancer. Human kallikrein-related peptidase 12 (KLK12, KLK12), recently identified in our laboratory, is a novel member of the KLK gene family. Here, we report generation of antibodies against the full-length recombinant KLK12 (classical form) and the immunohistological localization of this KLK in normal and malignant prostate tissues.

METHODS

The mature form of KLK12 cDNA was amplified using PCR and cloned into a plasmid vector for protein production in E. coli. Following identification by mass spectroscopy, recombinant KLK12 was purified and used as immunogen in rabbits. Anti- KLK12 antibody was used for immunostaining of paraffin-embedded sections of human prostate tissue. Immunoexpression of KLK12 in benign and malignant prostate tissue was evaluated using a prostate cancer tissue array.

RESULTS

Anti-KLK12 antibody showed a predominantly apical and membranous staining of the luminal cells of the normal prostate in contrast with the predominantly diffuse cytoplasmic staining observed in both prostatic intra-epithelial neoplasia and adenocarcinomas. This was occasionally associated with an intense granular supranuclear staining. More than 95% of the prostate cancers on the tissue microarray were KLK12 positive.

CONCLUSION

Higher levels of KLK12 in malignant prostatic glands, and the shift in subcellular localization of KLK12 in prostate cancer observed in this study point to the potential role of this kallikrein during prostate carcinogenesis.

Human kallikrein 10 ELISA development and validation in breast cancer sera

BACKGROUND

Human kallikrein 10 (hK10) is a putative secreted serine protease belonging to the same gene family as prostate specific antigen (hK3; PSA). There is significant interest in measuring hK10 which may act as a tumor suppressor in some cancers. We have developed an ELISA for hK10 and determined its analytical and clinical performance in normal and breast cancer sera.

METHODS

The assay used a previously described pair of monoclonal anti-hK10 antibodies and recombinant hK10 protein. Serum hK10 was detected quantitatively in a 2-step sandwich ELISA with colorimetric detection. The assay was analytically validated and used to determine serum levels of hK10 in a set of breast cancer, benign breast disease and normal samples.

RESULTS

The assay covered a linear range of 0.2 to 15 ng/mL and had a detection limit of 0.08 ng/mL. The within-run and between-run imprecision was <9%. The average spike and dilution linearity recoveries were 96 and 103% respectively. Mean hK10 concentration in normal female sera was 0.79+/-0.26 ng/mL. Concentrations were not age related and were not significantly different from benign fibrocystic disease or breast cancer. However, in a subset of breast cancer patients with both early and late stage disease, serum hK10 levels were elevated, at >1.55 ng/mL, above all normal female and benign disease samples.

CONCLUSIONS

We report in detail the analytical performance of a colorimetric hK10 ELISA validated in human serum and report for the first time the hK10 serum concentration in benign and breast cancer samples.

Proteolytic processing of human growth hormone by multiple tissue kallikreins and regulation by the serine protease inhibitor Kazal-Type5 (SPINK5) protein

BACKGROUND

Human growth hormone (hGH) is naturally present in numerous isoforms, some of which arise from proteolytic processing in both the pituitary and periphery. The nature of the enzymes that proteolytically cleave hGH and the regulation of this process are not fully understood. Our objective is to examine if members of a newly discovered human tissue kallikrein family (KLKs) are expressed in the pituitary and if these enzymes can cleave hGH in-vitro.

METHODS

Expression of 12 of the KLKs (KLKs 4-15) and serine protease inhibitor Kazal-type 5 (SPINK5) genes and their proteins in the pituitary was examined by RT-PCR and immunohistochemistry. Recombinant hGH was digested by various recombinant KLKs and fragments were characterized by N-terminal sequencing. SPINK5 recombinant fragments were used for inhibition of KLK activities.

RESULTS

We here describe for the first time expression of numerous KLKs (KLKs 5-8, 10-14) and SPINK5 in the pituitary. KLK6 and SPINK5 appeared to be localized to hGH-producing cells. KLKs 4-6, 8, 13 and 14 were able to cleave hGH, yielding various isoforms, in vitro. Inhibitor SPINK5 fragments were able to suppress activity of KLKs 4, 5 and 14 in vitro. Based on these data, we propose a model for the proteolytic processing of hGH in the pituitary and the regulation of this system by SPINK5 inhibitory domains. We speculate that loss of SPINK5 inhibitory domains, as in the case of Netherton syndrome, may lead to proteolytic over-processing of hGH and to growth retardation.

CONCLUSION

We conclude that many KLKs and SPINK5 are expressed in the pituitary. This serine protease-inhibitor system is likely to participate in the regulated proteolytic processing of hGH in the pituitary, leading to generation of hGH fragments. Our data suggest that KLKs 5, 6 and 14 might be involved in this process.

Cellular distribution of human tissue kallikreins: immunohistochemical localization

We have studied the immunohistochemical expression (IE) of eight non-tissue-specific human kallikreins (hKs) (hK5, 6, 7, 10, 11, 12, 13, and 14) in different normal tissues. The IE was always cytoplasmic, showing a characteristic pattern in some tissues. Comparison of the IE of all hKs studied in the different tissues revealed no major differences, suggesting that they share a common mode of regulation. Furthermore, hKs were immunohistochemically revealed in a variety of tissues, indicating that no protein is tissue-specific (except for hK2 and hK3, which have tissue-restricted expression). In general, our results correspond well with data from RT-PCR and ELISA assays. Glandular epithelia constitute the main kallikrein IE sites, and the staining in their secretions confirms that these proteases are secreted. A variety of other tissues express the proteins as well. We have also immunohistochemically evaluated all the above hKs in several malignant tissues. Tumors arising from tissues expressing kallikreins tested positive. Corresponding to the IE in normal glandular tissues, most hKs were expressed in adenocarcinomas. The prognostic value of several hKs was studied in series of prostate, renal cell, colon and urothelial carcinomas.

Human kallikrein 10, a predictive marker for breast cancer

Our laboratory is involved in identifying genes that can be used as early diagnostic or prognostic markers in breast cancer. We previously identified a gene (NES1) that is expressed in normal but not in transformed mammary epithelial cells (MECs). NES1 is located on chromosome 19q13.4 within the kallikrein locus and thus was designated as human kallikrein 10 (hK10), although we have been unable to detect any protease activity. Importantly, hK10 expression is decreased in a majority of breast cancer cell lines. Transfection of hK10 into hK10-negative breast cancer cells reduces the tumorigenicity. Using methylation-specific PCR and subsequent sequencing, we demonstrate a strong correlation between hypermethylation of hK10 and loss of mRNA expression. Further analysis showed that essentially 100% of normal breast specimens had hK10 expression, whereas 46% of ductal carcinoma in situ (DCIS) and the majority of infiltrating ductal carcinoma (IDC) samples lacked the hK10 mRNA. Importantly, hK10-negative DCIS diagnosed at the time of biopsy were subsequently diagnosed as IDC at the time of definitive surgery. It has been shown that hK10 protein expression is regulated by steroids. In addition to breast cancers, hK10 is downregulated in cervical cancer, prostate cancer and acute lymphocytic leukemia, whereas it is upregulated in ovarian cancers. These results point to the paradoxical role of hK10 in human cancers and underscore the importance of further studies of this kallikrein.

Characterization of human kallikreins 6 and 10 in ascites fluid from ovarian cancer patients

OBJECTIVES

Human kallikreins 6 (hK6) and 10 (hK10) are secreted serine proteases. We previously found that hK6 and hK10 are highly overexpressed in epithelial ovarian tumors and demonstrated that serum levels of hK6 and hK10 are valuable biomarkers for ovarian cancer diagnosis and prognosis. Our aim is to purify and characterize these two kallikreins from ascites fluid of ovarian cancer patients.

METHODS

Protein concentrations of hK6 and hK10 in ovarian cancer ascites fluids were measured with ELISA-type immunoassays. hK6 and hK10 were purified from the ascites fluids with immunoaffinity columns, followed by reverse-phase high performance liquid chromatography. Purified hK6 and hK10 were then subjected to N-terminal sequencing. Enzymatic analyses were performed with synthetic fluorogenic peptides.

RESULTS

hK6 and hK10 were present in ovarian cancer ascites fluid at concentrations ranging from 0.2-571 and 0.7-220 microg/l, respectively. The majority of hK6 and hK10 in the ascites fluids were present in the free (uncomplexed) form. Both hK6 and hK10 purified from the ascites fluid were zymogens with a molecular mass of 30 kDa. Purified hK6 exhibited trypsin-like enzymatic activity, whereas no enzymatic activity was observed for purified hK10. The enzymatic activity of hK6 could be suppressed by a neutralizing monoclonal antibody.

CONCLUSIONS

The majority of hK6 secreted by the ovarian tumor cells into the ascites fluid are present in the uncomplexed, zymogen form, possessing weak trypsin-like enzymatic activity. All hK10 present in ovarian cancer ascites fluids are in the uncomplexed, zymogen form and have no detectable enzymatic activity.

Effects of Long-term Androgen Administration on Breast Tissue of Female-to-Male Transsexuals

Our aim was to examine the effects of androgen administration on breast tissue histology of female-to-male transsexuals and to study the immunohistochemical expression of three human tissue kallikreins, hK3 (PSA), hK6, and hK10. We studied 23 female-to-male transsexuals who were treated with injectable testosterone for 18-24 months. We also used 10 control female breast tissues. All tissues were fixed in buffered formalin, embedded in paraffin, and examined by hematoxylin-eosin staining and immunohistochemical staining for PSA, hK6, and hK10. Females treated with androgens exhibited similar involutionary changes as those seen in breast of menopausal women, such as marked reduction of glandular tissue, involution of the lobuloalveolar structures, and prominence of fibrous connective tissue, but presence of only small amounts of fat tissue. Fibrocystic lesions were generally not observed. In immunohistochemistry, in control breast tissues, we found moderate to strong cytoplasmic immunoexpression of hK6 and hK10 in the epithelial ductal and lobuloalveolar structures, but myoepithelial cells were negative. Luminal secretions were also positive. In menopausal breast, the immunoexpression of hK6 and hK10 was weaker and focal. No control case showed immunoexpression for PSA. In female-to-male transsexuals, one case showed focal PSA cytoplasmic immunoexpression in the epithelium of moderately involuting lobules. Long-term administration of androgens in female-to-male transsexuals causes marked reduction of glandular tissue and prominence of fibrous connective tissue. These changes are similar to those observed at the end-stage of menopausal mammary involution. (J Histochem Cytochem 54:905-910, 2006)

Expression of the human kallikrein genes 10 (KLK10) and 11 (KLK11) in cancerous and non-cancerous lung tissues

Only one transcript for KLK10 was identified by RT-PCR in lung tissue, whereas KLK11 expressed at least four alternative transcripts. Quantitative analysis of KLK10 and KLK11 expression levels was assessed by real-time PCR, in a cohort of 47 patients with non-small-cell lung cancer (NSCLC). Expression levels of these genes were widely distributed in the population studied. Multivariate analysis revealed a correlation between KLK10 over-expression and the squamous cell carcinoma histotype (p=0.034). There was no correlation between gene expression and patient survival. Overall, both genes behaved similarly (p<0.001). These results suggest a co-regulation of KLK10 and KLK11 expression in lung and a lack of KLK10 suppressor role in NSCLC. Finally, our findings indicate that these genes are likely involved in normal physiology processes in bronchus.

Prognostic Implications of the Immunohistochemical Expression of Human Kallikreins 5, 6, 10 and 11 in Renal Cell Carcinoma

Human kallikreins 5, 6, 10 and 11 (hK5, 6, 10 and 11) are expressed by many normal tissues, and it has been suggested that they may represent candidate tumor-diagnostic or -prognostic markers. In patients with renal cell carcinoma (RCC), outcome is unpredictable despite the use of conventional prognostic factors. The aim of this study is to evaluate the immunohistochemical expression and the prognostic value of the above kallikreins in RCC. The study comprised 95 patients who underwent radical nephrectomy for RCC. The median follow-up period was 60 months (range 1-180 months). Fifty-seven RCC cases were immunostained for hK5, 70 for hK6, 70 for hK10 and 69 for hK11. The streptavidin-biotin-peroxidase method of immunostaining was performed using anti-hK5, anti-hK6, anti-hK10 and anti-hK11 monoclonal and polyclonal antibodies. The immunohistochemical expression of these kallikreins was correlated with tumor size, histological type, histological malignancy according to the Fuhrman four-grade scale, mitotic index, pathological stage and disease survival. For the statistical analysis, four grades were collapsed into two by which RCC cases were categorized as low malignant (LM) and high malignant (HM). In the normal renal parenchyma adjacent to the tumors, the renal tubular epithelium showed a cytoplasmic expression of all four kallikreins. In RCC, immunohistochemical expression was decreased: 33 of 57 cases (58%) were positive for hK5, 27 of 70 (39%) for hK6, 46 of 70 (66%) for hK10 and 32 of 69 (46%) for hK11. A statistically significant positive correlation was observed among the immunohistochemical expression of all kallikreins. HM-RCC expressed all kallikreins in a higher percentage of cases than LM-RCC, but statistically significant differences were only observed for hK6 and hK10 (55 vs. 27%, p = 0.016, and 79 vs. 56%, p = 0.044, respectively). hK6 and hK11 expression showed a positive correlation to pathological stage: hK6 with both Robson and TNM 2002 staging systems (p = 0.010 and p = 0.017, respectively), and hK11 only with the Robson staging system (p = 0.045). In both the Kaplan-Meier and the univariate Cox regression analyses, hK6 expression was negatively correlated with disease-specific survival (p = 0.05 and p = 0.038, respectively). In univariate analysis, nuclear grade, Robson stage and TNM stage also correlated with disease-specific survival. However, in the multivariate analysis, TNM stage was the only independent prognostic factor. In conclusion, although the immunohistochemical expression of hK5, hK6, hK10 and hK11 was downregulated in RCC, tumors of high grade and late stage expressed one or more of the above kallikreins in a higher percentage of cases, and hK6 may predict a poor disease outcome in RCC.

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.

Immunohistochemical localization of human kallikreins 6, 10 and 13 in benign and malignant prostatic tissues

Human kallikreins 6, 10 and 13 (hK6, hK10 and hK13) are expressed by many normal, mainly glandular tissues, including prostatic epithelium. Some kallikreins may function as tumor suppressors or are downregulated during cancer progression. The aim of this study was to evaluate the immunoexpression of these kallikreins in benign and malignant prostatic tissues and correlate their expression with prostate cancer (PC) prognosis. Included in the study were 25 cases of nonmalignant prostate and 179 cases of PC. Among them, 122 PC cases were immunostained for hK6, 94 for hK10 and 113 for hK13, respectively. The follow-up period for a subset of 68 patients who had undergone radical prostatectomy (RP) was 1-58 months (mean=13.4 +/- 1.7 and median=8.0 months). A cutoff value of 0.2 microg/l of serum PSA was established as a biochemical recurrence threshold. Follow-up information was available for 26/55 RP cases stained for hK6, 14/32 cases stained for hK10 and 25/59 cases stained for hK13. Gleason score (GS) 7 carcinomas were stratified as 7a and 7b, according to the primary grade. PC with GS 2-7a were histologically categorized as low malignant (LM) and PC with GS 7b-10 as high malignant (HM). The immunohistochemical method of streptavidin-biotin-peroxidase using monoclonal and polyclonal antibodies was performed. In the benign prostate and in prostatic intraepithelial neoplasia, a cytoplasmic immunostaining of varying intensity was evident. In PC, the immunoexpression of all kallikreins was decreased: 102/122 cases (84%) were positive for hK6, 73/94 (78%) for hK10 and 97/113 (86%) for hK13, respectively. A statistically significant difference in expression was found, in comparison to nonmalignant prostates (P=0.029, 0.009 and 0.045, respectively). Also, a positive correlation was observed between the immunoexpression of these three kallikreins. Concerning the histological grade, HM-PC expressed all three kallikreins with a slightly higher percentage than LM-PC: 79 vs 88% for hK6, 76 vs 79% for hK10 and 76 vs 92% for hK13. These differences were statistically significant only in the case of hK13 (P=0.024). Serum PSA did not correlate with kallikrein immunoexpression in PC. Furthermore, there was no significant correlation between kallikrein expression and pathological stage or recurrence, in the cases of RP. All three kallikreins are expressed in the nonmalignant and malignant prostate, with cancer tissues demonstrating slightly lower expression. Expression levels did not correlate with aggressiveness and they do not seem to have value for prostate cancer prognosis.

Human kallikrein 13 expression in normal tissues: an immunohistochemical study

The human tissue kallikrein 13 gene (KLK13), encoding for hK13 protein, was recently cloned and characterized. Here we describe the immunohistochemical (IHC) localization of hK13 in normal human tissues and compare it with the expression of two other kallikreins, hK6 and hK10. We performed the streptavidin-biotin IHC method on 204 paraffin blocks from archival, current, and autopsy material prepared from almost every normal human tissue, using a polyclonal and a monoclonal hK13 antibody. The staining was cytoplasmic and both antibodies yielded similar results. The hK13 protein was revealed in a variety of tissues, mainly in glandular epithelia. Other epithelia that expressed hK13 included the urothelium, the spermatic epithelium, and the epithelium of the choroid plexus. hK13 was intensely immunoexpressed by some endocrine organs, such as the adenohypophysis, the thyroid gland, the parathyroid glands, the adrenal medulla, the Leydig cells of the testis, and the cells of the endocrine pancreas. Immunoreactivity was also observed in the primordial follicles, the corpus luteum, and sparse luteinized cells in the stroma of the ovary, the trophoblastic cells of the placenta, the Hassall's corpuscles of the thymus, and chondrocytes. Nerves and ganglia of the peripheral nervous system, and both neurons and glial cells in the central nervous system, were positive. In short, hK13 was expressed by many glandular epithelia, some endocrine organs, and some specialized epithelia and cells. Comparison of these data with hK6 and hK10 expression suggests that the three kallikreins have a similar IHC pattern in normal human tissues.

Immunohistochemical localization of human kallikreins 6 and 10 in pancreatic islets

Tissue kallikreins are thought to be present in the pancreatic islets of Langerhans and to aid in the conversion of proinsulin to insulin. In recent immunohistochemical studies, we observed strong staining of the newly identified human kallikreins 6 and 10 (hK6 and hK10) in the islets of Langerhans. Here, we examine hK6 and hK10 immunoexpression in different types of islet cells of the endocrine pancreas, in order to obtain clues for hK6 and hK10 function in these cells. Ten cases of normal pancreatic tissue, two cases of nesidioblastosis, five insulin-producing tumours and one case of multiple endocrine neoplasia 1 syndrome, containing an insulin-, a somatostatin- and several glucagon-producing tumours, as well as tiny foci of endocrine dysplasia with different predominance of the secreted hormones (mainly glucagon and pancreatic polypeptide) were included in the study. A streptavidin--biotin--peroxidase and an alkaline phosphatase protocol, as well as a sequential immunoenzymatic double staining method were performed, using specific antibodies against hK6, hK10, insulin, glucagon, somatostatin, pancreatic polypeptide, and serotonin. hK6 and hK10 immunoexpression was observed in the islets of Langerhans, including the pancreatic polypeptide-rich islets, in the normal pancreas. Scattered hK6 and hK10 positive cells were localized in relationship with pancreatic acinar cells. In the exocrine pancreas, a cytoplasmic and/or brush border hK6 and hK10 immunoexpression was observed in the median and small sized pancreatic ducts, while the acinar cells were negative. Foci of nesidioblastosis and endocrine dysplasia expressed both kallikreins. hK6 and hK10 were also strongly and diffusely expressed throughout all insulin-, glucagon- and somatostatin-producing tumours. The double staining method revealed co-localization of each hormone and hK6/hK10 respectively, in the same cellular population, in the normal as well as in the diseased pancreas. Our results support the view that hK6 and hK10 may be involved in insulin and other pancreatic hormone processing and/or secretion, as well as in physiological functions related to the endocrine pancreas.