The use of kallikrein-related peptidases as adjuvant prognostic markers in colorectal cancer. Br J Cancer. 2009;100:1659-1665. [PMID: 19367279 PMCID: PMC2696752 DOI: 10.1038/sj.bjc.6605033]

The Role of Kallikrein 7 in Tumorigenesis

Kallikrein 7 (KLK7) is a secreted serine protease with chymotrypsic protease activity. Abnormally high expression of KLK7 is closely related to the occurrence and development of various types of cancer. Therefore, KLK7 has been identified as a potential target for cancer drug development design in recent years. KLK7 mediates various biological and pathological processes in tumorigenesis, including cell proliferation, migration, invasion, angiogenesis, and cell metabolism, by hydrolyzing a series of substrates such as membrane proteins, extracellular matrix proteins, and cytokines. This review mainly introduces the downstream cell signaling pathways involved in the activation of KLK7 and its substrate-related proteins. This review will not only help us to better understand the mechanisms of KLK7 in regulating biological and pathological processes of cancer cells, but also lay a solid foundation for the design of inhibitors targeting KLK7.

Clinical significance of kallikrein 5 as a novel prognostic biomarker in gastric adenocarcinoma

Backgrounds

Gastric cancer is one of the most common cancers with unsatisfied prognosis. It is challenging to predict gastric cancer prognosis due to its highly heterogeneous nature. Kallikrein 5 (KLK5) belongs to the family of kallikreins, which plays a crucial role in serine proteolysis and exerts diverse physiological functions. The role of KLK5 in human gastric adenocarcinoma (GAC) has not been elucidated. In the present study, we aimed to examine the expression level of KLK5 and dissect whether the KLK5 expression was associated with GAC prognosis.

Patients and methods

Clinicopathological analyses were performed in a retrospective GAC patient cohort (n = 138). The expression of KLK5 was tested by quantitative RT‐PCR and immunohistochemistry staining. The prognostic role of KLK5 in GAC was assessed by univariate and multivariate analyses. The effects of KLK5 on cell proliferation, migration, and invasion were examined through cellular experiments.

Results

The data showed that KLK5 expression was elevated in GAC tissues compared with normal stomach tissues. Protein expression of KLK5 was positively correlated with tumor invasion depth and lymph node metastasis. Patients with higher KLK5 expression had poorer overall survival. KLK5 was identified to be an independent risk factor according to multivariate analysis. Using human GAC cell lines, we found that KLK5 can promote tumor cell migration and invasion.

Conclusions

Our study demonstrated that higher expression of KLK5 was significantly correlated with a poorer prognosis of GAC patients, implying the potential of KLK5 as a novel prognostic biomarker in GAC.

Could Kallikrein-Related Serine Peptidase 3 Be an Early Biomarker of Environmental Exposure in Young Women?

Bisphenols and phthalates affect androgen receptor-mediated signaling that directly regulates Kallikrein-Related serine Peptidase 3 (KLK3) secretion, indicating that environmental factors may play a role in KLK3 secretion. With the aim of obtaining preliminary data on whether KLK3 could serve as an early marker of environmental pollution effects, in 61 and 58 healthy women living in a high environmental impact (HEI) and low environmental impact (LEI) area, respectively, serum KLK3 levels at different phases of menstrual cycle were measured. KLK3 values resulted in always being higher in the HEI group with respect to the LEI group. These differences were particularly relevant in the ovulatory phase (cycle day 12°–13°) of the menstrual cycle. The differences in KLK3 values during the three phases of the menstrual cycle were significant in the LEI group differently from the HEI group. In addition, higher progesterone levels were observed in the LEI group with respect to the HEI group in the luteal phase, indicating an opposite trend of KLK3 and progesterone in this phase of the menstrual cycle. Although changes in KLK3 could also depend on other factors, these preliminary data could be an early indication of an expanding study of the role of biomarkers in assessing early environmental effects for female reproductive health.

A nine-gene signature to improve prognosis prediction of colon carcinoma

This study aims to establish a gene model that can robustly and effectively predict the prognosis of colon carcinoma patients via bioinformatics. Data along with clinical information in GSE39582 Series Matrix were firstly downloaded from Gene Expression Omnibus (GEO) database. Next, differentially expressed genes (DEGs) were obtained through "edgeR" analysis. Finally, a risk predication model was established through a series of regression analyses, and then prognostic performance of the model was comprehensively evaluated though Kaplan-Meier and receiver operating characteristic (ROC) analysis. Gene set enrichment analysis (GSEA) was further performed. Totally, 846 DEGs were obtained by analyzing the gene expression data in GSE39582 dataset. A 9-gene signature-based risk predication model was established via regression analyses, and the model-based risk score was formulated as: Riskscore = (-0.1214) * TNFRSF11A + (-0.2617) * TMEM97 + (-0.1041) * LGR5 + 0.0973 * KLK10 + 0.1655 * HOXB8 + 0.227 * FKBP10 + (-0.1312) * CXCL13 + (-0.1316) * CXCL10 + 0.2593 * CD36. Kaplan-Meier curve showed that colon carcinoma patients in the high-risk group had a lower survival rate. GSEA showed that high-risk group and low-risk group displayed significant difference in biological pathways including ECM RECEPTOR INTERACTION. Besides, correlation analysis between the riskscore of the model and clinical features of patients revealed that the model could effectively predict the prognosis of patients in different ages (age>65, age<65) and stages (tumor_stage I/II, tumor_stage III/IV, T3&T4, N0&N1, N2&N3, M0). This study provides a robust model for the prognosis prediction of colon carcinoma, and lays a basis for researching the molecular mechanism underlying the development of colon carcinoma.

L1CAM, CA9, KLK6, HPN, and ALDH1A1 as Potential Serum Markers in Primary and Metastatic Colorectal Cancer Screening

BACKGROUND

Colorectal cancer (CRC) screening at the earlier stages could effectively decrease CRC-related mortality and incidence; however, accurate screening strategies are still lacking. Considerable interest has been generated in the detection of less invasive tests requiring a small sample volume with the potential to detect several cancer biomarkers simultaneously. Due to this, the ELISA-based method was undertaken in this study.

METHODS

Concentrations of neural cell adhesion molecule L1 (L1CAM), carbonic anhydrase IX (CA9), mesothelin (MSLN), midkine (MDK), hepsin (HPN), kallikrein 6 (KLK6), transglutaminase 2 (TGM2) aldehyde dehydrogenase 1 family, member A1 (ALDH1A1), epithelial cell adhesion molecule (EpCAM), and cluster of differentiation 44 (CD44) from blood serum of 36 primary CRC and 24 metastatic CRC (mCRC) were calculated via MAGPIX® System (Luminex Corporation, USA).

RESULTS

Significantly increased concentration (p < 0.05) of three serum biomarkers (L1CAM, CA9, and HPN) were shown in mCRC when compared with primary CRC. HPN and KLK6 showed significant differences (p < 0.05) in concentration among different stages of CRC. In contrast, levels of HPN and ALDH1A1 were significantly elevated (p < 0.05) in chemotherapy-treated CRC patients as compared with nontreated ones. Conclusion: Serum biomarkers could act as a potential early CRC diagnostics test, but further additional testings are needed.

Biomarker implication of kallikrein-related peptidases as prognostic tissue substrates of poor survival in colorectal cancer

Background

Recent studies have demonstrated that the kallikrein and kallikrein-related peptidases (KLKs) exhibit aberrant expression in patients with colorectal cancer (CRC) and might be considered as potential prognostic biomarkers of CRC. However, inconsistent findings have been reported, which promote us to summarize the global prognostic roles of KLKs for survival in CRC patients.

Methods

Eligible published studies were identified by searching electronic databases with several search strategies. The patients’ baseline characteristics and survival results were extracted from enrolled studies and pooled as combined hazard ratio (HR) with 95% confidence interval (95% CI) to estimate the effect size.

Results

A total of 25 and 22 eligible studies were included in the meta-analysis to evaluate the prognostic roles of KLKs on overall survival (OS) and disease-free survival (DFS), respectively. KLKs overexpression was significantly associated with worse OS (pooled HR = 1.43, 95% CI 1.27–1.60, P < 0.001) and short DFS (pooled HR = 1.35, 95% CI 1.21–1.51, P < 0.001). Importantly, subgroup and meta-regression analyses revealed the survival differences among different races and detection methods of KLKs. Furthermore, several specific members of KLKs were identified to be more significantly related to worse OS and DFS compared with other members.

Conclusion

The present study demonstrated that KLKs may have the potential to serve as promising biomarkers to monitor CRC prognosis and progression. The promising results concerning the utility of KLKs in clinical practice encourage the further investigation of their clinical utility applicability as tumor markers of CRC.

Cancer-related proteins in serum are altered in workers occupationally exposed to polycyclic aromatic hydrocarbons: a cross-sectional study

Exposure to some polycyclic aromatic hydrocarbons (PAH) increases the risk of cancer and is common particularly for workers in occupations such as chimney sweeping. In exposed workers, screening of early cancer-related markers provides important information to identify individuals at risk. Here, we aimed to elucidate the associations between PAH exposure and serum levels of cancer-related proteins in 118 chimney sweeps and 126 occupationally unexposed controls, all non-smoking males from Sweden. Monoydroxylated metabolites of pyrene, phenanthrene, benzo[a]pyrene and benzo[a]anthracene were measured in urine using liquid chromatography coupled to tandem mass spectrometry and 90 cancer-related proteins were measured in serum using a proximity extension assay. Linear regression analysis adjusted for age and body mass index, and false discovery rate (FDR) identified 17 serum proteins that were differentially expressed (16 upregulated and 1 downregulated) in chimney sweeps compared with controls (FDR < 0.05). Concentrations of the peptidase kallikrein 13 (KLK13) showed significant positive associations with urinary concentrations of the PAH metabolites 3-hydroxybenzo[a]pyrene (3-OH-BaP) [B, 95% confidence interval (CI): 0.042, 0.008–0.076] and 3-hydroxybenzo[a]anthracene (3-OH-BaA) (B, 95% CI: 0.068, 0.002–0.134). Moreover, dose–response relationships were observed between KLK13 and 3-OH-BaP (trend test P = 0.027) and 3-OH-BaA (P = 0.035). Pathway and gene ontology analyses showed that cell movement, cell adhesion and cell migration were the predominant molecular functions associated with the top differentially expressed proteins. In conclusion, we found a number of putative cancer-related proteins differentially expressed in workers exposed to PAH. This warrants effective measure to reduce PAH exposure among workers as well as further investigation to confirm these findings.

Knockdown of KLK12 inhibits viability and induces apoptosis in human colorectal cancer HT-29 cell line

Kallikrein-related peptidase 12 (KLK12) is overexpressed in cancer tissues including gastric, breast and prostate cancer. However, the role of KLK12 in colorectal cancer is not fully understood. In the present study, the level of KLK12 was determined by performing reverse transcription-polymerase chain reaction (RT-qPCR) in colorectal cancer tissues and cell lines. Lipofectamine^® 2000 was used to transfect HT-29 cells to overexpress and knockdown KLK12. Cell viability, migration, invasion and apoptosis were detected by MTT, wound healing, Transwell and flow cytometry assays, respectively. The mRNA and protein expression levels of EMT-associated proteins, apoptosis-associated proteins, phosphorylated adenosine monophosphate-activated protein kinase (p-AMPK) and phosphorylated mammalian target of rapamycin (p-mTOR) were determined by RT-qPCR and western blot analysis. It was identified that the KLK12 mRNA levels were increased significantly in colorectal cancer tissues and cell lines. KLK12 small interfering RNA inhibited cell viability, migration and invasion. Furthermore, epithelial-mesenchymal transition (EMT)-associated proteins were altered by siKLK12. Cell apoptosis was induced by KLK12 downregulation, which was demonstrated by the changes in apoptosis-associated proteins; however, KLK12 overexpression produced the opposite effect. SiKLK12 enhanced the expression of p-AMPK and suppressed the expression of p-mTOR, while KLK12 overexpression had the opposite effect. Promotion of KLK12 overexpression-induced cell viability was reversed by 5-aminoimidazole-4-carboxamide ribonucleotide, an activator of the AMPK signaling pathway, and rapamycin, a specific inhibitor of the mTOR signaling pathway. Taken together, the results of the present study indicated that KLK12 was overexpressed in colorectal cancer and may regulate cell behavior, potentially via the AMPK and mTOR pathways.

Uncovering the clinical impact of kallikrein-related peptidase 5 (KLK5) mRNA expression in the colorectal adenoma-carcinoma sequence

Background Kallikrein-related peptidases (KLKs) are a subgroup of serine proteases located on chromosome 19q13.3. Most KLKs have been extensively studied as potential biomarkers for several carcinomas and other diseases. KLK5 was originally identified from a keratinocyte library, and its enzyme was purified from the stratum corneum of human skin. KLK5 was shown to be differentially expressed in a variety of endocrine tumors, although it is not as yet examined widely in colorectal cancer (CRC). Methods In this study, we quantitatively assessed the mRNA expression status of KLK5 in 197 colorectal tissues from 133 patients (70 cancerous and their paired normal colonic mucosa for 64 of them, as well as 63 colorectal adenomas) by quantitative real-time PCR (qPCR) using TaqMan probes. Statistical analysis evaluated the results. Results It was shown that KLK5 expression is reduced following the histologically non-cancerous-adenoma sequence (p<0.001), whereas it is increased during the sequence adenoma-carcinoma (p<0.001). Furthermore, KLK5 positive expression is associated with positive nodal status (p=0.022), advanced tumor stage (p=0.038) and high histological grade (p=0.033). Cox univariate analysis revealed that KLK5 positive expression is associated with disease-free survival (DFS) (p=0.028) and overall survival (OS) of patients (p=0.048). Kaplan-Meyer survival models showed that patients with positive KLK5 expression have lower DFS (p=0.009) and OS (p=0.019). Receiver operating characteristic (ROC) analysis demonstrated for first time that KLK5 expression had significant discriminatory values between cancer and adenoma tissues (area under the curve [AUC] 0.77; 95% confidence interval [CI]=0.69-0.85, p=0.03). Conclusions KLK5 mRNA expression may be useful for the differentiation of CRC from colorectal adenoma and represents a potential unfavorable prognostic biomarker for CRC.

Mucin 16 and kallikrein 13 as potential prognostic factors in colon cancer: Results of an oncological 92-multiplex immunoassay

Colon cancer represents one of the most common cancers in the world. Despite improved treatment, mortality remains high. In order to improve the assessment of prognosis for colon cancer patients, identifying new prognostic markers remains necessary. We analyzed preoperative serum samples from 148 colon cancer patients surgically treated at Helsinki University Hospital from 1998 through 2002 using a multiplex proximity extension assay (Oncology II panel, Olink Bioscience, Uppsala, Sweden), a panel constituting 92 immunological and oncological markers. We performed univariate and multivariate analyses on these patients and calculated the disease-specific survival among patients using the log-rank test for Kaplan–Meier estimates. In the univariate survival analysis of 92 biomarkers, 26 resulted in p < 0.1. Among these, eight biomarkers emerged as statistically significant (p < 0.05). Patients with low levels of kallikrein 13 had a poor prognosis. Moreover, patients with high levels of amphiregulin, carcinoembryonic antigen-related adhesion molecule 5, interleukin 6, mucin 16, syndecan 1, transforming growth factor alpha, and vimentin also had a poor prognosis. In the multivariate analysis, kallikrein 13 and mucin 16 emerged as independent prognostic markers. The role of kallikrein 13, a member of the serine protease kallikrein biomarker family, in tumorigenesis remains unclear. Mucin 16 is also known as carbohydrate antigen 125, a well-known ovarian cancer biomarker. Patients with low levels of kallikrein 13 (hazard ratio: 0.36; 95% confidence interval: 0.14–0.92; p = 0.033) and high levels of mucin 16 (hazard ratio: 3.15; 95% confidence interval: 1.68–5.93; p < 0.005) had a poor prognosis. Mucin 16 and kallikrein 13 represent independent prognostic markers for colon cancer. Furthermore, the clinical utility of mucin 16 and kallikrein 13 serum tests warrants additional investigation.

An unexpected switch in peptide binding mode: from simulation to substrate specificity

A ten microsecond molecular dynamics simulation of a kallikrein-related peptidase 7 peptide complex revealed an unexpected change in binding mode. After more than two microseconds unrestrained sampling we observe a spontaneous transition of the binding pose including a 180° rotation around the P1 residue. Subsequently, the substrate peptide occupies the prime side region rather than the cognate non-prime side in a stable conformation. We characterize the unexpected binding mode in terms of contacts, solvent-accessible surface area, molecular interactions and energetic properties. We compare the new pose to inhibitor-bound structures of kallikreins with occupied prime side and find that a similar orientation is adopted. Finally, we apply in silico mutagenesis based on the alternative peptide binding position to explore the prime side specificity of kallikrein-related peptidase 7 and compare it to available experimental data. Our study provides the first microsecond time scale simulation data on a kallikrein protease and shows previously unexplored prime side interactions. Therefore, we expect our study to advance the rational design of inhibitors targeting kallikrein-related peptidase 7, an emerging drug target involved in several skin diseases as well as cancer.

Kallikrein-related peptidases and associated microRNAs as promising prognostic biomarkers in gastrointestinal malignancies

Gastrointestinal (GI) malignancies represent a wide spectrum of diseases of the GI tract and its accessory digestive organs, including esophageal (EC), gastric (GC), hepatocellular, pancreatic (PC) and colorectal cancers (CRC). Malignancies of the GI system are responsible for nearly 30% of cancer-related morbidity and approximately 40% of cancer-related mortality, worldwide. For this reason, the discovery of novel prognostic biomarkers that can efficiently provide a better prognosis, risk assessment and prediction of treatment response is an imperative need. Human kallikrein-related peptidases (KLKs) are a subgroup of trypsin and chymotrypsin-like serine peptidases that have emerged as promising prognosticators for many human types of cancer, being aberrantly expressed in cancerous tissues. The aberrant expression of KLKs in human malignancies is often regulated by KLK/microRNAs (miRNAs) interactions, as many miRNAs have been found to target KLKs and therefore alter their expression levels. The biomarker utility of KLKs has been elucidated not only in endocrine-related human malignancies, including those of the prostate and breast, but also in GI malignancies. The main purpose of this review is to summarize the existing information regarding the prognostic significance of KLKs in major types of GI malignancies and highlight the regulatory role of miRNAs on the expression levels of KLKs in these types of cancer.

Diagnostic and prognostic biomarker potential of kallikrein family genes in different cancer types

Purpose

The aim of this study was to compare and contrast the expression of all members of the Kallikrein (KLK) family of genes across 15 cancer types and to evaluate their utility as diagnostic and prognostic biomarkers.

Results

Severe alterations were found in the expression of different Kallikrein genes across various cancers. Interestingly, renal clear cell and papillary carcinomas have similar kallikrein expression profiles, whereas, chromophobe renal cell carcinoma has a unique expression profile. Several KLK genes have excellent biomarker potential (AUC > 0.90) for chromophobe renal cell carcinoma (KLK2, KLK3, KLK4, KLK7, KLK15), renal papillary carcinoma (KLK1, KLK6, KLK7), clear cell renal cell carcinoma (KLK1, KLK6), thyroid carcinoma (KLK2, KLK4, KLK13, KLK15) and colon adenocarcinoma (KLK6, KLK7, KLK8, KLK10). Several KLK genes were significantly associated with mortality in clear cell renal cell carcinoma (KLK2: HR = 1.69; KLK4: HR = 1.63; KLK8: HR = 1.71; KLK10: HR = 2.12; KLK11: HR = 1.76; KLK14: HR = 1.86), papillary renal cell carcinoma (KLK6: HR = 3.38, KLK7: HR = 2.50), urothelial bladder carcinoma (KLK5: HR = 1.89, KLK6: HR = 1.71, KLK8: HR = 1.60), and hepatocellular carcinoma (KLK13: HR = 1.75).

Methods

The RNA-seq gene expression data were downloaded from The Cancer Genome Atlas (TCGA). Statistical analyses, including differential expression analysis, receiver operating characteristic curves and survival analysis (Cox proportional-hazards regression models) were performed.

Conclusions

A comprehensive analysis revealed the changes in the expression of different KLK genes associated with specific cancers and highlighted their potential as a diagnostic and prognostic tool.

Expression of kallikrein-related peptidase 13 is associated with poor prognosis in esophageal squamous cell carcinoma

OBJECTIVE

Our previous differential transcriptome analysis between a paired specimen of normal and esophageal squamous cell carcinoma (ESCC) tissues found aberrant expression of kallikrein-related peptidase 13 (KLK13) in tumors. In this study, we evaluated the expression of KLK13 in many ESCC cases in relation with clinical features, and the prognosis.

METHODS

Eighty-eight ESCC cases were subjected to immunohistological staining for KLK13 and classified into KLK13-negative and KLK13-positive groups. Difference of clinical features and the prognosis between the groups was analyzed.

RESULTS

In normal esophageal mucosa, KLK13 expression was evident but limited in the stratum granulosum in all cases. By contrast, only 27 of 88 ESCC samples showed KLK13 expression, whereas the remaining 61 tumors showed no KLK13 expression. The KLK13-positive group was significantly associated with pT classification (deeper tumor invasions; P = 0.0282), pN classification (lymph node metastasis; P = 0.0163), and advanced TNM stage (P = 0.0198). In KLK13-positive samples, KLK13-expressing cells often expressed Ki67, a proliferation marker, unlike normal mucosa, in which Ki67-expressing cells were limited to the basal layer and did not express KLK13. Compared with patients with KLK13-negative group, KLK13-positive group showed poorer postoperative prognosis.

CONCLUSION

Relatively high levels of KLK13 expression in ESCC were associated with cell proliferation and correlated with tumor progression, advanced cancer stage, and poor prognosis.

Advanced high-grade serous ovarian cancer: inverse association of KLK13 and KLK14 mRNA levels in tumor tissue and patients' prognosis

PURPOSE

Gene expression of a variety of the 15 members of the KLK serine protease family is dysregulated in ovarian cancer. We aimed at determining the clinical relevance of KLK13 and KLK14 mRNA expression in tumor tissues of a homogeneous patient cohort afflicted with advanced high-grade serous ovarian cancer (FIGO stage III/IV).

METHODS

mRNA expression levels of KLK13 and KLK14 were assessed by quantitative PCR in tumor tissue of 91 patients and related with clinical factors and patients' outcome.

RESULTS

There was no significant association of KLK13 and KLK14 mRNA expression with the clinical factors ascitic fluid volume or residual tumor mass. In univariate Cox regression analysis, elevated KLK13 mRNA levels were significantly linked with shorter progression-free (PFS; hazard ratio [HR] = 1.97, P = 0.020) and overall survival (OS; HR = 1.81, P = 0.041). High KLK14 mRNA levels were significantly associated with prolonged PFS (HR = 0.44, P = 0.017) and showed a trend towards significance for OS (HR = 0.55, P = 0.070). In multivariable analysis, including the factors age, residual tumor mass, ascitic fluid volume, KLK13, and KLK14, both KLKs, apart from residual tumor mass, remained statistically independent predictive markers: patients with high KLK13 mRNA expression levels displayed a more than twofold increase risk for shorter PFS (HR = 2.14, P = 0.020) as well as OS (HR = 2.05, P = 0.028), whereas elevated KLK14 mRNA values were found to be significant for both, prolonged PFS (HR = 0.36, P = 0.007) and OS (HR = 0.46, P = 0.037).

CONCLUSION

These results indicate that in advanced high-grade serous ovarian cancer KLK13 may become proficient for tumor-supporting functions, whereas KLK14 may have adopted tumor-suppressing activity.

Knockdown of KLK11 reverses oxaliplatin resistance by inhibiting proliferation and activating apoptosis via suppressing the PI3K/AKT signal pathway in colorectal cancer cell

Introduction

Kallikrein 11 (KLK11) plays a crucial role in drug-resistance to oxaliplatin (L-OHP) in the treatment of metastatic colorectal cancer (mCRC). The study aimed to investigate the role of KLK11 in chemoresistance, and to clarify the mechanism underlying reverse of L-OHP resistance by knockdown of KLK11.

Materials and Methods

Resistance to oxaliplatin was induced in HCT-8 (HCT-8/L-OHP) colorectal adenocarcinoma cell lines by exposing cells to increasing concentrations of L-OHP. MTT, RT-qPCR, and Western blot were used to evaluate the resistance to L-OHP. We then knocked down KLK11 in HCT-8/L-OHP cells to explore the mechanism through which KLK11 reverses L-OHP resistance. The mRNA and protein expression of KLK11 in tissues from mCRC patients were detected by RT-qPCR and immunohistochemistry.

Results

The drug resistance index (RI) of HCT-8/L-OHP cell line to L-OHP, 5-Fluorouracil (5-FU), Irinotecan (CPT-11), Vincristine (VCR) and Cis-diamminedichloroplatinum (CDDP) were 10, 5.35, 3.23, 1.28, and 6.64, respectively. Increased expression of multi-drug resistant genes ABCC1, ABCB1, GSTP1 and ERCC1 were detected in HCT-8/L-OHP cell line. Moreover, the activated PI3K/AKT pathway was related to L-OHP-resistance. Knockdown of KLK11 in HCT-8/L-OHP cell reversed L-OHP-resistance by inhibiting cell growth and activating apoptosis via suppressing the PI3K/AKT signaling pathway. Moreover, high expression of KLK11 in chemoresistant-patients was associated with lymph node metastases and histopathology.

Conclusion

KLK11 was highly expressed in chemoresistant-patients and L-OHP-resistant cell lines. Moreover, L-OHP resistance was associated with activated PI3K/AKT signal pathway. Knockdown of KLK11 can reverse L-OHP resistance by blocking PI3K/AKT signaling pathway.

Downregulation of KLK13 promotes the invasiveness and metastasis of oesophageal squamous cell carcinoma

KLK13 downregulation occurs in tumour tissues in comparison with adjacent normal tissues from patients with oesophageal squamous cell carcinoma (OSCC). KLK13 mRNA levels were tested in OSCC tumour tissues and adjacent noncancerous tissues from 138 patients. In addition, the correlation between KLK13 mRNA levels and OSCC clinicopathologic features was analysed. KLK13 mRNA levels decreased notably in tumour tissues compared with those in adjacent noncancerous tissues. And decreased KLK13 mRNA levels indicated significant correlations with higher tumour grade, elevated TNM (UICC, 2009) stage classification, deeper infiltration and more lymph node metastases. And thus KLK13 may be a promising diagnostic marker. Decreased KLK13 mRNA levels also correlate with poor survival, which indicates that KLK13 mRNA expression may be a potential prognostic marker, although it could not be an independent prognostic factor by multivariate analysis. In vitro experiments of the OSCC cell lines KYSE150 and KYSE450 demonstrated that overexpression of KLK13 inhibits cell invasion and migration. Thus, KLK13 is a unique novel molecule useful for monitoring OSCC progression. Full elucidation of the role of KLK13 in OSCC may reveal avenues for investigating the molecule's functional potential as a novel therapeutic drug for targeting OSCC.

3D-quantitative structure–activity relationship and docking studies of coumarin derivatives as tissue kallikrein 7 inhibitors

Objectives

Kallikrein 7 (KLK7) is a secreted serine protease that plays important roles in skin desquamation and tumour progression, which makes it an attracting drug target. To guide the design of KLK7 inhibitors, a series of coumarin-based inhibitors were used to perform 3D-quantitative structure–activity relationship analysis.

Methods

3D conformations of 37 inhibitors were generated and used to construct CoMFA and CoMSIA models. Then a complex model between the inhibitors and KLK7 was built with molecular docking.

Key findings

With the training set, the CoMFA and CoMSIA models achieved q2 values of 0.521 and 0.498, and r2 values of 0.942 and 0.983, respectively. With the testing set, the predicted r2 values were 0.663 and 0.669, respectively, for CoMFA and CoMSIA. 3D contour maps from these two models identified steric and hydrophobic interactions as the most important molecular features of these inhibitors. Furthermore, molecular docking study was performed to understand the binding modes between these compounds and KLK7, in which the critical steric and hydrophobic interactions between the inhibitors and KLK7 were confirmed.

Conclusions

Steric and hydrophobic interactions are critical in the efficient binding of KLK7 inhibitors. Our analysis would provide a meaningful guideline for the rational design of novel KLK7 inhibitors.

Novel RNA variants in colorectal cancers

With an annual estimated incidence of 1.4 million, and a five-year survival rate of 60%, colorectal cancer (CRC) is a major clinical burden. To identify novel RNA variants in CRC, we analyzed exon-level microarray expression data from a cohort of 202 CRCs. We nominated 25 genes with increased expression of their 3′ parts in at least one cancer sample each. To efficiently investigate underlying transcript structures, we developed an approach using rapid amplification of cDNA ends followed by high throughput sequencing (RACE-seq). RACE products from the targeted genes in 23 CRC samples were pooled together and sequenced. We identified VWA2-TCF7L2, DHX35-BPIFA2 and CASZ1-MASP2 as private fusion events, and novel transcript structures for 17 of the 23 other candidate genes. The high-throughput approach facilitated identification of CRC specific RNA variants. These include a recurrent read-through fusion transcript between KLK8 and KLK7, and a splice variant of S100A2. Both of these were overrepresented in CRC tissue and cell lines from external RNA-seq datasets.

Downregulated KLK13 expression in bladder cancer highlights tumor aggressiveness and unfavorable patients' prognosis

PURPOSE

Despite recent research advantages on the molecular and subcellular background, bladder cancer (BlCa) remains a clinically neglected malignancy. This is strongly reflected by the generic approach of disease diagnosis and management. Additionally, patients' prognosis became a rather demanding task due to the great disease heterogeneity. Here, we aimed to evaluate, for the first time, the clinical value of KLK13 in BlCa.

METHODS

A total of 279 bladder specimens (137 tumors, 107 adjacent normal tissues and 35 healthy samples) were included. Total RNA was extracted, reverse transcribed, and KLK13 expression was assessed by quantitative real-time PCR.

RESULTS

KLK13 expression is significantly increased in bladder tumors compared to normal adjacent epithelium. However, reduced KLK13 expression is correlated with disease aggressiveness, including higher tumor stage and grade, and high-risk TaT1 tumors according to the EORTC stratification. Moreover, Kaplan-Meier and Cox regression analysis highlighted the prognostic value of the reduced KLK13 expression for the prediction of TaT1 patients' recurrence and shorter disease-free survival following TURBT. Finally, the combination of KLK13 expression with EORTC-risk stratification results to an improved prediction of TaT1 patients' outcome.

CONCLUSION

This first clinical study of KLK13 in BlCa reveals its deregulated expression in bladder tumors and highlights KLK13 as a promising marker for improving TaT1 patients' prognosis following treatment.

Development of Monoclonal Antibodies and Characterization of an ELISA Platform Against Kallikrein-Related Peptidase 6 as a Tumor Biomarker

Kallikrein-related peptidase 6 (KLK6) is a serine protease, and one of fifteen kallikrein members located on chromosome 19. KLK6 is associated with the regulation of axonal growth following spinal injury, tumor cell metastasis, and alpha synuclein aggregate pathologies like Parkinson's, making KLK6 a potentially important biomarker. We generated a KLK6 expression vector for large-scale expression in Escherichia coli. After affinity chromatography purification and SDS-PAGE confirmation, mice were immunized with the purified protein for development of monoclonal B cell populations. Our immunizations generated five hybridomas (1D8, 2E3, 3B7, 5G8, and 5H12) against KLK6. Isotyping analysis revealed that clone 2E3 was IgG2b, while the other four clones were IgG1. Further studies found that clone 5G8 could be used to visualize specific KLK6 bands by Western blot analysis from ovarian cancer patient serum and plasma, and also in mouse liver lysates. Finally, we established a sandwich ELISA pair and determined their sensitivity for KLK6 to be 10 ng/mL. These findings establish an essential tool for the detection and analysis of KLK6.

Microarray Analysis of Long Non-coding RNA Expression Profile Associated with 5-Fluorouracil-Based Chemoradiation Resistance in Colorectal Cancer Cells

BACKGROUND

Preoperative 5-fluorouracil (5-FU)-based chemoradiotherapy is a standard treatment for locally advanced colorectal cancer (CRC). However, CRC cells often develop chemoradiation resistance (CRR). Recent studies have shown that long non-coding RNA (lncRNA) plays critical roles in a myriad of biological processes and human diseases, as well as chemotherapy resistance. Since the roles of lncRNAs in 5-FU-based CRR in human CRC cells remain unknown, they were investigated in this study.

MATERIALS AND METHODS

A 5-FU-based concurrent CRR cell model was established using human CRC cell line HCT116. Microarray expression profiling of lncRNAs and mRNAs was undertaken in parental HCT116 and 5-FU-based CRR cell lines.

RESULTS

In total, 2,662 differentially expressed lncRNAs and 2,398 mRNAs were identified in 5-FU-based CRR HCT116 cells when compared with those in parental HCT116. Moreover, 6 lncRNAs and 6 mRNAs found to be differentially expressed were validated by quantitative real time PCR (qRT-PCR). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis for the differentially expressed mRNAs indicated involvement of many, such as Jak- STAT, PI3K-Akt and NF-kappa B signaling pathways. To better understand the molecular basis of 5-FU-based CRR in CRC cells, correlated expression networks were constructed based on 8 intergenic lncRNAs and their nearby coding genes.

CONCLUSIONS

Changes in lncRNA expression are involved in 5-FU-based CRR in CRC cells. These findings may provide novel insight for the prognosis and prediction of response to therapy in CRC patients.

The kallikrein-related peptidase family: Dysregulation and functions during cancer progression

Cancer is the second leading cause of death with 14 million new cases and 8.2 million cancer-related deaths worldwide in 2012. Despite the progress made in cancer therapies, neoplastic diseases are still a major therapeutic challenge notably because of intra- and inter-malignant tumour heterogeneity and adaptation/escape of malignant cells to/from treatment. New targeted therapies need to be developed to improve our medical arsenal and counter-act cancer progression. Human kallikrein-related peptidases (KLKs) are secreted serine peptidases which are aberrantly expressed in many cancers and have great potential in developing targeted therapies. The potential of KLKs as cancer biomarkers is well established since the demonstration of the association between KLK3/PSA (prostate specific antigen) levels and prostate cancer progression. In addition, a constantly increasing number of in vitro and in vivo studies demonstrate the functional involvement of KLKs in cancer-related processes. These peptidases are now considered key players in the regulation of cancer cell growth, migration, invasion, chemo-resistance, and importantly, in mediating interactions between cancer cells and other cell populations found in the tumour microenvironment to facilitate cancer progression. These functional roles of KLKs in a cancer context further highlight their potential in designing new anti-cancer approaches. In this review, we comprehensively review the biochemical features of KLKs, their functional roles in carcinogenesis, followed by the latest developments and the successful utility of KLK-based therapeutics in counteracting cancer progression.

KLK11 mRNA expression predicts poor disease-free and overall survival in colorectal adenocarcinoma patients

BACKGROUND

Dysregulated expression of several KLK family members has been observed in colorectal adenocarcinoma. In the present study, the prognostic value of KLK11 mRNA expression as a molecular tissue biomarker in colorectal adenocarcinoma was examined.

MATERIALS & METHODS

Using quantitative real-time PCR, KLK11 mRNA expression was studied in 120 cancerous and 41 paired noncancerous colorectal specimens obtained from 120 patients with primary colorectal adenocarcinoma.

RESULTS

A significant upregulation of KLK11 transcripts in colorectal tumors was observed. KLK11 mRNA expression was associated with the depth of tumor invasion and the histological grade. Furthermore, KLK11 mRNA expression predicted poor disease-free and overall survival, independently of patient gender, age, tumor size, location, histological subtype, grade, venous invasion, lymphatic invasion, TNM stage, radiotherapy and chemotherapy treatment.

CONCLUSION

KLK11 mRNA expression could be considered as a new molecular prognostic biomarker in colorectal adenocarcinoma, with additional prognostic value in patients with highly invasive tumors and/or positive lymph nodes.

Kallikrein-related peptidase 7 (KLK7) is a proliferative factor that is aberrantly expressed in human colon cancer

Emerging evidence indicates that serine proteases of the tissue kallikrein-related peptidases family (KLK) are implicated in tumorigenesis. We recently reported the ectopic expression of KLK4 and KLK14 in colonic cancers and their signaling to control cell proliferation. Human tissue kallikrein-related peptidase 7 (KLK7) is often dysregulated in many cancers; however, its role in colon tumorigenesis has not yet been established. In the present study, we analyzed expression of KLK7 in 15 colon cancer cell lines and in 38 human colonic tumors. In many human colon cancer cells, KLK7 mRNA was observed, which leads to KLK7 protein expression and secretion. Furthermore, KLK7 was detected in human colon adenocarcinomas, but it was absent in normal epithelia. KLK7 overexpression in HT29 colon cancer cells upon stable transfection with a KLK7 expression plasmid resulted in increased cell proliferation. Moreover, subcutaneous inoculation of transfected cells into nude mice led to increased tumor growth that was associated with increased tumor cell proliferation as reflected by a positive Ki-67 staining. Our results demonstrate the aberrant expression of KLK7 in colon cancer cells and tissues and its involvement in cell proliferation in vitro and in vivo. Thus, KLK7 may represent a potential therapeutic target for human colon tumorigenesis.

Kallikrein-related peptidase 6 (KLK6) expression in the progression of colon adenoma to carcinoma

KLK6 is a secreted trypsin-like serine protease. KLK6 mRNA expression and its association with colon cancer (CC) progression was studied using quantitative real-time PCR. We examined the expression of KLK6 in 232 colon tissues (cancerous, non-cancerous, and adenomatous). We proved that KLK6 expression in CC behaves as a continuous variable, as its expression correlates significantly with increasing tumor stage (p=0.004) and histological grade (p=0.007). Interestingly, the expression of KLK6 in adenomas was significantly higher than that in the cancerous or non-cancerous tissues examined (p<0.001). Cox proportional hazard regression model using univariate analysis revealed that positive KLK6 expression is a significant factor for disease-free survival (DFS) (p=0.017) and overall survival (OS) (p=0.002) of patients. Kaplan-Meier survival curves demonstrated that KLK6-negative expression is significantly associated with longer DFS (p=0.009) and OS (p=0.001). ROC analysis showed that KLK6 expression has significant discriminatory power in distinguishing cancerous from non-cancerous colon tissues (p<0.001), or cancerous from adenoma tissues (p=0.001), or adenoma from non-cancerous colon tissues (p<0.001). Additionally, strong KLK6 immunostaining was seen in the cancer cells of selected CC sections, as well as in glandular cells and inflammatory cells of adenomas. In conclusion, KLK6 may represent a potential unfavorable prognostic biomarker for CC.

Predictions for the future of kallikrein-related peptidases in molecular diagnostics

Kallikrein-related peptidases (KLKs) form a cancer-related ensemble of serine proteases. This multigene family hosts the most widely used cancer biomarker that is PSA-KLK3, with millions of tests performed annually worldwide. The present report provides an overview of the biomarker potential of the extended KLK family (KLK1-KLK15) in various disease settings and envisages approaches that could lead to additional KLK-driven applications in future molecular diagnostics. Particular focus is given on the inclusion of KLKs into multifaceted cancer biomarker panels that provide enhanced diagnostic, prognostic and/or predictive accuracy in several human malignancies. Such panels have been described so far for prostate, ovarian, lung and colorectal cancers. The role of KLKs as biomarkers in non-malignant disease settings, such as Alzheimer's disease and multiple sclerosis, is also commented upon. Predictions are given on the challenges and future directions regarding clinically oriented KLK research.

Kallikrein-related peptidase-6 (KLK6) mRNA expression is an independent prognostic tissue biomarker of poor disease-free and overall survival in colorectal adenocarcinoma

Members of the family of tissue kallikrein and kallikrein-related peptidases possess important prognostic value in cancer. Moreover, the oncogenic role of kallikrein-related peptidase-6 (KLK6) in colorectal cancer has been well documented so far. This study investigated the prognostic value of KLK6 mRNA expression as a molecular tissue biomarker in colorectal adenocarcinoma. For this purpose, KLK6 mRNA expression was studied in 110 primary colorectal adenocarcinomas and 39 paired noncancerous colorectal specimens. A dramatic upregulation of KLK6 mRNA expression was observed in colorectal tumors. KLK6 mRNA overexpression was associated with high depth of tumor invasion, presence of distant metastases, and tumor-node-metastasis (TNM) stage of patients. Furthermore, KLK6 mRNA expression was shown to predict poor disease-free and overall survival independently of patient gender, age, tumor size, location, histological subtype, grade, venous invasion, lymphatic invasion, TNM stage, radiotherapy, and chemotherapy treatment. Moreover, Kaplan-Meier survival analysis revealed that colorectal adenocarcinoma patients with negative regional lymph nodes (N0) and those without distant metastases (M0) harboring KLK6 mRNA-positive colorectal tumors tended to relapse and die earlier than N0 and M0 patients with KLK6 mRNA-negative colorectal adenocarcinoma. Thus, KLK6 mRNA expression could be considered as an independent, unfavorable molecular prognostic biomarker in colorectal adenocarcinoma, with additional prognostic value in patients without regional or distant metastases.

Overexpression of kallikrein gene 10 is a biomarker for predicting poor prognosis in gastric cancer

AIM: To analyze the expression of kallikrein gene 10 (KLK10) in gastric cancer and to determine whether KLK10 has independent prognostic value in gastric cancer.

METHODS: We studied KLK10 expression in 80 histologically confirmed gastric cancer samples using real-time quantitative reverse transcription-PCR and hK10 expression using immunohistochemistry. Correlations with clinicopathological variables (lymph node metastasis, depth of invasion and histology) and with outcomes (disease-free survival and overall survival) during a median follow-up period of 31 mo were assessed. Gastric cancer tissues were then classified as KLK10 positive or negative.

RESULTS: KLK10 was found to be highly expressed in 57/80 (70%) of gastric cancer samples, while its expression was very low in normal gastric tissues. Positive relationships between KLK10 expression and lymph node metastasis (P = 0.048), depth of invasion (P = 0.034) and histology (P = 0.015) were observed. Univariate survival analysis revealed that gastric cancer patients with positive KLK10 expression had an increased risk for relapse/metastasis and death (P = 0.005 and 0.002, respectively). Cox multivariate analysis indicated that KLK10 was an independent prognostic indicator of disease-free survival and overall survival in patients with gastric cancer.

CONCLUSION: KLK10 expression is an independent biomarker of unfavorable prognosis in patients with gastric cancer.

The kinin-kallikrein system: physiological roles, pathophysiology and its relationship to cancer biomarkers

The kinin-kallikrein system (KKS) is an endogenous multiprotein cascade, the activation of which leads to triggering of the intrinsic coagulation pathway and enzymatic hydrolysis of kininogens with the consequent release of bradykinin-related peptides. This system plays a crucial role in inflammation, vasodilation, smooth muscle contraction, cardioprotection, vascular permeability, blood pressure control, coagulation and pain. In this review, we will outline the physiology and pathophysiology of the KKS and also highlight the association of this system with carcinogenesis and cancer progression.

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.

Kallikrein-related peptidases (KLKs) in gastrointestinal cancer: mechanistic and clinical aspects

The human tissue kallikrein (KLK1) and kallikrein-related peptidases (KLKs) are secreted serine proteases with diverse expression patterns and physiological roles in different systems, including the digestive system. The aberrant expression of KLKs in gastrointestinal malignancies as well as their implication in carcinogenesis including cell growth regulation, angiogenesis, invasion, and metastasis, has prompted scientists to investigate their potential as cancer biomarkers. Expression of distinct KLKs is associated with various clinic-pathological parameters of patients with gastric, colorectal, pancreatic, hepatic, and esophageal cancer. Moreover, several KLKs possess significant favourable or unfavourable prognostic value in these human malignancies. Identification of novel diagnostic, prognostic and predictive biomarkers will contribute utmost to clinical decision-making, since early diagnosis of gastrointestinal cancer and early detection of recurrence following surgery are critical for the effective treatment of patients and for a positive clinical outcome. The current review provides a brief overview of the functional role of KLKs in gastric, colorectal, pancreatic, hepatic, and esophageal cancer, and describes the current status of KLKs as potential tumour biomarkers in these human malignancies.

Parallel overexpression and clinical significance of kallikrein-related peptidases 7 and 14 (KLK7KLK14) in colon cancer

Currently available colon cancer (CC) markers lack sensitivity and specificity. Kallikrein-related peptidases (KLKs) present a new class of biomarkers under investigation for diverse diseases, including cancer. KLKs are co-expressed in various tissues participating in proteolytic cascades. KLK7 in human tumours facilitates metastasis by degrading components of the extracellular matrix. KLK14 promotes tumourigenesis by activating proteinase-activated receptors. In the present study we examined the concomitant expression of KLK7 and KLK14 in245 colonic tissue specimens from 175 patients; 70 were pairs of cancerous-normal tissues, 31 were cancerous tissues and 74 were colonic adenomas. We used quantitative real-time PCR and proved that both genes are up-regulated in CC at the mRNA level. Receiver-operating characteristic (ROC) analysis of our results showed that both genes have discriminatory value between CC and adenoma tissues, with KLK14 obtaining greater distinguishing power (area under the curve [AUC]=0.708 for KLK14; AUC=0.669 for KLK7). Current work showed that the two genes are fairly co-expressed in all three types of colon tissues examined (normal rs=0.667, p<0.001, adenomas rs=0.373, p=0.001, carcinomas rs=0.478, p<0.001). KLK14 is associated with shorter disease-free survival (DFS) and overall survival (OS) of patients (p=0.003, p=0.016 respectively), whereas KLK7only with shorter DFS (p=0.004). KLK7 and KLK14 gene expression can be regarded as markers of poor prognosis for CC patients with discriminating power between CC and adenoma patients.

Kallikrein-related peptidase 4 (KLK4) mRNA predicts short-term relapse in colorectal adenocarcinoma patients

The members of the kallikrein-related peptidase (KLK) family are aberrantly expressed in cancer, including colorectal adenocarcinoma. KLK4 is an endogenous activator of protease-activated receptor 1 (PAR1) in HT-29 colorectal adenocarcinoma cells, inducing PAR1 signaling and subsequent ERK1/2 activation. The aim of this study was to analyze KLK4 mRNA expression in colorectal adenocarcinoma and to examine its prognostic value as a novel molecular tissue biomarker in this malignancy. Therefore, total RNA was isolated from primary tumors of 81 colorectal adenocarcinoma patients, cDNA was prepared, and KLK4 mRNA expression analysis was performed using quantitative real-time PCR. KLK4 mRNA was significantly associated with the Dukes stage, tumor invasion, size, and histological grade. Survival analysis demonstrated that KLK4 mRNA expression constitutes an unfavorable prognostic biomarker in colorectal adenocarcinoma, predicting poor disease-free survival (DFS), independently of the nodal status and tumor size. Furthermore, KLK4 mRNA predicts short-term relapse of lymph node-negative patients or those with tumors of early Dukes stage. In conclusion, KLK4 mRNA expression can be regarded as a novel potential tissue biomarker in colorectal adenocarcinoma.

Lymph node tissue kallikrein-related peptidase 6 mRNA: a progression marker for colorectal cancer

Background:

A most important characteristic feature for poor prognosis in colorectal cancer (CRC) is the presence of lymph node metastasis. Determination of carcinoembryonic antigen (CEA) mRNA levels in lymph nodes has proven powerful for quantification of disseminated tumour cells. Here, we investigate the utility of human tissue kallikrein-related peptidase 6 (KLK6) mRNA as a progression biomarker to complement CEA mRNA, for improved selection of patients in need of adjuvant therapy and intensified follow-up after surgery.

Methods:

Lymph nodes of pTNM stage I-IV CRC- (166 patients/503 lymph nodes) and control (23/108) patients were collected at surgery and analysed by quantitative RT–PCR.

Results:

Lymph node KLK6 positivity was an indicator of poor outcome (hazard ratio 3.7). Risk of recurrence and cancer death increased with KLK6 lymph node levels. Patients with KLK6 lymph node levels above the 90th percentile had a hazard ratio of 6.5 and 76 months shorter average survival time compared to patients with KLK6 negative nodes. The KLK6 positivity in lymph nodes with few tumour cells, that is, low CEA mRNA levels, also indicated poor prognosis (hazard ratio 2.8).

Conclusion:

In CRC patients, lymph node KLK6 positivity indicated presence of aggressive tumour cells associated with poor prognosis and high risk of tumour recurrence.

Expression of kallikrein-related peptidase 7 predicts poor prognosis in patients with unresectable pancreatic ductal adenocarcinoma

BACKGROUND

Kallikrein-related peptidase 7 (KLK7) is overexpressed in pancreatic ductal adenocarcinomas (PDAC). The aims of this study were to examine the expression of KLK7 during progression of pancreatic intraepithelial neoplasia (PanIN) to invasive PDAC and to assess its prognostic significance for PDAC.

METHODS

Immunohistochemistry was used to assess KLK7 expression using a tissue microarray (TMA) and full sections of pancreatic tissue containing normal tissue, PanIN, and invasive adenocarcinoma, and the association between KLK7 expression and prognosis was examined by a population-based pancreatic cancer TMA.

RESULTS

Normal pancreatic epithelium was negative for KLK7 in either TMAs or full sections. Analysis by TMAs showed that 91% of cases showed KLK7 positivity in the adenocarcinoma component, which was significantly higher than PanIN 2/3. In full tissue sections of PDAC, KLK7 expression was detected in less than 1% of cells among PanIN 1A lesions, and increased with grade among PanIN 1B and PanIN2/3 lesions before reaching 69% in the invasive PDAC. In patients with unresected PDAC, KLK7 positivity was significantly associated with shorter overall survival.

CONCLUSIONS

Aberrant KLK7 expression starts in intermediate-to-late stages of PanIN progression, and KLK7-positive staining is associated with almost a three-fold increase in mortality rate of patients with unresected PDAC.

IMPACT

The association of KLK7 expression and poor outcome of patients with unresectable PDAC suggests that inhibiting either KLK7 expression and/or activity could be a therapeutic strategy. Because the vast majority of patients present with unresectable disease, such an intervention could have a significant impact upon the overall survival of this patient population.

Kallikrein-related peptidase signaling in colon carcinoma cells: targeting proteinase-activated receptors

We hypothesized that kallikrein-related peptidase 14 (KLK14) is produced by colonic tumors and can promote tumorigenesis by activating proteinase-activated receptors (PARs). We found that KLK14 is expressed in human colon adenocarcinoma cells but not in adjacent cancer-free tissue; KLK14 mRNA, present in colon cancer, leads to KLK14 protein expression and secretion; and KLK14 signals viaPAR-2 in HT-29 cells to cause (1) receptor activation/internalization, (2) increases in intracellular calcium, (3) stimulation of ERK1/2/MAP kinase phosphorylation, and (4) cell proliferation. We suggest that KLK14, acting via PAR-2, represents an autocrine/paracrine regulator of colon tumorigenesis.

Evaluation and prognostic significance of human tissue kallikrein-related peptidase 10 (KLK10) in colorectal cancer

The prognosis of patients with colorectal cancer (CRC) is assessed through conventional clinicopathological parameters, which are not always accurate. Members of the human kallikrein-related peptidases gene family represent potential cancer biomarkers. The aim of this study was to investigate the expression of human tissue kallikrein-related peptidase 10 (KLK10) by immunohistochemistry in CRC, to correlate this expression with various histopathological and clinical variables, and to evaluate its significance as a predictor of disease outcome. KLK10 expression was evaluated by immunohistochemistry and a combined expression score was calculated for each case based on intensity and percentage of positivity. A statistically significant positive association was observed between KLK10 and tumor stage and liver metastases (p = 0.015 and p = 0.035, respectively). Paradoxically, a negative association was observed between KLK10 and tumor grade (p = 0.009). Kaplan-Meier survival curves and univariate analysis showed that both KLK10 expression and stage had statistically significant correlations with disease-free survival (DFS) (p = 0.030 and p < 0.001, respectively) and overall survival (p = 0.010 and p = 0.001, respectively). Cox multivariate analysis showed that both KLK10 expression and stage were independent predictors of unfavorable DFS (p = 0.057 and p = 0.001, respectively) and overall survival (p = 0.009 and p = 0.001, respectively). In conclusion, KLK10 immunostaining is an independent prognostic marker in patients with CRC.

Kallikrein-related peptidase 14 acts on proteinase-activated receptor 2 to induce signaling pathway in colon cancer cells

Serine proteinases participate in tumor growth and invasion by cleaving and activating proteinase-activated receptors (PARs). Recent studies have implicated PAR-1 and PAR-4 (activated by thrombin) and PAR-2 (activated by trypsin but not by thrombin) in human colon cancer growth. The endogenous activators of PARs in colon tumors, however, are still unknown. We hypothesize that the kallikrein-related peptidase (KLK) family member KLK14, a known tumor biomarker, is produced by colonic tumors and signals to human colon cancer cells by activating PARs. We found that i) KLK14 mRNA was present in 16 human colon cancer cell lines, ii) KLK14 protein was expressed and secreted in colon cancer cell lines, and iii) KLK14 (0.1 μmol/L) induced increases in intracellular calcium in HT29, a human colon cancer-derived cell line. KLK14-induced calcium flux was associated with internalization of KLK14-mediated activation of PAR-2. Furthermore, KLK14 induced significant extracellular signal-regulated kinases 1 and 2 (ERK1/2) phosphorylation and HT29 cell proliferation, presumably by activating PAR-2. A PAR-2 cleavage and activation-blocking antibody dramatically reduced KLK14-induced ERK1/2 signaling. Finally, ectopic expression of KLK14 in human colon adenocarcinomas and its absence in normal epithelia was demonstrated by IHC analysis. These results demonstrate, for the first time, the aberrant expression of KLK14 in colon cancer and its involvement in PAR-2 receptor signaling. Thus, KLK14 and its receptor, PAR-2, may represent therapeutic targets for colon tumorigenesis.

Down-regulation of kallikrein-related peptidase 5 (KLK5) expression in breast cancer patients: a biomarker for the differential diagnosis of breast lesions

Background

Kallikrein-related peptidase 5 (KLK5) is a secreted trypsin-like protease of the KLK family, encoded by the KLK5 gene. KLK5 has been found to cleave various extracellular matrix components, as well as to activate several other KLK proteases, triggering the stimulation of tissue microenvironment proteolytic cascades.

Material and Methods

KLK5 expression levels were quantified in 102 cancerous and benign breast tissue specimens, obtained by randomly chosen patients, using RT-qPCR assay. Subsequently, advanced biostatistics were applied in order to analyze the KLK5 expression profile in the two patients' cohorts and also to evaluate its clinical significance for the discrimination of breast tumors.

Results

A statistically significant (p < 0.001) down-regulation of the KLK5 expression levels were observed in the malignant specimens compared to the benign ones. Logistic regression and ROC curve analysis revealed the significant (p < 0.001) and the independent (p < 0.001) value of the KLK5 expression quantification, for the discrimination of the malignant from the benign mammary gland biopsies. Moreover, KLK5 expression levels correlate with the pre-menopausal status (p < 0.005) as well as the ER-negative staining (p = 0.028) of women with breast cancer.

Conclusions

The quantification of KLK5 expression in breast tissue biopsies may be considered as a novel and independent biomarker for the differential diagnosis between malignant and benign tumors of the mammary gland.

Identification and validation of Kallikrein-ralated peptidase 11 as a novel prognostic marker of gastric cancer based on immunohistochemistry

BACKGROUND AND OBJECTIVES

It is important to identify and validate the differentially expressed genes in gastric cancer to screen diagnostic and/or prognostic tumor markers.

METHODS

cDNA expression microarray, gene set enrichment analysis, and bioinformatics approaches were used to screen the differentially expressed genes between gastric cancer tissues and adjacent non-cancerous mucosa. A novel candidate prognostic marker, Kallikrein-related peptidase 11 (KLK11), was validated in 400 Chinese gastric cancer patients. KLK11 expression in gastric cancer tissues was detected using real-time PCR and Western blot. KLK11 protein expression was further analyzed by immunostaining on tissue microarray, followed with clinicopathological significance and survival analysis.

RESULTS

KLK11 expression was significantly decreased in gastric cancer compared with that in normal gastric mucosa (P<0.001). Furthermore, KLK11 expression was much lower in poorly differentiated cancer samples than that in well-differentiated group (P<0.01). Survival analysis showed that negative KLK11 expression was associated with nearly fivefold increased risk of distant metastasis after curative gastrectomy (HR 4.65, P<0.01). Multivariate Cox regression analysis showed that KLK11 expression emerged as a significant independent prognostic factor for disease-free survival and overall survival (P<0.05).

CONCLUSIONS

The results indicated that KLK11 expression was decreased in gastric cancer and might serve as a novel independent prognostic marker.

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.

A Boolean-based systems biology approach to predict novel genes associated with cancer: Application to colorectal cancer

Background

Cancer has remarkable complexity at the molecular level, with multiple genes, proteins, pathways and regulatory interconnections being affected. We introduce a systems biology approach to study cancer that formally integrates the available genetic, transcriptomic, epigenetic and molecular knowledge on cancer biology and, as a proof of concept, we apply it to colorectal cancer.

Results

We first classified all the genes in the human genome into cancer-associated and non-cancer-associated genes based on extensive literature mining. We then selected a set of functional attributes proven to be highly relevant to cancer biology that includes protein kinases, secreted proteins, transcription factors, post-translational modifications of proteins, DNA methylation and tissue specificity. These cancer-associated genes were used to extract 'common cancer fingerprints' through these molecular attributes, and a Boolean logic was implemented in such a way that both the expression data and functional attributes could be rationally integrated, allowing for the generation of a guilt-by-association algorithm to identify novel cancer-associated genes. Finally, these candidate genes are interlaced with the known cancer-related genes in a network analysis aimed at identifying highly conserved gene interactions that impact cancer outcome. We demonstrate the effectiveness of this approach using colorectal cancer as a test case and identify several novel candidate genes that are classified according to their functional attributes. These genes include the following: 1) secreted proteins as potential biomarkers for the early detection of colorectal cancer (FXYD1, GUCA2B, REG3A); 2) kinases as potential drug candidates to prevent tumor growth (CDC42BPB, EPHB3, TRPM6); and 3) potential oncogenic transcription factors (CDK8, MEF2C, ZIC2).

Conclusion

We argue that this is a holistic approach that faithfully mimics cancer characteristics, efficiently predicts novel cancer-associated genes and has universal applicability to the study and advancement of cancer research.

Kallikrein-related peptidase genes as promising biomarkers for prognosis and monitoring of human malignancies

Tissue kallikrein (KLK1) and the kallikrein-related peptidase (KLK2-15) genes encode for a subgroup of 15 homologous secreted serine proteases possessing numerous physiological roles, such as the regulation of blood pressure, hormone processing and tissue remodeling. The expression of KLKs is detected in a broad spectrum of human tissues where it has been found to be regulated mainly by steroids hormones. The aberrant expression of KLKs, presented in many human malignancies, highlights the significance of this gene family for early diagnosis, prognosis and monitoring of cancer patients, as it is strongly emphasized by the routine use of PSA (KLK3) for prostate cancer management. Here, we review the presently known data regarding the role of KLKs as cancer biomarkers, giving emphasis on novel information about the subject.

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

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

Clinical significance of human kallikrein7 gene expression in colorectal cancer

BACKGROUND

The human kallikrein-related peptidases (KLK) are considered important prognostic biomarkers in cancer. The aim of the current study is to demonstrate gene expression of KLK7 in colorectal cancer (CRC) and to correlate the relative KLK7 expression level with clinicopathological factors of CRC.

METHODS

KLK7 messenger RNA (mRNA) expression was examined in nine CRC cancer cell lines by real-time polymerase chain reaction. The expression levels of KLK7 mRNA in cancerous tissues (n = 136) and paired normal tissues (n = 136) of CRC patients were also examined.

RESULTS

Six of the nine cell lines expressed the KLK7 gene. KLK7 mRNA expression levels in cancer tissues were significantly higher than those in normal tissues. Multivariate analysis revealed that the KLK7 mRNA expression level in cancer was an independent prognostic factor, especially in liver metastasis.

CONCLUSIONS

We provide evidence suggesting that KLK7 mRNA expression is correlated with prognosis in CRC patients, especially in liver metastasis.

Prognostic value and biological role of the kallikrein-related peptidases in human malignancies

Cancer is a substantial health problem for the populations of the Western world. The discovery of new molecular biomarkers for diagnosis, prognosis and monitoring patients' response to therapy can aid in combating this complicated disease. The human kallikrein-related peptidases (human tissue kallikreins [KLKs]) are encoded by a continuous multigene family, located on chromosomal region 19q13.3-4. KLK3 (prostate-specific antigen) is the most efficient cancer biomarker ever employed. KLK genes are expressed abnormally in various malignancies, where they affect cancer-cell growth and metastasis. Their deregulated expression pattern, often associated with various clinicopathological characteristics of cancer patients, can be exploited, solely or within multiparametric panels, as a prognostic biomarker. Recent data illustrate that discernible molecular modulations of KLKs, occurring as a result of cancer cells' treatment with antitumor agents, may serve as new potential biomarkers, possibly predicting patients' treatment response. It is believed that KLKs might be employed in future clinical practice as novel and effective tumor markers.