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

KLK10 derived from tumor endothelial cells accelerates colon cancer cell proliferation and hematogenous liver metastasis formation

Tumor endothelial cells (TECs), which are thought to be structurally and functionally different from normal endothelial cells (NECs), are increasingly attracting attention as a therapeutic target in hypervascular malignancies. Although colorectal liver metastasis (CRLM) tumors are hypovascular, inhibitors of angiogenesis are a key drug in multidisciplinary therapy, and TECs might be involved in the development and progression of cancer. Here, we analyzed the function of TEC in the CRLM tumor microenvironment. We used a murine colon cancer cell line (CT26) and isolated TECs from CRLM tumors. TECs showed higher proliferation and migration than NECs. Coinjection of CT26 and TECs yielded rapid tumor formation in vivo. Immunofluorescence analysis showed that coinjection of CT26 and TECs increased vessel formation and Ki-67+ cells. Transcriptome analysis identified kallikrein-related peptide 10 (KLK10) as a candidate target. Coinjection of CT26 and TECs after KLK10 downregulation with siRNA suppressed tumor formation in vivo. TEC secretion of KLK10 decreased after KLK10 downregulation, and conditioned medium after KLK10 knockdown in TECs suppressed CT26 proliferative activity. Double immunofluorescence staining of KLK10 and CD31 in CRLM tissues revealed a significant correlation between poor prognosis and positive KLK10 expression in TECs and tumor cells. On multivariate analysis, KLK10 expression was an independent prognostic factor in disease-free survival. In conclusion, KLK10 derived from TECs accelerates colon cancer cell proliferation and hematogenous liver metastasis formation. KLK10 in TECs might offer a promising therapeutic target in CRLM.

KLK10 promotes the progression of KRAS mutant colorectal cancer via PAR1-PDK1-AKT signaling pathway

Kirsten rat sarcoma virus (KRAS) gene mutation is common in colorectal cancer (CRC) and is often predictive of treatment failure and poor prognosis. To understand the mechanism, we compared the transcriptome of CRC patients with wild-type and mutant KRAS and found that KRAS mutation is associated with the overexpression of a secreted serine protease, kallikrein-related peptidase 10 (KLK10). Moreover, using in vitro and in vivo models, we found that KLK10 overexpression favors the rapid growth and liver metastasis of KRAS mutant CRC and can also impair the efficacy of KRAS inhibitors, leading to drug resistance and poor survival. Further functional assays revealed that the oncogenic role of KLK10 is mediated by protease-activated receptor 1 (PAR1). KLK10 cleaves and activates PAR1, which further activates 3-phosphoinositide-dependent kinase 1 (PDK1)-AKT oncogenic pathway. Notably, suppressing PAR1-PDK1-AKT cascade via KLK10 knockdown can effectively inhibit CRC progression and improve the sensitivity to KRAS inhibitor, providing a promising therapeutic strategy. Taken together, our study showed that KLK10 promotes the progression of KRAS mutant CRC via activating PAR1-PDK1-AKT signaling pathway. These findings expanded our knowledge of CRC development, especially in the setting of KRAS mutation, and also provided novel targets for clinical intervention.

Identifying Biomarkers Using Support Vector Machine to Understand the Racial Disparity in Triple-Negative Breast Cancer

With the properties of aggressive cancer and heterogeneous tumor biology, triple-negative breast cancer (TNBC) is a type of breast cancer known for its poor clinical outcome. The lack of estrogen, progesterone, and human epidermal growth factor receptor in the tumors of TNBC leads to fewer treatment options in clinics. The incidence of TNBC is higher in African American (AA) women compared with European American (EA) women with worse clinical outcomes. The significant factors responsible for the racial disparity in TNBC are socioeconomic lifestyle and tumor biology. The current study considered the open-source gene expression data of triple-negative breast cancer samples' racial information. We implemented a state-of-the-art classification Support Vector Machine (SVM) method with a recurrent feature elimination approach to the gene expression data to identify significant biomarkers deregulated in AA women and EA women. We also included Spearman's rho and Ward's linkage method in our feature selection workflow. Our proposed method generates 24 features/genes that can classify the AA and EA samples 98% accurately. We also performed the Kaplan-Meier analysis and log-rank test on the 24 features/genes. We only discussed the correlation between deregulated expression and cancer progression with a poor survival rate of 2 genes, KLK10 and LRRC37A2, out of 24 genes. We believe that further improvement of our method with a higher number of RNA-seq gene expression data will more accurately provide insight into racial disparity in TNBC.

Targeted and explorative profiling of kallikrein proteases and global proteome biology of pancreatic ductal adenocarcinoma, chronic pancreatitis, and normal pancreas highlights disease-specific proteome remodelling

Pancreatic ductal adenocarcinoma (PDAC) represents one of the most aggressive and lethal malignancies worldwide with an urgent need for new diagnostic and therapeutic strategies. One major risk factor for PDAC is the pre-indication of chronic pancreatitis (CP), which represents highly inflammatory pancreatic tissue. Kallikreins (KLKs) are secreted serine proteases that play an important role in various cancers as components of the tumor microenvironment. Previous studies of KLKs in solid tumors largely relied on either transcriptomics or immunodetection. We present one of the first targeted mass spectrometry profiling of kallikrein proteases in PDAC, CP, and normal pancreas. We show that KLK6 and KLK10 are significantly upregulated in PDAC (n=14) but not in CP (n=7) when compared to normal pancreas (n=16), highlighting their specific intertwining with malignancy. Additional explorative proteome profiling identified 5936 proteins in our pancreatic cohort and observed disease-specific proteome rearrangements in PDAC and CP. As such, PDAC features an enriched proteome motif for extracellular matrix (ECM) and cell adhesion while there is depletion of mitochondrial energy metabolism proteins, reminiscent of the Warburg effect. Although often regarded as a PDAC hallmark, the ECM fingerprint was also observed in CP, alongside with a prototypical inflammatory proteome motif as well as with an increased wound healing process and proteolytic activity, thereby possibly illustrating tissue autolysis. Proteogenomic analysis based on publicly accessible data sources identified 112 PDAC-specific and 32 CP-specific single amino acid variants, which among others affect KRAS and ANKHD1. Our study emphasizes the diagnostic potential of kallikreins and provides novel insights into proteomic characteristics of PDAC and CP.

KLK6/PAR1 Axis Promotes Tumor Growth and Metastasis by Regulating Cross-Talk between Tumor Cells and Macrophages

Kallikrein-related peptidase (KLK)6 is associated with inflammatory diseases and neoplastic progression. KLK6 is aberrantly expressed in several solid tumors and regulates cancer development, metastatic progression, and drug resistance. However, the function of KLK6 in the tumor microenvironment remains unclear. This study aimed to determine the role of KLK6 in the tumor microenvironment. Here, we uncovered the mechanism underlying KLK6-mediated cross-talk between cancer cells and macrophages. Compared with wild-type mice, KLK6-/- mice showed less tumor growth and metastasis in the B16F10 melanoma and Lewis lung carcinoma (LLC) xenograft model. Mechanistically, KLK6 promoted the secretion of tumor necrosis factor-alpha (TNF-α) from macrophages via the activation of protease-activated receptor-1 (PAR1) in an autocrine manner. TNF-α secreted from macrophages induced the release of the C-X-C motif chemokine ligand 1 (CXCL1) from melanoma and lung carcinoma cells in a paracrine manner. The introduction of recombinant KLK6 protein in KLK6-/- mice rescued the production of TNF-α and CXCL1, tumor growth, and metastasis. Inhibition of PAR1 activity suppressed these malignant phenotypes rescued by rKLK6 in vitro and in vivo. Our findings suggest that KLK6 functions as an important molecular link between macrophages and cancer cells during malignant progression, thereby providing opportunities for therapeutic intervention.

A KLK6 Activity-Based Probe Reveals a Role for KLK6 Activity in Pancreatic Cancer Cell Invasion

Pancreatic cancer has the lowest survival rate of all common cancers due to late diagnosis and limited treatment options. Serine hydrolases are known to mediate cancer progression and metastasis through initiation of signaling cascades and cleavage of extracellular matrix proteins, and the kallikrein-related peptidase (KLK) family of secreted serine proteases have emerging roles in pancreatic ductal adenocarcinoma (PDAC). However, the lack of reliable activity-based probes (ABPs) to profile KLK activity has hindered progress in validation of these enzymes as potential targets or biomarkers. Here, we developed potent and selective ABPs for KLK6 by using a positional scanning combinatorial substrate library and characterized their binding mode and interactions by X-ray crystallography. The optimized KLK6 probe IMP-2352 (k_obs/I = 11,000 M^-1 s^-1) enabled selective detection of KLK6 activity in a variety of PDAC cell lines, and we observed that KLK6 inhibition reduced the invasiveness of PDAC cells that secrete active KLK6. KLK6 inhibitors were combined with N-terminomics to identify potential secreted protein substrates of KLK6 in PDAC cells, providing insights into KLK6-mediated invasion pathways. These novel KLK6 ABPs offer a toolset to validate KLK6 and associated signaling partners as targets or biomarkers across a range of diseases.

KLK6 Functions as an Oncogene and Unfavorable Prognostic Factor in Bladder Urothelial Carcinoma

Background

Kallikrein-related peptidase 6 (KLK6) has been substantiated as a diagnostic, prognostic, and therapeutic molecular in several cancer types. In our study, we attempt to explore the biological functions of KLK6 in bladder urothelial carcinoma (BLCA).

Methods

KLK6 gene expression prognostic, gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), gene set enrichment analysis (GSEA), and immune infiltration were analyzed using The Cancer Genome Atlas (TCGA) database. In vitro and in vivo experimental measurements, including CCK8, transwell migration, TUNEL, and nude mouse transplanted tumor model, were used to evaluate the antineoplastic activities of KLK6 loss-of-function.

Results

The combination of bioinformatics analyses and experimental measurements demonstrate that KLK6 expression is aberrantly upregulated in human specimens and cell lines of BLCA. GO and GSEA enrichment analyses exhibited that KLK6 is implicated in the inflammatory response and immune infiltration, suggesting that upregulation of KLK6 may be associated with the progression of BLCA. Knockdown of KLK6 is able to inhibit the growth and migration and trigger apoptosis of RT4 and T24 cells. Moreover, the TCGA database indicates that KLK6 high expression in BLCA patients showed a poorer prognosis than those patients with KLK6 low expression. Univariate and multivariate regression analyses suggest KLK6 as an independent prognostic factor to predict unfavorable OS in patients with BLCA.

Conclusion

KLK6 is an independent prognostic factor and an antitumor target of BLCA. KLK6 expression positively correlates with several immune cells infiltration, indicating that inhibition of KLK6 may contribute to immunotherapy of BLCA.

Single-cell analysis of patient-derived PDAC organoids reveals cell state heterogeneity and a conserved developmental hierarchy

Pancreatic ductal adenocarcinoma (PDAC) is projected to be the second leading cause of cancer mortality by 2030. Bulk transcriptomic analyses have distinguished 'classical' from 'basal-like' tumors with more aggressive clinical behavior. We derive PDAC organoids from 18 primary tumors and two matched liver metastases, and show that 'classical' and 'basal-like' cells coexist in individual organoids. By single-cell transcriptome analysis of PDAC organoids and primary PDAC, we identify distinct tumor cell states shared across patients, including a cycling progenitor cell state and a differentiated secretory state. Cell states are connected by a differentiation hierarchy, with 'classical' cells concentrated at the endpoint. In an imaging-based drug screen, expression of 'classical' subtype genes correlates with better drug response. Our results thus uncover a functional hierarchy of PDAC cell states linked to transcriptional tumor subtypes, and support the use of PDAC organoids as a clinically relevant model for in vitro studies of tumor heterogeneity.

Kallikrein-Related Peptidase 6 Is Associated with the Tumour Microenvironment of Pancreatic Ductal Adenocarcinoma

Simple Summary

Kallikrein-related peptidases have tumour-biological roles and are dysregulated in many cancers. Only a few studies have reported their upregulation in pancreatic cancer and linked them to poor prognosis. By interrogating publicly available and our own datasets, we studied their expression in patient-derived tissues and pancreatic cancer cells. We found several kallikrein-related peptidases that were upregulated, in particular kallikrein-related peptidase 6 at the forefront of the tumour area. We then tested the effect of a kallikrein-related peptidase 6 inhibitor on cancer cell functions. Because the majority of patients present with inoperable disease, a targeted therapeutic intervention may have a positive impact on the survival of this patient population.

Abstract

As cancer-associated factors, kallikrein-related peptidases (KLKs) are components of the tumour microenvironment, which represents a rich substrate repertoire, and considered attractive targets for the development of novel treatments. Standard-of-care therapy of pancreatic cancer shows unsatisfactory results, indicating the need for alternative therapeutic approaches. We aimed to investigate the expression of KLKs in pancreatic cancer and to inhibit the function of KLK6 in pancreatic cancer cells. KLK6, KLK7, KLK8, KLK10 and KLK11 were coexpressed and upregulated in tissues from pancreatic cancer patients compared to normal pancreas. Their high expression levels correlated with each other and were linked to shorter survival compared to low KLK levels. We then validated KLK6 mRNA and protein expression in patient-derived tissues and pancreatic cancer cells. Coexpression of KLK6 with KRT19, αSMA or CD68 was independent of tumour stage, while KLK6 was coexpressed with KRT19 and CD68 in the invasive tumour area. High KLK6 levels in tumour and CD68+ cells were linked to shorter survival. KLK6 inhibition reduced KLK6 mRNA expression, cell metabolic activity and KLK6 secretion and increased the secretion of other serine and aspartic lysosomal proteases. The association of high KLK levels and poor prognosis suggests that inhibiting KLKs may be a therapeutic strategy for precision medicine.

Molecular Pathways Associated with Kallikrein 6 Overexpression in Colorectal Cancer

Colorectal cancer (CRC) remains one of the leading causes of cancer-related death worldwide. The high mortality of CRC is related to its ability to metastasize to distant organs. The kallikrein-related peptidase Kallikrein 6 (KLK6) is overexpressed in CRC and contributes to cancer cell invasion and metastasis. The goal of this study was to identify KLK6-associated markers for the CRC prognosis and treatment. Tumor Samples from the CRC patients with significantly elevated KLK6 transcript levels were identified in the RNA-Seq data from Cancer Genome Atlas (TCGA) and their expression profiles were evaluated using Gene Ontology (GO), Phenotype and Reactome enrichment, and protein interaction methods. KLK6-high cases had a distinct spectrum of mutations in titin (TTN), APC, K-RAS, and MUC16 genes. Differentially expressed genes (DEGs) found in the KLK6-overexpressing CRCs were associated with cell signaling, extracellular matrix organization, and cell communication regulatory pathways. The top KLK6-interaction partners were found to be the members of kallikrein family (KLK7, KLK8, KLK10), extracellular matrix associated proteins (keratins, integrins, small proline rich repeat, S100A families) and TGF-β, FOS, and Ser/Thr protein kinase signaling pathways. Expression of selected KLK6-associated genes was validated in a subset of paired normal and tumor CRC patient-derived organoid cultures. The performed analyses identified KLK6 itself and a set of genes, which are co-expressed with KLK6, as potential clinical biomarkers for the management of the CRC disease.

Transcriptomic Analysis of Laser Capture Microdissected Tumors Reveals Cancer- and Stromal-Specific Molecular Subtypes of Pancreatic Ductal Adenocarcinoma

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) lethality is multifactorial; although studies have identified transcriptional and genetic subsets of tumors with different prognostic significance, there is limited understanding of features associated with the minority of patients who have durable remission after surgical resection. In this study, we performed laser capture microdissection (LCM) of PDAC samples to define their cancer- and stroma-specific molecular subtypes and identify a prognostic gene expression signature for short-term and long-term survival.

EXPERIMENTAL DESIGN

LCM and RNA sequencing (RNA-seq) analysis of cancer and adjacent stroma of 19 treatment-naïve PDAC tumors was performed. Gene expression signatures were tested for their robustness in a large independent validation set. An RNA-ISH assay with pooled probes for genes associated with disease-free survival (DFS) was developed to probe 111 PDAC tumor samples.

RESULTS

Gene expression profiling identified four subtypes of cancer cells (C1-C4) and three subtypes of cancer-adjacent stroma (S1-S3). These stroma-specific subtypes were associated with DFS (P = 5.55E-07), with S1 associated with better prognoses when paired with C1 and C2. Thirteen genes were found to be predominantly expressed in cancer cells and corresponded with DFS in a validation using existing RNA-seq datasets. A second validation on an independent cohort of patients using RNA-ISH probes to six of these prognostic genes demonstrated significant association with overall survival (median 17 vs. 25 months; P < 0.02).

CONCLUSIONS

Our results identified specific signatures from the epithelial and the stroma components of PDAC, which add clarity to the nature of PDAC molecular subtypes and may help predict survival.

Cysteine depletion induces pancreatic tumor ferroptosis in mice

Ferroptosis is a form of cell death that results from the catastrophic accumulation of lipid reactive oxygen species (ROS). Oncogenic signaling elevates lipid ROS production in many tumor types and is counteracted by metabolites that are derived from the amino acid cysteine. In this work, we show that the import of oxidized cysteine (cystine) via system x_C ^- is a critical dependency of pancreatic ductal adenocarcinoma (PDAC), which is a leading cause of cancer mortality. PDAC cells used cysteine to synthesize glutathione and coenzyme A, which, together, down-regulated ferroptosis. Studying genetically engineered mice, we found that the deletion of a system x_C ^- subunit, Slc7a11, induced tumor-selective ferroptosis and inhibited PDAC growth. This was replicated through the administration of cyst(e)inase, a drug that depletes cysteine and cystine, demonstrating a translatable means to induce ferroptosis in PDAC.

Identification of Prognostic Biomarkers and Drugs Targeting Them in Colon Adenocarcinoma: A Bioinformatic Analysis

Objective: To identify prognostic biomarkers and drugs that target them in colon adenocarcinoma (COAD) based on the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus databases. Methods: The TCGA dataset was used to identify the top 50 upregulated differentially expressed genes (DEGs), and Gene Expression Omnibus profiles were used for validation. Survival analyses were conducted with the TCGA dataset using the RTCGAToolbox package in the R software environment. Drugs targeting the candidate prognostic biomarkers were searched in the DrugBank and herbal databases. Results: Among the top 50 upregulated DEGs in patients with COAD in the TCGA dataset, the Wnt signaling pathway and cytokine-cytokine receptor interactions and pathways in cancer Kyoto Encyclopedia of Genes and Genomes pathway analysis were enriched in DEGs. Tissue development and regulation of cell proliferation were the main Gene Ontology biological processes associated with upregulated DEGs. MYC and KLK6 were overexpressed in tumors validated in the TCGA, GSE41328, and GSE113513 databases (all P < .001) and were significantly associated with overall survival in patients with COAD (P = .021 and P = .047). Nadroparin and benzamidine were identified as inhibitors of MYC and KLK6 in DrugBank, and 8 herbs targeting MYC, including Da Huang (Radix Rhei Et Rhizome), Hu Zhang (Polygoni Cuspidati Rhizoma Et Radix), Huang Lian (Coptidis Rhizoma), Ban Xia (Arum Ternatum Thunb), Tu Fu Ling (Smilacis Glabrae Rhixoma), Lei Gong Teng (Tripterygii Radix), Er Cha (Catechu), and Guang Zao (Choerospondiatis Fructus), were identified. Conclusion: MYC and KLK6 may serve as candidate prognostic predictors and therapeutic targets in patients with COAD.

PAR1 signaling on tumor cells limits tumor growth by maintaining a mesenchymal phenotype in pancreatic cancer

Protease activated receptor-1 (PAR1) expression is associated with disease progression and overall survival in a variety of cancers. However, the importance of tumor cell PAR1 in pancreatic ductal adenocarcinomas (PDAC) remains unexplored. Utilizing orthotopic models with wild type and PAR1-targeted PDAC cells, we show that tumor cell PAR1 negatively affects PDAC growth, yet promotes metastasis. Mechanistically, we show that tumor cell-specific PAR1 expression correlates with mesenchymal signatures in PDAC and that PAR1 is linked to the maintenance of a partial mesenchymal cell state. Indeed, loss of PAR1 expression results in well-differentiated pancreatic tumors in vivo, with enhanced epithelial characteristics both in vitro and in vivo. Taken together, we have identified a novel growth inhibitory role of PAR1 in PDAC, which is linked to the induction, and maintenance of a mesenchymal-like phenotype. The recognition that PAR1 actively limits pancreatic cancer cell growth suggest that the contributions of PAR1 to tumor growth differ between cancers of epithelial origin and that its targeting should be applied with care.

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.

Aberrant upregulation of KLK10 promotes metastasis via enhancement of EMT and FAK/SRC/ERK axis in PDAC

Pancreatic Ductal Adenocarcinoma (PADC) metastasis is the leading cause of morality of this severe malignant tumor. Proteases are key players in the degradation of extracellular matrix which promotes the cascade of tumor metastasis. As a kind of serine proteases, the kallikrein family performs vital function on the cancer proteolysis scene, which have been proved in diverse malignant tumors. However, the specific member of kallikrein family and its function in PDAC remain unexplored. In this study, by data mining of GEO datasets, we have identified KLK10 is upregulated gene in PDAC. We found that KLK10 was significantly overexpressed in tissues of pancreatic intraepithelial neoplasia (PanIN) and PDAC from Pdx1-Cre; LSL-KrasG12D/+ mice (KC) and Pdx1-Cre; LSL-KrasG12D/+; LSL-Trp53R172H/+ mice (KPC) by immunohistochemical analysis. Moreover, KLK10 is extremely elevated in the PDAC tissues, especially that from the PDAC patients with lymphatic and distant metastasis. Aberrant KLK10 expression is significantly correlated with poor prognosis and shorter survival by univariable and multivariable analysis. Functionally, knockdown of KLK10 observably inhibits invasion and metastatic phenotype of PDAC cells in vitro and metastasis in vivo. In addition, blockade of KLK10 attenuates epithelial-mesenchymal transition and activation of FAK-SRC-ERK signaling, which explains the mechanism of KLK10 in promoting metastasis. Collectively, KLK10 should be considered as a promising biomarker for diagnosis and potential target for therapy in PDAC.

KLK10 exon 3 unmethylated PCR product concentration: a new potential early diagnostic marker in ovarian cancer? - A pilot study

BACKGROUND

KLK10 exon 3 hypermethylation correlated to tumor-specific lack of KLK10 expression in cancer cell lines and primary tumors. In the present study we investigate the possible role of KLK10 exon 3 methylation in ovarian tumor diagnosis and prognosis.

RESULTS

Qualitative methylation-specific PCR (MSP) results did not show statistically significant differences in patient group samples (normal and tumor) where all samples were positive only for the unmethylated-specific PCR except for two malignant samples that were either doubly positive (serous carcinoma) or doubly negative (Sertoli-Leydig cell tumor) for the two MSP tests. However, KLK10 exon 3 unmethylated PCR product concentration (ng/μl) showed statistically significant differences in benign and malignant patient group samples; mean ± SD (n): tumor: 0.077 ± 0.035 (14) and 0.047 ± 0.021 (15), respectively, p-value = 0.011; and normal: 0.094 ± 0.039 (7) and 0.046 ± 0.027 (6), respectively, p-value = 0.031. Moreover, ROC curve analysis of KLK10 exon 3 unmethylated PCR product concentration in overall patient group samples showed good diagnostic ability (AUC = 0.778; p-value = 0.002). Patient survival (living and died) showed statistically significant difference according to preoperative serum CA125 concentration (U/ml); median (n): 101.25 (10) and 1252 (5), respectively, p-value = 0.037, but not KLK10 exon 3 unmethylated PCR product concentration (ng/μl) in overall malignant patient samples; mean ± SD (n): 0.042 ± 0.015 (14) and 0.055 ± 0.032 (7), p-value = 0.228.

CONCLUSION

To the best of our knowledge, this is the first report on KLK10 exon 3 unmethylated PCR product concentration as potential early epigenetic diagnostic marker in primary ovarian tumors. Taken into account the limitations in our study (small sample size and semi-quantitative PCR product analysis) further studies are strongly recommended.

A 65‑gene signature for prognostic prediction in colon adenocarcinoma

The aim of the present study was to examine the molecular factors associated with the prognosis of colon cancer. Gene expression datasets were downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus databases to screen differentially expressed genes (DEGs) between colon cancer samples and normal samples. Survival‑related genes were selected from the DEGs using the Cox regression method. A co‑expression network of survival‑related genes was then constructed, and functional clusters were extracted from this network. The significantly enriched functions and pathways of the genes in the network were identified. Using Bayesian discriminant analysis, a prognostic prediction system was established to distinguish the positive from negative prognostic samples. The discrimination efficacy of the system was validated in the GSE17538 dataset using Kaplan‑Meier survival analysis. A total of 636 and 1,892 DEGs between the colon cancer samples and normal samples were screened from the TCGA and GSE44861 dataset, respectively. There were 155 survival‑related genes selected. The co‑expression network of survival‑related genes included 138 genes, 534 lines (connections) and five functional clusters, including the signaling pathway, cellular response to cAMP, and immune system process functional clusters. The molecular function, cellular components and biological processes were the significantly enriched functions. The peroxisome proliferator‑activated receptor signaling pathway, Wnt signaling pathway, B cell receptor signaling pathway, and cytokine‑cytokine receptor interactions were the significant pathways. A prognostic prediction system based on a 65‑gene signature was established using this co‑expression network. Its discriminatory effect was validated in the TCGA dataset (P=3.56e‑12) and the GSE17538 dataset (P=1.67e‑6). The 65‑gene signature included kallikrein‑related peptidase 6 (KLK6), collagen type XI α1 (COL11A1), cartilage oligomeric matrix protein, wingless‑type MMTV integration site family member 2 (WNT2) and keratin 6B. In conclusion, a 65‑gene signature was screened in the present study, which showed a prognostic prediction effect in colon adenocarcinoma. KLK6, COL11A1, and WNT2 may be suitable prognostic predictors for colon adenocarcinoma.

Epigenetic regulation of KLK7 gene expression in pancreatic and cervical cancer cells

Kallikrein-related peptidase 7 (KLK7) is a serine protease encoded within the kallikrein gene cluster located on human chromosome region 19q13.3-13.4. KLK7 is overexpressed in human pancreatic ductal adenocarcinomas (PDACs), but not in normal pancreas. Examination of KLK7 mRNA levels in pancreatic cancer cell lines revealed that it is readily detected in MIA PaCa-2 and PK-1 cells, but not in Panc-1 cells. Treatment of Panc-1 cells with the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) significantly induced KLK7 mRNA expression. Similarly, KLK7 is highly expressed in cervical cancer cells, but its expression in the human cervical cancer cell line HeLa is only detected following TSA treatment. Promoter deletion analysis revealed that the proximal -238 promoter region, containing a putative Sp1-binding site, was sufficient for TSA activation of luciferase reporter activity, which was abrogated by the disruption of the Sp1-binding sequence. Consistent with the notion that TSA induced KLK7 expression via Sp1, co-expression of Sp1 with the KLK7-promoter/luciferase construct produced a significant increase in reporter activity. Chromatin immunoprecipitation (ChIP) analysis revealed enriched Sp1 occupancy on the KLK7 promoter following TSA treatment. Similarly, ChIP analysis showed the histone active mark, H3K4Me3, in the KLK7 promoter region was significantly increased after exposure to TSA.

Clinical relevance of kallikrein-related peptidase 6 (KLK6) and 8 (KLK8) mRNA expression in advanced serous ovarian cancer

Most members of the kallikrein-related peptidase family have been demonstrated to be dysregulated in ovarian cancer and modulate tumor growth, migration, invasion, and resistance to chemotherapy. In the present study, we assessed the mRNA expression levels of KLK6 and KLK8 by quantitative PCR in 100 patients with advanced serous ovarian cancer FIGO stage III/IV. A pronounced correlation between KLK6 and KLK8 mRNA expression (rs = 0.636, p < 0.001) was observed, indicating coordinate expression of both peptidases. No significant associations of clinical parameters with KLK6, KLK8, and a combined score KLK6+KLK8 were found. In univariate Cox regression analysis, elevated mRNA levels of KLK6 were significantly linked with shortened overall survival (OS) (hazard ratio [HR] = 2.07, p = 0.007). While KLK8 values were not associated with patients' outcome, high KLK6+KLK8 values were significantly associated with shorter progression-free survival (HR = 1.82, p = 0.047) and showed a trend towards significance in the case of OS (HR = 1.82, p = 0.053). Strikingly, in multivariable analysis, elevated KLK6 mRNA values, apart from residual tumor mass, remained an independent predictive marker for poor OS (HR = 2.33, p = 0.005). As KLK6 mRNA and protein levels correlate, KLK6 may represent an attractive therapeutic target for potent and specific inhibitors of its enzymatic activity.

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.

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.

Upregulated KLK10 inhibits esophageal cancer proliferation and enhances cisplatin sensitivity in vitro

The kallikrein-related peptidase 10 (KLK10) gene has tumor-suppressive function in various types of human cancer. However, previous studies showed that KLK10 also acts as an oncogene and is upregulated in gastrointestinal tumors. The role of KLK10 in human esophageal cancer (EC) remains unclear. In the present study, the expression of KLK10 in human esophageal and non-esophageal cancer tissues was investigated by immunohistochemistry. Quantitative RT-PCR and western blot analysis were utilized to detect KLK10 mRNA and protein expression in human esophageal cancer cell lines (TE-1 and Eca-109). Small interference RNA was utilized to specifically knockdown KLK10 expression in Eca-109 and TE-1 cells. Cell proliferation, cell cycle analysis as well as CDDP-dependent apoptosis were determined using a CCK-8 assay and flow cytometry. The results showed that, KLK10 was positive in 67 out of 83 (80.72%) human EC and positive in 3 out of 11 (27.27%) normal tissues (P=0.001). The present study indicated that KLK10 potentially plays a crucial role in Eca-109 cell growth. Additionally, the downregulation of KLK10 induced S-phase arrest and promoted cisplatin-induced apoptosis. The resutls of the present study suggested that KLK10 is a promising novel marker for the diagnostic and therapeutic target of esophageal cancer.

Kallikrein-related peptidase 6 regulates epithelial-to-mesenchymal transition and serves as prognostic biomarker for head and neck squamous cell carcinoma patients

Background

Dysregulated expression of Kallikrein-related peptidase 6 (KLK6) is a common feature for many human malignancies and numerous studies evaluated KLK6 as a promising biomarker for early diagnosis or unfavorable prognosis. However, the expression of KLK6 in carcinomas derived from mucosal epithelia, including head and neck squamous cell carcinoma (HNSCC), and its mode of action has not been addressed so far.

Methods

Stable clones of human mucosal tumor cell lines were generated with shRNA-mediated silencing or ectopic overexpression to characterize the impact of KLK6 on tumor relevant processes in vitro. Tissue microarrays with primary HNSCC samples from a retrospective patient cohort (n = 162) were stained by immunohistochemistry and the correlation between KLK6 staining and survival was addressed by univariate Kaplan-Meier and multivariate Cox proportional hazard model analysis.

Results

KLK6 expression was detected in head and neck tumor cell lines (FaDu, Cal27 and SCC25), but not in HeLa cervix carcinoma cells. Silencing in FaDu cells and ectopic expression in HeLa cells unraveled an inhibitory function of KLK6 on tumor cell proliferation and mobility. FaDu clones with silenced KLK6 expression displayed molecular features resembling epithelial-to-mesenchymal transition, nuclear β-catenin accumulation and higher resistance against irradiation. Low KLK6 protein expression in primary tumors from oropharyngeal and laryngeal SCC patients was significantly correlated with poor progression-free (p = 0.001) and overall survival (p < 0.0005), and served as an independent risk factor for unfavorable clinical outcome.

Conclusions

In summary, detection of low KLK6 expression in primary tumors represents a promising tool to stratify HNSCC patients with high risk for treatment failure. These patients might benefit from restoration of KLK6 expression or pharmacological targeting of signaling pathways implicated in EMT.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0381-6) contains supplementary material, which is available to authorized users.

Evaluation of human tissue kallikrein-related peptidases 6 and 10 expression in early gastroesophageal adenocarcinoma

Kallikreins are a family of serine proteases that are linked to malignancy of different body organs with potential clinical utility as tumor markers. In this study, we investigated kallikrein-related peptidase 6 (KLK6) and KLK10 expression in early gastroesophageal junction adenocarcinoma and Barrett esophagus (BE) with and without dysplasia. Immunohistochemistry revealed significantly increased KLK6 expression in early invasive cancer compared with dysplastic (P = .009) and nondysplastic BE (P = .0002). There was a stepwise expression increase from metaplasia to dysplasia and invasive tumors. Significantly higher KLK10 was seen in dysplastic lesions compared with metaplasia but not between dysplastic lesions and invasive cancers. KLK6 staining intensity was increased at the invasive front (P = .006), suggesting its role in tumor invasiveness. Neither KLK6 nor KLK10 was significantly associated with other prognostic markers, including depth of invasion, indicating their potential as independent biomarkers. Our results should be interpreted with caution due to limited sample size. There was a significant correlation between KLK6 and KLK10 expression both at the invasive front and within the main tumor, indicating a collaborative effect. We then compared KLK6 and KLK10 messenger RNA expression between metaplastic and cancerous tissues in an independent data set of esophageal carcinoma from The Cancer Genome Atlas. KLK6 and KLK10 may be useful markers and potential therapeutic targets in gastroesophageal junction tumors.

Identification of human tissue kallikrein 6 as a potential marker of laryngeal cancer based on the relevant secretory/releasing protein database

OBJECTIVE

This study was aimed to create a large-scale laryngeal cancer relevant secretory/releasing protein database and further discover candidate biomarkers.

METHODS

Primary tissue cultures were established using tumor tissues and matched normal mucosal tissues collected from four laryngeal cancer patients. Serum-free conditioned medium (CM) samples were collected. These samples were then sequentially processed by SDS-PAGE separation, trypsin digestion, and LC-MS/MS analysis. The candidates in the database were validated by ELISA using plasma samples from laryngeal cancer patients, benign patients, and healthy individuals.

RESULTS

Combining MS data from the tumor tissues and normal tissues, 982 proteins were identified in total; extracellular proteins and cell surface proteins accounted for 15.0% and 4.3%, respectively. According to stringent criteria, 49 proteins were selected as candidates worthy of further validation. Of these, human tissue kallikrein 6 (KLK6) was verified. The level of KLK6 was significantly increased in the plasma samples from the cancer cohort compared to the benign and healthy cohorts and moreover showed a slight decrease in the postoperative plasma samples in comparison to the preoperative plasma samples.

CONCLUSIONS

This laryngeal cancer-derived protein database provides a promising repository of candidate blood biomarkers for laryngeal cancer. The diagnostic potential of KLK6 deserves further investigation.

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.

Correlation of hK6 expression with tumor recurrence and prognosis in advanced gastric cancer

Background

Human kallikrein gene 6 (KLK6) is a member of the human kallikrein gene family (Kallikreins, KLKs). Human kallikrein-related peptidase 6 (hK6) is a trypsin-like serine protease encoded by the KLK6, has been reported to be highly expressed in several cancers including gastric cancer. In this study, we investigated the the correlation of hK6 expression with clinicopathological characteristics, tumor recurrence and prognosis in advanced gastric carcinoma after curative resection.

Methods

We retrospectively analyzed the clinical data of 129 cases advanced gastric cancer after curative gastrectomy. The expression of hK6 in advanced gastric cancer tissues compared to adjacent noncancerous tissues were examined, and the relationship between hK6 expression and clinicopathological characteristics was evaluated. In additional, these patients were followed up to investigate the relationship between hK6 expression and the survival time.

Results

The positive rate of hK6 expression was significantly higher in advanced gastric cancer tissue, than that in adjacent noncancerous and gastric ulcer tissues (36.5%, 33.3%, respectively, P < 0.001). There was a close relationship between hK6 expression and TNM stage (P = 0.005), vascular invasion (P = 0.037) and perineural invasion (P = 0.035). Furthermore, patients with hK6 positive showed significantly higher recurrence and poorer prognosis than those with hK6 negative. Multivariate analysis showed that hK6 expression was a significant independent factor for tumor recurrence and overall survival.

Conclusion

hK6 is overexpressed in advanced gastric cancer tissues. Its clinical utility may be used as an unfavorable indicator in predicting tumor recurrence and prognosis for advanced gastric cancer after operation. This study also suggests that hK6 might be a potential therapeutic target for gastric cancer.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/8558403578787206

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.

Kallikrein-related peptidase 6 (KLK6)gene expression in intracranial tumors

Kallikrein-related peptidases (KLKs) are emerging novel new biomarkers for prognosis, diagnosis and therapeutic intervention of cancer. Kallikrein-related peptidase 6 (KLK6) has the highest expression in normal brain among other tissues. Although its expression has been extensively studied in many types of cancer and in neurodegenerative diseases, very little is known for its expression in intracranial tumors. In the present study, 73 intracranial tumor samples were examined for KLK6 messenger ribunucleic acid (mRNA) gene expression using quantitative real-time polymerase chain reaction. Statistical analysis revealed the significant association of KLK6 expression with clinical and pathological parameters. Follow-up information was available for a median time of 20 months (range 1-59 months). KLK6 is expressed more frequently in tumors of high malignancy like the glioblastomas (70.6 %) and less in tumors of low malignancy like the meningiomas (12.5 %). KLK6 positive expression is associated with tumor grade (p < 0.001), malignancy status (p < 0.001), and tumor histologic type (p = 0.001). Cox proportional hazard regression model using univariate analysis revealed for the first time that positive KLK6 expression is a significant factor for disease-free survival (DFS; p = 0.041) of patients suffering from intracranial tumors. Kaplan-Meier survival curves demonstrated that negative KLK6 expression is significantly associated with longer DFS (p = 0.032). KLK6 gene expression may have clinical utility as a marker of unfavorable prognosis for intracranial tumors, and consequently, it could be used as target for therapeutic intervention.

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.

The physiology and pathobiology of human kallikrein-related peptidase 6 (KLK6)

The human kallikrein-related peptidase 6 (KLK6) gene belongs to the 15-member kallikrein (KLK) gene family mapping to chromosome 19q13.3-13.4. Encoding for an enzyme with trypsin-like properties, KLK6 can degrade components of the extracellular matrix. The successful utilisation of another KLK member (KLK3/PSA) for prostate cancer diagnosis has led many to evaluate KLK6 as a potential biomarker for other cancer and diseased states. The observed dysregulated expression in cancers, neurodegenerative diseases and skin conditions has led to the discovery that KLK6 participates in other cellular pathways including inflammation, receptor activation and regulation of apoptosis. Moreover, the improvements in high-throughput genomics have not only enabled the identification of sequence polymorphisms, but of transcript variants, whose functional significances have yet to be realised. This comprehensive review will summarise the current findings of KLK6 pathophysiology and discuss its potential as a viable biomarker.

Five primary human pancreatic adenocarcinoma cell lines established by the outgrowth method

BACKGROUND

Pancreatic ductal adenocarcinoma is an aggressive tumor; treatment remains a challenge because of the lack of effective therapeutic strategies. Basic research in this field is dependent on the availability of model systems. New pancreatic cancer cell lines are therefore important for the study of its biology. In the present study, we report the establishment and characterization of five new pancreatic cancer cell lines (PaCaDD-43, -60, -119, -135, -137).

MATERIAL AND METHODS

All cell lines were derived from pancreatic ductal adenocarcinomas by the Dresden outgrowth protocol. The five cell lines originated from primary pancreatic tumors, lymph node metastases, or malignant pleural effusions. We characterized the cell lines by examining their morphology and their cytostructural and functional profiles.

RESULTS

All cell lines grew as adherent monolayers and were cultured in optimized Dresden-medium. The doubling time ranged from 22 to 47 h. v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations were detected in four of the five cell lines. KRAS mutations were identical between each primary tumor and the cell line derived from it. Immunohistochemical staining showed cytoplasmic expression of CK8/18, mostly membrane and partially cytoplasmic expression of E-cadherin and strong expression of ezrin in all cell lines. Three cell lines showed nuclear p53 accumulation and heterogeneous expression of vimentin. SMAD4 was heterogeneously expressed in four of the cell lines.

CONCLUSIONS

We were able to establish five new primary pancreatic carcinoma cell lines. As applicable tools for basic research, these cell lines might contribute to a better understanding and treatment of this aggressive tumor.

Tissue biomarkers for prognosis in pancreatic ductal adenocarcinoma: a systematic review and meta-analysis

PURPOSE

The management of pancreatic ductal adenocarcinoma (PDAC) continues to present a great challenge particularly with regard to prediction of outcome following pancreaticoduodenectomy. Molecular markers have been extensively investigated by numerous groups with the aim of enhancing prognostication; however, despite hundreds of studies that have sought to assess the potential prognostic value of molecular markers in predicting the clinical course following resection of PDAC, at this time, no molecular marker assay forms part of recommended clinical practice.

EXPERIMENTAL DESIGN

We conducted a systematic review and meta-analysis of the published literature for immunohistochemistry-based biomarkers of PDAC outcome. A dual search strategy was applied to the PubMed database on January 6, 2010, to identify cohort studies that reported associations between immunohistochemical biomarker expression and survival outcomes in PDAC, and conformed to the REMARK (REporting recommendations for tumor MARKer prognostic studies) criteria.

RESULTS

A total of 103 distinct proteins met all inclusion criteria. Promising markers that emerged for the prediction of overall survival included BAX (HR = 0.31, 95% CI: 0.71-0.56), Bcl-2 (HR = 0.41, 95% CI: 0.27-0.63), survivin (HR = 0.46, 95% CI: 0.29-0.73), Ki-67: (HR = 2.42, 95% CI: 1.87-3.14), COX-2 (HR = 1.39, 95% CI: 1.13-1.71), E-cadherin (HR = 1.80, 95% CI: 1.33-2.42), and S100 calcium-binding proteins, in particular S100A2 (HR = 3.23, 95% CI: 1.58-6.62).

CONCLUSIONS

We noted that that there was incomplete adherence to the REMARK guidelines with inadequate methodology reporting as well as failure to perform multivariate analysis. Addressing the persistent incomplete adoption of these criteria may eventually result in the incorporation of molecular marker assessment within PDAC management algorithms.

Functional role of kallikrein 6 in regulating immune cell survival

BACKGROUND

Kallikrein 6 (KLK6) is a newly identified member of the kallikrein family of secreted serine proteases that prior studies indicate is elevated at sites of central nervous system (CNS) inflammation and which shows regulated expression with T cell activation. Notably, KLK6 is also elevated in the serum of multiple sclerosis (MS) patients however its potential roles in immune function are unknown. Herein we specifically examine whether KLK6 alters immune cell survival and the possible mechanism by which this may occur.

METHODOLOGY/PRINCIPAL FINDINGS

Using murine whole splenocyte preparations and the human Jurkat T cell line we demonstrate that KLK6 robustly supports cell survival across a range of cell death paradigms. Recombinant KLK6 was shown to significantly reduce cell death under resting conditions and in response to camptothecin, dexamethasone, staurosporine and Fas-ligand. Moreover, KLK6-over expression in Jurkat T cells was shown to generate parallel pro-survival effects. In mixed splenocyte populations the vigorous immune cell survival promoting effects of KLK6 were shown to include both T and B lymphocytes, to occur with as little as 5 minutes of treatment, and to involve up regulation of the pro-survival protein B-cell lymphoma-extra large (Bcl-XL), and inhibition of the pro-apoptotic protein Bcl-2-interacting mediator of cell death (Bim). The ability of KLK6 to promote survival of splenic T cells was also shown to be absent in cell preparations derived from PAR1 deficient mice.

CONCLUSION/SIGNIFICANCE

KLK6 promotes lymphocyte survival by a mechanism that depends in part on activation of PAR1. These findings point to a novel molecular mechanism regulating lymphocyte survival that is likely to have relevance to a range of immunological responses that depend on apoptosis for immune clearance and maintenance of homeostasis.

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.

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.

Serum tumor markers in pancreatic cancer-recent discoveries

The low prevalence of pancreatic cancer remains an obstacle to the development of effective screening tools in an asymptomatic population. However, development of effective serologic markers still offers the potential for improvement of diagnostic capabilities, especially for subpopulations of patients with high risk for pancreatic cancer. The accurate identification of patients with pancreatic cancer and the exclusion of disease in those with benign disorders remain important goals. While clinical experience largely dismissed many candidate markers as useful markers of pancreatic cancer, CA19-9 continues to show promise. The present review highlights the development and the properties of different tumor markers in pancreatic cancer and their impact on the diagnostic and treatment of this aggressive disease.

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.

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.

KLK6 and KLK13 predict tumor recurrence in epithelial ovarian carcinoma

Background:

The human kallikrein-related peptidase family consists of 15 genes. Twelve of these genes are overexpressed in ovarian cancer and may represent potential markers for diagnosis, prognosis, and/or response to treatment. The aim of this study was to determine the prognostic significance of kallikrein-related peptidase 6 (KLK6) and kallikrein-related peptidase 13 (KLK13) in epithelial ovarian cancer by quantifying gene expression levels with tumour pathology and patient survival data.

Methods:

Total RNA was isolated from 106 patients diagnosed with primary ovarian cancer, as well as 8 normal ovary controls. Samples were analysed by quantitative real-time PCR for KLK6 and KLK13 expression. Correlation between kallikrein gene expression and clinical characteristics was evaluated with the χ²-test. Survival analysis was performed using Kaplan–Meier and Cox proportional hazards regression models.

Results:

Expression levels of both KLK6 and KLK13 mRNA were significantly increased in invasive cancers relative to normal ovaries (P=0.002 and 0.039 respectively). High KLK6 and KLK13 expression was an indicator of poor prognosis, with patients having a shorter recurrence-free survival (P=0.002 and 0.027 respectively). High KLK6 expression was also significantly associated with lower overall survival (P=0.011). When subjected to multivariate analysis, patients with either high KLK6 or KLK13 were 3- and 2.2-fold, respectively, more likely to have a recurrence than patients with low kallikrein expression.

Conclusion:

These data show increased mRNA expression of KLK6 and KLK13 in ovarian cancer compared to normal ovarian tissues. High KLK6 or KLK13 expression in primary ovarian tumours can significantly predict prognosis in terms of recurrence-free survival and overall survival. In all, this study shows KLK6 and KLK13 as potential biomarkers and may be therapeutic targets for treatment of ovarian cancer.

Inhibition of MIF leads to cell cycle arrest and apoptosis in pancreatic cancer cells

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is the eighth most common cancer with the lowest overall 5-y relative survival rate. Gene expression profiling of PDAC revealed an overexpression of the macrophage migration inhibitory factor (MIF), a lymphokine involved in cell-mediated immunity and inflammation, as well as in the regulation of cellular signal transduction.

MATERIALS AND METHODS

Endogenous MIF expression was silenced by treatment of pancreatic cancer cell lines using two independent MIF siRNAs. The expression of MIF RNA and protein after siRNA treatment was investigated using quantitative RT-PCR and Western blot. Induction of apoptosis was analyzed using fluorescence activated cell sorting (FACS).

RESULTS

Transfection of MiaPaCa-2 cells with MIF siRNA resulted in a reduction of MIF RNA and protein levels by more than 85%. After treatment, we observed an inhibition of cellular proliferation accompanied by induction of apoptosis. Analysis of the phosphorylation state of Akt showed a markedly increase of the phosphorylation at the Thr308 residue.

CONCLUSIONS

Using post-transcriptional silencing with small interfering RNAs, we could show that MIF acts as an autocrine growth factor involved in cell cycle progression. Since MIF is a secreted protein, a therapy directed against MIF or its receptor might lead to a significant growth reduction of PDAC.