Protein C inhibitor regulates both cathepsin L activity and cell-mediated tumor cell migration

Transcriptomic analysis to identify genes associated with selective hippocampal vulnerability in Alzheimer's disease

Selective vulnerability of different brain regions is seen in many neurodegenerative disorders. The hippocampus and cortex are selectively vulnerable in Alzheimer's disease (AD), however the degree of involvement of the different brain regions differs among patients. We classified corticolimbic patterns of neurofibrillary tangles in postmortem tissue to capture extreme and representative phenotypes. We combined bulk RNA sequencing with digital pathology to examine hippocampal vulnerability in AD. We identified hippocampal gene expression changes associated with hippocampal vulnerability and used machine learning to identify genes that were associated with AD neuropathology, including SERPINA5, RYBP, SLC38A2, FEM1B, and PYDC1. Further histologic and biochemical analyses suggested SERPINA5 expression is associated with tau expression in the brain. Our study highlights the importance of embracing heterogeneity of the human brain in disease to identify disease-relevant gene expression.

Associations of Polymorphism of rs9944155, rs1051052, and rs1243166 Locus Allele in Alpha-1-antitrypsin with Chronic Obstructive Pulmonary Disease in Uygur Population of Kashgar Region

Background:

Previous studies conducted in various geographical and ethnical populations have shown that Alpha-1-antitrypsin (Alpha-1-AT) expression affects the occurrence and progression of chronic obstructive pulmonary disease (COPD). We aimed to explore the associations of rs9944155AG, rs1051052AG, and rs1243166AG polymorphisms in the Alpha-1-AT gene with the risk of COPD in Uygur population in the Kashgar region.

Methods:

From March 2013 to December 2015, a total of 225 Uygur COPD patients and 198 healthy people were recruited as cases and controls, respectively, in Kashgar region. DNA was extracted according to the protocol of the DNA genome kit, and Sequenom MassARRAY single-nucleotide polymorphism technology was used for genotype determination. Serum concentration of Alpha-1-AT was detected by enzyme-linked immunosorbent assay. A logistic regression model was used to estimate the associations of polymorphisms with COPD.

Results:

The rs1243166-G allele was associated with a higher risk of COPD (odds ratio [OR] = 2.039, 95% confidence interval [CI]: 1.116–3.725, P = 0.019). In cases, Alpha-1-AT levels were the highest among participants carrying rs1243166 AG genotype, followed by AA and GG genotype (χ² = 11.89, P = 0.003). Similarly, the rs1051052-G allele was associated with a higher risk of COPD (OR = 19.433, 95% CI: 8.783–43.00, P < 0.001). The highest Alpha-1-AT levels were observed in cases carrying rs1051052 AA genotype, followed by cases with AG and GG genotypes (χ² = 122.45, P < 0.001). However, individuals with rs9944155-G allele exhibited a lower risk of COPD than those carrying the rs9944155-A allele (OR = 0.121, 95% CI: 0.070–0.209, P < 0.001). In both cases and controls, no significant difference in Alpha-1-AT levels was observed among various rs9944115 genotypes.

Conclusions:

rs1243166, rs9944155, and rs1051052 sites of Alpha-1-AT may be associated with the COPD morbidity in Uygur population. While rs1243166-G allele and rs1051052-G allele are associated with an increased risk of developing COPD, rs9944155-G allele is a protect locus in Uygur population. Alpha-1-AT levels in Uygur COPD patients were lower than those in healthy people and differed among patients with different rs1051052 AG and rs1243166 AG genotypes.

Cathepsin B Expression and the Correlation with Clinical Aspects of Oral Squamous Cell Carcinoma

Background

Cathepsin B (CTSB), a member of the cathepsin family, is a cysteine protease that is widely distributed in the lysosomes of cells in various tissues. It is overexpressed in several human cancers and may be related to tumorigenesis. The main purpose of this study was to analyze CTSB expression in oral squamous cell carcinoma (OSCC) and its correlation with patient prognosis.

Methodology/Principal Findings

Tissue microarrays were used to detect CTSB expression in 280 patients and to examine the association between CTSB expression and clinicopathological parameters. In addition, the metastatic effects of the CTSB knockdown on two oral cancer cell lines were investigated by transwell migration assay. Cytoplasmic CTSB expression was detected in 34.6% (97/280) of patients. CTSB expression was correlated with positive lymph node metastasis (p = 0.007) and higher tumor grade (p = 0.008) but not with tumor size and distant metastasis. In addition, multivariate analysis using a Cox proportional hazards model revealed a higher hazard ratio, demonstrating that CTSB expression was an independent unfavorable prognostic factor in buccal mucosa carcinoma patients. Furthermore, the Kaplan–Meier curve revealed that buccal mucosa OSCC patients with positive CTSB expression had significantly shorter overall survival. Moreover, treatment with the CTSB siRNA exerted an inhibitory effect on migration in OC2 and CAL27 oral cancer cells.

Conclusions

We conclude that CTSB expression may be useful for determining OSCC prognosis, particularly for patients with lymph node metastasis, and may function as a biomarker of the survival of OSCC patients in Taiwan.

The role of serpins in tumor cell migration

Tumor cells are characterized by uncontrolled cell growth at a primary site that is caused by genetic alterations. Tumor cells that metastasize from their primary site to distant locations are commonly referred to as malignant. Cell migration is a critical step in this process. The ability of tumor cells to migrate and invade is partly controlled by proteolytic enzymes. These enzymes are secreted by either the tumor cells themselves or adjacent cells. They represent all classes of proteases, including serine and cysteine proteases. Serine proteases, in particular urokinase plasminogen activator (uPA), initiate a proteolytic cascade that culminates in degrading components of the extracellular matrix (ECM). Some serine proteases are controlled by a superfamily of proteins known as serpins. This minireview provides an overview of serpins that are vital in regulating tumor cell migration and progressing cancer.

A+-helix of protein C inhibitor (PCI) is a cell-penetrating peptide that mediates cell membrane permeation of PCI

Protein C inhibitor (PCI) is a serpin with broad protease reactivity. It binds glycosaminoglycans and certain phospholipids that can modulate its inhibitory activity. PCI can penetrate through cellular membranes via binding to phosphatidylethanolamine. The exact mechanism of PCI internalization and the intracellular role of the serpin are not well understood. Here we showed that testisin, a glycosylphosphatidylinositol-anchored serine protease, cleaved human PCI and mouse PCI (mPCI) at their reactive sites as well as at sites close to their N terminus. This cleavage was observed not only with testisin in solution but also with cell membrane-anchored testisin on U937 cells. The cleavage close to the N terminus released peptides rich in basic amino acids. Synthetic peptides corresponding to the released peptides of human PCI (His¹–Arg¹¹) and mPCI (Arg¹–Ala¹⁸) functioned as cell-penetrating peptides. Because intact mPCI but not testisin-cleaved mPCI was internalized by Jurkat T cells, a truncated mPCI mimicking testisin-cleaved mPCI was created. The truncated mPCI lacking 18 amino acids at the N terminus was not taken up by Jurkat T cells. Therefore our model suggests that testisin or other proteases could regulate the internalization of PCI by removing its N terminus. This may represent one of the mechanisms regulating the intracellular functions of PCI.

SERPINA5 inhibits tumor cell migration by modulating the fibronectin-integrin β1 signaling pathway in hepatocellular carcinoma

In our previous study, we identified 1241 loci with somatic copy number alterations in human hepatocellular carcinoma (HCC) using Affymetrix SNP 6.0 arrays, and a putative cancer gene SERPINA5 was uncovered in a novel chromosomal region with recurrent copy number loss at 14q31.1-32.13. The SERPINA5 was reported to be deregulated in renal, breast, prostate and ovarian cancers. However, the roles of SERPINA5 in cancer remain greatly elusive. In this study, we found that the DNA dosage and expression level of the SERPINA5 gene were significantly decreased in HCC by quantitative real-time PCR. Notably, the expression levels of SERPINA5 negatively correlated with malignant progression of HCC. The SERPINA5 gene was further observed to reduce in vitro and in vivo metastatic potential of HCC cells. Moreover, secreted SERPINA5 protein also could inhibit the metastatic ability of HCC cells. Finally, we discovered that one of the mechanisms explaining SERPINA5 inhibition of HCC metastasis is through direct interaction with fibronectin and disruption of the fibronectin-integrin signaling pathway. These findings highlight an important role of SERPINA5 in the regulation of migratory and metastatic potentials of HCC and suggest a potential application of SERPINA5 in cancer treatment.

Cathepsin L inhibition by the small molecule KGP94 suppresses tumor microenvironment enhanced metastasis associated cell functions of prostate and breast cancer cells

Metastasis remains the major cause of therapeutic failure, poor prognosis and high mortality in breast and prostate cancer patients. Aberrant microenvironments including hypoxia and acidic pH are common features of most solid tumors that have been long associated with enhanced metastasis and poor patient outcomes. Novel approaches to reduce metastatic incidences and improve overall survival of cancer patients clearly are needed. The crucial role of Cathepsin L (CTSL) in the dissemination of tumor cells has led to the development of novel cathepsin L inhibition strategies. The present study evaluated the ability of KGP94, a small molecule inhibitor of CTSL, to impair the metastatic phenotype of prostate (PC-3ML) and breast (MDA-MB-231) cancer cells both under normal and aberrant microenvironmental conditions. To assess the role of CTSL in hypoxia and acidosis triggered metastasis associated cell functions, secreted CTSL levels were determined under conditions pertinent to the tumor microenvironment. Acute exposures to hypoxic or acidic conditions significantly elevated secreted CTSL levels either through an increase in intracellular CTSL levels or through activation of lysosomal exocytosis or both, depending on the tumor type. Increases in CTSL secretion closely paralleled enhanced tumor cell migration and invasion suggesting that CTSL could be an essential factor in tumor microenvironment triggered metastasis. Importantly, KGP94 treatment led to marked attenuation of tumor cell invasion and migration under both normal and aberrant microenvironmental conditions suggesting that it may have significant utility as an anti-metastatic agent.

Interaction of protein C inhibitor with the type II transmembrane serine protease enteropeptidase

The serine protease inhibitor protein C inhibitor (PCI) is expressed in many human tissues and exhibits broad protease reactivity. PCI binds glycosaminoglycans and certain phospholipids, which modulate its inhibitory activity. Enteropeptidase (EP) is a type II transmembrane serine protease mainly found on the brush border membrane of epithelial cells in the duodenum, where it activates trypsinogen to initiate the digestion of food proteins. Some active EP is also present in duodenal fluid and has been made responsible for causing pancreatitis in case of duodeno-pancreatic reflux. Together with its substrate trypsinogen, EP is furthermore present in the epidermis and in some cancer cells. In this report, we show that PCI inhibited EP with an apparent 2nd order rate constant of 4.48 × 10(4) M(-1) s(-1). Low molecular weight (LMWH) and unfractionated heparin (UFH) slightly reduced the inhibitory effect of PCI. The SI (stoichiometry of inhibition) value for the inhibition of EP by PCI was 10.8 in the absence and 17.9 in the presence of UFH (10 U/ml). By inhibiting trypsin, chymotrypsin, and additionally EP, PCI might play a role in the protection of the pancreas from autodigestion. Furthermore the interaction of PCI with EP may influence the regulation of epithelial differentiation.

Anti-angiogenic peptides for cancer therapeutics

Peptides have emerged as important therapeutics that are being rigorously tested in angiogenesis-dependent diseases due to their low toxicity and high specificity. Since the discovery of endogenous proteins and protein fragments that inhibit microvessel formation (thrombospondin, endostatin) several peptides have shown promise in pre-clinical and clinical studies for cancer. Peptides have been derived from thrombospondin, collagens, chemokines, coagulation cascade proteins, growth factors, and other classes of proteins and target different receptors. Here we survey recent developments for anti-angiogenic peptides with length not exceeding 50 amino acid residues that have shown activity in pre-clinical models of cancer or have been tested in clinical trials; some of the peptides have been modified and optimized, e.g., through L-to-D and non-natural amino acid substitutions. We highlight technological advances in peptide discovery and optimization including computational and bioinformatics tools and novel experimental techniques.

Post-transcriptional regulation of human cathepsin L expression

The expression of cathepsin L, a lysosomal protease, is known to be elevated in cancer and other pathologies. Multiple splice variants of human cathepsin L with variable 5'UTRs exist, which encode for the same protein. Previously we have observed that variant hCATL A (bearing the longest 5'UTR) was translated in vitro with significantly lower efficiency than variant hCATL AIII (bearing the shortest 5'UTR). Contrary to these findings, results of the present study reveal that in cancer cells, hCATL A mRNA exhibits higher translatability in spite of having lower stability than AIII. This is the first report demonstrating a highly contrasting trend in translation efficiencies of hCATL variants in rabbit reticulocytes and live cells. Expression from chimeric mRNAs containing 5'UTRs of A or AIII upstream to luciferase reporter cDNA established the A UTR to be the sole determinant for this effect. Transient transfections of bicistronic plasmids and mRNAs confirmed the presence of a functional Internal Ribosome Entry Site in this UTR. Our data suggest that differential stability and translation initiation modes mediated by the 5'UTRs of human cathepsin L variants are involved in regulating its expression.

Methods to measure the kinetics of protease inhibition by serpins

The serpin molecule has evolved an unusual mechanism of inhibition, involving an exposed reactive center loop (RCL) and conformational change to covalently trap a target protease. Successful inhibition of the protease is dependent on the rate of serpin-protease association and the efficiency with which the RCL inserts into β-sheet A, translocating the covalently bound protease and thereby completing the inhibition process. This chapter describes the kinetic methods used for determining the rate of protease inhibition (k(a)) and the stoichiometry of inhibition. These kinetic variables provide a means to examine different serpin-protease pairings, assess the effects of mutations within a serpin on protease inhibition, and determine the physiologically cognate protease of a serpin.