Differential cathepsin responses to inhibitor-induced feedback: E-64 and cystatin C elevate active cathepsin S and suppress active cathepsin L in breast cancer cells

Causal relationship between renal function and risk of esophageal cancer: insights from Mendelian randomization

Background

Previous studies have indicated a potential correlation between renal function and risk of cancer. However, establishing a causal relationship is challenging. To address this, we employed Mendelian randomization (MR), a novel method that utilizes genotype data to simulate randomized trial groups, to investigate whether there is a causal correlation between renal function and the esophageal cancer (EC) risk.

Methods

MR analysis was conducted with the individual-level data on EC from the UK Biobank published dataset. Genetic instruments were derived from single nucleotide polymorphisms (SNPs) extracted from publicly available genome-wide association studies. Furthermore, leave-one-out sensitivity analysis was performed to assess the impact of individual SNPs.

Results

In our MR analysis, we examined 39,475,182 SNPs associated with various renal functional indexes from public databases. Based on the primary causal effects model using MR analyses with the inverse variance weighted method, the genetically predicted cystatin C [odds ratio (OR) =1.0005, 95% confidence interval (CI): 1.0000-1.0009; P=0.05] and creatinine (OR =1.0016, 95% CI: 1.0002-1.0031; P=0.02) demonstrated a significant association with higher risk of EC. However, we found no evidence of an association between urinary albumin and glomerular filtration rate with the risk of EC.

Conclusions

Our research provides strong evidence for the association of decreased renal function to a potential risk of EC. However, it is crucial to recognize the necessity for additional large-scale prospective studies to validate this discovery and establish a comprehensive understanding of the causal relationships between renal function and EC.

Keywords

Esophageal cancer (EC); renal function; Mendelian randomization (MR); causal association.

Compensational role between cathepsins

Cathepsins, a family of lysosomal peptidases, play a crucial role in maintaining cellular homeostasis by regulating protein turnover and degradation as well as many specific regulatory actions that are important for proper cell function and human health. Alterations in the activity and expression of cathepsins have been observed in many diseases such as cancer, inflammation, neurodegenerative disorders, bone remodelling-related conditions and others. These changes are not exclusively harmful, but rather appear to be a compensatory response on the lack of one cathepsin in order to maintain tissue integrity. The upregulation of specific cathepsins in response to the inhibition or dysfunction of other cathepsins suggests a fine-tuned system of proteolytic balance and understanding the compensatory role of cathepsins may improve therapeutic potential of cathepsin's inhibitors. Selectively targeting one cathepsin or modulating their activity could offer new treatment strategies for a number of diseases. This review emphasises the need for comprehensive research into cathepsin biology in the context of disease. The identification of the specific cathepsins involved in compensatory responses, the elucidation of the underlying molecular mechanisms and the development of targeted interventions could lead to innovative therapeutic approaches.

Microfluidic Platform for Microparticle Fabrication and Release of a Cathepsin Inhibitor

Cathepsins are a family of cysteine proteases responsible for a variety of homeostatic functions throughout the body, including extracellular matrix remodeling, and have been implicated in a variety of degenerative diseases. However, clinical trials using systemic administration of cathepsin inhibitors have been abandoned due to side effects, so local delivery of cathepsin inhibitors may be advantageous. In these experiments, a novel microfluidic device platform was developed that can synthesize uniform, hydrolytically degradable microparticles from a combination of poly(ethylene glycol) diacrylate (PEGDA) and dithiothreitol (DTT). Of the formulations examined, the 10-polymer weight percentage 10 mM DTT formulation degraded after 77 days in vitro. A modified assay using the DQ Gelatin Fluorogenic Substrate was used to demonstrate sustained release and bioactivity of a cathepsin inhibitor (E-64) released from hydrogel microparticles over 2 weeks in vitro (up to ∼13 μg/mL released with up to ∼40% original level of inhibition remaining at day 14). Altogether, the technologies developed in this study will allow a small-molecule, broad cathepsin inhibitor E-64 to be released in a sustained manner for localized inhibition of cathepsins for a wide variety of diseases.

Challenges and Opportunities Modeling the Dynamic Tumor Matrisome

We need novel strategies to target the complexity of cancer and, particularly, of metastatic disease. As an example of this complexity, certain tissues are particularly hospitable environments for metastases, whereas others do not contain fertile microenvironments to support cancer cell growth. Continuing evidence that the extracellular matrix (ECM) of tissues is one of a host of factors necessary to support cancer cell growth at both primary and secondary tissue sites is emerging. Research on cancer metastasis has largely been focused on the molecular adaptations of tumor cells in various cytokine and growth factor environments on 2-dimensional tissue culture polystyrene plates. Intravital imaging, conversely, has transformed our ability to watch, in real time, tumor cell invasion, intravasation, extravasation, and growth. Because the interstitial ECM that supports all cells in the tumor microenvironment changes over time scales outside the possible window of typical intravital imaging, bioengineers are continuously developing both simple and sophisticated in vitro controlled environments to study tumor (and other) cell interactions with this matrix. In this perspective, we focus on the cellular unit responsible for upholding the pathologic homeostasis of tumor-bearing organs, cancer-associated fibroblasts (CAFs), and their self-generated ECM. The latter, together with tumoral and other cell secreted factors, constitute the "tumor matrisome". We share the challenges and opportunities for modeling this dynamic CAF/ECM unit, the tools and techniques available, and how the tumor matrisome is remodeled (e.g., via ECM proteases). We posit that increasing information on tumor matrisome dynamics may lead the field to alternative strategies for personalized medicine outside genomics.

Enzymes in the time of COVID-19: An overview about the effects in the human body, enzyme market, and perspectives for new drugs

The rising pandemic caused by a coronavirus, resulted in a scientific quest to discover some effective treatments against its etiologic agent, the severe acute respiratory syndrome‐coronavirus 2 (SARS‐CoV‐2). This research represented a significant scientific landmark and resulted in many medical advances. However, efforts to understand the viral mechanism of action and how the human body machinery is subverted during the infection are still ongoing. Herein, we contributed to this field with this compilation of the roles of both viral and human enzymes in the context of SARS‐CoV‐2 infection. In this sense, this overview reports that proteases are vital for the infection to take place: from SARS‐CoV‐2 perspective, the main protease (M^pro) and papain‐like protease (PL^pro) are highlighted; from the human body, angiotensin‐converting enzyme‐2, transmembrane serine protease‐2, and cathepsins (CatB/L) are pointed out. In addition, the influence of the virus on other enzymes is reported as the JAK/STAT pathway and the levels of lipase, enzymes from the cholesterol metabolism pathway, amylase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and glyceraldehyde 3‐phosphate dehydrogenase are also be disturbed in SARS‐CoV‐2 infection. Finally, this paper discusses the importance of detailed enzymatic studies for future treatments against SARS‐CoV‐2, and how some issues related to the syndrome treatment can create opportunities in the biotechnological market of enzymes and the development of new drugs.

Harnessing Extracellular Matrix Biology for Tumor Drug Delivery

The extracellular matrix (ECM) plays an active role in cell life through a tightly controlled reciprocal relationship maintained by several fibrous proteins, enzymes, receptors, and other components. It is also highly involved in cancer progression. Because of its role in cancer etiology, the ECM holds opportunities for cancer therapy on several fronts. There are targets in the tumor-associated ECM at the level of signaling molecules, enzyme expression, protein structure, receptor interactions, and others. In particular, the ECM is implicated in invasiveness of tumors through its signaling interactions with cells. By capitalizing on the biology of the tumor microenvironment and the opportunities it presents for intervention, the ECM has been investigated as a therapeutic target, to facilitate drug delivery, and as a prognostic or diagnostic marker for tumor progression and therapeutic intervention. This review summarizes the tumor ECM biology as it relates to drug delivery with emphasis on design parameters targeting the ECM.

Cysteine cathepsins are altered by flow within an engineered in vitro microvascular niche

Throughout the process of vascular growth and remodeling, the extracellular matrix (ECM) concurrently undergoes significant changes due to proteolytic activity—regulated by both endothelial and surrounding stromal cells. The role of matrix metalloproteinases has been well-studied in the context of vascular remodeling, but other proteases, such as cysteine cathepsins, could also facilitate ECM remodeling. To investigate cathepsin-mediated proteolysis in vascular ECM remodeling, and to understand the role of shear flow in this process, in vitro microvessels were cultured in previously designed microfluidic chips and assessed by immunostaining, zymography, and western blotting. Primary human vessels (HUVECs and fibroblasts) were conditioned by continuous fluid flow and/or small molecule inhibitors to probe cathepsin expression and activity. Luminal flow (in contrast to static culture) decreases the activity of cathepsins in microvessel systems, despite a total protein increase, due to a concurrent increase in the endogenous inhibitor cystatin C. Observations also demonstrate that cathepsins mostly co-localize with fibroblasts, and that fibrin (the hydrogel substrate) may stabilize cathepsin activity in the system. Inhibitor studies suggest that control over cathepsin-mediated ECM remodeling could contribute to improved maintenance of in vitro microvascular networks; however, further investigation is required. Understanding the role of cathepsin activity in in vitro microvessels and other engineered tissues will be important for future regenerative medicine applications.

The potential of cystatin C as a predictive biomarker in breast cancer

INTRODUCTION

Breast cancer (BCa) is the leading cause of cancer-related deaths among women. Numerous efforts are being directed toward identifying novel tissue and/or circulating molecular markers that may help clinicians in detecting early-stage BCa patients and in providing an accurate estimation of the prognosis and prediction of response to clinical treatments. In this setting, emerging evidence has indicated Cystatin C (Cyst C), as the most potent endogenous inhibitor of cysteine cathepsins, as a possible useful marker in the clinical management of BCa patients.

AREAS COVERED

This review analyzes the results of emerging studies underpinning a potential clinical role of Cyst C, as additional marker in BCa.

EXPERT OPINION

Cyst C expression levels have been reported to be altered in tumor tissues and/or in biological fluids of BCa patients. Furthermore, clinical evidence has highlighted a significant correlation between altered Cyst C levels in tumor tissues and/or biological fluids and some clinco-biological parameters of BCa progression. These findings provide evidence for a potential clinical use of Cyst C as a novel marker to improve the clinical and therapeutic management of BCa patients and as a gauge for better clarifying the role of cysteine proteinases in the various steps of BCa progression.

Thrombin alters the synthesis and processing of CYR61/CCN1 in human corneal stromal fibroblasts and myofibroblasts through multiple distinct mechanisms

Purpose

Previous research in our laboratory indicated that prothrombin and other coagulation enzymes required to activate prothrombin to thrombin are synthesized by the cornea and that apoptotic human corneal stromal cells can provide a surface for prothrombin activation through the intrinsic and extrinsic coagulation pathways. The purpose of the work reported here is to study the role of thrombin activity in the regulation of matricellular protein Cyr61 (CCN1) produced by wounded phenotype human corneal stromal fibroblasts and myofibroblasts.

Methods

Stromal cells from human donor corneas were converted to defined wounded phenotype fibroblasts and myofibroblasts with fetal bovine serum, followed by basic fibroblast growth factor (bFGF) and transforming growth factor beta-1 (TGFβ-1), respectively, and stimulated with varying concentrations (0-10.0 units (U)/ml) of thrombin from 1-7 h. Cyr61 transcript levels were determined using reverse transcriptase-PCR (RT-PCR) and quantitative PCR (qPCR) while protein forms were analyzed using western blot data. Protease activities were characterized via protease class-specific inhibitors and western blot analysis. Thrombin activity was quantified using the fluorogenic peptide Phe-Pro-Arg-AFC. Protease-activated receptor (PAR) agonist peptides-1 and -4 were used to determine whether cells increased Cyr61 through PAR signaling pathways. The PAR-1 antagonist SCH 79797 was used to block the thrombin cleavage of the receptor. PCR data were analyzed using MxPro software and western blot data were analyzed using Image Lab™ and Image J software. Student t test and one- and two-way ANOVA (with or without ranking, depending on sample distribution), together with Dunnett's test or Tukey comparison tests for post-hoc analysis, were used to determine statistical significance.

Results: Full-length Cyr61 is expressed by human corneal stromal fibroblasts and myofibroblasts and is significantly upregulated by active thrombin stimulation at the message (p<0.03) and protein (p<0.03) levels for fibroblasts and myofibroblasts. Inhibition by the allosteric thrombin-specific inhibitor hirudin prevented the thrombin-associated increase in the Cyr61 protein expression, indicating that the proteolytic activity of thrombin is required for the increase of the Cyr61 protein level. PAR-1 agonist stimulation of fibroblasts and myofibroblasts significantly increased cell-associated Cyr61 protein levels (p<0.04), and PAR-1 antagonist SCH 79797 significantly inhibited the thrombin stimulated increase of Cyr61 in fibroblasts but not in myofibroblasts. In the fibroblast and myofibroblast conditioned media, Cyr61 was detected as the full-length 40 kDa protein in the absence of thrombin, and mainly at 24 kDa in the presence of thrombin at ≥0.5 U/ml, using an antibody directed toward the internal linker region between the von Willebrand factor type C and thrombospondin type-1 domains. Although known to undergo alternative splicing, Cyr61 that is synthesized by corneal fibroblasts and myofibroblasts is not alternatively spliced in response to thrombin stimulation nor is Cyr61 directly cleaved by thrombin to generate its 24 kDa form; instead, Cyr61 is proteolytically processed into 24 kDa N- and 16 kDa C-terminal fragments by a thrombin activated leupeptin-sensitive protease present in conditioned media with activity distinct from the proteolytic activity of thrombin.

Conclusions

In cultured human corneal stromal fibroblasts and myofibroblasts, thrombin regulates Cyr61 through two mechanisms: 1) thrombin increases the Cyr61 expression at the message and protein levels, and 2) thrombin increases the activation of a leupeptin-sensitive protease that stimulates the cleavage of Cyr61 into N- and C-terminal domain populations in or near the thrombospondin type-1 domain. Generation of Cyr61 peptides during corneal injury stimulation may reveal additional functions of the protein, which modulate corneal wound healing activities or decrease activities of the full-length Cyr61 form.

Cathepsin S: investigating an old player in lung disease pathogenesis, comorbidities, and potential therapeutics

Dysregulated expression and activity of cathepsin S (CTSS), a lysosomal protease and a member of the cysteine cathepsin protease family, is linked to the pathogenesis of multiple diseases, including a number of conditions affecting the lungs. Extracellular CTSS has potent elastase activity and by processing cytokines and host defense proteins, it also plays a role in the regulation of inflammation. CTSS has also been linked to G-coupled protein receptor activation and possesses an important intracellular role in major histocompatibility complex class II antigen presentation. Modulated CTSS activity is also associated with pulmonary disease comorbidities, such as cancer, cardiovascular disease, and diabetes. CTSS is expressed in a wide variety of immune cells and is biologically active at neutral pH. Herein, we review the significance of CTSS signaling in pulmonary diseases and associated comorbidities. We also discuss CTSS as a plausible therapeutic target and describe recent and current clinical trials examining CTSS inhibition as a means for treatment.

Cysteine Cathepsins: Potential Applications in Diagnostics and Therapy of Malignant Tumors

Cysteine cathepsins are proteolytic enzymes involved in protein degradation in lysosomes and endosomes. Cysteine cathepsins have been also found in the tumor microenvironment during carcinogenesis, where they are implicated in proliferation, invasion and metastasis of tumor cells through the degradation of extracellular matrix, suppression of cell-cell interactions, and promotion of angiogenesis. In this regard, cathepsins can have a diagnostic value and represent promising targets for antitumor drugs aimed at inhibition of these proteases. Moreover, cysteine cathepsins can be used as activators of novel targeted therapeutic agents. This review summarizes recent discovered roles of cysteine cathepsins in carcinogenesis and discusses new trends in cancer therapy and diagnostics using cysteine cathepsins as markers, targets, or activators.

Long-Term Cryopreservation and Revival of Tissue-Engineered Skeletal Muscle

IMPACT STATEMENT

The ability to freeze, revive, and prolong the lifetime of tissue-engineered skeletal muscle without incurring any loss of function represents a significant advancement in the field of tissue engineering. Cryopreservation enables the efficient fabrication, storage, and shipment of these tissues. This in turn facilitates multidisciplinary collaboration between research groups, enabling advances in skeletal muscle regenerative medicine, organ-on-a-chip models of disease, drug testing, and soft robotics. Furthermore, the observation that freezing undifferentiated skeletal muscle enhances functional performance may motivate future studies developing stronger and more clinically relevant engineered muscle.

Dynamic Model of Protease State and Inhibitor Trafficking to Predict Protease Activity in Breast Cancer Cells

Introduction

Cysteine cathepsins are implicated in breast cancer progression, produced by both transformed epithelial cells and infiltrated stromal cells in tumors, but to date, no cathepsin inhibitor has been approved for clinical use due to unexpected side effects. This study explores cellular feedback to cathepsin inhibitors that might yield non-intuitive responses, and uses computational models to determine underlying cathepsin-inhibitor dynamics.

Methods

MDA-MB-231 cells treated with E64 were tested by multiplex cathepsin zymography and immunoblotting to quantify total, active, and inactive cathepsins S and L. This data was used to parameterize mathematical models of intracellular free and inhibited cathepsins, and then applied to a dynamic model predicting cathepsin responses to other classes of cathepsin inhibitors that have also failed clinical trials.

Results

E64 treated cells exhibited increased amounts of active cathepsin S and reduced amount of active cathepsin L, although E64 binds tightly to both. This inhibitor response was not unique to cancer cells or any one cell type, suggesting an underlying fundamental mechanism of E64 preserving activity of cathepsin S, but not cathepsin L. Computational models were able to predict and differentiate between inhibitor-bound, active, and inactive cathepsin species and demonstrate how different classes of cathepsin inhibitors can have drastically divergent effects on active cathepsins located in different intracellular compartments.

Conclusions

Together, this work has important implications for the development of mathematical model systems for protease inhibition in tissue destructive diseases, and consideration of preservation mechanisms by inhibitors that could alter perceived benefits of these treatment modalities.

Cystatins in cancer progression: More than just cathepsin inhibitors

Cystatins are endogenous and reversible inhibitors of cysteine peptidases that are important players in cancer progression. Besides their primary role as regulators of cysteine peptidase activity, cystatins are involved in cancer development and progression through proteolysis-independent mechanisms. Mechanistic studies of cystatin function revealed that they affect all stages of cancer progression including tumor growth, apoptosis, invasion, metastasis and angiogenesis. Recently, the involvement of cystatins in the antitumor immune responses was reported. In this review, we discuss molecular mechanisms and clinical aspects of cystatins in cancer. Altered expression of cystatins in cancer resulting in harmful excessive cysteine peptidase activity has been a subject of several studies in order to find correlations with clinical outcome and therapy response. However, involvement in anti-tumor immune response and signaling cascades leading to cancer progression designates cystatins as possible targets for development of new anti-tumor drugs.

Sequential, but not Concurrent, Incubation of Cathepsin K and L with Type I Collagen Results in Extended Proteolysis

Degradation of extracellular matrix (ECM) during tendinopathy is, in part, mediated by the collagenolytic cathepsin K (catK) and cathepsin L (catL), with a temporal component to their activity. The objective of this study was to determine how catK and catL act in concert or in conflict to degrade collagen and tendon ECM during tissue degeneration. To do so, type I collagen gels or ECM extracted from apolipoprotein E deficient mouse Achilles tendons were incubated with catK and catL either concurrently or sequentially, incubating catK first, then catL after a delayed time period. Sequential incubation of catK then catL caused greater degradation of substrates over concurrent incubation, and of either cathepsin alone. Zymography showed there were reduced amounts of active enzymes when co-incubated, indicating that cannibalism, or protease-on-protease degradation between catK and catL was occurring, but incubation with ECM could distract from these interactions. CatK alone was sufficient to quickly degrade tendon ECM, but catL was not, requiring the presence of catK for degradation. Together, these data identify cooperative and conflicting actions of cathepsin mediated collagen matrix degradation by considering interactive effects of multiple proteases during tissue degeneration.

Cathepsins: Potent regulators in carcinogenesis

Cathepsins (CTS) are mainly lysosomal acid hydrolases extensively involved in the prognosis of different diseases, and having a distinct role in tumor progression by regulating cell proliferation, autophagy, angiogenesis, invasion, and metastasis. As all these processes conjunctively lead to cancer progression, their site-specific regulation might be beneficial for cancer treatment. CTS regulate activation of the proteolytic cascade and protein turnover, while extracellular CTS is involved in promoting extracellular matrix degradation and angiogenesis, thereby stimulating invasion and metastasis. Despite cancer regulation, the involvement of CTS in cellular adaptation toward chemotherapy and radiotherapy augments their therapeutic potential. However, lysosomal permeabilization mediated cytosolic translocation of CTS induces programmed cell death. This complex behavior of CTS generates the need to discuss the different aspects of CTS associated with cancer regulation. In this review, we mainly focused on the significance of each cathepsin in cancer signaling and their targeting which would provide noteworthy information in the context of cancer biology and therapeutics.

Full-thickness rotator cuff tear in rat results in distinct temporal expression of multiple proteases in tendon, muscle, and cartilage

The etiology of joint tissue degeneration following rotator cuff tear remains unclear. Thus, the purpose of this study was to understand the timeline of protease activity in the soft tissues of the shoulder (tendon, muscle, and cartilage) that may lead to down-stream degeneration following rotator cuff tear. A well-established rat model involving suprascapular nerve denervation and supraspinatus/infraspinatus tendon transection was employed. Histological staining and/or micro-computed tomography (µCT) were used to observe structural damage in the supraspinatus tendon and muscle, humeral head cartilage, and subchondral bone. Multiplex gelatin zymography was utilized to assess protease activity in the supraspinatus tendon and muscle, and humeral head cartilage. Zymography analysis demonstrated that cathepsins were upregulated in the first week in all tissues, while MMP-2 maintained prolonged activity in supraspinatus tendon between 1 and 3 weeks and increased only at 3 weeks in supraspinatus muscle. In supraspinatus tendon, increased cathepsin L and MMP-2 activity in the first week was concurrent with matrix disorganization and infiltration of inflammatory cells. In contrast, significant upregulation of cathepsin L and K activity in supraspinatus muscle and humeral head cartilage did not correspond to any visible tissue damage at 1 week. However, focal defects developed in half of all animals' humeral head cartilage by 12 weeks (volume: 0.12 ± 0.09 mm³ ). This work provides a more comprehensive understanding of biochemical changes to joint tissue over time following rotator cuff tear. Overall, this provides insight into potential therapeutic targets and will better inform ideal intervention times and treatments for each tissue. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:490-502, 2019.

Investigating the Life Expectancy and Proteolytic Degradation of Engineered Skeletal Muscle Biological Machines

A combination of techniques from 3D printing, tissue engineering and biomaterials has yielded a new class of engineered biological robots that could be reliably controlled via applied signals. These machines are powered by a muscle strip composed of differentiated skeletal myofibers in a matrix of natural proteins, including fibrin, that provide physical support and cues to the cells as an engineered basement membrane. However, maintaining consistent results becomes challenging when sustaining a living system in vitro. Skeletal muscle must be preserved in a differentiated state and the system is subject to degradation by proteolytic enzymes that can break down its mechanical integrity. Here we examine the life expectancy, breakdown, and device failure of engineered skeletal muscle bio-bots as a result of degradation by three classes of proteases: plasmin, cathepsin L, and matrix metalloproteinases (MMP-2 and MMP-9). We also demonstrate the use of gelatin zymography to determine the effects of differentiation and inhibitor concentration on protease expression. With this knowledge, we are poised to design the next generation of complex biological machines with controllable function, specific life expectancy and greater consistency. These results could also prove useful for the study of disease-specific models, treatments of myopathies, and other tissue engineering applications.