Tissue Levels of Stefin A and Stefin B in Hepatocellular Carcinoma

Molecular and functional characterization of a type-1 cystatin in amphioxus (Branchiostoma japonicum)

Cystatins comprise a vast superfamily of evolutionary conserved proteins, predominantly recognized for their roles as endogenous inhibitors by regulating the activity of cysteine proteases. Emerging lines of research evidence also provides insight into their alternative roles in a spectrum of biological and pathological processes, including neurodegenerative disorders, tumor progression, inflammatory diseases, and immune response. Nowadays, various type-1 cystatins (stefins) have been demonstrated among a variety of discovered vertebrate groups, while little is known about the related homologue in cephalochordate amphioxus, which are repositioned at the base of the chordate phylum. In the present study, a single type-1 cystatin homologue in Branchiostoma japonicum was first successfully cloned and designated as Bjcystatin-1. The deduced Bjcystatin-1 protein is structurally characterized by the presence of typical wedge-shaped cystatin features, including the 'QxVxG' and 'Px' motif, as well as the conserved N-terminal glycine residue. Phylogenomic analyses utilizing different cystatin counterparts affirmed the close evolutionary relationship of Bjcystatin-1 and type-1 cystatin homologue. Bjcystatin-1 was predominantly expressed in the gills and hind-gut in a tissue-specific pattern, and its expression was remarkably up-regulated in response to challenge with bacteria or their signature molecules LPS and LTA, suggesting the involvement in immune response. Additionally, the recombinant Bjcystatin-1 (rBjcystatin-1) protein showed significant inhibitory activity towards papain and binding ability to LPS and LTA, indicating its hypothesized role as a pattern recognition receptor in immune response. Subcellular localization results also showed that Bjcystatin-1 was located in the cytoplasm and nucleus, and its overexpression could attenuate the activation of LPS-induced nuclear transcription factors NF-κB. Taken together, our study suggests that amphioxus Bjcystatin-1 acts as a dual role in protease inhibitor and an immunocompetent factor, providing new insights into the immune defense effect of type-1 cystatin in amphioxus.

CSTB accelerates the progression of hepatocellular carcinoma via the ERK/AKT/mTOR signaling pathway

Hepatocellular carcinoma (HCC) is a significant contributor to global cancer-related deaths, leading to high mortality rates. However, the pathogenesis of HCC remains unclear. In this research, by the bioinformatics data analysis, we found that elevated CSTB expression correlated with advanced disease and predicted diminished overall survival (OS) in HCC patients. We subsequently verified the oncogenic role of CSTB as well as the potential underlying mechanisms in HCC through a series of in vitro experiments, such as CCK-8 assays, cloning assays, flow cytometry, Transwell assays, and western blotting. Our findings illustrated that the silencing of CSTB effectively suppressed cellular proliferation by inducing cell cycle arrest in the G2 phase and impaired HCC cell invasion and migration by stimulating epithelial-mesenchymal transition (EMT). Additionally, we analyzed the pathways enriched in HCC using RNA sequencing and found that the ERK/AKT/mTOR signaling pathway was related to increased CSTB expression in HCC. Finally, we confirmed the tumorigenic role of CSTB via in vivo experiments. Thus, our findings revealed that silencing CSTB inhibited the HCC progression via the ERK/AKT/mTOR signaling pathway, highlighting new perspectives for investigating the mechanisms of HCC.

The intersection between cysteine proteases, Ca2+ signalling and cancer cell apoptosis

Apoptosis is a highly complex and regulated cell death pathway that safeguards the physiological balance between life and death. Over the past decade, the role of Ca2+ signalling in apoptosis and the mechanisms involved have become clearer. The initiation and execution of apoptosis is coordinated by three distinct groups of cysteines proteases: the caspase, calpain and cathepsin families. Beyond its physiological importance, the ability to evade apoptosis is a prominent hallmark of cancer cells. In this review, we will explore the involvement of Ca2+ in the regulation of caspase, calpain and cathepsin activity, and how the actions of these cysteine proteases alter intracellular Ca2+ handling during apoptosis. We will also explore how apoptosis resistance can be achieved in cancer cells through deregulation of cysteine proteases and remodelling of the Ca2+ signalling toolkit.

Cystatin B increases autophagic flux by sustaining proteolytic activity of cathepsin B and fuels glycolysis in pancreatic cancer: CSTB orchestrates autophagy and glycolysis in PDAC

BACKGROUND

Both autophagy and glycolysis are essential for pancreatic ductal adenocarcinoma (PDAC) survival due to desmoplasia. We investigated whether targeting a hub gene which participates in both processes could be an efficient strategy for PDAC treatment.

METHODS

The expression pattern of glycolysis signatures (GS) and autophagy signatures (AS) and their correlation with cystatin B (CSTB) in PDAC were analysed. It was discovered how CSTB affected the growth, glycolysis, and autophagy of PDAC cells. We assessed competitive binding to cathepsin B (CTSB) between CSTB and cystatin C (CSTC) via immunoprecipitation (IP) and immunofluorescence (IF). Chromatin immunoprecipitation quantitative polymerase chain reaction (ChIP-qPCR) and luciferase reporter gene assays were used to unveil the mechanism underlying CSTB upregulation. The expression pattern of CSTB was examined in clinical samples and KrasG12D/+, Trp53R172H/+, Pdx1-Cre (KPC) mice.

RESULTS

GS and AS were enriched and closely associated in PDAC tissues. CSTB increased autophagic flux and provided substrates for glycolysis. CSTB knockdown attenuated the proliferation of PDAC cells and patient-derived xenografts. The liquid chromatography-tandem mass spectrometry assay indicated CSTB interacted with CTSB and contributed to the proteolytic activity of CTSB in lysosomes. IF and IP assays demonstrated that CSTB competed with CSTC to bind to CTSB. Mutation of the key sites of CSTB abolished the interaction between CSTB and CTSB. CSTB was highly expressed in PDAC due to H3K27acetylation and SP1 expression. High expression of CSTB in PDAC was observed in tissue microarray and patients' serum samples.

CONCLUSIONS

Our work demonstrated the tumorigenic roles of autophagy and glycolysis in PDAC. CSTB is a key role in orchestrating these processes to ensure energy supply of PDAC cells.

Beyond basic research: the contribution of cathepsin B to cancer development, diagnosis and therapy

INTRODUCTION

In view of other candidate proteins from the cathepsin family of proteases holding great potential in being targeted during cancer therapy, the importance of Cathepsin B (CtsB) stands out as being truly exceptional. Based on its contribution to oncogenesis, its intimate connection with regulating apoptosis and modulating extracellular and intracellular functions through its secretion or compartmentalized subcellular localization, collectively highlight its complex molecular involvement with a myriad of normal and pathological regulatory processes. Despite its complex functional nature, CtsB is emerging as one of the few cathepsin proteases that has been extensively researched to yield tangible outcomes for cancer therapy.

AREAS COVERED

In this article, we review the scientific literature that has justified or shaped the importance of CtsB expression in cancer progression, from the perspective of highlighting a paradigm that is rapidly changing from basic research toward a broader clinical and translational context.

EXPERT OPINION

In doing so, we detail its maturation as a diagnostic marker through describing the development of CtsB-specific Activity-Based Probes, the rapid evolution of these toward a new generation of Prodrugs, and the evaluation of these in model systems for their therapeutic potential as anti-cancer agents in the clinic.

Transcriptional factor III A promotes colorectal cancer progression by upregulating cystatin A

BACKGROUND

Advanced colorectal cancer (CRC) generally has poor outcomes and high mortality rates. Clarifying the molecular mechanisms underlying CRC progression is necessary to develop new diagnostic and therapeutic strategies to improve CRC outcome and decrease mortality. Transcriptional factor III A (GTF3A), an RNA polymerase III transcriptional factor, is a critical driver of tumorgenesis and aggravates CRC cell growth.

AIM

To confirm whether GTF3A promotes CRC progression by regulating the expression of cystatin A (Csta) gene and investigate whether GTF3A can serve as a prognostic biomarker and therapeutic target for patients with CRC.

METHODS

Human tissue microarrays containing 90 pairs of CRC tissues and adjacent non-tumor tissues, and human tissue microarrays containing 20 pairs of CRC tissues, adjacent non-tumor tissues, and metastatic tissues were examined for GTF3A expression using immunohistochemistry. The survival rates of patients were analyzed. Short hairpin GTF3As and CSTAs were designed and packaged into the virus to block the expression of Gtf3a and Csta genes, respectively. In vivo tumor growth assays were performed to confirm whether GTF3A promotes CRC cell proliferation in vivo. Electrophoretic mobility shift assay and fluorescence in situ hybridization assay were used to detect the interaction of GTF3A with Csta, whereas luciferase activity assay was used to evaluate the expression of the Gtf3a and Csta genes. RNA-Sequencing (RNA-Seq) and data analyses were used to screen for target genes of GTF3A.

RESULTS

The expression of GTF3A was higher in CRC tissues and lymph node metastatic tissues than in the adjacent normal tissues. GTF3A was associated with CRC prognosis, and knockdown of the Gtf3a gene impaired CRC cell proliferation, invasion, and motility in vitro and in vivo. Moreover, RNA-Seq analysis revealed that GTF3A might upregulate the expression of Csta, whereas the luciferase activity assay showed that GTF3A bound to the promoter of Csta gene and increased Csta transcription. Furthermore, CSTA regulated the expression of epithelial-mesenchymal transition (EMT) markers.

CONCLUSION

GTF3A increases CSTA expression by binding to the Csta promoter, and increased CSTA level promotes CRC progression by regulating the EMT. Inhibition of GTF3A prevents CRC progression. Therefore, GTF3A is a potential novel therapeutic target and biomarker for CRC.

In Silico, In Vitro, and Clinical Investigations of Cathepsin B and Stefin A mRNA Expression and a Correlation Analysis in Kidney Cancer

The cysteine protease Cathepsin B (CtsB) plays a critical role in multiple signaling pathways, intracellular protein degradation, and processing. Endogenous inhibitors regulate its enzymatic activity, including stefins and other cystatins. Recent data proved that CtsB is implicated in tumor extracellular matrix remodeling, cell invasion, and metastasis: a misbalance between cathepsins and their natural inhibitors is often considered a sign of disease progression. In the present study, we investigated CtsB and stefin A (StfA) expression in renal cell carcinoma (RCC). mRNA analysis unveiled a significant CTSB and STFA increase in RCC tissues compared to adjacent non-cancerogenic tissues and a higher CtsB expression in malignant tumors than in benign renal neoplasms. Further analysis highlighted a positive correlation between CtsB and StfA expression as a function of patient sex, age, tumor size, grade, lymph node invasion, metastasis occurrence, and survival. Alternative overexpression and silencing of CtsB and StfA confirmed the correlation expression between these proteins in human RCC-derived cells through protein analysis and fluorescent microscopy. Finally, the ectopic expression of CtsB and StfA increased RCC cell proliferation. Our data strongly indicated that CtsB and StfA expression play an important role in RCC development by mutually stimulating their expression in RCC progression.

Expression of Cathepsin B and Cystatin A in Oral Lichen Planus

Objective:

Cathepsin B (Cat-B), a cysteine protease, and cystatin A (Cys-A), a protease inhibitor, are involved in the immune response. This study determined Cat-B and Cys-A expression in oral lichen planus (OLP) by immunohistochemistry.

Materials and Methods:

Thirty specimens each of OLP and healthy gingiva (HG) were included. The expression pattern, the number of positive cells, the staining intensity, and the immunoreactive score (IRS) of Cat-B and Cys-A were investigated. The data were analyzed by using unpaired t-test, Chi-square, and Spearman’s rank correlation.

Results:

The Cat-B expression in OLP was observed as cytoplasmic staining in the epithelial cells, whereas Cys-A expression was exhibited in the nucleus and cytoplasm of the epithelium. An increase in Cat-B staining intensity was also observed in the basal cells. Conversely, the high staining intensity of Cys-A was observed in the stratum spinosum, but not the stratum basale. In HG, Cat-B expression demonstrated a relatively consistent intensity in the epithelial layer. The Cys-A expression in HG was similar to OLP with a lower staining intensity. The mean percentage of positive cells and the IRS score of Cat-B and Cys-A in OLP were significantly higher than HG (P < 0.05). There was no correlation between Cat-B and Cys-A levels in OLP. Interestingly, Cat-B expression in erosive OLP was greater than in non-erosive OLP (P < 0.05).

Conclusion:

The Cat-B and Cys-A expression in OLP was more outstanding than in HG, suggesting possible roles for the process of OLP pathogenesis. In addition, Cat-B expression may be an indicator of the disease severity.

Cystatin-B Negatively Regulates the Malignant Characteristics of Oral Squamous Cell Carcinoma Possibly Via the Epithelium Proliferation/Differentiation Program

Disturbance in the proteolytic process is one of the malignant signs of tumors. Proteolysis is highly orchestrated by cysteine cathepsin and its inhibitors. Cystatin-B (CSTB) is a general cysteine cathepsin inhibitor that prevents cysteine cathepsin from leaking from lysosomes and causing inappropriate proteolysis. Our study found that CSTB was downregulated in both oral squamous cell carcinoma (OSCC) tissues and cells compared with normal controls. Immunohistochemical analysis showed that CSTB was mainly distributed in the epithelial structure of OSCC tissues, and its expression intensity was related to the grade classification. A correlation analysis between CSTB and clinical prognosis was performed using gene expression data and clinical information acquired from The Cancer Genome Atlas (TCGA) database. Patients with lower expression levels of CSTB had shorter disease-free survival times and poorer clinicopathological features (e.g., lymph node metastases, perineural invasion, low degree of differentiation, and advanced tumor stage). OSCC cell models overexpressing CSTB were constructed to assess the effects of CSTB on malignant biological behaviors and upregulation of CSTB inhibited cell proliferation, migration, and invasion in vitro. Weighted gene correlation network analysis (WGCNA) and gene set enrichment analysis (GSEA) were performed based on the TCGA data to explore potential mechanisms, and CSTB appeared to correlate with squamous epithelial proliferation-differentiation processes, such as epidermal cell differentiation and keratinization. Moreover, in WGCNA, the gene module most associated with CSTB expression (i.e., the brown module) was also the one most associated with grade classification. Upregulation of CSTB promoted the expression levels of markers (LOR, IVL, KRT5/14, and KRT1/10), reflecting a tendency for differentiation and keratinization in vitro. Gene expression profile data of the overexpressed CSTB cell line were obtained by RNA sequencing (RNA-seq) technology. By comparing the GSEA enrichment results of RNA-seq data (from the OSCC models overexpressing CSTB) and existing public database data, three gene sets (i.e., apical junction, G2/M checkpoint, etc.) and six pathways (e.g., NOTCH signaling pathway, glycosaminoglycan degradation, mismatch repair, etc.) were enriched in the data from both sources. Overall, our study shows that CSTB is downregulated in OSCC and might regulate the malignant characteristics of OSCC via the epithelial proliferation/differentiation program.

Identification of Cysteine Protease Inhibitor CST2 as a Potential Biomarker for Colorectal Cancer

Additional biomarkers for the development and progression of colorectal cancer (CRC) remain to be identified. Hence, the current study aimed to identify potential diagnostic markers for CRC. Analyses of cysteine protease inhibitor [cystatins (CSTs)] expression in CRC samples and its correlation with cancer stage or survival in patients with CRC demonstrated that CRC tissues had greater CST1 and CST2 mRNA expression compared to noncancerous adjacent tissues, while higher CST2 mRNA expression in CRC tissues was correlated with advanced stages and disease-free survival in patients with CRC, encouraging further exploration on the role of CST2 in CRC. Through an online database search and tissue microarray (TMA), we confirmed that CRC samples had higher CST2 expression compared to noncancerous adjacent tissue or normal colorectal tissues at both the mRNA and protein levels. TMA also revealed that colorectal adenoma, CRC, and metastatic CRC tissues exhibited a significantly increased CST2 protein expression. Accordingly, survival analysis demonstrated that the increase in CST2 protein expression was correlated with shorter overall survival of patients with CRC. Moreover, our results found a significant upregulation of CST2 in multiple cancer tissues. Taken together, these findings suggest the potential role of CST2 as a diagnostic and prognostic biomarker for CRC.

Decreased CSTA expression promotes lymphatic metastasis and predicts poor survival in oral squamous cell carcinoma

OBJECTIVE

Herein, we aimed to identify biomarkers that affect lymphatic metastasis of oral squamous cell carcinoma (OSCC) through bioinformatic analysis, and clinicopathological and in vitro verifications.

DESIGN

The OSCC-related gene expression dataset was retrieved from The Cancer Genome Atlas (TCGA) and analyzed to identify differentially expressed genes (DEGs), which were subjected to pathway analysis. Weighted gene co-expression network analysis (WGCNA) and protein-protein interaction (PPI) network analysis were performed to identify hub genes. Expression of potential biomarkers was examined using quantitative real-time polymerase chain reaction, immunohistochemistry, and western blotting. Statistical analyses were performed to determine the association between biomarker expression and clinicopathological characteristics of patients with OSCC. Effects of selected biomarkers on proliferation, migration, and invasion were evaluated using in vitro assays.

RESULTS

For DEGs, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed potential lymphatic metastasis-related biological processes and signaling pathways. Eight hub genes - ALOXE3, CSTA, PLA2G4E, PPL, SPRR1A, SPRR2A, SPRR2D, and SPRR2E, were identified via WGCNA and PPI analyses. CSTA expression was markedly downregulated in primary OSCC tissues, and low CSTA expression significantly correlated with high tumor grade (P =  0.001), nodal metastasis (P =  0.028), and poor overall survival (P <  0.001). CTSA overexpression inhibited OSCC cell migration and invasion in vitro, with little effect on OSCC cell proliferation.

CONCLUSIONS

Our study revealed that CSTA is a promising biomarker and therapeutic target with prognostic implications in patients with OSCC. CSTA may play an essential role in OSCC lymphatic metastasis and tumor differentiation.

Grass carp (Ctenopharyngodon idella) stefin A: Systematic research on its cloning, expression, characterization and tissue distribution

To fully understand the properties of piscine stefins (family I cystatins), the 294-bp stefinA gene from grass carp (Ctenopharyngodon idella, Ci) was cloned and expressed in E. coli BL21 (DE3). After purification by Ni²⁺-NTA agarose affinity chromatography, the CiStefin A protein was tested to have a molecular weight of 11.48 kDa and an isoelectric point of 8.7. The typical motif of the cystatins superfamily was characterized from CiStefin A (QVVQG). CiStefin A specifically inhibited the activity of papain and cathepsin B/L. The K_i value of CiStefin A against papain was 6.5 × 10^-11 M. CiStefin A showed excellent heat and acid-base tolerance. StefinA gene transcription occurred in all tested tissues of grass carp, with the highest level in the hepatopancreas. Immunolocalization staining with an anti-CiStefinA antibody revealed the CiStefinA protein distribution in all tested tissues at various levels. Overall, these results clarified the physical and biochemical properties of grass carp stefin A.

Site-1 protease ablation in the osterix-lineage in mice results in bone marrow neutrophilia and hematopoietic stem cell alterations

Site-1 protease (S1P) ablation in the osterix-lineage in mice drastically reduces bone development and downregulates bone marrow-derived skeletal stem cells. Here we show that these mice also suffer from spina bifida occulta with a characteristic lack of bone fusion in the posterior neural arches. Molecular analysis of bone marrow-derived non-red blood cell cells, via single-cell RNA-Seq and protein mass spectrometry, demonstrate that these mice have a much-altered bone marrow with a significant increase in neutrophils and Ly6C-expressing leukocytes. The molecular composition of bone marrow neutrophils is also different as they express more and additional members of the stefin A (Stfa) family of proteins. In vitro, recombinant Stfa1 and Stfa2 proteins have the ability to drastically inhibit osteogenic differentiation of bone marrow stromal cells, with no effect on adipogenic differentiation. FACS analysis of hematopoietic stem cells show that despite a decrease in hematopoietic stem cells, S1P ablation results in an increased production of granulocyte-macrophage progenitors, the precursors to neutrophils. These observations indicate that S1P has a role in the lineage specification of hematopoietic stem cells and/or their progenitors for development of a normal hematopoietic niche. Our study designates a fundamental requirement of S1P for maintaining a balanced regenerative capacity of the bone marrow niche.

Cancer Cell-Derived Matrisome Proteins Promote Metastasis in Pancreatic Ductal Adenocarcinoma

The prognosis for pancreatic ductal adenocarcinoma (PDAC) remains poor despite decades of effort. The abundant extracellular matrix (ECM) in PDAC comprises a major fraction of the tumor mass and plays various roles in promoting resistance to therapies. However, nonselective depletion of ECM has led to poor patient outcomes. Consistent with that observation, we previously showed that individual matrisome proteins derived from stromal cells correlate with either long or short patient survival. In marked contrast, those derived from cancer cells correlate strongly with poor survival. Here, we studied three cancer cell-derived matrisome proteins that are significantly overrepresented during PDAC progression, AGRN (agrin), SERPINB5 (serine protease inhibitor B5), and CSTB (cystatin B). Using both overexpression and knockdown experiments, we demonstrate that all three are promoters of PDAC metastasis. Furthermore, these proteins operate at different metastatic steps. AGRN promoted epithelial-to-mesenchymal transition in primary tumors, whereas SERPINB5 and CSTB enhanced late steps in the metastatic cascade by elevating invadopodia formation and in vivo extravasation. All three genes were associated with a poor prognosis in human patients and high levels of SERPINB5, secreted by cancer cells and deposited in the ECM, correlated with poor patient prognosis. This study provides strong evidence that cancer cell-derived matrisome proteins can be causal in promoting tumorigenesis and metastasis and lead to poor patient survival. Therefore, compared with the bulk matrix, mostly made by stromal cells, precise interventions targeting cancer cell-derived matrisome proteins, such as AGRN, SERPINB5, and CSTB, may represent preferred potential therapeutic targets. SIGNIFICANCE: This study provides insights into the biological roles of cancer cell-derived matrisome proteins in PDAC and supports the notion that these proteins are protumorigenic and better therapeutic targets.

The Role of Cysteine Cathepsins in Cancer Progression and Drug Resistance

Cysteine cathepsins are lysosomal enzymes belonging to the papain family. Their expression is misregulated in a wide variety of tumors, and ample data prove their involvement in cancer progression, angiogenesis, metastasis, and in the occurrence of drug resistance. However, while their overexpression is usually associated with highly aggressive tumor phenotypes, their mechanistic role in cancer progression is still to be determined to develop new therapeutic strategies. In this review, we highlight the literature related to the role of the cysteine cathepsins in cancer biology, with particular emphasis on their input into tumor biology.

Physcion Synergistically Enhances the Cytotoxicity of Sorafenib in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a common human malignancy. Physcion is a naturally occurring anthraquinone derivative found in plant and marine sources. Our previous studies have indicated that physcion could suppress tumor growth and induce apoptosis in HCC. This study was aimed to investigate the effect of a combination of physcion and sorafenib on HCC. Our findings indicated that physcion could significantly augment the antiproliferative and proapoptotic activities of sorafenib in vitro and in vivo. Mechanistically, the synergistic effect correlates with physcion-induced suppression of Notch3/AKT signaling. This preclinical evidence highlights the potential application of physcion in the treatment of HCC. Anat Rec, 302:2171-2177, 2019. © 2019 American Association for Anatomy.

Cysteine Cathepsin Protease Inhibition: An update on its Diagnostic, Prognostic and Therapeutic Potential in Cancer

In keeping with recent developments in basic research; the importance of the Cathepsins as targets in cancer therapy have taken on increasing importance and given rise to a number of key areas of interest in the clinical setting. In keeping with driving basic research in this area in a translational direction; recent findings have given rise to a number of exciting developments in the areas of cancer diagnosis; prognosis and therapeutic development. As a fast-moving area of research; the focus of this review brings together the latest findings and highlights the translational significance of these developments.

Transforming growth factor‑β/miR‑143‑3p/cystatin B axis is a therapeutic target in human ovarian cancer

We previously reported that cystatin B (CSTB) is a progression marker of human ovarian cancer (OC); however, the regulatory mechanism of CSTB and its function in OC remain unclear. The present study aimed to explore the mechanism underlying transforming growth factor-β (TGF‑β) 1‑mediated CSTB regulation, and to examine the function of CSTB on OC cell proliferation and apoptosis. Using the online program, miRWalk, a microRNA (miR)‑143‑3p was detected, which contains a homologous sequence of the potential binding site to the 3'‑untranslated region (3'‑UTR) of CSTB. A dual‑luciferase reporter assay confirmed the interaction between miR‑143‑3p and CSTB 3'‑UTR. Treating OC cells with miR‑143‑3p mimics or inhibitors resulted in a decrease or an increase of CSTB expression at mRNA and protein levels, respectively. Additionally, CSTB was significantly overexpressed, whereas miR‑143‑3p was downregulated in human OC tissues compared with normal ovarian tissues. A negative correlation between miR‑143‑3p and CSTB mRNA expression was observed in ovarian malignant tumors. The levels of primary and mature miR‑143‑3p expression were upregulated in OC cells after TGF‑β1 treatment; the action of TGF‑β1 was abolished in the presence of an inhibitor of TGF‑β type I receptor. These results indicated an axis between TGF‑β, miR‑143‑3p and CSTB in OC cells. Furthermore, high levels of CSTB expression were associated with the poor overall survival of patients with OC. Knockdown of CSTB resulted in a decrease in OC cell proliferation and arrested cells in G2/M phase. In addition, suppression of CSTB induced cell apoptosis. In conclusion, CSTB was overexpressed and miR‑143‑3p was downregulated in ovarian malignant tumors. Mature miR‑143‑3p directly bound CSTB 3'‑UTR, leading to a decrease in CSTB expression in OC cells, which was regulated by TGF‑β1. Our findings suggest the potential therapeutic application of targeting the TGF‑β/miR‑143‑3p/CSTB axis for treating patients with OC.

Investigation of the clinical significance and prospective molecular mechanisms of cystatin genes in patients with hepatitis B virus‑related hepatocellular carcinoma

The present study aimed to investigate the clinical significance and prospective molecular mechanism of cystatin (CST) genes in patients with hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). The role of CST genes in the molecular mechanism of HCC was revealed through bioinformatics analysis. The clinical significance of CST genes was investigated using GSE14520-derived data from patients with HBV-related HCC. Gene set enrichment analysis (GSEA) was used to identify pathways in which the CST genes were enriched, as well as the association between these pathways and HCC. The expression levels of CST1, CST2, CST5, CSTA and CSTB genes were higher in HCC tissue compared with in normal tissue; conversely, CST3 and CST7 were reduced in HCC tissue. Subsequent receiver operating characteristic analysis of the CST genes demonstrated that CST7 and CSTB genes may function as potential diagnostic markers for HCC. Furthermore, the expression levels of CST6 and CST7 were strongly associated with recurrence-free survival and overall survival of patients with HBV-related HCC. GSEA of the CST genes revealed that CST7 was significantly enriched in tumor evasion and tolerogenicity, cancer progenitors, liver cancer late recurrence, liver cancer progression and several liver cancer subclasses. In addition, CST genes demonstrated homology in terms of protein structure and were revealed to be strongly co-expressed. The present findings suggested that CST7 and CSTB genes may serve as potential prognostic and diagnostic biomarkers for HCC.

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.

Salivary Cystatins: Exploring New Post-Translational Modifications and Polymorphisms by Top-Down High-Resolution Mass Spectrometry

Cystatins are a complex family of cysteine peptidase inhibitors. In the present study, various proteoforms of cystatin A, cystatin B, cystatin S, cystatin SN, and cystatin SA were detected in the acid-soluble fraction of human saliva and characterized by a top-down HPLC-ESI-MS approach. Proteoforms of cystatin D were also detected and characterized by an integrated top-down and bottom-up strategy. The proteoforms derive from coding sequence polymorphisms and post-translational modifications, in particular, phosphorylation, N-terminal processing, and oxidation. This study increases the current knowledge of salivary cystatin proteoforms and provides the basis to evaluate possible qualitative/quantitative variations of these proteoforms in different pathological states and reveal new potential salivary biomarkers of disease. Data are available via ProteomeXchange with identifier PXD007170.

Cysteine cathepsins as a prospective target for anticancer therapies-current progress and prospects

Cysteine cathepsins (CTS), being involved in both physiological and pathological processes, play an important role in the human body. During the last 30 years, it has been shown that CTS are highly upregulated in a wide variety of cancer types although they have received a little attention as a potential therapeutic target as compared to serine or metalloproteinases. Studies on the increasing problem of neoplastic progression have revealed that secretion of cell-surface- and intracellular cysteine proteases is aberrant in tumor cells and has an impact on their growth, invasion, and metastasis by taking part in tumor angiogenesis, in apoptosis, and in events of inflammatory and immune responses. Considering the role of CTS in carcinogenesis, inhibition of these enzymes becomes an attractive strategy for cancer therapy. The downregulation of natural CTS inhibitors (CTSsis), such as cystatins, observed in various types of cancer, supports this claim. The intention of this review is to highlight the relationship of CTS with cancer and to present illustrations that explain how some of their inhibitors affect processes related to neoplastic progression.

Clinical features of cystatin A expression in patients with pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the most lethal malignancy known, with an extremely poor prognosis due to the lack of an efficient diagnostic scheme and no radical treatment option, except surgery. Therefore, understanding the pathophysiology of, and finding a novel biomarker to detect, PDAC should be prioritized. We observed an increase in mRNA expression of the cysteine protease inhibitor cystatin A (CSTA) in CD4⁺ T cells in peripheral blood cells of nine patients with PDAC, compared with the expression in seven healthy volunteers. Moreover, we confirmed significantly higher CSTA mRNA expression in a larger cohort of 41 patients with PDAC compared with that in 20 healthy volunteers. Correspondingly, the serum CSTA concentrations in 36 patients with PDAC were higher than those in 37 healthy volunteers, and this increase was correlated with PDAC clinical stage. Furthermore, the expression of CSTA and cathepsin B, which is a lysosomal cysteine protease inhibited by CSTA, was observed in tumor tissues and tumor‐infiltrating immune cells in 20 surgically resected PDAC tissues by immunohistochemical staining. Expression of CSTA was detected in some tumor tissues and many tumor‐infiltrating immune cells. Cathepsin B expression was also observed in most tumor tissues and tumor‐infiltrating immune cells. In conclusion, CSTA and its substrate cathepsin B are involved in PDAC‐related inflammation. The increment of CSTA expression in peripheral blood of patients with PDAC may have a potential role as a PDAC immunopathologic biomarker.