Transcription of human cathepsin B is mediated by Sp1 and Ets family factors in glioma

Recent discovery of natural substances with cathepsin L-inhibitory activity for cancer metastasis suppression

Cathepsin L (CTSL), a cysteine cathepsin protease of the papain superfamily, plays a crucial role in cancer progression and metastasis. Dysregulation of CTSL is frequently observed in tumor malignancies, leading to the degradation of extracellular matrix and facilitating epithelial-mesenchymal transition (EMT), a key process in malignant cancer metastasis. This review mainly provides a comprehensive information about recent findings on natural inhibitors targeting CTSL and their anticancer effects, which have emerged as potent anticancer therapeutic agents or metastasis-suppressive adjuvants. Specifically, inhibitors are categorized into small-molecule and macromolecule inhibitors, with a particular emphasis on cathepsin propeptide-type macromolecules. Additionally, the article explores the molecular mechanisms of CTSL involvement in cancer metastasis, highlighting its regulation at transcriptional, translational, post-translational, and epigenetic levels. This work underscores the importance of understanding natural CTSL inhibitors and provides researchers with practical insights to advance the relevant fields and discover novel CTSL-targeting inhibitors from natural sources.

Cathepsin V: Molecular characteristics and significance in health and disease

Human cysteine cathepsins form a family of eleven proteases (B, C, F, H, K, L, O, S, V, W, X/Z) that play important roles in a considerable number of biological and pathophysiological processes. Among them, cathepsin V, also known as cathepsin L2, is a lysosomal enzyme, which is mainly expressed in cornea, thymus, heart, brain, and skin. Cathepsin V is a multifunctional endopeptidase that is involved in both the release of antigenic peptides and the maturation of MHC class II molecules and participates in the turnover of elastin fibrils as well in the cleavage of intra- and extra-cellular substrates. Moreover, there is increasing evidence that cathepsin V may contribute to the progression of diverse diseases, due to the dysregulation of its expression and/or its activity. For instance, increased expression of cathepsin V is closely correlated with malignancies (breast cancer, squamous cell carcinoma, or colorectal cancer) as well vascular disorders (atherosclerosis, aortic aneurysm, hypertension) being the most prominent examples. This review aims to shed light on current knowledge on molecular aspects of cathepsin V (genomic organization, protein structure, substrate specificity), its regulation by protein and non-protein inhibitors as well to summarize its expression (tissue and cellular distribution). Then the core biological and pathophysiological roles of cathepsin V will be depicted, raising the question of its interest as a valuable target that can open up pioneering therapeutic avenues.

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.

Phosphorylation-mediated interaction between human E26 transcription factor 1 and specific protein 1 is required for tumor cell migration

Transcription factors, human E26 transcription factor 1 (Ets1) and specific protein 1 (Sp1), are known to induce gene expression in tumorigenicity. High Ets1 expression is often associated with colorectal tumorigenesis. In this study, we discover that metastasis and clone formation in SW480 cells mainly depend on the direct interaction between Ets1 and Sp1 instead of high Ets1 expression. The interaction domains are further addressed to be the segment at Sp1(626-708) and the segment at Ets1(244-331). In addition, the phosphorylation inhibition of Ets1 at Tyr283 by either downregulation of Src kinase or Src family inhibitor treatment decreases the interaction between Sp1 and Ets1 and suppresses SW480 migration. Either administration or overexpression of the peptides harboring the interaction segment strongly inhibits the colony formation and migration of SW480 cells. Our findings suggest that the interaction between Ets1 and Sp1 rather than Ets1 alone promotes transformation in SW480 cells and provide new insight into the Ets1 and Sp1 interaction as an antitumour target in SW480 cells.

Gene Networks of Hyperglycemia, Diabetic Complications, and Human Proteins Targeted by SARS-CoV-2: What Is the Molecular Basis for Comorbidity?

People with diabetes are more likely to have severe COVID-19 compared to the general population. Moreover, diabetes and COVID-19 demonstrate a certain parallelism in the mechanisms and organ damage. In this work, we applied bioinformatics analysis of associative molecular networks to identify key molecules and pathophysiological processes that determine SARS-CoV-2-induced disorders in patients with diabetes. Using text-mining-based approaches and ANDSystem as a bioinformatics tool, we reconstructed and matched networks related to hyperglycemia, diabetic complications, insulin resistance, and beta cell dysfunction with networks of SARS-CoV-2-targeted proteins. The latter included SARS-CoV-2 entry receptors (ACE2 and DPP4), SARS-CoV-2 entry associated proteases (TMPRSS2, CTSB, and CTSL), and 332 human intracellular proteins interacting with SARS-CoV-2. A number of genes/proteins targeted by SARS-CoV-2 (ACE2, BRD2, COMT, CTSB, CTSL, DNMT1, DPP4, ERP44, F2RL1, GDF15, GPX1, HDAC2, HMOX1, HYOU1, IDE, LOX, NUTF2, PCNT, PLAT, RAB10, RHOA, SCARB1, and SELENOS) were found in the networks of vascular diabetic complications and insulin resistance. According to the Gene Ontology enrichment analysis, the defined molecules are involved in the response to hypoxia, reactive oxygen species metabolism, immune and inflammatory response, regulation of angiogenesis, platelet degranulation, and other processes. The results expand the understanding of the molecular basis of diabetes and COVID-19 comorbidity.

Cathepsins in neuronal plasticity

Proteases comprise a variety of enzymes defined by their ability to catalytically hydrolyze the peptide bonds of other proteins, resulting in protein lysis. Cathepsins, specifically, encompass a class of at least twenty proteases with potent endopeptidase activity. They are located subcellularly in lysosomes, organelles responsible for the cell’s degradative and autophagic processes, and are vital for normal lysosomal function. Although cathepsins are involved in a multitude of cell signaling activities, this chapter will focus on the role of cathepsins (with a special emphasis on Cathepsin B) in neuronal plasticity. We will broadly define what is known about regulation of cathepsins in the central nervous system and compare this with their dysregulation after injury or disease. Importantly, we will delineate what is currently known about the role of cathepsins in axon regeneration and plasticity after spinal cord injury. It is well established that normal cathepsin activity is integral to the function of lysosomes. Without normal lysosomal function, autophagy and other homeostatic cellular processes become dysregulated resulting in axon dystrophy. Furthermore, controlled activation of cathepsins at specialized neuronal structures such as axonal growth cones and dendritic spines have been positively implicated in their plasticity. This chapter will end with a perspective on the consequences of cathepsin dysregulation versus controlled, localized regulation to clarify how cathepsins can contribute to both neuronal plasticity and neurodegeneration.

ETS1-activated SNHG10 exerts oncogenic functions in glioma via targeting miR-532-3p/FBXL19 axis

Background

In past few years, long non-coding RNAs (lncRNAs) have been reported to play regulatory roles during cancer progression. LncRNA SNHG10 has been explored in several sorts of cancers. However, its detailed role and mechanism are still not well understood in glioma.

Methods

Expression levels of genes were evaluated by RT-qPCR. EdU, TUNEL, sphere formation, wound healing and transwell assays appraised the effect of SNHG10 on glioma cellular processes. The interaction between molecules was examined by ChIP, RIP, RNA pull down and luciferase reporter assays.

Results

High level of SNHG10 was detected in glioma cells. Functional assay confirmed that SNHG10 promoted the proliferation, migration, invasion and stemness of glioma cells. Moreover, miR-532-3p was validated to bind with SNHG10 and expressed at a low level in glioma cells. Importantly, miR-532-3p exerted inhibitory functions in glioma. Furthermore, it was found that FBXL19 targeted by miR-532-3p facilitated cell growth and stemness in glioma, and that SNHG10 worked in glioma by increasing FBXL19 expression through sequestering miR-532-3p. More importantly, ETS1 promoted the transcription of SNHG10 and it mediated contribution to the malignant behaviors of glioma cells by SNHG10/miR-532-3p/FBXL19 signaling.

Conclusion

SNHG10 was transcriptionally activated by ETS1 and played an oncogenic role in glioma by sponging miR-532-3p and up-regulating FBXL19.

Cathepsin B is highly expressed in pancreatic cancer stem-like cells and is associated with patients' surgical outcomes

Cancer stem-like cells (CSLCs) in solid tumors are resistant to conventional chemotherapy and molecularly targeted therapy, which is thought to contribute to cancer recurrence and metastasis. The present study aimed to identify biomarkers for pancreatic CSLCs (P-CSLCs). Using our previously reported methods, P-CSLC-enriched populations were generated from pancreatic cancer cell lines. The protein expression profiles of these populations were compared with those of parental cells using two-dimensional electrophoresis, tandem mass spectrometry, flow cytometry and immunohistochemistry. Protein expression in surgical specimens was also evaluated for relationships with clinical outcomes. A lysosomal cysteine protease, cathepsin B (CTSB), was significantly upregulated in P-CSLCs compared with that in the parental cells, as shown using western blotting. Flow cytometry analysis also confirmed that CTSB was more highly expressed on the surface of P-CSLCs compared with that on parental cells. Moreover, PCLCs had elevated cellular secretions of CTSB compared with the parental cells. Finally, CTSB expression was evaluated in 69 resected tumor specimens, and high expression was associated with the patients' clinicopathological features and surgical outcomes. The present results suggested that CTSB is a biomarker for poor survival in patients with pancreatic cancer, which is possibly associated with P-CSLCs. This novel biomarker may also have potential as a therapeutic target.

The Ins and Outs of Cathepsins: Physiological Function and Role in Disease Management

Cathepsins are the most abundant lysosomal proteases that are mainly found in acidic endo/lysosomal compartments where they play a vital role in intracellular protein degradation, energy metabolism, and immune responses among a host of other functions. The discovery that cathepsins are secreted and remain functionally active outside of the lysosome has caused a paradigm shift. Contemporary research has unraveled many versatile functions of cathepsins in extralysosomal locations including cytosol and extracellular space. Nevertheless, extracellular cathepsins are majorly upregulated in pathological states and are implicated in a wide range of diseases including cancer and cardiovascular diseases. Taking advantage of the differential expression of the cathepsins during pathological conditions, much research is focused on using cathepsins as diagnostic markers and therapeutic targets. A tailored therapeutic approach using selective cathepsin inhibitors is constantly emerging to be safe and efficient. Moreover, recent development of proteomic-based approaches for the identification of novel physiological substrates offers a major opportunity to understand the mechanism of cathepsin action. In this review, we summarize the available evidence regarding the role of cathepsins in health and disease, discuss their potential as biomarkers of disease progression, and shed light on the potential of extracellular cathepsin inhibitors as safe therapeutic tools.

'Patchiness' and basic cancer research: unravelling the proteases

The recent developments in Cathepsin protease research have unveiled a number of key observations which are fundamental to further our understanding of normal cellular homeostasis and disease. By far, the most interesting and promising area of Cathepsin biology stems from how these proteins are linked to the fate of living cells through the phenomenon of Lysosomal Leakage and Lysosomal Membrane Permeabilisation. While extracellular Cathepsins are generally believed to be of central importance in tumour progression, through their ability to modulate the architecture of the Extracellular Matrix, intracellular Cathepsins have been established as being of extreme significance in mediating cell death through Apoptosis. With these two juxtaposed key research areas in mind, the focus of this review highlights recent advancements in how this fast-paced area of Cathepsin research has recently evolved in the context of their mechanistic regulation in cancer research. Abbreviations : ECM, Extracellular Matrix; MMP, Matrix Metalloproteases; LL, Lysosomal Leakage; LMP, Lysosomal Membrane Permeabilisation; LMA, Lysosomorphic Agents; BC, Breast Cancer; ASM, Acid Sphingomyelinase; TNF-α, Tumor Necrosis Factor-alpha; LAMP, Lysosomal Associated membrane Protein; PCD, Programmed Cell Death; PDAC, Pancreatic Ductal Adenocarcinoma; ROS, Reactive Oxygen Species; aa, amino acids.

Abl and Arg mediate cysteine cathepsin secretion to facilitate melanoma invasion and metastasis

The incidence of melanoma is increasing, particularly in young women, and the disease remains incurable for many because of its aggressive, metastatic nature and its high rate of resistance to conventional, targeted, and immunological agents. Cathepsins are proteases that are critical for melanoma progression and therapeutic resistance. Intracellular cathepsins cleave or degrade proteins that restrict cancer progression, whereas extracellular cathepsins directly cleave the extracellular matrix and activate proinvasive proteases in the tumor microenvironment. Cathepsin secretion is markedly increased in cancer cells. We investigated the signaling pathways leading to increased cathepsin secretion in melanoma cells. We found that the nonreceptor tyrosine kinases Abl and Arg (Abl/Arg) promoted the secretion of cathepsin B and cathepsin L by activating transcription factors (namely, Ets1, Sp1, and NF-κB/p65) that have key roles in the epithelial-mesenchymal transition (EMT), invasion, and therapeutic resistance. In some melanoma cell lines, Abl/Arg promoted the Ets1/p65-induced secretion of cathepsin B and cathepsin L in a kinase-independent manner, whereas in other melanoma lines, Abl/Arg promoted the kinase-dependent, Sp1/Ets1/p65-mediated induction of cathepsin L secretion and the Sp1/p65-mediated induction of cathepsin B secretion. As an indication of clinical relevance, the abundance of mRNAs encoding Abl/Arg, Sp1, Ets1, and cathepsins was positively correlated in primary melanomas, and Abl/Arg-driven invasion in culture and metastasis in vivo required cathepsin secretion. These data suggest that drugs targeting Abl kinases, many of which are FDA-approved, might inhibit cathepsin secretion in some melanomas and potentially other aggressive cancers harboring activated Abl kinases.

Mammalian Sterile 20-like Kinase 1 (Mst1) Enhances the Stability of Forkhead Box P3 (Foxp3) and the Function of Regulatory T Cells by Modulating Foxp3 Acetylation

Regulatory T cells (Tregs) play crucial roles in maintaining immune tolerance. The transcription factor Foxp3 is a critical regulator of Treg development and function, and its expression is regulated at both transcriptional and post-translational levels. Acetylation by lysine acetyl transferases/lysine deacetylases is one of the main post-translational modifications of Foxp3, which regulate Foxp3's stability and transcriptional activity. However, the mechanism(s) by which the activities of these lysine acetyl transferases/lysine deacetylases are regulated to preserve proper Foxp3 acetylation during Treg development and maintenance of Treg function remains to be determined. Here we report that Mst1 can enhance Foxp3 stability, its transcriptional activity, and Treg function by modulating the Foxp3 protein at the post-translational level. We discovered that Mst1 could increase the acetylation of Foxp3 by inhibiting Sirt1 activity, which requires the Mst1 kinase activity. We also found that Mst1 could attenuate Sirt1-mediated deacetylation of Foxp3 through directly interacting with Foxp3 to prevent or interfere the interaction between Sirt1 and Foxp3. Therefore, Mst1 can regulate Foxp3 stability in kinase-dependent and kinase-independent manners. Finally, we showed that treatment of Mst1(-/-) Tregs with Ex-527, a Sirt1-specific inhibitor, partially restored the suppressive function of Mst1(-/-) Tregs. Our studies reveal a novel mechanism by which Mst1 enhances Foxp3 expression and Treg function at the post-translational level.

Cysteine cathepsin proteases: regulators of cancer progression and therapeutic response

Cysteine cathepsin protease activity is frequently dysregulated in the context of neoplastic transformation. Increased activity and aberrant localization of proteases within the tumour microenvironment have a potent role in driving cancer progression, proliferation, invasion and metastasis. Recent studies have also uncovered functions for cathepsins in the suppression of the response to therapeutic intervention in various malignancies. However, cathepsins can be either tumour promoting or tumour suppressive depending on the context, which emphasizes the importance of rigorous in vivo analyses to ascertain function. Here, we review the basic research and clinical findings that underlie the roles of cathepsins in cancer, and provide a roadmap for the rational integration of cathepsin-targeting agents into clinical treatment.

Cathepsin B: multiple roles in cancer

Proteases, including intracellular proteases, play roles at many different stages of malignant progression. Our focus here is cathepsin B, a lysosomal cysteine cathepsin. High levels of cathepsin B are found in a wide variety of human cancers, levels that often induce secretion and association of cathepsin B with the tumor cell membrane. In experimental models, such as transgenic models of murine pancreatic and mammary carcinomas, causal roles for cathepsin B have been demonstrated in initiation, growth/tumor cell proliferation, angiogenesis, invasion, and metastasis. Tumor growth in transgenic models is promoted by cathepsin B in tumor-associated cells, for example, tumor-associated macrophages, as well as in tumor cells. In transgenic models, the absence of cathepsin B has been associated with enhanced apoptosis, yet cathepsin B also has been shown to contribute to apoptosis. Cathepsin B is part of a proteolytic pathway identified in xenograft models of human glioma; targeting only cathepsin B in these tumors is less effective than targeting cathepsin B in combination with other proteases or protease receptors. Understanding the mechanisms responsible for increased expression of cathepsin B in tumors and association of cathepsin B with tumor cell membranes is needed to determine whether targeting cathepsin B could be of therapeutic benefit.

Mst1/Mst2 regulate development and function of regulatory T cells through modulation of Foxo1/Foxo3 stability in autoimmune disease

Foxp3 expression and regulatory T cell (Treg) development are critical for maintaining dominant tolerance and preventing autoimmune diseases. Human MST1 deficiency causes a novel primary immunodeficiency syndrome accompanied by autoimmune manifestations. However, the mechanism by which Mst1 controls immune regulation is unknown. In this article, we report that Mst1 regulates Foxp3 expression and Treg development/function and inhibits autoimmunity through modulating Foxo1 and Foxo3 (Foxo1/3) stability. We have found that Mst1 deficiency impairs Foxp3 expression and Treg development and function in mice. Mechanistic studies reveal that Mst1 enhances Foxo1/3 stability directly by phosphorylating Foxo1/3 and indirectly by attenuating TCR-induced Akt activation in peripheral T cells. Our studies have also shown that Mst1 deficiency does not affect Foxo1/3 cellular localization in CD4 T cells. In addition, we show that Mst1(-/-) mice are prone to autoimmune disease, and mutant phenotypes, such as overactivation of naive T cells, splenomegaly, and autoimmune pathological changes, are suppressed in Mst1(-/-) bone marrow chimera by cotransplanted wt Tregs. Finally, we demonstrate that Mst1 and Mst2 play a partially redundant role in Treg development and autoimmunity. Our findings not only identify Mst kinases as the long-searched-for factors that simultaneously activate Foxo1/3 and inhibit TCR-stimulated Akt downstream of TCR signaling to promote Foxp3 expression and Treg development, but also shed new light on understanding and designing better therapeutic strategies for MST1 deficiency-mediated human immunodeficiency syndrome.

Cathepsin B as a cancer target

INTRODUCTION

Cathepsin B is of significant importance to cancer therapy as it is involved in various pathologies and oncogenic processes in humans. Numerous studies have shown that abnormal regulation of cathepsin B overexpression is correlated with invasive and metastatic phenotypes in cancers. Cathepsin B is normally associated with the lysosomes involved in autophagy and immune response, but its aberrant expression has been shown to lead to cancers.

AREAS COVERED

This review highlights the oncogenic role of cathepsin B, discusses the regulation of cathepsin B in light of oncogenesis, discusses the role of cathepsin B as a signaling molecule, and highlights the therapeutic potential of targeting cathepsin B.

EXPERT OPINION

Targeting cathepsin B alone does not appear to abolish tumor growth, and this is probably because cathepsin B appears to have diverse functions and influence numerous pathways. It is not clear whether global suppression of cathepsin B activity or expression would produce unintended effects or cause the activation or suppression of unwanted pathways. A localized approach for targeting the expression of cathepsin B would be more relevant. Moreover, a combination of targeting cathepsin B with other relevant oncogenic molecules has significant therapeutic potential.

Microarray-based analysis of gene regulation by transcription factors and microRNAs in glioma

Transcription factor (TF) and microRNA (miRNA) are two best characterized gene regulators that have been found to play an important role in gene regulation. However, high throughput screening the interaction relationships between transcription factors, microRNAs, and target genes in gliomas remains rare. Using GSE16666 and GSE13091 datasets downloaded from Gene Expression Omnibus data, we first screened the differentially expressed genes in gliomas. We explored the regulation relationship among TFs, miRNAs and target genes by different algorithms. The underlying molecular mechanisms of these crucial target genes were investigated by Gene Ontology function and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. Our study has developed three regulation relationships between two TFs and three miRNAs, including TP53/hsa-mir-155, TP53/hsa-mir-125b, and KLF2/hsa-mir-126. In addition, we also constructed a regulation network of the target genes by transcription factors and miRNAs. Some of them had been demonstrated to be involved in glioma progression via various pathways. For example, ATP2B2 target gene could be regulated by has-mir-181a to involve in calcium signaling pathway. RB1 could be regulated by has-miR-26a to participate in pathways in cancer. Smad7 could be regulated by has-miR-21 via intracellular TGF-β signal transduction. We constructed a comprehensive regulatory network which was found to play an important role in gliomas progression.

PPARα agonist Wy14643 suppresses cathepsin B in human endothelial cells via transcriptional, post-transcriptional and post-translational mechanisms

Cathepsin B has been shown to be important in angiogenesis; therefore, understanding its regulation in endothelial cells should provide fundamental information that will aid in the development of new treatment options. Peroxisome proliferator-activated receptors (PPARs) have been shown to have anti-inflammatory, anti-angiogenic and anti-tumorigenic properties. We explored the influence of a PPARα agonist on cathepsin B expression in human endothelial cells. The PPARα agonist, Wy14643, was found to inhibit cathepsin B protein expression. Further studies demonstrated the Wy14643-dependent but PPARα-independent suppression of cathepsin B. This has been previously described for other PPAR agonists. Wy14643 suppressed the accumulation of cathepsin B mRNA, which was accompanied by the selective suppression of a 5'-alternative splice variant. Consistent with these results, luciferase promoter assays and electrophoretic mobility shift analysis demonstrated that the suppression was facilitated by reduced binding of the transcription factors USF1/2 to an E-box within the cathepsin B promoter. Additionally, Wy14643 treatment resulted in a reduction in cathepsin B half-life, suggesting a posttranslational regulatory mechanism. Overall, our results suggest that the PPARα-dependent anti-angiogenic action of Wy14643 seems to be mediated, in part, by Wy14643-dependent but PPARα-independent regulation of cathepsin B expression.

ErbB2-driven breast cancer cell invasion depends on a complex signaling network activating myeloid zinc finger-1-dependent cathepsin B expression

Aberrant ErbB2 receptor tyrosine kinase activation in breast cancer is strongly linked to an invasive disease. The molecular basis of ErbB2-driven invasion is largely unknown. We show that cysteine cathepsins B and L are elevated in ErbB2 positive primary human breast cancer and function as effectors of ErbB2-induced invasion in vitro. We identify Cdc42-binding protein kinase beta, extracellular regulated kinase 2, p21-activated protein kinase 4, and protein kinase C alpha as essential mediators of ErbB2-induced cysteine cathepsin expression and breast cancer cell invasiveness. The identified signaling network activates the transcription of cathepsin B gene (CTSB) via myeloid zinc finger-1 transcription factor that binds to an ErbB2-responsive enhancer element in the first intron of CTSB. This work provides a model system for ErbB2-induced breast cancer cell invasiveness, reveals a signaling network that is crucial for invasion in vitro, and defines a specific role and targets for the identified serine-threonine kinases.

Acid ceramidase-mediated production of sphingosine 1-phosphate promotes prostate cancer invasion through upregulation of cathepsin B

Invasiveness is one of the key features of aggressive prostate cancer; however, our understanding of the precise mechanisms effecting invasion remains limited. The ceramide hydrolyzing enzyme acid ceramidase (AC), overexpressed in most prostate tumors, causes an aggressive and invasive phenotype through downstream effectors that have not yet been well characterized. Here, we demonstrate that AC, through generation of sphingosine-1-phosphate (S1P), promotes Ets1 nuclear expression and binding to the promoter region of matrix-degrading protease cathepsin B. Through confocal microscopy and flow cytometry, we found that AC overexpression promotes pericellular localization of cathepsin B and its translocation to the outer leaflet of the cell membrane. AC overexpressing cells have an increased abundance of cathepsin B-enriched invasive structures and enhanced ability to invade through a collagen matrix, but not in the presence of an inhibitor of cathepsin B. In human prostate tissues, AC and cathepsin B overexpression were strongly associated and may relate to poor outcome. These results demonstrate a novel pathway by which AC, through S1P, promotes an invasive phenotype in prostate cancer by causing overexpression and secretion of cathepsin B through activation and nuclear expression of Ets1. As prostate cancer prognosis is dramatically worse when invasion has occurred, this study provides critical insight into the progression toward lethal prostate cancer.

Reprogramming of the tumour microenvironment by stromal PTEN-regulated miR-320

Phosphatase and tensin homolog deleted on chromosome ten (Pten) in stromal fibroblasts suppresses epithelial mammary tumors, but the underlying molecular mechanisms remain unknown. Using proteomic and expression profiling, we show that Pten loss from mammary stromal fibroblasts activates an oncogenic secretome that orchestrates the transcriptional reprogramming of other cell types in the microenvironment. Downregulation of miR-320 and upregulation of one of its direct targets, ETS2, are critical events in Pten-deleted stromal fibroblasts responsible for inducing this oncogenic secretome, which in turn promotes tumor angiogenesis and tumor cell invasion. Expression of the Pten-miR-320-Ets2 regulated secretome distinguished human normal breast stroma from tumor stroma and robustly correlated with recurrence in breast cancer patients. This work reveals miR-320 as a critical component of the Pten tumor suppressor axis that acts in stromal fibroblasts to reprogram the tumor microenvironment and curtail tumor progression.

Systemic administration of ribbon-type decoy oligodeoxynucleotide against nuclear factor κB and ets prevents abdominal aortic aneurysm in rat model

Currently, there is no effective clinical treatment to prevent abdominal aortic aneurysm (AAA). To develop a novel therapeutic approach, we modified decoy oligodeoxynucleotide (ODN) against nuclear factor κB (NFκB) and ets, to a ribbon-shaped circular structure without chemical modification, to increase its resistance to endonuclease for systemic administration. Intraperitoneal administration of ribbon-type decoy ODNs (R-ODNs) was performed in an elastase-induced rat AAA model. Fluorescent isothiocyanate (FITC)-labeled R-ODNs could be detected in macrophages migrating into the aneurysm wall, and NFκB and ets activity were simultaneously inhibited by chimeric R-ODN. Treatment with chimeric R-ODN significantly inhibited aortic dilatation, whereas conventional phosphorothioate decoy ODN failed to prevent aneurysm formation. Significant preservation of elastic fibers was observed with chimeric R-ODN, accompanied by a reduction of secretion of several proteases from macrophages. Activation of matrix metalloproteinase (MMP)-9 and MMP-12, but not MMP-2, was suppressed in the aneurysm wall by chimeric R-ODN, whereas recruitment of macrophages was not inhibited. Treatment with chimeric R-ODN also inhibited the secretion of cathepsin B and K from macrophages. Overall, the present study demonstrated that systemic administration of chimeric R-ODNs prevented aneurysm formation in a rat model. Further modification of the decoy strategy would provide a means of less invasive molecular therapy for human AAA.

Effects of Sp1 overexpression on cultured human corneal stromal cells

Sp1, a transcription factor, is upregulated in keratoconus, a cornea-thinning disease. Keratoconus corneas have also been shown to contain increased levels of degradative enzymes such as cathepsin B and decreased proteinase inhibitors such as alpha1-proteinase inhibitor (alpha1-PI). We transfected cultured human corneal stromal cells to overexpress Sp1. The resulting effects on cathepsin B and alpha1-PI levels as well as the cellular proliferative and apoptotic activities were examined by Western blotting and cytochemical staining. It was found that the Sp1 transfected cells contained a greater amount of cathepsin B than did mock transfected controls. The activity of cathepsin B was also increased. By contrast, the protein level of alpha1-PI was lowered in corneal stromal cells upon Sp1 overexpression. The Sp1-induced alterations thus mimicked closely those observed in keratoconus, supporting the notion that Sp1 upregulation may be a key factor contributing directly to the disease development. Furthermore, the apoptotic activity was unaffected in Sp1 transfectants but the proliferation was inhibited, consistent with the idea that Sp1 may play a role in differentiation of corneal cells.

Overexpression of protease-activated receptor-1 contributes to melanoma metastasis via regulation of connexin 43

Protease-activated receptor-1 (PAR-1) is a key player in melanoma metastasis with higher expression seen in metastatic melanoma cell lines and tissue specimens. cDNA microarray and Western blot analyses reveal that the gap junctional intracellular communication molecule connexin 43 (Cx-43), known to be involved in tumor cell diapedesis and attachment to endothelial cells, is significantly decreased after PAR-1 silencing in metastatic melanoma cell lines. Furthermore, Cx-43 promoter activity was significantly inhibited in PAR-1-silenced cells, suggesting that PAR-1 regulates Cx-43 at the transcriptional level. Chromatin immunoprecipitation studies showed a reduction in the binding of SP-1 and AP-1 transcription factors to the promoter of Cx-43. Both transcription factors have been shown previously to be required for maximal Cx-43 promoter activity. These results were corroborated by mutating the AP-1 and SP-1 binding sites resulting in decreased Cx-43 promoter activity in PAR-1-positive cells. Moreover, as Cx-43 has been shown to facilitate arrest of circulating tumor cells at the vascular endothelium, melanoma cell attachment to endothelial cells was significantly decreased in PAR-1-silenced cells, with this effect being abrogated after PAR-1 rescue. Herein, we report that up-regulation of PAR-1 expression, seen in melanoma progression, mediates high levels of Cx-43 expression. As both SP-1 and AP-1 transcription factors act as positive regulators of Cx-43, our data provide a novel mechanism for the regulation of Cx-43 expression by PAR-1. Indeed, Cx-43 expression was restored following PAR-1 rescue in PAR-1-silenced cells. Taken together, our data support the tumor promoting function of Cx-43 in melanoma.

Murine and human cathepsin B exhibit similar properties: possible implications for drug discovery

Validation of drug targets and subsequent preclinical studies are usually carried out on animal disease models, with mouse being the most commonly used. However, results from mouse models cannot always be directly related to human disease. Major discrepancies between the properties of murine and human variants were observed during the evaluation of compounds targeting cathepsins S and K. It is important, therefore, to know whether similar differences exist between murine and human cathepsin B. Thus, both enzymes were expressed and biochemically characterized. The enzymes exhibited similar biochemical properties, indicating that cathepsin B transgenic mouse models could be useful for studying its role in human pathologies.

Up-regulation of cathepsin B expression and enhanced secretion in mitochondrial DNA-depleted osteosarcoma cells

BACKGROUND INFORMATION

mtDNA (mitochondrial DNA) mutations that impair oxidative phosphorylation can contribute to carcinogenesis through the increased production of reactive oxygen species and through the release of proteins involved in cell motility and invasion. On the other hand, many human cancers are associated with both the up-regulation and the increased secretion of several proteases and heparanase. In the present study, we tried to determine whether the depletion in mtDNA could modulate the expression and/or the secretion of some lysosomal hydrolases in the 143B osteosarcoma cells, as these mtDNA-depleted cells are characterized by a higher degree of invasiveness than the parental cells.

RESULTS

In comparison with the parental cells, we measured a higher amount of procathepsin B in the conditioned culture medium of the 143B cells lacking mtDNA (rho(0) 143B cells), as well as a rise in the specific activity of intracellular cathepsin B. In addition, we observed an activation of the transcription factor NF-kappaB (nuclear factor kappaB) in the cells devoid of functional mitochondria. Finally, we demonstrated that the down-regulation of the NF-kappaB p65 subunit by RNA interference led to a reduction in cathepsin B expression in rho(0) 143B cells.

CONCLUSIONS

The up-regulation of cathepsin B by NF-kappaB, followed by its secretion into the extracellular environment, might be partly responsible for the previously reported invasiveness of the mtDNA-depleted 143B osteosarcoma cells.

The BH3-only protein Bik/Blk/Nbk inhibits nuclear translocation of activated ERK1/2 to mediate IFNgamma-induced cell death

IFNγ induces cell death in epithelial cells, but the mediator for this death pathway has not been identified. In this study, we find that expression of Bik/Blk/Nbk is increased in human airway epithelial cells (AECs [HAECs]) in response to IFNγ. Expression of Bik but not mutant BikL61G induces and loss of Bik suppresses IFNγ-induced cell death in HAECs. IFNγ treatment and Bik expression increase cathepsin B and D messenger RNA levels and reduce levels of phospho–extracellular regulated kinase 1/2 (ERK1/2) in the nuclei of bik^+/+ compared with bik^−/− murine AECs. Bik but not BikL61G interacts with and suppresses nuclear translocation of phospho-ERK1/2, and suppression of ERK1/2 activation inhibits IFNγ- and Bik-induced cell death. Furthermore, after prolonged exposure to allergen, hyperplastic epithelial cells persist longer, and nuclear phospho-ERK is more prevalent in airways of IFNγ^−/− or bik^−/− compared with wild-type mice. These results demonstrate that IFNγ requires Bik to suppress nuclear localization of phospho-ERK1/2 to channel cell death in AECs.

Differences in the expression of cathepsin B in B16 melanoma metastatic variants depend on transcription factor Sp1

Cathepsin B contributes to the invasiveness of B16 melanoma cells in mice, with the highly metastatic B16a melanoma producing six- to eightfold more cathepsin B mRNA and protein than the less metastatic B16F1 variant. The proximal promoter region of the cathepsin B (Ctsb) gene (-149 to +94) was previously found to be capable of reproducing this pattern of differential gene activation in B16 melanoma variants. The binding of B16 melanoma nuclear proteins to this promoter region has now been mapped to three GC-boxes (Sp1 transcription factor binding sites) and a potential X-box [tax response element (TRE)/c-AMP responsive element (CRE) site]. Mutation of the GC-boxes at -55 and -37 independently decreased the expression of a luciferase reporter gene in B16a cells to the level observed in B16F1 cells. Promoter activity was also attenuated by mutations within the GC-rich segment between +6 and +16, but not by mutation of the putative X-box. Both Sp1 and Sp3 bound the GC-boxes in the Ctsb promoter, and western blotting showed the level of Sp1 to be greater in B16a compared to B16F1 cells. B16F1 cells that were made to express Sp1 at levels observed in B16a cells produced corresponding increased amounts of endogenous cathepsin B mRNA and enzyme activity. Thus, the difference in cathepsin B expression between high and low metastatic B16 melanoma variants is largely due to different levels of Sp1.

Functional interaction of E1AF and Sp1 in glioma invasion

Transcription factor E1AF is widely known to play critical roles in tumor metastasis via directly binding to the promoters of genes involved in tumor migration and invasion. Here, we report for the first time E1AF as a novel binding partner for ubiquitously expressed Sp1 transcription factor. E1AF forms a complex with Sp1, contributes to Sp1 phosphorylation and transcriptional activity, and functions as a mediator between epidermal growth factor and Sp1 phosphorylation and activity. Sp1 functions as a carrier bringing E1AF to the promoter region, thus activating transcription of glioma-related gene for beta1,4-galactosyltransferase V (GalT V; EC 2.4.1.38). Biologically, E1AF functions as a positive invasion regulator in glioma in cooperation with Sp1 partly via up-regulation of GalT V. This report describes a new mechanism of glioma invasion involving a cooperative effort between E1AF and Sp1 transcription factors.

Increased carcinogenic potential of myeloid tumor cells induced by aberrant TGF-beta1-signaling and upregulation of cathepsin B

The TGF-beta signaling pathways are implicated in cancer. Cysteine cathepsins can contribute to the carcinogenic potential of tumor cells. The aim of this study was to investigate the regulation of cysteine cathepsin expression by TGF-beta1 and the functional implications in tumor cells. We found an upregulation of cathepsin B (CathB, 2- to 5-fold) in different myeloid tumor cells (THP-1, MonoMac-1, MonoMac-6) after incubation with TGF-beta1. No upregulation was found in monocytes, and there was suppression of CathB expression in epithelial tumor cells (A549). Increased cathepsin B activity led to enhanced carcinogenic potential, which was reflected by increased migration and invasion of the cells and resistance to inhibitor-induced apoptosis. Analysis of the TGF-beta signaling pathways showed no alterations in TGF-beta/BMP receptor expression or SMAD2/3 phosphorylation, and no influence of MAP kinase pathways. However, a reduction in SMAD1 expression was detected. The lack of BMP action on cysteine cathepsin expression in myeloid tumor cells, but not in epithelial tumor cells, suggests a defect in the Smad1/Smad5 pathway. We located a related TGF-beta1-responsive element within the first intron of the CathB gene. In conclusion, alterations in the TGF-beta1 signaling pathway lead to upregulation of CathB, which contributes to the carcinogenic potential of tumor cells.

p53 and disease: when the guardian angel fails

The p53 tumor suppressor gene (TP53) is mutated more often in human cancers than any other gene yet reported. Of importance, it is mutated frequently in the common human malignancies of the breast and colorectum and also, but less frequently, in other significant human cancers such as glioblastomas. There is also one inherited cancer predisposing syndrome called Li-Fraumeni that is caused by TP53 mutations. In this review, we discuss the significance of p53 mutations in some of the above tumors with a view to outlining how p53 contributes to malignant progression. We also discuss the usefulness of TP53 status as a prognostic marker and its role as a predictor of response to therapy. Finally, we outline some evidence that abnormalities in p53 function contribute to the etiology of other non-neoplastic diseases.

Seven-up facilitates insect counter-defense by suppressing cathepsin B expression

When challenged by the dietary soybean cysteine protease inhibitor scN, the cowpea bruchid (Callosobruchus maculatus) adapts to the inhibitory effects by readjusting the transcriptome of its digestive system, including the specific activation of a cathepsin B-like cysteine protease CmCatB. To understand the transcriptional regulation of CmCatB, we cloned a portion of its promoter and demonstrated its activity in Drosophila cells using a chloramphenicol acetyltransferase reporter system. EMSAs detected differential DNA-binding activity between nuclear extracts of scN-adapted and -unadapted midguts. Two tandem chicken ovalbumin upstream promoter (COUP) elements were identified in the CmCatB promoter that specifically interacted with a protein factor unique to nuclear extracts of unadapted insect guts, where CmCatB expression was repressed. Seven-up (Svp) is a COUP-TF-related transcription factor that interacted with the COUP responsive element. Polyclonal anti-(mosquito Svp) serum abolished the specific DNA-binding activity in cowpea bruchid midgut extracts, suggesting that the protein factor is an Svp homolog. Subsequent cloning of a cowpea bruchid Svp (CmSvp) indicated that it shares a high degree of amino acid sequence similarity with COUP-TF/Svp orphan nuclear receptor family members from varied species. The protein was more abundant in scN-unadapted insect guts than scN-adapted guts, consistent with the observed DNA-binding activity. Furthermore, CmCatB expression was repressed when CmSvp was transiently expressed in Drosophila cells, most likely through COUP binding. These findings indicate that CmSvp may contribute to insect counter-defense, in part by inhibiting CmCatB expression under normal growth conditions, but releasing the inhibition when insects are challenged by dietary protease inhibitors.

Cysteine cathepsins: multifunctional enzymes in cancer

Cysteine cathepsins are highly upregulated in a wide variety of cancers by mechanisms ranging from gene amplification to post-transcriptional modification. Their localization within intracellular lysosomes often changes during neoplastic progression, resulting in secretion of both inactive and active forms and association with binding partners on the tumour cell surface. Secreted, cell-surface and intracellular cysteine cathepsins function in proteolytic pathways that increase neoplastic progression. Direct proof for causal roles in tumour growth, migration, invasion, angiogenesis and metastasis has been shown by downregulating or ablating the expression of individual cysteine cathepsins in tumour cells and in transgenic mouse models of human cancer.

Ethanol feeding alters death signaling in the pancreas

OBJECTIVES

Alcohol abuse is a major cause of pancreatitis, which is associated with death of parenchymal cells. The goal of this study was to explore the effects of ethanol on cell death pathways in the pancreas.

METHODS

Adult male Wistar rats were fed with ethanol diets using the Lieber-DeCarli method. Caspase-8, caspase-3, and cathepsin B expression and activity in the pancreas of these animals as well as the signals that regulate their expression were studied using Western blot analysis and specific assays for biochemical enzyme activity.

RESULTS

In the pancreas from rats fed with ethanol, the protein expression and activity of caspase-8 decreased by 48% and 45%, respectively, and caspase-3 activity decreased by 39%. In contrast, cathepsin B protein expression and activity increased with ethanol feeding by 189% and 143%, respectively. Evaluation of the transcriptional regulatory system for caspase-8 and cathepsin B showed that the ethanol effects on these pathways were largely transcriptional.

CONCLUSIONS

Our findings show effects of ethanol on the expression of several signals involved in cell death in the pancreas through alteration of transcriptional regulators. The decrease in caspase expression and increase in cathepsin B expression indicate that ethanol feeding may prevent apoptosis and promote necrosis of pancreatic tissue with stresses that cause pancreatitis.

Differential metastasis-associated gene analysis of prostate carcinoma cells derived from primary tumor and spontaneous lymphatic metastasis in nude mice with orthotopic implantation of PC-3M cells

The purpose of these studies was to explore the genes associated with invasion and metastasis of human prostatic carcinoma line PC-3M in nude mice. After PC-3M cells were inoculated in orthotopic site (prostate) in male nude mice for two months, tumor cells were isolated from primary tumor and lymph node metastasis in the same mouse, respectively. Cell invasion and adhesion ability in vitro were first compared between two cell lines. Then human metastasis-related genes differentially expressed between them were analyzed by utilizing cDNA microarray technique. The in vitro cell invasion and adhesion potential of tumor cells from lymph node metastasis was significantly higher than those from primary tumor, Metastasis-related genes differentially expressed between those two cell lines were identified, all of them were up-regulated in the tumor cells from lymph node metastasis and could be categorized as: (1) genes encoding cellular matrix-degrading proteolytic enzyme including cathepsin and MMP; (2) genes encoding transcription factors; (3) genes related to heterotypic adhesion of tumor cells; (4) genes encoding cell surface receptors. Moreover, Four genes were chosen for semi-quantitative RT-PCR analysis, they showed a consistent expression pattern with that of cDNA microarray analysis. We concluded that the lymph node metastasis in nude mice given an injection of PC-3M cells in the prostate is a selective process favoring the survival and growth of a special subpopulation derived from primary tumor with specific genetic alterations, which may play a pivotal role in the metastasis of prostate cancer. Identification and further characterization of these genes may allow a better understanding of lymphatic metastasis in prostate carcinoma.

Proteases and glioma angiogenesis

Angiogenesis, the process by which new branches sprout from existing vessels, requires the degradation of the vascular basement membrane and remodeling of the ECM in order to allow endothelial cells to migrate and invade into the surrounding tissues. Serine, metallo, and cysteine proteinases are 3 types of a family of enzymes that proteolytically degrade various components of extracellular matrix. These proteases release various growth factors and also increase adhesive molecules and signaling pathway molecules upon their activation, which plays a significant role in angiogenesis. Downregulation of these molecules by antisense/siRNA or synthetic inhibitors decreases the levels of these molecules, inhibits the release of growth factors, and decreases the levels of various signaling pathway molecules, thereby leading to the inhibition of angiogenesis. Furthermore, MMPs degrade specific substrates and release angiogenic inhibitors which inhibit angiogenesis. Downregulation of 2 molecules, such as uPA and uPAR, uPAR and MMP-9, or Cathepsin B and MMP-9, are more effective to inhibit angiogenesis rather than downregulation of single molecules. However, careful testing of these combinations are most important because multiple effects of these combinations play a significant role in angiogenesis.

Bone microenvironment modulates expression and activity of cathepsin B in prostate cancer

Prostate cancers metastasize to bone leading to osteolysis. Here we assessed proteolysis of DQ-collagen I (a bone matrix protein) and, for comparison, DQ-collagen IV, by living human prostate carcinoma cells in vitro. Both collagens were degraded, and this degradation was reduced by inhibitors of matrix metallo, serine, and cysteine proteases. Because secretion of the cysteine protease cathepsin B is increased in human breast fibroblasts grown on collagen I gels, we analyzed cathepsin B levels and secretion in prostate cells grown on collagen I gels. Levels and secretion were increased only in DU145 cells--cells that expressed the highest baseline levels of cathepsin B. Secretion of cathepsin B was also elevated in DU145 cells grown in vitro on human bone fragments. We further investigated the effect of the bone microenvironment on cathepsin B expression and activity in vivo in a SCID-human model of prostate bone metastasis. High levels of cathepsin B protein and activity were found in DU145, PC3, and LNCaP bone tumors, although the PC3 and LNCaP cells had exhibited low cathepsin B expression in vitro. Our results suggest that tumor-stromal interactions in the context of the bone microenvironment can modulate the expression of the cysteine protease cathepsin B.

The C-terminal subunit of artificially truncated human cathepsin B mediates its nuclear targeting and contributes to cell viability

BACKGROUND

Splicing variants of human cathepsinB primary transcripts (CB(-2,3)) result in an expression product product which lacks the signal peptide and parts of the propeptide. This naturally truncated Delta51CB is thus unable to follow the regular CB processing and sorting pathway. It is addressed to the mitochondria through an activated N-terminal mitochondrial targeting signal instead. Although Delta51CB is supposed to be devoid of the typical CB enzymatic activity, it might play a role in malignancies and trigger cell death/apoptosis independent from the function of the regular enzyme. Cytoplasmic presence of the mature CB might occur as a result of lysosomal damage.

RESULTS

We investigated such "aberrant" proteins by artificial CB-GFP chimeras covering various sequence parts in respect to their enzymatic activity, their localization in different cell types, and the effects on the cell viability. Unlike the entire full length CB form, the artificial single chain form was not processed and did not reveal typical enzymatic CB activity during transient overexpression in large cell lung carcinoma cells. Delta51CB was found predominantly in mitochondria. In contrast, the shorter artificial CB constructs localized in the cytoplasm, inside the cell nucleus, and in the midbodies of dividing cells. Bleaching experiments revealed both mobile and immobile fractions of these constructs in the nucleus. Nuclear accumulation of artificially truncated CB variants led to disintegration of nuclei, followed by cell death.

CONCLUSION

We propose that cell death associated with CB is not necessarily triggered by its regular enzymatic activity but alternatively by a yet unknown activity profile of truncated CB. Cytoplasmic CB might be able to enter the cell nucleus. According to a mutational analysis, the part of CB that mediates its nuclear import is a signal patch within its heavy chain domain. The results suggest that besides the N-terminal signal peptide also other CB domains contain patterns which are responsible for a differentiated targeting of the molecule, e.g. to the mitochondria, to the nucleus, or to vesicles. We propose a hierarchy of targeting signals depending on their strength and availability. This implies other possible transport mechanisms besides the usual trafficking via the mannose-6-sound recording copyright sign pathway.

Cathepsin B promotes both motility and invasiveness of oral carcinoma cells

We previously demonstrated that overexpression of cathepsin B (CB) protease in oral squamous cell carcinomas correlated positively with advanced tumor stage and poor histologic malignancy grade. Here we examined whether CB contributes to the invasiveness of oral carcinoma cells. For RNA-mediated inhibition, two ribozymes that target CB mRNA were designed and stably expressed in the oral squamous cell carcinoma cell line 1386Tu. Both ribozymes diminished expression of CB mRNA, protein, and activity, without affecting cathepsin D or beta-actin, as determined by quantitative real-time PCR, Western blots, and protease activity assays. Matrigel invasion assays showed that the invasiveness of the cells was significantly reduced by the expressed ribozymes and, surprisingly, the motilities of the ribozyme-transfected cells were also diminished. Our results document a direct role for CB in promoting oral cancer spread and invasion, and open the possibility of controlling oral carcinoma malignancy and metastasis by targeting CB with RNA inhibitor strategies.

Cost efficient and effective gene transfer into the human natural killer cell line, NK92

Introducing genes into cells is a crucial step in many fields of basic research, as well as for the development of new drugs and therapies. Many cell types are resistant to normal methods of gene delivery, such as lipid based transfection and electroporation. Delivery to resistant cell lines can be costly or inefficient. Natural killer (NK) cells are highly resistant to transfection. We have developed a novel method to deliver exogenous genes in the NK cell line, NK92. Using a combination of electroporation and a defined buffer, we were able to obtain an electroporation efficiency of 40% in NK92 cells. Using RNAi, we show significant reduction of an endogenous protein (ETS1) using this optimized buffer and electroporation conditions. Taken together, the results show a functional and cost effective method for the expression of exogenous genes in NK cells.

Sp3 proteins negatively regulate beta myosin heavy chain gene expression during skeletal muscle inactivity

In adult skeletal muscle, beta myosin heavy chain (betaMyHC) gene expression is primarily restricted to slow type I fibers; however, its expression is down-regulated in response to muscle inactivity. Little is known about the signaling pathways and transcription factors that mediate this important functional response. This study demonstrates that increased binding of Sp3 to GC-rich elements in the betaMyHC promoter is a critical event in down-regulation of betaMyHC gene expression under non-weight-bearing conditions. Conversely, binding of Sp3 to these elements decreased while Sp1 binding increased with nuclear extracts from plantaris muscle exposed to mechanical overload, a stimulus that increases betaMyHC gene expression. In addition, these experiments revealed the existence of an Sp4-DNA binding complex when using adult skeletal muscle nuclear extract was used but not when nuclear extracts from cultured myotubes were used. Sp3 proteins are competitive inhibitors of Sp1-mediated betaMyHC reporter gene transactivation in both Drosophila SL-2 and mouse C2C12 myotubes. Sp4 is a weak activator of betaMyHC gene expression in SL-2 cells, which lack endogenous Sp1 activity, but does not activate betaMyHC gene expression in C2C12 myotubes, which have high levels of Sp1. These results suggest that competitive binding of Sp family proteins regulate betaMyHC gene transcription in response to altered neuromuscular activity.

Transcription of cathepsin B in glioma cells: regulation by an E-box adjacent to the transcription initiation site

We have previously isolated the human cathepsin B promoter and shown that Sp1 and Ets factors are involved in the regulation of cathepsin B expression. Using mutagenesis, transient transfection and electrophoretic mobility shift assays (EMSAs), we further identified regulatory factors that mediate cathepsin B transcription in U87 human glioblastoma cells. An E-box element (CACGTG) adjacent to the transcription initiation site (at nucleotides -7 to -2) was found to be indispensable for cathepsin B promoter activity. Mutation of this E-box element in both pSCB2, a promoter construct with high promoter activity, and pSCB6, a construct with basal promoter activity, led to a 90% decrease in promoter activity in U87 cells. EMSAs demonstrated that upstream stimulatory factor 1 (USF-1) and upstream stimulatory factor 2 (USF-2) bound to the E-box as a heterodimer. Chromatin immunoprecipitation assays revealed that both USF-1 and USF-2 were associated with the cathepsin B promoter. The roles of USF-1 and USF-2 in the regulation of cathepsin B expression were demonstrated by (i) co-transfection experiments showing that USF-1 or USF-2 increased promoter activity by 2.5-fold individually and by 3.4-fold together; (ii) co-transfection of pSCB6 with pUSF-2deltaN (a dominant negative USF-2 expression plasmid) resulting in an 80% decrease in promoter activity; and (iii) mutation of the E-box element (from 5'-CACGTG to 5'-CGCGTT in the pSCB6 basal promoter construct) abolishing transactivation of cathepsin B by USF-1 and USF-2. These results collectively indicate that an E-box at nucleotides -7 to -2 of the cathepsin B promoter is critical to the expression of cathepsin B and that binding of USF-1 and USF-2 to this E-box can regulate cathepsin B promoter activity.

Isolation of a novel USF2 isoform: repressor of cathepsin B expression

We previously demonstrated that upstream stimulatory factor 1 (USF1) and USF2 regulate transcription of cathepsin B. Here, we have cloned a novel transcript variant of USF2 from a human DU145 prostate cancer cell line by reverse transcription-polymerase chain reaction (RT-PCR). This new transcript variant, designated USF2c, results from alternative splicing of the primary USF2 transcript using a cryptic splicing acceptor site within exon 6. As a consequence, USF2c is missing exons 4, 5, and part of exon 6. USF2c can be transcribed and translated to a protein of approximately 29 kDa in vitro, and the resulting USF2c protein can bind as a homodimer to the E-box of the cathepsin B promoter. USF2c is expressed in two other prostate cancer cell lines (LNCaP, PC3), and U87 human glioblastoma cells as are USF2a and USF2b, two previously identified isoforms of USF2. Cotransfection experiments in DU145 and U87 cells demonstrate that USF2c can down-regulate expression of cathepsin B. These results suggest that USF2c regulates expression of cathepsin B by binding to the E box element in the cathepsin B promoter as a repressor.

Cathepsin B mRNA and protein expression following contusion spinal cord injury in rats

We provide the first data that cathepsin B (Cath B), a lysosomal cysteine protease, is up-regulated following contusion-spinal cord injury (SCI). Following T12 laminectomy and moderate contusion, Cath B mRNA and protein expression profiles were examined from 2 to 168 h post-injury in rats using real-time PCR and immunoblots, respectively. Contusion injury significantly increased [mRNA]Cath B in the injury site and adjacent segments over sham injury levels. While the largest [mRNA]Cath B induction (20-fold over naive) was seen in the injury site, the caudal segment routinely yielded [mRNA]Cath B levels greater than 10-fold over naive. Interestingly, sham injury animals also experienced mRNA induction at several time points at the injury site and in segments rostral and caudal to the injury site. Contusion injury also significantly elevated levels of Cath B proenzyme protein (37 kDa) over sham injury in the injury site (48, 72 and 168 h post-injury). Furthermore, significant protein increases of single and double chain Cath B (both active forms) occurred at the injury site at 72 and 168 h post-injury. Similar significant increases in Cath B protein levels were seen in areas adjacent to the injury site. The induction of Cath B mRNA and protein expression following contusion injury is previously undescribed and suggests that Cath B may potentially be involved in the secondary injury cascade, perhaps for as long as 1 week post-injury.

Transcription of human cathepsin L mRNA species hCATL B from a novel alternative promoter in the first intron of its gene

Cathepsin L is a lysosomal cysteine protease over-expressed in malignancy. It is very potent in degrading collagen, elastin, laminin and other components of the basement membrane and therefore, has been implicated in tumor invasion and metastasis. Two mRNA species, hCATL A and hCATL B, which contain an identical open reading frame and different 5'UTRs, were demonstrated to be encoded by the same gene located on chromosome 9q21-22. We have previously cloned and characterized the promoter responsible for the transcription of hCATL A (hCATL A promoter). However, it was not clear whether hCATL B is a splice variant of hCATL A or transcribed from a different promoter. In the present study, we demonstrate for the first time that hCATL B is transcribed from an alternate promoter (hCATL B promoter) located in the first intron of hCATL. This TATA-less promoter initiates transcription from two cytosine nucleotides present 191 and 367 bases upstream to the translation start codon. Deletion analysis revealed that the core promoter region lies upstream to these transcription initiation sites. This region contains several putative transcription factor-binding sites like AP-1, AP-4, GATA-1, Lmo2, NF-kappa B, MZF-1, NF-AT, etc. In U-87 MG cells, hCATL B promoter exhibits at least six times less activity than our previously characterized hCATL A promoter. However, this promoter is significantly more active in malignantly transformed cells as compared to its activity in untransformed cells. Thus, our results conclusively demonstrate that hCATL B mRNA is transcribed from an alternate promoter. Increased transcriptional activity from this promoter contributes to the elevated cathepsin L expression in transformed cells.

Molecular mechanisms of glioma invasiveness: the role of proteases

The invasive nature of brain-tumour cells makes an important contribution to the ineffectiveness of current treatment modalities, as the remaining tumour cells inevitably infiltrate the surrounding normal brain tissue, which leads to tumour recurrence. Such local invasion remains an important cause of mortality and underscores the need to understand in more detail the mechanisms of tumour invasiveness. Several proteases influence the malignant characteristics of gliomas--could their inhibition prove to be a useful therapeutic strategy?

Exploring the role of 5' alternative splicing and of the 3'-untranslated region of cathepsin B mRNA

The cysteine peptidase cathepsin B is responsible for connective tissue breakdown in several diseases. The pathological expression of cathepsin B may depend on the structure of its mRNA. We investigated the translational efficiency of the cathepsin B mRNA untranslated regions (UTRs) using fusion constructs to green fluorescent protein (GFP) and luciferase. Transfection of fusion constructs with GFP and luciferase containing the full-length 5'-UTR, the variant lacking exon 2, and that lacking exons 2 and 3 into mammalian cells, resulted in modulation of the biosynthetic rate of cathepsin B in a cell-specific manner. Constructs missing these exons were biosynthetically more efficient than the full-length counterpart. Luciferase was cloned upstream of the 3'-UTR, downstream of the 5'-UTR, or sandwiched between the 5'- and the 3'-UTR. The UTRs of cathepsin B downregulated luciferase biosynthesis moderately when present individually, with the 3'-UTR being more efficient than the 5'-UTR, and downregulated it even more when present simultaneously. A truncated cathepsin B-GFP chimeric product derived from the 5'-UTR missing exons 2 and 3 induced cell death. The increased biosynthetic rate and abnormal trafficking of cathepsin B observed in pathologies such as cancer and osteoarthritis may depend on alternative splicing of pre-mRNA.

Molecular regulation of human cathepsin B: implication in pathologies

Cathepsin B is a papain-family cysteine protease that is normally located in lysosomes, where it is involved in the turnover of proteins and plays various roles in maintaining the normal metabolism of cells. This protease has been implicated in pathological conditions, e.g., tumor progression and arthritis. In disease conditions, increases in the expression of cathepsin B occur at both the gene and protein levels. At the gene level, the altered expression results from gene amplification, elevated transcription, use of alternative promoters and alternative splicing. These molecular changes lead to increased cathepsin B protein levels and in turn redistribution, secretion and increased activity. Here we focus on the molecular regulation of cathepsin B and attendant implications for tumor progression and arthritis. The potential of cathepsin B as a therapeutic target is also discussed.