Cathepsin L antisense oligonucleotides in a human osteosarcoma cell line: effects on the invasive phenotype

Cathepsin L promotes oesophageal squamous cell carcinoma development and may be associated with tumour-associated macrophages

Background

Oesophageal squamous cell carcinoma (ESCC) is a leading cause of cancer-related deaths worldwide because existing treatments are often insufficient. Therefore, new, reliable biomarkers must be identified. CTSL overexpression is closely associated with tumour progression and poor prognosis. However, the role and mechanism of CTSL as an oncogene in ESCC remain unclear.

Methods

Genome-wide association study (GWAS) data were used for Mendelian randomization analysis to investigate the possible relationships between CTSL and ESCC. The correlation between CTSL expression and prognosis was analysed using GEO, TCGA, and GEPIA data. We compared CTSL expression among the cell types using single-cell sequencing. Correlations between CTSL and the tumour microenvironment, immune cell infiltration, tumour mutational load, immunological checkpoints, and treatment sensitivity in patients with ESCC were investigated. Finally, using mouse models and cellular investigations, we assessed the effects of CTSL on the growth, apoptosis, and metastasis of ESCC tumour cells.

Results

CTSL was overexpressed in ESCC and correlated with prognosis. We also discovered its close association with cell immunity, especially with tumour-associated macrophages and immune checkpoints in the tumour microenvironment. CTSL may play a key role in ESCC development by affecting M2 macrophage polarisation. CTSL and the M2 macrophage marker genes showed significant positive correlations. Mendelian randomization analysis confirmed a relationship between CTSL and ESCC. Finally, our in vitro and in vivo experiments demonstrated that CTSL promoted the proliferation and migration of ESCC cells, validating our bioinformatic analysis.

Conclusion

CTSL emerged as a crucial gene in ESCC that influences patient prognosis and immunity, particularly in association with M2 macrophages. Therefore, targeting or modulating CTSL levels may provide new therapeutic strategies for patients with ESCC.

Large-scale whole exome sequencing studies identify two genes,CTSL and APOE, associated with lung cancer

Common genetic variants associated with lung cancer have been well studied in the past decade. However, only 12.3% heritability has been explained by these variants. In this study, we investigate the contribution of rare variants (RVs) (minor allele frequency <0.01) to lung cancer through two large whole exome sequencing case-control studies. We first performed gene-based association tests using a novel Bayes Factor statistic in the International Lung Cancer Consortium, the discovery study (European, 1042 cases vs. 881 controls). The top genes identified are further assessed in the UK Biobank (European, 630 cases vs. 172 864 controls), the replication study. After controlling for the false discovery rate, we found two genes, CTSL and APOE, significantly associated with lung cancer in both studies. Single variant tests in UK Biobank identified 4 RVs (3 missense variants) in CTSL and 2 RVs (1 missense variant) in APOE stongly associated with lung cancer (OR between 2.0 and 139.0). The role of these genetic variants in the regulation of CTSL or APOE expression remains unclear. If such a role is established, this could have important therapeutic implications for lung cancer patients.

Identification of Factors Driving Doxorubicin-Resistant Ewing Tumor Cells to Survival

BACKGROUND

Ewing sarcoma (ES) cells exhibit extreme plasticity that contributes to the cell's survival and recurrence. Although multiple studies reveal various signaling pathways mediated by the EWSR1/FLI1 fusion, the specific transcriptional control of tumor cell resistance to doxorubicin is unknown. Understanding the molecular hubs that contribute to this behavior provides a new perspective on valuable therapeutic options against tumor cells.

METHODS

Single-cell RNA sequencing and LC-MS/MS-based quantitative proteomics were used.

RESULTS

A goal of this study was to identify protein hubs that would help elucidate tumor resistance which prompted ES to relapse or metastasize. Several differentially expressed genes and proteins, including adhesion, cytoskeletal, and signaling molecules, were observed between embryonic fibroblasts and control and doxorubicin-treated tumor cell lines. While several cancer-associated genes/proteins exhibited similar expression across fibroblasts and non-treated cells, upregulation of some proteins belonging to metabolic, stress response, and growth pathway activation was uniquely observed in doxorubicin-treated sarcoma cells, respectively. The novel information on differentially expressed genes/proteins provides insights into the biology of ES cells, which could help elucidate mechanisms of their recurrence.

CONCLUSIONS

Collectively, our results identify a novel role of cellular proteins in contributing to tumor cell resistance and escape from doxorubicin therapy and contributing to ES progression.

An efficient and concise synthesis of a selective small molecule non-peptide inhibitor of cathepsin L: KGP94

KGP94 is a potent, selective, and competitive inhibitor of the lysosomal endopeptidase enzyme (Cathepsin L) currently in preclinical trials for the treatment of metastatic cancer, which is a leading cause of cancer-associated death. Herein, we report two new synthetic routes for synthesizing the target compound through four consecutive steps, using a Weinreb amide approach starting from a common 3-bromobenzoyl chloride. A key step in the approach is a coupling reaction of a readily available Grignard reagent with amide 4 to produce 6, a previously unreported coupling pattern. These new strategies offer an efficient and alternative approach to synthesis of target compound with an excellent overall yield.

CTLA-2 Alpha Is a Potent Inhibitor of Angiogenesis in Murine Ocular Tissue

Cytotoxic T lymphocyte antigen-2 (CTLA-2) alpha has been reported to suppress the activities of cathepsin L (Cath L), which is deeply involved in angiogenesis. Therefore, we assessed whether CTLA-2 alpha plays a role in angiogenesis in ocular tissue. To establish models of corneal inflammation and experimental choroidal neovascularization (CNV), male C57BL/6J mice (n = 5) underwent corneal suture placement or laser-induced CNV, respectively. Mice were then injected with recombinant CTLA-2 alpha (1 µg) into the peritoneal cavity at day 0 and every 2 days after operation. In vitro experiments were performed to assess the inflammatory response by measuring TNF-alpha secretion in peritoneal cavity exudate cells (PECs) or the proliferation of mouse vascular endothelial cells (mVECs). CTLA-2 alpha treatment dramatically suppressed corneal angiogenesis, as well as laser-induced CNV. Moreover, CTLA-2 alpha inhibited the proliferation of mVECs in vitro, while CTLA-2 alpha abolishment was able to rescue proliferation. However, CTLA-2 alpha could not suppress cytokine secretion from inflammatory cells such as PECs. In summary, CTLA-2 alpha was able to suppress angiogenesis by suppressing endothelial cell proliferation. Further studies are needed to investigate its usefulness as a new antiangiogenic treatment for a variety of conditions, including age-related macular degeneration.

CDH4 is a novel determinant of osteosarcoma tumorigenesis and metastasis

The era of cancer genomics now provides an opportunity to discover novel determinants of osteosarcoma (OS), the most common primary bone cancer in children and adolescents known for its poor prognosis due to lung metastasis. Here, we identify CDH4 amplification in 43.6% of human osteosarcoma using array CGH and demonstrate its critical role in osteosarcoma development and progression. Gain or loss-of-function of CDH4, which encodes R-cadherin, causally impacts multiple features of human OS cells including cell migration and invasion, osteogenic differentiation, and stemness. CDH4 overexpression activates c-Jun via the JNK pathway, while CDH4 knockdown suppresses both tumor xenograft growth and lung colonization. In OS patient specimens, high CDH4 expression associates with lung metastases and poor prognosis. Collectively, our bioinformatics, functional, molecular, and clinical analyses uncover an oncogenic function of CDH4 in osteosarcoma and its relationship with patient outcome.

Cystatin C deficiency suppresses tumor growth in a breast cancer model through decreased proliferation of tumor cells

Cysteine cathepsins are proteases that, in addition to their important physiological functions, have been associated with multiple pathologies, including cancer. Cystatin C (CstC) is a major endogenous inhibitor that regulates the extracellular activity of cysteine cathepsins. We investigated the role of cystatin C in mammary cancer using CstC knockout mice and a mouse model of breast cancer induced by expression of the polyoma middle T oncoprotein (PyMT) in the mammary epithelium. We showed that the ablation of CstC reduced the rate of mammary tumor growth. Notably, a decrease in the proliferation of CstC knockout PyMT tumor cells was demonstrated ex vivo and in vitro, indicating a role for this protease inhibitor in signaling pathways that control cell proliferation. An increase in phosphorylated p-38 was observed in CstC knockout tumors, suggesting a novel function for cystatin C in cancer development, independent of the TGF-β pathway. Moreover, proteomic analysis of the CstC wild-type and knockout PyMT primary cell secretomes revealed a decrease in the levels of 14-3-3 proteins in the secretome of knock-out cells, suggesting a novel link between cysteine cathepsins, cystatin C and 14-3-3 proteins in tumorigenesis, calling for further investigations.

Cathepsin L targeting in cancer treatment

Proteolytic enzymes may serve as promising targets for novel therapeutic treatment strategies seeking to impede cancer progression and metastasis. One such enzyme is cathepsin L (CTSL), a lysosomal cysteine protease. CTSL upregulation, a common occurrence in a variety of human cancers, has been widely correlated with metastatic aggressiveness and poor patient prognosis. In addition, CTSL has been implicated to contribute to cancer-associated osteolysis, a debilitating morbidity affecting both life expectancy and the quality of life. In this review, we highlight the mechanisms by which CTSL contributes to tumor progression and dissemination and discuss the therapeutic utility of CTSL intervention strategies aimed at impeding metastatic progression and bone resorption.

Downregulation of cathepsin L suppresses cancer invasion and migration by inhibiting transforming growth factor‑β‑mediated epithelial‑mesenchymal transition

Cathepsin L, a lysosomal acid cysteine protease, was found to be overexpressed in several types of human carcinomas. However, its functional roles in tumor progression and the underlying mechanisms remain largely unclear. In the present study, we investigated a novel functional aspect of cathepsin L in regulating transforming growth factor‑β (TGF‑β)‑induced epithelial‑mesenchymal transition (EMT) in A549 and MCF‑7 cells and examined its possible mechanisms. We found that TGF‑β‑induced cell morphologic changes of EMT were associated with the increased protein level of cathepsin L in A549 and MCF‑7 cells, suggesting that cathepsin L may be involved in the regulation of EMT. Furthermore, we showed that silencing of cathepsin L blocked TGF‑β‑induced cell migration, invasion and actin remodeling and inhibited TGF‑β‑mediated EMT. We also demonstrated that the mechanism of how cathepsin L knockdown regulates EMT may be explained by the suppression of EMT‑inducing molecules, such as Snail, which is associated with the phosphatidylinositol 3‑kinase (PI3K)‑AKT and Wnt signaling pathways. Moreover, we proved that cathepsin L knockdown in A549 cells significantly inhibited xenograft tumor growth and EMT in vivo. The results showed a new mechanism to determine cathepsin L involvement in the regulation of cancer invasion and migration. These results showed that cathepsin L knockdown is important in regulating EMT and suggest that cathepsin L may be utilized as a new target for enhancing the efficacy of chemotherapeutics against epithelial cancer.

Acquired resistance to metformin in breast cancer cells triggers transcriptome reprogramming toward a degradome-related metastatic stem-like profile

Therapeutic interventions based on metabolic inhibitor-based therapies are expected to be less prone to acquired resistance. However, there has not been any study assessing the possibility that the targeting of the tumor cell metabolism may result in unforeseeable resistance. We recently established a pre-clinical model of estrogen-dependent MCF-7 breast cancer cells that were chronically adapted to grow (> 10 months) in the presence of graded, millimolar concentrations of the anti-diabetic biguanide metformin, an AMPK agonist/mTOR inhibitor that has been evaluated in multiple in vitro and in vivo cancer studies and is now being tested in clinical trials. To assess what impact the phenomenon of resistance might have on the metformin-like "dirty" drugs that are able to simultaneously hit several metabolic pathways, we employed the ingenuity pathway analysis (IPA) software to functionally interpret the data from Agilent whole-human genome arrays in the context of biological processes, networks, and pathways. Our findings establish, for the first time, that a "global" targeting of metabolic reprogramming using metformin certainly imposes a great selective pressure for the emergence of new breast cancer cellular states. Intriguingly, acquired resistance to metformin appears to trigger a transcriptome reprogramming toward a metastatic stem-like profile, as many genes encoding the components of the degradome (KLK11, CTSF, FREM1, BACE-2, CASP, TMPRSS4, MMP16, HTRA1), cancer cell migration and invasion factors (TP63, WISP2, GAS3, DKK1, BCAR3, PABPC1, MUC1, SPARCL1, SEMA3B, SEMA6A), stem cell markers (DCLK1, FAK), and key pro-metastatic lipases (MAGL and Cpla2) were included in the signature. Because this convergent activation of pathways underlying tumor microenvironment interactions occurred in low-proliferative cancer cells exhibiting a notable downregulation of the G 2/M DNA damage checkpoint regulators that maintain genome stability (CCNB1, CCNB2, CDC20, CDC25C, AURKA, AURKB, BUB1, CENP-A, CENP-M) and pro-autophagic features (i.e., TRAIL upregulation and BCL-2 downregulation), it appears that the unique mechanism of acquired resistance to metformin has opposing roles in growth and metastatic dissemination. While refractoriness to metformin limits breast cancer cell growth, likely due to aberrant mitotic/cytokinetic machinery and accelerated autophagy, it notably increases the potential of metastatic dissemination by amplifying the number of pro-migratory and stemness inputs via the activation of a significant number of proteases and EMT regulators. Future studies should elucidate whether our findings using supra-physiological concentrations of metformin mechanistically mimic the ultimate processes that could paradoxically occur in a polyploid, senescent-autophagic scenario triggered by the chronic metabolic stresses that occur during cancer development and after treatment with cancer drugs.

Cysteine cathepsins: from structure, function and regulation to new frontiers

It is more than 50 years since the lysosome was discovered. Since then its hydrolytic machinery, including proteases and other hydrolases, has been fairly well identified and characterized. Among these are the cysteine cathepsins, members of the family of papain-like cysteine proteases. They have unique reactive-site properties and an uneven tissue-specific expression pattern. In living organisms their activity is a delicate balance of expression, targeting, zymogen activation, inhibition by protein inhibitors and degradation. The specificity of their substrate binding sites, small-molecule inhibitor repertoire and crystal structures are providing new tools for research and development. Their unique reactive-site properties have made it possible to confine the targets simply by the use of appropriate reactive groups. The epoxysuccinyls still dominate the field, but now nitriles seem to be the most appropriate “warhead”. The view of cysteine cathepsins as lysosomal proteases is changing as there is now clear evidence of their localization in other cellular compartments. Besides being involved in protein turnover, they build an important part of the endosomal antigen presentation. Together with the growing number of non-endosomal roles of cysteine cathepsins is growing also the knowledge of their involvement in diseases such as cancer and rheumatoid arthritis, among others. Finally, cysteine cathepsins are important regulators and signaling molecules of an unimaginable number of biological processes. The current challenge is to identify their endogenous substrates, in order to gain an insight into the mechanisms of substrate degradation and processing. In this review, some of the remarkable advances that have taken place in the past decade are presented. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.

INSL3 has tumor-promoting activity in thyroid cancer

The functional role of INSL3 and its receptor RXFP2 in carcinogenesis is largely unknown. We have previously demonstrated (pro-)cathepsin-L as a target of INSL3 in human thyroid cancer cells facilitating penetration of tumor cells through elastin matrices. We demonstrate the expression of RXFP2 in human thyroid tissues and in mouse follicular thyroid epithelial cells using Cre-recombinase transgene driven by Rxfp2 promoter. Recombinant and secreted INSL3 increased the motility of thyroid carcinoma (TC) cells in an autocrine/paracrine manner. This effect required the presence of RXFP2. We identified S100A4 as a novel INSL3 target molecule and showed that S100A4 facilitated INSL3-induced enhanced motility. Stable transfectants of the human follicular TC cell line FTC-133 expressing and secreting bioactive human INSL3 displayed enhanced anchorage-independent growth in soft agar assays. Xenotransplant experiments in nude mice showed that INSL3, but not EGFP-mock transfectants, developed fast-growing and highly vascularized xenografts. We used human umbilical vein endothelial cells in capillary tube formation assays to demonstrate increased 2-dimensional tube formations induced by recombinant human INSL3 and human S100A4 comparable to the effect of vascular endothelial growth factor used as positive control. We conclude that INSL3 is a powerful and multifunctional promoter of tumor growth and angiogenesis in human thyroid cancer cell xenografts. INSL3 actions involve RXFP2 activation and the secretion of S100A4 and (pro-)cathepsin-L.

Cathepsin L increased level upon Ras mutants expression: the role of p38 and p44/42 MAPK signaling pathways

The involvement of Ras and three major Ras effectors, Raf, phosphatidylinositol 3-kinase (PI3K) and Ral guanine nucleotide exchange factor in the regulation of lysosomal proteases cathepsin L and B in human fibroblasts was compared. We found that cathepsin L cell content was increased by active Ras overexpression through Raf- and PI3K-mediated signaling pathways, while cathepsin B processing was altered by active Ras overexpression. Cathepsin L increased level following active Ras overexpression correlates with an increase of p38 MAPK activation and content and with an increase of p44/42 MAPK activation, so we investigated the role of these signaling pathways using pharmacological inhibitors. Unexpectedly, the p38 MAPK inhibitor SB203580 produced an increase of cathepsin L content, while the p44/42 MAPK signaling cascade inhibitor U0126 produced a remarkable shift of cathepsin L processing in favor of procathepsin L. In both cases, cathepsin B level and processing were not affected. The analysis of CTSL1 gene transcript demonstrated that cathepsin L protein and transcript correlate both in fibroblasts expressing Ras mutants and in pharmacologically treated cells, thus indicating a transcriptional up-regulation.

Cathepsin L in metastatic bone disease: therapeutic implications

Cathepsin L is a lysosomal cysteine proteinase primarily devoted to the metabolic turnover of intracellular proteins. However, accumulating evidence suggests that this endopeptidase might also be implicated in the regulation of other important biological functions, including bone resorption in normal and pathological conditions. These findings support the concept that cathepsin L, in concert with other proteolytic enzymes involved in bone remodeling processes, could contribute to facilitate bone metastasis formation. In support of this hypothesis, recent studies indicate that cathepsin L can foster this process by triggering multiple mechanisms which, in part, differ from those of the major cysteine proteinase of osteoclasts, namely cathepsin K. Therefore, cathepsin L can be regarded as an additional target in the treatment of patients with metastatic bone disease. This review discusses the clinical and therapeutic implications related to these findings.

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

BACKGROUND

Protein C inhibitor (PCI) is a plasma serine protease inhibitor (serpin) that regulates several serine proteases in coagulation including thrombin and activated protein C. However, the physiological role of PCI remains under investigation. The cysteine protease, cathepsin L, has a role in many physiological processes including cardiovascular diseases, blood vessel remodeling, and cancer.

METHODS AND RESULTS

We found that PCI inhibits cathepsin L with an inhibition rate (k(2)) of 3.0x10(5)M(-)(1)s(-)(1). Whereas, the PCI P1 mutant (R354A) inhibits cathepsin L at rates similar to wild-type PCI, mutating the P2 residue results in a slight decrease in the rate of inhibition. We then assessed the effect of PCI and cathepsin L on the migration of human breast cancer (MDA-MB-231) cells. Cathepsin L was expressed in both the cell lysates and conditioned media of MDA-MB-231 cells. Wound-induced and transwell migration of MDA-MB-231 cells was inhibited by exogenously administered wtPCI and PCI P1 but not PCI P14 mutant. In addition, migration of MDA-MB-231 cells expressing wtPCI was significantly decreased compared to non-expressing MDA-MB-231 cells or MDA-MB-231 cells expressing the PCI P14 mutant. Downregulation of cathepsin L by either a specific cathepsin L inhibitor or siRNA technology also resulted in a decrease in the migration of MDA-MB-231 cells.

CONCLUSIONS

Overall, our data show that PCI regulates tumor cell migration partly by inhibiting cathepsin L.

GENERAL SIGNIFICANCE

Consequently, inhibiting cathepsin L by serpins like PCI may be a new pathway of regulating hemostasis, cardiovascular and metastatic diseases.

Cysteine protease-mediated cytoskeleton interactions with LFA-1 promote T-cell morphological changes

T cells migrate through restrictive barriers in a protease-independent, amoeboid fashion that is characterized by morphological cell polarization. The interaction of cysteine-dependent carboxypeptidase cathepsin X with beta(2) integrin LFA-1 (lymphocyte function associated antigen 1) induces T-cell morphological changes, displaying into a 3D extracellular matrix a cytoplasmic projection termed a uropod. In the present study we show that inhibition of cathepsin X and a cysteine-dependent endopeptidase, cathepsin L, markedly inhibits T-cell actin polymerization, shape polarization, and chemotaxis. We propose that cathepsin L promotes T-cell migration associated processes by activating procathepsin X in the endolysosomal vesicles near the cell membrane and at the peak of the uropod, where both proteases were colocalized. We show that active cathepsin X modifies the beta(2) cytoplasmic tail of LFA-1 in the uropod, promoting its high affinity conformation. We suggest that LFA-1 cleavage contributes to the conformational change in the cytoplasmic tail, promoting the binding of the cytoskeletal protein talin. This interaction is restricted to the uropod and results in the stabilization of this region, promoting LFA-1-mediated cell uropod elongation.

Molecular cloning of cDNA for SPase, a monkey cathepsin L orthologue

SPase is a cysteine protease isolated from an African green monkey kidney cell line, CV-1, and has selective cleavage activity toward transcription factor SP-1 and retinoblastoma susceptibility gene product RB. In this study, a cDNA encoding SPase was cloned from a cDNA library prepared from CV-1 cells. The cDNA clone encodes 333 amino acids and is 96.5% identical to human cathepsin L at the nucleotide and amino acid sequence levels. SPase appears to be translated as a preproenzyme based on the comparison between the deduced amino acid sequence and the N-terminal sequence of the purified enzyme. Northern blot analysis exhibited the considerably higher expression of SPase in CV-1 cells compared with COS-1 cells, showing a good correlation with enzymatic activity in these cell lines. Bacterially expressed SPase protein exhibited proteolytic activity toward SP-1 and RB proteins. These observations suggest that SPase is a monkey cathepsin L orthologue.

Frequent loss of cystatin E/M expression implicated in the progression of prostate cancer

Cystatin E/M (CST6) is a natural inhibitor of lysosomal cysteine proteases. Recent studies have shown that experimental manipulation of CST6 expression alters the metastatic behavior of human breast cancer cells. However, the association of CST6 with prostate cancer invasion and progression remains unclear. Here, we show that CST6 is robustly expressed in normal human prostate epithelium, whereas its expression is downregulated in metastatic prostate cell lines and prostate tumor tissues. Treatment of metastatic prostate cell lines with the histone deacetylase inhibitor trichostatin A resulted in significant induction of CST6 mRNA levels and increased CST6 protein expression, indicating that epigenetic silencing may play a role in the loss of CST6 expression observed in prostate cancer. CST6 overexpression in human prostate cancer cells significantly reduced in vitro cell proliferation and matrigel invasion. Furthermore, the results from a bioluminescence tumor/metastasis model showed that the overexpression of CST6 significantly inhibits tumor growth and the incidence of lung metastasis. These results suggest that the downregulation of the CST6 gene is associated with promoter histone modifications and that this association plays an important role in prostate cancer progression during the invasive and metastatic stages of the disease.

The cytoplasmic domain of proEGF negatively regulates motility and elastinolytic activity in thyroid carcinoma cells

The intracellular domains of the membrane-anchoring regions of some precursors of epidermal growth factor (EGF) family members have intrinsic biologic activities. We have determined the role of the human proEGF cytoplasmic domain (proEGFcyt) as part of the proEGF transmembrane-anchored region (proEGFctF) in the regulation of motility and elastinolytic invasion in human thyroid cancer cells. We found proEGFctF to act as a negative regulator of motility and elastin matrix penetration and the presence of proEGFcyt or proEGF22.23 resulted in a similar reduction in motility and elastinolytic migration. This activity was counteracted by EGF-induced activation of EGF receptor signaling. Decreased elastinolytic migratory activity in the presence of proEGFctF and proEGFcyt/proEGF22.23 coincided with decreased secretion of elastinolytic procathepsin L. The presence of proEGFctF and proEGFcyt/proEGF22.23 coincided with the specific transcriptional up-regulation of t-SNARE member SNAP25. Treatment with siRNA-SNAP25 resulted in motility and elastin migration being restored to normal levels. Epidermal growth factor treatment down-regulated SNAP25 protein by activating EGF receptor-mediated proteasomal degradation of SNAP25. These data provide first evidence for an important function of the cytoplasmic domain of the human proEGF transmembrane region as a novel suppressor of motility and cathepsin L-mediated elastinolytic invasion in human thyroid carcinoma cells and suggest important clinical implications for EGF-expressing tumors.

Thymoquinone reduces mouse colon tumor cell invasion and inhibits tumor growth in murine colon cancer models

We have shown that thymoquinone (TQ) is a potent antitumor agent in human colorectal cancer cells. In this study, we evaluated TQ's therapeutic potential in two different mice colon cancer models [1,2-dimethyl hydrazine (DMH) and xenografts]. We also examined TQ effects on the growth of C26 mouse colorectal carcinoma spheroids and assessed tumor invasion in vitro. Mice were treated with saline, TQ, DMH, or combinations once per week for 30 weeks and the multiplicity, size and distribution of aberrant crypt foci (ACF) and tumors were determined at weeks 10, 20 and 30. TQ injected intraperitoneally (i.p.) significantly reduced the numbers and sizes of ACF at week 10; ACF numbers were reduced by 86%. Tumor multiplicity was reduced at week 20 from 17.8 in the DMH group to 4.2 in mice injected with TQ. This suppression was observed at week 30 and was long-term; tumors did not re-grow even when TQ injection was discontinued for 10 weeks. In a xenograft model of HCT116 colon cancer cells, TQ significantly (P < 0.05) delayed the growth of the tumor cells. Using a matrigel artificial basement membrane invasion assay, we demonstrated that sub-cyto-toxic doses of TQ (40μM) decreased C26 cell invasion by 50% and suppressed growth in three-dimensional spheroids. Apoptotic signs seen morphologically were increased significantly in TQ-treated spheroids. TUNEL staining of xenografts and immunostaining for caspase 3 cleavage in DMH tumors confirmed increased apoptosis in mouse tumors in response to TQ. These data should encourage further in vivo testing and support the potential use of TQ as a therapeutic agent in human colorectal cancer.

Loss of responsiveness to IGF-I in cells with reduced cathepsin L expression levels

The lysosomal cysteine proteinase cathepsin L is involved in proteolytic processing of internalized proteins. In transformed cells, where it is frequently overexpressed, its intracellular localization and functions can be altered. Previously, we reported that treatment of highly metastatic, murine carcinoma H-59 cells with small molecule cysteine proteinase inhibitors altered the responsiveness of the type I insulin-like growth factor (IGF-I) receptor and consequently reduced cell invasion and metastasis. To assess more specifically the role of cathepsin L in IGF-I-induced signaling and tumorigenicity, we generated H-59 subclones with reduced cathepsin L expression levels. These clonal lines showed an altered responsiveness to IGF-I in vitro, as evidenced by (i) loss of IGF-I-induced receptor phosphorylation and Shc recruitment, (ii) reduced IGF-I (but not IGF-II)-induced cellular proliferation and migration, (iii) decreased anchorage-independent growth and (iv) reduced plasma membrane levels of IGF-IR. These changes resulted in increased apoptosis in vivo and an impaired ability of the cells to form liver metastases. The results demonstrate that cathepsin L expression levels regulate cell responsiveness to IGF-I and thereby identify a novel function for cathepsin L in the control of the tumorigenic/metastatic phenotype.

Inhibitory effect of the sugarcane cystatin CaneCPI-4 on cathepsins B and L and human breast cancer cell invasion

The lysosomal cysteine proteases cathepsin B and L play important roles in tumor cell invasion. An imbalance between these cathepsins and their endogenous inhibitors, the cystatins, has been associated with development of the metastatic phenotype. Accordingly, many studies have indicated potential use of cystatins in therapeutic approaches. We report a novel cystatin from sugarcane (Saccharum officinarum), CaneCPI-4, with strong inhibitory activity against cathepsins B (Ki=0.83 nm) and L (Ki=0.021 nm). The invasive ability of MDA-MB-231 human breast cancer cells expressing CaneCPI-4 was only slightly decreased. In contrast, addition of low, non-toxic concentrations of recombinant His-tagged CaneCPI-4 significantly reduced invasion through a Matrigel matrix. Immunoblot analyses failed to detect the recombinant protein inside cells, indicating that the cystatin was not internalized by endocytosis, but exerted its anti-invasive effect mainly through inhibition of extracellular cathepsins. Our findings open the possibility of considering phytocystatins for anti-cancer strategies.

Cathepsins and osteosarcoma: Expression analysis identifies cathepsin K as an indicator of metastasis

Osteosarcoma is the most frequent malignant bone tumor with a poor survival rate for patients with metastasis. Previous studies have shown that beside other proteases, distinct sets of cathepsins are involved in the process of metastasis of different tumors. In this study we investigated the expression of cathepsin proteases in human osteosarcoma metastasis. First, the mRNA expression of 14 human cathepsins was studied in SAOS-2 osteosarcoma cells and the highly metastatic LM5 and LM7 sublines by reverse transcriptase (RT)-polymerase chain reaction (PCR). The expression of cathepsin D, K, and L mRNA was found upregulated and that of cathepsin F, H, and V downregulated in the highly metastatic LM5 and LM7 cells. A subgroup of the cathepsin proteases was further studied at the protein level by Western blot analysis of cell extracts. The expression of cathepsin B and H was decreased and that of cathepsin D, K, and L was increased in the highly metastatic cell lines as compared to the SAOS-2 cell line. Diagnostic relevance of cathepsin K expression in osteosarcoma was revealed upon correlation of survival and metastasis with immunohistochemical cathepsin K staining of biopsies collected from 92 patients prior to chemotherapy. Patients with metastatic high-grade osteosarcoma and low cathepsin K expression at diagnosis had a better prognosis than those with high expression. Thus, it appears that cathepsin K expression is of predictive prognostic value for patients with high-grade tumors and metastasis at diagnosis.

Loss of cathepsin L activity promotes claudin-1 overexpression and intestinal neoplasia

Intestinal epithelial integrity and polarity are maintained by cohesive interactions between cells via the formation of tight junctions. Irregularities in tight junctions have only recently been found to be associated with the initiation and progression of intestinal neoplasia. The claudin family of proteins is integral to the structure and function of the tight junction but little is known of the molecular events that regulate the expression of these components. The present report identifies cathepsin L, classically a lysosomal cysteine protease, as being induced during intestinal epithelial cell polarization and differentiation. Inhibition of intracellular cathepsin L activity results in the accumulation of disorganized cell layers and a decline in the expression of differentiation markers in cultured intestinal epithelial cells. This coincides with a rapid up-regulation of claudin-1 protein accumulation. Mutant mice defective in cathepsin L activity (furless) display an elevated level of intestinal claudin-1 and claudin-2 expression. Loss of cathepsin L activity leads to a marked increase in tumor multiplicity in the intestine of Apc(Min) mice. Given the traditionally viewed biological role of cathepsin L in the processing of lysosomal content as well as in pathological extracellular matrix remodeling, the results here demonstrate an as yet unsuspected intracellular role for this protease in normal intestinal epithelial polarization and initiation of neoplasia.

Cathepsin L increases invasion and migration of B16 melanoma

Background

Most cancers express elevated protease levels which contribute to certain aspects of tumor behavior such as growth, metastatic spread, and angiogenesis. Elevation of the cathepsins of the cysteine protease family correlates with increased invasion of tumor cells. Cysteine proteases such as cathepsins B, H and L type participate in tumor cell invasion as extracellular proteases, yet are enzymes whose exact roles in metastasis are still being elucidated.

Methods

We have examined the role of cathepsin L in highly metastatic B16F10 murine melanoma cells through genetic antisense constructs of cathepsin L. The effects of cathepsin L antisense were examined for melanoma cell proliferation, invasion, migration and adhesion.

Results

Antisense expression of cathepsin L, while decreasing enzyme activity in cell lysates, did not influence cell proliferation. Cathepsin L contributed to melanoma cell invasion and also augmented melanoma cell migration. Further, we demonstrated the adhesion of cathepsin L down-regulated clones was unaltered to fibronectin, laminin, and collagen. Finally, the inhibition of melanoma cell migration via down-regulation of cathepsin L appears to be independent of cystatin C expression.

Conclusion

This study shows that cathepsin L facilitates high metastatic B16 melanoma cell invasion and migration. The mechanism of migration inhibition by decreased cathepsin L is independent of cystatin C levels. Since metastasis depends upon both the invasiveness and migration of tumor cells, cathepsin L may be a therapeutic target of strong clinical interest.

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.

Relaxin enhances the oncogenic potential of human thyroid carcinoma cells

The role of members of the insulin-like superfamily in human thyroid carcinoma is primarily unknown. Here we demonstrate the presence of RLN2 relaxin and relaxin receptor LGR7 in human papillary, follicular, and undifferentiated anaplastic thyroid carcinoma suggesting a specific involvement of relaxin-LGR7 signaling in thyroid carcinoma. Stable transfectants of the LGR7-positive human follicular thyroid carcinoma cell lines FTC-133 and FTC-238 that secrete bioactive proRLN2 revealed this hormone to act as a multifunctional endocrine factor in thyroid carcinoma cells. Although RLN2 did not act as a mitogen, it acted as an autocrine/paracrine factor and significantly increased anchorage-independent growth and thyroid carcinoma cell motility and invasiveness through elastin matrices. Suppression of LGR7 expression by LGR7-siRNA abolished the RLN2-mediated accelerated tumor cell motility. The increased elastinolytic activity correlated with enhanced production and secretion of the lysosomal proteinases cathepsin-D (cath-D) and cath-L forms hereby identified as new RLN2 target molecules in human neoplastic thyrocytes. We found the intracellular distribution of procath-L specifically altered in RLN2 transfectants, providing first evidence for selective actions of relaxin on the powerful elastinolytic cath-L production, storage, and secretion in thyroid carcinoma cells. Thus, relaxin enhances the oncogenic potential and acts as novel endocrine modulator of invasiveness in human thyroid carcinoma cells.

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.

Antiprotease therapy in cancer: hot or not?

The activity of a set of peptidases (proteases) involved in cancer progression is collectively known as the cancer 'degradome'. Invasion and metastasis were initially considered as late events in cancer development and the processes in which proteases were involved. However, recent studies indicate that invasion and metastasis are not late events, but can occur during early stages as well. Moreover, other processes occurring in various stages of cancer progression are also protease-dependent, such as (upregulation of) cell proliferation, (downregulation of) apoptosis, involvement of white blood cells, angiogenesis and induction of multi-drug resistance. Proteolytic activity in tumours is regulated in a complex manner, as both genetically unstable cancer cells and stable stromal cells, such as fibroblasts, endothelial cells and inflammatory cells, are involved. In vitro studies and studies using animal models have clearly shown protease dependency of many processes in carcinogenesis. However, clinical trials using protease inhibitors have thus far been unsuccessful except for a few applications of matrix metalloprotease (MMP) inhibitors when used in combination with cytostatic anticancer agents and/or in the early stages of cancer. Antithrombotics, such as low-molecular-weight heparin and warfarin, were also successful in clinical trials, probably by interfering with proteases of the coagulation cascade. The two-way association between cancer and thrombosis has long been recognised in the clinic. The poor outcome of other clinical trials of protease inhibitors is probably due to the late stages of cancer of the patient populations included, and the limited understanding of the complex regulation and effects of the activity of the various proteases in tumours depending on, among others, tumour type and stage, interactions between the cancer cells, other cells and the extracellular matrix in tumours. Therefore, a better fundamental understanding of the proteolytic complexity in tumours is essential before clinical trials can be rationally designed. At present, antithrombotics, the urokinase-type plasminogen activator system, the membrane-bound membrane-type 1-MMP, cathepsin L and the proteasome seem the most promising candidates as targets for anticancer strategies in early stages of cancer in combination with cytotoxic drugs. Moreover, metronomic therapy is an attractive approach using low doses of inhibitors for prolonged periods of time without interruption to specifically target endothelial cells that are involved in angiogenesis.

The importance of cysteine cathepsin proteases for placental development

The typically lysosomal family of cysteine cathepsin proteases has been implicated in the development of the placenta in particular, from studies in the mouse. Here, we analysed overall expression, regulation and presence of transcript isoforms of cysteine cathepsins during human extra-embryonic development. All 11 family members are expressed in human placental tissues, and many are differentially regulated during gestation. Several cysteine cathepsins exhibit deregulated expression levels in placentas from pregnancies complicated by pre-eclampsia. The localization of cathepsin B predominantly in placental and decidual macrophages suggests a role in the physiological functions of these cells in mediating villous angiogenesis and decidual apoptosis. Cathepsin L levels are highest in a subpopulation of invasive cytotrophoblasts. Reflecting the expression pattern of two murine cathepsins, these data give insights into the evolutionary conservation of cathepsin function that is not necessarily exhibited by gene pairs defined by highest sequence similarity. Furthermore, cathepsin L protein localization in uterine epithelial cells demonstrates the in vivo occurrence of intranuclear cathepsin L isoforms. The zonally restricted expression of cathepsin in the syncytiotrophoblast may be important for the metabolic breakdown of maternal nutrients. Overall, the distribution and abnormal expression levels in pre-eclamptic placentas indicate that cysteine cathepsins may play important roles during normal placentation and in the etiology of pre-eclampsia.

Helicobacter pylori encoding the pathogenicity island activates matrix metalloproteinase 1 in gastric epithelial cells via JNK and ERK

Helicobacter pylori colonizes the human gastric epithelium and induces an inflammatory response that is a trigger for gastric carcinogenesis. Matrix metalloproteinases (MMPs) have recently been shown to be up-regulated in gastric epithelial cells infected with H. pylori and might contribute to the pathogenesis of peptic ulcer. The aim of this study was to extend the knowledge about the effect of H. pylori infection on MMP-1 expression by gastric epithelial cells, the kinetics of induction, the pathogenetic properties of the bacterium, and the intracellular signaling pathways required for MMP-1 up-regulation. Expression of MMP-1 was induced more than 10-fold by co-culture of AGS+cells with H. pylori strains carrying the pathogenicity island (PAI). H. pylori strains with mutations in the PAI and a defective type IV secretion system had no effect on MMP-1. Double immunofluorescence revealed strong MMP-1 staining in epithelial cells of gastric biopsies at sites of bacterial attachment. In vitro, MMP-1 is up-regulated by interleukin-1beta and tumor necrosis factor-alpha, but these regulatory mechanisms are not operating in H. pylori infection as shown by inhibitory antibodies. Specific inhibitors of JNK kinase and ERK1/2 kinase were found to suppress the H. pylori-induced MMP-1 expression and activity. AGS cells treated with antisense MMP-1 showed a significantly reduced potential to degrade reconstituted basement membrane. Our results suggest that in gastric epithelial cells, H. pylori up-regulates MMP-1 in a type IV secretion system-dependent manner via JNK and ERK1/2. Induction of MMP-1 is further implicated in complex processes induced by H. pylori, resulting in tissue degradation and remodeling of the gastric mucosa.

Expression of cathepsin L in human tumor cells is under the control of distinct regulatory mechanisms

Cathepsin L, a cysteine protease, is overexpressed in human tumor cells and plays a major role in melanoma progression. Our aim was herein to identify molecular mechanisms, which contribute to its overexpression. We found that cathepsin L protein expression correlated with mRNA level in tumor cells. Therefore, we focused on mechanisms involved in cathepsin L mRNA regulation. CpG island was localized in the 5' region of cathepsin L gene that encompassed regulatory regions identified as essential for promoter activity. CpG dinucleotides, not methylated in any melanoma cells analysed, were methylated in a B lymphoma cell line, which poorly express cathepsin L. Our data demonstrate that in lymphoma cells, cathepsin L silencing was methylation-dependent. Furthermore, gene amplification was involved in cathepsin L overexpression in one melanoma cell line, while transcriptional mechanisms but not mRNA stability are responsible of cathepsin L overexpression in others melanoma cells. In addition, NF-Y, Sp1, Sp2 and Sp3 transcription factors, essential to basal cathepsin L transcription, are not directly involved in overexpression. Thus, our data provides the first demonstration that cathepsin L expression in tumor cells is under the control of distinct molecular mechanisms.

Up-regulation of cathepsin X in Helicobacter pylori gastritis and gastric cancer

Recently, we identified increased cathepsin X expression in H. pylori-infected gastric mucosa. Here, we describe further up-regulation in gastric cancer and report on the role of inflammatory cytokines required for cathepsin X up-regulation in H. pylori-infected gastric mucosa, as well as on consequences for cellular invasion. Biopsy specimens were taken from the antrum, corpus and cardia of H. pylori-infected and non-infected patients. Gastric cancer samples were obtained from patients undergoing gastric surgery. Cathepsin X was detected in gastric mucosa by quantitative real-time RT-PCR, western blotting and immunohistochemistry. Induction of cathepsin X expression in epithelial and inflammatory cells caused by H. pylori infection was tested in in vitro contact and non-contact co-cultures of AGS cells and monocytic cells. Patients with H. pylori gastritis showed significantly higher cathepsin X mRNA (2.5-fold) and protein (1.6-fold) expression than H. pylori-negative patients. Cathepsin X was also up-regulated in gastric cancer (3-12-fold) compared to non-neoplastic mucosa. Cathepsin X was predominantly expressed by macrophages in the mucosal stroma and in glands of the antral mucosa. In addition, tumour cells stained for cathepsin X in 26 (68%) patients with gastric carcinoma. In general, staining was significantly more common (20 vs. 6 patients) and more intense (3.55 vs. 0.83) in intestinal type gastric cancer than in the diffuse type. In vitro cell culture experiments revealed that intercellular signalling between pathogenicity island (PAI)-positive H. pylori-infected epithelial cells and macrophages via soluble factors in the culture medium seems to be responsible for increased expression of cathepsin X in monocytes. Using antisense oligonucleotides, cathepsin X up-regulation was directly associated with higher invasiveness in vitro. Although no correlation of cathepsin X expression and TNM stage was found, our study demonstrates that cathepsin X plays a role not only in the chronic inflammation of gastric mucosa but also in the tumourigenesis of gastric cancer.

Establishment and characterization of the permanent human cell line C3842 derived from a secondary chondrosarcoma in Ollier's disease

The permanent human cell line C3842 was established from a secondary chondrosarcoma in a typical case of Ollier's disease. In the present study, we analyzed the morphological, cytogenetic and molecular biological characteristics of the cultured cells in comparison with the original tumor and investigated the invasion properties of the tumor model using functional imaging of proteolysis, matrigel assay and chick chorioallantoic membrane assay. C3842 cells exhibit the typical features of malignant cartilage tumor cells in vitro, including the expression of collagen types II, IX, XI and aggrecan. The proteolytic ability of C3842 cells is attributed to the expression of several proteases, such as cathepsin B, urokinase plasminogen activator and matrix-metalloproteinase-2, which enable the cells to degrade collagen type I and to permeate matrigel matrix. In accordance with the biological features in vivo, C3842 cells are not able to invade through the epithelium of the chick chorioallantoic membrane. In conclusion, the cell line C3842 provides the first model of a secondary chondrosarcoma in Ollier's disease in vitro, which is characterized by distinct features of such malignant cartilage tumors.

Cathepsin L is required for endothelial progenitor cell-induced neovascularization

Infusion of endothelial progenitor cells (EPC), but not of mature endothelial cells, promotes neovascularization after ischemia. We performed gene expression profiling of EPC and endothelial cells to identify genes that might be important for the neovascularization capacity of EPC. Notably, the protease cathepsin L (CathL) was highly expressed in EPC as opposed to endothelial cells and was essential for matrix degradation and invasion by EPC in vitro. CathL-deficient mice showed impaired functional recovery following hind limb ischemia, supporting the concept of a crucial role for CathL in postnatal neovascularization. Infused CathL-deficient progenitor cells neither homed to sites of ischemia nor augmented neovascularization. Forced expression of CathL in mature endothelial cells considerably enhanced their invasive activity and sufficed to confer their capacity for neovascularization in vivo. We concluded that CathL has a critical role in the integration of circulating EPC into ischemic tissue and is required for EPC-mediated neovascularization.

Interactions between human colon carcinoma cells, fibroblasts and monocytic cells in coculture--regulation of cathepsin B expression and invasiveness

To elucidate the importance of the tumor/host interaction in malignant tumors, we investigated the colon carcinoma cell line HT-29 in coculture with monocytic cells (THP-1) and fibroblasts (175BR) for cathepsin B expression and activity. The tumor cells were grown in monolayer cultures or as multicellular tumor spheroids. After coculture, the three cell types were separated by labeled magnetic beads for cathepsin B mRNA and protein analysis. The invasive potential was studied in in vitro invasion assays. The expression level of cathepsin B was found to be 10-fold increased in three dimensional spheroids of HT-29 compared to HT-29 monolayers. The coculture of HT-29 with THP-1 cells and/or human fibroblasts led to a considerable increase in cathepsin B mRNA expression in both tumor and tumor-associated cells. The invasive potential of the tumor cells was 5 times increased by adding monocytic cells to the assay system. This is dependent on the functional activity of cathepsin B as shown by specific siRNA's and seems to be regulated by activation of ERK1/2 and p38 signal transduction pathways.

Analysis of the type IV secretion system-dependent cell motility of Helicobacter pylori-infected epithelial cells

The pathogenesis of Helicobacter pylori-associated disorders is strongly dependent on a specialized type IV secretion system (T4SS) encoded by the cag pathogenicity island (PAI). Cytotoxin-associated gene A (CagA) is the only known H. pylori protein translocated into the host cell followed by tyrosine phosphorylation through host protein kinases. H. pylori induces cellular processes which are either PAI- or CagA-dependent (e.g., cell motility), PAI-dependent, but CagA-independent (e.g., interleukin-8 release), or PAI- and CagA-independent (e.g., cyclooxygenase-2 release). Here, we investigated H. pylori strains mutated in single PAI genes of the wild type strain Hp26695 and their effects on cell motility. We found 17 gene products out of 27 PAI genes playing a superordinated role and five PAI-encoded proteins exhibiting a clearly critical role in motogenic host cell responses, whereas the remaining five PAI gene products had no significant influence on the motogenic response in reaction to H. pylori infection. This study clearly demonstrated that H. pylori-induced cell motility and invasive growth involve type IV secretion system-dependent signalling as well as translocated and phosphorylated CagA. These findings reveal a deeper insight in to the meaning of the T4SS of H. pylori for host cell motility.

Targeting cathepsin L (CL) by specific ribozymes decreases CL protein synthesis and cartilage destruction in rheumatoid arthritis

The present study was undertaken to examine whether ribozymes cleaving specifically cathepsin L (CL) mRNA are able to decrease the synthesis of CL protease in rheumatoid arthritis synovial fibroblasts (RA-SF) and thereby reduce the invasiveness into cartilage both in vitro and in the SCID mouse coimplantation model of RA. Two different ribozymes that cleave CL mRNA specifically at positions 533 (RzCL533) and 790 (RzCL790) were generated. Using retroviral gene transfer, RA-SF were transduced with the ribozyme constructs or the empty vector. To examine the effect of the ribozymes on the mRNA level, quantitative analysis for CL mRNA was performed using real-time PCR. For evaluation on the protein level, ELISA using specific anti-CL antibodies was performed. In addition, transduced RA-SF were examined in vitro in a three-dimensional destruction assay evaluating their ability to degrade extracellular matrix produced by human chondrocytes. Matrix destruction was monitored by the release of soluble glycosaminoglycans (sGAG). Using the in vivo SCID mouse coimplantation model of RA, RzCL533-transduced RA-SF and control cells were coimplanted with human cartilage for 60 days. After being killed, invasion of RA-SF into the cartilage was evaluated by using a semiquantitative score. Transduction of RA-SF with RzCL533 and RzCL790 ribozymes decreased significantly the expression of CL mRNA to 44% (range 25-62%) and 20% (range 1-43%), respectively, when compared to mock-transduced cells. The protein concentration of CL in the cell culture supernatants of transduced RA-SF was decreased from 16.0 ng/ml in the mock constructs to 4.1 and 8.2 ng/ml (mean), respectively. Using the in vitro cartilage destruction assay, the release of sGAG decreased to 46 and 60%, respectively, after 14 days when compared to mock-transduced cells. In the SCID mouse coimplantation model of RA, RzCL533-transduced RA-SF revealed a significant lower cartilage invasion when compared to mock and untransduced cells. Using retroviral gene transfer, ribozymes cleaving CL mRNA inhibit specifically the synthesis of this matrix-degrading enzyme and reduce cartilage destruction in in vitro and in vivo models. Our study therefore suggests that ribozymes targeting CL could be a novel and efficient tool to inhibit joint destruction in RA.

Selective suppression of cathepsin L by antisense cDNA impairs human brain tumor cell invasion in vitro and promotes apoptosis

Invasion and metastasis of certain tumors are accompanied by increased mRNA protein levels and enzymatic activity of cathepsin L. Cathepsin L has also been suggested to play a role in the proteolytic cascades associated with apoptosis. To investigate the role of cathepsin L in brain tumor invasion and apoptosis, the human glioma cell line, IPTP, was stably transfected with full-length antisense and sense cDNA of cathepsin L. Down-regulation of cathepsin L by antisense cDNA significantly impaired (up to 70%) glioma cell invasion in vitro and markedly increased glioma cell apoptosis induced by staurosporine. Compared to control and parental cell lines, antisense down-regulation of cathepsin L was associated with an earlier induction of caspase-3 activity. Up-regulation of cathepsin L activity by sense cDNA was associated with reduced apoptosis and later induction of caspase-3 activity. Moreover, down-regulation of cathepsin L lowered the expression of antiapoptotic protein Bcl-2, whereas up-regulation increased the expression of Bcl-2, indicating that cathepsin L acts upstream of caspase-3. These data show that cathepsin L is an important protein mediating the malignancy of gliomas and its inhibition may diminish their invasion and lead to increased tumor cell apoptosis by reducing apoptotic threshold.

Functional consequences of cathepsin L deficiency in human lung epithelial cells

Cathepsin L is a cysteine protease of the papain family. Lung epithelial cells play an important role in host defence. The aim of the present study was to investigate the functional role of cathepsin L in the human lung carcinoma cell line A549. Cathepsin L-deficient A549 clones were generated. They showed a significant lower proliferation and secreted 5- to 8-fold more IL-8 than the control cells. The production of IL-6, IL-18, and TGF-beta1/2 was not affected significantly. It was shown that the cells upregulate IL-8 transcription and that IL-8 in the culture supernatant is necessary for the containment of cellular proliferation. In conclusion, the data show that suppression of cathepsin L expression in A549 cells leads to a growth inhibition which is partially compensated by an upregulation of IL-8 production.