Primary tumour expression of the cysteine cathepsin inhibitor Stefin A inhibits distant metastasis in breast cancer

Cystatin A promotes the antitumor activity of T helper type 1 cells and dendritic cells in murine models of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a disease with poor prognosis due to diagnostic and therapeutic limitations. We previously identified cystatin A (CSTA) as a PDAC biomarker and have conducted the present study to investigate the antitumor effects of CSTA. PDAC murine models were established with genetically modified PAN02 tumor cell lines to evaluate the antitumor immune response. PDAC mouse survival was significantly longer with CSTA, and its antitumor effect was mediated mainly by CD4+ cells and partly by CD8+ cells. We also observed an increased infiltration of CD4+ and CD8+ cells in tumors of mice overexpressing CSTA. Phenotypically, we confirmed higher T helper type 1 (Th1) cell activity and increased frequency and activity of M1 macrophages and dendritic cells (DCs) in CSTA-overexpressing mice. Gene expression analysis highlighted pathways related to interferon gamma (IFN-γ) induction and Th1 lymphocyte activation that were induced by CSTA. Macrophages and DCs shifted toward proinflammatory antitumor phenotypes. Furthermore, activated splenocytes of PDAC model mice expressing CSTA had increased proapoptotic activity. CSTA also promoted the selective migration of CD4+ and CD11c+ immune cells in an in vitro migration assay. In conclusion, CSTA exerts antitumor effects by enhancing Th1-mediated antitumor effects through promotion of DC and M1 macrophage activity, thereby increasing immune cell chemotaxis. CSTA could be a novel therapeutic candidate for PDAC.

An Integrated Approach to Protein Discovery and Detection From Complex Biofluids

Ovarian cancer, a leading cause of cancer-related deaths among women, has been notoriously difficult to screen for and diagnose early, as early detection significantly improves survival. Researchers and clinicians seek routinely usable and noninvasive screening methods; however, available methods (i.e., biomarker screening) lack desirable sensitivity/specificity. The most fatal form, high-grade serous ovarian cancer, often originate in the fallopian tube; therefore, sampling from the vaginal environment provides more proximal sources for tumor detection. To address these shortcomings and leverage proximal sampling, we developed an untargeted mass spectrometry microprotein profiling method and identified cystatin A, which was validated in an animal model. To overcome the limits of detection inherent to mass spectrometry, we demonstrated that cystatin A is present at 100 pM concentrations using a label-free microtoroid resonator and translated our workflow to patient-derived clinical samples, highlighting the potential utility of early stage detection where biomarker levels would be low.

Cysteine Cathepsins in Breast Cancer: Promising Targets for Fluorescence-Guided Surgery

The majority of breast cancer patients is treated with breast-conserving surgery (BCS) combined with adjuvant radiation therapy. Up to 40% of patients has a tumor-positive resection margin after BCS, which necessitates re-resection or additional boost radiation. Cathepsin-targeted near-infrared fluorescence imaging during BCS could be used to detect residual cancer in the surgical cavity and guide additional resection, thereby preventing tumor-positive resection margins and associated mutilating treatments. The cysteine cathepsins are a family of proteases that play a major role in normal cellular physiology and neoplastic transformation. In breast cancer, the increased enzymatic activity and aberrant localization of many of the cysteine cathepsins drive tumor progression, proliferation, invasion, and metastasis. The upregulation of cysteine cathepsins in breast cancer cells indicates their potential as a target for intraoperative fluorescence imaging. This review provides a summary of the current knowledge on the role and expression of the most important cysteine cathepsins in breast cancer to better understand their potential as a target for fluorescence-guided surgery (FGS). In addition, it gives an overview of the cathepsin-targeted fluorescent probes that have been investigated preclinically and in breast cancer patients. The current review underscores that cysteine cathepsins are highly suitable molecular targets for FGS because of favorable expression and activity patterns in virtually all breast cancer subtypes. This is confirmed by cathepsin-targeted fluorescent probes that have been shown to facilitate in vivo breast cancer visualization and tumor resection in mouse models and breast cancer patients. These findings indicate that cathepsin-targeted FGS has potential to improve treatment outcomes in breast cancer patients.

Stimuli-Sensitive Linear-Dendritic Block Copolymer-Drug Prodrug as a Nanoplatform for Tumor Combination Therapy

Linear-dendritic block copolymer (LDBCs) are highly attractive candidates for smart drug-delivery vehicles. Herein, an amphiphilic poly[(ethylene glycol) methyl ether methacrylate] (POEGMA) linear-peptide dendritic prodrug of doxorubicin (DOX) prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization is reported. The hydrophobic-dye-based photosensitizer chlorin e6 (Ce6) is employed for encapsulation in the prodrug nanoparticles (NPs) to obtain an LDBCs-based drug-delivery system (LD-DOX/Ce6) that offers a combination cancer therapy. Due to the presence of Gly-Phe-Leu-Gly peptides and hydrazone bonds in the prodrug structure, LD-DOX/Ce6 is degraded into small fragments, thus specifically triggering the intracellular release of DOX and Ce6 in the tumor microenvironment. Bioinformatics analysis suggests that LD-DOX/Ce6 with laser irradiation treatment significantly induces apoptosis, DNA damage, and cell cycle arrest. The combination treatment can not only suppress tumor growth, but also significantly reduce tumor metastasis compared with treatments with DOX or Ce6 through regulating EMT pathway, TGFβ pathway, angiogenesis, and the hypoxia pathway. LD-DOX/Ce6 displays a synergistic chemo-photodynamic antitumor efficacy, resulting in a high inhibition in tumor growth and metastasis, while maintaining an excellent biosafety. Therefore, this study demonstrates the potential of the biodegradable and tumor-microenvironment-responsive LDBCs as an intelligent multifunctional drug-delivery vehicle for high-efficiency cancer combination therapy.

Cathepsin B-responsive and gadolinium-labeled branched glycopolymer-PTX conjugate-derived nanotheranostics for cancer treatment

Multi-modal therapeutics are emerging for simultaneous diagnosis and treatment of cancer. Polymeric carriers are often employed for loading multiple drugs due to their versatility and controlled release of these drugs in response to a tumor specific microenvironment. A theranostic nanomedicine was designed and prepared by complexing a small gadolinium chelate, conjugating a chemotherapeutic drug PTX through a cathepsin B-responsive linker and covalently bonding a fluorescent probe pheophorbide a (Ppa) with a branched glycopolymer. The branched prodrug-based nanosystem was degradable in the tumor microenvironment with overexpressed cathepsin B, and PTX was simultaneously released to exert its therapeutic effect. The theranostic nanomedicine, branched glycopolymer-PTX-DOTA-Gd, had an extended circulation time, enhanced accumulation in tumors, and excellent biocompatibility with significantly reduced gadolinium ion (Gd³⁺) retention after 96 h post-injection. Enhanced imaging contrast up to 24 h post-injection and excellent antitumor efficacy with a tumor inhibition rate more than 90% were achieved from glycopolymer-PTX-DOTA-Gd without obvious systematic toxicity. This branched polymeric prodrug-based nanomedicine is very promising for safe and effective diagnosis and treatment of cancer.

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A cathepsin B-responsive theranostic nanomedicine (glycopolymer-PTX-DOTA-Gd) based on a branched glycopolymer was prepared.

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Glycopolymer-PTX-DOTA-Gd can be specifically degradated and release drug at tumor enviornment.

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Glycopolymer-PTX-DOTA-Gd enhance the contrast of magnetic resonance imaging (MRI) at tumor sites.

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The nanomedicine have good biocompatibility, excellent tumor targeting and anti-tumor efficacy.

Rational Design of a Humanized Antibody Inhibitor of Cathepsin B

Cathepsin B (CTSB) is an abundant cysteine protease that functions in both endolysosomal compartments and extracellular regions. A considerable number of preclinical and clinical studies indicate that CTSB is implicated in many human diseases. Expression levels and activity of CTSB significantly correlate with disease progression and severity. Current inhibitors of CTSB are lack of adequate specificity and pharmacological activities. Through structure-guided rational design, we hereby designed and generated a humanized antibody inhibitor targeting human CTSB. This was achieved by genetically fusing the propeptide of procathepsin B, a naturally occurring inhibitor of CTSB, into heavy chain complementarity-determining region 3 (CDR3H) of Herceptin that is used in the clinic for the treatment of breast cancer. The resulting antibody-propeptide fusion displayed high specificity for inhibiting CTSB proteolytic activity at nanomolar levels. Pharmacokinetic studies in mice revealed a plasma half-life of approximately 42 h for this anti-CTSB antibody inhibitor, comparable to that of the parental Herceptin scaffold. This study demonstrates a new approach for the efficient generation of humanized antibody inhibitors with high potency and specificity for human CTSB, which may be extended to develop antibody inhibitors against other disease relevant cathepsin proteases.

Interplay of ERα binding and DNA methylation in the intron-2 determines the expression and estrogen regulation of cystatin A in breast cancer cells

Despite advances in early detection and treatment, invasion and metastasis of breast tumors remains a major hurdle. Cystatin A (CSTA, also called stefin A), an estrogen-regulated gene in breast cancer cells, is an inhibitor of cysteine cathepsins, and a purported tumor suppressor. Loss of CSTA expression in breast tumors evidently shifts the balance in favor of cysteine cathepsins, thereby promoting extracellular matrix remodeling, tumor invasion and metastasis. However, the underlying mechanism behind the loss of CSTA expression in breast tumors is not known. Here, we have analyzed CSTA expression, and methylation of upstream and intron-2 CpG sites within the CSTA locus in human breast cancer cell lines and breast tumors of the TCGA cohort. Results showed an inverse relationship between expression and methylation. Sequence analysis revealed a potential estrogen response element (ERE) in the intron-2. Analysis of ChIP-seq data (ERP000380) and our own ChIP experiments showed that 17β-estradiol (E2) enhanced ERα binding to this ERE in MCF-7 cells. This ERE was located amidst the differentially methylated intron-2 CpG sites, which provoked us to examine the possible conflict between estrogen-regulation of CSTA and DNA methylation in the intron-2. We analyzed the expression of CSTA and its regulation by E2 in MDA-MB-231 and T47D cells subjected to global demethylation by 5-azacytidine (5-aza). 5-aza significantly demethylated intron-2 CpGs, and enhanced estrogen-induced ERα occupancy at the intron-2 ERE, leading to restoration of estrogen-regulation. Taken together, our results indicate that DNA methylation-dependent silencing could play a significant role in the loss of CSTA expression in breast tumors. The potential of DNA methylation as an indicator of CSTA expression or as a marker of tumor progression can be explored in future investigations. Furthermore, our results indicate the convergence of ERα-mediated estrogen regulation and DNA methylation in the intron-2, thereby offering a novel context to understand the role of estrogen-ERα signaling axis in breast tumor invasion and metastasis.

Cystatins in cancer progression: More than just cathepsin inhibitors

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

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

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

A survey of metastasis suppressors in Metazoa

Metastasis suppressors are genes/proteins involved in regulation of one or more steps of the metastatic cascade while having little or no effect on tumor growth. The list of putative metastasis suppressors is constantly increasing although thorough understanding of their biochemical mechanism(s) and evolutionary history is still lacking. Little is known about tumor-related genes in invertebrates, especially non-bilaterians and unicellular relatives of animals. However, in the last few years we have been witnessing a growing interest in this subject since it has been shown that many disease-related genes are already present in simple non-bilateral animals and even in their unicellular relatives. Studying human diseases using simpler organisms that may better represent the ancestral conditions in which the specific disease-related genes appeared could provide better understanding of how those genes function. This review represents a compilation of published literature and our bioinformatics analysis to gain a general insight into the evolutionary history of metastasis-suppressor genes in animals (Metazoa). Our survey suggests that metastasis-suppressor genes emerged in three different periods in the evolution of Metazoa: before the origin of metazoans, with the emergence of first animals and at the origin of vertebrates.

Hypericin targets osteoclast and prevents breast cancer-induced bone metastasis via NFATc1 signaling pathway

Bone is the most common target organ of metastasis of breast cancers. This produces considerable morbidity due to skeletal-related events, and severely reduces the quality of life. Increased osteoclast activity is implicated in breast cancer outgrowth in the bone microenvironment. Our previous observation of an anti-osteoclastic activity of hypericin, a natural plant compound, led us to investigate whether hypericin could inhibit bone metastasis and osteolysis caused by breast cancer. We find that hypericin inhibited the upregulation of osteoclasts stimulated by breast cancer cells. The activity of hypericin on osteoclasts and breast cancer-mediated osteoclastogenesis was associated with the inhibition of NFATc1 signaling pathway and attenuation of Ca2+ oscillation. Furthermore, hypericin suppresses invasion and migration in breast cancer cells, but has little effect on breast cancer-cell induced RANKL/OPG ratio in osteoblast or the expression of osteoclast-activating factors. Administration of hypericin could reduce tumor burden, osteolysis induced by direct inoculation of MDA-MB-231 cells into the bone marrow cavity of the tibia as well as metastasis of bone and improve survival in an experimental metastasis model by intracardiac injection of MDA-MB-231 breast cancer cells. Taken together, these results suggest that hypericin may be a potential natural agent for preventing and treating bone destruction in patients with bone metastasis due to breast cancer.

Cystatin A suppresses tumor cell growth through inhibiting epithelial to mesenchymal transition in human lung cancer

Cystatin A (CSTA), belonging to type 1 cystatin super-family, is expressed primarily in epithelial and lymphoid tissues for protecting cells from proteolysis of cytoplasmic and cytoskeletal proteins by cathepsins B, H and L. CSTA acts as a tumor suppressor in esophageal cancer, however, its role in lung cancer has not yet been elucidated. Here we found that CSTA was down-regulated in all lung cancer cell lines compared to normal lung epithelial cells. CSTA was restored in most lung cancer cell lines after treatment with demethylation agent 5-aza-2-deoxycytidine and deacetylation agent Trichostatin. Bisulfite sequencing revealed that CSTA was partially methylated in the promoter and exon 1. In primary lung tumors, squamous cell carcinoma (SCC) significantly expressed more CSTA compared to adenocarcinoma (p<0.00001), and higher expression of CSTA was significantly associated with lower tumor grade (p<0.01). CSTA stable transfection reduced the activity of cathepsin B and inhibited the ability of colony formation, migration and invasion, and enhanced gemcitabine-induced apoptosis. CSTA overexpression resulted in reduced activity of ERK, p-38, and AKT. Additionally, CSTA overexpression led to a mesenchymal to epithelial transition (MET) and prevented the TGF-β1-induced epithelial to mesenchymal transition (EMT) through inhibiting the ERK/MAPK pathway. In conclusion, our date indicate 1) epigenetic regulation is associated with CSTA gene silencing; 2) CSTA exerts tumor suppressive function through inhibiting MAPK and AKT pathways; 3) Overexpression of CSTA leads to MET and prevents TGF-β1-induced EMT by modulating the MAPK pathway; 4) CSTA may be a potential biomarker for lung SCC and tumor differentiation.

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

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

Particular gene upregulation and p53 heterogeneous expression in TP53-mutated maxillary carcinoma

It has been demonstrated that tumor protein p53 (TP53) mutation in maxillary squamous cell carcinoma, is more treatment-resistant compared with the carcinoma without TP53 mutation. However, the association between TP53 mutation and treatment resistance remains unclear. As a first step in understanding the biological differences between tumors with and without TP53 mutation, a comprehensive gene expression analysis of maxillary squamous cell carcinoma with or without TP53 mutation was performed. A total of 42 genes were identified to be differentially expressed by >4-fold. Quantification of their mRNA using quantitative polymerase chain reaction indicated 18 genes with high expression and three genes with low expression in TP53 mutated tumors vs. TP53 wild-type tumors. The 18 genes included eight cell adhesion (DSC3, GRHL1, EPPK1, PROM2, ANXA8, DSP, JUP, and KRT6B) and four cell growth inhibition (SFN, CLCA2, SAMD9 and TP63) genes. Among these genes, DSC3, SFN, and CSTA, whose expression was markedly increased, also demonstrated high protein expression in immunohistochemical staining of TP53 mutated tumors. The TP53 mutated tumors demonstrated high nuclear staining of the TP53 protein only in tumor cells at the tumor margins adjacent to the stroma, whereas the tumor interior was negative for TP53. However, all tumor cells of TP53 wild-type tumors exhibited positive nuclear staining for the TP53 protein. The combined findings suggest that TP53 mutated tumors possess a phenotype opposite to that associated with cancer progression and malignant transformation, and exhibit tumor cell heterogeneity between the tumor interior and margins.

Cationic liposome-mediated delivery of reovirus enhances the tumor cell-killing efficiencies of reovirus in reovirus-resistant tumor cells

Reovirus induces tumor cell death efficiently and specifically, and thus is currently undergoing clinical testing as an anticancer agent. In the intracellular trafficking of reovirus, proteolytic disassembly of reovirus capsid-proteins and subsequent penetration of viral particles into the cytosol are crucial steps. Cathepsins B and L are largely responsible for the proteolytic disassembly of reovirus. Reovirus efficiently lyses tumor cells exhibiting relatively high activities of cathepsins B and L, while tumor cells with low activities of cathepsins B and L are often refractory to reovirus, probably due to inefficient endo/lysosomal escape. In this study, in order to enhance the tumor cell-killing efficiencies of reovirus by promoting endo/lysosomal escape, especially in reovirus-resistant tumor cells, reovirus was complexed with a cationic liposome transfection reagent. Reovirus alone and reovirus-cationic liposome complex (reoplex) exhibited similar levels of tumor cell-killing efficiencies in reovirus-susceptible tumor cells, while reoplex mediated more than 30% higher levels of tumor cell-killing activities in reovirus-resistant tumor cells than reovirus alone. Reoplex-mediated tumor cell death was efficiently induced in the tumor cells pretreated with cathepsin inhibitors. The mRNA levels of interferon (IFN)-β and apoptotic genes were significantly elevated following reoplex treatment. These results suggest that cationic liposomes efficiently promoted delivery of reovirus to the cytosol, leading to induction of apoptosis.

Role of protease and protease inhibitors in cancer pathogenesis and treatment

Cancer is the second cause of death in 2015, and it has been estimated to surpass heart diseases as the leading cause of death in the next few years. Several mechanisms are involved in cancer pathogenesis. Studies have indicated that proteases are also implicated in tumor growth and progression which is highly dependent on nutrient and oxygen supply. On the other hand, protease inhibitors could be considered as a potent strategy in cancer therapy. On the basis of the type of the key amino acid in the active site of the protease and the mechanism of peptide bond cleavage, proteases can be classified into six groups: cysteine, serine, threonine, glutamic acid, aspartate proteases, as well as matrix metalloproteases. In this review, we focus on the role of different types of proteases and protease inhibitors in cancer pathogenesis.

Cysteine cathepsin activity suppresses osteoclastogenesis of myeloid-derived suppressor cells in breast cancer

Cysteine cathepsin proteases contribute to many normal cellular functions, and their aberrant activity within various cell types can contribute to many diseases, including breast cancer. It is now well accepted that cathepsin proteases have numerous cell-specific functions within the tumor microenvironment that function to promote tumor growth and invasion, such that they may be valid targets for anti-metastatic therapeutic approaches. Using activity-based probes, we have examined the activity and expression of cysteine cathepsins in a mouse model of breast cancer metastasis to bone. In mice bearing highly metastatic tumors, we detected abundant cysteine cathepsin expression and activity in myeloid-derived suppressor cells (MDSCs). These immature immune cells have known metastasis-promoting roles, including immunosuppression and osteoclastogenesis, and we assessed the contribution of cysteine cathepsins to these functions. Blocking cysteine cathepsin activity with multiple small-molecule inhibitors resulted in enhanced differentiation of multinucleated osteoclasts. This highlights a potential role for cysteine cathepsin activity in suppressing the fusion of osteoclast precursor cells. In support of this hypothesis, we found that expression and activity of key cysteine cathepsins were downregulated during MDSC-osteoclast differentiation. Another cysteine protease, legumain, also inhibits osteoclastogenesis, in part through modulation of cathepsin L activity. Together, these data suggest that cysteine protease inhibition is associated with enhanced osteoclastogenesis, a process that has been implicated in bone metastasis.

Low spinophilin expression enhances aggressive biological behavior of breast cancer

Spinophilin, a putative tumor suppressor gene, has been shown to be involved in the pathogenesis of certain types of cancer, but its role has never been systematically explored in breast cancer. In this study, we determined for the first time the expression pattern of spinophilin in human breast cancer molecular subtypes (n = 489) and correlated it with survival (n = 921). We stably reduced spinophilin expression in breast cancer cells and measured effects on cellular growth, apoptosis, anchorage-independent growth, migration, invasion and self-renewal capacity in vitro and metastases formation in vivo. Microarray profiling was used to determine the most abundantly expressed genes in spinophilin-silenced breast cancer cells. Spinophilin expression was significantly lower in basal-like breast cancer (p<0.001) and an independent poor prognostic factor in breast cancer patients (hazard ratio = 1.93, 95% confidence interval: 1.24-3.03; p = 0.004) A reduction of spinophilin levels increased cellular growth in breast cancer cells (p<0.05), without influencing activation of apoptosis. Anchorage-independent growth, migration and self-renewal capacity in vitro and metastatic potential in vivo were also significantly increased in spinophilin-silenced cells (p<0.05). Finally, we identified several differentially expressed genes in spinophilin-silenced cells. According to our data, low levels of spinophilin are associated with aggressive behavior of breast cancer.

Proteomic Analysis of Urine to Identify Breast Cancer Biomarker Candidates Using a Label-Free LC-MS/MS Approach

INTRODUCTION

Breast cancer is a complex heterogeneous disease and is a leading cause of death in women. Early diagnosis and monitoring progression of breast cancer are important for improving prognosis. The aim of this study was to identify protein biomarkers in urine for early screening detection and monitoring invasive breast cancer progression.

METHOD

We performed a comparative proteomic analysis using ion count relative quantification label free LC-MS/MS analysis of urine from breast cancer patients (n = 20) and healthy control women (n = 20).

RESULTS

Unbiased label free LC-MS/MS-based proteomics was used to provide a profile of abundant proteins in the biological system of breast cancer patients. Data analysis revealed 59 urinary proteins that were significantly different in breast cancer patients compared to the normal control subjects (p<0.05, fold change >3). Thirty-six urinary proteins were exclusively found in specific breast cancer stages, with 24 increasing and 12 decreasing in their abundance. Amongst the 59 significant urinary proteins identified, a list of 13 novel up-regulated proteins were revealed that may be used to detect breast cancer. These include stage specific markers associated with pre-invasive breast cancer in the ductal carcinoma in-situ (DCIS) samples (Leucine LRC36, MAST4 and Uncharacterized protein CI131), early invasive breast cancer (DYH8, HBA, PEPA, uncharacterized protein C4orf14 (CD014), filaggrin and MMRN2) and metastatic breast cancer (AGRIN, NEGR1, FIBA and Keratin KIC10). Preliminary validation of 3 potential markers (ECM1, MAST4 and filaggrin) identified was performed in breast cancer cell lines by Western blotting. One potential marker MAST4 was further validated in human breast cancer tissues as well as individual human breast cancer urine samples with immunohistochemistry and Western blotting, respectively.

CONCLUSIONS

Our results indicate that urine is a useful non-invasive source of biomarkers and the profile patterns (biomarkers) identified, have potential for clinical use in the detection of BC. Validation with a larger independent cohort of patients is required in the following study.

Cell cycle- and cancer-associated gene networks activated by Dsg2: evidence of cystatin A deregulation and a potential role in cell-cell adhesion

Cell-cell adhesion is paramount in providing and maintaining multicellular structure and signal transmission between cells. In the skin, disruption to desmosomal regulated intercellular connectivity may lead to disorders of keratinization and hyperproliferative disease including cancer. Recently we showed transgenic mice overexpressing desmoglein 2 (Dsg2) in the epidermis develop hyperplasia. Following microarray and gene network analysis, we demonstrate that Dsg2 caused a profound change in the transcriptome of keratinocytes in vivo and altered a number of genes important in epithelial dysplasia including: calcium-binding proteins (S100A8 and S100A9), members of the cyclin protein family, and the cysteine protease inhibitor cystatin A (CSTA). CSTA is deregulated in several skin cancers, including squamous cell carcinomas (SCC) and loss of function mutations lead to recessive skin fragility disorders. The microarray results were confirmed by qPCR, immunoblotting, and immunohistochemistry. CSTA was detected at high level throughout the newborn mouse epidermis but dramatically decreased with development and was detected predominantly in the differentiated layers. In human keratinocytes, knockdown of Dsg2 by siRNA or shRNA reduced CSTA expression. Furthermore, siRNA knockdown of CSTA resulted in cytoplasmic localization of Dsg2, perturbed cytokeratin 14 staining and reduced levels of desmoplakin in response to mechanical stretching. Both knockdown of either Dsg2 or CSTA induced loss of cell adhesion in a dispase-based assay and the effect was synergistic. Our findings here offer a novel pathway of CSTA regulation involving Dsg2 and a potential crosstalk between Dsg2 and CSTA that modulates cell adhesion. These results further support the recent human genetic findings that loss of function mutations in the CSTA gene result in skin fragility due to impaired cell-cell adhesion: autosomal-recessive exfoliative ichthyosis or acral peeling skin syndrome.

Discovery in genetic skin disease: the impact of high throughput genetic technologies

The last decade has seen considerable advances in our understanding of the genetic basis of skin disease, as a consequence of high throughput sequencing technologies including next generation sequencing and whole exome sequencing. We have now determined the genes underlying several monogenic diseases, such as harlequin ichthyosis, Olmsted syndrome, and exfoliative ichthyosis, which have provided unique insights into the structure and function of the skin. In addition, through genome wide association studies we now have an understanding of how low penetrance variants contribute to inflammatory skin diseases such as psoriasis vulgaris and atopic dermatitis, and how they contribute to underlying pathophysiological disease processes. In this review we discuss strategies used to unravel the genes underlying both monogenic and complex trait skin diseases in the last 10 years and the implications on mechanistic studies, diagnostics, and therapeutics.

Microenvironmental Influences on Metastasis Suppressor Expression and Function during a Metastatic Cell's Journey

Metastasis is the process of primary tumor cells breaking away and colonizing distant secondary sites. In order for a tumor cell growing in one microenvironment to travel to, and flourish in, a secondary environment, it must survive a series of events termed the metastatic cascade. Before departing the primary tumor, cells acquire genetic and epigenetic changes that endow them with properties not usually associated with related normal differentiated cells. Those cells also induce a subset of bone marrow-derived stem cells to mobilize and establish pre-metastatic niches [1]. Many tumor cells undergo epithelial-to-mesenchymal transition (EMT), where they transiently acquire morphologic changes, reduced requirements for cell-cell contact and become more invasive [2]. Invasive tumor cells eventually enter the circulatory (hematogenous) or lymphatic systems or travel across body cavities. In transit, tumor cells must resist anoikis, survive sheer forces and evade detection by the immune system. For blood-borne metastases, surviving cells then arrest or adhere to endothelial linings before either proliferating or extravasating. Eventually, tumor cells complete the process by proliferating to form a macroscopic mass [3].Up to 90 % of all cancer related morbidity and mortality can be attributed to metastasis. Surgery manages to ablate most primary tumors, especially when combined with chemotherapy and radiation. But if cells have disseminated, survival rates drop precipitously. While multiple parameters of the primary tumor are predictive of local or distant relapse, biopsies remain an imperfect science. The introduction of molecular and other biomarkers [4, 5] continue to improve the accuracy of prognosis. However, the invasive procedure introduces new complications for the patient. Likewise, the heterogeneity of any tumor population [3, 6, 7] means that sampling error (i.e., since it is impractical to examine the entire tumor) necessitates further improvements.In the case of breast cancer, for example, women diagnosed with stage I diseases (i.e., no evidence of invasion through a basement membrane) still have a ~30 % likelihood of developing distant metastases [8]. Many physicians and patients opt for additional chemotherapy in order to "mop up" cells that have disseminated and have the potential to grow into macroscopic metastases. This means that ~ 70 % of patients receive unnecessary therapy, which has undesirable side effects. Therefore, improving prognostic capability is highly desirable.Recent advances allow profiling of primary tumor DNA sequences and gene expression patterns to define a so-called metastatic signature [9-11], which can be predictive of patient outcome. However, the genetic changes that a tumor cell must undergo to survive the initial events of the metastatic cascade and colonize a second location belie a plasticity that may not be adequately captured in a sampling of heterogeneous tumors. In order to tailor or personalize patient treatments, a more accurate assessment of the genetic profile in the metastases is needed. Biopsy of each individual metastasis is not practical, safe, nor particularly cost-effective. In recent years, there has been a resurrection of the notion to do a 'liquid biopsy,' which essentially involves sampling of circulating tumor cells (CTC) and/or cell free nucleic acids (cfDNA, including microRNA (miRNA)) present in blood and lymph [12-16].The rationale for liquid biopsy is that tumors shed cells and/or genetic fragments into the circulation, theoretically making the blood representative of not only the primary tumor but also distant metastases. Logically, one would predict that the proportion of CTC and/or cfDNA would be proportionate to the likelihood of developing metastases [14]. While a linear relationship does not exist, the information within CTC or cfDNA is beginning to show great promise for enabling a global snapshot of the disease. However, the CTC and cfDNA are present at extremely low levels. Nonetheless, newer technologies capture enough material to enrich and sequence the patient's DNA or quantification of some biomarkers.Among the biomarkers showing great promise are metastasis suppressors which, by definition, block a tumor cell's ability to complete the metastatic process without prohibiting primary tumor growth [17]. Since the discovery of the first metastasis suppressor, Nm23, more than 30 have been functionally characterized. They function at various stages of the metastatic cascade, but their mechanisms of action, for the most part, remain ill-defined. Deciphering the molecular interactions of functional metastasis suppressors may provide insights for targeted therapies when these regulators cease to function and result in metastatic disease.In this brief review, we summarize what is known about the various metastasis suppressors and their functions at individual steps of the metastatic cascade (Table 1). Some of the subdivisions are rather arbitrary in nature, since many metastasis suppressors affect more than one step in the metastatic cascade. Nonetheless what emerges is a realization that metastasis suppressors are intimately associated with the microenvironments in which cancer cells find themselves [18].

Metastasis suppressors in breast cancers: mechanistic insights and clinical potential

For the most part, normal epithelial cells do not disseminate to other parts of the body and proliferate, as do metastatic cells. Presumably, a class of molecules-termed metastasis suppressors-are involved in this homeostatic control. Metastasis suppressors are, by definition, cellular factors that, when re-expressed in metastatic cells, functionally inhibit metastasis without significantly inhibiting tumor growth. In this brief review, we catalog known metastasis suppressors, what is known about their mechanism(s) of action, and experimental and clinical associations to date.

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.

The regulation of cysteine cathepsins and cystatins in human gliomas

Cysteine cathepsins play an important role in shaping the highly infiltrative growth pattern of human gliomas. We have previously demonstrated that the activity of cysteine cathepsins is elevated in invasive glioblastoma (GBM) cells in vitro, in part due to attenuation of their endogenous inhibitors, the cystatins. To investigate this relationship in vivo, we established U87-MG xenografts in non-obese diabetic (NOD)/severe combined immunodeficiency (SCID)-enhanced green fluorescent protein (eGFP) mice. Here, tumor growth correlated with an elevated enzymatic activity of CatB both in the tumor core and at the periphery, whereas CatS and CatL levels were higher at the xenograft edge compared to the core. Reversely, StefB expression was detected in the tumor core, but it was generally absent in the tumor periphery, suggesting that down-regulation of this inhibitor correlates with in vivo invasion. In human GBM samples, all cathepsins were elevated at the tumor periphery compared to brain parenchyma. CatB was also typically associated with angiogenic endothelia and necrotic areas. StefB was mainly detected in the tumor core, whereas CysC and StefA were evenly distributed, reflecting the observations in the xenografts. However, at the mRNA level, no differences in cathepsins and cystatins were observed between the tumor center and the periphery in both human biopsies and xenografts. Interestingly, in human tumors, cathepsin and stefin transcript levels correlated with CD68 and CXCR4 levels, but not with epidermal growth factor receptor (EGFR). Moreover, we reveal for the first time that an elevated StefA mRNA level is a highly significant prognostic factor for patient survival.

Silencing of Irf7 pathways in breast cancer cells promotes bone metastasis through immune escape

Breast cancer metastasis is a key determinant of long-term patient survival. By comparing the transcriptomes of primary and metastatic tumor cells in a mouse model of spontaneous bone metastasis, we found that a substantial number of genes suppressed in bone metastases are targets of the interferon regulatory factor Irf7. Restoration of Irf7 in tumor cells or administration of interferon led to reduced bone metastases and prolonged survival time. In mice deficient in the interferon (IFN) receptor or in natural killer (NK) and CD8(+) T cell responses, metastasis was accelerated, indicating that Irf7-driven suppression of metastasis was reliant on IFN signaling to host immune cells. We confirmed the clinical relevance of these findings in over 800 patients in which high expression of Irf7-regulated genes in primary tumors was associated with prolonged bone metastasis-free survival. This gene signature may identify patients that could benefit from IFN-based therapies. Thus, we have identified an innate immune pathway intrinsic to breast cancer cells, the suppression of which restricts immunosurveillance to enable metastasis.

Strategies for the discovery and development of therapies for metastatic breast cancer

Nearly all deaths caused by solid cancers occur as a result of metastasis--the formation of secondary tumours in distant organs such as the lungs, liver, brain and bone. A major obstruction to the development of drugs with anti-metastatic efficacy is our fragmented understanding of how tumours 'evolve' and metastasize, at both the biological and genetic levels. Furthermore, although there is significant overlap in the metastatic process among different types of cancer, there are also marked differences in the propensity to metastasize, the extent of metastasis, the sites to which the tumour metastasizes, the kinetics of the process and the mechanisms involved. Here, we consider the case of breast cancer, which has some marked distinguishing features compared with other types of cancer. Considerable progress has been made in the development of preclinical models and in the identification of relevant signalling pathways and genetic regulators of metastatic breast cancer, and we discuss how these might facilitate the development of novel targeted anti-metastatic drugs.

Dual-wavelength imaging of tumor progression by activatable and targeting near-infrared fluorescent probes in a bioluminescent breast cancer model

Bioluminescence imaging (BLI) has shown its appeal as a sensitive technique for in vivo whole body optical imaging. However, the development of injectable tumor-specific near-infrared fluorescent (NIRF) probes makes fluorescence imaging (FLI) a promising alternative to BLI in situations where BLI cannot be used or is unwanted (e.g., spontaneous transgenic tumor models, or syngeneic mice to study immune effects).

In this study, we addressed the questions whether it is possible to detect tumor progression using FLI with appropriate sensitivity and how FLI correlates with BLI measurements. In addition, we explored the possibility to simultaneously detect multiple tumor characteristics by dual-wavelength FLI (∼700 and ∼800 nm) in combination with spectral unmixing. Using a luciferase-expressing 4T1-luc2 mouse breast cancer model and combinations of activatable and targeting NIRF probes, we showed that the activatable NIRF probes (ProSense680 and MMPSense680) and the targeting NIRF probes (IRDye 800CW 2-DG and IRDye 800CW EGF) were either activated by or bound to 4T1-luc2 cells. In vivo, we implanted 4T1-luc2 cells orthotopically in nude mice and were able to follow tumor progression longitudinally both by BLI and dual-wavelength FLI. We were able to reveal different probe signals within the tumor, which co-localized with immuno-staining. Moreover, we observed a linear correlation between the internal BLI signals and the FLI signals obtained from the NIRF probes. Finally, we could detect pulmonary metastases both by BLI and FLI and confirmed their presence histologically.

Taken together, these data suggest that dual-wavelength FLI is a feasible approach to simultaneously detect different features of one tumor and to follow tumor progression with appropriate specificity and sensitivity. This study may open up new perspectives for the detection of tumors and metastases in various experimental models and could also have clinical applications, such as image-guided surgery.

Cathepsin B inhibition limits bone metastasis in breast cancer

Metastasis to bone is a major cause of morbidity in breast cancer patients, emphasizing the importance of identifying molecular drivers of bone metastasis for new therapeutic targets. The endogenous cysteine cathepsin inhibitor stefin A is a suppressor of breast cancer metastasis to bone that is coexpressed with cathepsin B in bone metastases. In this study, we used the immunocompetent 4T1.2 model of breast cancer which exhibits spontaneous bone metastasis to evaluate the function and therapeutic targeting potential of cathepsin B in this setting of advanced disease. Cathepsin B abundancy in the model mimicked human disease, both at the level of primary tumors and matched spinal metastases. RNA interference-mediated knockdown of cathepsin B in tumor cells reduced collagen I degradation in vitro and bone metastasis in vivo. Similarly, intraperitoneal administration of the highly selective cathepsin B inhibitor CA-074 reduced metastasis in tumor-bearing animals, a reduction that was not reproduced by the broad spectrum cysteine cathepsin inhibitor JPM-OEt. Notably, metastasis suppression by CA-074 was maintained in a late treatment setting, pointing to a role in metastatic outgrowth. Together, our findings established a prometastatic role for cathepsin B in distant metastasis and illustrated the therapeutic benefits of its selective inhibition in vivo.

Cathepsin B inhibition limits bone metastasis in breast cancer

Metastasis to bone is a major cause of morbidity in breast cancer patients, emphasizing the importance of identifying molecular drivers of bone metastasis for new therapeutic targets. The endogenous cysteine cathepsin inhibitor stefin A is a suppressor of breast cancer metastasis to bone that is coexpressed with cathepsin B in bone metastases. In this study, we used the immunocompetent 4T1.2 model of breast cancer which exhibits spontaneous bone metastasis to evaluate the function and therapeutic targeting potential of cathepsin B in this setting of advanced disease. Cathepsin B abundancy in the model mimicked human disease, both at the level of primary tumors and matched spinal metastases. RNA interference-mediated knockdown of cathepsin B in tumor cells reduced collagen I degradation in vitro and bone metastasis in vivo. Similarly, intraperitoneal administration of the highly selective cathepsin B inhibitor CA-074 reduced metastasis in tumor-bearing animals, a reduction that was not reproduced by the broad spectrum cysteine cathepsin inhibitor JPM-OEt. Notably, metastasis suppression by CA-074 was maintained in a late treatment setting, pointing to a role in metastatic outgrowth. Together, our findings established a prometastatic role for cathepsin B in distant metastasis and illustrated the therapeutic benefits of its selective inhibition in vivo.

Activation of the aryl hydrocarbon receptor by TCDD inhibits mammary tumor metastasis in a syngeneic mouse model of breast cancer

Treatment with aryl hydrocarbon receptor (AhR) agonists can slow or reverse the growth of primary mammary tumors in rodents, which has fostered interest in developing selective AhR modulators for treatment of breast cancer. However, the major goal of breast cancer therapy is to inhibit metastasis, the primary cause of mortality in women with this disease. Studies conducted using breast cancer cell lines have demonstrated that AhR agonists suppress proliferation, invasiveness, and colony formation in vitro; however, further exploration using in vivo models of metastasis is warranted. To test the effect of AhR activation on metastasis, 4T1.2 mammary tumor cells were injected into the mammary gland fat pad of syngeneic Balb/c mice treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Primary tumor growth was monitored for 4 weeks, at which time metastasis was determined. TCDD treatment suppressed metastasis by approximately 50%, as measured both in the lung and in mammary glands at sites distant from the primary tumor. Primary tumor growth was not suppressed by TCDD exposure nor was proliferation of 4T1.2 cells affected by TCDD treatment in vitro. Taken together, these results suggest that the protective effect of AhR activation was selective for the metastatic process and not simply the result of a direct decrease in tumor cell proliferation or survival at the primary site. These observations in immunologically intact animals warrant further investigation into the mechanism of the protective effects of AhR activation and support the promise for use of AhR modulators to treat breast cancer.

Molecular network pathways and functional analysis of tumor signatures associated with development of resistance to viral gene therapy

Replication-competent attenuated herpes simplex viruses have proven effective in killing many cancer cell lines. However, determinants of resistance to oncolytic therapy are mostly unknown. We developed viral therapy-resistant cells and examined changes in gene-expression pattern compared with therapy-sensitive parental cells. Colon cancer cell line HT29 and hepatoma cell line PLC5 were exposed to increasing concentrations of virus G207. Therapy-resistant cells were isolated and grown in vitro. Tumorigenicity was confirmed by ability of cell lines to form tumors in mice. Human Genome U133A complementary DNA microarray chips were used to determine gene-expression patterns, which were analyzed in the context of molecular network interactions, pathways and gene ontology. In parental cell lines, 90-100% of cells were killed by day 7 at 1.0 multiplicity of infection. In resistant cell lines, cytotoxicity assay confirmed 200- to 400-fold resistance. Microarray analysis confirmed changes in gene expressions associated with resistance: cell surface proteins affecting viral attachment and entry, cellular proteins affecting nucleotide pools and proteins altering apoptotic pathways. These changes would decrease viral infection and replication. Our study identifies gene-expression signatures associated with resistance to oncolytic viral therapy. These data provide potential targets to overcome resistance, and suggest that molecular assays may be useful in selecting patients for trial with this novel treatment.

Overexpression of cathepsin Z contributes to tumor metastasis by inducing epithelial-mesenchymal transition in hepatocellular carcinoma

The aim of this study was to characterize the oncogenic function and mechanism of Cathepsin Z (CTSZ) at 20q13.3, a frequently amplified region in hepatocellular carcinoma (HCC). Real-time PCR were used to compare CTSZ expression between paired HCC tumor and non-tumor specimens. CTSZ gene was stably transfected into HCC line QGY-7703 cells and its role in tumorigenicity and cell motility was characterized by soft agar, wound-healing, transwell invasion and cell adhesion assay, and tumor xenograft mouse model. Western blot analysis was used to study expression of proteins associated with epithelial-mesenchymal transition (EMT).Upregulation of CTSZ was detected in 59/137 (43%) of primary HCCs, which was significantly associated with advanced clinical stage (P = 0.000). Functional study found that CTSZ could increase colony formation in soft agar and promote cell motility. Further study found that the metastatic effect of CTSZ was associated with its role in inducing epithelial-mesenchymal transition (EMT) by upregulating mesenchymal markers (fibronectin and vimentin) and downregulating epithelial markers (E-cadherin and α-catenin). In addition, CTSZ could also upregulate proteins associated with extracellular matrix remodeling such as MMP2, MMP3 and MMP9. Taken together, our data suggested that CTSZ was a candidate oncogene within the 20q13 amplicon and it played an important role in HCC metastasis.

Multi-conformation 3D QSAR study of benzenesulfonyl-pyrazol-ester compounds and their analogs as cathepsin B inhibitors

Cathepsin B has been found being responsible for many human diseases. Inhibitors of cathepsin B, a ubiquitous lysosomal cysteine protease, have been developed as a promising treatment for human diseases resulting from malfunction and over-expression of this enzyme. Through a high throughput screening assay, a set of compounds were found able to inhibit the enzymatic activity of cathepsin B. The binding structures of these active compounds were modeled through docking simulation. Three-dimensional (3D) quantitative structure-activity relationship (QSAR) models were constructed using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) based on the docked structures of the compounds. Strong correlations were obtained for both CoMFA and CoMSIA models with cross-validated correlation coefficients (q²) of 0.605 and 0.605 and the regression correlation coefficients (r²) of 0.999 and 0.997, respectively. The robustness of these models was further validated using leave-one-out (LOO) method and training-test set method. The activities of eight (8) randomly selected compounds were predicted using models built from training set of compounds with prediction errors of less than 1 unit for most compounds in CoMFA and CoMSIA models. Structural features for compounds with improved activity are suggested based on the analysis of the CoMFA and CoMSIA contour maps and the property map of the protein ligand binding site. These results may help to provide better understanding of the structure-activity relationship of cathepsin B inhibitors and to facilitate lead optimization and novel inhibitor design. The multi-conformation method to build 3D QSAR is very effective approach to obtain satisfactory models with high correlation with experimental results and high prediction power for unknown compounds.

Identification of cystatin SA as a novel inhibitor of acid ceramidase

Autoproteolytic cleavage of the inactive acid ceramidase (AC) precursor into the active heterodimer exposes a free cysteine residue, leading us to study whether AC could be regulated by one or more members of the cystatin family. Co-expression of the full-length AC and cystatin SA (cysSA) cDNAs led to significant reduction of AC activity in the transfected cells. Expression of cysSA also inhibited endogenous AC activity in cells and increased ceramide. Conversely, cysSA siRNA expression led to elevated AC activity and reduction in ceramide. The effects of cysSA siRNA expression could be reversed by the addition of recombinant cysSA into the culture media. These results were consistent with detection of a physical interaction between AC and cysSA, assessed by co-immunoprecipitation and nickel-nitrilotriacetic acid affinity chromatography, and further supported by co-localization of the endogenous proteins using confocal microscopy. In vitro kinetic analysis of purified, recombinant AC and cysSA confirmed the transfection results and suggested a non-competitive type of inhibition with a K(i) in the low micromolar range. Processing of the AC precursor into the active form was not affected by cysSA expression, suggesting that it likely inhibits AC by allosteric interference. Computer modeling and expression studies identified several potential inhibitory domains in cysSA, including a small "AC-like" domain (identical to the AC cleavage site, TICT). Small peptides, synthesized with combinations of this and a "cystatin-like" domain (QXVXG), exhibited significant AC inhibition as well. Such peptide-based AC inhibitors could potentially be used to regulate AC activity in cancer cells that are known to overexpress this enzyme alone and in combination with conventional anti-cancer drugs.

Identification of a myeloid-derived suppressor cell cystatin-like protein that inhibits metastasis

Myeloid-derived suppressor cells (MDSCs) are significantly increased in cancer patients and tumor bearing-animals. MDSCs infiltrate into tumors and promote tumor invasion and metastasis. To identify the mediator responsible for the prometastatic property of MDSCs, we used proteomics. We found neutrophilic granule protein (NGP) was decreased >2-fold in MDSCs from metastatic 4T1 tumor-bearing mice compared to nonmetastatic 67NR controls. NGP mRNA levels were decreased in bone marrow and in tumor-infiltrating MDSCs by 45 and 66%, respectively, in 4T1 tumor-bearing mice compared to 67NR controls. Interestingly, 4T1-conditioned medium reduced myeloid cell NGP expression by ∼ 40%, suggesting that a secreted factor mediates gene reduction. Sequence analysis shows a putative cystatin domain in NGP, and biochemical analysis confirms NGP a novel cathepsin inhibitor. It inhibited cathepsin B activity by nearly 40% in vitro. NGP expression in 4T1 tumor cells suppressed cell invasion, delayed primary tumor growth, and greatly reduced lung metastasis in vivo. A 2.8-fold reduction of cathepsin activity was found in tumors expressing NGP compared to controls. NGP significantly reduced tumor angiogenesis to 12.6 from 19.6 and lymphangiogenesis to 4.6 from 9.1 vessels/field. Necrosis was detectable only in NGP-expressing tumors, and the number of apoptotic cells increased to 22.4 from 8.3 in controls. Taken together, this study identifies a negative regulator of tumor metastasis in MDSCs, NGP, which is down-regulated in metastatic conditions. The finding suggests that malignant tumors promote invasion/metastasis not only through up-regulation of proteases but also down-regulation of protease inhibitors.

[Identification of salivary biomarkers in breast cancer patients with thick white or thick yellow tongue fur using isobaric tags for relative and absolute quantitative proteomics]

OBJECTIVE

To explore the presence of informative protein biomarkers in the salivary proteome of breast cancer patients with thick white or thick yellow tongue fur.

METHODS

Salivia samples were collected from 20 breast cancer patients with thick white or yellow tongue fur and 10 healthy controls. The samples were profiled by using isobaric tags for relative and absolute quantitation (iTRAQ) technology coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). The analyzed map and data were assessed with Mascott 2.2 and Scaffold software. Ratio of proteins between groups of less than 0.6 or more than 1.5 could confirm that there was difference between groups.

RESULTS

A total of 464 proteins were identified and 125 proteins met strict quantitative criteria. There were 9 proteins associated with breast cancer, expression levels of which were up- or down-regulated more than 1.5 folds compared with healthy people. There were 16 proteins associated with tongue coating, of which 10 proteins expressed in breast cancer patients with thick white fur were lower than in patients with thick yellow fur, and the expressions of the other 6 proteins were increased.

CONCLUSION

This study demonstrates that iTRAQ combined with LC-MS/MS quantitative proteomics is a powerful tool for biomarker discovery and the identification of proteins associated with breast cancer and tongue coating.

Modulation of cystatin A expression in human airway epithelium related to genotype, smoking, COPD, and lung cancer

The cathepsin inhibitor Cystatin A (CSTA) has antiapoptotic properties linked with neoplastic changes in squamous cell epithelium, where it has been proposed as a diagnostic and prognostic marker of lung cancer. Notably, cystatin A is upregulated in dysplastic epithelium, prompting us to hypothesize that it might be modulated in chronic obstructive pulmonary disease (COPD), a small airway epithelial (SAE) disorder that is a risk factor for non-small cell lung cancer (NSCLC) in a subset of smokers. Here we report that genetic variation, smoking, and COPD can all elevate levels of CSTA expression in lung small airway epithelia, with still further upregulation in squamous cell carcinoma (SCC), an NSCLC subtype. We examined SAE gene expression in 178 individuals, including healthy nonsmokers (n = 60), healthy smokers (n = 82), and COPD smokers (n = 36), with corresponding large airway epithelium (LAE) data included in a subset of subjects (n = 52). Blood DNA was genotyped by SNP microarray. Twelve SNPs upstream of the CSTA gene were found to associate with its expression in SAE. Levels were higher in COPD smokers than in healthy smokers, who, in turn, had higher levels than nonsmokers. CSTA gene expression in LAE was also smoking-responsive. Using publicly available NSCLC expression data we also found that CSTA was upregulated in SCC versus LAE and downregulated in adenocarcinoma versus smoke-exposed SAE. All phenotypes were associated with different proportional expression of CSTA to cathepsins. Our findings establish that genetic variability, smoking, and COPD all influence CSTA expression, as does SCC, supporting the concept that CSTA may make pivotal contributions to NSCLC pathogenesis in both early and late stages of disease development.

Image-guided tumor resection using real-time near-infrared fluorescence in a syngeneic rat model of primary breast cancer

Tumor involvement of resection margins is found in a large proportion of patients who undergo breast-conserving surgery. Near-infrared (NIR) fluorescence imaging is an experimental technique to visualize cancer cells during surgery. To determine the accuracy of real-time NIR fluorescence imaging in obtaining tumor-free resection margins, a protease-activatable NIR fluorescence probe and an intraoperative camera system were used in the EMR86 orthotopic syngeneic breast cancer rat model. Influence of concentration, timing and number of tumor cells were tested in the MCR86 rat breast cancer cell line. These variables were significantly associated with NIR fluorescence probe activation. Dosing and tumor size were also significantly associated with fluorescence intensity in the EMR86 rat model, whereas time of imaging was not. Real-time NIR fluorescence guidance of tumor resection resulted in a complete resection of 17 out of 17 tumors with minimal excision of normal healthy tissue (mean minimum and a mean maximum tumor-free margin of 0.2 ± 0.2 mm and 1.3 ± 0.6 mm, respectively). Moreover, the technique enabled identification of remnant tumor tissue in the surgical cavity. Histological analysis revealed that the NIR fluorescence signal was highest at the invasive tumor border and in the stromal compartment of the tumor. In conclusion, NIR fluorescence detection of breast tumor margins was successful in a rat model. This study suggests that clinical introduction of intraoperative NIR fluorescence imaging has the potential to increase the number of complete tumor resections in breast cancer patients undergoing breast-conserving surgery.

QSAR models for predicting cathepsin B inhibition by small molecules--continuous and binary QSAR models to classify cathepsin B inhibition activities of small molecules

Cathepsin B is a potential target for the development of drugs to treat several important human diseases. A number of inhibitors targeting this protein have been developed in the past several years. Recently, a group of small molecules were identified to have inhibitory activity against cathepsin B through high throughput screening (HTS) tests. In this study, traditional continuous and binary QSAR models were built to classify the biological activities of previously identified compounds and to distinguish active compounds from inactive compounds for drug development based on the calculated molecular and physicochemical properties. Strong correlations were obtained for the continuous QSAR models with regression correlation coefficients (r²) and cross-validated correlation coefficients (q²) of 0.77 and 0.61 for all compounds, and 0.82 and 0.68 for the compound set excluding 3 outliers, respectively. The models were further validated through the leave-one-out (LOO) method and the training-test set method. The binary models demonstrated a strong level of predictability in distinguishing the active compounds from inactive compounds with accuracies of 0.89 and 0.94 for active and inactive compounds, respectively, in non-cross-validated models. Similar results were obtained for the cross-validated models. Collectively, these results demonstrate the models’ ability to discriminate between active and inactive compounds, suggesting that the models may be used to pre-screen compounds to facilitate compound optimization and to design novel inhibitors for drug development.

Computational analysis of the cathepsin B inhibitors activities through LR-MMPBSA binding affinity calculation based on docked complex

Cathepsin B, a ubiquitous lysosomal cysteine protease, is involved in many biological processes related to several human diseases. Inhibitors targeting the enzyme have been investigated as possible diseases treatments. A set of 37 compounds were recently found active in a high throughput screening assay to inhibit the catalytic activity of Cathepsin B, with chemical structures and biological test results available to the public in the PubChem BioAssay Database (AID 820). In this study, we compare these experimental activities to the results of theoretical predictions from binding affinity calculation with a LR-MM-PNSA approach based on docked complexes. Strong correlations (r(2) = 0.919 and q(2) = 0.887 for the best) are observed between the theoretical predictions and experimental biological activity. The models are cross-validated by four independent predictive experiments with randomly split compounds into training and test sets. Our results also show that the results based on protein dimer show better correlations with experimental activity when compared to results based on monomer in the in silico calculations.

Analysis of blood stem cell activity and cystatin gene expression in a mouse model presenting a chromosomal deletion encompassing Csta and Stfa2l1

The cystatin protein superfamily is characterized by the presence of conserved sequences that display cysteine protease inhibitory activity (e.g., towards cathepsins). Type 1 and 2 cystatins are encoded by 25 genes of which 23 are grouped in 2 clusters localized on mouse chromosomes 16 and 2. The expression and essential roles of most of these genes in mouse development and hematopoiesis remain poorly characterized. In this study, we describe a set of quantitative real-time PCR assays and a global expression profile of cystatin genes in normal mouse tissues. Benefiting from our collection of DelES embryonic stem cell clones harboring large chromosomal deletions (to be reported elsewhere), we selected a clone in which a 95-kb region of chromosome 16 is missing (Del^16qB3Δ/+). In this particular clone, 2 cystatin genes, namely Csta and Stfa2l1 are absent along with 2 other genes (Fam162a, Ccdc58) and associated intergenic regions. From this line, we established a new homozygous mutant mouse model (Del^{16qB3Δ/16qB3Δ}) to assess the in vivo biological functions of the 2 deleted cystatins. Stfa2l1 gene expression is high in wild-type fetal liver, bone marrow, and spleen, while Csta is ubiquitously expressed. Homozygous Del^{16qB3Δ/16qB3Δ} animals are phenotypically normal, fertile, and not overtly susceptible to spontaneous or irradiation-induced tumor formation. The hematopoietic stem and progenitor cell activity in these mutant mice are also normal. Interestingly, quantitative real-time PCR expression profiling reveals a marked increase in the expression levels of Stfa2l1/Csta phylogenetically-related genes (Stfa1, Stfa2, and Stfa3) in Del^{16qB3Δ/16qB3Δ} hematopoietic tissues, suggesting that these candidate genes might be contributing to compensatory mechanisms. Overall, this study presents an optimized approach to globally monitor cystatin gene expression as well as a new mouse model deficient in Stfa2l1/Csta genes, expanding the available tools to dissect cystatin roles under normal and pathological conditions.

The role of cathepsins in involution and breast cancer

Cysteine cathepsins are proteolytic enzymes that reside in endolysosomal vesicles. Some are expressed constitutively while others are transcriptionally regulated. However, the expression and subcellular localization of cathepsins changes during cancer progression and cathepsins have been shown to be causally involved in various aspects of tumorigenesis including metastasis. The use of mouse models of breast cancer genetically ablated for cathepsin B has shown that both the growth of the primary tumor and the extend of lung metastasis is reduced by the loss of cathepsin B. The role of cathepsins in involution of the mammary gland has received little attention although it is clear that cathepsins are involved in tissue remodeling in the second phase of involution. We discuss here the roles of cathepsins and their endogenous inhibitors in breast tumorigenesis and post-lactational involution.