Lysosomal enzymes, cathepsins in brain tumour invasion

Lysosomes in Cancer-At the Crossroad of Good and Evil

Although it has been known for decades that lysosomes are central for degradation and recycling in the cell, their pivotal role as nutrient sensing signaling hubs has recently become of central interest. Since lysosomes are highly dynamic and in constant change regarding content and intracellular position, fusion/fission events allow communication between organelles in the cell, as well as cell-to-cell communication via exocytosis of lysosomal content and release of extracellular vesicles. Lysosomes also mediate different forms of regulated cell death by permeabilization of the lysosomal membrane and release of their content to the cytosol. In cancer cells, lysosomal biogenesis and autophagy are increased to support the increased metabolism and allow growth even under nutrient- and oxygen-poor conditions. Tumor cells also induce exocytosis of lysosomal content to the extracellular space to promote invasion and metastasis. However, due to the enhanced lysosomal function, cancer cells are often more susceptible to lysosomal membrane permeabilization, providing an alternative strategy to induce cell death. This review summarizes the current knowledge of cancer-associated alterations in lysosomal structure and function and illustrates how lysosomal exocytosis and release of extracellular vesicles affect disease progression. We focus on functional differences depending on lysosomal localization and the regulation of intracellular transport, and lastly provide insight how new therapeutic strategies can exploit the power of the lysosome and improve cancer treatment.

Molecular signature of stem-like glioma cells (SLGCs) from human glioblastoma and gliosarcoma

Glioblastoma multiforme (GBM) and the GBM variant gliosarcoma (GS) are among the tumors with the highest morbidity and mortality, providing only palliation. Stem-like glioma cells (SLGCs) are involved in tumor initiation, progression, therapy resistance, and relapse. The identification of general features of SLGCs could contribute to the development of more efficient therapies. Commercially available protein arrays were used to determine the cell surface signature of eight SLGC lines from GBMs, one SLGC line obtained from a xenotransplanted GBM-derived SLGC line, and three SLGC lines from GSs. By means of non-negative matrix factorization expression metaprofiles were calculated. Using the cophenetic correlation coefficient (CCC) five metaprofiles (MPs) were identified, which are characterized by specific combinations of 7-12 factors. Furthermore, the expression of several factors, that are associated with GBM prognosis, GBM subtypes, SLGC differentiation stages, or neural identity was evaluated. The investigation encompassed 24 distinct SLGC lines, four of which were derived from xenotransplanted SLGCs, and included the SLGC lines characterized by the metaprofiles. It turned out that all SLGC lines expressed the epidermal growth factor EGFR and EGFR ligands, often in the presence of additional receptor tyrosine kinases. Moreover, all SLGC lines displayed a neural signature and the IDH1 wildtype, but differed in their p53 and PTEN status. Pearson Correlation analysis identified a positive association between the pluripotency factor Sox2 and the expression of FABP7, Musashi, CD133, GFAP, but not with MGMT or Hif1α. Spherical growth, however, was positively correlated with high levels of Hif1α, CDK4, PTEN, and PDGFRβ, whereas correlations with stemness factors or MGMT (MGMT expression and promoter methylation) were low or missing. Factors highly expressed by all SLGC lines, irrespective of their degree of stemness and growth behavior, are Cathepsin-D, CD99, EMMPRIN/CD147, Intβ1, the Galectins 3 and 3b, and N-Cadherin.

Human C1q Tumor Necrosis Factor 8 (CTRP8) defines a novel tryptase+ mast cell subpopulation in the prostate cancer microenvironment

The adipokine C1q Tumor Necrosis Factor 8 (CTRP8) is the least known member of the 15 CTRP proteins and a ligand of the relaxin receptor RXFP1. We previously demonstrated the ability of the CTRP8-RXFP1 interaction to promote motility, matrix invasion, and drug resistance. The lack of specific tools to detect CTRP8 protein severely limits our knowledge on CTRP8 biological functions in normal and tumor tissues. Here, we have generated and characterized the first specific antiserum to human CTRP8 which identified CTRP8 as a novel marker of tryptase+ mast cells (MC_T) in normal human tissues and in the prostate cancer (PC) microenvironment. Using human PC tissue microarrays composed of neoplastic and corresponding tumor-adjacent prostate tissues, we have identified a significantly higher number of CTRP8+ MC_T in the peritumor versus intratumor compartment of PC tissues of Gleason scores 6 and 7. Higher numbers of CTRP8+ MC_T correlated with the clinical parameter of biochemical recurrence. We showed that the human MC line ROSA^{KIT WT} expressed RXFP1 transcripts and responded to CTRP8 treatment with a small but significant increase in cell proliferation. Like the cognate RXFP1 ligand RLN-2 and the small molecule RXFP1 agonist ML-290, CTRP8 reduced degranulation of ROSA^{KIT WT} MC stimulated by the Ca²⁺-ionophore A14187. In conclusion, this is the first report to identify the RXFP1 agonist CTRP8 as a novel marker of MC_T and autocrine/paracrine oncogenic factor within the PC microenvironment.

Guggulsterone inhibits migration and invasion through proteasomal and lysosomal degradation in human glioblastoma cells

Glioblastoma multiforme (GBM) is a deadly brain malignancy, and current therapies offer limited survival benefit. The phytosterol guggulsterone (GS) has been shown to exhibit antitumor efficacy. This study aimed to investigate the effects of GS on migration and invasion and its underlying mechanisms in human GBM cell lines. After GS treatment, the survival rate of GBM cells was reduced, and the migration and invasion abilities of GBM cells were significantly decreased. There was also concomitant decreased expression of focal adhesion complex, matrix metalloproteinase-2 (MMP2), MMP9 and cathepsin B. Furthermore, GS induced ERK phosphorylation and autophagy, with increased p62 and LC3B-II expression. Notably, treatment of in GBM cells with the proteasome inhibitor MG132 or the lysosome inhibitor NH4Cl reversed the GS-mediated inhibition of migration and invasion. In an orthotopic xenograft mouse model, immunohistochemical staining of brain tumor tissues demonstrated that MMP2 and cathepsin B expression was reduced in GS-treated mice. GS treatment inhibited GBM cell migration and invasion via proteasomal and lysosomal degradation, suggesting its therapeutic potential in clinical use in the future.

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

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

Molecular neuropathology of brain-invasive meningiomas

Invasion of brain tissue by meningiomas has been identified as one key factor for meningioma recurrence. The identification of meningioma tumor tissue surrounded by brain tissue in neurosurgical samples has been touted as a criterion for atypical meningioma (CNS WHO grade 2), but is only rarely seen in the absence of other high-grade features, with brain-invasive otherwise benign (BIOB) meningiomas remaining controversial. While post-surgery irradiation therapy might be initiated in brain-invasive meningiomas to prevent recurrences, specific treatment approaches targeting key molecules involved in the invasive process are not established. Here we have compiled the current knowledge about mechanisms supporting brain tissue invasion by meningiomas and summarize preclinical models studying targeted therapies with potential inhibitory effects.

Upregulation of Cathepsin X in Glioblastoma: Interplay with γ-Enolase and the Effects of Selective Cathepsin X Inhibitors

Glioblastoma (GBM) is the most common and deadly primary brain tumor in adults. Understanding GBM pathobiology and discovering novel therapeutic targets are critical to finding efficient treatments. Upregulation of the lysosomal cysteine carboxypeptidase cathepsin X has been linked to immune dysfunction and neurodegenerative diseases, but its role in cancer and particularly in GBM progression in patients is unknown. In this study, cathepsin X expression and activity were found to be upregulated in human GBM tissues compared to low-grade gliomas and nontumor brain tissues. Cathepsin X was localized in GBM cells as well as in tumor-associated macrophages and microglia. Subsequently, potent irreversible (AMS36) and reversible (Z7) selective cathepsin X inhibitors were tested in vitro. Selective cathepsin X inhibitors decreased the viability of patient-derived GBM cells as well as macrophages and microglia that were cultured in conditioned media of GBM cells. We next examined the expression pattern of neuron-specific enzyme γ-enolase, which is the target of cathepsin X. We found that there was a correlation between high proteolytic activity of cathepsin X and C-terminal cleavage of γ-enolase and that cathepsin X and γ-enolase were colocalized in GBM tissues, preferentially in GBM-associated macrophages and microglia. Taken together, our results on patient-derived material suggest that cathepsin X is involved in GBM progression and is a potential target for therapeutic approaches against GBM.

The effect of spacers in dual drug-polymer conjugates toward combination therapeutic efficacy

Recently, a great effort has been made to perfect the therapeutic effect of solid tumor, from single-agent therapy to combined therapy and many other polymer-drug conjugations with dual or more anticancer agents due to their promising synergistic effect and higher drug level accumulation towards tumor tissues. Different polymer-drug spacers present diverse therapeutic efficacy, therefore, finding an appropriate spacer is desirable. In this study, dual drugs that are doxorubicin (DOX) and mitomycin C (MMC) were conjugated onto a polymer carrier (xyloglucan) via various peptide or amide bonds, and a series of polymers drug conjugates were synthesized with different spacers and their effect on tumor treatment efficacy was studied both in vitro and in vivo. The result shows that the synergistic effect is better when using different linker to conjugate different drugs rather than using the same spacer to conjugate different drugs on the carrier. Particularly, the finding of this works suggested that, using peptide bond for MMC and amide bond for DOX to conjugate dual drugs onto single XG carrier could improve therapeutic effect and synergy effect. Therefore, in polymer-pharmaceutical formulations, the use of different spacers to optimize the design of existing drugs to enhance therapeutic effects is a promising strategy.

Proteases Regulate Cancer Stem Cell Properties and Remodel Their Microenvironment

Proteolytic activity is perturbed in tumors and their microenvironment, and proteases also affect cancer stem cells (CSCs). CSCs are the therapy-resistant subpopulation of cancer cells with tumor-initiating capacity that reside in specialized tumor microenvironment niches. In this review, we briefly summarize the significance of proteases in regulating CSC activities with a focus on brain tumor glioblastoma. A plethora of proteases and their inhibitors participate in CSC invasiveness and affect intercellular interactions, enhancing CSC immune, irradiation, and chemotherapy resilience. Apart from their role in degrading the extracellular matrix enabling CSC migration in and out of their niches, we review the ability of proteases to modulate CSC properties, which prevents their elimination. When designing protease-oriented therapies, the multifaceted roles of proteases should be thoroughly investigated.

The Anti-VEGF(R) Drug Discovery Legacy: Improving Attrition Rates by Breaking the Vicious Cycle of Angiogenesis in Cancer

Resistance to anti-vascular endothelial growth factor (VEGF) molecules causes lack of response and disease recurrence. Acquired resistance develops as a result of genetic/epigenetic changes conferring to the cancer cells a drug resistant phenotype. In addition to tumor cells, tumor endothelial cells also undergo epigenetic modifications involved in resistance to anti-angiogenic therapies. The association of multiple anti-angiogenic molecules or a combination of anti-angiogenic drugs with other treatment regimens have been indicated as alternative therapeutic strategies to overcome resistance to anti-angiogenic therapies. Alternative mechanisms of tumor vasculature, including intussusceptive microvascular growth (IMG), vasculogenic mimicry, and vascular co-option, are involved in resistance to anti-angiogenic therapies. The crosstalk between angiogenesis and immune cells explains the efficacy of combining anti-angiogenic drugs with immune check-point inhibitors. Collectively, in order to increase clinical benefits and overcome resistance to anti-angiogenesis therapies, pan-omics profiling is key.

Brain-invasive meningiomas: molecular mechanisms and potential therapeutic options

Meningiomas are the most commonly diagnosed benign intracranial adult tumors. Subsets of meningiomas that present with extensive invasion into surrounding brain areas have high recurrence rates, resulting in difficulties for complete resection, substantially increased mortality of patients, and are therapeutically challenging for neurosurgeons. Exciting new data have provided insights into the understanding of the molecular machinery of invasion. Moreover, clinical trials for several novel approaches have been launched. Here, we will highlight the mechanisms which govern brain invasion and new promising therapeutic approaches for brain-invasive meningiomas, including pharmacological approaches targeting three major aspects of tumor cell invasion: extracellular matrix degradation, cell adhesion, and growth factors, as well as other innovative treatments such as immunotherapy, hormone therapy, Tumor Treating Fields, and biodegradable copolymers (wafers), impregnated chemotherapy. Those ongoing studies can offer more diversified possibilities of potential treatments for brain-invasive meningiomas, and help to increase the survival benefits for patients.

Upregulation of Cathepsins in Olfactory Bulbs Is Associated with Transient Olfactory Dysfunction in Mice with Experimental Autoimmune Encephalomyelitis

Cathepsins are a family of lysosomal/endosomal proteolytic enzymes that include serine, aspartate, and cysteine proteases. The role of cathepsin in neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease, remains elusive. We evaluated the expression level and localization of different cathepsins in the olfactory bulbs of mice with experimental autoimmune encephalomyelitis (EAE), a model of human multiple sclerosis. Quantitative real-time PCR results and Western blotting analyses revealed that serine, aspartate, and cysteine cathepsins are expressed at significantly higher levels in the olfactory bulbs of mice with EAE in the paralytic stage compared with those of control mice. Immunohistochemical analyses indicated that cathepsin A, D, and S were expressed in the glomerulus layer, external plexiform layer, and mitral cell layer. Furthermore, cathepsins were detected in astrocytes, microglia, inflammatory cells, and vascular cells in the olfactory bulb of EAE mice at the paralytic stage. Collectively, these results suggest that the upregulation of cathepsins in the olfactory bulb of mice with EAE is associated with transient olfactory dysfunction in autoimmune encephalomyelitis.

Quantitative proteomic analysis of down syndrome biomarkers in maternal serum using isobaric tags for relative and absolute quantification (iTRAQ)

Prenatal diagnosis of Down syndrome (DS) is based on calculated risk involving maternal age, biochemical and ultrasonographic markers, and, more recently, cell-free DNA (cfDNA). The present study was designed to identify Down Syndrome biomarkers in maternal serum. We quantified the changes in maternal serum protein levels between 10 non-pregnant women, 10 pregnant women with healthy fetuses, and 10 pregnant women with DS fetuses using isobaric tags for relative and absolute quantification (iTRAQ). We subsequently conducted a Gene Ontology (GO) analysis. A total of 470 proteins were identified, 11 of which had significantly different serum levels between the DS fetus group and Healthy fetuses group. Our data shows the identified proteins may be relevant to DS and constitute potential DS biomarkers.

Immunoreactivity of cytotoxic T-lymphocyte antigen 2 alpha in mouse pancreatic islet cells

Cells of the pancreatic islets produce several molecules including insulin (beta cells), glucagon (alpha cells), somatostatin (delta cells), pancreatic polypeptide (PP cells), ghrelin (epsilon cells), serotonin (enterochromaffin cells), gastrin (G cells) and small granules of unknown content secreted by the P/D1 cells. Secretion mechanism of some of these molecules is still poorly understood. However, Cathepsin L is shown to regulate insulin exocytosis in beta cells and activate the trypsinogen produced by the pancreatic serous acini cells into trypsin. The structure of the propeptide region of Cathepsin L is homologous to Cytotoxic T-lymphocyte antigen-2 alpha (CTLA-2 alpha) which is also shown to exhibit selective inhibitory activities against Cathepsin L. It was thought that if CTLA-2 alpha was expressed in the pancreas; then, it would be an important regulator of protease activation and insulin secretion. The purpose of this study was, therefore, to examine by immunohistochemistry the cellular localization and distribution pattern of CTLA-2 alpha in the pancreas. Results showed that strong immunoreactivity was specifically detected in the pancreatic islets (endocrine pancreas) but not in the exocrine pancreas and pancreatic stroma. Immunostaining was further performed to investigate more on localization of Cathepsin L in the pancreas. Strong immunoreactivity for Cathepsin L was detected in the pancreatic islets, serous cells and the pancreas duct system. These findings suggest that CTLA-2 alpha may be involved in the proteolytic processing and secretion of insulin through regulation of Cathepsin L and that the regulated inhibition of Cathepsin L may have therapeutic potential for type 1 diabetes.

Role of endolysosomes and pH in the pathogenesis and treatment of glioblastoma

BACKGROUND

Glioblastoma multiforme (GBM) is a Grade IV astrocytoma with an aggressive disease course and a uniformly poor prognosis. Pathologically, GBM is characterized by rapid development of primary tumors, diffuse infiltration into the brain parenchyma, and robust angiogenesis. The treatment options that are limited and largely ineffective include a combination of surgical resection, radiotherapy, and chemotherapy with the alkylating agent temozolomide.

RECENT FINDINGS

Similar to many other forms of cancer, the extracellular environment near GBM tumors is acidified. Extracellular acidosis is particularly relevant to tumorgenesis and the concept of tumor cell dormancy because of findings that decreased pH reduces proliferation, increases resistance to apoptosis and autophagy, promotes tumor cell invasion, increases angiogenesis, obscures immune surveillance, and promotes resistance to drug and radio-treatment. Factors known to participate in the acidification process are nutrient starvation, oxidative stress, hypoxia and high levels of anaerobic glycolysis that lead to increases in lactate. Also involved are endosomes and lysosomes (hereafter termed endolysosomes), acidic organelles with highly regulated stores of hydrogen (H+) ions. Endolysosomes contain more than 60 hydrolases as well as about 50 proteins that are known to affect the number, sizes and distribution patterns of these organelles within cells. Recently, vacuolar ATPase (v-ATPase), the main proton pump that is responsible for maintaining the acidic environment in endolysosomes, was identified as a novel therapeutic target for glioblastoma.

CONCLUSIONS

Thus, a greater understanding of the role of endolysosomes in regulating cellular and extracellular acidity could result in a better elucidation of GBM pathogenesis and new therapeutic strategies.

Therapeutic Targeting of Cancer Stem Cells in Human Glioblastoma by Manipulating the Renin-Angiotensin System

Patients with glioblastoma (GB), a highly aggressive brain tumor, have a median survival of 14.6 months following neurosurgical resection and adjuvant chemoradiotherapy. Quiescent GB cancer stem cells (CSCs) invariably cause local recurrence. These GB CSCs can be identified by embryonic stem cell markers, express components of the renin-angiotensin system (RAS) and are associated with circulating CSCs. Despite the presence of circulating CSCs, GB patients rarely develop distant metastasis outside the central nervous system. This paper reviews the current literature on GB growth inhibition in relation to CSCs, circulating CSCs, the RAS and the novel therapeutic approach by repurposing drugs that target the RAS to improve overall symptom-free survival and maintain quality of life.

Kinins in Glioblastoma Microenvironment

Tumour progression involves interactions among various cancer cell clones, including the cancer stem cell subpopulation and exogenous cellular components, termed cancer stromal cells. The latter include a plethora of tumour infiltrating immunocompetent cells, among which are also immuno-modulatory mesenchymal stem cells, which by vigorous migration to growing tumours and susequent transdifferentiation into various types of tumour-residing stromal cells, may either inhibit or support tumour progression. In the light of the scarce therapeutic options existing for the most malignant brain tumour glioblastoma, mesenchymal stem cells may represent a promising novel tool for cell therapy, e.g. drug delivery vectors. Here, we review the increasing number of reports on mutual interactions between mesenchymal stem cells and glioblastoma cells in their microenvironment. We particularly point out two novel aspects: the different responses of cancer cells to their microenvironmental cues, and to the signalling by kinin receptors that complement the immuno-modulating cytokine-signalling networks. Inflammatory glioblastoma microenvironment is characterised by increasing expression of kinin receptors during progressive glioma malignancy, thus making kinin signalling and kinins themselves rather important in this context. In general, their role in tumour microenvironment has not been explored so far. In addition, kinins also regulate blood brain barrier-related drug transfer as well as brain tumour angiogenesis. These studies support the on-going research on kinin antagonists as candidates in the development of anti-invasive agents for adjuvant glioblastoma therapy.

Potential role of cytotoxic T-lymphocyte antigen 2 alpha in secretory activity of endocrine cells in mouse adenohypophysis

The peptide hormones of the adenohypophysis are produced by proteolytic processing of their prohormone precursors. Cathepsin L is known to function as a major proteolytic enzyme involved in the production of the peptide hormones. The structure of the propeptide region of cathepsin L is identical to cytotoxic T-lymphocyte antigen-2 alpha (CTLA-2α) which is also shown to exhibit selective inhibitory activities against cathepsin L. However, the specific cell types synthesizing CTLA-2α in mouse adenohypophysis and its functional implications as relevant in vivo have not been demonstrated. In this study, CTLA-2α expression in the adenohypophysis was evaluated by immunohistochemistry. In both male and female mice, strong immunoreactivity was specifically detected in folliculostellate (FS) cells surrounding endocrine cells which were delineated by CTLA-2α. These findings suggest that the CTLA-2α may be involved in the proteolytic processing and secretion of the hormones in the adenohypophysis through regulation of cathepsin L.

Expression of Cathepsins B, D, and G in WHO Grade I Meningioma

Aim: We have recently demonstrated the presence of putative tumor stem cells (TSCs) in World Health Organization (WHO) grade I meningioma (MG) localized to the microvessels, which expresses components of the renin-angiotensin system (RAS). The RAS is known to be dysregulated and promotes tumorigenesis in many cancer types, including glioblastoma. Cathepsins B, D, and G are isoenzymes that catalyze the production of angiotensin peptides, hence providing bypass loops for the RAS. This study investigated the expression of cathepsins B, D, and G in WHO grade I MG in relation to the putative TSC population we have previously demonstrated. Methods: 3,3-Diaminobenzidine (DAB) immunohistochemical (IHC) staining with antibodies for cathepsins B, D, and G was performed on WHO grade I MG tissue samples from 10 patients. Three of the MG samples subjected to DAB IHC staining underwent immunofluorescence (IF) IHC staining to investigate co-expression of each of these cathepsins using combinations of smooth muscle actin (SMA) and embryonic stem cell marker OCT4. NanoString mRNA expression (n = 6) and Western blotting (WB; n = 5) analyses, and enzyme activity assays (EAAs; n = 3), were performed on snap-frozen WHO grade I MG tissue samples to confirm transcriptional activation, protein expression, and functional activity of these proteins, respectively. Results: DAB IHC staining demonstrated expression of cathepsins B, D, and G in all 10 MG samples. NanoString mRNA expression and WB analyses showed transcriptional activation and protein expression of all three cathepsins, although cathepsin G was expressed at low levels. EAAs demonstrated that cathepsin B and cathepsin D were functionally active. IF IHC staining illustrated localization of cathepsin B and cathepsin D to the endothelium and SMA+ pericyte layer of the microvessels, while cathepsin G was localized to cells scattered within the interstitium, away from the microvessels. Conclusion: Cathepsin B and cathepsin D, and to a lesser extent cathepsin G, are expressed in WHO grade I MG. Cathepsin B and cathepsin D are enzymatically active and are localized to the putative TSC population on the microvessels, whereas cathepsin G was localized to cells scattered within the interstitium, These results suggest the presence of bypass loops for the RAS, within WHO grade I MG.

Identification of CD37, cystatin A, and IL-23A gene expression in association with brain metastasis: analysis of a prospective trial

PURPOSE/OBJECTIVES

We aimed to assess the predictive value of a lung cancer gene panel for the development of brain metastases.

MATERIALS/METHODS

Between 2011 and 2015, 102 patients with lung cancer were prospectively enrolled in a clinical trial in which a diagnostic fine-needle aspirate was obtained. Gene expression was conducted on all samples that rendered a diagnosis of non-small cell lung cancer (NSCLC). Subsequent retrospective analysis of brain metastases-related outcomes was performed by reviewing patient electronic medical records. A competing risk multivariable regression was performed to estimate the adjusted hazard ratio for the development of brain metastases and non-brain metastases from NSCLC.

RESULTS

A total of 49 of 102 patients had died by the last follow-up. Median time of follow-up was 13 months (range 0.23-67 months). A total of 17 patients developed brain metastases. Median survival time after diagnosis of brain metastases was 3.58 months (95% confidence interval (CI) 2.17, not available). A total of 30 patients developed metastases without any evidence of brain metastases until the time of death or last follow-up. Competing risk analysis identified three genes that were downregulated differentially in the patients with brain metastases versus non-brain metastatic disease: CD37 (0.017), cystatin A (0.022), and IL-23A (0.027). Other factors associated with brain metastases include: stage T ( P ⩽ 8.3e-6) and stage N ( P= 6.8e-4).

CONCLUSIONS

We have identified three genes, CD37, cystatin A, and IL-23A, for which downregulation of gene expression was associated with a greater propensity for developing brain metastases. Validation of these biomarkers could have implications on surveillance patterns in patients with brain metastases from NSCLC.

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 tumor-targeting probe based on a mitophagy process for live imaging

A pH sensitive probe was designed for mitochondria and autolysosomes monitoring in cell level and tumor targeting imaging.

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.

Cystatin C as a p53-inducible apoptotic mediator that regulates cathepsin L activity

In response to various cellular stresses, p53 is activated and inhibits malignant transformation through the transcriptional regulation of its target genes. However, the full picture of the p53 downstream pathway still remains to be elucidated. Here we identified cystatin C, a major inhibitor of cathepsins, as a novel p53 target. In response to DNA damage, activated p53 induced cystatin C expression through p53 binding sequence in the first intron. We showed that cathepsin L activity was decreased in HCT116 p53^+/+ cells after adriamycin treatment, but not in HCT116 p53^−/− cells. We also found that knockdown of cystatin C reduced adriamycin‐induced caspase‐3 activation. Cystatin C expression was significantly downregulated in breast cancer cells with p53 mutations, and decreased cystatin C expression was associated with poor prognosis of breast cancer. Our findings revealed an important role of the p53–cystatin C pathway in human carcinogenesis.

Melittin suppresses cathepsin S-induced invasion and angiogenesis via blocking of the VEGF-A/VEGFR-2/MEK1/ERK1/2 pathway in human hepatocellular carcinoma

Melittin, a significant constituent of Apis mellifera (honeybee) venom, is a water-soluble toxic peptide that has traditionally been used as an antitumor agent. However, the underlying mechanisms by which it inhibits tumor cell growth and angiogenesis remain to be elucidated. In the present study, screening for increased cathepsin S (Cat S) expression levels was performed in MHCC97-H cells and various other hepatocellular carcinoma cell lines by reverse transcription-polymerase chain reaction and western blot analysis. A pcDNA3.1-small hairpin RNA (shRNA)-Cat S vector was stably transfected into MHCC97-H cells (shRNA/MHCC97-H) in order to knockdown the expression of Cat S. The effects resulting from the inhibition of Cat S-induced proliferation, invasion and angiogenesis by melittin were examined using cell proliferation, cell viability, flat plate colony formation, migration, wound healing, Transwell migration and ELISA assays. In order to substantiate the evidence for melittin-mediated inhibition of Cat S-induced angiogenesis, Cat S RNA was transfected into primary human umbilical vein endothelial cells (Cat S-HUVECs) to induce overexpression of the Cat S gene. The effects of melittin on HUVECs were examined using Transwell migration and tube formation assays. The findings demonstrated that melittin was able to significantly suppress MHCC97-H cell (Mock/MHCC97-H) proliferation, invasion and angiogenesis, as well as capillary tube formation of Cat S-HUVECs, in a dose-dependent manner. However, proliferation, invasion and angiogenesis in shRNA/MHCC97-H and in native HUVECs (Mock-HUVECs) were unaffected. In addition, melittin specifically decreased the expression of phosphorylated (activated) Cat S, and components of the vascular endothelial growth factor (VEGF)-A/VEGF receptor 2 (VEGFR-2)/mitogen-activated protein kinase kinase 1 (MEK1)/extracellular signal-regulated kinase (ERK)1/2 signaling pathway in Mock/MHCC97-H cells. In conclusion, the inhibition of tumor cell growth and anti-angiogenic activity exerted by melittin may be associated with anti-Cat S actions, via the inhibition of VEGF-A/VEGFR-2/MEK1/ERK1/2 signaling.

Quantitative proteomic analysis reveals effects of epidermal growth factor receptor (EGFR) on invasion-promoting proteins secreted by glioblastoma cells

Glioblastoma multiforme is a highly invasive and aggressive brain tumor with an invariably poor prognosis. The overexpression of epidermal growth factor receptor (EGFR) is a primary influencer of invasion and proliferation in tumor cells and the constitutively active EGFRvIII mutant, found in 30-65% of Glioblastoma multiforme, confers more aggressive invasion. To better understand how EGFR contributes to tumor aggressiveness, we investigated the effect of EGFR on the secreted levels of 65 rationally selected proteins involved in invasion. We employed selected reaction monitoring targeted mass spectrometry using stable isotope labeled internal peptide standards to quantity proteins in the secretome from five GBM (U87) isogenic cell lines in which EGFR, EGFRvIII, and/or PTEN were expressed. Our results show that cell lines with EGFR overexpression and constitutive EGFRvIII expression differ remarkably in the expression profiles for both secreted and intracellular signaling proteins, and alterations in EGFR signaling result in reproducible changes in concentrations of secreted proteins. Furthermore, the EGFRvIII-expressing mutant cell line secretes the majority of the selected invasion-promoting proteins at higher levels than other cell lines tested. Additionally, the intracellular and extracellular protein measurements indicate elevated oxidative stress in the EGFRvIII-expressing cell line. In conclusion, the results of our study demonstrate that EGFR signaling has a significant effect on the levels of secreted invasion-promoting proteins, likely contributing to the aggressiveness of Glioblastoma multiforme. Further characterization of these proteins may provide candidates for new therapeutic strategies and targets as well as biomarkers for this aggressive disease.

The current stage of cathepsin B inhibitors as potential anticancer agents

Cathepsin B is a lysosomal cysteine peptidase, with an important role in the development and progression of cancer. It is involved in the degradation of extracellular matrix proteins, a process promoting invasion and metastasis of tumor cells and tumor angiogenesis. Cathepsin B is unique among cathepsins in possessing both carboxypeptidase and endopeptidase activities. While the former is associated with its physiological role, the latter is involved in pathological degradation of the extracellular matrix. Its activities are regulated by different means, the most important being its endogenous inhibitors, the cystatins. In cancer this peptidase/inhibitor balance is altered, leading to harmful cathepsin B activity. The latter can be prevented by exogenous inhibitors. They differ in modes of inhibition, size, structure, binding affinity, selectivity, toxicity and bioavailability. In this article, we review the properties and function of endogenous and exogenous cathepsin B inhibitors and indicate their application as possible anticancer agents.

Inhibition of cathepsin S induces autophagy and apoptosis in human glioblastoma cell lines through ROS-mediated PI3K/AKT/mTOR/p70S6K and JNK signaling pathways

Cathepsin S is a lysosomal cysteine protease that is overexpressed in various cancer models and plays important role in tumorigenesis, however the mechanisms are unclear. In the present study, we found that inhibition of cathepsin S induced autophagy and mitochondrial apoptosis in human glioblastoma cells. Blockade of autophagy by either a chemical inhibitor or RNA interference attenuated cathespin S inhibition-induced apoptosis. Furthermore, autophagy and apoptosis induction was dependent on the suppression of phosphatidylinositide 3-kinases/protein kinase B/mammalian target of rapamycin/p70S6 kinase (PI3K/AKT/mTOR/p70S6K) signaling pathway and activation of c-Jun N-terminal kinase (JNK) signaling pathway. In addition, reactive oxygen species (ROS) served as an upstream of PI3K/AKT/mTOR/p70S6K and JNK signaling pathways. In conclusion, the current study revealed that cathepsin S played an important role in the regulation of autophagy and apoptosis in human glioblastoma cells.

Cysteine cathepsins and extracellular matrix degradation

BACKGROUND

Cysteine cathepsins are normally found in the lysosomes where they are involved in intracellular protein turnover. Their ability to degrade the components of the extracellular matrix in vitro was first reported more than 25years ago. However, cathepsins were for a long time not considered to be among the major players in ECM degradation in vivo. During the last decade it has, however, become evident that abundant secretion of cysteine cathepsins into extracellular milieu is accompanying numerous physiological and disease conditions, enabling the cathepsins to degrade extracellular proteins.

SCOPE OF VIEW

In this review we will focus on cysteine cathepsins and their extracellular functions linked with ECM degradation, including regulation of their activity, which is often enhanced by acidification of the extracellular microenvironment, such as found in the bone resorption lacunae or tumor microenvironment. We will further discuss the ECM substrates of cathepsins with a focus on collagen and elastin, including the importance of that for pathologies. Finally, we will overview the current status of cathepsin inhibitors in clinical development for treatment of ECM-linked diseases, in particular osteoporosis.

MAJOR CONCLUSIONS

Cysteine cathepsins are among the major proteases involved in ECM remodeling, and their role is not limited to degradation only. Deregulation of their activity is linked with numerous ECM-linked diseases and they are now validated targets in a number of them. Cathepsins S and K are the most attractive targets, especially cathepsin K as a major therapeutic target for osteoporosis with drugs targeting it in advanced clinical trials.

GENERAL SIGNIFICANCE

Due to their major role in ECM remodeling cysteine cathepsins have emerged as an important group of therapeutic targets for a number of ECM-related diseases, including, osteoporosis, cancer and cardiovascular diseases. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Invasion as target for therapy of glioblastoma multiforme

The survival of cancer patients suffering from glioblastoma multiforme is limited to just a few months even after treatment with the most advanced techniques. The indefinable borders of glioblastoma cell infiltration into the surrounding healthy tissue prevent complete surgical removal. In addition, genetic mutations, epigenetic modifications and microenvironmental heterogeneity cause resistance to radio- and chemotherapy altogether resulting in a hardly to overcome therapeutic scenario. Therefore, the development of efficient therapeutic strategies to combat these tumors requires a better knowledge of genetic and proteomic alterations as well as the infiltrative behavior of glioblastoma cells and how this can be targeted. Among many cell surface receptors, members of the integrin family are known to regulate glioblastoma cell invasion in concert with extracellular matrix degrading proteases. While preclinical and early clinical trials suggested specific integrin targeting as a promising therapeutic approach, clinical trials failed to deliver improved cure rates up to now. Little is known about glioblastoma cell motility, but switches in invasion modes and adaption to specific microenvironmental cues as a consequence of treatment may maintain tumor cell resistance to therapy. Thus, understanding the molecular basis of integrin and protease function for glioblastoma cell invasion in the context of radiochemotherapy is a pressing issue and may be beneficial for the design of efficient therapeutic approaches. This review article summarizes the latest findings on integrins and extracellular matrix in glioblastoma and adds some perspective thoughts on how this knowledge might be exploited for optimized multimodal therapy approaches.

Crosstalk between B16 melanoma cells and B-1 lymphocytes induces global changes in tumor cell gene expression

The analysis of gene expression patterns in cancers has improved the understanding of the mechanisms underlying the process of metastatic progression. However, the acquisition of invasive behavior in melanoma is poorly understood. In melanoma, components of the immune system can contribute to tumor progression, and inflammatory cells can influence almost all aspects of cancer progression, including metastasis. Recent studies have attributed an important role to B-1 cells, a subset of B lymphocytes, in melanoma progression. In vitro interactions between B16 melanoma cells and B-1 lymphocytes lead to increased B16 cell metastatic potential, but the molecular changes induced by B-1 lymphocytes on B16 cells have not yet been elucidated. In this study, we used a microarray approach to assess the gene expression profile of B16 melanoma cells following contact with B-1 lymphocytes (B16B1). The microarray analysis identified upregulation in genes involved with metastatic progression, such as ctss, ccl5, cxcl2 and stat3. RT-qPCR confirmed this increase in mRNA expression in B16B1 samples. As previous studies have indicated that the ERK1/2 MAPK cascade is activated in melanoma cells following contact with B-1 lymphocytes, RT-qPCR was performed with RNA from melanoma cells before and after contacting B-1 cells and untreated or treated with ERK phosphorylation inhibitors. The results showed that the expression of stat3, ctss and cxcl2 increased in B16B1 but decreased following ERK1/2 MAPK inhibition. Ccl5 gene expression increased after contacting B-1 cells and was maintained at the same level following inhibitor treatment. Stat3 was verified and validated at the protein level by Western blot analysis. STAT3 expression was also significantly increased in B16B1, suggesting that this pathway can also contribute to the increased metastatic phenotype observed in our model. These results indicated that B-1 cells induce important global gene expression changes in B16 melanoma cells. We also evaluated the relationship of some of the genes identified as differentially expressed and the ERK1/2 MAPK cascade. This work may have important implications for understanding the role of B-1 lymphocytes and the ERK/MAPK cascade in the metastatic process.

Inhibition of glioma cell lysosome exocytosis inhibits glioma invasion

Cancer cells invade by secreting enzymes that degrade the extracellular matrix and these are sequestered in lysosomal vesicles. In this study, the effects of the selective lysosome lysing drug GPN and the lysosome exocytosis inhibitor vacuolin-1 on lysosome exocytosis were studied to determine their effect on glioma cell migration and invasion. Both GPN and vacuolin-1 evidently inhibited migration and invasion in transwell experiments and scratch experiments. There are more lysosomes located on the cell membrane of glioma cells than of astrocytes. GPN decreased the lysosome number on the cell membrane. We found that rab27A was expressed in glioma cells, and colocalized with cathepsin D in lysosome. RNAi-Rab27A inhibited lysosome cathepsin D exocytosis and glioma cell invasion in an in vitro assay. Inhibition of cathepsin D inhibited glioma cell migration. The data suggest that the inhibition of lysosome exocytosis from glioma cells plays an important modulatory role in their migration and invasion.

Myrtenal ameliorates diethylnitrosamine-induced hepatocarcinogenesis through the activation of tumor suppressor protein p53 and regulation of lysosomal and mitochondrial enzymes

Myrtenal is a novel class of compound belongs to monoterpenes found predominantly in mint, pepper, etc., and it was shown to have excellent pharmacological activities against many diseases among which cancer is imperative. Hepatocellular carcinoma is a primary malignancy of the hepatocytes, which rapidly leads to death in short periods. The aim of this study was to investigate the possible therapeutic efficiency of myrtenal against diethylnitrosamine-induced experimental hepatocarcinogenesis by analyzing the key enzymes of carbohydrate metabolism, lysosomal and mitochondrial TCA cycle enzymes, and also the possible role of tumor suppressor protein p53, and scanning electron microscopic studies. The results revealed that myrtenal significantly ameliorated the altered enzymes of carbohydrate metabolism, lysosomal and mitochondrial enzymes, and interestingly the tumor suppressor protein p53 was found to be significantly accumulated in myrtenal-treated animals, which inevitably confirms that myrtenal has a prominent role in preventing the liver cancer during treatment. Furthermore, the antineoplastic property was well evidenced by the mRNA expression of p53 protein by the reverse-transcriptase polymerase chain reaction and immunoblot analysis. The observed anticancer property of myrtenal may be due to the involvement and expression of p53 and influence in the mitochondrial and lysosomal membrane integrity and also interference in the gluconeogenesis process of cancer cells. Our results suggest that myrtenal is very efficient and useful compound in the treatment of liver cancer in future.

Targeting cathepsin S induces tumor cell autophagy via the EGFR-ERK signaling pathway

Cathepsin S is a cellular cysteine protease, which is frequently over-expressed in human cancer cells and plays important role in tumor metastasis. However, the role of cathepsin S in regulating cancer cell survival and death remains undefined. The aim of this study was to determine whether targeting cathepsin S could induce autophagy/apoptosis in cancer cells. In this study, we demonstrated that targeting cathepsin S by either specific small molecular inhibitors or cathepsin S siRNA induced autophagy and subsequent apoptosis in human cancer cells, and the induction of autophagy was dependent on the phosphorylation of EGFR and activation of the EGFR-related ERK/MAPK-signaling pathway. In conclusion, the current study reveals that cathepsin S plays an important role in the regulation of cell autophagy through interference with the EGFR-ERK/MAPK-signaling pathway.

Secretome signature of invasive glioblastoma multiforme

The incurability of malignant glioblastomas is mainly attributed to their highly invasive nature coupled with resistance to chemo- and radiation therapy. Because invasiveness is partially dictated by the proteins these tumors secrete we used SILAC to characterize the secretomes of four glioblastoma cell lines (LN18, T98, U118 and U87). Although U87 and U118 cells both secreted high levels of well-known invasion promoting proteins, a Matrigel invasion assay showed U87 cells to be eight times more invasive than U118 cells, suggesting that additional proteins secreted by U87 cells may contribute to the highly invasive phenotype. Indeed, we identified a number of proteins highly or exclusively expressed by U87 cells as compared to the less invasive cell lines. The most striking of these include ADAM9, ADAM10, cathepsin B, cathepsin L1, osteopontin, neuropilin-1, semaphorin-7A, suprabasin, and chitinase-3-like protein 1. U87 cells also expressed significantly low levels of some cell adhesion proteins such as periostin and EMILIN-1. Correlation of secretome profiles with relative levels of invasiveness using Pavlidis template matching further indicated potential roles for these proteins in U87 glioblastoma invasion. Antibody inhibition of CH3L1 reduced U87 cell invasiveness by 30%.

Differential role of cathepsins B and L in autophagy-associated cell death induced by arsenic trioxide in U87 human glioblastoma cells

Arsenic trioxide (arsenite) was the first chemotherapeutic drug to be described and is now being rediscovered in cancer treatment, including glioblastoma multiforme. Arsenite toxicity triggers autophagy in cancer cells, although final stages of the process involve executive caspases, suggesting an interplay between autophagic and apoptotic pathways that awaits to be explained at a molecular level. We evaluated the contribution of the lysosomal cathepsins (Cat) L and B, which are upregulated in glioblastomas, in the mechanism of arsenite toxicity in human glioblastoma cells. Arsenite treatment induced autophagosome formation and permeabilization of mitochondria, followed by caspase 3/7-mediated apoptosis. The autophagy inhibitor 3-methyladenine protected from arsenite toxicity, whereas bafilomycin A1 did not. Furthermore, arsenite significantly decreased CatB levels and selectively inhibited its cellular and recombinant protein activity, while not affecting CatL. However, downregulation of CatL greatly enhanced apoptosis by arsenite. Our results show that arsenite toxicity involves a complex interplay between autophagy and apoptosis in human glioblastoma cells and is associated with inhibition of CatB, and that this toxicity is highly exacerbated by simultaneous CatL inhibition. The latter points to a synergy that could be used in clinical treatment to lower the therapeutic dose, thus avoiding the toxic side effects of arsenite in glioblastoma management.

Cathepsin D messenger RNA is downregulated in human lung cancer

OBJECTIVES

Lysosomal proteases cathepsins B and D (CB and CD) play a significant part in cancer progression. For many oncological diseases protein expression levels of CB and CD have been investigated and correlations with tumour characteristics revealed. Meanwhile, there is very little information concerning mRNA expression level.

METHODS

In the present work, data about mRNA levels of CB and CD in human lung cancer was obtained using reverse transcription followed by real-time polymerase chain reaction.

RESULTS

For the first time CD and CB mRNA in human lung cancer tumours was quantified. It was shown that CB and CD mRNA levels do not correlate with any tumour characteristics. However, in most analysed tumours, expression of CD mRNA was downregulated compared with adjacent normal tissue (p <0.0003).

CONCLUSIONS

The data obtained indicate CD mRNA as a potential lung cancer marker.

The transglutaminase 2 gene is aberrantly hypermethylated in glioma

Transglutaminase 2 (TG2) is a ubiquitously expressed protein that catalyzes protein/protein crosslinking. Because extracellular TG2 crosslinks components of the extracellular matrix, TG2 is thought to function as a suppressor of cellular invasion. We have recently uncovered that the TG2 gene (TGM2) is a target for epigenetic silencing in breast cancer, highlighting a molecular mechanism that drives reduced TG2 expression, and this aberrant molecular event may contribute to invasiveness in this tumor type. Because tumor invasiveness is a primary determinant of brain tumor aggressiveness, we sought to determine if TGM2 is targeted for epigenetic silencing in glioma. Analysis of TGM2 gene methylation in a panel of cultured human glioma cells indicated that the 5' flanking region of the TGM2 gene is hypermethylated and that this feature is associated with reduced TG2 expression as judged by immunoblotting. Further, culturing glioma cells in the presence of the global DNA demethylating agent 5-aza-2'-deoxycytidine and the histone deacetylase inhibitor Trichostatin A resulted in re-expression of TG2 in these lines. In primary brain tumors we observed that the TGM2 promoter is commonly hypermethylated and that this feature is a cancer-associated phenomenon. Using publically available databases, TG2 expression in gliomas was found to vary widely, with many tumors showing overexpression or underexpression of this gene. Since overexpression of TG2 leads to resistance to doxorubicin through the ectopic activation of NFκB, we sought to examine the effects of recombinant TG2 expression in glioma cells treated with commonly used brain tumor therapeutics. We observed that in addition to doxorubicin, TG2 expression drove resistance to CCNU; however, TG2 expression did not alter sensitivity to other drugs tested. Finally, a catalytically null mutant of TG2 was also able to support doxorubicin resistance in glioma cells indicating that transglutaminase activity is not necessary for the resistance phenotype.

Comparative study of mature and zymogen mite cysteine protease stability and pH unfolding

BACKGROUND

Papain-like proteases (CA1) are synthesized as inactive precursors carrying an N-terminal propeptide, which is further removed under acidic conditions to generate active enzymes.

METHODS

To have a better insight into the mechanism of activation of this protease family, we compared the pH unfolding of the zymogen and the mature form of the mite cysteine protease Der p 1.

RESULTS

We showed that the presence of the propeptide does not significantly influence the pH-induced unfolding of the catalytic domain but does affect its fluorescence properties by modifying the exposure of the tryptophan 192 to the solvent. In addition, we demonstrated that the propeptide displays weaker pH stability than the protease domain confirming that the unfolding of the propeptide is the key event in the activation process of the zymogen.

GENERAL SIGNIFICANCE

Finally, we show, using thermal denaturation and enzymatic activity measurements, that whatever the pH value, the propeptide does not stabilize the structure of the catalytic domain but very interestingly, prevents its autolysis.

Does protein expression predict recurrence of benign World Health Organization grade I meningioma?

The aim of this study was to assess the predictive value of recurrence of protein expression in surgical samples of meningiomas. Thus, the expression of proteins that have been reported to be associated with prognosis of meningiomas was assessed in a sample of 59 World Health Organization grade I tumors obtained after Simpson grade I to III surgical resection (complete excision) and that were followed for 6 to 16 years. The expression was investigated applying immunohistochemical and tissue microarray techniques. One protein, the hepatocytic growth factor receptor, of 22 investigated proteins, showed significantly differing expression when comparing the 38 nonrecurrent with the 21 recurrent World Health Organization grade I meningiomas. It is noteworthy however that by means of logistic regression analyses, the independent predictive value of this protein expression was not significantly associated with the recurrence. Furthermore, it is noteworthy that the proliferation rate estimated by means of Ki67 expression did not show a significant difference, being 3.3 +/- 0.4 for the nonrecurrent meningioma and 3.9 +/- 0.5 for the recurrent and ranging from 0% to 10%. A significant and differing Spearman rank order of correlation was noted between 19 pairs of the investigated proteins when comparing nonrecurrent with recurrent World Health Organization grade I meningiomas. None of these correlations, however, showed a significant association by means of logistic regression analyses. Our results indicate that the Simpson grade significantly alters the outcome of a World Health Organization I grade meningioma and a longer follow-up period significantly increases the risk of recurrence. The expression of none of the proteins or correlation between protein expressions previously reported to be of significance regarding recurrence can be recommended as a diagnostic tool while assessing the risk of recurrence of World Health Organization grade I meningiomas.

Biological behaviors and proteomics analysis of hybrid cell line EAhy926 and its parent cell line A549

Background

It is well established that cancer cells can fuse with endothelial cells to form hybrid cells spontaneously, which facilitates cancer cells traversing the endothelial barrier to form metastases. However, up to now, little is known about the biologic characteristics of hybrid cells. Therefore, we investigate the malignant biologic behaviors and proteins expression of the hybrid cell line EAhy926 with its parent cell line A549.

Methods

Cell counting and flow cytometry assay were carried out to assess cell proliferation. The number of cells attached to the extracellular matrix (Matrigel) was measured by MTT assay for the adhesion ability of cells. Transwell chambers were established for detecting the ability of cell migration and invasion. Tumor xenograft test was carried out to observe tumorigenesis of the cell lines. In addition, two-dimensional electrophoresis (2-DE) and mass spectrometry were utilized to identify differentially expressed proteins between in Eahy926 cells and in A549 cells.

Results

The doubling time of EAhy926 cell and A549 cell proliferation was 25.32 h and 27.29 h, respectively (P > 0.1). Comparing the phase distribution of cell cycle of EAhy926 cells with that of A549 cells, the percentage of cells in G0/G1 phase, in S phase and in G2/M phase was (63.7% ± 2.65%) VS (60.0% ± 3.17%), (15.4% ± 1.52%) VS (13.8% ± 1.32%), and (20.9% ± 3.40%) VS (26.3% ± 3.17%), respectively (P > 0.05). For the ability of cell adhesion of EAhy926 cells and A549 cells, the value of OD in Eahy926 cells was significantly higher than that in A549 cells (0.3236 ± 0.0514 VS 0.2434 ± 0.0390, P < 0.004). We also found that the migration ability of Eahy926 cells was stronger than that of A549 cells (28.00 ± 2.65 VS 18.00 ± 1.00, P < 0.01), and that the invasion ability of Eahy926 cells was significantly weak than that of A549 cells (15.33 ± 0.58 VS 26.67 ± 2.52, P < 0.01). In the xenograft tumor model, expansive masses of classic tumor were found in the A549 cells group, while subcutaneous inflammatory focuses were found in the EAhy926 cells group. Besides, twenty-eight proteins were identified differentially expressed between in EAhy926 cells and in A549 cells by proteomics technologies.

Conclusion

As for the biological behaviors, the ability of cell proliferation in Eahy926 cells was similar to that in A549 cells, but the ability in adhesion and migration of Eahy926 cells was higher. In addition, Eahy926 cells had weaker ability in invasion and could not form tumor mass. Furthermore, there were many differently expressed proteins between hybrid cell line Eahy926 cells and A549 cells, which might partly account for some of the differences between their biological behaviors at the molecular level. These results may help to understand the processes of tumor angiogenesis, invasion and metastasis, and to search for screening method for more targets for tumor therapy in future.

Invasion suppressor cystatin E/M (CST6): high-level cell type-specific expression in normal brain and epigenetic silencing in gliomas

DNA hypermethylation-mediated gene silencing is a frequent and early contributor to aberrant cell growth and invasion in cancer. Malignant gliomas are the most common primary brain tumors in adults and the second most common tumor in children. Morbidity and mortality are high in glioma patients because tumors are resistant to treatment and are highly invasive into surrounding brain tissue rendering complete surgical resection impossible. Invasiveness is regulated by the interplay between secreted proteases (eg, cathepsins) and their endogenous inhibitors (cystatins). In our previous studies we identified cystatin E/M (CST6) as a frequent target of epigenetic silencing in glioma. Cystatin E/M is a potent inhibitor of cathepsin B, which is frequently overexpressed in glioma. Here, we study the expression of cystatin E/M in normal brain and show that it is highly and moderately expressed in oligodendrocytes and astrocytes, respectively, but not in neurons. Consistent with this, the CST6 promoter is hypomethylated in all normal samples using methylation-specific PCR, bisulfite genomic sequencing, and pyrosequencing. In contrast, 78% of 28 primary brain tumors demonstrated reduced/absent cystatin E/M expression using a tissue microarray and this reduced expression correlated with CST6 promoter hypermethylation. Interestingly, CST6 was expressed in neural stem cells (NSC) and markedly induced upon differentiation, whereas a glioma tumor initiating cell (TIC) line was completely blocked for CST6 expression by promoter methylation. Analysis of primary pediatric brain tumor-derived lines also showed CST6 downregulation and methylation in nearly 100% of 12 cases. Finally, ectopic expression of cystatin E/M in glioma lines reduced cell motility and invasion. These results demonstrate that epigenetic silencing of CST6 is frequent in adult and pediatric brain tumors and occurs in TICs, which are thought to give rise to the tumor. CST6 methylation may therefore represent a novel prognostic marker and therapeutic target specifically altered in TICs.

Up-regulation of micro-RNA-221 (miRNA-221; chr Xp11.3) and caspase-3 accompanies down-regulation of the survivin-1 homolog BIRC1 (NAIP) in glioblastoma multiforme (GBM)

Glioblastoma multiforme (GBM) represents a class of malignant gliomas which rapidly proliferate, invade and destroy surrounding brain tissues. This study examined micro-RNA (miRNA) speciation and miRNA effects on gene expression in six ATCC glioma and GBM cell lines and in 14 glioma and GBM samples obtained from human brain biopsy. We observed selective up-regulation of miRNA-221 and down-regulation of a miRNA-221 messenger RNA target encoding the survivin-1 homolog BIRC1, a neuronal inhibitor of apoptosis protein (NIAP) and marker for neurodegeneration. The expression of BIRC5 (survivin-1) and caspase-3 were found to be significantly up-regulated, particularly in stage IV GBM. These studies suggest that the abundance and speciation of the BIRC family of neural cell fate regulators are differentially regulated in glioma and GBM, and may contribute to progressive changes in apoptotic signaling and altered neural cell cycling functions.

Internalization of cystatin C in human cell lines

Altered protease activity is considered important for tumour invasion and metastasis, processes in which the cysteine proteases cathepsin B and L are involved. Their natural inhibitor cystatin C is a secreted protein, suggesting that it functions to control extracellular protease activity. Because cystatins added to cell cultures can inhibit polio, herpes simplex and coronavirus replication, which are intracellular processes, the internalization and intracellular regulation of cysteine proteases by cystatin C should be considered. The extension, mechanism and biological importance of this hypothetical process are unknown. We investigated whether internalization of cystatin C occurs in a set of human cell lines. Demonstrated by flow cytometry and confocal microscopy, A‐431, MCF‐7, MDA‐MB‐453, MDA‐MB‐468 and Capan‐1 cells internalized fluorophore‐conjugated cystatin C when exposed to physiological concentrations (1 μm). During cystatin C incubation, intracellular cystatin C increased after 5 min and accumulated for at least 6 h, reaching four to six times the baseline level. Western blotting showed that the internalized inhibitor was not degraded. It was functionally intact and extracts of cells exposed to cystatin C showed a higher capacity to inhibit papain and cathepsin B than control cells (decrease in enzyme activity of 34% and 37%, respectively). The uptake of labelled cystatin C was inhibited by unlabelled inhibitor, suggesting a specific pathway for the internalization. We conclude that the cysteine protease inhibitor cystatin C is internalized in significant quantities in various cancer cell lines. This is a potentially important physiological phenomenon not previously described for this group of inhibitors.

Synthesis and characterization of glucosamine-bound near-infrared probes for optical imaging

[structure: see text] Two novel near-infrared (NIR) fluorescent probes have been synthesized by linking a carbocyanine fluorophore and glucosamine through different linkers. These probes demonstrated a high quantum yield, low cytotoxicity, reversible pH-dependent fluorescence in the physiological pH range, and a decreased aggregation tendency in aqueous solutions. In vitro NIR optical imaging studies revealed cellular uptake and strong intracellular NIR fluorescence of these two probes in four breast epithelial cell lines.

Neural stem cell markers, nestin and musashi proteins, in the progression of human glioma: correlation of nestin with prognosis of patient survival

BACKGROUND

The IF protein nestin and the RNA-binding protein musashi are expressed by neural progenitor cells during CNS development. Their expression in glial tumors was evaluated by immunohistochemistry, and the histopathological scores correlated with levels of cysteine cathepsins that are known prognostic markers in several tumors.

METHODS

The levels of nestin, musashi, and cathepsins B and L were assessed by immunohistochemical analysis of biopsies from 87 patients with primary CNS tumors. To confirm the immunohistochemical data, nestin expression was analyzed by real-time PCR in 12 brain tumor biopsies. The exact location of nestin-positive cells was determined by mapping the distribution of nestin in a highly invasive human glioma xenograft model.

RESULTS

Immunostaining revealed nestin to be expressed in 95.8% and musashi in 80% of the patient biopsies. The total IHC score for nestin was significantly higher in high- than in low-grade tumors (P < .0001). No difference was observed for musashi (P = .11). Real-time PCR of nestin expression confirmed the immunohistochemical data. Nestin expression was shown to be a strong prognostic marker for decreased overall survival (P = .0001), whereas musashi expression has no prognostic significance. Moreover, nestin was shown by Cox regression analysis to be a stronger prognostic marker than cathepsins B and L. IHC staining of nestin in a xenograft model showed that its expression is localized mainly in the invasive tumor cells at the tumor periphery.

CONCLUSIONS

Nestin is shown to be a strong prognostic marker for glioma malignancy. The presented data links the invasive glioma cells to CNS precursor cells, indicating that the most malignant cells in the gliomas may well be closely related to the glioma stem cells.