Characteristics of ABCC4 and ABCG2 High Expression Subpopulations in CRC-A New Opportunity to Predict Therapy Response.

BACKGROUND: Our previous findings proved that ABCC4 and ABCG2 proteins present much more complex roles in colorectal cancer (CRC) than typically cancer-associated functions as drug exporters. Our objective was to evaluate their predictive/diagnostic potential. METHODS: CRC patients' transcriptomic data from the Gene Expression Omnibus database (GSE18105, GSE21510 and GSE41568) were discriminated into two subpopulations presenting either high expression levels of ABCC4 (ABCC4 High) or ABCG2 (ABCG2 High). Subpopulations were analysed using various bioinformatical tools and platforms (KEEG, Gene Ontology, FunRich v3.1.3, TIMER2.0 and STRING 12.0). RESULTS: The analysed subpopulations present different gene expression patterns. The protein-protein interaction network of subpopulation-specific genes revealed the top hub proteins in ABCC4 High: RPS27A, SRSF1, DDX3X, BPTF, RBBP7, POLR1B, HNRNPA2B1, PSMD14, NOP58 and EIF2S3 and in ABCG2 High: MAPK3, HIST2H2BE, LMNA, HIST1H2BD, HIST1H2BK, HIST1H2AC, FYN, TLR4, FLNA and HIST1H2AJ. Additionally, our multi-omics analysis proved that the ABCC4 expression correlates with substantially increased tumour-associated macrophage infiltration and sensitivity to FOLFOX treatment. CONCLUSIONS: ABCC4 and ABCG2 may be used to distinguish CRC subpopulations that present different molecular and physiological functions. The ABCC4 High subpopulation demonstrates significant EMT reprogramming, RNA metabolism and high response to DNA damage stimuli. The ABCG2 High subpopulation may resist the anti-EGFR therapy, presenting higher proteolytical activity.

Evening Primrose Extract Modulates TYMS Expression via SP1 Transcription Factor in Malignant Pleural Mesothelioma.

PURPOSE: To determine the mechanism of EPE in downregulating TYMS in MPM cancer. METHODS: The TYMS mRNA expression with epithelial-to-mesenchymal transition biomarkers and nuclear factor SP1 was assessed using the GEO database in a data set of MPM patients (GSE51024). Invasive MPM cell lines were in vitro models for the investigation of TYMS expression after EPE treatment. The tyms promoter SP1 binding sequences were determined using Genomatix v 3.4 software Electrophoretic mobility shift and dual-luciferase reporter assays revealed specific SP1 motifs in the interaction of EPE and reference compounds. Chromatin immunoprecipitation and Re-ChIP were used for the co-occupancy study. RESULTS: In MPM patients, a positive correlation of overexpressed TYMS with mesenchymal TWIST1, FN1 and N-cadherin was observed. EPE and its major components, gallic and ellagic acid (GA and EA, respectively), downregulated TYMS in invasive MPM cells by interacting with particular SP1 motifs on the tyms promoter. The luciferase constructs confirmed the occupation of two SP1 regulatory regions critical for the promotion of TYMS expression. Both EPE and reference standards influenced SP1 translocation into the nucleus. CONCLUSION: EPE components reduced TYMS expression by occupation of SP1 motifs on the tyms promoter and reversed the EMT phenotype of invasive MPM cells. Further in-depth analysis of the molecular docking of polyphenol compounds with SP1 regulatory motifs is required.

The Comparison of Serum Exosome Protein Profile in Diagnosis of NSCLC Patients.

A thorough study of the exosomal proteomic cargo may enable the identification of proteins that play an important role in cancer development. The aim of this study was to compare the protein profiles of the serum exosomes derived from non-small lung cancer (NSCLC) patients and healthy volunteers (control) using the high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS) method to identify potentially new diagnostic and/or prognostic protein biomarkers. Proteins exclusively identified in NSCLC and control groups were analyzed using several bioinformatic tools and platforms (FunRich, Vesiclepedia, STRING, and TIMER2.0) to find key protein hubs involved in NSCLC progression and the acquisition of metastatic potential. This analysis revealed 150 NSCLC proteins, which are significantly involved in osmoregulation, cell-cell adhesion, cell motility, and differentiation. Among them, 3 proteins: Interleukin-34 (IL-34), HLA class II histocompatibility antigen, DM alpha chain (HLA-DMA), and HLA class II histocompatibility antigen, DO beta chain (HLA-DOB) were shown to be significantly involved in the cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs) infiltration processes. Additionally, detected proteins were analyzed according to the presence of lymph node metastasis, showing that differences in frequency of detection of protein FAM166B, killer cell immunoglobulin-like receptor 2DL1, and olfactory receptor 52R1 correlate with the N feature according to the TNM Classification of Malignant Tumors. These results prove their involvement in NSCLC lymph node spread and metastasis. However, this study requires further investigation.

Platelet-derived microparticles stimulate the invasiveness of colorectal cancer cells via the p38MAPK-MMP-2/MMP-9 axis.

BACKGROUND: Metastasis is the main cause of death in patients with colorectal cancer (CRC). Apart from platelets, platelet-derived microparticles (PMPs) are also considered important factors that can modify the activity of cancer cells. PMPs are incorporated by cancer cells and can also serve as intracellular signalling vesicles. PMPs are believed to affect cancer cells by upregulating their invasiveness. To date, there is no evidence that such a mechanism occurs in colorectal cancer. It has been shown that platelets can stimulate metalloproteases (MMPs) expression and activity via the p38MAPK pathway in CRC cells, leading to their elevated migratory potential. This study aimed to investigate the impact of PMPs on the invasive potential of CRC cells of various phenotypes via the MMP-2, MMP-9 and p38MAPK axis. METHODS: We used various CRC cell lines, including the epithelial-like HT29 and the mesenchymal-like SW480 and SW620. Confocal imaging was applied to study PMP incorporation into CRC cells. The presence of surface receptors on CRC cells after PMP uptake was evaluated by flow cytometry. Transwell and scratch wound-healing assays were used to evaluate cell migration. The level of C-X-C chemokine receptor type 4 (CXCR4), MMP-2, and MMP-9 and the phosphorylation of ERK1/2 and p38MAPK were measured by western blot. MMP activity was determined using gelatine-degradation assays, while MMP release was evaluated by ELISA. RESULTS: We found that CRC cells could incorporate PMPs in a time-dependent manner. Moreover, PMPs could transfer platelet-specific integrins and stimulate the expression of integrins already present on tested cell lines. While mesenchymal-like cells expressed less CXCR4 than epithelial-like CRC cells, PMP uptake did not increase its intensity. No significant changes in CXCR4 level either on the surface or inside CRC cells were noticed. Levels of cellular and released MMP-2 and MMP-9 were elevated in all tested CRC cell lines after PMP uptake. PMPs increased the phosphorylation of p38MAPK but not that of ERK1/2. Inhibition of p38MAPK phosphorylation reduced the PMP-induced elevated level and release of MMP-2 and MMP-9 as well as MMP-dependent cell migration in all cell lines. CONCLUSIONS: We conclude that PMPs can fuse into both epithelial-like and mesenchymal-like CRC cells and increase their invasive potential by inducing the expression and release of MMP-2 and MMP-9 via the p38MAPK pathway, whereas CXCR4-related cell motility or the ERK1/2 pathway appears to not be affected by PMPs. Video Abstract.

Sentiment analysis of the Twitter response to Netflix's Our Planet documentary.

The role of nature documentaries in shaping public attitudes and behavior toward conservation and wildlife issues is unclear. We analyzed the emotional content of over 2 million tweets related to Our Planet, a major nature documentary released on Netflix, with dictionary and rule-based automatic sentiment analysis. We also compared the sentiment associated with species mentioned in Our Planet and a set of control species with similar features but not mentioned in the documentary. Tweets were largely negative in sentiment at the time of release of the series. This effect was primarily linked to the highly skewed distributions of retweets and, in particular, to a single negatively valenced and massively retweeted tweet (>150,000 retweets). Species mentioned in Our Planet were associated with more negative sentiment than the control species, and this effect coincided with a short period following the airing of the series. Our results are consistent with a general negativity bias in cultural transmission and document the difficulty of evoking positive sentiment, on social media and elsewhere, in response to environmental problems.

Análisis de sentimientos de la respuesta en Twitter al documental Nuestro Planeta de Netflix Resumen No está claro el papel que tienen los documentales sobre naturaleza en la formación de actitudes públicas y respuestas a los temas de conservación y vida silvestre. Aplicamos un análisis automático de sentimientos basado en reglas y el diccionario al contenido emocional de más de dos millones de tuits relacionados a Nuestro Planeta, un importante documental estrenado en Netflix. También comparamos entre los sentimientos asociados a las especies mencionadas en el documental y un conjunto de especies control con características similares pero que no mencionan en el documental. En general, los tuits contenían sentimientos negativos cuando se estrenó la serie. Relacionamos este efecto a la distribución sesgada de retuits particularmente de un solo tuit negativo con retuits masivos (>150,000). Las especies mencionadas estuvieron asociadas con más sentimientos negativos que las especies control. Este efecto coincidió con un periodo corto después de la emisión de la serie. Nuestros resultados son coherentes con un sesgo generalizado de negatividad en la transmisión cultural y documentan lo difícil que es provocar sentimientos positivos, en redes sociales o en demás sitios, como respuesta a los problemas ambientales.

Isothiocyanates (ITCs) 1-(Isothiocyanatomethyl)-4-phenylbenzene and 1-Isothiocyanato-3,5-bis(trifluoromethyl)benzene-Aldehyde Dehydrogenase (ALDH) Inhibitors, Decreases Cisplatin Tolerance and Migratory Ability of NSCLC.

One of the main treatment modalities for non-small-cell lung cancer (NSCLC) is cisplatin-based chemotherapy. However, the acquisition of cisplatin resistance remains a major problem. Existing chemotherapy regimens are often ineffective against cancer cells expressing aldehyde dehydrogenase (ALDH). As such, there is an urgent need for therapies targeting ALDH-positive cancer cells. The present study compares the anticancer properties of 36 structurally diverse isothiocyanates (ITCs) against NSCLC cells with the ALDH inhibitor disulfiram (DSF). Their potential affinity to ALDH isoforms and ABC proteins was assessed using AutoDockTools, allowing for selection of three compounds presenting the strongest affinity to all tested proteins. The selected ITCs had no impact on NSCLC cell viability (at tested concentrations), but significantly decreased the cisplatin tolerance of cisplatin-resistant variant of A549 (A549CisR) and advanced (stage 4) NSCLC cell line H1581. Furthermore, long-term supplementation with ITC 1-(isothiocyanatomethyl)-4-phenylbenzene reverses the EMT phenotype and migratory potential of A549CisR to the level presented by parental A549 cells, increasing E-Cadherin expression, followed by decreased expression of ABCC1 and ALDH3A1. Our data indicates that the ALDH inhibitors DSF and ITCs are potential adjuvants of cisplatin chemotherapy.

Integrated Bioinformatics Analysis of the Hub Genes Involved in Irinotecan Resistance in Colorectal Cancer.

Different drug combinations including irinotecan remain some of the most important therapeutic modalities in treating colorectal cancer (CRC). However, chemotherapy often leads to the acquisition of cancer drug resistance. To bridge the gap between in vitro and in vivo models, we compared the mRNA expression profiles of CRC cell lines (HT29, HTC116, and LoVo and their respective irinotecan-resistant variants) with patient samples to select new candidate genes for the validation of irinotecan resistance. Data were downloaded from the Gene Expression Omnibus (GEO) (GSE42387, GSE62080, and GSE18105) and the Human Protein Atlas databases and were subjected to an integrated bioinformatics analysis. The protein-protein interaction (PPI) network of differently expressed genes (DEGs) between FOLFIRI-resistant and -sensitive CRC patients delivered several potential irinotecan resistance markers: NDUFA2, SDHD, LSM5, DCAF4, COX10 RBM8A, TIMP1, QKI, TGOLN2, and PTGS2. The chosen DEGs were used to validate irinotecan-resistant cell line models, proving their substantial phylogenetic heterogeneity. These results indicated that in vitro models are highly limited and favor different mechanisms than in vivo, patient-derived ones. Thus, cell lines can be perfectly utilized to analyze specific mechanisms on their molecular levels but cannot mirror the complicated drug resistance network observed in patients.

Molecular Mechanisms of Chemoresistance Induced by Cisplatin in NSCLC Cancer Therapy.

Cancer cells utilise several mechanisms to increase their survival and progression as well as their resistance to anticancer therapy: deregulation of growth regulatory pathways by acquiring grow factor independence, immune system suppression, reducing the expression of antigens activating T lymphocyte cells (mimicry), induction of anti-apoptotic signals to counter the action of drugs, activation of several DNA repair mechanisms and driving the active efflux of drugs from the cell cytoplasm, and epigenetic regulation by microRNAs (miRNAs). Because it is commonly diagnosed late, lung cancer remains a major malignancy with a low five-year survival rate; when diagnosed, the cancer is often highly advanced, and the cancer cells may have acquired drug resistance. This review summarises the main mechanisms involved in cisplatin resistance and interactions between cisplatin-resistant cancer cells and the tumour microenvironment. It also analyses changes in the gene expression profile of cisplatin sensitive vs. cisplatin-resistant non-small cell lung cancer (NSCLC) cellular model using the GSE108214 Gene Expression Omnibus database. It describes a protein-protein interaction network that indicates highly dysregulated TP53, MDM2, and CDKN1A genes as they encode the top networking proteins that may be involved in cisplatin tolerance, these all being upregulated in cisplatin-resistant cells. Furthermore, it illustrates the multifactorial nature of cisplatin resistance by examining the diversity of dysregulated pathways present in cisplatin-resistant NSCLC cells based on KEGG pathway analysis.

Mycobacterium tuberculosis Binds Human Serum Amyloid A, and the Interaction Modulates the Colonization of Human Macrophages and the Transcriptional Response of the Pathogen.

As a very successful pathogen with outstanding adaptive properties, Mycobacterium tuberculosis (Mtb) has developed a plethora of sophisticated mechanisms to subvert host defenses and effectively enter and replicate in the harmful environment inside professional phagocytes, namely, macrophages. Here, we demonstrated the binding interaction of Mtb with a major human acute phase protein, namely, serum amyloid A (SAA1), and identified AtpA (Rv1308), ABC (Rv2477c), EspB (Rv3881c), TB 18.6 (Rv2140c), and ThiC (Rv0423c) membrane proteins as mycobacterial effectors responsible for the pathogen-host protein interplay. SAA1-opsonization of Mtb prior to the infection of human macrophages favored bacterial entry into target phagocytes accompanied by a substantial increase in the load of intracellularly multiplying and surviving bacteria. Furthermore, binding of human SAA1 by Mtb resulted in the up- or downregulation of the transcriptional response of tubercle bacilli. The most substantial changes were related to the increased expression level of the genes of two operons encoding mycobacterial transporter systems, namely, mmpL5/mmpS5 (rv0676c), and rv1217c, rv1218c. Therefore, we postulate that during infection, Mtb-SAA1 binding promotes the infection of host macrophages by tubercle bacilli and modulates the functional response of the pathogen.

Implications of ABCC4-Mediated cAMP Eflux for CRC Migration.

Colorectal cancer (CRC) presents significant molecular heterogeneity. The cellular plasticity of epithelial to mesenchymal transition (EMT) is one of the key factors responsible for the heterogeneous nature of metastatic CRC. EMT is an important regulator of ATP binding cassette (ABC) protein expression; these proteins are the active transporters of a broad range of endogenous compounds and anticancer drugs. In our previous studies, we performed a transcriptomic and functional analysis of CRC in the early stages of metastasis induced by the overexpression of Snail, the transcription factor involved in EMT initiation. Interestingly, we found a correlation between the Snail expression and ABCC4 (MRP4) protein upregulation. The relationship between epithelial transition and ABCC4 expression and function in CRC has not been previously defined. In the current study, we propose that the ABCC4 expression changes during EMT and may be differentially regulated in various subpopulations of CRC. We confirmed that ABCC4 upregulation is correlated with the phenotype conversion process in CRC. The analysis of Gene Expression Omnibus (GEO) sets showed that the ABCC4 expression was elevated in CRC patients. The results of a functional study demonstrated that, in CRC, ABCC4 can regulate cell migration in a cyclic nucleotide-dependent manner.

Cathepsin B Is Upregulated and Mediates ECM Degradation in Colon Adenocarcinoma HT29 Cells Overexpressing Snail.

During tumor development and ongoing metastasis the acquisition of mesenchymal cell traits by epithelial carcinoma cells is achieved through a programmed phenotypic shift called the epithelial-to-mesenchymal transition, EMT. EMT contributes to increased cancer cell motility and invasiveness mainly through invadosomes, the adhesion structures that accompany the mesenchymal migration. The invadosomes and their associated proteases restrict protease activity to areas of the cell in direct contact with the ECM, thus precisely controlling cell invasion. Our data prove that Snail-overexpressing HT-29 cells that imitate the phenotype of colon cancer cells in the early stage of the EMT showed an increase in the expression and pericellular activity of cathepsin B. It appears that the pericellular localization of cathepsin B, also observed in colon and rectum adenocarcinoma tissue samples, plays a key role in its function.

Cell Migration Related to MDR-Another Impediment to Effective Chemotherapy?

Multidrug resistance, mediated by members of the ATP-binding cassette (ABC) proteins superfamily, has become one of the biggest obstacles in conquering tumour progression. If the chemotherapy outcome is considered successful, when the primary tumour volume is decreased or completely abolished, modulation of ABC proteins activity is one of the best methods to overcome drug resistance. However, if a positive outcome is represented by no metastasis or, at least, elongation of remission-free time, then the positive effect of ABC proteins inhibition should be compared with the several side effects it causes, which may inflict cancer progression and decrease overall patient health. Clinical trials conducted thus far have shown that the tested ABC modulators add limited or no benefits to cancer patients, as some of them are merely toxic and others induce unwanted drug-drug interactions. Moreover, the inhibition of certain ABC members has been recently indicated as potentially responsible for increased fibroblasts migration. A better understanding of the complex role of ABC proteins in relation to cancer progression may offer novel strategies in cancer therapy.

Proteases Revisited: Roles and Therapeutic Implications in Fibrosis.

Proteases target many substrates, triggering changes in distinct biological processes correlated with cell migration, EMT/EndMT and fibrosis. Extracellular protease activity, demonstrated by secreted and membrane-bound protease forms, leads to ECM degradation, activation of other proteases (i.e., proteolysis of nonactive zymogens), decomposition of cell-cell junctions, release of sequestered growth factors (TGF-ß and VEGF), activation of signal proteins and receptors, degradation of inflammatory inhibitors or inflammation-related proteins, and changes in cell mechanosensing and motility. Intracellular proteases, mainly caspases and cathepsins, modulate lysosome activity and signal transduction pathways. Herein, we discuss the current knowledge on the multidimensional impact of proteases on the development of fibrosis.

HMEC-1 adopt the mixed amoeboid-mesenchymal migration type during EndMT.

The contribution of endothelial cells to scar and fibrotic tissue formation is undisputedly connected to their ability to undergo the endothelial-to-mesenchymal transition (EndMT) towards fibroblast phenotype-resembling cells. The migration model of fibroblasts and fibroblast-resembling cells is still not fully understood. It may be either a Rho/ROCK-independent, an integrin- and MMP-correlated ECM degradation-dependent, a mesenchymal model or Rho/ROCK-dependent, integrin adhesion- and MMP activity-independent, an amoeboid model. Here, we hypothesized that microvascular endothelial cells (HMEC-1) undergoing EndMT adopt an intermediate state of drifting migration model between the mesenchymal and amoeboid protrusive types in the early stages of fibrosis. We characterized the response of HMEC-1 to TGF-ß2, a well-known mediator of EndMT within the microvasculature. We observed that TGF-ß2 induces up to an intermediate mesenchymal phenotype in HMEC-1. In parallel, MMP-2 is upregulated and is responsible for most proteolytic activity. Interestingly, the migration of HMEC-1 undergoing EndMT is dependent on both ECM degradation and invadosome formation associated with MMP-2 proteolytic activity and Rho/ROCK cytoskeleton contraction. In conclusion, the transition from mesenchymal towards amoeboid movement highlights a molecular plasticity mechanism in endothelial cell migration in skin fibrosis.

Neuromedin U is upregulated by Snail at early stages of EMT in HT29 colon cancer cells.

BACKGROUND: The epithelial-mesenchymal transition (EMT) is considered a core process that facilitates the escape of cancer cells from the primary tumor site. The transcription factor Snail was identified as a key regulator of EMT; however, the cascade of regulatory events leading to metastasis remains unknown and new predictive markers of the process are awaited. METHODS: Gene expressions were analysed using real-time PCR, protein level by Western immunoblotting and confocal imaging. The motility of the cells was examined using time-lapse microscopy. Affymetrix GeneChip Human Genome U133 Plus 2.0 analysis was performed to identify transcriptomic changes upon Snail. Snail silencing was performed using siRNA nucleofection. NMU detection was performed by ELISA. RESULTS: HT29 cells overexpressing Snail showed changed morphology, functions and transcriptomic profile indicating EMT induction. Changes in expression of 324 genes previously correlated with cell motility were observed. Neuromedin U was the second highest upregulated gene in HT29-Snail cells. This increase was validated by real-time PCR. Additionally elevated NMU protein was detected by ELISA in cell media. CONCLUSIONS: These results show that Snail in HT29 cells regulates early phenotype conversion towards an intermediate epithelial state. We provided the first evidence that neuromedin U is associated with Snail regulatory function of metastatic induction in colon cancer cells. GENERAL SIGNIFICANCE: We described the global, early transcriptomic changes induced through Snail in HT29 colon cancer cells and suggested NMU involvement in this process.

Mycobacterium tuberculosis AtsG (Rv0296c), GlmU (Rv1018c) and SahH (Rv3248c) Proteins Function as the Human IL-8-Binding Effectors and Contribute to Pathogen Entry into Human Neutrophils.

Mycobacterium tuberculosis is an extremely successful intracellular pathogen that has evolved a broad spectrum of pathogenic mechanisms that enable its manipulation of host defense elements and its survival in the hostile environment inside phagocytes. Cellular influx into the site of mycobacterial entry is mediated by a variety of chemokines, including interleukin-8 (IL-8), and the innate cytokine network is critical for the development of an adaptive immune response and infection control. Using affinity chromatography, liquid chromatography electrospray ionization tandem mass spectrometry and surface plasmon resonance techniques, we identified M. tuberculosis AtsG arylsulphatase, bifunctional glucosamine-1-phosphate acetyltransferase and N-acetylglucosamine-1-phosphate uridyl transferase (GlmU) and S-adenosyl-L-homocysteine hydrolase (SahH) as the pathogen proteins that bind to human IL-8. The interactions of all of the identified proteins (AtsG, GlmU and SahH) with IL-8 were characterized by high binding affinity with KD values of 6.83x10-6 M, 5.24x10-6 M and 7.14x10-10 M, respectively. Furthermore, the construction of Mtb mutant strains overproducing AtsG, GlmU or SahH allowed determination of the contribution of these proteins to mycobacterial entry into human neutrophils. The significantly increased number of intracellularly located bacilli of the overproducing M. tuberculosis mutant strains compared with those of "wild-type" M. tuberculosis and the binding interaction of AtsG, GlmU and SahH proteins with human IL-8 may indicate that these proteins participate in the modulation of the early events of infection with tubercle bacilli and could affect pathogen attachment to target cells.

Leukocytes: The Double-Edged Sword in Fibrosis.

Skin tissue scar formation and fibrosis are often characterized by the increased production and deposition of extracellular matrix components, accompanied by the accumulation of a vast number of myofibroblasts. Scaring is strongly associated with inflammation and wound healing to regain tissue integrity in response to skin tissue injury. However, increased and uncontrolled inflammation, repetitive injury, and individual predisposition might lead to fibrosis, a severe disorder resulting in the formation of dense and stiff tissue that loses the physical properties and physiological functions of normal tissue. Fibrosis is an extremely complicated and multistage process in which bone marrow-derived leukocytes act as both pro- and antifibrotic agents, and therefore, few, if any, effective therapies are available for the most severe and lethal forms of fibrosis. Herein, we discuss the current knowledge on the multidimensional impact of leukocytes on the induction of fibrosis, focusing on skin fibrosis.

Protein disulfide isomerase directly interacts with ß-actin Cys374 and regulates cytoskeleton reorganization.

Recent studies support the role of cysteine oxidation in actin cytoskeleton reorganization during cell adhesion. The aim of this study was to explain whether protein disulfide isomerase (PDI) is responsible for the thiol-disulfide rearrangement in the ß-actin molecule of adhering cells. First, we showed that PDI forms a disulfide-bonded complex with ß-actin with a molecular mass of 110 kDa. Specific interaction of both proteins was demonstrated by a solid phase binding assay, surface plasmon resonance analysis, and immunoprecipitation experiments. Second, using confocal microscopy, we found that both proteins colocalized when spreading MEG-01 cells on fibronectin. Colocalization of PDI and ß-actin could be abolished by the membrane-permeable sulfhydryl blocker, N-ethylmaleimide, by the RGD peptide, and by anti-αIIbß3 antibodies. Consequently, down-regulation of PDI expression by antisense oligonucleotides impaired the spreading of cells and initiated reorganization of the cytoskeleton. Third, because of transfection experiments followed by immunoprecipitation and confocal analysis, we provided evidence that PDI binds to the ß-actin Cys(374) thiol. Formation of the ß-actin-PDI complex was mediated by integrin-dependent signaling in response to the adhesion of cells to the extracellular matrix. Our data suggest that PDI is released from subcellular compartments to the cytosol and translocated toward the periphery of the cell, where it forms a disulfide bond with ß-actin when MEG-01 cells adhere via the αIIbß3 integrin to fibronectin. Thus, PDI appears to regulate cytoskeletal reorganization by the thiol-disulfide exchange in ß-actin via a redox-dependent mechanism.

Thymosin ß4 is rapidly internalized by cells and does not induce intracellular Ca2+ elevation.

Thymosin ß4 (Tß4) is a multifunctional protein that has pleiotropic activities both intracellularly and extracellularly. The mechanisms by which it influences cellular processes such as adhesion, migration, differentiation, or apoptosis are not yet understood. Calcium is a ubiquitous signal molecule that is involved in the regulation of almost all cellular functions. Our data indicate that the release of Ca(2+) from intracellular stores following stimulation of cells with Tß4 does not occur. Interestingly, Tß4 becomes rapidly internalized, supporting the concept that it may express its activities via intracellular receptors.

Matrix metalloproteinase-2 cleavage of the ß1 integrin ectodomain facilitates colon cancer cell motility.

Cancer cell invasion is a key element in metastasis that requires integrins for adhesion/de-adhesion, as well as matrix metalloproteinases (MMPs) for focalized proteolysis. Herein we show that MMP-2 is up-regulated in resected colorectal tumors and degrades ß1 integrins with the release of fragments containing the ß1 I-domain. The ß1 cleavage pattern is similar to that produced by digestion of α5ß1 and α2ß1 with MMP-2. Two such fragments, at 25 and 75 kDa, were identified after immunoprecipitation, with monoclonal antibody BD610468 reacting with the NH(2)-terminal I-like ectodomain followed by SDS-PAGE and microsequencing using electrospray (ISI-Q-TOF-Micromass) spectrometry. Cleavage of the ß1 integrin can be abolished by inhibition of MMP-2 activity; it can be induced by up-regulation of MMP-2 expression, as exemplified by HT29 colon cancer cells transfected with pCMV6-XL5-MMP-2. Co-immunoprecipitation studies of colon cancer cells showed that the ß1 integrin subunit is associated with MMP-2. The MMP-2-mediated shedding of the I-like domain from ß1 integrins resulted in decreased adhesion of colon cancer cells to collagen and fibronectin, thus abolishing their receptivity. Furthermore, such cells showed enhanced motility as evaluated by a "wound healing-like" assay and time-lapse microscopy, indicating their increased invasiveness. Altogether, our data demonstrate that MMP-2 amplifies the motility of colon cancer cells, not only by digesting the extracellular matrix components in the vicinity of cancer cells but also by inactivating their major ß1 integrin receptors.