Inhibition of platelets and tumor cell adhesion by the disintegrin domain of human ADAM9 to collagen I under dynamic flow conditions

The Novel Role of Noncoding RNAs in Modulating Platelet Function: Implications in Activation and Aggregation

It is currently believed that plaque complication, with the consequent superimposed thrombosis, is a key factor in the clinical occurrence of acute coronary syndromes (ACSs). Platelets are major players in this process. Despite the considerable progress made by the new antithrombotic strategies (P2Y12 receptor inhibitors, new oral anticoagulants, thrombin direct inhibitors, etc.) in terms of a reduction in major cardiovascular events, a significant number of patients with previous ACSs treated with these drugs continue to experience events, indicating that the mechanisms of platelet remain largely unknown. In the last decade, our knowledge of platelet pathophysiology has improved. It has been reported that, in response to physiological and pathological stimuli, platelet activation is accompanied by de novo protein synthesis, through a rapid and particularly well-regulated translation of resident mRNAs of megakaryocytic derivation. Although the platelets are anucleate, they indeed contain an important fraction of mRNAs that can be quickly used for protein synthesis following their activation. A better understanding of the pathophysiology of platelet activation and the interaction with the main cellular components of the vascular wall will open up new perspectives in the treatment of the majority of thrombotic disorders, such as ACSs, stroke, and peripheral artery diseases before and after the acute event. In the present review, we will discuss the novel role of noncoding RNAs in modulating platelet function, highlighting the possible implications in activation and aggregation.

The Biochemistry and Physiology of A Disintegrin and Metalloproteinases (ADAMs and ADAM-TSs) in Human Pathologies

Metalloproteinases are a group of proteinases that plays a substantial role in extracellular matrix remodeling and its molecular signaling. Among these metalloproteinases, ADAMs (a disintegrin and metalloproteinases) and ADAM-TSs (ADAMs with thrombospondin domains) have emerged as highly efficient contributors mediating proteolytic processing of various signaling molecules. ADAMs are transmembrane metalloenzymes that facilitate the extracellular domain shedding of membrane-anchored proteins, cytokines, growth factors, ligands, and their receptors and therefore modulate their biological functions. ADAM-TSs are secretory, and soluble extracellular proteinases that mediate the cleavage of non-fibrillar extracellular matrix proteins. ADAMs and ADAM-TSs possess pro-domain, metalloproteinase, disintegrin, and cysteine-rich domains in common, but ADAM-TSs have characteristic thrombospondin motifs instead of the transmembrane domain. Most ADAMs and ADAM-TSs are activated by cleavage of pro-domain via pro-protein convertases at their N-terminus, hence directing them to various signaling pathways. In this article, we are discussing not only the structure and regulation of ADAMs and ADAM-TSs, but also the importance of these metalloproteinases in various human pathophysiological conditions like cardiovascular diseases, colorectal cancer, autoinflammatory diseases (sepsis/rheumatoid arthritis), Alzheimer's disease, proliferative retinopathies, and infectious diseases. Therefore, based on the emerging role of ADAMs and ADAM-TSs in various human pathologies, as summarized in this review, these metalloproteases can be considered as critical therapeutic targets and diagnostic biomarkers.

MicroRNA as Potential Biomarkers of Platelet Function on Antiplatelet Therapy: A Review

MicroRNAs (miRNAs) are small, non-coding RNAs, able to regulate cellular functions by specific gene modifications. Platelets are the major source for circulating miRNAs, with significant regulatory potential on cardiovascular pathophysiology. MiRNAs have been shown to modify the expression of platelet proteins influencing platelet reactivity. Circulating miRNAs can be determined from plasma, serum, or whole blood, and they can be used as diagnostic and prognostic biomarkers of platelet reactivity during antiplatelet therapy as well as novel therapeutic targets in cardiovascular diseases (CVDs). Herein, we review diagnostic and prognostic value of miRNAs levels related to platelet reactivity based on human studies, presenting its interindividual variability as well as the substantial role of genetics. Furthermore, we discuss antiplatelet treatment in the context of miRNAs alterations related to pathways associated with drug response.

microRNAs as promising biomarkers of platelet activity in antiplatelet therapy monitoring

Given the high morbidity and mortality of cardiovascular diseases (CVDs), novel biomarkers for platelet reactivity are urgently needed. Ischemic events in CVDs are causally linked to platelets, small anucleate cells important for hemostasis. The major side-effect of antiplatelet therapy are life-threatening bleeding events. Current platelet function tests are not sufficient in guiding treatment decisions. Platelets host a broad spectrum of microRNAs (miRNAs) and are a major source of cell-free miRNAs in the blood stream. Platelet-related miRNAs have been suggested as biomarkers of platelet activation and assessment of antiplatelet therapy responsiveness. Platelets release miRNAs upon activation, possibly leading to alterations of plasma miRNA levels in conjunction with CVD or inadequate platelet inhibition. Unlike current platelet function tests, which measure platelet activation ex vivo, signatures of platelet-related miRNAs potentially enable the assessment of in vivo platelet reactivity. Evidence suggests that some miRNAs are responsive to platelet inhibition, making them promising biomarker candidates. In this review, we explain the secretion of miRNAs upon platelet activation and discuss the potential use of platelet-related miRNAs as biomarkers for CVD and antiplatelet therapy monitoring, but also highlight remaining gaps in our knowledge and uncertainties regarding clinical utility. We also elaborate on technical issues and limitations concerning plasma miRNA quantification.

Modulation of Immune Responses by Platelet-Derived ADAM10

Platelets have a crucial function in maintaining hemostasis. However, beyond their role in coagulation and thrombus formation, platelets have been implicated to affect various pathophysiological conditions such as infectious diseases, autoimmune disorders, and cancer. It is well-established that platelets aid local cancer growth by providing growth factors or contributing to cancer angiogenesis. In addition, they promote metastasis, among others by facilitation of tumor cell-extravasation and epithelial-to-mesenchymal-like transition as well as protecting metastasizing cancer cells from immunosurveillance. A variety of membrane-bound and soluble platelet-derived factors are involved in these processes, and many aspects of platelet biology in both health and disease are regulated by platelet-associated metalloproteinases and their inhibitors. Platelets synthesize (i) members of the matrix metalloproteinase (MMP) family and also inhibitors of MMPs such as members of the "tissue inhibitor of metalloproteinases" (TIMP) family as well as (ii) members of the "a disintegrin and metalloproteinase" (ADAM) family including ADAM10. Notably, platelet-associated metalloproteinase activity not only influences functions of platelets themselves: platelets can also induce expression and/or release of metalloproteinases e.g., in leukocytes or cancer cells, and ADAMs are emerging as important components by which platelets directly affect other cell types and function. This review outlines the function of metalloproteinases in platelet biology with a focus on ADAM10 and discusses the role of platelet-derived metalloproteinases in the interaction of platelets with components of the immune system and/or cancer cells.

ADAM9 contributes to vascular invasion in pancreatic ductal adenocarcinoma

A disintegrin and a metalloprotease (ADAM)‐9 is a metzincin cell‐surface protease with strongly elevated expression in solid tumors, including pancreatic ductal adenocarcinoma (PDAC). In this study, we performed immunohistochemistry (IHC) of a tissue microarray (TMA) to examine the expression of ADAM9 in a cohort of >100 clinically annotated PDAC cases. We report that ADAM9 is prominently expressed by PDAC tumor cells, and increased ADAM9 expression levels correlate with poor tumor grading (P = 0.027) and the presence of vasculature invasion (P = 0.017). We employed gene expression silencing to generate a loss‐of‐function system for ADAM9 in two established PDAC cell lines. In vitro analysis showed that loss of ADAM9 does not impede cellular proliferation and invasiveness in basement membrane. However, ADAM9 plays a crucial role in mediating cell migration and adhesion to extracellular matrix substrates such as fibronectin, tenascin, and vitronectin. This effect appears to depend on its catalytic activity. In addition, ADAM9 facilitates anchorage‐independent growth. In AsPC1 cells, but not in MiaPaCa‐2 cells, we noted a pronounced yet heterogeneous impact of ADAM9 on the abundance of various integrins, a process that we characterized as post‐translational regulation. Sprout formation of human umbilical vein endothelial cells (HUVECs) is promoted by ADAM9, as examined by transfer of cancer cell conditioned medium; this finding further supports a pro‐angiogenic role of ADAM9 expressed by PDAC cancer cells. Immunoblotting analysis of cancer cell conditioned medium highlighted that ADAM9 regulates the levels of angiogenic factors, including shed heparin‐binding EGF‐like growth factor (HB‐EGF). Finally, we carried out orthotopic seeding of either wild‐type AsPC‐1 cells or AsPC‐1 cells with silenced ADAM9 expression into murine pancreas. In this in vivo setting, ADAM9 was also found to foster angiogenesis without an impact on tumor cell proliferation. In summary, our results characterize ADAM9 as an important regulator in PDAC tumor biology with a strong pro‐angiogenic impact.

Platelet-Enriched MicroRNAs and Cardiovascular Homeostasis

SIGNIFICANCE

Platelets are anucleate blood cells that are involved in hemostasis and thrombosis. Although no longer able to generate ribonucleic acid (RNA) de novo, platelets contain messenger RNA (mRNA), YRNA fragments, and premature microRNAs (miRNAs) that they inherit from megakaryocytes. Recent Advances: Novel sequencing techniques have helped identify the unexpectedly large number of RNA species present in platelets. Throughout their life time, platelets can process the pre-existing pool of premature miRNA to give the fully functional miRNA that can regulate platelet protein expression and function.

CRITICAL ISSUES

Platelets make a major contribution to the circulating miRNA pool but platelet activation can have major consequences on Dicer levels and thus miRNA maturation, which has implications for studies that are focused on screening-stored platelets.

FUTURE DIRECTIONS

It will be important to determine the importance of platelets as donors for miRNA-containing microvesicles that can be taken up and processed by other (particularly vascular) cells, thus contributing to homeostasis as well as disease progression. Antioxid. Redox Signal. 29, 902-921.

MicroRNAs as potential regulators of platelet function and bleeding diatheses

Although a growing number of studies suggest that microRNAs (miRNAs) play a relevant role in platelet biology, their implications in bleeding diatheses are starting to be investigated. Indeed, several studies have shown that alterations in the intracellular levels of highly expressed platelet miRNAs provoke a thrombotic phenotype. On the other hand, primary immune thrombocytopenia (ITP), which is considered the hallmark of acquired bleeding disorders, has been recently associated with altered levels of miRNAs in peripheral blood mononuclear cells, plasma, and platelets. In this review, we will focus on miRNAs that may affect the hemostatic and thrombotic functions of platelets, and we will discuss the different studies that have attempted to associate miRNAs with regulatory mechanisms of ITP.

Loss of ADAM9 expression impairs β1 integrin endocytosis, focal adhesion formation and cancer cell migration

The transmembrane protease ADAM9 is frequently upregulated in human cancers, and it promotes tumour progression in mice. In vitro, ADAM9 regulates cancer cell adhesion and migration by interacting with integrins. However, how ADAM9 modulates integrin functions is not known. We here show that ADAM9 knockdown increases β1 integrin levels through mechanisms that are independent of its protease activity. In ADAM9-silenced cells, adhesion to collagen and fibronectin is reduced, suggesting an altered function of the accumulated integrins. Mechanistically, ADAM9 co-immunoprecipitates with β1 integrin, and both internalization and subsequent degradation of β1 integrin are significantly decreased in ADAM9-silenced cells, with no effect on β1 integrin recycling. Accordingly, the formation of focal adhesions and actin stress fibres in ADAM9-silenced cells is altered, possibly explaining the reduction in cell adhesion and migration in these cells. Taken together, our data provide mechanistic insight into the ADAM9-integrin interaction, demonstrating that ADAM9 regulates β1 integrin endocytosis. Moreover, our findings indicate that the reduced migration of ADAM9-silenced cells is, at least in part, caused by the accumulation and altered activity of β1 integrin at the cell surface.

microRNAs in cardiovascular disease - clinical application

microRNAs (miRNAs) are well-known, powerful regulators of gene expression, and their potential to serve as circulating biomarkers is widely accepted. In cardiovascular disease (CVD), numerous studies have suggested miRNAs as strong circulating biomarkers with high diagnostic as well as prognostic power. In coronary artery disease (CAD) and heart failure (HF), miRNAs have been suggested as reliable biomarkers matching up to established protein-based such as cardiac troponins (cT) or natriuretic peptides. Also, in other CVD entities, miRNAs were identified as surprisingly specific biomarkers - with great potential for clinical applicability, especially in those entities that lack specific protein-based biomarkers such as atrial fibrillation (AF) and acute pulmonary embolism (APE). In this regard, miRNA signatures, comprising a set of miRNAs, yield high sensitivity and specificity. Attempts to utilize miRNAs as therapeutic agents have led to promising results. In this article, we review the clinical applicability of circulating miRNAs in CVD. We are giving an overview of miRNAs as biomarkers in numerous CVD entities to depict the variety of their potential clinical deployment. We illustrate the function of miRNAs by means of single miRNA examples in CVD.

Differentially expressed genes selection via Laplacian regularized low-rank representation method

With the rapid development of DNA microarray technology and next-generation technology, a large number of genomic data were generated. So how to extract more differentially expressed genes from genomic data has become a matter of urgency. Because Low-Rank Representation (LRR) has the high performance in studying low-dimensional subspace structures, it has attracted a chunk of attention in recent years. However, it does not take into consideration the intrinsic geometric structures in data. In this paper, a new method named Laplacian regularized Low-Rank Representation (LLRR) has been proposed and applied on genomic data, which introduces graph regularization into LRR. By taking full advantages of the graph regularization, LLRR method can capture the intrinsic non-linear geometric information among the data. The LLRR method can decomposes the observation matrix of genomic data into a low rank matrix and a sparse matrix through solving an optimization problem. Because the significant genes can be considered as sparse signals, the differentially expressed genes are viewed as the sparse perturbation signals. Therefore, the differentially expressed genes can be selected according to the sparse matrix. Finally, we use the GO tool to analyze the selected genes and compare the P-values with other methods. The results on the simulation data and two real genomic data illustrate that this method outperforms some other methods: in differentially expressed gene selection.

ADAM9 silencing inhibits breast tumor cells transmigration through blood and lymphatic endothelial cells

ADAMs are transmembrane multifunctional proteins that contain disintegrin and metalloprotease domains. ADAMs act in a diverse set of biological processes, including fertilization, inflammatory responses, myogenesis, cell migration, cell proliferation and ectodomain cleavage of membrane proteins. These proteins also have additional functions in pathological processes as cancer and metastasis development. ADAM9 is a member of ADAM protein family that is overexpressed in several types of human carcinomas. The aim of this study was to investigate the role of ADAM9 in hematogenous and lymphatic tumor cell dissemination assisting the development of new therapeutic tools. The role of ADAM9 in the interaction of breast tumor cells (MDA-MB-231) and endothelial cells was studied through RNA silencing. ADAM9 silencing in MDA-MB-231 cells had no influence in expression of several genes related to the metastatic process such as ADAM10, ADAM12, ADAM17, cMYC, MMP9, VEGF-A, VEGF-C, osteopontin and collagen XVII. However, there was a minor decrease in ADAM15 expression but an increase in that of MMP2. Moreover, ADAM9 silencing had no effect in the adhesion of MDA-MB-231 cells to vascular (HMEC-1 and HUVEC) and lymphatic cells (HMVEC-dLyNeo) under flow condition. Nevertheless, siADAM9 in MDA-MB-231 decreased transendothelial cell migration in vitro through HUVEC, HMEC-1 and HMVEC-dLyNeo (50%, 40% and 32% respectively). These results suggest a role for ADAM9 on the extravasation step of the metastatic cascade through both blood and lymph vessels.

Association of MicroRNAs and YRNAs With Platelet Function

RATIONALE

Platelets shed microRNAs (miRNAs). Plasma miRNAs change on platelet inhibition. It is unclear whether plasma miRNA levels correlate with platelet function.

OBJECTIVE

To link small RNAs to platelet reactivity.

METHODS AND RESULTS

Next-generation sequencing of small RNAs in plasma revealed 2 peaks at 22 to 23 and 32 to 33 nucleotides corresponding to miRNAs and YRNAs, respectively. Among YRNAs, predominantly, fragments of RNY4 and RNY5 were detected. Plasma miRNAs and YRNAs were measured in 125 patients with a history of acute coronary syndrome who had undergone detailed assessment of platelet function 30 days after the acute event. Using quantitative real-time polymerase chain reactions, 92 miRNAs were assessed in patients with acute coronary syndrome on different antiplatelet therapies. Key platelet-related miRNAs and YRNAs were correlated with platelet function tests. MiR-223 (rp=0.28; n=121; P=0.002), miR-126 (rp=0.22; n=121; P=0.016), and other abundant platelet miRNAs and YRNAs showed significant positive correlations with the vasodilator-stimulated phosphoprotein phosphorylation assay. YRNAs, miR-126, and miR-223 were also among the small RNAs showing the greatest dependency on platelets and strongly correlated with plasma levels of P-selectin, platelet factor 4, and platelet basic protein in the population-based Bruneck study (n=669). A single-nucleotide polymorphism that facilitates processing of pri-miR-126 to mature miR-126 accounted for a rise in circulating platelet activation markers. Inhibition of miR-126 in mice reduced platelet aggregation. MiR-126 directly and indirectly affects ADAM9 and P2Y12 receptor expression.

CONCLUSIONS

Levels of platelet-related plasma miRNAs and YRNAs correlate with platelet function tests in patients with acute coronary syndrome and platelet activation markers in the general population. Alterations in miR-126 affect platelet reactivity.

Downregulation of Integrins in Cancer Cells and Anti-Platelet Properties Are Involved in Holothurian Glycosaminoglycan-Mediated Disruption of the Interaction of Cancer Cells and Platelets in Hematogenous Metastasis

Activated platelets have been recognized as an accessory character in the cascade of tumor hematogenous metastasis, and intervention of tumor cell attachment to the activated platelets or microemboli formation might be a leading strategy to prevent tumor cells surviving in the blood vessels and sequential metastasis. Recently, we have demonstrated that holothurian glycosaminoglycan (hGAG), a sulfated polysaccharide with potent anticoagulant activity extracted from the sea cucumber Holothuria leucospilota Brandt, was highly efficacious against tumor metastasis. In this study, we identified the potential effects of hGAG on the disruption of interactions of cancer cells and platelets and the underlying mechanisms, which were supported by the following evidence: hGAG (1) inhibited thrombin-induced platelet activation and aggregation, (2) reduced adhesion between platelet and breast cancer cells, and abrogated platelets/cancer cells adhering to fibrinogen, (3) attenuated platelet-cancer cell complex formation (the number and size of aggregates) and (4) suppressed both mRNA and protein levels of β1 and β3 integrins, matrix metalloproteinase (MMP)-2 and MMP-9, while increasing the expression of the MMP inhibitor, tissue inhibitor of metalloproteinase (TIMP)-1 in MDA-MB-231 cells. These results suggested that both the antiplatelet properties and mitigation of the levels of cellular adhesion molecules contributed to the anticancer effects of hGAG, and might thus be exploited for clinical adjuvant therapy to attenuate tumor hematogenous metastasis.

Recombinant disintegrin domain of human ADAM9 inhibits migration and invasion of DU145 prostate tumor cells

One of the most important features of malignant cells is their capacity to invade adjacent tissues and metastasize to distant organs. This process involves the creation, by tumor and stroma cells, of a specific microenvironment, suitable for proliferation, migration and invasion of tumor cells. The ADAM family of proteins has been involved in these processes. This work aimed to investigate the role of the recombinant disintegrin domain of the human ADAM9 (rADAM9D) on the adhesive and mobility properties of DU145 prostate tumor cells. rADAM9D was able to support DU145 cell adhesion, inhibit the migration of DU145 cells, as well as the invasion of this cell line through matrigel in vitro. Overall this work demonstrates that rADAM9D induces specific cellular migratory properties when compared with different constructs having additional domains, specially those of metalloproteinase and cysteine-rich domains. Furthermore, we showed that rADAM9D was able to inhibit cell adhesion, migration and invasion mainly through interacting with α6β1 in DU145 tumor cell line. These results may contribute to the development of new therapeutic strategies for prostate cancer.

ADAM9 disintegrin domain activates human neutrophils through an autocrine circuit involving integrins and CXCR2

ADAM9 is a member of the ADAM family whose expression positively correlates with tumor progression. Besides the metalloprotease activity, ADAM9D interacts with different integrins, modulating cell-adhesion events. Previous studies pointed to an important role for neutrophils in tumor development, as the inhibition of neutrophil migration or depletion of this immune cell impairs tumor growth. However, our understanding of the molecular mechanisms involved in this process, as well as the main key players acting on neutrophils, is very limited. Here, we investigated the possible modulatory effects of ADAM9D on human neutrophil functions. Our results show that ADAM9D promotes neutrophil activation and chemotaxis in a process that depends on the engagement of α_vβ₃ and α₉β₁ integrins and on the activation of PI3K/Akt and MAPK signaling pathway. ADAM9D impairs migration of neutrophils toward fMLP, LTB₄, and IL-8 as classic chemoattractants. This effect is blocked by PTX, a G(i)PCR inhibitor. Furthermore, CXCR2 antagonists RPTX and SB225002 also impaired neutrophil chemotaxis in response to ADAM9D, suggesting a hierarchical cross-talk of integrins with CXCR2. Our results indicate that ADAM9D activates neutrophil functions and may be implicated in the inflammatory events associated with cancer and other disorders.

ADAM9 silencing inhibits breast tumor cell invasion in vitro

ADAM9 (A Disintegrin And Metalloproteinase 9) is a member of the ADAM protein family which contains a disintegrin domain. This protein family plays key roles in many physiological processes, including fertilization, migration, and cell survival. The ADAM proteins have also been implicated in various diseases, including cancer. Specifically, ADAM9 has been suggested to be involved in metastasis. To address this question, we generated ADAM9 knockdown clones of MDA-MB-231 breast tumor cells using silencing RNAs that were tested for cell adhesion, proliferation, migration and invasion assays. In RNAi-mediated ADAM9 silenced MDA-MB-231 cells, the expression of ADAM9 was lower from the third to the sixth day after silencing and inhibited tumor cell invasion in matrigel by approximately 72% when compared to control cells, without affecting cell adhesion, proliferation or migration. In conclusion, the generation of MDA-MB-231 knockdown clones lacking ADAM9 expression inhibited tumor cell invasion in vitro, suggesting that ADAM9 is an important molecule in the processes of invasion and metastasis.

Rac3 induces a molecular pathway triggering breast cancer cell aggressiveness: differences in MDA-MB-231 and MCF-7 breast cancer cell lines

Background

Rho GTPases are involved in cellular functions relevant to cancer. The roles of RhoA and Rac1 have already been established. However, the role of Rac3 in cancer aggressiveness is less well understood.

Methods

This work was conducted to analyze the implication of Rac3 in the aggressiveness of two breast cancer cell lines, MDA-MB-231 and MCF-7: both express Rac3, but MDA-MB-231 expresses more activated RhoA. The effect of Rac3 in cancer cells was also compared with its effect on the non-tumorigenic mammary epithelial cells MCF-10A. We analyzed the consequences of Rac3 depletion by anti-Rac3 siRNA.

Results

Firstly, we analyzed the effects of Rac3 depletion on the breast cancer cells’ aggressiveness. In the invasive MDA-MB-231 cells, Rac3 inhibition caused a marked reduction of both invasion (40%) and cell adhesion to collagen (84%), accompanied by an increase in TNF-induced apoptosis (72%). This indicates that Rac3 is involved in the cancer cells’ aggressiveness. Secondly, we investigated the effects of Rac3 inhibition on the expression and activation of related signaling molecules, including NF-κB and ERK. Cytokine secretion profiles were also analyzed. In the non-invasive MCF-7 line; Rac3 did not influence any of the parameters of aggressiveness.

Conclusions

This discrepancy between the effects of Rac3 knockdown in the two cell lines could be explained as follows: in the MDA-MB-231 line, the Rac3-dependent aggressiveness of the cancer cells is due to the Rac3/ERK-2/NF-κB signaling pathway, which is responsible for MMP-9, interleukin-6, -8 and GRO secretion, as well as the resistance to TNF-induced apoptosis, whereas in the MCF-7 line, this pathway is not functional because of the low expression of NF-κB subunits in these cells. Rac3 may be a potent target for inhibiting aggressive breast cancer.

The role and clinical implications of microRNAs in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is common and one of the most aggressive of all human cancers. Recent studies have indicated that miRNAs, a class of small noncoding RNAs that regulate gene expression post-transcriptionally, directly contribute to HCC by targeting many critical regulatory genes. Several miRNAs are involved in hepatitis B or hepatitis C virus replication and virus-induced changes, whereas others participate in multiple intracellular signaling pathways that modulate apoptosis, cell cycle checkpoints, and growth-factor-stimulated responses. When disturbed, these pathways appear to result in malignant transformation and ultimately HCC development. Recently, miRNAs circulating in the blood have acted as possible early diagnostic markers for HCC. These miRNA also could serve as indicators with respect to drug efficacy and be prognostic in HCC patients. Such biomarkers would assist stratification of HCC patients and help direct personalized therapy. Here, we summarize recent advances regarding the role of miRNAs in HCC development and progression. Our expectation is that these and ongoing studies will contribute to the understanding of the multiple roles of these small noncoding RNAs in liver tumorigenesis.

Chemically modified heparins inhibit fibrinogen-bridged indirect adhesion between tumor cells and platelets

The interaction between platelets and tumor cells is critical for the hematogenous metastasis of tumor cells. We recently reported that fibrinogen was capable of bridging and enhancing the interaction of platelets and tumor cells under conditions of physical shear force. In the present study, we aimed to detect the effects of 8 chemically modified heparins on the binding of fibrinogen to platelets or tumor cells using flow cytometry assays, as well as the fibrinogen-bridged adhesion of platelets and tumor cells using flow chamber assays. The results showed that fibrinogen binds to platelets and tumor cells in a β3 integrin-dependent manner and bridges the adhesion between platelets and tumor cells. Heparin and certain chemically modified heparins, including borohydride-reduced (RO)-, carboxyl-reduced (CR)- and 2-O, 3-O-desulfated (2/3ODS)-heparins, inhibited the β3 integrin-dependent adhesion of fibrinogen to platelets or tumor cells, and consequently blocked the fibrinogen-bridged indirect adhesion of platelets to tumor cells. These data indicate that chemically modified heparins should be potential inhibitors for the fibrinogen-bridged indirect adhesion of platelets and tumor cells, which provides a novel explanation of the anti-adhesion property of heparin and proposes a new anti-metastatic target for cancer treatment.

Blocking αvβ3 integrin by a recombinant RGD disintegrin impairs VEGF signaling in endothelial cells

Vascular endothelial growth factor (VEGF) and αvβ3 integrin are key molecules that actively participate in tumor angiogenesis and metastasis. Some integrin-blocking molecules are currently under clinical trials for cancer and metastasis treatment. However, the mechanism of action of such inhibitors is not completely understood. We have previously demonstrated the anti-angiogenic and anti-metastatic properties of DisBa-01, a recombinant His-tag RGD-disintegrin from Bothrops alternatus snake venom in some experimental models. DisBa-01 blocks αvβ3 integrin binding to vitronectin and inhibits integrin-mediated downstream signaling cascades and cell migration. Here we add some new information on the mechanism of action of DisBa-01 in the tumor microenvironment. DisBa-01 supports the adhesion of fibroblasts and MDA-MB-231 breast cancer cells but it inhibits the adhesion of these cells to type I collagen under flow in high shear conditions, as a simulation of the blood stream. DisBa-01 does not affect the release of VEGF by fibroblasts or breast cancer cells but it strongly decreases the expression of VEGF mRNA and of its receptors, vascular endothelial growth factor receptors 1 and 2 (VEGFR1 and VEGFR2) in endothelial cells. DisBa-01 at nanomolar concentrations also modulates metalloprotease 2 (MMP-2) and 9 (MMP-9) activity, the latter being decreased in fibroblasts and increased in MDA-MB-231 cells. In conclusion, these results demonstrate that αvβ3 integrin inhibitors may induce distinct effects in the cells of the tumor microenvironment, resulting in blockade of angiogenesis by impairing of VEGF signaling and in inhibition of tumor cell motility.

P-selectin-mediated platelet activation promotes adhesion of non-small cell lung carcinoma cells on vascular endothelial cells under flow

Lung cancer is a severe disease threatening human health worldwide. Distant hematogenous metastasis results in poor prognosis and death of lung cancer patients. In the present study, we investigated the effect of circulatory platelets (PLTs) on hematogenous metastasis of non-small cell lung carcinoma (NSCLC). Laser scanning confocal microscopy was employed to assay the expression of P-selectin in lung cancer tissue, paracancerous tissue and distant tissue, respectively. Meanwhile, fluorescence-activated cell sorting (FACS) was used to determine P-selectin activation in peripheral blood. Purified PLTs were co-cultured with A549 cells and human vascular endothelial cells (HuvECs). Subsequently, the formation of PLT-lung cancer cell complexes and their effects on rolling and adhesion of A549 on the surface of vascular endothelium were assayed. Integrin α3, α5, β1, ICAM-1 and VCAM-1 mRNAs and proteins were measured by reverse RT-PCR and western blot analysis, respectively. The expression of P-selectin in lung adenocarcinoma tissue was significantly stronger compared to that in paracancerous and distant tissues. P-selectin activation in peripheral blood in lung adenocarcinoma was markedly enhanced. The rolling rate of A549 on HuvECs was significantly slowed down after co-culture of activated PLTs and A549 cells. The mRNA and protein levels of integrin α3, α5, β1, ICAM-1 and VCAM-1 were significantly increased after the co-culture. In conclusion, the PLT-lung cancer cell complexes protected the lung cancer cells from mechanical injury under blood flow. Furthermore, up-regulated integrin α3, α5, β1 and endothelial cell adhesion molecules ICAM-1 and VCAM-1 promoted the adhesion of A549 on vascular endothelial cells, which may be responsible for hematogenous metastasis of lung cancer.

Snake venom disintegrins and cell migration

Cell migration is a key process for the defense of pluricellular organisms against pathogens, and it involves a set of surface receptors acting in an ordered fashion to contribute directionality to the movement. Among these receptors are the integrins, which connect the cell cytoskeleton to the extracellular matrix components, thus playing a central role in cell migration. Integrin clustering at focal adhesions drives actin polymerization along the cell leading edge, resulting in polarity of cell movement. Therefore, small integrin-binding proteins such as the snake venom disintegrins that inhibit integrin-mediated cell adhesion are expected to inhibit cell migration. Here we review the current knowledge on disintegrin and disintegrin-like protein effects on cell migration and their potential use as pharmacological tools in anti-inflammatory therapy as well as in inhibition of metastatic invasion.

Secreted and membrane-bound isoforms of protease ADAM9 have opposing effects on breast cancer cell migration

Tumor cell migration is mediated by cell-autonomous signaling mechanisms as well as paracrine and autocrine factors secreted by activated stromal cells in the tumor microenvironment. Like other members of the ADAM (a disintegrin and metalloproteinase) family, the integrin-binding metalloproteinase ADAM9 modulates cell-cell and cell-matrix interactions as well as ectodomain shedding of cell surface receptors and ligands, thereby modifying intracellular and extracellular signaling. ADAM9 transcripts are alternatively spliced to express a transmembrane protein (ADAM9-L) and a secreted variant (ADAM9-S). In this study, we show that ADAM9-S promotes breast cancer cell migration in a manner requiring its metalloproteinase activity, whereas ADAM9-L suppresses cell migration independent of its metalloproteinase activity. Suppression of migration by ADAM9-L requires a functional disintegrin domain and integrin binding. Expression analysis revealed that both ADAM9 isoforms are expressed in breast cancer cell lines and tissues. Therefore, relative levels of membrane-tethered and secreted variants of ADAM9 are a key determinant in manifestation of aggressive migratory phenotypes associated with breast cancer progression.

Inhibition of breast cancer cell growth and invasiveness by dual silencing of HER-2 and VEGF

Overexpression of HER-2 accounts for approximately 25% of all breast cancer cases, while 87.7% of HER-2 positive breast cancers are associated with upregulated VEGF. The objective of this study is to explore the combination therapy of blocking HER-2 and VEGF expressions simultaneously using siRNA. This is the first report to examine the effect of dual silencing of HER-2 and VEGF genes on tumor growth and invasiveness. We have designed nine HER-2 siRNAs and ten VEGF siRNAs, and identified potent siRNA which can silence the target gene up to 75-83.5%. The most potent HER-2 and VEGF siRNAs were used to conduct functional studies in HER-2 positive breast cancer cells. Tumor invasiveness properties including cell morphology change, in vitro migration, cell spreading, and adhesion to ECM were evaluated. In addition, cell proliferation and apoptosis were examined after the siRNA treatment. Our data demonstrated for the first time that HER-2 siRNA could inhibit cell migration and invasion abilities. Combination of HER-2 and VEGF siRNAs exhibited synergistic silencing effect on VEGF. Both HER-2 siRNA and VEGF siRNA showed significant inhibition on cell migration and proliferation. HER-2 siRNA also demonstrated dramatic suppression on cell spreading and adhesion to ECM, as well as induction of apoptosis. Dual silencing of HER-2 and VEGF exhibited significant cell morphology change, and substantial suppression on migration, spreading, cell adhesion, and proliferation. Our observations suggested that HER-2 positive breast cancer may be more effectively treated by dual inhibition of HER-2 and VEGF gene expressions using siRNA.