Targeting tumor cell motility to prevent metastasis

Uveal Melanoma Metastasis Models

Metastatic disease is the leading cause of death among patients with uveal melanoma. Treatment options for patients with clinically disseminated disease are usually unsuccessful. In vitro and in vivo models are important tools to investigate the pathogenesis of metastatic uveal melanomas and develop treatments for the metastases. In vitro experimental approaches focusing on cell invasion/migration which mimic the steps of the complex metastatic process may also be used for the identification of potential anti-invasion/migration drugs that may inhibit the spreading of tumor cells or the development of metastases. The effects of these drugs must subsequently be confirmed in reliable in vivo models before entering the clinical trial phase. Several models of intraocular melanoma with metastases in rodents and rabbits are currently being used. Most experimental models of uveal melanoma metastases require injection or implantation of melanoma cells into orthotopic locations, including into the liver, spleen, tail vein, or the left ventricle of the heart, in order to mimic the metastatic process.

P311 modulates hepatic stellate cells migration

BACKGROUND & AIMS

Liver fibrosis is induced by the accumulation of extracellular matrix, deposited mainly by activated hepatic stellate cells (HSCs). One key characteristic of stellate cell activation is the directional migration to the site of injury during the wound-healing process. P311 is a protein that has been shown to play a role in migration and we aimed to study a possible role for this protein during stellate cell migration.

METHODS

Mouse stellate cells were isolated and cultured in vitro to investigate P311 protein and gene expression during HSC activation by immunocytochemistry and RT-qPCR respectively. Expression of P311 during in vivo activation was evaluated in CCl4 and bile duct ligation-induced liver fibrosis. Production of reactive oxygen species was determined using the fluorescent probe DCFH-DA. By siRNA-mediated knockdown of P311, we investigated a possible effect on proliferation by incorporation of EdU and on migration by Boyden chamber assays.

RESULTS

P311 gene expression was increased during both in vitro and in vivo activation of HSCs. siRNA-mediated knockdown led to a decrease in reactive oxygen production and cell proliferation. Migration induced by different chemokines, such as PDGF-bb and MCP-1 was inhibited by knockdown of P311.

CONCLUSIONS

P311 is central to reactive oxygen species-mediated HSC migration induced by different chemokines.

Cigarette smoke induces cell motility via platelet-activating factor accumulation in breast cancer cells: a potential mechanism for metastatic disease

Most cancer deaths are a result of metastasis rather than the primary tumor. Although cigarette smoking has been determined as a risk factor for several cancers, its role in metastasis has not been studied in detail. We propose that cigarette smoking contributes to metastatic disease via inhibition of breast cancer cell platelet-activating factor acetylhydrolase (PAF-AH), resulting in PAF accumulation and a subsequent increase in cell motility. We studied several breast cell lines, including immortalized mammary epithelial cells (MCF-10A), luminal A hormone positive MCF-7, basal-like triple negative MDA-MB-468, and claudin-low triple-negative highly metastatic MDA-MB-231 breast tumor cells. We exposed cells to cigarette smoke extract (CSE) for up to 48 h. CSE inhibited PAF-AH activity, increased PAF accumulation, and increased cell motility in MDA-MB-231 metastatic triple negative breast cancer cells. The calcium-independent phospholipase A₂ (iPLA₂) inhibitor, (S) bromoenol lactone ((S)-BEL) was used to prevent the accumulation of PAF and further prevented the increase in cell motility seen previously when cells were exposed to CSE. Thus, iPLA₂ or PAF may represent a therapeutic target to manage metastatic disease, particularly in triple-negative breast cancer patients who smoke.

Conditioned medium from mesenchymal stem cells enhances the migration of hepatoma cells through CXCR4 up-regulation and F-actin remodeling

Interactions between tumors and mesenchymal stem cells (MSCs) can regulate cancer cell behavior and cancer progression. Rat bone marrow-derived MSCs (rMSCs) were isolated and purified by Percoll density gradient centrifugation. Conditioned media from rMSCs (MSC-CM) was prepared, and its role in cancer cell migration and the underlying molecular mechanism were investigated. MSC-CM increased the migration and up-regulated the expression of CXC chemokine receptor 4 (CXCR4) in rat hepatoma cells (CBRH-7919). F-actin remodeling was observed, and the Young's modulus was decreased in CBRH-7919 cells. A CXCR4 inhibitor suppressed the MSC-CM-induced CXCR4 expression and migration, restored the decrease in the Young's modulus and disrupted the formation of F-actin. MSC-CM thus promotes CBRH-7919 cell migration by lessening cell stiffness and increasing F-actin formation through up-regulation of CXCR4 expression. MSC-CM may therefore have a positive impact on cancer metastases and underlines a potential safety issue associated with clinical applications of MSCs.

Microfabricated Systems and Assays for Studying the Cytoskeletal Organization, Micromechanics, and Motility Patterns of Cancerous Cells

Cell motions are driven by coordinated actions of the intracellular cytoskeleton - actin, microtubules (MTs) and substrate/focal adhesions (FAs). This coordination is altered in metastatic cancer cells resulting in deregulated and increased cellular motility. Microfabrication tools, including photolithography, micromolding, microcontact printing, wet stamping and microfluidic devices have emerged as a powerful set of experimental tools with which to probe and define the differences in cytoskeleton organization/dynamics and cell motility patterns in non-metastatic and metastatic cancer cells. In this review, we discuss four categories of microfabricated systems: (i) micropatterned substrates for studying of cell motility sub-processes (for example, MT targeting of FAs or cell polarization); (ii) systems for studying cell mechanical properties, (iii) systems for probing overall cell motility patterns within challenging geometric confines relevant to metastasis (for example, linear and ratchet geometries), and (iv) microfluidic devices that incorporate co-cultures of multiple cells types and chemical gradients to mimic in vivo intravasation/extravasation steps of metastasis. Together, these systems allow for creating controlled microenvironments that not only mimic complex soft tissues, but are also compatible with live cell high-resolution imaging and quantitative analysis of single cell behavior.

Control of cell migration through mRNA localization and local translation

Cell migration plays an important role in many normal and pathological functions such as development, wound healing, immune defense, and tumor metastasis. Polarized migrating cells exhibit asymmetric distribution of many cytoskeletal proteins, which is believed to be critical for establishing and maintaining cell polarity and directional cell migration. To target these proteins to the site of function, cells use a variety of mechanisms such as protein transport and messenger RNA (mRNA) localization-mediated local protein synthesis. In contrast to the former which is intensively investigated and relatively well understood, the latter has been understudied and relatively poorly understood. However, recent advances in the study of mRNA localization and local translation have demonstrated that mRNA localization and local translation are specific and effective ways for protein localization and are crucial for embryo development, neuronal function, and many other cellular processes. There are excellent reviews on mRNA localization, transport, and translation during development and other cellular processes. This review will focus on mRNA localization-mediated local protein biogenesis and its impact on somatic cell migration.

Motility of select ovarian cancer cell lines: effect of extra-cellular matrix proteins and the involvement of PAK2

The interaction between tumor cells and extracellular matrix (ECM) proteins influences cell migration and the invasive behavior of cancer cells. In this study, we provide experimental evidence that collagen I and fibronectin affect ovarian cancer cell migration. In vitro wound healing assays and transwell migration assays were used to measure both total wound healing and directionality of individually migrating OV2008 and C13 ovarian cancer cells on glass, collagen I and fibronectin. Involvement of p21-activated kinase 2 (Pak2) in the motility of these cell lines was investigated using a chemical inhibitor as well as siRNA transfection. Culturing ovarian cancer cells on collagen type I (COLL) increased the migratory ability of OV2008 and C13 cells by increasing the directional migration of cells. In contrast, fibronectin (FN) decreased the migratory ability of OV2008 cells by reducing their ability to migrate directionally. When both cell lines are cultured on COLL and treated with increasing concentrations of a PAK inhibitor (IPA-3), there is a dose-dependent response such that there is a decrease in migration with an increase in inhibitor concentration. Further experiments utilizing PAK2 knockdown via siRNA transfection demonstrated significantly reduced migration of OV2008 cells on COLL as compared to those receiving control siRNA. In conclusion, our results indicate that FN and COLL affect the motility of the selected ovarian cancer cells lines and the effect of COLL is likely mediated, at least in part, by PAK2. A better understanding of the molecular events that contribute to tumor invasion and metastasis is crucial for developing novel treatment strategies to improve the long-term survival of women with ovarian cancer. As PAK2 is involved in motility, it should be further explored as a pro-metastatic gene in ovarian cancer.

Nanotechnology applications in diagnosis and treatment of metastasis

The lethality of solid tumors is in large part dependent on their ability to metastasize through hematologic and lymphatic transport pathways. The dissemination of cancer cells from the primary tumor to undergo transport, their ability to survive in transit and then to subsequently form metastatic colonies, is facilitated by a complex concert of signaling pathways and cell–cell and cell–matrix interactions. Elucidating these mechanistic components is highly valuable to guide the development of technologies for efficiently detecting and treating metastasis. To this end, in recent years nanotechnology approaches have provided several unique detection, characterization and treatment strategies. The current article will review these approaches to discuss their promise and challenges, specifically in metastatic cancer, above and beyond the usual nanomedicine applications in cancer therapy.

Extra virgin olive oil phenols suppress migration and invasion of T24 human bladder cancer cells through modulation of matrix metalloproteinase-2

The consumption of extra virgin olive oil (EVOO), a common dietary habit of the Mediterranean people, seems to be related to a lower incidence of certain types of cancer including bladder neoplasm. Metastases are the major cause of bladder cancer-related deaths and targeting cell motility has been proposed as a therapeutic strategy to prevent cancer spread. This study aimed to investigate the potential antimetastatic effect of total phenols extracted from EVOO against the human transitional bladder carcinoma cell line T24. We also aimed at verifying that EVOO extract exerts cytotoxic effect on tumor cells without affecting normal urothelial fibroblasts. Our results show that EVOO extract can significantly inhibit the proliferation and motility of T24 bladder cells in a dose-dependent manner. In the same experimental conditions fibroblast proliferation and motility were not significantly modified. Furthermore the enzymatic activity of MMP-2 was inhibited at nontoxic EVOO extract doses only in T24 cells. The qRT-PCR revealed a decrease of the MMP-2 expression and a simultaneous increase of the tissue inhibitors of metalloproteinases expression. Our results may support the epidemiological evidences that link olive oil consumption to health benefits and may represent a starting point for the development of new anticancer strategies.

Diosgenin inhibits the migration of human breast cancer MDA-MB-231 cells by suppressing Vav2 activity

Diosgenin, a naturally occurring steroidal saponin, possess tumor therapeutic potential. However, the effect of diosgenin on cancer metastasis remains poorly understood. In this study, we performed in vitro experiments to investigate the inhibitory activity of diosgenin on human breast cancer MDA-MB-231 cell migration, and reveal the possible mechanism. Diosgenin caused a marked inhibition of cell migration in MDA-MB-231 cell by transwell assay. In addition, diosgenin significantly impacted MDA-MB-231 cell migratory behavior under real-time observation. We also found diosgenin significantly inhibited actin polymerization, Vav2 phosphorylation and Cdc42 activation, which might be, at least in part, attributed to the anti-metastatic potential of diosgenin. These findings reveal a new therapeutic potential of diosgenin for human breast cancer metastasis therapy.

Metastasis as a therapeutic target in prostate cancer: a conceptual framework

Metastasis is the main cause of prostate cancer-associated deaths. While significant progerss has been made in the treatment of primary tumors, efficent therapies that target the metastatic spread of prostate cancer are far from clinical reality. To efficiently treat cancer we need be able to impede its spread. Unfortunately, the majority of current therapeutics approved to treat metastatic cancer were originally selected based on their ability to inhibit primary tumor growth. This inherent flaw precluded these therapies from efficiently targeting the development of secondary metastatic lesions, a process that is distinct from that of primary tumor progression. In this review we will summarize the conceptual, cellular and molecular targets that should be considered to design effective anti-metastatic therapies.

Screening and functional analysis of a differential protein profile of human breast cancer

To improve the understanding of the enriched functions of proteins and to identify potential biomarkers in human breast cancer, the present study constructed a differentially expressed protein profile by screening immunohistochemistry maps of human breast cancer proteins. A total of 1,688 proteins were found to be differentially expressed in human breast cancer, including 773 upregulated and 915 downregulated proteins. Of these proteins, secreted and membrane proteins were screened and clustered, and more enriched biological functions and pathways were presented in the upregulated protein profiles. Furthermore, altered serum levels of peroxiredoxin (PRDX)2, PRDX6, cathepsin (CTS)B and CTSD were detected by ELISA assay. The present study provides a novel global mapping of potential breast cancer biomarkers that could be used as background to identify the altered pathways in human breast cancer, as well as potential cancer targets.

P300 binds to and acetylates MTA2 to promote colorectal cancer cells growth

MTA2 is a member of metastasis associated family, which is highly expressed in several solid tumors and associated with tumor cells migration and invasion. Here, we report that MTA2 is acetylated at K152 and histone acetyltransferase p300 binds to and acetylates MTA2. Furthermore, mutation of the MTA2 acetylation site inhibits the growth of colorectal cancer cells and migration and invasion of Rat1 fibroblasts. These results reveal a novel post-translational regulation of MTA2 by the way of p300-dependent acetylation, which is important for tumor cells growth and migration and provides a potential target for clinical cancer research.

ALCAM/CD166 is a TGF-β-responsive marker and functional regulator of prostate cancer metastasis to bone

The dissemination of prostate cancer to bone is a common, incurable aspect of advanced disease. Prevention and treatment of this terminal phase of prostate cancer requires improved molecular understanding of the process as well as markers indicative of molecular progression. Through biochemical analyses and loss-of-function in vivo studies, we demonstrate that the cell adhesion molecule, activated leukocyte cell adhesion molecule (ALCAM), is actively shed from metastatic prostate cancer cells by the sheddase ADAM17 in response to TGF-β. Not only is this posttranslational modification of ALCAM a marker of prostate cancer progression, the molecule is also required for effective metastasis to bone. Biochemical analysis of prostate cancer cell lines reveals that ALCAM expression and shedding is elevated in response to TGF-β signaling. Both in vitro and in vivo shedding is mediated by ADAM17. Longitudinal analysis of circulating ALCAM in tumor-bearing mice revealed that shedding of tumor, but not host-derived ALCAM is elevated during growth of the cancer. Gene-specific knockdown of ALCAM in bone-metastatic PC3 cells greatly diminished both skeletal dissemination and tumor growth in bone. The reduced growth of ALCAM knockdown cells corresponded to an increase in apoptosis (caspase-3) and decreased proliferation (Ki67). Together, these data demonstrate that the ALCAM is both a functional regulator as well as marker of prostate cancer progression.

Shape in migration: quantitative image analysis of migrating chemoresistant HCT-8 colon cancer cells

Unsuccessful cytotoxic anticancer treatments may contribute to tumor morphologic instability and consequent tissue invasion, promoting the selection of a more malignant phenotype. Indeed, morphological changes have been demonstrated to be more pronounced in strongly vs. weakly metastatic cells. By means of normalized bending energy, we have previously quantitatively defined the link between cell shape modifications and the acquisition of a more malignant phenotype by 5-FU-resistant colon cancer cells (HCT-8FUres). Such changes were significantly correlated with an increase in motility speed. Herein, we propose a method to quantitatively analyze the shape of wild and chemoresistant HCT-8 migration front cells during wound healing assay. We evaluated the reliability of parameters (area/perimeter ratio [A/p], circularity, roundness, fractal dimension, and solidity) in describing the biological behavior of the two cell lines, enabling hence in distinguishing the chemoresistant line from the other one. We found solidity index the parameter that better described the difference between chemoresistant and wild cells. Moreover, solidity is able to capture the differences between chemoresistant and wild cells at each time point of the migration process. Indeed, motility speed was found to be inversely correlated with solidity, a quantitative index of cell deformability. Deformability is an outstanding hallmark of the process leading to metastatic spread; consequently, solidity may be considered a marker of acquired metastatic property.

MTA2 promotes gastric cancer cells invasion and is transcriptionally regulated by Sp1

Background

MTA2 gene belongs to metastasis associated family, and is highly expressed in some solid tumors, including gastric cancer. Its biological function in gastric cancer is currently undefined.

Methods

Metastasis-associated tumor gene family 2 (MTA2) and transcription factor specificity protein 1 (Sp1) expression were detected in 127 gastric cancer samples by immunohistochemistry staining. SGC-7901 and AGS gastric cancer cell lines transfected by MTA2 shRNA was used for biological function investigation. Binding and regulation activities of Sp1 on MTA2 promoter were investigated by chromatin immunoprecipitation and luciferase reporter gene.

Results

The expression rate of MTA2 in gastric cancer tissues was 55.9% (71/127), and its expression was closely related to the depth of tumor invasion, lymph nodes metastasis, and TNM staging. MTA2 knockdown in human SGC-7901 and AGS gastric cancer cells significantly inhibited migration and invasion in vitro, and disrupted structure of cytoskeleton. MTA2 knockdown also attenuated xenografts growth and lung metastasis in nude mice model. MTA2 expression was positively correlated with transcription factor Sp1 in gastric cancer tissues (r = 0.326, P < 0.001). Sp1 bound to human MTA2 gene promoter at region from -1043 bp to -843 bp. Transcriptional activity of MTA2 promoter could be enhanced by Sp1 overexpression.

Conclusions

MTA2 knockdown impairs invasion and metastasis of gastric cancer cells, and attenuates xenografts growth in vivo. Sp1 regulates MTA2 expression at transcriptional level.

Interaction between p68 RNA helicase and Ca2+-calmodulin promotes cell migration and metastasis

p68 RNA helicase is a prototypical RNA helicase. Here we present evidence to show that, by interacting with Ca-calmodulin (CaM), p68 plays a role in cancer metastasis and cell migration. A peptide fragment that spans the IQ motif of p68 strongly inhibits cancer metastasis in two different animal models. The peptide interrupts p68 and CaM interaction and inhibits cell migration. Our results demonstrate that the p68-CaM interaction is essential for the formation of lamellipodia and filopodia in migrating cells. p68 interacts with microtubules in the presence of CaM. Our experiments show that interaction with microtubules stimulates p68 ATPase activity. Further, microtubule gliding assays demonstrate that p68, in the presence of CaM, can function as a microtubule motor. This motor activity may allow p68 to transport CaM to the leading edge of migrating cells.

Downregulation of RhoGDIα increased migration and invasion of ER (+) MCF7 and ER (-) MDA-MB-231 breast cancer cells

Rho GDP dissociation inhibitors (RhoGDIs) can inhibit cell motility, invasion, and metastasis in cancer by inactivating the RhoGTPases. A member of RhoGDI family has been consistently shown to interact with estrogen receptor (ER), and change its transcriptional activity. ER is a receptor known to be inversely correlated with cell motility and invasion in breast cancer. The consequence of RhoGDIα activity on migration and invasion of ER (+) and ER (-) breast cancers is not clear. The aim of our study was to investigate the possible opposing effect of RhoGDIα on the migration and invasion of ER (+) MCF7 and ER (-) MDA-MB-231 breast cancer cells. RhoGDIα was downregulated using short interfering RNA (siRNA) and upregulated using GFP-tagged ORF clone of RhoGDIα, and their ability for migration and invasion was assayed using transwell chambers. It was found that the silencing of RhoGDIα in MCF7 and MDA-MB-231 cells significantly increased migration and invasion of these cells into the lower surface of porous membrane of the chambers. Overexpression of RhoGDIα in MCF7 cells suppressed their migration and invasion, but no significant effect was found on MDA-MB-231 cells. Our results indicate that the downregulation of RhoGDIα similarly affects the in vitro migration and invasion of ER (+) MCF7 and ER (-) MDA-MB-231 cells. However, our assays are differently affected by the upregulation of RhoGDIα in these two cell lines and this may be due to the differences in ER expression, primary invasive ability and/or other molecules between these two cell line models which warrant further investigation.

Established and novel methods of interrogating two-dimensional cell migration

The regulation of cell motility is central to living systems. Consequently, cell migration assays are some of the most frequently used in vitro assays. This article provides a comprehensive, detailed review of in vitro cell migration assays both currently in use and possible with existing technology. Emphasis is given to two-dimensional migration assays using densely organized cells such as the scratch assay. Assays are compared and categorized in an outline format according to their primary biological readout and physical parameters. The individual benefits of the various methods and quantification strategies are also discussed. This review provides an in-depth, structured overview of in vitro cell migration assays as a means of enabling the reader to make informed decisions among the growing number of options available for their specific cell migration application.

A platelet-mimetic paradigm for metastasis-targeted nanomedicine platforms

There is compelling evidence that, beyond their traditional role in hemostasis and thrombosis, platelets play a significant role in mediating hematologic mechanisms of tumor metastasis by directly and indirectly interacting with pro-metastatic cancer cells. With this rationale, we hypothesized that platelets can be an effective paradigm to develop nanomedicine platforms that utilize platelet-mimetic interaction mechanisms for targeted diagnosis and therapy of metastatic cancer cells. Here we report on our investigation of the development of nanoconstructs that interact with metastatic cancer cells via platelet-mimetic heteromultivalent ligand-receptor pathways. For our studies, pro-metastatic human breast cancer cell line MDA-MB-231 was studied for its surface expression of platelet-interactive receptors, in comparison to another low-metastatic human breast cancer cell line, MCF-7. Certain platelet-interactive receptors were found to be significantly overexpressed on the MDA-MB-231 cells, and these cells showed significantly enhanced binding interactions with active platelets compared to MCF-7 cells. Based upon these observations, two specific receptor interactions were selected, and corresponding ligands were engineered onto the surface of liposomes as model nanoconstructs, to enable platelet-mimetic binding to the cancer cells. Our model platelet-mimetic liposomal constructs showed enhanced targeting and attachment of MDA-MB-231 cells compared to the MCF-7 cells. These results demonstrate the promise of utilizing platelet-mimetic constructs in modifying nanovehicle constructs for metastasis-targeted drug as well as modifying surfaces for ex-vivo cell enrichment diagnostic technologies.

Tumor spheroid-based migration assays for evaluation of therapeutic agents

Cell migration is a key hallmark of malignant cells that contributes to the progression of cancers from a primary, localized mass to an invasive and/or metastatic phenotype. Traditional methods for the evaluation of tumor cell migration in vitro generally employ two-dimensional (2D), homogeneous cultures that do not take into account tumor heterogeneity, three-dimensional (3D) cell-cell contacts between tumor and/or host cells or interactions with extracellular matrix proteins. Here we describe a 3D tumor spheroid-based migration assay which more accurately reflects the solid tumor microenvironment and can accommodate both extracellular matrix and host cell interactions. It is a rapid and highly reproducible 96-well plate-based technique and we demonstrate its utility for the evaluation of therapeutic agents/drugs with anti-migratory properties.

Two-dimensional vs. three-dimensional in vitro tumor migration and invasion assays

Motility and invasion are key hallmarks that distinguish benign from malignant tumors, enabling cells to cross tissue boundaries, disseminate in blood and lymph and establish metastases at distant sites. Similar properties are also utilized by activated endothelial cells during tumor-induced angiogenesis. It is now appreciated that these processes might provide a rich source of novel molecular targets with the potential for inhibitors to restrain both metastasis and neoangiogenesis. Such therapeutic strategies require assays that can rapidly and quantitatively measure cell movement and the ability to traverse physiological barriers. The need for high-throughput, however, must be balanced by assay designs that accommodate, as far as possible, the complexity of the in vivo tumor microenvironment. This chapter aims to give an overview of some commonly used migration and invasion assays to aid in the selection of a balanced portfolio of techniques for the rapid and accurate evaluation of novel therapeutic agents.

GTSE1 is a microtubule plus-end tracking protein that regulates EB1-dependent cell migration

The regulation of cell migration is a highly complex process that is often compromised when cancer cells become metastatic. The microtubule cytoskeleton is necessary for cell migration, but how microtubules and microtubule-associated proteins regulate multiple pathways promoting cell migration remains unclear. Microtubule plus-end binding proteins (+TIPs) are emerging as important players in many cellular functions, including cell migration. Here we identify a +TIP, GTSE1, that promotes cell migration. GTSE1 accumulates at growing microtubule plus ends through interaction with the EB1+TIP. The EB1-dependent +TIP activity of GTSE1 is required for cell migration, as well as for microtubule-dependent disassembly of focal adhesions. GTSE1 protein levels determine the migratory capacity of both nontransformed and breast cancer cell lines. In breast cancers, increased GTSE1 expression correlates with invasive potential, tumor stage, and time to distant metastasis, suggesting that misregulation of GTSE1 expression could be associated with increased invasive potential.

The role of microtubules and their dynamics in cell migration

Although microtubules have long been implicated in cell locomotion, the mechanism of their involvement remains controversial. Most studies have concluded that microtubules play a positive role by regulating actin polymerization, transporting membrane vesicles to the leading edge, and/or facilitating the turnover of adhesion plaques. Here we used wild-type and mutant CHO cell lines with alterations in tubulin to demonstrate that microtubules can also act to restrain cell motility. Tubulin mutations or low concentrations of drugs that suppress microtubule dynamics without affecting the amount of microtubule polymer inhibited the rate of migration by preventing microtubule reorganization in the trailing portion of the cells where the more dynamic microtubules are normally found. Under these conditions, cells along the edge of a wound still extended lamellipodia and elongated toward the wound but were inhibited in their ability to retract their tails, thus retarding forward progress. The idea that microtubules normally act to restrain cell locomotion was confirmed by treating cells with high concentrations of nocodazole to depolymerize the microtubule network. In the absence of microtubules, wild-type CHO and HeLa cells could still move at near normal speeds, but the movement became more random. We conclude that microtubules act both to restrain cell movement and to establish directionality.

The mechanics of metastasis: insights from a computational model

Although it may seem obvious that mechanical forces are required to drive metastatic cell movements, understanding of the mechanical aspects of metastasis has lagged far behind genetic and biochemical knowledge. The goal of this study is to learn about the mechanics of metastasis using a cell-based finite element model that proved useful for advancing knowledge about the forces that drive embryonic cell and tissue movements. Metastasis, the predominant cause of cancer-related deaths, involves a series of mechanical events in which one or more cells dissociate from a primary tumour, migrate through normal tissue, traverse in and out of a multi-layer circulatory system vessel and resettle. The present work focuses on the dissemination steps, from dissociation to circulation. The model shows that certain surface tension relationships must be satisfied for cancerous cells to dissociate from a primary tumour and that these equations are analogous to those that govern dissociation of embryonic cells. For a dissociated cell to then migrate by invadopodium extension and contraction and exhibit the shapes seen in experiments, the invadopodium must generate a contraction equal to approximately twice that produced by the interfacial tension associated with surrounding cells. Intravasation through the wall of a vessel is governed by relationships akin to those in the previous two steps, while release from the vessel wall is governed by equations that involve surface and interfacial tensions. The model raises a number of potential research questions. It also identifies how specific mechanical properties and the sub-cellular structural components that give rise to them might be changed so as to thwart particular metastatic steps and thereby block the spread of cancer.

Magnetically attachable stencils and the non-destructive analysis of the contribution made by the underlying matrix to cell migration

Cell migration is controlled by the integration of numerous distinct components. Consequently, the analysis of cell migration is advancing towards comprehensive, multifaceted in vitro models. To accurately evaluate the contribution of an underlying substrate to cell motility in complex cellular environments we developed a migration assay using magnetically attachable stencils (MAts). When attached to a culture surface, MAts create a defined void in the cell monolayer without disrupting the cells or damaging the underlying substrate. Quantitative analysis of migration into this void reveals the substrate's contribution to migration. The magnetically-guided placement of a microfabricated stencil allows for full experimental control of the substrate on which migration is analyzed. MAts enable the evaluation of intact, defined matrix, and make it possible to analyze migration on unique surfaces such as micropatterned proteins, nano-textured surfaces, and pliable hydrogels. These studies also revealed that mechanical disruption, including the damage that occurs during scratch assays, diminishes migration and confounds the analysis of individual cell behavior. Analysis of migration on increasingly complex biomaterials reveals that the contribution of the underlying matrix depends not only on its molecular composition but also its organization and the context in which it is presented.

LAP2 is widely overexpressed in diverse digestive tract cancers and regulates motility of cancer cells

Background

Lamina-associated polypeptides 2 (LAP2) is a nuclear protein that connects the nuclear lamina with chromatin. Although its critical roles in genetic disorders and hematopoietic malignancies have been described, its expression and roles in digestive tract cancers have been poorly characterized.

Methods

To examine the expression of LAP2 in patient tissues, we performed immunohistochemistry and real-time PCR. To examine motility of cancer cells, we employed Boyden chamber, wound healing and Matrigel invasion assays. To reveal its roles in metastasis in vivo, we used a liver metastasis xenograft model. To investigate the underlying mechanism, a cDNA microarray was conducted.

Results

Immunohistochemistry in patient tissues showed widespread expression of LAP2 in diverse digestive tract cancers including stomach, pancreas, liver, and bile duct cancers. Real-time PCR confirmed that LAP2β is over-expressed in gastric cancer tissues. Knockdown of LAP2β did not affect proliferation of most digestive tract cancer cells except pancreatic cancer cells. However, knockdown of LAP2β decreased motility of all tested cancer cells. Moreover, overexpression of LAP2β increased motility of gastric and pancreatic cancer cells. In the liver metastasis xenograft model, LAP2β increased metastatic efficacy of gastric cancer cells and mortality in tested mice. cDNA microarrays showed the possibility that myristoylated alanine-rich C kinase substrate (MARCKS) and interleukin6 (IL6) may mediate LAP2β-regulated motility of cancer cells.

Conclusions

From the above results, we conclude that LAP2 is widely overexpressed in diverse digestive tract cancers and LAP2β regulates motility of cancer cells and suggest that LAP2β may have utility for diagnostics and therapeutics in digestive tract cancers.

Silencing of Eps8 blocks migration and invasion in human glioblastoma cell lines

Glioblastoma multiforme (GBM) is the most malignant human primary brain tumor, and its infiltrative nature represents the leading cause for the failure of therapies and tumor recurrences. It is therefore crucial the knowledge of the molecular mechanisms underlying GBM invasion to identify novel therapeutic targets to limit motility. In this study, we evaluated the role of Epidermal growth factor receptor Pathway Substrate 8 (Eps8), a crucial regulator of the actin cytoskeleton dynamics accompanying cell motility and invasion, in GBM migration and invasiveness. We found that silencing of the protein by small interfering RNAs (siRNAs) abrogated the migratory and invasive capacity of three different human GBM cell lines both in 2-dimensional (2-D) and 3-dimensional (3-D) in vitro assays. The inhibitory effect on invasion was maintained independently by the migration mode utilized by the cells in our 3-D model, and was accompanied by an impaired formation of actin-based cytoskeletal protrusive structures. Our data propose Eps8 as a key molecule involved in the control of the intrinsic invasive behavior of GBM cells, and suggest that this protein might represent a useful target for the design of new drugs for the treatment of these tumors.

Pretubulysin: from hypothetical biosynthetic intermediate to potential lead in tumor therapy

Pretubulysin is a natural product that is found in strains of myxobacteria in only minute amounts. It represents the first enzyme-free intermediate in the biosynthesis of tubulysins and undergoes post-assembly acylation and oxidation reactions. Pretubulysin inhibits the growth of cultured mammalian cells, as do tubulysins, which are already in advanced preclinical development as anticancer and antiangiogenic agents. The mechanism of action of this highly potent compound class involves the depolymerization of microtubules, thereby inducing mitotic arrest. Supply issues with naturally occurring derivatives can now be circumvented by the total synthesis of pretubulysin, which, in contrast to tubulysin, is synthetically accessible in gram-scale quantities. We show that the simplified precursor is nearly equally potent to the parent compound. Pretubulysin induces apoptosis and inhibits cancer cell migration and tubulin assembly in vitro. Consequently, pretubulysin appears to be an ideal candidate for future development in preclinical trials and is a very promising early lead structure in cancer therapy.

Role of integrins in regulating proteases to mediate extracellular matrix remodeling

The extracellular matrix (ECM) is an extracellular scaffold composed of complex mixtures of proteins that plays a pivotal role in tumor progression. ECM remodeling is crucial for tumor migration and invasion during the process of metastasis. ECM can be remodeled by several processes including synthesis, contraction and proteolytic degradation. In order to cross through the ECM barriers, malignant cells produce a spectrum of extracellular proteinases including matrix metalloproteinases (MMPs), serine proteases (mainly the urokinase plasminogen activator (uPA) system) and cysteine proteases to degrade ECM components. As major adhesion molecules to support cell attachment to ECM, integrins play critical roles in tumor progression by enhancing tumor cell survival, migration and invasion. Previous studies have shown that integrins can regulate the expression and activity of these proteases through different pathways. This review summarizes the roles of MMPs and uPA system in ECM remodeling and discusses the regulatory functions of integrins on these proteases in invasive tumors.

Quantitative shape analysis of chemoresistant colon cancer cells: correlation between morphotype and phenotype

Morphological, qualitative observations allow pathologists to correlate the shape the cells acquire with the progressive, underlying neoplastic transformation they are experienced. Cell morphology, indeed, roughly scales with malignancy. A quantitative parameter for characterizing complex irregular structures is the Normalized Bending Energy (NBE). NBE provides a global feature for shape characterization correspondent to the amount of energy needed to transform the specific shape under analysis into its lowest energy state. We hypothesized that a chemotherapy resistant cancer cell line would experience a significant change in its shape, and that such a modification might be quantified by means of NBE parameterization. We checked out the usefulness of a mathematical algorithm to distinguish wild and 5-fluorouracil (5-FU)-resistant colon cancer HCT-8 cells (HCT-8FUres). NBE values, as well as cellular and molecular parameters, were recorded in both cell populations. Results demonstrated that acquisition of drug resistance is accompanied by statistically significant morphological changes in cell membrane, as well as in biological parameters. Namely, NBE increased progressively meanwhile cells become more resistant to increasing 5-FU concentrations. These data indicate how tight the relationships between morphology and phenotype is, and they support the idea to follow a cell transition toward a drug-resistant phenotype by means of morphological monitoring.