Mobility and invasiveness of metastatic esophageal cancer are potentiated by shear stress in a ROCK- and Ras-dependent manner

Mechanism insights and therapeutic intervention of tumor metastasis: latest developments and perspectives

Metastasis remains a pivotal characteristic of cancer and is the primary contributor to cancer-associated mortality. Despite its significance, the mechanisms governing metastasis are not fully elucidated. Contemporary findings in the domain of cancer biology have shed light on the molecular aspects of this intricate process. Tumor cells undergoing invasion engage with other cellular entities and proteins en route to their destination. Insights into these engagements have enhanced our comprehension of the principles directing the movement and adaptability of metastatic cells. The tumor microenvironment plays a pivotal role in facilitating the invasion and proliferation of cancer cells by enabling tumor cells to navigate through stromal barriers. Such attributes are influenced by genetic and epigenetic changes occurring in the tumor cells and their surrounding milieu. A profound understanding of the metastatic process's biological mechanisms is indispensable for devising efficacious therapeutic strategies. This review delves into recent developments concerning metastasis-associated genes, important signaling pathways, tumor microenvironment, metabolic processes, peripheral immunity, and mechanical forces and cancer metastasis. In addition, we combine recent advances with a particular emphasis on the prospect of developing effective interventions including the most popular cancer immunotherapies and nanotechnology to combat metastasis. We have also identified the limitations of current research on tumor metastasis, encompassing drug resistance, restricted animal models, inadequate biomarkers and early detection methods, as well as heterogeneity among others. It is anticipated that this comprehensive review will significantly contribute to the advancement of cancer metastasis research.

Shear Stress Drives the Cleavage Activation of Protease-Activated Receptor 2 by PRSS3/Mesotrypsin to Promote Invasion and Metastasis of Circulating Lung Cancer Cells

When circulating tumor cells (CTCs) travel in circulation, they can be killed by detachment-induced anoikis and fluidic shear stress (SS)-mediated apoptosis. Circulatory treatment, which can make CTCs detached but also generate SS, can increase metastasis of cancer cells. To identify SS-specific mechanosensors without detachment impacts, a microfluidic circulatory system is used to generate arteriosus SS and compare transcriptome profiles of circulating lung cancer cells with suspended cells. Half of the cancer cells can survive SS damage and show higher invasion ability. Mesotrypsin (PRSS3), protease-activated receptor 2 (PAR2), and the subunit of activating protein 1, Fos-related antigen 1 (FOSL1), are upregulated by SS, and their high expression is responsible for promoting invasion and metastasis. SS triggers PRSS3 to cleave the N-terminal inhibitory domain of PAR2 within 2 h. As a G protein-coupled receptor, PAR2 further activates the Gαi protein to turn on the Src-ERK/p38/JNK-FRA1/cJUN axis to promote the expression of epithelial-mesenchymal transition markers, and also PRSS3, which facilitates metastasis. Enriched PRSS3, PAR2, and FOSL1 in human tumor samples and their correlations with worse outcomes reveal their clinical significance. PAR2 may serve as an SS-specific mechanosensor cleavable by PRSS3 in circulation, which provides new insights for targeting metastasis-initiating CTCs.

Cell response to mechanical microenvironment cues via Rho signaling: From mechanobiology to mechanomedicine

Mechanical cues in the cell microenvironment such as those from extracellular matrix properties, stretching, compression and shear stress, play a critical role in maintaining homeostasis. Upon sensing mechanical stimuli, cells can translate these external forces into intracellular biochemical signals to regulate their cellular behaviors, but the specific mechanisms of mechanotransduction at the molecular level remain elusive. As a subfamily of the Ras superfamily, Rho GTPases have been recognized as key intracellular mechanotransduction mediators that can regulate multiple cell activities such as proliferation, migration and differentiation as well as biological processes such as cytoskeletal dynamics, metabolism, and organ development. However, the upstream mechanosensors for Rho proteins and downstream effectors that respond to Rho signal activation have not been well illustrated. Moreover, Rho-mediated mechanical signals in previous studies are highly context-dependent. In this review, we systematically summarize the types of mechanical cues in the cell microenvironment and provide recent advances on the roles of the Rho-based mechanotransduction in various cell activities, physiological processes and diseases. Comprehensive insights into the mechanical roles of Rho GTPase partners would open a new paradigm of mechanomedicine for a variety of diseases. STATEMENT OF SIGNIFICANCE: In this review, we highlight the critical role of Rho GTPases as signal mediators to respond to physical cues in microenvironment. This article will add a distinct contribution to this set of knowledge by intensively addressing the relationship between Rho signaling and mechanobiology/mechanotransduction/mechanomedcine. This topic has not been discussed by the journal, nor has it yet been developed by the field. The comprehensive picture that will develop, from molecular mechanisms and engineering methods to disease treatment strategies, represents an important and distinct contribution to the field. We hope that this review would help researchers in various fields, especially clinicians, oncologists and bioengineers, who study Rho signal pathway and mechanobiology/mechanotransduction, understand the critical role of Rho GTPase in mechanotransduction.

Fluid Flow Stimulation Modulates Expression of S100 Genes in Normal Breast Epithelium and Breast Cancer

INTRODUCTION

S100 proteins are intracellular calcium ion sensors that participate in cellular processes, some of which are involved in normal breast functioning and breast cancer development. Despite several S100 genes being overexpressed in breast cancer, their roles during disease development remain elusive. Human mammary epithelial cells (HMECs) can be exposed to fluid shear stresses and implications of such interactions have not been previously studied. The goal of this study was to analyze expression profiles of S100 genes upon exposing HMECs to fluid flow.

METHODS

HMECs and breast cancer cell lines were exposed to fluid flow in a parallel-plate bioreactor system. Changes in gene expression were quantified using microarrays and qPCR, gene-gene interactions were elucidated using network analysis, and key modified genes were examined in three independent clinical datasets.

RESULTS

S100 genes were among the most upregulated genes upon flow stimulation. Network analysis revealed interactions between upregulated transcripts, including interactions between S100P, S100PBP, S100A4, S100A7, S100A8 and S100A9. Overexpression of S100s was also observed in patients with early stage breast cancer compared to normal breast tissue, and in most breast cancer patients. Finally, survival analysis revealed reduced survival times for patients with elevated expression of S100A7 and S100P.

CONCLUSION

This study shows that exposing HMECs to fluid flow upregulates genes identified clinically to be overexpressed during breast cancer development, including S100A7 and S100P. These findings are the first to show that S100 genes are flow-responsive and might be participating in a fundamental adaptation pathway in normal tissue that is also active in breast cancer.

Fluid flow exposure promotes epithelial-to-mesenchymal transition and adhesion of breast cancer cells to endothelial cells

BACKGROUND

Mechanical interactions between tumor cells and microenvironments are frequent phenomena during breast cancer progression, however, it is not well understood how these interactions affect Epithelial-to-Mesenchymal Transition (EMT). EMT is associated with the progression of most carcinomas through induction of new transcriptional programs within affected epithelial cells, resulting in cells becoming more motile and adhesive to endothelial cells.

METHODS

MDA-MB-231, SK-BR-3, BT-474, and MCF-7 cells and normal Human Mammary Epithelial Cells (HMECs) were exposed to fluid flow in a parallel-plate bioreactor system. Changes in expression were quantified using microarrays, qPCR, immunocytochemistry, and western blots. Gene-gene interactions were elucidated using network analysis, and key modified genes were examined in clinical datasets. Potential involvement of Smads was investigated using siRNA knockdown studies. Finally, the ability of flow-stimulated and unstimulated cancer cells to adhere to an endothelial monolayer, migrate and invade membrane pores was evaluated in flow and static adhesion experiments.

RESULTS

Fluid flow stimulation resulted in upregulation of EMT inducers and downregulation of repressors. Specifically, Vimentin and Snail were upregulated both at the gene and protein expression levels in flow stimulated HMECs and MDA-MB-231 cells, suggesting progression towards an EMT phenotype. Flow-stimulated SNAI2 was abrogated with Smad3 siRNA. Flow-induced overexpression of a panel of cell adhesion genes was also observed. Network analysis revealed genes involved in cell flow responses including FN1, PLAU, and ALCAM. When evaluated in clinical datasets, overexpression of FN1, PLAU, and ALCAM was observed in patients with different subtypes of breast cancer. We also observed increased adhesion, migration and invasion of flow-stimulated breast cancer cells compared to unstimulated controls.

CONCLUSIONS

This study shows that fluid forces on the order of 1 Pa promote EMT and adhesion of breast cancer cells to an endothelial monolayer and identified biomarkers were distinctly expressed in patient populations. A better understanding of how biophysical forces such as shear stress affect cellular processes involved in metastatic progression of breast cancer is important for identifying new molecular markers for disease progression, and for predicting metastatic risk.

Slow transcription of the 99a/let-7c/125b-2 cluster results in differential miRNA expression and promotes melanoma phenotypic plasticity

Almost half of human miRNAs are encoded in clusters. Although transcribed as a single unit, the levels of individual mature miRNAs often differ. The mechanisms underlying differential biogenesis of clustered miRNAs and the resulting physiological implications are mostly unknown. Here, we report that the melanoma master transcription regulator MITF regulates the differential expression of the 99a/let-7c/125b-2 cluster by altering the distribution of RNA polymerase II (Pol-II) along the cluster. We discovered that MITF interacts with TRIM28, a known inhibitor of Pol-II transcription elongation, at the let-7c region resulting in Pol-II pausing and causing its elevated expression, whereas low levels of Pol-II occupation over miR-99a and miR-125b-2 regions decreases their biogenesis. Furthermore, we showed that this differential expression affects the phenotypic state of melanoma cells. RNA-seq analysis of proliferative melanoma cells that express miR-99a and miR-125b mimics revealed a transcriptomic shift toward an invasive phenotype. Conversely, expression of a let-7c mimic in invasive melanoma cells induced a shift to a more proliferative state. We confirmed direct target genes of these miRNAs: FGFR3, BAP1, Bcl2, TGFBR1, and CDKN1A. Our study demonstrates a MITF-governed biogenesis mechanism that results in differential expression of clustered 99a/let-7c/125b-2 miRNAs that control melanoma progression.

Targeting the cytoskeleton against metastatic dissemination

Cancer is a pathology characterized by a loss or a perturbation of a number of typical features of normal cell behaviour. Indeed, the acquisition of an inappropriate migratory and invasive phenotype has been reported to be one of the hallmarks of cancer. The cytoskeleton is a complex dynamic network of highly ordered interlinking filaments playing a key role in the control of fundamental cellular processes, like cell shape maintenance, motility, division and intracellular transport. Moreover, deregulation of this complex machinery contributes to cancer progression and malignancy, enabling cells to acquire an invasive and metastatic phenotype. Metastasis accounts for 90% of death from patients affected by solid tumours, while an efficient prevention and suppression of metastatic disease still remains elusive. This results in the lack of effective therapeutic options currently available for patients with advanced disease. In this context, the cytoskeleton with its regulatory and structural proteins emerges as a novel and highly effective target to be exploited for a substantial therapeutic effort toward the development of specific anti-metastatic drugs. Here we provide an overview of the role of cytoskeleton components and interacting proteins in cancer metastasis with a special focus on small molecule compounds interfering with the actin cytoskeleton organization and function. The emerging involvement of microtubules and intermediate filaments in cancer metastasis is also reviewed.

Activation of cell migration via morphological changes in focal adhesions depends on shear stress in MYCN-amplified neuroblastoma cells

Neuroblastoma is the most common solid tumour of childhood, and it metastasizes to distant organs. However, the mechanism of metastasis, which generally depends on the cell motility of the neuroblastoma, remains unclear. In many solid tumours, it has been reported that shear stress promotes metastasis. Here, we investigated the relationship between shear stress and cell motility in the MYCN-amplified human neuroblastoma cell line IMR32, using a microfluidic device. We confirmed that most of the cells migrated downstream, and cell motility increased dramatically when the cells were exposed to a shear stress of 0.4 Pa, equivalent to that expected in vivo. We observed that the morphological features of focal adhesion were changed under a shear stress of 0.4 Pa. We also investigated the relationship between malignancy and the motility of IMR32 cells under shear stress. Decreasing the expression of MYCN in IMR32 cells via siRNA transfection inhibited cell motility by a shear stress of 0.4 Pa. These results suggest that MYCN-amplified neuroblastoma cells under high shear stress migrate to distant organs due to high cell motility, allowing cell migration to lymphatic vessels and venules.

Silence of lncRNA ANRIL represses cell growth and promotes apoptosis in retinoblastoma cells through regulating miR-99a and c-Myc

Retinoblastoma is a rare cancer of the immature retina. This study designed to see the function of the lncRNA ANRIL in retinoblastoma Y79 cells. ANRIL, miR-99a and c-Myc expression in Y79 cells was altered by transfection and then trypan blue, transwell assay and flow cytometry were carried out to evaluate the changes of cell phenotype. The connection between ANRIL, miR-99a and c-Myc was measured by luciferase reporter assay and RNA immunoprecipitation analysis. As a result, ANRIL expression was highly expressed in human retinoblastoma tissue as relative to the adjacent noncancerous tissues. ANRIL suppression inhibited Y79 cells viability, migration, invasion, while promoted apoptosis. ANRIL negatively regulated miR-99a by binding to miR-99a. Silence of miR-99a reversed the ANRIL-knockdown effects on Y79 cells. miR-99a overexpression suppressed Y79 cell viability, migration, invasion, and enhanced apoptosis through downregulating c-Myc. Meanwhile, we found that miR-99a inhibited JAK/STAT and PI3K/AKT pathways. To conclude, it seems that ANRIL suppression inhibits cell growth and metastasis in retinoblastoma Y79 cells by regulating miR-99a and c-Myc.

Migrastatics-Anti-metastatic and Anti-invasion Drugs: Promises and Challenges

In solid cancers, invasion and metastasis account for more than 90% of mortality. However, in the current armory of anticancer therapies, a specific category of anti-invasion and antimetastatic drugs is missing. Here, we coin the term ‘migrastatics’ for drugs interfering with all modes of cancer cell invasion and metastasis, to distinguish this class from conventional cytostatic drugs, which are mainly directed against cell proliferation. We define actin polymerization and contractility as target mechanisms for migrastatics, and review candidate migrastatic drugs. Critical assessment of these antimetastatic agents is warranted, because they may define new options for the treatment of solid cancers.

Local invasion and metastasis, rather than clonal proliferation, are the dominant features of solid cancer. However, a specific category of anti-invasion and antimetastatic drugs is missing for treatment of solid cancer

We propose the term ‘migrastatics’ for drugs interfering with all modes of cancer cell invasiveness and, consequently, with their ability to metastasize (e.g., inhibiting not only local invasion, but also extravasation and metastatic colonization).

In solid cancer, drug resistance is the main cause of treatment failure, and is attributed to mutations of the target. Since targeting the cause, although academically desirable, may be futile, a pragmatic and near-term option is to move downstream, to common denominators of cell migration and/or invasion, such as actin polymerization and actomyosin-mediated contractility.

Circular-shaped microfluidic device to study the effect of shear stress on cellular orientation

Understanding the effects of shear stress on mammalian cells is a crucial factor for understanding a number of biological processes and diseases. Here, we show the development of a circular-shaped microfluidic device for the facile generation of shear stress gradients. With this microfluidic device, the effect of shear stress on orientation of human umbilical vein endothelial cells was studied. This microfluidic device, which enables to control the alignment of human umbilical vein endothelial cells within a microchannel, can be a valuable tool to mimic blood vessels.

Biomechanics of the Circulating Tumor Cell Microenvironment

Circulating tumor cells (CTCs) exist in a microenvironment quite different from the solid tumor tissue microenvironment. They are detached from matrix and exposed to the immune system and hemodynamic forces leading to the conclusion that life as a CTC is "nasty, brutish, and short." While there is much evidence to support this assertion, the mechanisms underlying this are much less clear. In this chapter we will specifically focus on biomechanical influences on CTCs in the circulation and examine in detail the question of whether CTCs are mechanically fragile, a commonly held idea that is lacking in direct evidence. We will review multiple lines of evidence indicating, perhaps counterintuitively, that viable cancer cells are mechanically robust in the face of exposures to physiologic shear stresses that would be encountered by CTCs during their passage through the circulation. Finally, we present emerging evidence that malignant epithelial cells, as opposed to their benign counterparts, possess specific mechanisms that enable them to endure these mechanical stresses.

Morphomechanical and structural changes induced by ROCK inhibitor in breast cancer cells

The EMT phenomenon is based on tumour progression. The cells lose their physiologic phenotype and assumed a mesenchymal phenotype characterized by an increased migratory capacity, invasiveness and high resistance to apoptosis. In this process, RHO family regulates the activation or suppression of ROCK (Rho-associated coiled-coil containing protein kinase) which in turn regulates the cytoskeleton dynamics. However, while the biochemical mechanisms are widely investigated, a comprehensive and careful estimation of biomechanical changes has not been extensively addressed. In this work, we used a strong ROCK inhibitor, Y-27632, to evaluate the effects of inhibition on living breast cancer epithelial cells by a biomechanical approach. Atomic Force Microscopy (AFM) was used to estimate changes of cellular elasticity, quantified by Young's modulus parameter. The morphometric alterations were analyzed by AFM topographies and Confocal Laser Scanning Microscopy (CLSM). Our study revealed a significant modification in the Young's modulus after treatment, especially as regards cytoskeletal region. Our evidences suggest that the use of Y-27632 enhanced the cell rigidity, preventing cell migration and arrested the metastasization process representing a potential powerful factor for cancer treatment.

Rho, ROCK and actomyosin contractility in metastasis as drug targets

Metastasis is the spread of cancer cells around the body and the cause of the majority of cancer deaths. Metastasis is a very complex process in which cancer cells need to dramatically modify their cytoskeleton and cope with different environments to successfully colonize a secondary organ. In this review, we discuss recent findings pointing at Rho-ROCK or actomyosin force (or both) as major drivers of many of the steps required for metastatic success. We propose that these are important drug targets that need to be considered in the clinic to palliate metastatic disease.

Transient Receptor Potential Canonical 7 (TRPC7), a Calcium (Ca(2+)) Permeable Non-selective Cation Channel

Transient receptor potential canonical subfamily, member 7 (TRPC7) is the most recently identified member of the TRPC family of Ca(2+)-permeable non-selective cation channels. The gene encoding the TRPC7 channel plasma membrane protein was first cloned from mouse brain. TRPC7 mRNA and protein have been detected in cell types derived from multiple organ systems from various species including humans. Gq-coupled protein receptor activation is the predominant mode of TRPC7 activation. Lipid metabolites involved in the phospholipase C (PLC) signaling pathway, including diacylglycerol (DAG) and its precursor the phosphatidylinositol-4,5-bisphosphate (PIP2), have been shown to be direct regulators of TRPC7 channel. TRPC7 channels have been linked to the regulation of various cellular functions however, the depth of our understanding of TRPC7 channel function and regulation is limited in comparison to other TRP channel family members. This review takes a historical look at our current knowledge of TRPC7 mechanisms of activation and its role in cellular physiology and pathophysiology.

Fabrication of keratin/fibroin membranes by electrospinning for vascular tissue engineering

Cardiovascular diseases (CVDs) are some of the leading causes of death and bypass surgery is one of the common treatment options for the critical CVD patients.

Living in shear: platelets protect cancer cells from shear induced damage

Pharmacologically and genetically induced thrombocytopenia is associated with decreased metastasis, highlighting the importance of platelets in the bloodborne dissemination of cancer cells. It is frequently suggested that platelets support metastasis, in part, by protecting cancer cells from shear stress, a biomechanical force generated by blood flow. However, there is currently no evidence to support this hypothesis. To address this, we investigated the effect of shear stress on A2780 ovarian cancer cells in the presence and absence of platelets. Using a cone and plate viscometer, suspensions of A2780 cells with and without platelets were exposed to shear rates representing venous (200 s(-1)) and arterial (1,500 s(-1)) blood flow. Lactate dehydrogenase (LDH) release was used to quantify shear induced membrane damage. Both venous and arterial shear rates induced the release of LDH from A2780 cells, demonstrating their susceptibility to shear forces. In contrast, platelets released minimal levels of LDH in response to similar conditions. In the presence of platelets, there was a significant decrease in LDH release by A2780 cells under shear conditions, suggesting that platelets can confer protection against shear induced damage. The disruption of platelet-cancer cell interactions could increase the shear stress induced destruction of cancer cells in vivo.

Do fasudil and Y-27632 affect the level of transient receptor potential (TRP) gene expressions in breast cancer cell lines?

Breast cancer (BC) is the most frequent cancer type in women, and the mortality rate is high especially in metastatic disease. Ion channels such as the transient receptor potential (TRP) channels correlate with malignant growth and cancer progression. Hence, some authors have suggested that the expression levels of TRP channels may be used as a marker in the diagnosis and predicting the prognosis of BC. Also, in some recent studies, targeting TRP channels are suggested as a novel treatment strategy in BC. The aim of this study was to investigate the effect of two Rho-kinase (ROCK) inhibitors, fasudil and Y-27632, on the expression levels of TRP channel genes in breast cancer cell lines (ZR-75-1, MCF7, and MDA-MB-231) and breast epithelial cell line (hTERT-HME1). The expression levels of TRP genes were determined by quantitative reverse transcription polymerase chain reaction (qRT-PCR). We found that fasudil had reduced the TRPC1, TRPV2 expression levels in the ZR-75-1, MCF7, and MDA-MB-231 cell lines. On the other hand, fasudil and Y-27632 had reduced TRPM6 expression levels in all cell lines. Y-27632 increased the expression levels of TRPC7 in all cell lines. In conclusion, this is the first study demonstrating that the inhibition of ROCK pathway changes the expression levels of some TRP genes. Also, our study has firstly shown that the expression levels of the TRP genes which are suggested as a diagnostic and prognostic biomarker in BC, were changed with the treatment of fasudil and Y-27632.

The effect of ROCK-1 activity change on the adhesive and invasive ability of Y79 retinoblastoma cells

BACKGROUND

Retinoblastoma (Rb) is the most common intraocular tumor in childhood worldwide. It is a deadly pediatric eye cancer. The main cause of death in Rb patients is intracranial and systemic metastasis. ROCK is the main downstream effector of Ras-homologous (Rho) family of GTPases which are involved in many cellular functions, such as cell proliferation, invasion and metastasis. Overexpression of ROCK promotes invasion and metastasis of many solid tumors. However, the effect of ROCK in Rb is largely unknown.

METHODS

ROCK-1 and ROCK-2 mRNA expression in Y79 cell lines were examined by RT-PCR. Protein expression in the Y79 cell line were examined by western blot analyses. ROCK-1 and ROCK-2 siRNA were transfected into Y79 cells with Lipofectamine 2000. Cell proliferation was evaluated by CCK-8 assay after exposure to ROCK inhibitor (Y-27632). We examined the effect of ROCK inhibitors (Y-27632, ROCK-1 and ROCK-2 siRNA) on Y79 cell adhesive capacity by cell adhesion assay. Cell invasion assay through matrigel was used to study the effect of ROCK inhibitors on Y79 cell invasive capacity.

RESULTS

The expression of mRNA of ROCK-1 was more than that of ROCK-2 in the Y79 cell line. The protein expression levels of ROCK-1 and ROCK-2 were downregulated in the cells transfected with siRNA. Y-27632 treatment didn't lead to any changes of Y79 cells proliferation. Adhesive ability of Y79 cells was enhanced following Y-27632 or ROCK-1 siRNA treatment. The invasive capacity of Y79 cells showed an inverse relationship with increasing Y-27632 concentration. Invasiveness of Y79 cells also decreased in Y79 cells transfected with ROCK-1 siRNA. However, there was no change in adhesive ability or invasive capacity in Y79 cells transfected with siRNA against ROCK-2.

CONCLUSIONS

The findings of this study demonstrate that ROCK-1 protein plays a key role in regulating metastasis and invasion of Y79 cells, suggesting that the ROCK-1 dependent pathway may be a potential target for therapy of Rb.

Inhibition of Rho-associated coiled-coil-forming kinase increases efficacy of measles virotherapy

RhoA and its downstream effector Rho-associated coiled-coil-forming kinase (ROCK) are known regulators of the formation of actin cytoskeleton in cells. Actin cytoskeleton is involved in paramyxovirus infection; we, therefore, examined the effect of ROCK inhibition on measles virus (MV) cytopathic effect and replication. Treatment with the ROCK inhibitor, Y27632, significantly increased syncytia size in tumor cell lines following MV infection, associated with cytoskeleton disruption as demonstrated by actin staining. Treatment of prostate cancer, breast cancer and glioblastoma tumor cell lines with Y27632 following MV infection resulted in increased cytopathic effect, as assessed by trypan blue exclusion assays. In addition, there was a significant increase in viral proliferation by at least one log or more as tested in one-step viral growth curves. Increased viral replication was also observed in athymic nude mice bearing MDA-MB-231 xenografts following combination treatment with MV and Y27632. In summary, inhibition of the ROCK kinase by Y27632 enhanced the oncolytic effect of MV and viral proliferation; this approach merits further translational investigation.

Three-dimensional microfluidic collagen hydrogels for investigating flow-mediated tumor-endothelial signaling and vascular organization

Hyperpermeable tumor vessels are responsible for elevated interstitial fluid pressure and altered flow patterns within the tumor microenvironment. These aberrant hydrodynamic stresses may enhance tumor development by stimulating the angiogenic activity of endothelial cells lining the tumor vasculature. However, it is currently not known to what extent shear forces affect endothelial organization or paracrine signaling during tumor angiogenesis. The objective of this study was to develop a three-dimensional (3D), in vitro microfluidic tumor vascular model for coculture of tumor and endothelial cells under varying flow shear stress conditions. A central microchannel embedded within a collagen hydrogel functions as a single neovessel through which tumor-relevant hydrodynamic stresses are introduced and quantified using microparticle image velocimetry (μ-PIV). This is the first use of μ-PIV in a tumor representative, 3D collagen matrix comprised of cylindrical microchannels, rather than planar geometries, to experimentally measure flow velocity and shear stress. Results demonstrate that endothelial cells develop a confluent endothelium on the microchannel lumen that maintains integrity under physiological flow shear stresses. Furthermore, this system provides downstream molecular analysis capability, as demonstrated by quantitative RT-PCR, in which, tumor cells significantly increase expression of proangiogenic genes in response to coculture with endothelial cells under low flow conditions. This work demonstrates that the microfluidic in vitro cell culture model can withstand a range of physiological flow rates and permit quantitative measurement of wall shear stress at the fluid-collagen interface using μ-PIV optical flow diagnostics, ultimately serving as a versatile platform for elucidating the role of fluid forces on tumor-endothelial cross talk.

Investigation of the esophageal Rho-kinase expression in patients with Barrett's esophagus

The mechanisms responsible for the malignant transformation in Barrett's esophagus (BE) are still poorly understood. The authors have evaluated the role of Rho-kinase (ROCK1 and ROCK2) expressions in patients with BE. All patients underwent upper gastrointestinal system endoscopy, which was confirmed histologically. Real-time PCR revealed no marked change in gene expressions of ROCK1 and ROCK2 at mRNA levels in BE when compared to controls. Immunohistochemical and western blot analyses showed no change in ROCK1 and ROCK2 protein expressions in BE. This study demonstrates that Rho-kinase gene and protein expressions are not modified in BE.

Using space-based investigations to inform cancer research on Earth

Experiments conducted in the microgravity environment of space are not typically at the forefront of the mind of a cancer biologist. However, space provides physical conditions that are not achievable on Earth, as well as conditions that can be exploited to study mechanisms and pathways that control cell growth and function. Over the past four decades, studies have shown how exposure to microgravity alters biological processes that may be relevant to cancer. In this Review, we explore the influence of microgravity on cell biology, focusing on tumour cells grown in space together with work carried out using models in ground-based investigations.

Fluid-flow induced wall shear stress and epithelial ovarian cancer peritoneal spreading

Epithelial ovarian cancer (EOC) is usually discovered after extensive metastasis have developed in the peritoneal cavity. The ovarian surface is exposed to peritoneal fluid pressures and shear forces due to the continuous peristaltic motions of the gastro-intestinal system, creating a mechanical micro-environment for the cells. An in vitro experimental model was developed to expose EOC cells to steady fluid flow induced wall shear stresses (WSS). The EOC cells were cultured from OVCAR-3 cell line on denuded amniotic membranes in special wells. Wall shear stresses of 0.5, 1.0 and 1.5 dyne/cm² were applied on the surface of the cells under conditions that mimic the physiological environment, followed by fluorescent stains of actin and β-tubulin fibers. The cytoskeleton response to WSS included cell elongation, stress fibers formation and generation of microtubules. More cytoskeletal components were produced by the cells and arranged in a denser and more organized structure within the cytoplasm. This suggests that WSS may have a significant role in the mechanical regulation of EOC peritoneal spreading.

Statin reverses smoke-induced pulmonary hypertension and prevents emphysema but not airway remodeling

RATIONALE

the potential role of statins in treating chronic obstructive pulmonary disease (COPD) is controversial, and it is unclear what anatomic COPD lesions statins affect.

OBJECTIVES

to determine whether an intervention of simvastatin could alter cigarette smoke-induced pulmonary hypertension.

METHODS

we exposed guinea pigs to cigarette smoke for 6 months. In half the animals, simvastatin therapy was initiated after 3 months of smoke exposure. Pulmonary arterial systolic pressures were monitored weekly with a radiotelemetric catheter; additional physiologic and morphologic measurements were made at sacrifice after 6 months. Precision-cut lung explants were assessed for evidence of endothelial dysfunction, and in situ vascular nitric oxide generation was measured with 4,5-diaminofluorescein diacetate.

MEASUREMENTS AND MAIN RESULTS

cigarette smoke increased the pulmonary arterial systolic pressure after approximately 4 weeks. Simvastatin returned the pressure to control levels within 4 weeks of starting treatment, and ameliorated smoke-induced small arterial remodeling as well as emphysema measured both physiologically and morphometrically at 6 months, but did not prevent smoke-induced small airway remodeling either physiologically or morphologically. In precision-cut lung slices simvastatin reversed small arterial endothelial dysfunction, and partially reversed smoke-induced loss of vascular nitric oxide generation.

CONCLUSIONS

simvastatin, as an intervention therapy, reverses the pulmonary vascular effects of cigarette smoke, including pulmonary hypertension, and prevents smoke-induced emphysema, but does not prevent small airway remodeling. This is the first demonstration that an intervention can reverse a COPD-associated cigarette smoke-induced anatomic abnormality. The study also shows the importance of examining all three anatomic lung compartments when assessing the effects of a potential drug intervention in patients with COPD.

The extracellular matrix microtopography drives critical changes in cellular motility and Rho A activity in colon cancer cells

We have shown that the microtopography (mT) underlying colon cancer changes as a tumor de-differentiates. We distinguish the well-differentiated mT based on the increasing number of "pits" and poorly differentiated mT on the basis of increasing number of "posts." We investigated Rho A as a mechanosensing protein using mT features derived from those observed in the ECM of colon cancer. We evaluated Rho A activity in less-tumorogenic (Caco-2 E) and more tumorigenic (SW620) colon cancer cell-lines on microfabricated pits and posts at 2.5 μm diameter and 200 nm depth/height. In Caco-2 E cells, we observed a decrease in Rho A activity as well as in the ratio of G/F actin on surfaces with either pits or posts but despite this low activity, knockdown of Rho A led to a significant decrease in confined motility suggesting that while Rho A activity is reduced on these surfaces it still plays an important role in controlling cellular response to barriers. In SW620 cells, we observed that Rho A activity was greatest in cells plated on a post microtopography which led to increased cell motility, and an increase in actin cytoskeletal turnover.

Analogues of Y27632 increase gap junction communication and suppress the formation of transformed NIH3T3 colonies

BACKGROUND

Constitutive activation of RhoA-dependent RhoA kinase (ROCK) signalling is known to promote cellular transformation and the ROCK inhibitor Y-27632 has the ability to suppress focus formation of RhoA transformed NIH3T3 cells.

METHODS

Sixty-four novel structural analogues of Y27632 were synthesised and tested for their ability to persistently inhibit the transformation of NIH3T3 cells by Rho guanidine exchange factor 16 (ARHGEF16) or Ras. In vitro kinase inhibitor profiling, co-culture of transformed cells with non-transformed cells and a novel Lucifer yellow/PKH67 dye transfer method were used to investigate their mode of action.

RESULTS

Four Y27632 analogues inhibited transformed focus formation that persisted when the compound was withdrawn. No toxicity was observed against either transformed or non-transformed cells and the effect was dependent on co-culture of these two cell types. In vitro kinase inhibitor profiling indicated that these compounds had reduced activity against ROCK compared with Y27632, targeting instead Aurora A (AURKA), p38 (MAPK14) and Hgk (MAP4K4). Dye transfer analysis showed they increased gap junction intercellular communication (GJIC) between transformed and non-transformed cells.

CONCLUSIONS

These data are the first to suggest that transient blockade of specific kinases can induce a persistent inhibition of non-contact inhibited transformed colony formation and can also remove pre-formed colonies. These effects could potentially be mediated by the observed increase in GJIC between transformed and non-transformed cells. Selection of kinase inhibitors with this property may thus provide a novel strategy for cancer chemoprevention.

Effects of ROCK inhibitor, Y-27632, on adhesion and mobility in esophageal squamous cell cancer cells

Rho-associated protein kinase (ROCK), a molecular switch, modulates cellular functions in many cancers, such as hepatocellular, breast, colon cancers, etc. However, little is known the effect of ROCK on cell adhesion and mobility in esophageal squamous cell cancer (ESCC), one of the most diagnosed cancers in China. In this study, Y-27632 was used to specifically block ROCK activity in ESCC cells. Adhesion of ESCC cells was detected by homotypic and heterotypic adhesion assay together with examination of E-cadherin expression. Motility of ESCC cells changes were examined by detection of phosphorylated cofilin and observed under confocal microscopy, respectively. We found that Y-27632 increased both heterotypic and homotypic adhesion, and the expression of E-cadherin; decreased phosphorylated cofilin resulting in actin rearrangement in ESCC cells. All these findings indicate that ROCK signaling pathway plays an important role in cell adhesion and mobility, suggesting that it may be used as a potential target for therapy of ESCC.

Shear stress induces internalization of E-cadherin and invasiveness in metastatic oesophageal cancer cells by a Src-dependent pathway

Metastatic disease is dependent on tumor cell migration through the venous and lymphatic systems and requires dynamic rearrangement of adherens junctions. Endocytosis of cadherins is a key mechanism to dynamically arrange adherens junctions, signaling, and motility in tumor cells; however, the role of shear in regulating this process in metastatic cells is unknown. In this study, the role of shear in regulating cell surface expression of E-cadherin was investigated. We found that exposure to venous shear (shear rate, 200/s) induced internalization of E-cadherin in adherent metastatic oesophageal tumor cells (OC-1 tumor cell line). Internalized E-cadherin was found localized to Rab5-positive endosomes and was not present in lysosomes. As the Src family of tyrosine kinase have been implicated in regulating cadherin expression, we investigated the role of shear in regulating E-cadherin through Src activity. Pretreatment of OC-1 cells with the specific Src kinase inhibitor 4-amino-5- (4-methylphenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP1) prevented shear-induced internalization of E-cadherin. Direct measurement of Src activity (phosphorylation on Y416) showed that Src is activated in sheared OC-1 cells and that the shear-induced increase in phospho-Src is inhibited by the presence of PP1. Moreover, we show that shear stress significantly increased the invasive capacity of OC-1 cells (P < 0.001), a process inhibited by the presence of PP1. These results indicate a novel role for shear in regulating the endocytosis of E-cadherin and invasiveness in metastatic cells.

The noncanonical WNT pathway is operative in idiopathic pulmonary arterial hypertension

Idiopathic pulmonary arterial hypertension (IPAH) is a fatal disease that comprises sustained vasoconstriction, enhanced proliferation of pulmonary vascular cells, and in situ thrombosis. The discovery of several contributing signaling pathways in recent years has resulted in an expanding array of novel therapies; however, IPAH remains a progressive disease with poor outcome in most instances. To identify new regulatory pathways of vascular remodeling in IPAH, we performed transcriptome-wide expression profiling of laser-microdissected pulmonary arterial resistance vessels derived from explanted IPAH and nontransplanted donor lung tissues. Statistical analysis of the data derived from six individuals in each group showed significant regulation of several mediators of the canonical and noncanonical WNT pathway. As to the noncanonical WNT pathway, the planar cell polarity (PCP) pathway, the ras homolog gene family member A (RHOA), and ras-related C3 botulinum toxin substrate-1 (RAC1) were strongly up-regulated. Real-time PCR of laser-microdissected pulmonary arteries confirmed these array results and showed in addition significant up-regulation of further PCP mediators wingless member 11 (WNT11), disheveled associated activator of morphogenesis-1 (DAAM1), disheveled (DSV), and RHO-kinase (ROCK). Immunohistochemical staining and semiquantitative expression analysis confirmed the markedly enhanced expression of the PCP mediators in the pulmonary resistance vessels, in particular in the endothelial layer in IPAH. Therefore we propose the PCP pathway to be critically involved in the regulation of vascular remodeling in IPAH.

Inhibition of ROCK activity allows InlF-mediated invasion and increased virulence of Listeria monocytogenes

Listeria monocytogenes is an intracellular bacterial pathogen that causes life-threatening disease. The mechanisms used by L. monocytogenes to invade non-professional phagocytic cells are not fully understood. In addition to the requirement of bacterial determinants, host cell conditions profoundly influence infection. Here, we have shown that inhibition of the RhoA/ROCK pathway by pharmacological inhibitors or RNA interference results in increased L. monocytogenes invasion of murine fibroblasts and hepatocytes. InlF, a member of the internalin multigene family with no known function, was identified as a L. monocytogenes-specific factor mediating increased host cell binding and entry. Conversely, activation of RhoA/ROCK activity resulted in decreased L. monocytogenes adhesion and invasion. Furthermore, virulence of wild-type bacteria during infection of mice was significantly increased upon inhibition of ROCK activity, whereas colonization and virulence of an inlF deletion mutant was not affected, thus supporting a role for InlF as a functional virulence determinant in vivo under specific conditions. In addition, inhibition of ROCK activity in human-derived cells enhanced either bacterial adhesion or adhesion and entry in an InlF-independent manner, further suggesting a host species or cell type-specific role for InlF and that additional bacterial determinants are involved in mediating ROCK-regulated invasion of human cells.

Importance of hemodynamic forces as signals for exercise-induced changes in endothelial cell phenotype

Current evidence indicates that the ability of physical activity to sustain a normal phenotype of arterial endothelial cells (ECs) plays a central role in the beneficial effects of exercise (Ex) on atherosclerotic disease. Here we evaluate the strength of evidence that shear stress (SS) and/or circumferential wall stress (stretch) are the primary signals, produced by bouts of Ex, that signal altered gene expression in arterial ECs, thereby resulting in a less atherogenic EC phenotype. Current literature indicates that SS is a signal for expression of antiatherogenic genes in cultured ECs, in ECs of isolated arteries, and in ECs of arteries in intact animals. Furthermore, SS levels in the arteries of humans during Ex are in the range that produces beneficial changes. In contrast, complex flow profiles within recirculation zones and/or oscillatory flow patterns can cause proatherogenic gene expression in ECs. In vivo evidence indicates that Ex decreases oscillatory flow/SS in some portions of the arterial tree but may increase oscillatory flow in other areas of the arterial tree. Circumferential wall stress can increase expression of some beneficial EC genes as well, but circumferential wall stress also increases production of reactive oxygen species and increases the expression of adhesion factors and other proatherogenic genes. Interactions of arterial pressure and fluid SS play an important role in arterial vascular health and likely contribute to how Ex bouts signal changes in EC gene expression. It is also clear that other local and circulating factors interact with these hemodynamic signals during Ex to produce the healthy arterial EC phenotype. We conclude that available evidence suggests that exercise signals formation of beneficial endothelial cell phenotype at least in part through changes in SS and wall stretch in the arteries.

Clinical and prognostic significance of RhoA and RhoC gene expression in esophageal squamous cell carcinoma

BACKGROUND

Rho GTPases are involved in the organization of a microfilament network, cell-to-cell interaction, and malignant transformation. To elucidate the role of Rho GTPases in esophageal squamous cell carcinoma (ESCC), we compared the levels of RhoA and RhoC mRNA from ESCC with the corresponding normal tissue originating from the same patients.

METHODS

Real-time reverse transcriptase-polymerase chain reaction was performed to observe rhoA and rhoC in esophageal cell lines. Next, the mRNA levels of rhoA and rhoC were evaluated from 50 patients.

RESULTS

The rhoA and rhoC were higher in ESCC cell lines than in noncancerous esophageal cell. rhoC was overexpressed in TTn, which was obtained directly from a surgical specimen of a metastatic lesion of ESCC in the mandible. rhoA and rhoC were significantly higher in ESCC patient than in the normal counterparts (P = .0022 and P < .0001, respectively). rhoA correlated with tumor differentiation and rhoC correlated with an advanced tumor, node, metastasis system classifications. rhoA and rhoC in ESCC showed a positive correlation (P = .008). Patients with rhoA overexpression showed a significantly poorer prognosis than those with rhoA underexpression (P = .044).

CONCLUSIONS

To our knowledge, this study is the first in which the expression of RhoA and RhoC at the mRNA level in ESCC was examined and compared with its normal counterpart. Our results suggest that rhoA and rhoC are involved in ESCC progression and useful as prognostic markers. Further study will be needed to examine the therapeutic potential of the Rho GTPase inhibitor as a promising anticancer therapy, especially in ESCC.

CCG-1423: a small-molecule inhibitor of RhoA transcriptional signaling

Lysophosphatidic acid receptors stimulate a Galpha(12/13)/RhoA-dependent gene transcription program involving the serum response factor (SRF) and its coactivator and oncogene, megakaryoblastic leukemia 1 (MKL1). Inhibitors of this pathway could serve as useful biological probes and potential cancer therapeutic agents. Through a transcription-based high-throughput serum response element-luciferase screening assay, we identified two small-molecule inhibitors of this pathway. Mechanistic studies on the more potent CCG-1423 show that it acts downstream of Rho because it blocks SRE.L-driven transcription stimulated by Galpha(12)Q231L, Galpha(13)Q226L, RhoA-G14V, and RhoC-G14V. The ability of CCG-1423 to block transcription activated by MKL1, but not that induced by SRF-VP16 or GAL4-VP16, suggests a mechanism targeting MKL/SRF-dependent transcriptional activation that does not involve alterations in DNA binding. Consistent with its role as a Rho/SRF pathway inhibitor, CCG-1423 displays activity in several in vitro cancer cell functional assays. CCG-1423 potently (<1 mumol/L) inhibits lysophosphatidic acid-induced DNA synthesis in PC-3 prostate cancer cells, and whereas it inhibits the growth of RhoC-overexpressing melanoma lines (A375M2 and SK-Mel-147) at nanomolar concentrations, it is less active on related lines (A375 and SK-Mel-28) that express lower levels of Rho. Similarly, CCG-1423 selectively stimulates apoptosis of the metastasis-prone, RhoC-overexpressing melanoma cell line (A375M2) compared with the parental cell line (A375). CCG-1423 inhibited Rho-dependent invasion by PC-3 prostate cancer cells, whereas it did not affect the Galpha(i)-dependent invasion by the SKOV-3 ovarian cancer cell line. Thus, based on its profile, CCG-1423 is a promising lead compound for the development of novel pharmacologic tools to disrupt transcriptional responses of the Rho pathway in cancer.

Fluvastatin inhibits hypoxic proliferation and p38 MAPK activity in pulmonary artery fibroblasts

The earliest structural change in hypoxia-induced pulmonary hypertension is increased proliferation of adventitial fibroblasts. This fibroproliferative response occurs in acute and chronic hypoxic models, is dependent on p38 mitogen-activated protein (MAP) kinase activation, is selective for the pulmonary circulation, and would seem an important therapeutic target. Simvastatin attenuates pulmonary vascular remodeling in animal models, but additional information regarding mechanisms of action, differential antiproliferative effects and dose responses of available statins is required for appropriate clinical trial design. Our objectives were to determine the effects of statins on acute hypoxia-induced proliferation and p38 MAP kinase activation in pulmonary and systemic artery fibroblasts, to assess the effects of cholesterol intermediates, prenyltransferase and related inhibitors, and to determine the statin's mechanism of action. Atorvastatin, fluvastatin, and simvastatin inhibited adventitial fibroblast proliferation. At low doses (1 microM), this effect was selective for hypoxic (versus serum-induced) proliferation and was also selective for pulmonary (versus systemic) fibroblasts. Complete inhibition of hypoxia-induced p38 MAP kinase activity was achieved at this 1-microM dose. The lipophilic statins exhibited similar potency. The statin effect was reversed by geranylgeranyl pyrophosphate and mimicked by geranylgeranyl transferase and Rac1 inhibitors. Hypoxia-induced p38 MAP kinase activation and proliferation in pulmonary adventitial fibroblasts is dependent on a geranylgeranylated signaling protein, probably Rac1. One micromolar of fluvastatin exhibits a circulation- and stimulus-selective antiproliferative effect on pulmonary artery fibroblasts. The pharmacokinetics of fluvastatin would suggest that its antiproliferative effects may be useful in pulmonary hypertension associated with hypoxia.

Organized migration of epithelial cells requires control of adhesion and protrusion through Rho kinase effectors

Migration of epithelial cell sheets, a process involving F-actin restructuring through Rho family GTPases, is both physiologically and pathophysiologically important. Our objective was to clarify the mechanisms whereby the downstream RhoA effector Rho-associated coil-coil-forming kinase (ROCK) influences coordinated epithelial cell motility. Although cells exposed to a pharmacological ROCK inhibitor (Y-27632) exhibited increased spreading in wound closure assays, they failed to migrate in a cohesive manner. Two main phenomena were implicated: the formation of aberrant protrusions at the migrating front and the basal accumulation of F-actin aggregates. Aggregates reflected increased membrane affiliation and detergent insolubility of the actin-binding protein ezrin and enhanced coassociation of ezrin with the membrane protein CD44. While F-actin aggregation following ROCK inhibition was recapitulated by inhibiting myosin light chain (MLC) phosphorylation with the MLC kinase inhibitor ML-7, the latter did not influence protrusiveness and, in fact, significantly decreased cell migration. Our results suggest that excessive protrusiveness downstream of ROCK inhibition reflects an influence of ROCK on F-actin stability via LIM kinase 1 (LIMK-1), which phosphorylates and inactivates cofilin. Y-27632 reduced the levels of both active LIMK-1 and inactive cofilin (phospho forms), and expression of a dominant negative LIMK-1 mutant stimulated leading edge protrusiveness. Furthermore, Y-27632-induced protrusions were partially reversed by overexpression of LIMK-1 to restore cofilin phosphorylation. In summary, our results provide new evidence suggesting that adhesive and protrusive events involved in organized epithelial motility downstream of ROCK are separately coordinated through the phosphorylation of (respectively) MLC and cofilin.

Allometric scaling of wall shear stress from mice to humans: quantification using cine phase-contrast MRI and computational fluid dynamics

Allometric scaling laws relate structure or function between species of vastly different sizes. They have rarely been derived for hemodynamic parameters known to affect the cardiovascular system, e.g., wall shear stress (WSS). This work describes noninvasive methods to quantify and determine a scaling law for WSS. Geometry and blood flow velocities in the infrarenal aorta of mice and rats under isoflurane anesthesia were quantified using two-dimensional magnetic resonance angiography and phase-contrast magnetic resonance imaging at 4.7 tesla. Three-dimensional models constructed from anatomic data were discretized and used for computational fluid dynamic simulations using phase-contrast velocity imaging data as inlet boundary conditions. WSS was calculated along the infrarenal aorta and compared between species to formulate an allometric equation for WSS. Mean WSS along the infrarenal aorta was significantly greater in mice and rats compared with humans (87.6, 70.5, and 4.8 dyn/cm2, P < 0.01), and a scaling exponent of −0.38 ( R2 = 0.92) was determined. Manipulation of the murine genome has made small animal models standard surrogates for better understanding the healthy and diseased human cardiovascular system. It has therefore become increasingly important to understand how results scale from mouse to human. This noninvasive methodology provides the opportunity to serially quantify changes in WSS during disease progression and/or therapeutic intervention.