WF-536 inhibits metastatic invasion by enhancing the host cell barrier and inhibiting tumour cell motility

The Journey of Cancer Cells to the Brain: Challenges and Opportunities

Cancer metastases into the brain constitute one of the most severe, but not uncommon, manifestations of cancer progression. Several factors control how cancer cells interact with the brain to establish metastasis. These factors include mediators of signaling pathways participating in migration, infiltration of the blood-brain barrier, interaction with host cells (e.g., neurons, astrocytes), and the immune system. Development of novel therapies offers a glimpse of hope for increasing the diminutive life expectancy currently forecasted for patients suffering from brain metastasis. However, applying these treatment strategies has not been sufficiently effective. Therefore, there is a need for a better understanding of the metastasis process to uncover novel therapeutic targets. In this review, we follow the journey of various cancer cells from their primary location through the diverse processes that they undergo to colonize the brain. These processes include EMT, intravasation, extravasation, and infiltration of the blood-brain barrier, ending up with colonization and angiogenesis. In each phase, we focus on the pathways engaging molecules that potentially could be drug target candidates.

Dasabuvir suppresses esophageal squamous cell carcinoma growth in vitro and in vivo through targeting ROCK1

Esophageal squamous cell carcinoma (ESCC) is an upper gastrointestinal cancer with high morbidity and mortality. New strategies are urgently needed to prolong patients' survival. Through screening FDA-approved drugs, we found dasabuvir, a drug approved for hepatitis C virus (HCV) treatment, suppressed ESCC proliferation. Dasabuvir could inhibit the growth of ESCC cells in a time and dose-dependent manner and arrested cell cycle at the G0/G1 phase. The antitumor activity was further validated in vivo using patient-derived xenograft tumor models. In terms of mechanism, we unveil that dasabuvir is a Rho-associated protein kinase 1 (ROCK1) inhibitor. Dasabuvir can bind to ROCK1 and suppress its kinase activity, thus downregulating the phosphorylation of ERK1/2 by ROCK1 and the expression of cyclin-dependent kinase 4 (CDK4) and cyclin D1. These results provide evidence that dasabuvir suppresses ESCC growth in vivo and in vitro through blocking ROCK1/ERK signaling pathway.

The Design, Synthesis and Evaluation of Rho-kinase Inhibitory Activity of 4-aryl-thiazole-2-amines

Rho-associated kinases (ROCK) are a class of serine/threonine kinases that play important roles in various biological processes. ROCK are becoming attractive targets for drug designing. A novel scaffold was designed according to molecular hybridization strategy, then a series of 4-aryl-5-aminomethyl-thiazole-2-amines were synthesized, and their inhibitory activities on ROCK were screened by enzyme-linked immunosorbent assay (ELISA). The results showed that 4-aryl-5-aminomethyl-thiazole-2-amines derivatives displayed certain ROCK II inhibitory activities. The IC₅₀ value of the most potent compound 4v was found to be 20 nM. The preliminary structure-activity-relationship investigation showed that compounds with 4-pyridine substitution were generally found to be more potent than compounds with 3-pyridine substitution. The molecular docking studies indicated that more optimization work needs to conduct to obtain more potent ROCK inhibitors.

Cardiac Safety of Kinase Inhibitors - Improving Understanding and Prediction of Liabilities in Drug Discovery Using Human Stem Cell-Derived Models

Many small molecule kinase inhibitors (SMKIs) used to fight cancer have been associated with cardiotoxicity in the clinic. Therefore, preventing their failure in clinical development is a priority for preclinical discovery. Our study focused on the integration and concurrent measurement of ATP, apoptosis dynamics and functional cardiac indexes in human stem cell-derived cardiomyocytes (hSC-CMs) to provide further insights into molecular determinants of compromised cardiac function. Ten out of the fourteen tested SMKIs resulted in a biologically relevant decrease in either beating rate or base impedance (cell number index), illustrating cardiotoxicity as one of the major safety liabilities of SMKIs, in particular of those involved in the PI3K–AKT pathway. Pearson's correlation analysis indicated a good correlation between the different read-outs of functional importance. Therefore, measurement of ATP concentrations and apoptosis in vitro could provide important insight into mechanisms of cardiotoxicity. Detailed investigation of the cellular signals facilitated multi-parameter evaluation allowing integrative assessment of cardiomyocyte behavior. The resulting correlation can be used as a tool to highlight changes in cardiac function and potentially to categorize drugs based on their mechanisms of action.

Design, synthesis and biological evaluation of 4-aryl-5-aminoalkyl-thiazole-2-amines derivatives as ROCK II inhibitors

A series of 4-aryl-5-aminoalkyl-thiazole-2-amines were designed and synthesized, and their inhibitory activity on ROCK II was screened by enzyme-linked immunosorbent assay (ELISA). The results showed that 4-aryl-5-aminomethyl-thiazole-2-amines derivatives had certain ROCK II inhibitory activities. Compound 10l showed ROCK II inhibitory activity with IC₅₀ value of 20 nM.

Potently inhibiting cancer cell migration with novel 3H-pyrazolo[4,3-f]quinoline boronic acid ROCK inhibitors

Rho-associated protein kinases (ROCKs) are ubiquitously expressed in most adult tissues, and are involved in modulating the cytoskeleton, protein synthesis and degradation pathways, synaptic function, and autophagy to list a few. A few ROCK inhibitors, such as fasudil and netarsudil, are approved for clinical use. Here we present a new ROCK inhibitor, boronic acid containing HSD1590, which is more potent than netarsudil at binding to or inhibiting ROCK enzymatic activities. This compound exhibits single digit nanomolar binding to ROCK (Kds < 2 nM) and subnanomolar enzymatic inhibition profile (ROCK2 IC50 is 0.5 nM for HSD1590. Netarsudil, an FDA-approved drug, inhibited ROCK2 with IC50 = 11 nM under similar conditions). Whereas netarsudil was cytotoxic to breast cancer cell line, MDA-MB-231 (greater than 80% growth inhibition at concentrations greater than 5 μM), HSD1590 displayed low cytotoxicity to MDA-MB-231. Interestingly, at 1 μM HSD1590 inhibited the migration of MDA-MB-231 whereas netarsudil did not.

Prognostic value and functional role of ROCK2 in pediatric Ewing sarcoma

Ewing's sarcoma (EWS) is a highly aggressive bone cancer that affects children and adolescents. Despite advances in multimodal management, 5-year event-free survival rates for patients presenting with metastases at diagnosis remain at 25%. As key regulators of actin organization, the Rho-associated coiled-coil containing protein kinases, ROCK1 and ROCK2, have been associated with cancer dissemination and poorer prognosis. Recently, in vitro data indicating ROCK2 as a molecular target for the treatment of EWS has been presented. Nonetheless, a deeper exploration of the contribution of this kinase dysregulation in EWS is still necessary. In this regard, the present study aimed to evaluate the expression of ROCK1 and ROCK2 in 23 pediatric tumor samples and to verify the prospect of using their pharmacological inhibition through functional assays. Our results showed positive immunostaining for ROCK1 and ROCK2 in the majority samples (75 and 65%, respectively). A significantly increased risk of incomplete remission in patients with positive immunostaining for ROCK2 was found (P=0.026), though no correlations with other prognostic features (huvos classification, FLI1/EWS status, relapse, metastasis or death) were observed. Associations with survival were merely suggestive. Apparent protein expression of both kinases was also found in EWS cell lines (SK-ES-1 and RD-ES). Treatments with selective ROCK inhibitors did not alter cell viability or migration in vitro. However, a significant increase in invasion was observed after treatment with SR3677 (ROCK2 inhibitor) and hydroxyfasudil (pan-inhibitor). Consequently, even though the majority of EWS samples included in our study showed positivity for ROCK1 and ROCK2, the lack of significant associations with prognosis and absence of appropriate responses to their inhibition in vitro does not support their prospective use as therapeutic targets for the treatment of this metastatic tumor. Larger cohort studies might provide more evidence on whether there is a specific role of ROCK kinases in EWS physiopathology.

O-GlcNAcylation promotes migration and invasion in human ovarian cancer cells via the RhoA/ROCK/MLC pathway

O-GlcNAcylation is a dynamic and reversible post-translational modification associated with the regulation of multiple cellular functions. The addition and removal of O-Linked β-N-acetylglucosamine (O-GlcNAc) on target proteins is catalyzed by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), respectively. Accumulating evidence suggests that O-GlcNAcylation is associated with the malignancy of several types of human cancer. To investigate the effect of O-GlcNAcylation on ovarian cancer phenotypes, global O-GlcNAc levels were decreased by OGT silencing through RNA interference and increased by inhibiting OGA activity with Thiamet-G. Transwell assay results demonstrated that OGT silencing inhibited the migration and invasion of SKOV3 and 59M ovarian cells in vitro, while Thiamet-G treatment promoted migration and invasion. Furthermore, a pull-down assay and western blot analysis demonstrated that Thiamet-G treatment enhanced RhoA activity and the phosphorylation of the Rho-associated protein kinase (ROCK) substrate, myosin light chain (MLC), while OGT silencing attenuated RhoA activity and MLC phosphorylation. In addition, RhoA silencing via RNA interference and inhibition of ROCK activity with Y-27632 prevented Thiamet-G-induced increases in cell migration and invasion. These data suggest that O-GlcNAcylation augments the motility of ovarian cancer cells via the RhoA/ROCK/MLC signaling pathway. Therefore, O-GlcNAcylation may be a potential target for the diagnosis and treatment of ovarian cancer.

α-TEA inhibits the growth and motility of human colon cancer cells via targeting RhoA/ROCK signaling

Colon or colorectal cancer is a common type of human cancer, which originates in the intestine crassum or the rectum. In the United States, colorectal cancer has one of the highest rates of cancer-related mortality. Investigating novel chemotherapeutic approaches is significant in the treatment of cancers, such as colorectal cancer. α-tocopherol ether-linked acetic acid (α-TEA) is a potent anticancer agent in multiple types of human cancer. However, its effect remains to be determined in colon cancer. In this study, HCT116 and SW480 human colon cancer cells were used to investigate the anticancer role of α-TEA. It was demonstrated that α-TEA inhibited cell proliferation, migration and invasion in colon cancer cells. Furthermore, it was shown that α-TEA downregulated the activity of RhoA and phosphorylated Rho-associated protein kinase (ROCK) substrate myosin light chain (MLC) using a pull-down assay and western blotting, respectively, implying that the RhoA/ROCK pathway is involved in α-TEA-mediated cell growth and motility inhibition. In order to confirm this hypothesis a RhoA inhibitor (clostridium botulinum C3 exoenzyme), a ROCK inhibitor (Y27632) and RhoA small interfering (si)RNA were applied to block RhoA/ROCK signaling. This resulted in the attenuation of MLC phosphorylation, and augmentation of α-TEA-mediated growth and motility inhibition in colon cancer cells. In conclusion, these results indicate that α-TEA inhibits growth and motility in colon cancer cells possibly by targeting RhoA/ROCK signaling. Moreover, combined with RhoA or ROCK inhibitors, α-TEA may exhibit a more effective inhibitory role in colon cancer.

Investigation of Rho-Kinase Expressions and Polymorphisms in Mantle Cell Lymphoma Patients

OBJECTIVE

Mantle cell lymphoma (MCL) is a rare but aggressive form of B-cell non-Hodgkin lymphoma characterized by excessive expression of cyclin D1. Intracellular signaling enzyme Rho-kinase (ROCK) can contribute to cellular migration, proliferation, and differentiation, as well as tumor development and metastasis. However, ROCK gene and protein expressions or polymorphisms have never been investigated in MCL patients. The purpose of this study was to investigate the role of ROCK gene and protein expressions in MCL patients. We also examined ROCK2 gene polymorphisms in this study.

MATERIALS AND METHODS

A total of 60 patients with MCL and 60 healthy controls were included in this retrospective study. Hematoxylin and eosin-stained lymph node tissue slides in the entire archive were reevaluated and used for immunohistochemistry, gene expression, and polymerase chain reaction studies.

RESULTS

In immunohistochemical studies, there were significant increases in ROCK1 (p=0.0009) and ROCK2 (p<0.0001) protein expressions in MCL patients when compared with the control group. Although a marked increase in ROCK1 gene expression (p=0.0215) was noted, no significant change was observed in ROCK2 gene expression in MCL patients. Seven ROCK2 polymorphisms were studied, but the results showed no significant differences between the groups.

CONCLUSION

This is the first study to show that ROCK1 gene and ROCK protein expressions may contribute to the development of MCL.

Rho Kinase (ROCK) Inhibitors and Their Therapeutic Potential

Rho kinases (ROCKs) belong to the serine-threonine family, the inhibition of which affects the function of many downstream substrates. As such, ROCK inhibitors have potential therapeutic applicability in a wide variety of pathological conditions including asthma, cancer, erectile dysfunction, glaucoma, insulin resistance, kidney failure, neuronal degeneration, and osteoporosis. To date, two ROCK inhibitors have been approved for clinical use in Japan (fasudil and ripasudil) and one in China (fasudil). In 1995 fasudil was approved for the treatment of cerebral vasospasm, and more recently, ripasudil was approved for the treatment of glaucoma in 2014. In this Perspective, we present a comprehensive review of the physiological and biological functions for ROCK, the properties and development of over 170 ROCK inhibitors as well as their therapeutic potential, the current status, and future considerations.

Rho-associated kinase signalling and the cancer microenvironment: novel biological implications and therapeutic opportunities

The Rho/ROCK pathway is involved in numerous pivotal cellular processes that have made it an area of intense study in cancer medicine, however, Rho-associated coiled-coil containing protein kinase (ROCK) inhibitors are yet to make an appearance in the clinical cancer setting. Their performance as an anti-cancer therapy has been varied in pre-clinical studies, however, they have been shown to be effective vasodilators in the treatment of hypertension and post-ischaemic stroke vasospasm. This review addresses the various roles the Rho/ROCK pathway plays in angiogenesis, tumour vascular tone and reciprocal feedback from the tumour microenvironment and explores the potential utility of ROCK inhibitors as effective vascular normalising agents. ROCK inhibitors may potentially enhance the delivery and efficacy of chemotherapy agents and improve the effectiveness of radiotherapy. As such, repurposing of these agents as adjuncts to standard treatments may significantly improve outcomes for patients with cancer. A deeper understanding of the controlled and dynamic regulation of the key components of the Rho pathway may lead to effective use of the Rho/ROCK inhibitors in the clinical management of cancer.

Afzelin exhibits anti-cancer activity against androgen-sensitive LNCaP and androgen-independent PC-3 prostate cancer cells through the inhibition of LIM domain kinase 1

Prostate cancer presents high occurrence worldwide. Medicinal plants are a major source of novel and potentially therapeutic molecules; therefore, the aim of the present study was to investigate the possible anti-prostate cancer activity of afzelin, a flavonol glycoside that was previously isolated from Nymphaea odorata. The effect of afzelin on the proliferation of androgen-sensitive LNCaP and androgen-independent PC-3 cells was evaluated by performing a water soluble tetrazolium salt-1 assay. In addition, the effect of afzelin on the cell cycle of the LNCaP and PC-3 prostate cancer cell lines was evaluated. Western blot analysis was performed to evaluate the effect of afzelin on the kinases responsible for the regulation of actin organization. Afzelin was identified to inhibit the proliferation of LNCaP and PC3 cells, and block the cell cycle in the G₀ phase. The anticancer activity of afzelin in these cells was determined to be due to inhibition of LIM domain kinase 1 expression. Thus, the in vitro efficacy of afzelin against prostate cancer is promising; however, additional studies on different animal models are required to substantiate its anticancer potential.

Targeting Rho-GTPases in immune cell migration and inflammation

Leukocytes are unmatched migrators capable of traversing barriers and tissues of remarkably varied structural composition. An effective immune response relies on the ability of its constituent cells to infiltrate target sites. Yet, unwarranted mobilization of immune cells can lead to inflammatory diseases and tissue damage ranging in severity from mild to life-threatening. The efficacy and plasticity of leukocyte migration is driven by the precise spatiotemporal regulation of the actin cytoskeleton. The small GTPases of the Rho family (Rho-GTPases), and their immediate downstream effector kinases, are key regulators of cellular actomyosin dynamics and are therefore considered prime pharmacological targets for stemming leukocyte motility in inflammatory disorders. This review describes advances in the development of small-molecule inhibitors aimed at modulating the Rho-GTPase-centric regulatory pathways governing motility, many of which stem from studies of cancer invasiveness. These inhibitors promise the advent of novel treatment options with high selectivity and potency against immune-mediated pathologies.

Rho kinase inhibitors: a patent review (2012 - 2013)

INTRODUCTION

The Rho kinase/ROCK is critical in vital signal transduction pathways central to many essential cellular activities. Since ROCK possess multiple substrates, modulation of ROCK activity is useful for treatment of many diseases.

AREAS COVERED

Significant progress has been made in the development of ROCK inhibitors over the past two years (Jan 2012 to Aug 2013). Patent search in this review was based on FPO IP Research and Communities and Espacenet Patent Search. In this review, patent applications will be classified into four groups for discussions. The grouping is mainly based on structures or scaffolds (groups 1 and 2) and biological functions of ROCK inhibitors (groups 3 and 4). These four groups are i) ROCK inhibitors based on classical structural elements for ROCK inhibition; ii) ROCK inhibitors based on new scaffolds; iii) bis-functional ROCK inhibitors; and iv) novel applications of ROCK inhibitors.

EXPERT OPINION

Although currently only one ROCK inhibitor (fasudil) is used as a drug, more drugs based on ROCK inhibition are expected to be advanced into market in the near future. Several directions should be considered for future development of ROCK inhibitors, such as soft ROCK inhibitors, bis-functional ROCK inhibitors, ROCK2 isoform-selective inhibitors, and ROCK inhibitors as antiproliferation agents.

Chromosome 2p gain in monoclonal B-cell lymphocytosis and in early stage chronic lymphocytic leukemia

Recent studies have described chromosome 2p gain as a recurrent lesion in chronic lymphocytic leukemia (CLL). We investigated the 2p gain and its relationship with common prognostic biomarkers in a prospective series of 69 clinical monoclonal B-cell lymphocytosis (cMBL) and 218 early stage (Binet A) CLL patients. The 2p gain was detected by FISH in 17 patients (6%, 16 CLL, and 1 cMBL) and further characterized by single nucleotide polymorphism-array. Overall, unfavorable cytogenetic deletions, i.e., del(11)(q23) and del(17)(p13) (P = 0.002), were significantly more frequent in 2p gain cases, as well as unmutated status of IGHV (P < 1 × 10(-4) ) and CD38 (P < 1 × 10(-4) ) and ZAP-70 positive expression (P = 0.003). Furthermore, 2p gain patients had significantly higher utilization of stereotyped B-cell receptors compared with 2p negative patients (P = 0.009), and the incidence of stereotyped subset #1 in 2p gain patients was significantly higher than that found in the remaining CLLs (P = 0.031). Transcriptional profiling analysis identified several genes significantly upregulated in 2p gain CLLs, most of which mapped to 2p. Among these, NCOA1 and ROCK2 are known for their involvement in tumor progression in several human cancers, whereas among those located in different chromosomes, CAV1 at 7q31.1 has been recently identified to play a critical role in CLL progression. Thus, 2p gain can be present since the early stages of the disease, particularly in those cases characterized by other poor prognosis markers. The finding of genes upregulated in the cells with 2p gain provides new insights to define the pathogenic role of this lesion.

ROCK1 and ROCK2 are required for non-small cell lung cancer anchorage-independent growth and invasion

Evidence is emerging that the closely related ROCK1 and ROCK2 serine/threonine kinases support the invasive and metastatic growth of a spectrum of human cancer types. Therefore, inhibitors of ROCK are under preclinical development. However, a key step in their development involves the identification of genetic biomarkers that will predict ROCK inhibitor antitumor activity. One identified mechanism for ROCK activation in cancer involves the loss of function of the DLC1 tumor suppressor gene, which encodes a GTPase activating protein (RhoGAP) for the RhoA and RhoC small GTPases. DLC-1 loss may lead to hyperactivation of RhoA/C and its downstream effectors, the ROCK kinases. We therefore determined whether loss of DLC-1 protein expression identifies non-small cell lung carcinoma (NSCLC) cell lines whose growth and invasion phenotypes are sensitive to ROCK inhibition. We identified and characterized a novel small molecule pharmacologic inhibitor of ROCK and additionally applied genetic approaches to impair ROCK1 and/or ROCK2 activity, and we determined that although NSCLC anchorage-dependent growth was ROCK-independent, both anchorage-independent growth and Matrigel invasion were ROCK-dependent. However, loss of DLC-1 expression did not correlate with ROCK activation or with OXA-06 sensitivity. Unexpectedly, suppression of ROCK1 or ROCK2 expression alone was sufficient to impair anchorage-independent growth, supporting their nonoverlapping roles in oncogenesis. Mechanistically, the block in anchorage-independent growth was associated with accumulation of cells in the G(0)-G(1) phase of the cell cycle, but not increased anoikis. We conclude that ROCK may be a useful therapeutic target for NSCLC.

ROCK1 and ROCK2 are required for non-small cell lung cancer anchorage-independent growth and invasion

Evidence is emerging that the closely related ROCK1 and ROCK2 serine/threonine kinases support the invasive and metastatic growth of a spectrum of human cancer types. Therefore, inhibitors of ROCK are under preclinical development. However, a key step in their development involves the identification of genetic biomarkers that will predict ROCK inhibitor antitumor activity. One identified mechanism for ROCK activation in cancer involves the loss of function of the DLC1 tumor suppressor gene, which encodes a GTPase activating protein (RhoGAP) for the RhoA and RhoC small GTPases. DLC-1 loss may lead to hyperactivation of RhoA/C and its downstream effectors, the ROCK kinases. We therefore determined whether loss of DLC-1 protein expression identifies non-small cell lung carcinoma (NSCLC) cell lines whose growth and invasion phenotypes are sensitive to ROCK inhibition. We identified and characterized a novel small molecule pharmacologic inhibitor of ROCK and additionally applied genetic approaches to impair ROCK1 and/or ROCK2 activity, and we determined that although NSCLC anchorage-dependent growth was ROCK-independent, both anchorage-independent growth and Matrigel invasion were ROCK-dependent. However, loss of DLC-1 expression did not correlate with ROCK activation or with OXA-06 sensitivity. Unexpectedly, suppression of ROCK1 or ROCK2 expression alone was sufficient to impair anchorage-independent growth, supporting their nonoverlapping roles in oncogenesis. Mechanistically, the block in anchorage-independent growth was associated with accumulation of cells in the G(0)-G(1) phase of the cell cycle, but not increased anoikis. We conclude that ROCK may be a useful therapeutic target for NSCLC.

Differential protein expression profiles in estrogen receptor-positive and -negative breast cancer tissues using label-free quantitative proteomics

Identification of the proteins that are associated with estrogen receptor (ER) status is a first step towards better understanding of the hormone-dependent nature of breast carcinogenesis. Although a number of gene expression analyses have been conducted, protein complement has not been systematically investigated to date. Because proteins are primary targets of therapeutic drugs, in this study, we have attempted to identify proteomic signatures that demarcate ER-positive and -negative breast cancers. Using highly enriched breast tumor cells, replicate analyses from 3 ERα+ and 3 ERα- human breast tumors resulted in the identification of 2,995 unique proteins with ≥2 peptides. Among these, a number of receptor tyrosine kinases and intracellular kinases that are abundantly expressed in ERα+ and ERα- breast cancer tissues were identified. Further, label-free quantitative proteome analysis revealed that 236 proteins were differentially expressed in ERα+ and ERα- breast tumors. Among these, 141 proteins were selectively up-regulated in ERα+, and 95 proteins were selectively up-regulated in ERα- breast tumors. Comparison of differentially expressed proteins with a breast cancer database revealed 98 among these have been previously reported to be involved in breast cancer. By Gene Ontology molecular function, dehydrogenase, reductase, cytoskeletal proteins, extracellular matrix, hydrolase, and lyase categories were significantly enriched in ERα+, whereas selected calcium-binding protein, membrane traffic protein, and cytoskeletal protein were enriched in ERα- breast tumors. Biological process and pathway analysis revealed that up-regulated proteins of ERα+ were overrepresented by proteins involved in amino acid metabolism, proteasome, and fatty acid metabolism, while up-regulated proteins of ERα- were overrepresented by proteins involved in glycolysis pathway. The presence and relative abundance of 4 selected differentially abundant proteins (liprin-α1, fascin, DAP5, and β-arrestin-1) were quantified and validated by immunohistochemistry. In conclusion, unlike in vitro cell culture models, the in vivo signaling proteins and pathways that we have identified directly from human breast cancer tissues may serve as relevant therapeutic targets for the pharmacological intervention of breast cancer.

Co-crystal structures of inhibitors with MRCKβ, a key regulator of tumor cell invasion

MRCKα and MRCKβ (myotonic dystrophy kinase-related Cdc42-binding kinases) belong to a subfamily of Rho GTPase activated serine/threonine kinases within the AGC-family that regulate the actomyosin cytoskeleton. Reflecting their roles in myosin light chain (MLC) phosphorylation, MRCKα and MRCKβ influence cell shape and motility. We report further evidence for MRCKα and MRCKβ contributions to the invasion of cancer cells in 3-dimensional matrix invasion assays. In particular, our results indicate that the combined inhibition of MRCKα and MRCKβ together with inhibition of ROCK kinases results in significantly greater effects on reducing cancer cell invasion than blocking either MRCK or ROCK kinases alone. To probe the kinase ligand pocket, we screened 159 kinase inhibitors in an in vitro MRCKβ kinase assay and found 11 compounds that inhibited enzyme activity >80% at 3 µM. Further analysis of three hits, Y-27632, Fasudil and TPCA-1, revealed low micromolar IC(50) values for MRCKα and MRCKβ. We also describe the crystal structure of MRCKβ in complex with inhibitors Fasudil and TPCA-1 bound to the active site of the kinase. These high-resolution structures reveal a highly conserved AGC kinase fold in a typical dimeric arrangement. The kinase domain is in an active conformation with a fully-ordered and correctly positioned αC helix and catalytic residues in a conformation competent for catalysis. Together, these results provide further validation for MRCK involvement in regulation of cancer cell invasion and present a valuable starting point for future structure-based drug discovery efforts.

A novel role of Rho-kinase in the regulation of ligand-induced phosphorylated EGFR endocytosis via the early/late endocytic pathway in human fibrosarcoma cells

The small GTPase RhoA and its downstream effectors, the Rho-associated kinase (Rho-kinase) family, are known to regulate cell morphology, motility, and tumor progression via the regulation of actin cytoskeleton rearrangement. In the present study, we evaluated the role of Rho-kinase in the intracellular endocytic trafficking of ligand-induced phosphorylated epidermal growth factor receptor (pEGFR). We investigated the time course of the internalization fate of EGF-induced pEGFR via the early/late endocytic pathway in human fibrosarcoma cell line HT1080 cells using Y-27632, a selective Rho-kinase inhibitor. We found, using confocal immunofluorescence microscopy and Western blot analysis, a large accumulation of pEGFR in the nuclei of HT1080 cells. In contrast, we observed decreased amounts of the pEGFR-positive staining in the nuclei along with an accumulation of cytosolic pEGFR staining when the cells were incubated for 15-30 min in the presence of Y-27632, implying that an aberrant endocytic trafficking mechanism of pEGFR occurs in HT1080 cells whereby pEGFR might be selectively translocated into the nucleus. Moreover, we demonstrated that after 15-min of stimulation with Texas Red-EGF, increasing numbers of pEGFR-positive staining that had colocalized with Texas Red-EGF-positive punctate staining were seen in the cytoplasm of HT1080 cells but after 30-min of stimulation, most of this staining had disappeared from the cytoplasm and a large accumulation of pEGFR-positive staining appeared in the nucleus. Thus, nuclear accumulation of pEGFR appears to occur in an EGF-dependent manner. In contrast, such nuclear pEGFR-positive staining was not seen in the Y-27632-treated cells. Furthermore, silencing of RhoA or Rho-kinases I/II by sequence specific siRNAs considerably inhibited the EGF-dependent nuclear accumulation of pEGFR. Collectively, these results provide the first evidence that Rho-kinase signaling pathway plays a suppressive role in the intracellular vesicle trafficking of pEGFR via the endocytic pathway and that an increased Rho-kinase activity leads to the attenuation of the normal endocytic vesicular traffic of pEGFR via the early/late endocytic pathway, instead causing pEGFR to be trafficked out of the endocytic vesicles into the nucleus.

Rho kinase and hypertension

Arterial hypertension is a multifactorial disease that is characterised by increased peripheral vascular resistance often accompanied by smooth muscle cell hypertrophy and proliferation. Rho kinases (ROCKs) are the most extensively studied effectors of the small G-protein RhoA and abnormalities in RhoA/ROCK signalling have been observed in various cardiovascular disease including hypertension. The RhoA/ROCK-pathway is a key player in different smooth muscle cell functions including contractility, proliferation and migration. Furthermore, there is extensive crosstalk between RhoA/ROCK- and NO-signalling. Therefore, not only ROCK inhibitors but also NO-donators or pleiotropic agents like statins exert their beneficial effects on the cardiovascular system at least in part via Rho/Rho-kinase.

Up-regulation of Rho/ROCK signaling in sarcoma cells drives invasion and increased generation of protrusive forces

Tumor cell invasion is the most critical step of metastasis. Determination of the mode of invasion within the particular tumor is critical for effective cancer treatment. Protease-independent amoeboid mode of invasion has been described in carcinoma cells and more recently in sarcoma cells on treatment with protease inhibitors. To analyze invasive behavior, we compared highly metastatic sarcoma cells with parental nonmetastatic cells. The metastatic cells exhibited a functional up-regulation of Rho/ROCK signaling and, similarly to carcinoma cells, an amoeboid mode of invasion. Using confocal and traction force microscopy, we showed that an up-regulation of Rho/ROCK signaling leads to increased cytoskeletal dynamics, myosin light chain localization, and increased tractions at the leading edge of the cells and that all of these contributed to increased cell invasiveness in a three-dimensional collagen matrix. We conclude that cells of mesenchymal origin can use the amoeboid nonmesenchymal mode of invasion as their primary invading mechanism and show the dependence of ROCK-mediated amoeboid mode of invasion on the increased capacity of cells to generate force.

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.

Development of Rho-kinase inhibitors for cardiovascular medicine

Rho-kinase (ROCK) is one of the downstream effectors of the small G-protein Rho. The Rho-ROCK pathway has an important role in mediating various cellular functions, including contraction, actin cytoskeleton organization, cell adhesion and motility, proliferation, cytokinesis and gene expression, all of which are involved in the pathogenesis of cardiovascular disease. Indeed, vascular smooth muscle cells, endothelial cells, adventitial cells, cardiomyocytes and nerve cells all undergo pathophysiological changes through the ROCK pathway. Abnormal activation of this pathway is associated with the pathogenesis of various cardiovascular diseases such as hypertension, coronary and cerebral vasospasm, restenosis, atherosclerosis, stroke and heart failure, although the roles of the ROCK isoforms (ROCK1 and ROCK2) remain to be elucidated. In this article, we review the information about the therapeutic importance of the ROCK pathway and summarize the current status of the development of ROCK inhibitors.

The Rho kinase inhibitor fasudil inhibits tumor progression in human and rat tumor models

The ability of cancer cells to undergo invasion and migration is a prerequisite for tumor metastasis. Rho, a Ras-related small GTPase, and the Rho-associated coiled coil-containing protein kinases (Rho kinases, ROCK1 and ROCK2) are key regulators of focal adhesion, actomyosin contraction, and thus cell motility. Inhibitors of this pathway have been shown to inhibit tumor cell motility and metastasis. Here, we show that fasudil [1-(5-isoquinolinesulfonyl)-homopiperazine], an orally available inhibitor of Rho kinases, and its metabolite 1-(hydroxy-5-isoquinoline sulfonyl-homopiperazine) (fasudil-OH) modify tumor cell morphology and inhibit tumor cell migration and anchorage-independent growth. In addition, we show that fasudil inhibited tumor progression in three independent animal models. In the MM1 peritoneal dissemination model, tumor burden and ascites production were reduced by > 50% (P < 0.05). In the HT1080 experimental lung metastasis model, fasudil decreased lung nodules by approximately 40% (P < 0.05). In the orthotopic breast cancer model with MDA-MB-231, there were 3-fold more tumor-free mice in the fasudil-treated group versus saline control group (P < 0.01). Fasudil has been approved for the treatment of cerebral vasospasm and associated cerebral ischemic symptoms. In patients, fasudil is well tolerated without any serious adverse reactions. Therefore, the concept of Rho kinase inhibition as an antimetastatic therapy for cancer can now be clinically explored.

Hepatocyte growth factor, its receptor, and their potential value in cancer therapies

Hepatocyte growth factor plays multiple roles in cancer, by acting as a motility and invasion stimulating factor, promoting metastasis and tumour growth. Furthermore, it acts as a powerful angiogenic factor. The pivotal role of this factor in cancer has indicated HGF as being a potential target in cancer therapies. The past few years have seen rapid progress in developing tools in targeting HGF, in the context of cancer therapies, including development of antagonists, small compounds, antibodies and genetic approaches. The current article discusses the potential value of HGF and its receptor as targets in cancer therapies, the current development in anti-HGF research, and the clinical value of HGF in prognosis and treatment.

Conditional ROCK activation in vivo induces tumor cell dissemination and angiogenesis

Progression of tumors to invasive and metastatic forms requires that tumor cells undergo dramatic morphologic changes, a process regulated by Rho GTPases. Elevated expression of RhoA and RhoC, as well as the Rho effector proteins ROCK I and ROCK II, are commonly observed in human cancers and are often associated with more invasive and metastatic phenotypes. To examine how ROCK contributes to the progression of solid tumors, we established a conditionally activated form of ROCK II by fusing the kinase domain to the estrogen receptor hormone-binding domain (ROCK:ER). ROCK:ER-expressing colon carcinoma cells grown as tumors in immunocompromised nude mice organized into discrete clusters surrounding blood vessels. However, ROCK:ER activation resulted in the aggressive dissemination of tumor cells into the surrounding stroma, indicating that increased ROCK signaling is sufficient to promote invasion from solid tumors. In addition, tumors in which ROCK:ER was activated were more highly vascularized, indicating that ROCK contributes to tumor angiogenesis. ROCK:ER activation resulted in changes to epithelial morphology and organization that facilitated motility in vitro, likely by inducing the redistribution of proteins such as ezrin, as well as adherens junction and extracellular matrix-binding proteins. These results suggest that ROCK inhibitors would be useful antimetastatic and antiangiogenic chemotherapeutic agents in tumors associated with elevated RhoA, RhoC, ROCK I, or ROCK II expression.