Cdc42-interacting protein 4 promotes breast cancer cell invasion and formation of invadopodia through activation of N-WASp

Endocytosis in cancer and cancer therapy

Endocytosis is a complex process whereby cell surface proteins, lipids and fluid from the extracellular environment are packaged, sorted and internalized into cells. Endocytosis is also a mechanism of drug internalization into cells. There are multiple routes of endocytosis that determine the fate of molecules, from degradation in the lysosomes to recycling back to the plasma membrane. The overall rates of endocytosis and temporal regulation of molecules transiting through endocytic pathways are also intricately linked with signalling outcomes. This process relies on an array of factors, such as intrinsic amino acid motifs and post-translational modifications. Endocytosis is frequently disrupted in cancer. These disruptions lead to inappropriate retention of receptor tyrosine kinases on the tumour cell membrane, changes in the recycling of oncogenic molecules, defective signalling feedback loops and loss of cell polarity. In the past decade, endocytosis has emerged as a pivotal regulator of nutrient scavenging, response to and regulation of immune surveillance and tumour immune evasion, tumour metastasis and therapeutic drug delivery. This Review summarizes and integrates these advances into the understanding of endocytosis in cancer. The potential to regulate these pathways in the clinic to improve cancer therapy is also discussed.

ARHGAP17 regulates the spatiotemporal activity of Cdc42 at invadopodia

Invadopodia formation is regulated by Rho GTPases. However, the molecular mechanisms that control Rho GTPase signaling at invadopodia remain poorly understood. Here, we have identified ARHGAP17, a Cdc42-specific RhoGAP, as a key regulator of invadopodia in breast cancer cells and characterized a novel ARHGAP17-mediated signaling pathway that controls the spatiotemporal activity of Cdc42 during invadopodia turnover. Our results show that during invadopodia assembly, ARHGAP17 localizes to the invadopodia ring and restricts the activity of Cdc42 to the invadopodia core, where it promotes invadopodia growth. Invadopodia disassembly starts when ARHGAP17 translocates from the invadopodia ring to the core, in a process that is mediated by its interaction with the Cdc42 effector CIP4. Once at the core, ARHGAP17 inactivates Cdc42 to promote invadopodia disassembly. Our results in invadopodia provide new insights into the coordinated transition between the activation and inactivation of Rho GTPases.

Bending over backwards: BAR proteins and the actin cytoskeleton in mammalian receptor-mediated endocytosis

The role of the actin cytoskeleton during receptor-mediated endocytosis (RME) has been well characterized in yeast for many years. Only more recently has the interplay between the actin cytoskeleton and RME been extensively explored in mammalian cells. These studies have revealed the central roles of BAR proteins in RME, and have demonstrated significant roles of BAR proteins in linking the actin cytoskeleton to this cellular process. The actin cytoskeleton generates and transmits mechanical force to promote the extension of receptor-bound endocytic vesicles into the cell. Many adaptor proteins link and regulate the actin cytoskeleton at the sites of endocytosis. This review will cover key effectors, adaptors and signalling molecules that help to facilitate the invagination of the cell membrane during receptor-mediated endocytosis, including recent insights gained on the roles of BAR proteins. The final part of this review will explore associations of alterations to genes encoding BAR proteins with cancer.

Mechanical loading of intraluminal pressure mediates wound angiogenesis by regulating the TOCA family of F-BAR proteins

Angiogenesis is regulated in coordinated fashion by chemical and mechanical cues acting on endothelial cells (ECs). However, the mechanobiological mechanisms of angiogenesis remain unknown. Herein, we demonstrate a crucial role of blood flow-driven intraluminal pressure (IP) in regulating wound angiogenesis. During wound angiogenesis, blood flow-driven IP loading inhibits elongation of injured blood vessels located at sites upstream from blood flow, while downstream injured vessels actively elongate. In downstream injured vessels, F-BAR proteins, TOCA1 and CIP4, localize at leading edge of ECs to promote N-WASP-dependent Arp2/3 complex-mediated actin polymerization and front-rear polarization for vessel elongation. In contrast, IP loading expands upstream injured vessels and stretches ECs, preventing leading edge localization of TOCA1 and CIP4 to inhibit directed EC migration and vessel elongation. These data indicate that the TOCA family of F-BAR proteins are key actin regulatory proteins required for directed EC migration and sense mechanical cell stretching to regulate wound angiogenesis.

Chemical and mechanical cues coordinately regulate angiogenesis. Here, the authors show that blood flow-driven intraluminal pressure regulates wound angiogenesis. Findings indicate that TOCA family of F-BAR proteins act as actin regulators required for endothelial cell migration and sense mechanical cell stretching to regulate wound angiogenesis.

Bisphenol A replacement chemicals, BPF and BPS, induce protumorigenic changes in human mammary gland organoid morphology and proteome

SignificanceBisphenol A (BPA), found in many plastic products, has weak estrogenic effects that can be harmful to human health. Thus, structurally related replacements-bisphenol S (BPS) and bisphenol F (BPF)-are coming into wider use with very few data about their biological activities. Here, we compared the effects of BPA, BPS, and BPF on human mammary organoids established from normal breast tissue. BPS disrupted organoid architecture and induced supernumerary branching. At a proteomic level, the bisphenols altered the abundance of common targets and those that were unique to each compound. The latter included proteins linked to tumor-promoting processes. These data highlighted the importance of testing the human health effects of replacements that are structurally related to chemicals of concern.

CIP4 targeted to recruit GTP-Cdc42 involving in invadopodia formation via NF-κB signaling pathway promotes invasion and metastasis of CRC

Cdc42-interacting protein 4 (CIP4), a member of the F-BAR family, which plays an important role in regulating cell membrane and actin, has been reported to interact with Cdc42 and be closely associated with tumor invadopodia formation. In this study, we found that CIP4 expression was significantly higher in human CRC tissues and correlated with the CRC infiltrating depth and metastasis, as well as the lower survival rate in patients. In cultured CRC cells, knockdown of CIP4 inhibited cell migration and invasion ability in vitro and tumor metastasis in vivo, while the overexpression of CIP4 promoted invadopodia formation and matrix degradation ability. We then identified GTP-Cdc42 as a directly interactive protein of CIP4, which was upregulated and recruited by CIP4. Furthermore, activated NF-κB signaling pathway was found in CIP4 overexpression of CRC cells contributing to invadopodia formation, while the inhibition of either CIP4 or Cdc42 led to the suppression of the NF-κB pathway and resulted in a decreased quantity of invadopodia. Our findings suggested that CIP4 targets to recruit GTP-Cdc42 and directly combines with it to accelerate invadopodia formation and function by activating NF-κB signaling pathway, thus promoting CRC infiltration and metastasis.

Dysregulation of circulating CDC42 and its correlation with demographic characteristics, comorbidities, tumor features, chemotherapeutic regimen and survival profile in non-small-cell lung cancer patients

OBJECTIVE

Cell division control protein 42 (CDC42) induces the immune escape, represses the CD8⁺ T-cell activation, and further leads to the tumor metastasis in various neoplasms, whereas the correlation of circulating CDC42 with clinical features and prognosis of non-small-cell lung cancer (NSCLC) remains elusive. Hence, the current study aimed to investigate this topic.

METHODS

Peripheral blood mononuclear cells from 263 NSCLC patients before treatment and 50 health controls (HC) were used for CDC42 determination by reverse transcription quantitative polymerase chain reaction (RT-qPCR) assay.

RESULTS

CDC42 expression was higher in NSCLC patients than HCs (p < 0.001). Besides, elevated CDC42 expression was correlated with the occurrence of lymph node (LYN) metastasis (p = 0.003) and advanced TNM stage (p = 0.007), but not related to other tumor features, demographic characteristics, comorbidities, nor neoadjuvant/adjuvant chemotherapy (all p > 0.05). Additionally, elevated CDC42 expression was correlated with unfavorable accumulating disease-free survival (DFS) (p < 0.001) and overall survival (OS) (p = 0.025). More importantly, multivariate Cox's proportional hazard regression analysis revealed that elevated CDC42 expression (hazard ratio (HR): 1.284, p < 0.001) and higher TNM stage (HR: 1.428, p = 0.003) were independently associated with shorter DFS, meanwhile elevated CDC42 expression (HR: 1.193, p = 0.035), higher pathological grade (HR: 1.558, p = 0.003), higher TNM stage (HR: 1.703, p = 0.001) and higher Eastern Cooperative Oncology Group performance status (ECOG PS) score (HR: 1.538, p = 0.038) were independently correlated with unsatisfying OS.

CONCLUSION

Circulating CDC42 is highly expressed with its overexpression linked with LYN metastasis, poor DFS, and OS in NSCLC patients.

PDLIM1: Structure, function and implication in cancer

PDLIM1, a member of the PDZ-LIM family, is a cytoskeletal protein and functions as a platform to form distinct protein complexes, thus participating in multiple physiological processes such as cytoskeleton regulation and synapse formation. Emerging evidence demonstrates that PDLIM1 is dysregualted in a variety of tumors and plays essential roles in tumor initiation and progression. In this review, we summarize the structure and function of PDLIM1, as well as its important roles in human cancers.

NIBNA: A network-based node importance approach for identifying breast cancer drivers

MOTIVATION

Identifying meaningful cancer driver genes in a cohort of tumors is a challenging task in cancer genomics. Although existing studies have identified known cancer drivers, most of them focus on detecting coding drivers with mutations. It is acknowledged that non-coding drivers can regulate driver mutations to promote cancer growth. In this work, we propose a novel node importance based network analysis (NIBNA) framework to detect coding and non-coding cancer drivers. We hypothesize that cancer drivers are crucial to the formation of community structures in cancer network, and removing them from the network greatly perturbs the network structure thereby critically affecting the functioning of the network. NIBNA detects cancer drivers using a three-step process; first, a condition-specific network is built by incorporating gene expression data and gene networks, second, the community structures in the network are estimated and third, a centrality-based metric is applied to compute node importance.

RESULTS

We apply NIBNA to the BRCA dataset and it outperforms existing state-of-art methods in detecting coding cancer drivers. NIBNA also predicts 265 miRNA drivers and majority of these drivers have been validated in literature. Further we apply NIBNA to detect cancer subtype-specific drivers and several predicted drivers have been validated to be associated with cancer subtypes. Lastly, we evaluate NIBNA's performance in detecting epithelial-mesenchymal transition (EMT) drivers, and we confirmed 8 coding and 13 miRNA drivers in the list of known genes.

AVAILABILITY

The source code can be accessed at: https://github.com/mandarsc/NIBNA.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Identification of afzelin potential targets in inhibiting triple-negative breast cancer cell migration using reverse docking

BACKGROUND

Triple-negative breast cancer (TNBC) tends to be aggressive and metastatic, characteristics attributable to its cellular migration capabilities. Afzelin is a chemical compound with anti-metastatic potentials. This study aimed to predict proteins involved in TNBC cell migration which could be inhibited by afzelin.

METHODS

The protein database was constructed from the Kyoto Encyclopedia of Genes and Genomes pathways collection which related to cell motility, then screened for druggability using SuperTarget and Therapeutic Target Database. The involvement of druggable proteins in the TNBC metastasis process was investigated through existing publications in The National Center for Biotechnology Information PubMed database. Inhibitory potential of afzelin toward target proteins was compared to the proteins' known-inhibitor, using the reverse docking method.

RESULTS

Ten proteins identified as potential targets of afzelin, with the top 3 being ERK2, KRas, and FAK, respectively. Afzelin's 3-O-rhamnoside group played a dominant role in forming hydrogen bonds with the target proteins. Further analysis with STRING suggested that afzelin might be able to inhibit chemotaxis and haptotaxis of TNBC cells.

CONCLUSIONS

Afzelin was predicted to inhibit TNBC cell motility, by targeting ERK2, KRas, and FAK activation.

Selective stabilization of multiple promoter G-quadruplex DNA by using 2-phenyl-1H-imidazole-based tanshinone IIA derivatives and their potential suppressing function in the metastatic breast cancer

The G-quadruplex (G4) DNA, which has been developed as a potential anticancer target in drug screening and design, plays a crucial role in the oncogene transcription and translation. Tanshinone IIA derivatives with a planar heterocycle structure may function as G4 stabilizers. We present an innovative case of imidazole-based tanshinone IIA derivatives (1-8) especially compound 4 that improve the selectivity and the binding affinity with G4 DNA and enhance the target tumor inhibition. Cellular and in vivo experiments indicate that the tanshinone IIA derivative 4 inhibits the growth, metastasis, and angiogenesis of triple-negative breast cancer cells possibly through the stabilization of multiple G4 DNAs (e.g., c-myc, K-ras, and VEGF) to induce DNA damage. Further investigation of the intermolecular interaction and the molecular docking indicates that tanshinone IIA derivatives have better selective binding capability to various G4 DNAs than to double-stranded DNA. These findings provide guidance in modifying the molecular structures of tanshinone IIA derivatives and reveal their potential to function as specific G4 stabilizers.

Intersection of TKS5 and FGD1/CDC42 signaling cascades directs the formation of invadopodia

Tumor cells exposed to a physiological matrix of type I collagen fibers form elongated collagenolytic invadopodia, which differ from dotty-like invadopodia forming on the gelatin substratum model. The related scaffold proteins, TKS5 and TKS4, are key components of the mechanism of invadopodia assembly. The molecular events through which TKS proteins direct collagenolytic invadopodia formation are poorly defined. Using coimmunoprecipitation experiments, identification of bound proteins by mass spectrometry, and in vitro pull-down experiments, we found an interaction between TKS5 and FGD1, a guanine nucleotide exchange factor for the Rho-GTPase CDC42, which is known for its role in the assembly of invadopodial actin core structure. A novel cell polarity network is uncovered comprising TKS5, FGD1, and CDC42, directing invadopodia formation and the polarization of MT1-MMP recycling compartments, required for invadopodia activity and invasion in a 3D collagen matrix. Additionally, our data unveil distinct signaling pathways involved in collagenolytic invadopodia formation downstream of TKS4 or TKS5 in breast cancer cells.

High formin binding protein 17 (FBP17) expression indicates poor differentiation and invasiveness of ductal carcinomas

Formin binding protein 17 (FBP17) belongs to Cdc-42 interacting protein 4 subfamily of F-BAR proteins. Recently, we had reported that FBP17 was overexpressed in invasive breast cancer cells and interacts with the actin regulatory proteins. We also reported that FBP17 promotes invadopodia formation and enhances extracellular matrix degradation. The current study determines FBP17 expression in invasive ductal carcinomas (IDCs) using breast cancer tissue microarrays (TMAs) (82 IDCs with variable receptor status and 8 Normal adjacent tissues) and its correlation with the clinico-pathological features. Immunohistochemistry of human breast cancer TMAs showed the significant elevation in the levels of FBP17 in breast cancer tissues than the normal (p ≤ 0.0001). Interestingly, FBP17 had a higher expression in invasive molecular subtypes HER2 and TNBC (p ≤ 0.05). Similarly, tumors with lymph node positive status showed elevated FBP17 expression in HER2 and TNBC subtypes (p ≤ 0.05). Surprisingly, grade 3 tumors demonstrated higher FBP17 expression (p ≤ 0.01) indicating its role in poorly differentiated tumors. Together, the data demonstrates the overexpression of FBP17 in invasive and poorly differentiated tumors. Understanding the role of FBP17 in poor differentiation and invasion of tumors in molecular subtypes at various level might represent as a potential molecular target against the disease.

Actin regulators in cancer progression and metastases: From structure and function to cytoskeletal dynamics

The cytoskeleton is a central factor contributing to various hallmarks of cancer. In recent years, there has been increasing evidence demonstrating the involvement of actin regulatory proteins in malignancy, and their dysregulation was shown to predict poor clinical prognosis. Although enhanced cytoskeletal activity is often associated with cancer progression, the expression of several inducers of actin polymerization is remarkably reduced in certain malignancies, and it is not completely clear how these changes promote tumorigenesis and metastases. The complexities involved in cytoskeletal induction of cancer progression therefore pose considerable difficulties for therapeutic intervention; it is not always clear which cytoskeletal regulator should be targeted in order to impede cancer progression, and whether this targeting may inadvertently enhance alternative invasive pathways which can aggravate tumor growth. The entire constellation of cytoskeletal machineries in eukaryotic cells are numerous and complex; the system is comprised of and regulated by hundreds of proteins, which could not be covered in a single review. Therefore, we will focus here on the actin cytoskeleton, which encompasses the biological machinery behind most of the key cellular functions altered in cancer, with specific emphasis on actin nucleating factors and nucleation-promoting factors. Finally, we discuss current therapeutic strategies for cancer which aim to target the cytoskeleton.

CBNA: A control theory based method for identifying coding and non-coding cancer drivers

A key task in cancer genomics research is to identify cancer driver genes. As these genes initialise and progress cancer, understanding them is critical in designing effective cancer interventions. Although there are several methods developed to discover cancer drivers, most of them only identify coding drivers. However, non-coding RNAs can regulate driver mutations to develop cancer. Hence, novel methods are required to reveal both coding and non-coding cancer drivers. In this paper, we develop a novel framework named Controllability based Biological Network Analysis (CBNA) to uncover coding and non-coding cancer drivers (i.e. miRNA cancer drivers). CBNA integrates different genomic data types, including gene expression, gene network, mutation data, and contains a two-stage process: (1) Building a network for a condition (e.g. cancer condition) and (2) Identifying drivers. The application of CBNA to the BRCA dataset demonstrates that it is more effective than the existing methods in detecting coding cancer drivers. In addition, CBNA also predicts 17 miRNA drivers for breast cancer. Some of these predicted miRNA drivers have been validated by literature and the rest can be good candidates for wet-lab validation. We further use CBNA to detect subtype-specific cancer drivers and several predicted drivers have been confirmed to be related to breast cancer subtypes. Another application of CBNA is to discover epithelial-mesenchymal transition (EMT) drivers. Of the predicted EMT drivers, 7 coding and 6 miRNA drivers are in the known EMT gene lists.

Cancer is a disease of cells in human body and it causes a high rate of deaths worldwide. There has been evidence that coding and non-coding RNAs are key players in the initialisation and progression of cancer. These coding and non-coding RNAs are considered as cancer drivers. To design better diagnostic and therapeutic plans for cancer patients, we need to know the roles of cancer drivers in cancer development as well as their regulatory mechanisms in the human body. In this study, we propose a novel framework to identify coding and non-coding cancer drivers (i.e. miRNA cancer drivers). The proposed framework is applied to the breast cancer dataset for identifying drivers of breast cancer. Comparing our method with existing methods in predicting coding cancer drivers, our method shows a better performance. Several miRNA cancer drivers predicted by our method have already been validated by literature. The predicted cancer drivers by our method could be a potential source for further wet-lab experiments to discover the causes of cancer. In addition, the proposed method can be used to detect drivers of cancer subtypes and drivers of the epithelial-mesenchymal transition in cancer.

A two-gene epigenetic signature for the prediction of response to neoadjuvant chemotherapy in triple-negative breast cancer patients

Background

Pathological complete response (pCR) after neoadjuvant chemotherapy (NAC) in triple-negative breast cancer (TNBC) varies between 30 and 40% approximately. To provide further insight into the prediction of pCR, we evaluated the role of an epigenetic methylation-based signature.

Methods

Epigenetic assessment of DNA extracted from biopsy archived samples previous to NAC from TNBC patients was performed. Patients included were categorized according to previous response to NAC in responder (pCR or residual cancer burden, RCB = 0) or non-responder (non-pCR or RCB > 0) patients. A methyloma study was performed in a discovery cohort by the Infinium HumanMethylation450 BeadChip (450K array) from Illumina. The epigenetic silencing of those methylated genes in the discovery cohort were validated by bisulfite pyrosequencing (PyroMark Q96 System version 2.0.6, Qiagen) and qRT-PCR in an independent cohort of TN patients and in TN cell lines.

Results

Twenty-four and 30 patients were included in the discovery and validation cohorts, respectively. In the discovery cohort, nine genes were differentially methylated: six presented higher methylation in non-responder patients (LOC641519, LEF1, HOXA5, EVC2, TLX3, CDKL2) and three greater methylation in responder patients (FERD3L, CHL1, and TRIP10). After validation, a two-gene (FER3L and TRIP10) epigenetic score predicted RCB = 0 with an area under the ROC curve (AUC) = 0.905 (95% CI = 0.805–1.000). Patients with a positive epigenetic two-gene score showed 78.6% RCB = 0 versus only 10.7% RCB = 0 if signature were negative.

Conclusions

These results suggest that pCR in TNBC could be accurately predicted with an epigenetic signature of FERD3L and TRIP10 genes. Further prospective validation of these findings is warranted.

Electronic supplementary material

The online version of this article (10.1186/s13148-019-0626-0) contains supplementary material, which is available to authorized users.

Tissue engineering the cancer microenvironment-challenges and opportunities

Mechanosensing is increasingly recognised as important for tumour progression. Tumours become stiff and the forces that normally balance in the healthy organism break down and become imbalanced, leading to increases in migration, invasion and metastatic dissemination. Here, we review recent advances in our understanding of how extracellular matrix properties, such as stiffness, viscoelasticity and architecture control cell behaviour. In addition, we discuss how the tumour microenvironment can be modelled in vitro, capturing these mechanical aspects, to better understand and develop therapies against tumour spread. We argue that by gaining a better understanding of the microenvironment and the mechanical forces that govern tumour dynamics, we can make advances in combatting cancer dormancy, recurrence and metastasis.

BAR domain proteins-a linkage between cellular membranes, signaling pathways, and the actin cytoskeleton

Actin filament assembly typically occurs in association with cellular membranes. A large number of proteins sit at the interface between actin networks and membranes, playing diverse roles such as initiation of actin polymerization, modulation of membrane curvature, and signaling. Bin/Amphiphysin/Rvs (BAR) domain proteins have been implicated in all of these functions. The BAR domain family of proteins comprises a diverse group of multi-functional effectors, characterized by their modular architecture. In addition to the membrane-curvature sensing/inducing BAR domain module, which also mediates antiparallel dimerization, most contain auxiliary domains implicated in protein-protein and/or protein-membrane interactions, including SH3, PX, PH, RhoGEF, and RhoGAP domains. The shape of the BAR domain itself varies, resulting in three major subfamilies: the classical crescent-shaped BAR, the more extended and less curved F-BAR, and the inverse curvature I-BAR subfamilies. Most members of this family have been implicated in cellular functions that require dynamic remodeling of the actin cytoskeleton, such as endocytosis, organelle trafficking, cell motility, and T-tubule biogenesis in muscle cells. Here, we review the structure and function of mammalian BAR domain proteins and the many ways in which they are interconnected with the actin cytoskeleton.

Modeling Membrane Curvature Generation due to Membrane⁻Protein Interactions

To alter and adjust the shape of the plasma membrane, cells harness various mechanisms of curvature generation. Many of these curvature generation mechanisms rely on the interactions between peripheral membrane proteins, integral membrane proteins, and lipids in the bilayer membrane. Mathematical and computational modeling of membrane curvature generation has provided great insights into the physics underlying these processes. However, one of the challenges in modeling these processes is identifying the suitable constitutive relationships that describe the membrane free energy including protein distribution and curvature generation capability. Here, we review some of the commonly used continuum elastic membrane models that have been developed for this purpose and discuss their applications. Finally, we address some fundamental challenges that future theoretical methods need to overcome to push the boundaries of current model applications.

High expression of FBP17 in invasive breast cancer cells promotes invadopodia formation

Metastatic spread of the cancer is usually the consequence of the activation of signaling pathways that generate cell motility and tissue invasion. Metastasis involves the reorganization of cytoskeleton and cell shape for the swift movement of the cells through extracellular matrix. Previously, we have described the invasive and metastatic role played by one of the members (Toca-1) of CIP4 subfamily of F-BAR proteins. In the present study, we address the role of another member (FBP17) of same family in the invasion breast cancer cells. Here, we report that the formin-binding protein 17 (FBP17) is highly expressed at both mRNA and protein levels in breast cancer cells. The study showed the association of FBP17 with cytoskeletal actin regulatory proteins like dynamin and cortactin. To determine its role in extracellular matrix (ECM) degradation, we achieved stable knockdown of FBP17 in MDA-MB-231 cells. FBP17 knockdown cells showed a defect and were found to be compromised in the degradation of ECM indicating the role of FBP17 in the invasion of breast cancer cells. Our results suggest that FBP17 is highly expressed in breast cancer cells and facilitates the invasion of breast cancer cells.

Regulating Cdc42 and Its Signaling Pathways in Cancer: Small Molecules and MicroRNA as New Treatment Candidates

Despite great improvements in the diagnosis and treatment of neoplasms, metastatic disease is still the leading cause of death in cancer patients, with mortality rates still rising. Given this background, new ways to treat cancer will be important for development of improved cancer control strategies. Cdc42 is a member of the Rho GTPase family and plays an important role in cell-to-cell adhesion, formation of cytoskeletal structures, and cell cycle regulation. It thus influences cellular proliferation, transformation, and homeostasis, as well as the cellular migration and invasion processes underlying tumor formation. Cdc42 acts as a collection point for signal transduction and regulates multiple signaling pathways. Moreover, recent studies show that in most human cancers Cdc42 is abnormally expressed and promoting neoplastic growth and metastasis. Regarding possible new treatments for cancer, miRNA and small molecules targeting Cdc42 and related pathways have been recently found to be effective on cancer. In this review, we analyze the newly recognized regulation mechanisms for Cdc42 and Cdc42-related signal pathways, and particularly new treatments using small molecules and miRNAs to inhibit the abnormal overexpression of Cdc42 that may slow down the metastasis process, improve cancer therapy and lead to novel strategies for development of antineoplastic drugs.

Stress-activated MAPKs and CRM1 regulate the subcellular localization of Net1A to control cell motility and invasion

The neuroepithelial cell transforming gene 1A (Net1A, an isoform of Net1) is a RhoA subfamily guanine nucleotide exchange factor (GEF) that localizes to the nucleus in the absence of stimulation, preventing it from activating RhoA. Once relocalized in the cytosol, Net1A stimulates cell motility and extracellular matrix invasion. In the present work, we investigated mechanisms responsible for the cytosolic relocalization of Net1A. We demonstrate that inhibition of MAPK pathways blocks Net1A relocalization, with cells being most sensitive to JNK pathway inhibition. Moreover, activation of the JNK or p38 MAPK family pathway is sufficient to elicit Net1A cytosolic localization. Net1A relocalization stimulated by EGF or JNK activation requires nuclear export mediated by CRM1. JNK1 (also known as MAPK8) phosphorylates Net1A on serine 52, and alanine substitution at this site prevents Net1A relocalization caused by EGF or JNK activation. Glutamic acid substitution at this site is sufficient for Net1A relocalization and results in elevated RhoA signaling to stimulate myosin light chain 2 (MLC2, also known as MYL2) phosphorylation and F-actin accumulation. Net1A S52E expression stimulates cell motility, enables Matrigel invasion and promotes invadopodia formation. These data highlight a novel mechanism for controlling the subcellular localization of Net1A to regulate RhoA activation, cell motility, and invasion.

The Arp2/3 Regulatory System and Its Deregulation in Cancer

The Arp2/3 complex is an evolutionary conserved molecular machine that generates branched actin networks. When activated, the Arp2/3 complex contributes the actin branched junction and thus cross-links the polymerizing actin filaments in a network that exerts a pushing force. The different activators initiate branched actin networks at the cytosolic surface of different cellular membranes to promote their protrusion, movement, or scission in cell migration and membrane traffic. Here we review the structure, function, and regulation of all the direct regulators of the Arp2/3 complex that induce or inhibit the initiation of a branched actin network and that controls the stability of its branched junctions. Our goal is to present recent findings concerning novel inhibitory proteins or the regulation of the actin branched junction and place these in the context of what was previously known to provide a global overview of how the Arp2/3 complex is regulated in human cells. We focus on the human set of Arp2/3 regulators to compare normal Arp2/3 regulation in untransformed cells to the deregulation of the Arp2/3 system observed in patients affected by various cancers. In many cases, these deregulations promote cancer progression and have a direct impact on patient survival.

VCA nanobodies target N-WASp to reduce invadopodium formation and functioning

Invasive cancer cells develop small actin-based protrusions called invadopodia, which perform a primordial role in metastasis and extracellular matrix remodelling. Neural Wiskott-Aldrich syndrome protein (N-WASp) is a scaffold protein which can directly bind to actin monomers and Arp2/3 and is a crucial player in the formation of an invadopodium precursor. Expression modulation has pointed to an important role for N-WASp in invadopodium formation but the role of its C-terminal VCA domain in this process remains unknown. In this study, we generated alpaca nanobodies against the N-WASp VCA domain and investigated if these nanobodies affect invadopodium formation. By using this approach, we were able to study functions of a selected functional/structural N-WASp protein domain in living cells, without requiring overexpression, dominant negative mutants or siRNAs which target the gene, and hence the entire protein. When expressed as intrabodies, the VCA nanobodies significantly reduced invadopodium formation in both MDA-MB-231 breast cancer and HNSCC61 head and neck squamous cancer cells. Furthermore, expression of distinct VCA Nbs (VCA Nb7 and VCA Nb14) in PC-3 prostate cancer cells resulted in reduced overall matrix degradation without affecting MMP9 secretion/activation or MT1-MMP localisation at invadopodial membranes. From these results, we conclude that we have generated nanobodies targeting N-WASp which reduce invadopodium formation and functioning, most likely via regulation of N-WASp—Arp2/3 complex interaction, indicating that this region of N-WASp plays an important role in these processes.

Paving the Rho in cancer metastasis: Rho GTPases and beyond

Malignant carcinomas are often characterized by metastasis, the movement of carcinoma cells from a primary site to colonize distant organs. For metastasis to occur, carcinoma cells first must adopt a pro-migratory phenotype and move through the surrounding stroma towards a blood or lymphatic vessel. Currently, there are very limited possibilities to target these processes therapeutically. The family of Rho GTPases is an ubiquitously expressed division of GTP-binding proteins involved in the regulation of cytoskeletal dynamics and intracellular signaling. The best characterized members of the Rho family GTPases are RhoA, Rac1 and Cdc42. Abnormalities in Rho GTPase function have major consequences for cancer progression. Rho GTPase activation is driven by cell surface receptors that activate GTP exchange factors (GEFs) and GTPase-activating proteins (GAPs). In this review, we summarize our current knowledge on Rho GTPase function in the regulation of metastasis. We will focus on key discoveries in the regulation of epithelial-mesenchymal-transition (EMT), cell-cell junctions, formation of membrane protrusions, plasticity of cell migration and adaptation to a hypoxic environment. In addition, we will emphasize on crosstalk between Rho GTPase family members and other important oncogenic pathways, such as cyclic AMP-mediated signaling, canonical Wnt/β-catenin, Yes-associated protein (YAP) and hypoxia inducible factor 1α (Hif1α) and provide an overview of the advancements and challenges in developing pharmacological tools to target Rho GTPase and the aforementioned crosstalk in the context of cancer therapeutics.

CDC42-interacting protein 4 promotes metastasis of nasopharyngeal carcinoma by mediating invadopodia formation and activating EGFR signaling

Background

Nasopharyngeal carcinoma (NPC) is a common malignancy in Southern China and Southeast Asia. In this study, we investigated the functional and molecular mechanisms by which CDC42-interacting protein 4 (CIP4) influences NPC.

Methods

The expression levels of CIP4 were examined by Western blot, qRT-PCR or IHC. MTT assay was used to detect the proliferative rate of NPC cells. The invasive abilities were examined by matrigel and transwell assay. The metastatic abilities of NPC cells were revealed in BALB/c nude mice.

Results

We report that CIP4 is required for NPC cell motility and invasion. CIP4 promotes the activation of N-WASP that controls invadopodia formation and activates EGFR signaling, which induces downstream MMP2 (matrix metalloproteinase 2) upregulation. In addition, CIP4 could promote NPC metastasis by activating the EGFR pathway. In nude mouse models, distant metastasis was significantly inhibited in CIP4-silenced groups. High CIP4 expression is an independent adverse prognostic factor of overall survival (OS) and distant metastasis-free survival (DMFS).

Conclusion

We identify the critical role of CIP4 in metastasis of NPC which suggest that CIP4 may be a potential therapeutic target of NPC patients.

Defining functional interactions during biogenesis of epithelial junctions

In spite of extensive recent progress, a comprehensive understanding of how actin cytoskeleton remodelling supports stable junctions remains to be established. Here we design a platform that integrates actin functions with optimized phenotypic clustering and identify new cytoskeletal proteins, their functional hierarchy and pathways that modulate E-cadherin adhesion. Depletion of EEF1A, an actin bundling protein, increases E-cadherin levels at junctions without a corresponding reinforcement of cell–cell contacts. This unexpected result reflects a more dynamic and mobile junctional actin in EEF1A-depleted cells. A partner for EEF1A in cadherin contact maintenance is the formin DIAPH2, which interacts with EEF1A. In contrast, depletion of either the endocytic regulator TRIP10 or the Rho GTPase activator VAV2 reduces E-cadherin levels at junctions. TRIP10 binds to and requires VAV2 function for its junctional localization. Overall, we present new conceptual insights on junction stabilization, which integrate known and novel pathways with impact for epithelial morphogenesis, homeostasis and diseases.

Formation and reinforcement of E-cadherin-mediated adhesion depends on intracellular trafficking and interactions with the actin cytoskeleton, but how these are coordinated is not known. Here the authors conduct a focused phenotypic screen to identify new pathways regulating cell–cell junction homeostasis.

Identification of novel biomarkers associated with poor patient outcomes in invasive breast carcinoma

Breast carcinoma (BC) corresponds to 23 % of all cancers in women, with 1.38 million new cases and 460,000 deaths worldwide annually. Despite the significant advances in the identification of molecular markers and different modalities of treatment for primary BC, the ability to predict its metastatic behavior is still limited. The purpose of this study was to identify novel molecular markers associated with distinct clinical outcomes in a Brazilian cohort of BC patients. We generated global gene expression profiles using tumor samples from 24 patients with invasive ductal BC who were followed for at least 5 years, including a group of 15 patients with favorable outcomes and another with nine patients who developed metastasis. We identified a set of 58 differentially expressed genes (p ≤ 0.01) between the two groups. The prognostic value of this metastasis signature was corroborated by its ability to stratify independent BC patient datasets according to disease-free survival and overall survival. The upregulation of B3GNT7, PPM1D, TNKS2, PHB, and GTSE1 in patients with poor outcomes was confirmed by quantitative reverse transcription polymerase chain reaction (RT-qPCR) in an independent sample of patients with BC (47 with good outcomes and eight that presented metastasis). The expression of BCL2-associated agonist of cell death (BAD) protein was determined in 1276 BC tissue samples by immunohistochemistry and was consistent with the reduced BAD mRNA expression levels in metastatic cases, as observed in the oligoarray data. These findings point to novel prognostic markers that can distinguish breast carcinomas with metastatic potential from those with favorable outcomes.

Macrophages promote matrix protrusive and invasive function of breast cancer cells via MIP-1β dependent upregulation of MYO3A gene in breast cancer cells

The potential of a tumor cell to metastasize profoundly depends on its microenvironment, or "niche" interactions with local components. Tumor-associated-macrophages (TAMs) are the most abundant subpopulation of tumor stroma and represent a key component of tumor microenvironment. The dynamic interaction of cancer cells with neighboring TAMs actively drive cancer progression and metastatic transformation through intercellular signaling networks that need better elucidation. Thus, current study was planned for discerning paracrine communication networks operational between TAMs, and breast cancer cells with special reference to cancer cell invasion and dissemination to distant sites. Here, we report role of MIP-1β in enhancing invasive potential of metastatic breast cancer MDA-MB-231 and MDA-MB-468 cells. In addition, the poorly metastatic MCF-7 cells were also rendered invasive by MIP-1β. The MIP-1β-driven cancer cell invasion was dependent on upregulated expression levels of MYO3A gene, which encodes an unconventional myosin super-family protein harboring a kinase domain. Ex ovo study employing Chick-embryo-model and in vivo Syngenic 4T1/BALB/c mice-model further corroborated aforementioned in vitro findings, thereby substantiating their physiological relevance. Concordantly, human breast cancer specimen exhibited significant association between mRNA expression levels of MIP-1β and MYO3A. Both, MIP-1β and MYO3A exhibited positive correlation with MMP9, an established molecular determinant of cancer cell invasion. Higher expression of these genes correlated with poor survival of breast cancer patients. Collectively, these results point toward so far undisclosed MIP-1β/MYO3A axis being operational during metastasis, wherein macrophage-derived MIP-1β potentiated cancer cell invasion and metastasis via up regulation of MYO3A gene within cancer cells. Our study exposes opportunities for devising potential anti-metastatic strategies for efficient clinical management of breast cancer.

Mechanotransduction pulls the strings of matrix degradation at invadosome

Degradation of the extracellular matrix is a critical step of tumor cell invasion. Both protease-dependent and -independent mechanisms have been described as alternate processes in cancer cell motility. Interestingly, some effectors of protease-dependent degradation are focalized at invadosomes and are directly coupled with contractile and adhesive machineries composed of multiple mechanosensitive proteins. This review presents recent findings in protease-dependent mechanisms elucidating the ways the force affects extracellular matrix degradation by targeting protease expression and activity at invadosome. The aim is to highlight mechanosensing and mechanotransduction processes to direct the degradative activity at invadosomes, with the focus on membrane tension, proteases and mechanosensitive ion channels.

Linking up at the BAR: Oligomerization and F-BAR protein function

As cells grow, move, and divide, they must reorganize and rearrange their membranes and cytoskeleton. The F-BAR protein family links cellular membranes with actin cytoskeletal rearrangements in processes including endocytosis, cytokinesis, and cell motility. Here we review emerging information on mechanisms of F-BAR domain oligomerization and membrane binding, and how these activities are coordinated with additional domains to accomplish scaffolding and signaling functions.

CIP4 promotes metastasis in triple-negative breast cancer and is associated with poor patient prognosis

Signaling via epidermal growth factor receptor (EGFR) and Src kinase pathways promote triple-negative breast cancer (TNBC) cell invasion and tumor metastasis. Here, we address the role of Cdc42-interacting protein-4 (CIP4) in TNBC metastasis in vivo, and profile CIP4 expression in human breast cancer patients. In human TNBC cells, CIP4 knock-down (KD) led to less sustained activation of Erk kinase and impaired cell motility compared to control cells. This correlated with significant defects in 3D invasion of surrounding extracellular matrix by CIP4 KD TNBC cells when grown as spheroid colonies. In mammary orthotopic xenograft assays using both human TNBC cells (MDA-MB-231, HCC 1806) and rat MTLn3 cells, CIP4 silencing had no overt effect on tumor growth, but significantly reduced the incidence of lung metastases in each tumor model. In human invasive breast cancers, high CIP4 levels was significantly associated with high tumor stage, TNBC and HER2 subtypes, and risk of progression to metastatic disease. Together, these results implicate CIP4 in promoting metastasis in TNBCs.

Invadopodia proteins, cortactin, N-WASP and WIP differentially promote local invasiveness in ameloblastoma

BACKGROUND

Cell migration and invasion through interstitial tissues are dependent upon several specialized characteristics of the migratory cell notably generation of proteolytic membranous protrusions or invadopodia. Ameloblastoma is a benign odontogenic epithelial neoplasm with a locally infiltrative behaviour. Cortactin and MMT1-MMP are two invadopodia proteins implicated in its local invasiveness. Other invadopodia regulators, namely N-WASP, WIP and Src kinase remain unclarified. This study addresses their roles in ameloblastoma.

MATERIALS AND METHOD

Eighty-seven paraffin-embedded ameloblastoma cases (20 unicystic, 47 solid/multicystic, 3 desmoplastic and 17 recurrent) were subjected to immunohistochemistry for expression of cortactin, N-WASP, WIP, Src kinase and F-actin, and findings correlated with clinicopathological parameters.

RESULTS

Invadopodia proteins (except Src kinase) and F-actin were widely detected in ameloblastoma (cortactin: n = 73/87, 83.9%; N-WASP: n = 59/87; 67.8%; WIP: n = 77/87; 88.5%; and F-actin: n = 87/87, 100%). Protein localization was mainly cytoplasmic and/or membranous, and occasionally nuclear for F-actin. Cortactin, which functions as an actin-scaffolding protein, demonstrated significantly higher expression levels within ameloblastoma tumoral epithelium than in stroma (P < 0.05). N-WASP, which coordinates actin polymerization and invadopodia-mediated extracellular matrix degradation, was overexpressed in the solid/multicystic subtype (P < 0.05). WIP, an upstream regulator of N-WASP, and F-actin were significantly upregulated along the tumour invasive front compared to tumour centres (P < 0.05). Except for males with cortactin overexpression, other clinical parameters (age, ethnicity and anatomical site) showed no significant correlations.

CONCLUSIONS

Present results suggest that local invasiveness of ameloblastoma is dependent upon the migratory potential of its tumour cells as defined by their distribution of cortactin, N-WASP and WIP in correlation with F-actin cytoskeletal dynamics.

Spatial control of active CDC-42 during collective migration of hypodermal cells in Caenorhabditis elegans

Collective epithelial cell migration requires the maintenance of cell-cell junctions while enabling the generation of actin-rich protrusions at the leading edge of migrating cells. Ventral enclosure of Caenorhabditis elegans embryos depends on the collective migration of anterior-positioned leading hypodermal cells towards the ventral midline where they form new junctions with their contralateral neighbours. In this study, we characterized the zygotic function of RGA-7/SPV-1, a CDC-42/Cdc42 and RHO-1/RhoA-specific Rho GTPase-activating protein, which controls the formation of actin-rich protrusions at the leading edge of leading hypodermal cells and the formation of new junctions between contralateral cells. We show that RGA-7 controls these processes in an antagonistic manner with the CDC-42's effector WSP-1/N-WASP and the CDC-42-binding proteins TOCA-1/2/TOCA1. RGA-7 is recruited to spatially distinct locations at junctions between adjacent leading cells, where it promotes the accumulation of clusters of activated CDC-42. It also inhibits the spreading of these clusters towards the leading edge of the junctions and regulates their accumulation and distribution at new junctions formed between contralateral leading cells. Our study suggests that RGA-7 controls collective migration and junction formation between epithelial cells by spatially restricting active CDC-42 within cell-cell junctions.

Allosteric N-WASP activation by an inter-SH3 domain linker in Nck

Actin filament networks assemble on cellular membranes in response to signals that locally activate neural Wiskott-Aldrich-syndrome protein (N-WASP) and the Arp2/3 complex. An inactive conformation of N-WASP is stabilized by intramolecular contacts between the GTPase binding domain (GBD) and the C helix of the verprolin-homology, connector-helix, acidic motif (VCA) segment. Multiple SH3 domain-containing adapter proteins can bind and possibly activate N-WASP, but it remains unclear how such binding events relieve autoinhibition to unmask the VCA segment and activate the Arp2/3 complex. Here, we have used purified components to reconstitute a signaling cascade driven by membrane-localized Src homology 3 (SH3) adapters and N-WASP, resulting in the assembly of dynamic actin networks. Among six SH3 adapters tested, Nck was the most potent activator of N-WASP-driven actin assembly. We identify within Nck a previously unrecognized activation motif in a linker between the first two SH3 domains. This linker sequence, reminiscent of bacterial virulence factors, directly engages the N-WASP GBD and competes with VCA binding. Our results suggest that animals, like pathogenic bacteria, have evolved peptide motifs that allosterically activate N-WASP, leading to localized actin nucleation on cellular membranes.

Endothelin A receptor drives invadopodia function and cell motility through the β-arrestin/PDZ-RhoGEF pathway in ovarian carcinoma

The endothelin-1 (ET-1)/ET A receptor (ETAR) signalling pathway is a well-established driver of epithelial ovarian cancer (EOC) progression. One key process promoted by ET-1 is tumor cell invasion, which requires the scaffolding functions of β-arrestin-1 (β-arr1) downstream of the receptor; however, the potential role of ET-1 in inducing invadopodia, which are crucial for cellular invasion and tumor metastasis, is completely unknown. We describe here that ET-1/ETAR, through β-arr1, activates RhoA and RhoC GTPase and downstream ROCK (Rho-associated coiled coil-forming kinase) kinase activity, promoting actin-based dynamic remodelling and enhanced cell invasion. This is accomplished by the direct interaction of β-arr1 with PDZ-RhoGEF (postsynaptic density protein 95/disc-large/zonula occludens-RhoGEF). Interestingly, ETAR-mediated invasive properties are related to the regulation of invadopodia, as evaluated by colocalization of actin with cortactin, as well as with TKS5 and MT1-MMP (membrane type 1-matrix metalloproteinase) with areas of matrix degradation, and activation of cofilin pathway, which is crucial for regulating invadopodia activity. Depletion of PDZ-RhoGEF, or β-arr1, or RhoC, as well as the treatment with the dual ET-1 receptor antagonist macitentan, significantly impairs invadopodia function, MMP activity and invasion, demonstrating that β-arr1/PDZ-RhoGEF interaction mediates ETAR-driven ROCK-LIMK-cofilin pathway through the control of RhoC activity. In vivo, macitentan is able to inhibit metastatic dissemination and cofilin phosphorylation. Collectively, our data unveil a noncanonical activation of the RhoC/ROCK pathway through the β-arr1/PDZ-RhoGEF complex as a regulator of ETAR-induced motility and metastasis, establishing ET-1 axis as a novel regulator of invadopodia protrusions through the RhoC/ROCK/LIMK/cofilin pathway during the initial steps of EOC invasion.

Different functional modes of BAR domain proteins in formation and plasticity of mammalian postsynapses

A plethora of cell biological processes involve modulations of cellular membranes. By using extended lipid-binding interfaces, some proteins have the power to shape membranes by attaching to them. Among such membrane shapers, the superfamily of Bin-Amphiphysin-Rvs (BAR) domain proteins has recently taken center stage. Extensive structural work on BAR domains has revealed a common curved fold that can serve as an extended membrane-binding interface to modulate membrane topologies and has allowed the grouping of the BAR domain superfamily into subfamilies with structurally slightly distinct BAR domain subtypes (N-BAR, BAR, F-BAR and I-BAR). Most BAR superfamily members are expressed in the mammalian nervous system. Neurons are elaborately shaped and highly compartmentalized cells. Therefore, analyses of synapse formation and of postsynaptic reorganization processes (synaptic plasticity) - a basis for learning and memory formation - has unveiled important physiological functions of BAR domain superfamily members. These recent advances, furthermore, have revealed that the functions of BAR domain proteins include different aspects. These functions are influenced by the often complex domain organization of BAR domain proteins. In this Commentary, we review these recent insights and propose to classify BAR domain protein functions into (1) membrane shaping, (2) physical integration, (3) action through signaling components, and (4) suppression of other BAR domain functions.

Centrosomal AKAP350 and CIP4 act in concert to define the polarized localization of the centrosome and Golgi in migratory cells

The acquisition of a migratory phenotype is central in processes as diverse as embryo differentiation and tumor metastasis. An early event in this phenomenon is the generation of a nucleus-centrosome-Golgi back-to-front axis. AKAP350 (also known as AKAP9) is a Golgi and centrosome scaffold protein that is involved in microtubule nucleation. AKAP350 interacts with CIP4 (also known as TRIP10), a cdc42 effector that regulates actin dynamics. The present study aimed to characterize the participation of centrosomal AKAP350 in the acquisition of migratory polarity, and the involvement of CIP4 in the pathway. The decrease in total or in centrosomal AKAP350 led to decreased formation of the nucleus-centrosome-Golgi axis and defective cell migration. CIP4 localized at the centrosome, which was enhanced in migratory cells, but inhibited in cells with decreased centrosomal AKAP350. A decrease in the CIP4 expression or inhibition of the CIP4-AKAP350 interaction also led to defective cell polarization. Centrosome positioning, but not nuclear movement, was affected by loss of CIP4 or AKAP350 function. Our results support a model in which AKAP350 recruits CIP4 to the centrosome, providing a centrosomal scaffold to integrate microtubule and actin dynamics, thus enabling centrosome polarization and ensuring cell migration directionality.

Role of the WASP and WAVE family proteins in breast cancer invasion and metastasis

The Wiskott–Aldrich syndrome protein (WASP) and WASP family verprolin-homologous protein (WAVE) family are a group of molecules that form a key link between GTPases and the actin cytoskeleton. The role of WASP/WAVE family proteins in the control of actin polymerization through activation of the actin-related protein 2/3 complex is critical in the formation of the actin-based membrane protrusions seen in cell migration and invasion. For this reason, the activity of the WASP/WAVE family in cancer cell invasion and migration has been of great interest in recent years. Many reports have highlighted the potential of targeting the WASP/WAVE family as a therapy for the prevention of cancer progression, in particular breast cancer. This review focuses on the role of the WASP/WAVE family in breast cancer cell invasion and migration and how this relates to the molecular mechanisms of WASP/WAVE activity, their exact contributions to the stages of cancer progression, and how this can lead to the development of anticancer drugs that target the WASP/WAVE family and related pathways.

Endophilin A2 Promotes TNBC Cell Invasion and Tumor Metastasis

Triple-negative breast cancers (TNBCs) are highly aggressive cancers that lack targeted therapies. However, EGFR is frequently activated in a subset of TNBCs and represents a viable clinical target. Because the endocytic adaptor protein Endophilin A2 (SH3GL1/Endo II) has been implicated in EGFR internalization, we investigated Endo II expression and function in human TNBCs. Endo II expression was high in several TNBC cells compared with normal breast epithelial cells. Stable knockdown (KD) of Endo II was achieved in two TNBC cell lines, and although cell viability was unaffected, defects in receptor-mediated endocytosis were observed. EGFR signaling to Erk and Akt kinases was impaired in Endo II KD cells, and this correlated with reduced rates of EGFR internalization and cell motility. Endo II KD cells also displayed defects in three dimensional (3D) cell invasion, and this correlated with impaired extracellular matrix degradation and internalization of MT1-MMP. Endo II silencing also caused a significant reduction in TNBC tumor growth and lung metastasis in mammary orthotopic tumor xenograft assays. In human breast tumor specimens, Endo II expression was highest in TNBC tumors compared with other subtypes, and at the level of gene expression, high Endo II was associated with reduced relapse-free survival in patients with basal-like breast cancers. Together, these results identify a positive role for Endo II in TNBC tumor metastasis and a potential link with poor prognosis.

IMPLICATIONS

Endophilin A2 and related adaptor proteins represent important signaling hubs to target in metastatic cancers.

Redox biology in normal cells and cancer: restoring function of the redox/Fyn/c-Cbl pathway in cancer cells offers new approaches to cancer treatment

This review discusses a unique discovery path starting with novel findings on redox regulation of precursor cell and signaling pathway function and identification of a new mechanism by which relatively small changes in redox status can control entire signaling networks that regulate self-renewal, differentiation, and survival. The pathway central to this work, the redox/Fyn/c-Cbl (RFC) pathway, converts small increases in oxidative status to pan-activation of the c-Cbl ubiquitin ligase, which controls multiple receptors and other proteins of central importance in precursor cell and cancer cell function. Integration of work on the RFC pathway with attempts to understand how treatment with systemic chemotherapy causes neurological problems led to the discovery that glioblastomas (GBMs) and basal-like breast cancers (BLBCs) inhibit c-Cbl function through altered utilization of the cytoskeletal regulators Cool-1/βpix and Cdc42, respectively. Inhibition of these proteins to restore normal c-Cbl function suppresses cancer cell division, increases sensitivity to chemotherapy, disrupts tumor-initiating cell (TIC) activity in GBMs and BLBCs, controls multiple critical TIC regulators, and also allows targeting of non-TICs. Moreover, these manipulations do not increase chemosensitivity or suppress division of nontransformed cells. Restoration of normal c-Cbl function also allows more effective harnessing of estrogen receptor-α (ERα)-independent activities of tamoxifen to activate the RFC pathway and target ERα-negative cancer cells. Our work thus provides a discovery strategy that reveals mechanisms and therapeutic targets that cannot be deduced by standard genetics analyses, which fail to reveal the metabolic information, isoform shifts, protein activation, protein complexes, and protein degradation critical to our discoveries.

Dynamins and BAR Proteins-Safeguards against Cancer

Dynamins and BAR proteins are crucial in a wide variety of cellular processes for their ability to mediate membrane remodeling, such as membrane curvature and membrane fission and fusion. In this review, we highlight dynamins and BAR proteins and the cellular mechanisms that are involved in the initiation and progression of cancer. We specifically discuss the roles of the seproteinsin endocytosis, endo-lysosomal trafficking, autophagy, and apoptosis as these processes are all tightly linked to membrane remodeling and cancer.

Dynamic shaping of cellular membranes by phospholipids and membrane-deforming proteins

All cellular compartments are separated from the external environment by a membrane, which consists of a lipid bilayer. Subcellular structures, including clathrin-coated pits, caveolae, filopodia, lamellipodia, podosomes, and other intracellular membrane systems, are molded into their specific submicron-scale shapes through various mechanisms. Cells construct their micro-structures on plasma membrane and execute vital functions for life, such as cell migration, cell division, endocytosis, exocytosis, and cytoskeletal regulation. The plasma membrane, rich in anionic phospholipids, utilizes the electrostatic nature of the lipids, specifically the phosphoinositides, to form interactions with cytosolic proteins. These cytosolic proteins have three modes of interaction: 1) electrostatic interaction through unstructured polycationic regions, 2) through structured phosphoinositide-specific binding domains, and 3) through structured domains that bind the membrane without specificity for particular phospholipid. Among the structured domains, there are several that have membrane-deforming activity, which is essential for the formation of concave or convex membrane curvature. These domains include the amphipathic helix, which deforms the membrane by hemi-insertion of the helix with both hydrophobic and electrostatic interactions, and/or the BAR domain superfamily, known to use their positively charged, curved structural surface to deform membranes. Below the membrane, actin filaments support the micro-structures through interactions with several BAR proteins as well as other scaffold proteins, resulting in outward and inward membrane micro-structure formation. Here, we describe the characteristics of phospholipids, and the mechanisms utilized by phosphoinositides to regulate cellular events. We then summarize the precise mechanisms underlying the construction of membrane micro-structures and their involvements in physiological and pathological processes.

Cdc42 expression in cervical cancer and its effects on cervical tumor invasion and migration

The aim of the present study was to examine Cdc42 expression in cervical cancer and explore its effects on invasion and migration capability of cervical cancer cells. Immunohistochemistry was used to detect Cdc42 expression in normal cervical tissues as well as CIN I or below, CIN II or above, and cervical cancer tissues. Western blot analysis was used to explore Cdc42 expression in normal cervical cell line Crl-2614 and cervical cancer cell line HeLa. Plasmids of constitutively active Cdc42 (Cdc42 CA), wild-type Cdc42 (Cdc42 WT) and dominant negative Cdc42 (Cdc42 DN) were transfected, respectively, into HeLa cells to investigate the impacts of Cdc42 on migration and invasion of cervical cancer cells using Transwell and on cytoskeleton microfilaments using confocal microscopy after immunofluorescence staining. Cdc42 expression was gradually increased in the order of cervical tissues with CIN I or below, CIN II or above and cancer, showing significant difference (P<0.05), and was significantly higher in HeLa cells than in Crl-2614 cells (P<0.05). Migration ability of HeLa cells transfected with Cdc42 CA was significantly higher than that of non-transfected, as well as Cdc42 WT- or Cdc42 DN-transfected HeLa cells (P<0.05). Overexpression of Cdc42 CA can promote filopodia formation in HeLa cells. We concluded that Cdc42 overexpression significantly improved the ability of cervical cancer cells to migrate possibly due to improved pseudopodia formation.

CIP4 promotes lung adenocarcinoma metastasis and is associated with poor prognosis

Aberrant Epidermal growth factor receptor (EGFR) signaling in non-small cell lung cancer (NSCLC) is linked to tumor progression, metastasis, and poor survival rates. Here, we report the role of Cdc42-interacting protein 4 (CIP4) in the regulation of NSCLC cell invasiveness and tumor metastasis. CIP4 was highly expressed in a panel of NSCLC cell lines and normal lung epithelial cell lines. Stable knock-down (KD) of CIP4 in lung adenocarcinoma H1299 cells, expressing wild-type EGFR, led to increased EGFR levels on the cell surface, and defects in sustained activation of Erk kinase in H1299 cells treated with EGF. CIP4 localized to leading edge projections in NSCLC cells, and CIP4 KD cells displayed defects in EGF-induced cell motility and invasion through extracellular matrix. This correlated with reduced expression and activity of matrix metalloproteinase-2 (MMP-2) in CIP4 KD cells compared to control. In xenograft assays, CIP4 silencing had no effect on tumor growth, but resulted in significant defects in spontaneous metastases to the lungs from these subcutaneous tumors. This correlated with reduced expression of the Erk target gene Zeb1, and the Zeb1 target gene MMP-2 in CIP4 KD tumors compared to control. CIP4 also enhanced rates of metastasis to the liver and lungs in an intrasplenic experimental metastasis model. In human NSCLC tumor sections, CIP4 expression was elevated ≥ 2-fold in 43% of adenocarcinomas and 32% of squamous carcinomas compared to adjacent normal lung tissues. Analysis of microarray data for NSCLC patients also revealed that high CIP4 transcript levels correlated with reduced overall survival. Together, these results identify CIP4 as a positive regulator of NSCLC metastasis, and a potential poor prognostic biomarker in lung adenocarcinoma.

Importance of RhoGTPases in formation, characteristics, and functions of invadosomes

Podosomes and invadopodia (collectively known as invadosomes) are specialized plasma-membrane actin-based microdomains that combine adhesive properties with matrix degrading and/or mechanosensor activities. These organelles have been extensively studied in vitro and current concerted efforts aim at establishing their physiological relevance and subsequent association with human diseases. Proper functioning of the bone, immune, and vascular systems is likely to depend on these structures while their occurrence in cancer cells appears to be linked to tumor metastasis. The elucidation of the mechanisms driving invadosome assembly is a prerequisite to understanding their role in vivo and ultimately to controlling their functions. Adhesive and soluble ligands act via transmembrane receptors that propagate signals to the cytoskeleton via small G proteins of the Rho family, assisted by tyrosine kinases and scaffold proteins to induce invadosome formation and rearrangements. Oncogene expression and cell-cell interactions may also trigger their assembly. Manipulation of the signals that regulate invadosome formation and dynamics could therefore be a strategy to interfere with their functions in a multitude of pathological settings, such as excessive bone breakdown, infections, vascular remodeling, transendothelial diapedesis, and metastasis.

PDZ and LIM domain protein 1(PDLIM1)/CLP36 promotes breast cancer cell migration, invasion and metastasis through interaction with α-actinin

Increased CLP36 expression has been found to be closely associated with breast cancer progression. However, whether and how it contributes to malignant behavior of breast cancer cells were not known. We show here that CLP36 is critical for promoting breast cancer cell migration and invasion in vitro and metastasis in vivo, whereas it is dispensable for breast cell proliferation and anchorage independent growth in vitro and tumor growth in vivo. CLP36 interacted with both α-actinin-1 and -4 in breast cancer cells. Depletion of either α-actinin-1 or -4 inhibited breast cancer cell migration. Furthermore, mutations inhibiting the α-actinin-binding activity abolished the ability of CLP36 to promote breast cancer cell migration. Finally, depletion of CLP36 or disruption of the CLP36-α-actinin complex in breast cancer cells substantially inhibited Cdc42 activation, cell polarization and migration. Our results identify CLP36 as an important regulator of breast cancer cell migration and metastasis, and shed light on how increased CLP36 expression contributes to progression of breast cancer.