Actin binding proteins: their ups and downs in metastatic life

Dynamical features of smooth muscle actin pathological mutants: The arginine-257(258)-Cysteine cases

The R257(8)C mutation in smooth muscle actins, ACTG2 and ACTA2, is the most frequent cause of severe genetic diseases: namely, visceral myopathy, and familial thoracic aortic aneurysms and dissections, which respectively, stem from impairment of the visceral and vascular muscle. The molecular mechanisms underlying such pathologies are not fully elucidated. In the absence of experimental data of WT and mutated actins in their monomeric (g-) and filamentous (f-) form, molecular dynamics can shed light on the role of the R257(8)C in protein structure and dynamics. Analysis of g-actins does not show significant differences between WT and mutated proteins suggesting the correct monomers folding. On the contrary, mutated filaments are destabilized. Subunits of R257C f-ACTG2 adopt non optimal angles and in R258C f-ACTA2 we observe depolymerization already in the simulated time frame. Overall, our data points to a crucial role of residue R257(8) in actin structure and dynamics, in particular when the protein assembles into the filament.

Bioinformatics analysis of PSAT1 loss identifies downstream pathways regulated in EGFR mutant NSCLC and a selective gene signature for predicting the risk of relapse

The majority of malignant tumors exhibit an altered metabolic phenotype that ultimately provides the required energy and molecular precursors necessary for unregulated cell division. Within this, phosphoserine aminotransferase 1 (PSAT1) is involved in de novo serine biosynthesis and its activity promotes various biochemical processes, including one-carbon metabolism. It also directly generates α-ketoglutarate (α-KG), a Kreb cycle intermediate and epigenetic-regulating metabolite. Prior studies examining PSAT1 depletion have identified individual affected downstream pathways, such as GSK3β and E2F, in several cancer types, including non-small-cell lung cancer (NSCLC). However, global gene expression examination in response to PSAT1 loss, particularly in EGFR mutant NSCLC, has not been unexplored. Transcriptional profiling of EGFR mutant NSCLC cells with or without stable knock-down of PSAT1 identified differentially expressed genes (DEGs) enriched in several metabolic pathways required for cell division, including amino acid and nucleotide biosynthesis. Supplementation studies involving non-essential amino acids, nucleosides and α-KG partially restored defects in anchorage-independent growth due to the knockdown of PSAT1. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analysis identified potential impacts on actin cytoskeleton arrangement and β-catenin activity, which were rescued by PSAT1 re-expression. Finally, a comparative analysis of PSAT1 DEGs against transcripts enriched in patient EGFR mutant lung tumors identified a gene signature that is associated with overall and relapse-free survival (RFS) and was able to distinguish low or high-risk populations for RFS in early-stage EGFR mutant NSCLC. Overall, investigating genes altered by PSAT1 loss confirmed known PSAT1-regulated cellular pathways, identified a previously unknown role in the mediation of cytoskeleton arrangement in EGFR mutant NSCLC cells and allowed for the characterization of a gene signature with putative predictive potential for RFS in early-stage disease.

The F-actin bundler SWAP-70 promotes tumor metastasis

Dynamic rearrangements of the F-actin cytoskeleton are a hallmark of tumor metastasis. Thus, proteins that govern F-actin rearrangements are of major interest for understanding metastasis and potential therapies. We hypothesized that the unique F-actin binding and bundling protein SWAP-70 contributes importantly to metastasis. Orthotopic, ectopic, and short-term tail vein injection mouse breast and lung cancer models revealed a strong positive dependence of lung and bone metastasis on SWAP-70. Breast cancer cell growth, migration, adhesion, and invasion assays revealed SWAP-70's key role in these metastasis-related cell features and the requirement for SWAP-70 to bind F-actin. Biophysical experiments showed that tumor cell stiffness and deformability are negatively modulated by SWAP-70. Together, we present a hitherto undescribed, unique F-actin modulator as an important contributor to tumor metastasis.

Recently reported cell migration inhibitors: Opportunities and challenges for antimetastatic agents

Antimetastatic agents are highly desirable for cancer treatment because of the severe medical challenges and high mortality resulting from tumor metastasis. Having demonstrated antimetastatic effects in numerous in vitro and in vivo studies, migration inhibitors present significant opportunities for developing a new class of anticancer drugs. To provide a useful overview on the latest research in migration inhibitors, this article first discusses their therapeutic significance, targetable proteins, and developmental avenues. Subsequently it reviews over 20 representative migration inhibitors reported in recent journals in terms of their inhibitory mechanism, potency, and potential clinical utility. The relevance of the target proteins to cellular migratory function is focused on as it is crucial for assessing the overall efficacy of the inhibitors.

Coronin 1C, Regulated by Multiple microRNAs, Facilitates Cancer Cell Aggressiveness in Pancreatic Ductal Adenocarcinoma

Coronin proteins are actin-related proteins containing WD repeat domains encoded by seven genes (CORO1A, CORO1B, CORO1C, CORO2A, CORO2B, CORO6, and CORO7) in the human genome. Analysis of large cohort data from The Cancer Genome Atlas revealed that expression of CORO1A, CORO1B, CORO1C, CORO2A, and CORO7 was significantly upregulated in pancreatic ductal adenocarcinoma (PDAC) tissues (p < 0.05). Moreover, high expression of CORO1C and CORO2A significantly predicted the 5 year survival rate of patients with PDAC (p = 0.0071 and p = 0.0389, respectively). In this study, we focused on CORO1C and investigated its functional significance and epigenetic regulation in PDAC cells. Knockdown assays using siRNAs targeting CORO1C were performed in PDAC cells. Aggressive cancer cell phenotypes, especially cancer cell migration and invasion, were inhibited by CORO1C knockdown. The involvement of microRNAs (miRNAs) is a molecular mechanism underlying the aberrant expression of cancer-related genes in cancer cells. Our in silico analysis revealed that five miRNAs (miR-26a-5p, miR-29c-3p, miR-130b-5p, miR-148a-5p, and miR-217) are putative candidate miRNAs regulating CORO1C expression in PDAC cells. Importantly, all five miRNAs exhibited tumor-suppressive functions and four miRNAs except miR-130b-5p negatively regulated CORO1C expression in PDAC cells. CORO1C and its downstream signaling molecules are potential therapeutic targets in PDAC.

Molecular dynamics simulation study on the structures of fascin mutants

Fascin is a filamentous actin (F-actin) bundling protein, which cross-links F-actin into bundles and becomes an important component of filopodia on the cell surface. Fascin is overexpressed in many types of cancers. The mutation of fascin affects its ability to bind to F-actin and the progress of cancer. In this paper, we have studied the effects of residues of K22, K41, K43, K241, K358, K399, and K471 using molecular dynamics (MD) simulation. For the strong-effect residues, that is, K22, K41, K43, K358, and K471, our results show that the mutation of K to A leads to large values of root mean square fluctuation (RMSF) around the mutated residues, indicating those residues are important for the flexibility and thermal stability. On the other hand, based on residue cross-correlation analysis, alanine mutations of these residues reinforce the correlation between residues. Together with the RMSF data, the local flexibility is extended to the entire protein by the strong correlations to influence the dynamics and function of fascin. By contrast, for the mutants of K241A and K399A those do not affect the function of fascin, the RMSF data do not show significant differences compared with wild-type fascin. These findings are in a good agreement with experimental studies.

The actin cytoskeleton: Morphological changes in pre- and fully developed lung cancer

Actin, a primary component of the cell cytoskeleton can have multiple isoforms, each of which can have specific properties uniquely suited for their purpose. These monomers are then bound together to form polymeric filaments utilizing adenosine triphosphate hydrolysis as a source of energy. Proteins, such as Arp2/3, VASP, formin, profilin, and cofilin, serve important roles in the polymerization process. These filaments can further be linked to form stress fibers by proteins called actin-binding proteins, such as α-actinin, myosin, fascin, filamin, zyxin, and epsin. These stress fibers are responsible for mechanotransduction, maintaining cell shape, cell motility, and intracellular cargo transport. Cancer metastasis, specifically epithelial mesenchymal transition (EMT), which is one of the key steps of the process, is accompanied by the formation of thick stress fibers through the Rho-associated protein kinase, MAPK/ERK, and Wnt pathways. Recently, with the advent of "field cancerization," pre-malignant cells have also been demonstrated to possess stress fibers and related cytoskeletal features. Analytical methods ranging from western blot and RNA-sequencing to cryo-EM and fluorescent imaging have been employed to understand the structure and dynamics of actin and related proteins including polymerization/depolymerization. More recent methods involve quantifying properties of the actin cytoskeleton from fluorescent images and utilizing them to study biological processes, such as EMT. These image analysis approaches exploit the fact that filaments have a unique structure (curvilinear) compared to the noise or other artifacts to separate them. Line segments are extracted from these filament images that have assigned lengths and orientations. Coupling such methods with statistical analysis has resulted in development of a new reporter for EMT in lung cancer cells as well as their drug responses.

Wound Healing from an Actin Cytoskeletal Perspective

Wound healing requires a complex cascade of highly controlled and conserved cellular and molecular processes. These involve numerous cell types and extracellular matrix molecules regulated by the actin cytoskeleton. This microscopic network of filaments is present within the cytoplasm of all cells and provides the shape and mechanical support required for cell movement and proliferation. Here, an overview of the processes of wound healing are described from the perspective of the cell in relation to the actin cytoskeleton. Key points of discussion include the role of actin, its binding proteins, signaling pathways, and events that play significant roles in the phases of wound healing. The identification of cytoskeletal targets that can be used to manipulate and improve wound healing is included as an emerging area of focus that may inform future therapeutic approaches to improve healing of complex wounds.

Statistical parametrization of cell cytoskeleton reveals lung cancer cytoskeletal phenotype with partial EMT signature

Epithelial–mesenchymal Transition (EMT) is a multi-step process that involves cytoskeletal rearrangement. Here, developing and using an image quantification tool, Statistical Parametrization of Cell Cytoskeleton (SPOCC), we have identified an intermediate EMT state with a specific cytoskeletal signature. We have been able to partition EMT into two steps: (1) initial formation of transverse arcs and dorsal stress fibers and (2) their subsequent conversion to ventral stress fibers with a concurrent alignment of fibers. Using the Orientational Order Parameter (OOP) as a figure of merit, we have been able to track EMT progression in live cells as well as characterize and quantify their cytoskeletal response to drugs. SPOCC has improved throughput and is non-destructive, making it a viable candidate for studying a broad range of biological processes. Further, owing to the increased stiffness (and by inference invasiveness) of the intermediate EMT phenotype compared to mesenchymal cells, our work can be instrumental in aiding the search for future treatment strategies that combat metastasis by specifically targeting the fiber alignment process.

A computational method for automated quantification of actin stress fiber alignment in fluorescence images of cultured cells is presented, used to detect changes in stress fiber organization during EMT, with pathways regulating actin dynamics manipulated leading to the discovery of a cytoskeletal phenotype.

miRNA-guided reprogramming of glucose and glutamine metabolism and its impact on cell adhesion/migration during solid tumor progression

MicroRNAs (miRNAs) are small, non-coding RNAs about 22 nucleotides in length that regulate the expression of target genes post-transcriptionally, and are highly involved in cancer progression. They are able to impact a variety of cell processes such as proliferation, apoptosis and differentiation and can consequently control tumor initiation, tumor progression and metastasis formation. miRNAs can regulate, at the same time, metabolic gene expression which, in turn, influences relevant traits of malignancy such as cell adhesion, migration and invasion. Since the interaction between metabolism and adhesion or cell movement has not, to date, been well understood, in this review, we will specifically focus on miRNA alterations that can interfere with some metabolic processes leading to the modulation of cancer cell movement. In addition, we will analyze the signaling pathways connecting metabolism and adhesion/migration, alterations that often affect cancer cell dissemination and metastasis formation.

Role of Swiprosin-1/EFHD2 as a biomarker in the development of chronic diseases

Swiprosin-1 or EFHD2, is a Ca²⁺ binding actin protein and its expression has been shown to be distinct in various cell types. The expression of swiprosin-1 is upregulated during the activation of immune cells, epithelial and endothelial cells. The expression of swiprosin-1 is regulated by diverse signaling pathways that are contingent upon the specific type of cells. The aim of this review is to summarize and provide an overview of the role of swiprosin-1 in pathophysiological conditions of cancers, cardiovascular diseases, diabetic nephropathy, neuropsychiatric diseases, and in the process of inflammation, immune response, and inflammatory diseases. Novel approaches for the targeting of swiprosin-1 as a biomarker in the early detection and prevention of various development of chronic diseases are also explored.

miR-195 Regulates Intestinal Epithelial Restitution after Wounding by altering Actin-Related Protein-2 Translation

Early gut epithelial restitution reseals superficial wounds after acute injury, but the exact mechanism underlying this rapid mucosal repair remains largely unknown. MicroRNA-195 (miR-195) is highly expressed in the gut epithelium and involved in many aspects of mucosal pathobiology. Actin-related proteins (ARPs) are key components essential for stimulation of actin polymerization and regulate cell motility. Here we reported that miR-195 modulates early intestinal epithelial restitution by altering ARP-2 expression at the translation level. MiR-195 directly interacted with the ARP-2 mRNA, and ectopically overexpressed miR-195 decreased ARP-2 protein without effect on its mRNA content. In contrast, miR-195 silencing by transfection with the anti-miR-195 increased ARP-2 protein expression. Decreased ARP-2 levels by miR-195 were associated with an inhibition of early epithelial restitution, as indicated by a decrease in cell migration over the wounded area. Elevation of cellular ARP-2 levels by transfection with its transgene restored cell migration after wounding in cells overexpressing miR-195. Polyamines were found to decrease miR-195 abundance and enhanced ARP-2 translation, thus promoting epithelial restitution after wounding. Moreover, increasing the levels of miR-195 disrupted F-actin cytoskeleton organization, which was prevented by ARP2 overexpression. These results indicate that miR-195 inhibits early epithelial restitution by decreasing ARP-2 translation and that miR-195 expression is negatively regulated by cellular polyamines.

Molecular Pathogenesis of the Coronin Family: CORO2A Facilitates Migration and Invasion Abilities in Oral Squamous Cell Carcinoma

In humans, the coronin family is composed of seven proteins containing WD-repeat domains that regulate actin-based cellular processes. Some members of the coronin family are closely associated with cancer cell migration and invasion. The Cancer Genome Atlas (TCGA) analysis revealed that CORO1C, CORO2A, and CORO7 were significantly upregulated in oral squamous cell carcinoma (OSCC) tissues (p < 0.05). Moreover, the high expression of CORO2A was significantly predictive of the 5-year survival rate of patients with OSCC (p = 0.0203). Overexpression of CORO2A was detected in OSCC clinical specimens by immunostaining. siRNA-mediated knockdown of CORO2A suppressed cancer cell migration and invasion abilities. Furthermore, we investigated the involvement of microRNAs (miRNAs) in the molecular mechanism underlying CORO2A overexpression in OSCC cells. TCGA analysis confirmed that tumor-suppressive miR-125b-5p and miR-140-5p were significantly downregulated in OSCC tissues. Notably, these miRNAs bound directly to the 3'-UTR of CORO2A and controlled CORO2A expression in OSCC cells. In summary, we found that aberrant expression of CORO2A facilitates the malignant transformation of OSCC cells, and that downregulation of tumor-suppressive miRNAs is involved in CORO2A overexpression. Elucidation of the interaction between genes and miRNAs will help reveal the molecular pathogenesis of OSCC.

ACTR3 promotes cell migration and invasion by inducing epithelial mesenchymal transition in pancreatic ductal adenocarcinoma

Background

Recurrence and metastasis are the major causes of pancreatic ductal adenocarcinoma (PDAC) mortality after treatment. The underlying molecular mechanism is poorly understood. Actin-related protein 3 (ACTR3) is an important component of the actin-related protein 2/3 complex, which is involved in the regulation of cell motility and epithelial mesenchymal transition (EMT) process. Previously published studies have indicated that ACTR3 expression is upregulated in several types of cancers, and promotes tumor development, including gastric cancer and hepatocellular carcinoma. However, to date, the expression levels and the role of ACTR3 in PDAC are not well understood.

Methods

In the present study, the expression levels of ACTR3 in PDAC tissue and the relationship of ACTR3 expression with clinical prognosis were analyzed by mRNA microarray and bioinformatics. The biological functions and underlying mechanism of ACTR3 in PDAC were examined by a series of assays, including Cell Counting Kit-8 (CCK-8), transwell assay, and Western blotting.

Results

We found that the expression of ACTR3 was significantly increased in PDAC tissues and cell lines. A higher expression of ACTR3 was predictive of poor outcome for patients with PDAC. In vitro, the knockdown of ACTR3 expression significantly inhibited the invasive and migratory capacity of PDAC cells, and altered the distribution of F-actin and the expression of EMT markers.

Conclusions

The findings of our study indicated that ACTR3 promotes cell migration and invasion by inducing EMT in PDAC, which may be a potential therapeutic target and prognostic indicator for PDAC patients.

Circulating Actin-Binding Proteins in Laryngeal Cancer: Its Relationship with Circulating Tumor Cells and Cells of the Immune System

We previously exposed the role of actin-binding proteins (ABPs) in cancer development and progression. In this paper, we studied the relationship between circulating ABPs and the number of ABP-expressing leukocytes and circulating tumor cells (CTCs) in patients with highly aggressive laryngeal squamous cell carcinoma (LSCC). The levels of cofilin (CFL1), profilin (PFN1), ezrin (EZR), fascin (FSCN1), and adenylate cyclase-associated protein 1 (CAP1) were determined using enzyme immunoassay. The ABP expression by the cellular pools was analyzed by flow cytometry. The highest levels of FSCN1 and EZR were found in the blood serum of LSCC patients. There was a difference in ABP expression between the pools of leukocytes and CTCs. Leukocytes were mainly represented by CAP1+ and FSCN1+ pools, and CTCs contained CAP1+, FSCN1+, and EZR+ cells. The serum FSCN1 level correlated with the number of FSCN1-containing and CFL1-containing leukocytes. Thus, the level of circulating EZR is likely related to its expression in CTCs. The levels of CFL1 and PFN1 are likely to be supported by the expression of these proteins by leukocytes. Both CTCs and leukocytes can be a source of FSCN1 and CAP1 in blood serum. The results suggest that serum proteins can be produced by various cells, thus indicating both cancer development and the response of the immune system to this process.

The elongation factor eEF1A2 controls translation and actin dynamics in dendritic spines

Synaptic plasticity involves structural modifications in dendritic spines that are modulated by local protein synthesis and actin remodeling. Here, we investigated the molecular mechanisms that connect synaptic stimulation to these processes. We found that the phosphorylation of isoform-specific sites in eEF1A2-an essential translation elongation factor in neurons-is a key modulator of structural plasticity in dendritic spines. Expression of a nonphosphorylatable eEF1A2 mutant stimulated mRNA translation but reduced actin dynamics and spine density. By contrast, a phosphomimetic eEF1A2 mutant exhibited decreased association with F-actin and was inactive as a translation elongation factor. Activation of metabotropic glutamate receptor signaling triggered transient dissociation of eEF1A2 from its regulatory guanine exchange factor (GEF) protein in dendritic spines in a phosphorylation-dependent manner. We propose that eEF1A2 establishes a cross-talk mechanism that coordinates translation and actin dynamics during spine remodeling.

Acupuncture Regulates Serum Differentially Expressed Proteins in Patients with Chronic Atrophic Gastritis: A Quantitative iTRAQ Proteomics Study

Objective

To identify differentially expressed proteins (DEPs) in sera of patients with chronic atrophic gastritis (CAG) using isobaric tags for relative and absolute quantitation (iTRAQ) and to explore acupuncture's mechanism in CAG.

Methods

Peripheral sera from 8 healthy volunteers (HC), 8 chronic nonatrophic gastritis (NAG) patients, 8 CAG patients, and 8 CAG patients who underwent acupuncture treatment (CAG + ACU) were collected followed by labeling with iTRAQ reagent for protein identification and quantification using two-dimensional liquid chromatography-tandem mass spectrometry (2D-LC-MS/MS). Representative DEPs were selected through bioinformatics, and proteins were verified by enzyme-linked immunosorbent assay (ELISA).

Results

A total of 4,448 unique peptides were identified, corresponding to 816 nonredundant proteins. A 1.4-fold difference was used as the threshold. Compared with the HC group, 75 and 106 DEPs were identified from CAG and NAG groups, respectively. Compared with the CAG group, 110 and 66 DEPs were identified from the NAG and CAG + ACU groups, respectively. The DEPs were mainly involved in protein binding and the Notch signaling pathway-related proteins, and the upregulated proteins included actin-binding proteins (thymosin beta-4, tropomyosin-4, profilin-1, transgelin-2), while the downregulated proteins included Notch2 and Notch3. After acupuncture, the expression of these proteins in CAG patients was less differentiated from that in healthy people. The level of the above 6 proteins were verified by ELISA, and the results were similar to the results of iTRAQ analysis.

Conclusions

Actin-binding proteins and Notch signaling pathway-related proteins were correlated with the development and progression of CAG and thus are potential diagnostic markers for CAG. Acupuncture may play a role in regulating actin-binding proteins and Notch signaling pathway-related proteins to play a therapeutic role in CAG.

Cancer type-specific alterations in actin genes: Worth a closer look?

Actins form a strongly conserved family of proteins that are central to the functioning of the actin cytoskeleton partaking in natural processes such as cell division, adhesion, contraction and migration. These processes, however, also occur during the various phases of cancer progression. Yet, surprisingly, alterations in the six human actin genes in cancer studies have received little attention and the focus was mostly on deregulated expression levels of actins and even more so of actin-binding or regulatory proteins. Starting from the early mutation work in the 1980s, we propose based on reviewing literature and data from patient cancer genomes that alterations in actin genes are different in distinct cancer subtypes, suggesting some specificity. These actin gene alterations include (missense) mutations, gene fusions and copy number alterations (deletions and amplifications) and we illustrate their occurrence for a limited number of examples including actin mutations in lymphoid cancers and nonmelanoma skin cancer and actin gene copy number alterations for breast, prostate and liver cancers. A challenge in the future will be to further sort out the specificity per actin gene, alteration type and cancer subtype. Even more challenging is (experimentally) distinguishing between cause and consequence: which alterations are passengers and which are involved in tumor progression of particular cancer subtypes?

Altered mechanical properties of actin fibers due to breast cancer invasion: parameter identification based on micropipette aspiration and multiscale tensegrity modeling

The biophysical properties of cells change with cancer invasion to fulfill their metastatic behavior. Cell softening induced by cancer is highly associated with alterations in cytoskeleton fibers. Changes in the mechanical properties of cytoskeletal fibers have not been quantified due to technical limitations. In this study, we used the micropipette aspiration technique to calculate and compare the viscoelastic properties of non-invasive and invasive breast cancer cells. We evaluated the mechanical properties of actin fibers and microtubules of two cancerous cell lines by using multiscale tensegrity modeling and an optimization method. Cancer invasion caused altered viscoelastic behavior of cells and the results of modeling showed changes in mechanical properties of major cytoskeleton fibers. The stiffness and viscosity constant of actin fibers in non-invasive cells were 1.28 and 2.27 times higher than those of the invasive cells, respectively. However, changes in mechanical properties of microtubules were minor. Immunofluorescent staining of fibers and their quantified distributions confirmed altered actin distribution among two cell lines, in contrast to microtubule distribution. This study highlights the function of cytoskeletal fibers in cancer progression, which could be of interest in designing therapeutic strategies to target cancer progress. Firstly, the viscoelastic behavior of non-invasive and invasive cells is examined with micropipette aspiration tests. A tensegrity model of cells is developed to mimic the viscoelastic behavior of cells, and tensegrity element stiffness is evaluated in an optimization procedure based on micropipette aspiration tests. Finally, by using immunofluorescent staining and confocal imaging, mechanical properties of actin filaments and microtubules of cancer cells are investigated during the course of metastasis.

Integrative molecular characterization of sarcomatoid and rhabdoid renal cell carcinoma

Sarcomatoid and rhabdoid (S/R) renal cell carcinoma (RCC) are highly aggressive tumors with limited molecular and clinical characterization. Emerging evidence suggests immune checkpoint inhibitors (ICI) are particularly effective for these tumors, although the biological basis for this property is largely unknown. Here, we evaluate multiple clinical trial and real-world cohorts of S/R RCC to characterize their molecular features, clinical outcomes, and immunologic characteristics. We find that S/R RCC tumors harbor distinctive molecular features that may account for their aggressive behavior, including BAP1 mutations, CDKN2A deletions, and increased expression of MYC transcriptional programs. We show that these tumors are highly responsive to ICI and that they exhibit an immune-inflamed phenotype characterized by immune activation, increased cytotoxic immune infiltration, upregulation of antigen presentation machinery genes, and PD-L1 expression. Our findings build on prior work and shed light on the molecular drivers of aggressivity and responsiveness to ICI of S/R RCC.

Sarcomatoid and rhabdoid tumours are highly aggressive forms of renal cell carcinoma that are also responsive to immunotherapy. In this study, the authors perform a comprehensive molecular characterization of these tumours discovering an enrichment of specific alterations and an inflamed phenotype.

Prognostic significance of FSCN family in multiple myeloma

Multiple myeloma (MM) is a hematologic tumor with monoclonal proliferation of malignant plasma cells in the bone marrow. Fascin (FSCN) is an actin-binding protein that plays a crucial role in cell migration and invasion, contributing to tumor metastasis. There are three members (FSCN1-3) in FSCN family. However, the prognostic role of FSCN family in MM remains unclear. In this study, we used four independent Gene Expression Omnibus (GEO) datasets to explore the relationships between FSCN1-3 expression profiles and patient survival in MM. We found that FSCN1 was dramatically down-regulated in MM compared to normal donors (p < 0.001) and monoclonal gammopathy of undetermined significance (MGUS) (p = 0.032). Patients with high expression of FSCN1 and FSCN2 had significantly longer OS (p = 0.023 and 0.028, respectively). Univariate and multivariate analysis showed that FSCN1 (p = 0.003, 0.002) and FSCN2 (p = 0.018, 0.013) were independent favorable prognostic factors for OS in MM. Moreover, the combination of high expression of FSCN1 and FSCN2 could effectively predict both longer EFS (p = 0.046) and OS (p = 0.015). Our study suggested that FSCN1 and FSCN2 can be used as favorable biomarkers for predicting clinical outcomes in MM.

Downregulation of FHOD1 Inhibits Metastatic Potential in A549 Cells

Purpose

Metastasis remains a serious clinical problem in which epithelial-to-mesenchymal transition is strictly involved. The change of cell phenotype is closely related to the dynamics of the cytoskeleton. Regarding the great interest in microfilaments, the manipulation of ABPs (actin-binding proteins) appears to be an interesting treatment strategy.

Material

The research material was the highly aggressive A549 cells with FHOD1 (F FH1/FH2 domain-containing protein 1) downregulation. The metastatic potential of the cells and the sensitivity to treatment with alkaloids (piperlongumine, sanguinarine) were analyzed.

Results

In comparison to A549 cells with naïve expression of FHOD1, those after manipulation were characterized by a reduced migratory potential. The obtained results were associated with microfilaments and vimentin reorganization induced by the manipulation of FHOD1 together with alkaloids treatment. The result was also an increase in the percentage of late apoptotic cells.

Conclusion

Downregulation of FHOD1 induced reorganization of microfilament network followed by the reduction in the metastatic potential of the A549 cells, as well as their sensitization to selected compounds. The presented results and the analysis of clinical data indicate the possibility of transferring research from the basic level to in vivo models in the context of manipulation of ABPs as a new therapeutic target in oncology.

Arabidopsis calcium-dependent protein kinase 3 regulates actin cytoskeleton organization and immunity

Pattern-triggered immunity and effector-triggered immunity are two primary forms of innate immunity in land plants. The molecular components and connecting nodes of pattern-triggered immunity and effector-triggered immunity are not fully understood. Here, we report that the Arabidopsis calcium-dependent protein kinase CPK3 is a key regulator of both pattern-triggered immunity and effector-triggered immunity. In vitro and in vivo phosphorylation assays, coupled with genetic and cell biology-based analyses, show that actin-depolymerization factor 4 (ADF4) is a physiological substrate of CPK3, and that phosphorylation of ADF4 by CPK3 governs actin cytoskeletal organization associated with pattern-triggered immunity. CPK3 regulates stomatal closure induced by flg22 and is required for resistance to Pst DC3000. Our data further demonstrates that CPK3 is required for resistance to Pst DC3000 carrying the effector AvrPphB. These results suggest that CPK3 is a missing link between cytoskeleton organization, pattern-triggered immunity and effector-triggered immunity.

Remodelling of the actin cytoskeleton occurs during plant immune responses to pathogens. Here Lu et al. show that this process requires the calcium-dependent kinase CPK3 which phosphorylates actin depolymerizing factor 4 and is required for both PAMP and effector-triggered immunity in Arabidopsis.

Emerging role of the Hippo pathway in autophagy

Autophagy is a dynamic circulatory system that occurs in all eukaryotic cells. Cytoplasmic material is transported to lysosomes for degradation and recovery through autophagy. This provides energy and macromolecular precursors for cell renewal and homeostasis. The Hippo-YAP pathway has significant biological properties in controlling organ size, tissue homeostasis, and regeneration. Recently, the Hippo-YAP axis has been extensively referred to as the pathophysiological processes regulating autophagy. Understanding the cellular and molecular basis of these processes is crucial for identifying disease pathogenesis and novel therapeutic targets. Here we review recent findings from Drosophila models to organisms. We particularly emphasize the regulation between Hippo core components and autophagy, which is involved in normal cellular regulation and the pathogenesis of human diseases, and its application to disease treatment.

Identification of Differentially Methylated Regions Associated with a Knockout of SUV39H1 in Prostate Cancer Cells

Epigenetic alterations, such as histone methylations, affect the pathogenesis of tumors including prostate cancer (PCa). Previously, we reported that metformin reduced SUV39H1, a histone methyltransferase of H3 Lys9, to inhibit the migration of PCa cells. Since histone methylation is functionally linked to DNA methylation, we speculate that the knockout of the SUV39H1 gene will affect the genomic DNA methylation profile to regulate PCa cell migration and invasion. The genome-wide DNA methylation level is lower in SUV39H1 knockout (KO) cells than wild-type (WT) ones. However, the methylation levels in functional regions of CpG Islands (CGI), 5' untranslated region (UTR5), and exon regions are higher in KO cells than WT cells. Analysis of differentially methylated regions (DMRs) identified 1241 DMR genes that have differential methylation on CG sites when comparing the KO and WT samples. Gene ontology enrichment and Kyoto Encyclopedia of Genes and Genomes Pathways analysis showed that knockout of SUV39H1 affects gene sets and pathways that are heavily involved in cell shapes, cell recognition, adhesion, motility, and migration. Our study suggests that SUV39H1 plays an important role in PCa migration via the epigenetic regulation of methylation on CG sites, and is a novel and legitimate target to inhibit PCa cell migration.

Differential expression of Scinderin and Gelsolin in gastric cancer and comparison with clinical and morphological characteristics

Gastric cancer is the first cause of cancer-related death in males and the second in female patients in Iran. Advanced cancer is usually associated with distant metastasis, which is uncontrollable. This study was conducted to compare the expression of Scinderin and Gelsolin genes between gastric cancer and adjacent normal tissue samples in Iranian patients in order to better understand the role of these genes in this disease and to assess them as potential gastric cancer diagnostic or prognostic biomarkers. This case-control study was conducted in 41 Iranian patients suffering from stage I to IV of Gastric Cancer diagnosed by pathologic and endoscopic tests. In this study, significant down-regulation of Gelsolin (p=0.001) and over-expression of Scinderin (p=0.001) were observed in tumor tissues compared to the adjacent normal tissues. The results of the present study showed decreased Gelsolin expression in patients above 40 years, while the relationship between Gelsolin expression and age was not significant; also, a significant increase was observed in Scinderin expression in patients above 40 years. Furthermore, Lymph node metastasis was observed in 59.52 % of the cases. The results showed that reduced Gelsolin and increased Scinderin expression were related to lymph node metastasis. Based on results, a significant association was observed between tumor size and Scinderin expression level. Furthermore, Gelsolin and Scinderin expressions were assessed in different grades and stages to determine the association of this gene with cancer progression. The result indicates significant alteration in Scinderin expression level of I and IV, II and IV, and III and IV stages. Although no significant association was observed between Scinderin expression level and GC grade, the mean Gelsolin expression showed a significant difference between grade II and III as well as grade I and IV. Based on our results, these genes would be potential biomarkers.

Fascin regulates protrusions and delamination to mediate invasive, collective cell migration in vivo

BACKGROUND

The actin bundling protein Fascin is essential for developmental cell migrations and promotes cancer metastasis. In addition to bundling actin, Fascin has several actin-independent roles; how these other functions contribute to cell migration remains unclear. Border cell migration during Drosophila oogenesis provides an excellent model to study Fascin's various roles during invasive, collective cell migration.

RESULTS

On-time border cell migration during Stage 9 requires Fascin (Drosophila Singed). Fascin functions not only within the migrating border cells, but also within the nurse cells, the substrate for this migration. Fascin genetically interacts with the actin elongation factor Enabled to promote on-time Stage 9 migration and overexpression of Enabled suppresses the defects seen with loss of Fascin. Loss of Fascin results in increased, shorter and mislocalized protrusions during migration. Additionally, loss of Fascin inhibits border cell delamination and increases E-Cadherin (Drosophila Shotgun) adhesions on both the border cells and nurse cells.

CONCLUSIONS

Overall, Fascin promotes on-time border cell migration during Stage 9 and contributes to multiple aspects of this invasive, collective cell migration, including both protrusion dynamics and delamination. These findings have implications beyond Drosophila, as border cell migration has emerged as a model to study mechanisms mediating cancer metastasis.

MiR-409-5p as a Regulator of Neurite Growth Is Down Regulated in APP/PS1 Murine Model of Alzheimer's Disease

Alzheimer’s disease (AD) is a heterogeneous neurodegenerative disease. Recent studies suggest that miRNA expression changes are associated with the development of AD. Our previous study showed that the expression level of miR-409-5p was stably downregulated in the early stage of APP/PS1 double transgenic mice model of AD. We now report that miR-409-5p impairs neurite outgrowth, decreases neuronal viability, and accelerates the progression of Aβ_1–42-induced pathologies. In this study, we found that Aβ_1–42 peptide significantly decreased the expression of miR-409-5p, which was consistent with the expression profile of miR-409-5p in the APP/PS1 mice cortexes. Plek was confirmed to be a potential regulatory target of miR-409-5p by luciferase assay and Western blotting. Overexpression of miR-409-5p has an obvious neurotoxicity in neuronal cell viability and differentiation, whereas Plek overexpression could partially rescue neurite outgrowth from this toxicity. Some cytoskeleton regulatory proteins have been found to be related to AD pathogenesis. Our data show some clues that cytoskeletal reorganization may play roles in AD pathology. The early downregulation of miR-409-5p in AD progression might be a self-protective reaction to alleviate the synaptic damage induced by Aβ, which may be used as a potential early biomarker of AD.

Pimozide suppresses cancer cell migration and tumor metastasis through binding to ARPC2, a subunit of the Arp2/3 complex

ARPC2 is a subunit of the Arp2/3 complex, which is essential for lamellipodia, invadopodia and filopodia, and ARPC2 has been identified as a migrastatic target molecule. To identify ARPC2 inhibitors, we generated an ARPC2 knockout DLD-1 human colon cancer cell line using the clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) system and explored gene signature-based strategies, such as a connectivity map (CMap) using the gene expression profiling data of ARPC2 knockout and knockdown cells. From the CMap-based drug discovery strategy, we identified pimozide (a clinically used antipsychotic drug) as a migrastatic drug and ARPC2 inhibitor. Pimozide inhibited the migration and invasion of various cancer cells. Through drug affinity responsive target stability (DARTS) analysis and cellular thermal shift assay (CETSA), it was confirmed that pimozide directly binds to ARPC2. Pimozide increased the lag phase of Arp2/3 complex-dependent actin polymerization and inhibited the vinculin-mediated recruitment of ARPC2 to focal adhesions in cancer cells. To validate the likely binding of pimozide to ARPC2, mutant cells, including ARPC2^F225A , ARPC2^F247A and ARPC2^Y250F cells, were prepared using ARPC2 knockout cells prepared by gene-editing technology. Pimozide strongly inhibited the migration of mutant cells because the mutated ARPC2 likely has a larger binding pocket than the wild-type ARPC2. Therefore, pimozide is a potential ARPC2 inhibitor, and ARPC2 is a new molecular target. Taken together, the results of the present study provide new insights into the molecular mechanism and target that are responsible for the antitumor and antimetastatic activity of pimozide.

Pharmaco-Genetic Screen To Uncover Actin Regulators Targeted by Prostaglandins During Drosophila Oogenesis

Prostaglandins (PGs) are lipid signaling molecules with numerous physiologic functions, including pain/inflammation, fertility, and cancer. PGs are produced downstream of cyclooxygenase (COX) enzymes, the targets of non-steroidal anti-inflammatory drugs (NSAIDs). In numerous systems, PGs regulate actin cytoskeletal remodeling, however, their mechanisms of action remain largely unknown. To address this deficiency, we undertook a pharmaco-genetic interaction screen during late-stage Drosophila oogenesis. Drosophila oogenesis is as an established model for studying both actin dynamics and PGs. Indeed, during Stage 10B, cage-like arrays of actin bundles surround each nurse cell nucleus, and during Stage 11, the cortical actin contracts, squeezing the cytoplasmic contents into the oocyte. Both of these cytoskeletal properties are required for follicle development and fertility, and are regulated by PGs. Here we describe a pharmaco-genetic interaction screen that takes advantage of the fact that Stage 10B follicles will mature in culture and COX inhibitors, such as aspirin, block this in vitro follicle maturation. In the screen, aspirin was used at a concentration that blocks 50% of the wild-type follicles from maturing in culture. By combining this aspirin treatment with heterozygosity for mutations in actin regulators, we quantitatively identified enhancers and suppressors of COX inhibition. Here we present the screen results and initial follow-up studies on three strong enhancers – Enabled, Capping protein, and non-muscle Myosin II Regulatory Light Chain. Overall, these studies provide new insight into how PGs regulate both actin bundle formation and cellular contraction, properties that are not only essential for development, but are misregulated in disease.

Mechanical Roles of F-Actin in the Differentiation of Stem Cells: A Review

In the development and differentiation of stem cells, mechanical forces associated with filamentous actin (F-actin) play a crucial role. The present review aims to reveal the relationship among the chemical components, microscopic structures, mechanical properties, and biological functions of F-actin. Particular attention is given to the functions of the cytoplasmic and nuclear microfilament cytoskeleton and their regulation mechanisms in the differentiation of stem cells. The distributions of different types of actin monomers in mammal cells and the functions of actin-binding proteins are summarized. We discuss how the fate of stem cells is regulated by intra/extracellular mechanical and chemical cues associated with microfilament-related proteins, intercellular adhesion molecules, etc. In addition, we also address the differentiation-induced variation in the stiffness of stem cells and the correlation between the fate and geometric shape change of stem cells. This review not only deepens our understanding of the biophysical mechanisms underlying the fates of stem cells under different culture conditions but also provides inspirations for the tissue engineering of stem cells.

Benproperine, an ARPC2 inhibitor, suppresses cancer cell migration and tumor metastasis

Metastasis is the leading cause of cancer mortality and cancer cell migration is an essential stage of metastasis. We identified benproperine (Benp, a clinically used antitussive drug) as an inhibitor of cancer cell migration and an anti-metastatic agent. Benp selectively inhibited cancer cell migration and invasion, which also suppressed metastasis of cancer cells in animal models. Actin-related protein 2/3 complex subunit 2 (ARPC2) was identified as a molecular target of Benp by affinity column chromatography with Benp-tagged Sepharose beads. Benp bound directly to ARPC2 in cells, which was validated by pull-down assay using Benp-biotin and label-free biochemical methods such as the drug affinity responsive target stability (DARTS) and cellular thermal shift assay (CETSA). Benp inhibited Arp2/3 function, showing disruption of lamellipodial structure and inhibition of actin polymerization. Unlike Arp2/3 inhibitors, Benp selectively inhibited the migration of cancer cells but not normal cells. ARPC2-knockdown cancer cells showed defective cell migration and suppressed metastasis in an animal model. Therefore, ARPC2 is a potential target for anti-metastatic therapy, and Benp has the clinical potential to block metastasis. Furthermore, Benp is a useful agent for studying the functions of the Arp2/3 complex in cancer cell migration and metastasis.

The anti-psychotic drug pimozide is a novel chemotherapeutic for breast cancer

Pimozide, an antipsychotic drug of the diphenylbutylpiperidine class, has been shown to suppress cell growth of breast cancer cells in vitro. In this study we further explore the inhibitory effects of this molecule in cancer cells. We found that Pimozide inhibited cell proliferation in a dose- and time-dependent manner in MDA-MB-231 breast cancer cells and A549 lung cancer cells. Furthermore, we found that Pimozide also promoted apoptosis as demonstrated by cell cycle arrest and induction of double-strand DNA breaks but did not result in any effect in the non-transformed MCF10A breast cell line. In order to shed new lights into the molecular pathways affected by Pimozide, we show that Pimozide downregulated RAN GTPase and AKT at both protein and mRNA levels and inhibited the AKT signaling pathway in MDA-MB-231 breast cancer cells. Pimozide also inhibited the epithelial mesenchymal transition and cell migration and downregulated the expression of MMPs. Administration of Pimozide showed a potent in vivo antitumor activity in MDA-MB-231 xenograft animal model and reduced the number of lung metastases by blocking vascular endothelial growth factor receptor 2. Furthermore, Pimozide inhibited myofibroblast formation as evaluated by the reduction in α-smooth muscle actin containing cells. Thus, Pimozide might inhibit tumor development by suppressing angiogenesis and by paracrine stimulation provided by host reactive stromal cells. These results demonstrate a novel in vitro and in vivo antitumor activity of Pimozide against breast and lung cancer cells and provide the proof of concept for a putative Pimozide as a novel approach for cancer therapy.

ARP3 promotes tumor metastasis and predicts a poor prognosis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death worldwide. Therefore, the study of the precise molecular mechanism underlying hepatocarcinogenesis has profound significance. In this study, we found that the expression of ARP3 was significantly up-regulated in HCC tissues and cell lines. Studies in liver cancer specimens showed that the expression of ARP3 is closely related to the pathological grade, distant metastasis and vascular invasion of HCC. According to the results of multivariate analysis, ARP3 is an independent prognostic factor for HCC patients. In vitro, knockdown of ARP3 expression significantly inhibited the invasion and migration of HCC cells and altered the expression of EMT markers. Based on the above conclusions, we conclude that ARP3 may be a potential prognostic indicator and therapeutic target for HCC patients.

Apelin Effects Migration and Invasion Abilities of Colon Cancer Cells

Colon cancer is one of the most common cancer types. Its positive correlation with general obesity has led to increasing amounts of research focusing on the role of adipokines in colon cancer development. Apelin is a peptide released by adipose tissue that could affect many cellular processes connected with carcinogenesis. In this study, we examined the role of apelin in the motility regulation of colon cancer cells. We showed that the effect of four different apelin peptides increased the ability of cancer cells to migrate and invade examined cells trough influencing migratory protrusions formation and actin cytoskeleton rearrangement. Additionally, using confocal microscopy, we noticed that apelin stimulated the proteolytic activity of cancer cells, especially increasing the level of membrane-type 1 matrix metalloprotease. Taken together, apelin increased the movement of colon cancer cells through several possible mechanisms. Moreover, better understanding the process through which apelin regulates cancer development is still necessary to the creation of novel anti-cancer therapy.

Identification of clinical tumor stages related mRNAs and miRNAs in cervical squamous cell carcinoma

OBJECTIVES

The aim of this study is to identify the clinical tumor stage related mRNAs and miRNAs, shedding light on the potential molecular mechanisms of cervical squamous cell carcinoma (CSCC).

METHODS

Firstly, the mRNA and miRNA next-generation sequencing data were downloaded. Secondly, clinical tumor stage correlation analysis of mRNAs and miRNA was performed, followed by the functional enrichment analysis of all clinical tumor stage related mRNAs. Thirdly, differentially expression analysis of mRNAs and miRNA between different clinical tumor stages was performed, followed by target gene prediction of these differentially expressed miRNAs.

RESULTS

3 mRNAs (PER1, PRKAB1 and PMM2) and 5 miRNAs (hsa-mir-486, hsa-mir-451, hsa-mir-424, hsa-mir-144 and hsa-mir-450a-2) were overlapped from stage 1, stage 2, stage 3 and stage 4.

CONCLUSIONS

Alterations of differentially expressed mRNAs and miRNAs may offer important insights into the molecular mechanisms in the pathology of CSCC.

S100P enhances the motility and invasion of human trophoblast cell lines

S100P has been shown to be a marker for carcinogenesis where its expression in solid tumours correlates with metastasis and a poor patient prognosis. This protein's role in any physiological process is, however, unknown. Here we first show that S100P is expressed both in trophoblasts in vivo as well as in some corresponding cell lines in culture. We demonstrate that S100P is predominantly expressed during the early stage of placental formation with its highest expression levels occurring during the first trimester of gestation, particularly in the invading columns and anchoring villi. Using gain or loss of function studies through overexpression or knockdown of S100P expression respectively, our work shows that S100P stimulates both cell motility and cellular invasion in different trophoblastic and first trimester EVT cell lines. Interestingly, cell invasion was seen to be more dramatically affected than cell migration. Our results suggest that S100P may be acting as an important regulator of trophoblast invasion during placentation. This finding sheds new light on a hitherto uncharacterized molecular mechanism which may, in turn, lead to the identification of novel targets that may explain why significant numbers of confirmed human pregnancies suffer complications through poor placental implantation.

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

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

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

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

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

MYLK promotes hepatocellular carcinoma progression through regulating cytoskeleton to enhance epithelial-mesenchymal transition

Myosin light chain kinase (MYLK) is found to catalyze the phosphorylation of myosin light chains (MLC) and regulate invasion and metastasis in some malignancies. However, there is little knowledge on the role of MYLK in hepatocellular carcinoma (HCC), and no studies have been conducted to investigate the mechanisms underlying MYLK-mediated promotion of HCC invasion and metastasis until now. In this study, we investigated the expression of MYLK in 50 pairs of human HCC and adjacent liver specimens. High MYLK expression was significantly correlated with aggressive clinicopathological features including tumor encapsulation, microvascular invasion and metastasis. In vitro assays showed that shRNA-induced MYLK knockdown significantly inhibited the wound-healing ability of HCC cells and the ability to migrate and invade through Matrigel. We next uncovered that MYLK knockdown resulted in a reduction in the number of F-actin stress fibers, disorganization of F-actin architectures and morphological alterations of HCC cells. Phosphorylated MLC, rather than total MLC, was found to be markedly reduced in response to downregulation of MYLK expression, and MYLK-regulated actin cytoskeleton through phosphorylating MLC in HCC cells. In addition, Western blotting assay revealed downregulation of the epithelial marker E-cadherin and upregulation of mesenchymal markers Vimentin, N-cadherin and Snail. Taken together, our findings indicate that MYLK promotes HCC progression by altering cytoskeleton to enhance epithelial-mesenchymal transition (EMT).

Forecast of actin-binding proteins as the oncotarget in osteosarcoma - a review of mechanism, diagnosis and therapy

Osteosarcoma (OS) is the most common bone malignant tumor with a high rate of lung metastasis and principally emerges in children and adolescents. Although neoadjuvant chemotherapy is widely used around the world, a high rate of chemoresistance occurs and frequently generates a poor prognosis. Therefore, finding a new appropriate prognostic marker for OS is a valuable research direction, which will give patients a better chance to receive proper therapy. Actin-binding proteins (ABPs) are a group of proteins that interact with actin cytoskeleton and play a crucial role in the regulation of the cell motility and morphology in eukaryotes. Meanwhile, ABPs also act as a bridge between the cytomembrane and nucleus, which transmit the outside-in and inside-out signals in cytoplasm. Furthermore, ABPs alter the dynamic structure of actin and regulate the invasion and metastasis of cancer. Hence, ABPs have a wide application in predicting the prognosis, and may be new targets, in tumor therapy. This review focuses on a series of ABPs and discusses their modulatory functions. It provides a new insight into the classification of ABPs’ functions in the process of invasion and metastasis in OS and illuminates the potential ability in predicting the prognosis of OS patients.

Myocardin-related transcription factor A (MRTF-A) activity-dependent cell adhesion is correlated to focal adhesion kinase (FAK) activity

The regulation of cell-substrate adhesion is tightly linked to the malignant phenotype of tumor cells and plays a role in their migration, invasion, and metastasis. Focal adhesions (FAs) are dynamic adhesion structures that anchor the cell to the extracellular matrix. Myocardin-related transcription factors (MRTFs), co-regulators of the serum response factor (SRF), regulate expression of a set of genes encoding actin cytoskeletal/FA-related proteins. Here we demonstrated that the forced expression of a constitutively active MRTF-A (CA-MRTF-A) in B16F10 melanoma cells induced the up-regulation of actin cytoskeletal and FA proteins, resulting in FA reorganization and the suppression of cell migration. Expression of CA-MRTF-A markedly increased phosphorylation of focal adhesion kinase (FAK) and paxillin, which are important components for FA dynamics. Notably, FAK activation was triggered by the clustering of up-regulated integrins. Our results revealed that the MRTF-SRF-dependent regulation of cell migration requires both the up-regulation of actin cytoskeletal/FA proteins and the integrin-mediated regulation of FA components via the FAK/Src pathway. We also demonstrated that activation of the MRTF-dependent transcription correlates FAK activation in various tumor cells. The elucidation of the correlation between MRTF and FAK activities would be an effective therapeutic target in focus of tumor cell migration.

Yap promotes hepatocellular carcinoma metastasis and mobilization via governing cofilin/F-actin/lamellipodium axis by regulation of JNK/Bnip3/SERCA/CaMKII pathways

Despite the increasingly important role of Hippo-Yap in hepatocellular carcinoma (HCC) development and progression, little insight is available at the time regarding the specifics interaction of Yap and cancer cells migration. Here, we identified the mechanism by which tumor-intrinsic Yap deletion resulted in HCC migratory inhibition. Yap was greatly upregulated in HCC and its expression promoted the cells migration. Functional studies found that knockdown of Yap induced JNK phosphorylation which closely bound to the Bnip3 promoter and contributed to Bnip3 expression. Higher Bnip3 employed excessive mitophagy leading to mitochondrial dysfunction and ATP shortage. The insufficient ATP inactivated SERCA and consequently triggered intracellular calcium overload. As the consequence of calcium oscillation, Ca/calmodulin-dependent protein kinases II (CaMKII) was signaled and subsequently inhibited cofilin activity via phosphorylated modification. The phosphorylated cofilin failed to manipulate F-actin polymerization and lamellipodium formation, resulting into the impairment of lamellipodium-based migration. Collectively, our results identified Hippo-Yap as the tumor promoter in hepatocellular carcinoma that mediated via activation of cofilin/F-actin/lamellipodium axis by limiting JNK-Bnip3-SERCA-CaMKII pathways, with potential application to HCC therapy involving cancer metastasis.

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Yap is upregulated in the hepatocellular carcinoma and promotes cancer cell migration.

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Loss of Yap impairs cell mobility via inhibiting cofilin/F-actin/lamellipodium by activation of JNK-Bnip3-SERCA-CaMKII.

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Loss of Yap enhances JNK phosphorylation which triggers Bnip3-required mitophagy.

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Excessive mitophagy induces mitochondrial energy disorder which blunts SERCA and causes calcium overload.

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The calcium overload drives CaMKII which inactivates cofilin, leading to F-actin degradation and lamellipodium collapse.

Covalent and non-covalent chemical engineering of actin for biotechnological applications

The cytoskeletal filaments are self-assembled protein polymers with 8-25nm diameters and up to several tens of micrometres length. They have a range of pivotal roles in eukaryotic cells, including transportation of intracellular cargoes (primarily microtubules with dynein and kinesin motors) and cell motility (primarily actin and myosin) where muscle contraction is one example. For two decades, the cytoskeletal filaments and their associated motor systems have been explored for nanotechnological applications including miniaturized sensor systems and lab-on-a-chip devices. Several developments have also revolved around possible exploitation of the filaments alone without their motor partners. Efforts to use the cytoskeletal filaments for applications often require chemical or genetic engineering of the filaments such as specific conjugation with fluorophores, antibodies, oligonucleotides or various macromolecular complexes e.g. nanoparticles. Similar conjugation methods are also instrumental for a range of fundamental biophysical studies. Here we review methods for non-covalent and covalent chemical modifications of actin filaments with focus on critical advantages and challenges of different methods as well as critical steps in the conjugation procedures. We also review potential uses of the engineered actin filaments in nanotechnological applications and in some key fundamental studies of actin and myosin function. Finally, we consider possible future lines of investigation that may be addressed by applying chemical conjugation of actin in new ways.

How myosin organization of the actin cytoskeleton contributes to the cancer phenotype

The human genome contains 39 genes that encode myosin heavy chains, classified on the basis of their sequence similarity into 12 classes. Most cells express at least 12 different genes, from at least 8 different classes, which are typically composed of several class 1 genes, at least one class 2 gene and classes 5, 6, 9, 10, 18 and 19. Although the different myosin isoforms all have specific and non-overlapping roles in the cell, in combination they all contribute to the organization of the actin cytoskeleton, and the shape and phenotype of the cell. Over (or under) expression of these different myosin isoforms can have strong effects on actin organization, cell shape and contribute to the cancer phenotype as discussed in this review.

A three-gene signature from protein-protein interaction network of LOXL2- and actin-related proteins for esophageal squamous cell carcinoma prognosis

Current staging is inadequate for predicting clinical outcome of esophageal squamous cell carcinoma (ESCC). Aberrant expression of LOXL2 and actin-related proteins plays important roles in ESCC. Here, we aimed to develop a novel molecular signature that exceeds the power of the current staging system in predicting ESCC prognosis. We found that LOXL2 colocalized with filamentous actin in ESCC cells, and gene set enrichment analysis (GSEA) showed that LOXL2 is related to the actin cytoskeleton. An ESCC-specific protein-protein interaction (PPI) network involving LOXL2 and actin-related proteins was generated based on genome-wide RNA-seq in 15 paired ESCC samples, and the prognostic significance of 14 core genes was analyzed. Using risk score calculation, a three-gene signature comprising LOXL2, CDH1, and FN1 was derived from transcriptome data of patients with ESCC. The high-risk three-gene signature strongly correlated with poor prognosis in a training cohort of 60 patients (P = 0.003). In mRNA and protein levels, the prognostic values of this signature were further validated in 243 patients from a testing cohort (P = 0.001) and two validation cohorts (P = 0.021, P = 0.007). Furthermore, Cox regression analysis revealed that the signature was an independent prognostic factor. Compared with using the signature or TNM stage alone, the combined model significantly enhanced the accuracy in evaluating ESCC prognosis. In conclusion, our data reveal that the tumor-promoting role of LOXL2 in ESCC is mediated by perturbing the architecture of actin cytoskeleton through its PPIs. We generated a novel three-gene signature (PPI interfaces) that robustly predicts poor clinical outcome in ESCC patients.

PHLDA1 (pleckstrin homology-like domain, family A, member 1) knockdown promotes migration and invasion of MCF10A breast epithelial cells

PHLDA1 (pleckstrin homology-like domain, family A, member 1) is a multifunctional protein that plays distinct roles in several biological processes including cell death and therefore its altered expression has been identified in different types of cancer. Progressively loss of PHLDA1 was found in primary and metastatic melanoma while its overexpression was reported in intestinal and pancreatic tumors. Previous work from our group showed that negative expression of PHLDA1 protein was a strong predictor of poor prognosis for breast cancer disease. However, the function of PHLDA1 in mammary epithelial cells and the tumorigenic process of the breast is unclear. To dissect PHLDA1 role in human breast epithelial cells, we generated a clone of MCF10A cells with stable knockdown of PHLDA1 and performed functional studies. To achieve reduced PHLDA1 expression we used shRNA plasmid transfection and then changes in cell morphology and biological behavior were assessed. We found that PHLDA1 downregulation induced marked morphological alterations in MCF10A cells, such as changes in cell-to-cell adhesion pattern and cytoskeleton reorganization. Regarding cell behavior, MCF10A cells with reduced expression of PHLDA1 showed higher proliferative rate and migration ability in comparison with control cells. We also found that MCF10A cells with PHLDA1 knockdown acquired invasive properties, as evaluated by transwell Matrigel invasion assay and showed enhanced colony-forming ability and irregular growth in low attachment condition. Altogether, our results indicate that PHLDA1 downregulation in MCF10A cells leads to morphological changes and a more aggressive behavior.

Actin stress fiber organization promotes cell stiffening and proliferation of pre-invasive breast cancer cells

Studies of the role of actin in tumour progression have highlighted its key contribution in cell softening associated with cell invasion. Here, using a human breast cell line with conditional Src induction, we demonstrate that cells undergo a stiffening state prior to acquiring malignant features. This state is characterized by the transient accumulation of stress fibres and upregulation of Ena/VASP-like (EVL). EVL, in turn, organizes stress fibres leading to transient cell stiffening, ERK-dependent cell proliferation, as well as enhancement of Src activation and progression towards a fully transformed state. Accordingly, EVL accumulates predominantly in premalignant breast lesions and is required for Src-induced epithelial overgrowth in Drosophila. While cell softening allows for cancer cell invasion, our work reveals that stress fibre-mediated cell stiffening could drive tumour growth during premalignant stages. A careful consideration of the mechanical properties of tumour cells could therefore offer new avenues of exploration when designing cancer-targeting therapies.

When cells acquire a malignant phenotype they become less stiff and this helps migration and invasion favouring metastasis. Here the authors show that Src-driven cell transformation and transition to a less stiff state follows an event of membrane stiffening due to stress fibres accumulation.

Tropomyosin Structure, Function, and Interactions: A Dynamic Regulator

Tropomyosin is the archetypal-coiled coil, yet studies of its structure and function have proven it to be a dynamic regulator of actin filament function in muscle and non-muscle cells. Here we review aspects of its structure that deviate from canonical leucine zipper coiled coils that allow tropomyosin to bind to actin, regulate myosin, and interact directly and indirectly with actin-binding proteins. Four genes encode tropomyosins in vertebrates, with additional diversity that results from alternate promoters and alternatively spliced exons. At the same time that periodic motifs for binding actin and regulating myosin are conserved, isoform-specific domains allow for specific interaction with myosins and actin filament regulatory proteins, including troponin. Tropomyosin can be viewed as a universal regulator of the actin cytoskeleton that specifies actin filaments for cellular and intracellular functions.