Integrins synergise to induce expression of the MRTF-A-SRF target gene ISG15 for promoting cancer cell invasion

GEF-H1 drives breast cancer cells to tumor progression

Rho GTPases are involved in several biological processes, including cytoskeletal remodeling, gene transcription, cell proliferation and differentiation. Dysregulation of Rho GTPases activity can lead to enhanced tumor cell proliferation and metastasis. Rho guanine nucleotide exchange factor-H1 (GEFH1) is a RhoA activator that is associated with microtubules (MT) and its localization and activity are regulated, in part, by MT and fibronectin-binding integrins. Our findings showed that GEF-H1 expression is significantly higher in human breast cancer biopsies than in normal tissues. Moreover, patients with increased GEF-H1 expression had a lower survival rate and a higher incidence of metastasis. We generated a GEF-H1 knockout (KO) breast cancer cell line and observed a significant reduction in the number of focal adhesions, formation of stress fibers, and activation of downstream signaling pathways. Concordantly, cell proliferation, migration, adhesion, and invasion were reduced. Furthermore, when GEF-H1 knockout (KO) cells were orthotopically implanted into the mammary fat pads of BALB/c mice, a significant decrease was observed in both tumor formation and lung metastasis compared to control breast cancer cells. These results suggest that GEF-H1/RhoA activation mediates cytoskeletal remodeling and signaling pathways critical for breast cancer cell proliferation, migration, and invasion. In vivo assays and human biopsy studies further support GEF-H1 as a potential biomarker of breast tumor progression.

Multiplex imaging reveals novel patterns of MRTFA/B activation in the breast cancer microenvironment

BACKGROUND

Breast cancer progression and metastasis involve the action of multiple transcription factors in tumors and in the cells of the tumor microenvironment (TME) and understanding how these transcription factors are coordinated can guide novel therapeutic strategies. Myocardin-related transcription factors A and B (MRTFA/B also known as MKL1/2) are two related transcription factors that redundantly control cancer cell invasion and metastasis in mouse models of breast cancer, but their roles in human cancer are incompletely understood. Here, we investigated the expression and activation of these transcription factors to better assess their tumorigenic and metastatic impact on breast cancer and cells of the tumor microenvironment.

METHODS

We used a multiplexed immunofluorescence approach to label MRTFA, MRTFB, tumor cells by using pan Cytokeratin, endothelial cells by using CD31, and antigen presenting cells (APCs) by using HLA-DRA on two different breast cancer tissue microarrays (TMA): The breast cancer progression TMA provided by the Cooperative Human Tissue Network (CHTN_BrCaProg3) and the University of Illinois Breast Cancer Working Group (TMA BCWG UIC-001-TMA) that included primary tumor and lymph node metastases from patients residing in the West Side and South Side of Chicago. We also used bioinformatics analyses of the TCGA and METABRIC databases and the Broad Institute's single-cell RNA sequencing portal to investigate MRTFA/B expression patterns in the cells of the tumor microenvironment (TME).

RESULTS

We found that in human tumors, MRTFA/B are concurrently activated in cancer cells, but they show distinct patterns of expression across different histological subtypes and in the cells of the TME. Importantly, MRTFA expression was elevated in metastatic tumors of African American patients, who disproportionately die from breast cancer. Interestingly, in contrast to publicly available mRNA expression data, MRTFA was similarly expressed across estrogen receptor (ER) positive and negative breast tumors, while MRTFB expression was highest in ER+ breast tumors. Furthermore, MRTFA was specifically expressed in the perivascular antigen-presenting cells (APCs), which has been previously associated with immune suppression and breast cancer progression. We also found that MRTFA expression correlated with the expression of the immune checkpoint protein V-set immunoregulatory receptor (VSIR) in the TCGA data and found that MRTFA activity promotes VSIR expression in THP-1 monocytes and cultured HEK293 cells.

CONCLUSIONS

Our results provide unique insights into how MRTFA and MRTFB promote metastasis in human cancer, the differences of their expression patterns, and their immune suppressive function within the breast cancer TME. Our results will guide future studies on targeting MRTFA/B transcriptional activity and the resulting immune suppression in breast cancer.

Pharmacological blocking of microfibrillar-associated protein 4 reduces retinal neoangiogenesis and vascular leakage

Neovascular age-related macular degeneration and diabetic macular edema are leading causes of vision loss evoked by retinal neovascularization and vascular leakage. The glycoprotein microfibrillar-associated protein 4 (MFAP4) is an integrin αVβ3/5/6 ligand present in the extracellular matrix. Single-cell transcriptomics reveal MFAP4 expression in cell types in close proximity to vascular endothelial cells, including choroidal vascular mural cells, retinal astrocytes, and Müller cells. Binding of the anti-MFAP4 antibody, hAS0326, makes MFAP4 inaccessible for integrin receptor interaction, and thereby hAS0326 blocked endothelial cell motility in vitro. Intravitreal hAS0326 inhibited retinal vascular lesion area and neovessel volume in a laser-induced choroidal neovascularization mouse model, vascular permeability in streptozotocin-induced retinopathy, and vascular leakage area in a chronic non-human primate model of DL-2-aminoadipic acid-induced retinopathy. One dose of hAS0326 showed duration of efficacy of at least 12 weeks in the latter model. Moreover, hAS0326 treatment significantly enriched Gene Ontology terms involving reduction of integrin binding. Our data suggest that hAS0326 constitutes a promising treatment of neovascularization and vascular leakage in retinal diseases.

Mechanosignaling via Integrins: Pivotal Players in Liver Fibrosis Progression and Therapy

Liver fibrosis, a consequence of chronic liver injury, represents a major global health burden and is the leading cause of liver failure, morbidity, and mortality. The pathological hallmark of this condition is excessive extracellular matrix deposition, driven primarily by integrin-mediated mechanotransduction. Integrins, transmembrane heterodimeric proteins that serve as primary ECM receptors, orchestrate complex mechanosignaling networks that regulate the activation, differentiation, and proliferation of hepatic stellate cells and other ECM-secreting myofibroblasts. These mechanical signals create self-reinforcing feedback loops that perpetuate the fibrotic response. Recent advances have provided insight into the roles of specific integrin subtypes in liver fibrosis and revealed their regulation of key downstream effectors-including transforming growth factor beta, focal adhesion kinase, RhoA/Rho-associated, coiled-coil containing protein kinase, and the mechanosensitive Hippo pathway. Understanding these mechanotransduction networks has opened new therapeutic possibilities through pharmacological manipulation of integrin-dependent signaling.

HERC5/ISG15 Enhances Glioblastoma Stemness and Tumor Progression by mediating SERBP1protein stability

Glioblastoma (GBM) is the most common malignant brain tumor, and has a low survival rate and a poor prognosis. Intensive studies of pathogenic mechanisms are essential for exploring therapeutic targets for GBM. In this study, the roles played by interferon-stimulated gene 15 (ISG15), HECT, RCC1-containing protein 5 (HERC5), and SERPINE1 mRNA binding protein 1 (SERBP1) in regulating GBM cell stemness were investigated. The real-time quantitative polymerase chain reaction (qPCR), western blotting (WB), and immunohistochemistry (IHC) were used to determine the expression levels of HERC5, ISG15, and SERBP1. Cell stemness was analyzed using a cell sphere formation assay. Colony formation and cell counting kit-8 (CCK-8) assays were performed to assess cell proliferation, Transwell assays used to evaluate cell migration and invasion, and flow cytometry was used to assess cell apoptosis after treatment with temozolomide. SERBP1 stability was assessed by a CHX chase assay. A co-immunoprecipitation (Co-IP) assay verified the binding of ISG15 and HERC5 onto SERBP1. Our results showed that HERC5 and ISG15 were highly expressed in GBM. HERC5 and ISG15 promoted the cell stemness of GBM, and increased cell proliferation, sphere formation, migration, invasion, and chemoresistance. Moreover, HERC5 and ISG15 played a synergistic role in promoting the cell stemness of GBM. We also found that HERC5/ISG15 promoted the stability of SERBP1, which also promoted the cell stemness of GBM. The tumor-promoting role of HERC5 and ISG15 was also confirmed in a subcutaneous xenograft tumor model. Collectively, HERC5/ISG15 was found to regulate GBM stemness and tumor progression by mediating SERBP1 protein stability. Our present study suggests a promising therapeutic target for GBM.

Altered extracellular matrix-related pathways accelerate the transition from normal to prefibroid myometrium in Black women

BACKGROUND

Black women experience a disproportionate impact of uterine fibroids compared to White women, including earlier diagnosis, higher frequency, and more severe symptoms. The etiology underlying this racial disparity remains elusive.

OBJECTIVE

The aim of this study was to evaluate the molecular differences in normal myometrium (fibroid-free uteri) and at-risk myometrium (fibroid-containing uteri) tissues in Black and White women.

STUDY DESIGN

We conducted whole-genome RNA-seq on normal and at-risk myometrium tissues obtained from both self-identified Black and White women (not Hispanic or Latino) to determine global gene expression profiles and to conduct enriched pathway analyses (n=3 per group). We initially assessed the differences within the same type of tissue (normal or at-risk myometrium) between races. Subsequently, we analyzed the transcriptome of normal myometrium compared to at-risk myometrium in each race and determined the differences between them. We validated our findings through real-time PCR (sample size range=5-12), western blot (sample size range=5-6), and immunohistochemistry techniques (sample size range=9-16).

RESULTS

The transcriptomic analysis revealed distinct profiles between Black and White women in normal and at-risk myometrium tissues. Interestingly, genes and pathways related to extracellular matrix and mechanosensing were more enriched in normal myometrium from Black than White women. Transcription factor enrichment analysis detected greater activity of the serum response transcription factor positional motif in normal myometrium from Black compared to White women. Furthermore, we observed increased expression levels of myocardin-related transcription factor-serum response factor and the serum response factor in the same comparison. In addition, we noted increased expression of both mRNA and protein levels of vinculin, a target gene of the serum response factor, in normal myometrium tissues from Black women as compared to White women. Importantly, the transcriptomic profile of normal to at-risk myometrium conversion differs between Black and White women. Specifically, we observed that extracellular matrix-related pathways are involved in the transition from normal to at-risk myometrium and that these processes are exacerbated in Black women. We found increased levels of Tenascin C, type I collagen alpha 1 chain, fibronectin, and phospho-p38 MAPK (Thr180/Tyr182, active) protein levels in at-risk over normal myometrium tissues from Black women, whereas such differences were not observed in samples from White women.

CONCLUSION

These findings indicate that the racial disparities in uterine fibroids may be attributed to heightened production of extracellular matrix in the myometrium in Black women, even before the tumors appear. Future research is needed to understand early life determinants of the observed racial differences.

A Versatile Microfluidic Platform for Extravasation Studies Based on DNA Origami-Cell Interactions

The adhesion of circulating tumor cells (CTCs) to the endothelial lumen and their extravasation to surrounding tissues are crucial in the seeding of metastases and remain the most complex events of the metastatic cascade to study. Integrins expressed on CTCs are major regulators of the extravasation process. This knowledge is primarily derived from animal models and biomimetic systems based on artificial endothelial layers, but these methods have ethical or technical limitations. We present a versatile microfluidic device to study cancer cell extravasation that mimics the endothelial barrier by using a porous membrane functionalized with DNA origami nanostructures (DONs) that display nanoscale patterns of adhesion peptides to circulating cancer cells. The device simulates physiological flow conditions and allows direct visualization of cell transmigration through microchannel pores using 3D confocal imaging. Using this system, we studied integrin-specific adhesion in the absence of other adhesive events. Specifically, we show that the transmigration ability of the metastatic cancer cell line MDA-MB-231 is influenced by the type, distance, and density of adhesion peptides present on the DONs. Furthermore, studies with mixed ligand systems indicate that integrins binding to RGD (arginine-glycine-aspartic acid) and IDS (isoleucine-aspartic acid-serine) did not synergistically enhance the extravasation process of MDA-MB-231 cells.

Fibroblast senescence-associated extracellular matrix promotes heterogeneous lung niche

Senescent cell accumulation in the pulmonary niche is associated with heightened susceptibility to age-related disease, tissue alterations, and ultimately a decline in lung function. Our current knowledge of senescent cell-extracellular matrix (ECM) dynamics is limited, and our understanding of how senescent cells influence spatial ECM architecture changes over time is incomplete. Herein is the design of an in vitro model of senescence-associated extracellular matrix (SA-ECM) remodeling using a senescent lung fibroblast-derived matrix that captures the spatiotemporal dynamics of an evolving senescent ECM architecture. Multiphoton second-harmonic generation microscopy was utilized to examine the spatial and temporal dynamics of fibroblast SA-ECM remodeling, which revealed a biphasic process that established a disordered and heterogeneous architecture. Additionally, we observed that inhibition of transforming growth factor-β signaling during SA-ECM remodeling led to improved local collagen fiber organization. Finally, we examined patient samples diagnosed with pulmonary fibrosis to further tie our results of the in vitro model to clinical outcomes. Moreover, we observed that the senescence marker p16 is correlated with local collagen fiber disorder. By elucidating the temporal dynamics of SA-ECM remodeling, we provide further insight on the role of senescent cells and their contributions to pathological ECM remodeling.

Protein ISGylation: a posttranslational modification with implications for malignant neoplasms

Interferon (IFN)-stimulated gene 15 (ISG15) is a member of the ubiquitin-like (UBL) protein family that can modify specific proteins via a catalytic process called ISGylation. This posttranslational modification can modulate the stability of the ISGylated proteins and protein-protein interactions. Some proteins modified by ISG15 have been identified in malignant neoplasms, suggesting the functional relevance of ISGylation in cancer. This review discusses the ISGylated proteins reported in malignant neoplasms that suggest the potential of ISG15 as a biomarker and therapeutic target in cancer.

Lfc subcellular localization and activity is controlled by αv-class integrin

Fibronectin (FN)-binding integrins control a variety of cellular responses through Rho GTPases. The FN-binding integrins, αvβ3 and α5β1, are known to induce different effects on cell morphology and motility. Here, we report that FN-bound αvβ3 integrin, but not FN-bound α5β1 integrin, triggers the dissociation of the RhoA GEF Lfc (also known as GEF-H1 and ARHGEF2 in humans) from microtubules (MTs), leading to the activation of RhoA, formation of stress fibres and maturation of focal adhesions (FAs). Conversely, loss of Lfc expression decreases RhoA activity, stress fibre formation and FA size, suggesting that Lfc is the major GEF downstream of FN-bound αvβ3 that controls RhoA activity. Mechanistically, FN-engaged αvβ3 integrin activates a kinase cascade involving MARK2 and MARK3, which in turn leads to phosphorylation of several phospho-sites on Lfc. In particular, S151 was identified as the main site involved in the regulation of Lfc localization and activity. Our findings indicate that activation of Lfc and RhoA is orchestrated in FN-adherent cells in an integrin-specific manner.

Small Extracellular Vesicles from Hypoxic Triple-Negative Breast Cancer Cells Induce Oxygen-Dependent Cell Invasion

Hypoxia, a condition of low oxygenation frequently found in triple-negative breast tumors (TNBC), promotes extracellular vesicle (EV) secretion and favors cell invasion, a complex process in which cell morphology is altered, dynamic focal adhesion spots are created, and ECM is remodeled. Here, we investigated the invasive properties triggered by TNBC-derived hypoxic small EV (SEVh) in vitro in cells cultured under hypoxic (1% O₂) and normoxic (20% O₂) conditions, using phenotypical and proteomic approaches. SEVh characterization demonstrated increased protein abundance and diversity over normoxic SEV (SEVn), with enrichment in pro-invasive pathways. In normoxic cells, SEVh promotes invasive behavior through pro-migratory morphology, invadopodia development, ECM degradation, and matrix metalloprotease (MMP) secretion. The proteome profiling of 20% O₂-cultured cells exposed to SEVh determined enrichment in metabolic processes and cell cycles, modulating cell health to escape apoptotic pathways. In hypoxia, SEVh was responsible for proteolytic and catabolic pathway inducement, interfering with integrin availability and gelatinase expression. Overall, our results demonstrate the importance of hypoxic signaling via SEV in tumors for the early establishment of metastasis.

Towards targeting of shared mechanisms of cancer metastasis and therapy resistance

Resistance to therapeutic treatment and metastatic progression jointly determine a fatal outcome of cancer. Cancer metastasis and therapeutic resistance are traditionally studied as separate fields using non-overlapping strategies. However, emerging evidence, including from in vivo imaging and in vitro organotypic culture, now suggests that both programmes cooperate and reinforce each other in the invasion niche and persist upon metastatic evasion. As a consequence, cancer cell subpopulations exhibiting metastatic invasion undergo multistep reprogramming that - beyond migration signalling - supports repair programmes, anti-apoptosis processes, metabolic adaptation, stemness and survival. Shared metastasis and therapy resistance signalling are mediated by multiple mechanisms, such as engagement of integrins and other context receptors, cell-cell communication, stress responses and metabolic reprogramming, which cooperate with effects elicited by autocrine and paracrine chemokine and growth factor cues present in the activated tumour microenvironment. These signals empower metastatic cells to cope with therapeutic assault and survive. Identifying nodes shared in metastasis and therapy resistance signalling networks should offer new opportunities to improve anticancer therapy beyond current strategies, to eliminate both nodular lesions and cells in metastatic transit.

ISG15 and ISGylation in Human Diseases

Type I Interferons (IFNs) induce the expression of >500 genes, which are collectively called ISGs (IFN-stimulated genes). One of the earliest ISGs induced by IFNs is ISG15 (Interferon-Stimulated Gene 15). Free ISG15 protein synthesized from the ISG15 gene is post-translationally conjugated to cellular proteins and is also secreted by cells into the extracellular milieu. ISG15 comprises two ubiquitin-like domains (UBL1 and UBL2), each of which bears a striking similarity to ubiquitin, accounting for its earlier name ubiquitin cross-reactive protein (UCRP). Like ubiquitin, ISG15 harbors a characteristic β-grasp fold in both UBL domains. UBL2 domain has a conserved C-terminal Gly-Gly motif through which cellular proteins are appended via an enzymatic cascade similar to ubiquitylation called ISGylation. ISG15 protein is minimally expressed under physiological conditions. However, its IFN-dependent expression is aberrantly elevated or compromised in various human diseases, including multiple types of cancer, neurodegenerative disorders (Ataxia Telangiectasia and Amyotrophic Lateral Sclerosis), inflammatory diseases (Mendelian Susceptibility to Mycobacterial Disease (MSMD), bacteriopathy and viropathy), and in the lumbar spinal cords of veterans exposed to Traumatic Brain Injury (TBI). ISG15 and ISGylation have both inhibitory and/or stimulatory roles in the etiology and pathogenesis of human diseases. Thus, ISG15 is considered a “double-edged sword” for human diseases in which its expression is elevated. Because of the roles of ISG15 and ISGylation in cancer cell proliferation, migration, and metastasis, conferring anti-cancer drug sensitivity to tumor cells, and its elevated expression in cancer, neurodegenerative disorders, and veterans exposed to TBI, both ISG15 and ISGylation are now considered diagnostic/prognostic biomarkers and therapeutic targets for these ailments. In the current review, we shall cover the exciting journey of ISG15, spanning three decades from the bench to the bedside.

Effects of forces on chromatin

Chromatin is a unique structure of DNA and histone proteins in the cell nucleus and the site of dynamic regulation of gene expression. Soluble factors are known to affect the chromatin structure and function via activating or inhibiting specific transcription factors. Forces on chromatin come from exogenous stresses on the cell surface and/or endogenous stresses, which are regulated by substrate mechanics, geometry, and topology. Forces on chromatin involve direct (via adhesion molecules, cytoskeleton, and the linker of nucleoskeleton and cytoskeleton complexes) and indirect (via diffusion and/or translocation processes) signaling pathways to modulate levels of chromatin folding and deformation to regulate transcription, which is controlled by histone modifications and depends on magnitude, direction, rate/frequency, duration, and modes of stresses. The rapid force transmission pathway activates multiple genes simultaneously, and the force may act like a "supertranscription factor." The indirect mechanotransduction pathways and the rapid force transmission pathway together exert sustained impacts on the chromatin, the nucleus, and cell functions.

Molecular Mechanisms and Cellular Contribution from Lung Fibrosis to Lung Cancer Development

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fibrosing interstitial lung disease (ILD) of unknown aetiology, with a median survival of 2-4 years from the time of diagnosis. Although IPF has unknown aetiology by definition, there have been identified several risks factors increasing the probability of the onset and progression of the disease in IPF patients such as cigarette smoking and environmental risk factors associated with domestic and occupational exposure. Among them, cigarette smoking together with concomitant emphysema might predispose IPF patients to lung cancer (LC), mostly to non-small cell lung cancer (NSCLC), increasing the risk of lung cancer development. To this purpose, IPF and LC share several cellular and molecular processes driving the progression of both pathologies such as fibroblast transition proliferation and activation, endoplasmic reticulum stress, oxidative stress, and many genetic and epigenetic markers that predispose IPF patients to LC development. Nintedanib, a tyrosine-kinase inhibitor, was firstly developed as an anticancer drug and then recognized as an anti-fibrotic agent based on the common target molecular pathway. In this review our aim is to describe the updated studies on common cellular and molecular mechanisms between IPF and lung cancer, knowledge of which might help to find novel therapeutic targets for this disease combination.

Vascular smooth muscle stiffness and its role in aging

Vascular smooth muscle cells (VSMC) are now considered important contributors to the pathophysiological and biophysical mechanisms underlying arterial stiffening in aging. Here, we review mechanisms whereby VSMC stiffening alters vascular function and contributes to the changes in vascular stiffening observed in aging and cardiovascular disease. Vascular stiffening in arterial aging was historically associated with changes in the extracellular matrix; however, new evidence suggests that endothelial and vascular smooth muscle cell stiffness also contribute to overall blood vessel stiffness. Furthermore, VSMC play an integral role in regulating matrix deposition and vessel wall contractility via interaction between the actomyosin contractile unit and adhesion structures that anchor the cell within the extracellular matrix. Aged-induce phenotypic modulation of VSMC from a contractile to a synthetic phenotype is associated with decreased cellular contractility and increased cell stiffness. Aged VSMC also display reduced mechanosensitivity and adaptation to mechanical signals from their microenvironment due to impaired intracellular signaling. Finally, evidence for decreased contractility in arteries from aged animals demonstrate that changes at the cellular level result in decreased functional properties at the tissue level.

The mitochondrially-localized nucleoside diphosphate kinase D (NME4) is a novel metastasis suppressor

Background

Mitochondrial nucleoside diphosphate kinase (NDPK-D, NME4, NM23-H4) is a multifunctional enzyme mainly localized in the intermembrane space, bound to the inner membrane.

Results

We constructed loss-of-function mutants of NDPK-D, lacking either NDP kinase activity or membrane interaction and expressed mutants or wild-type protein in cancer cells. In a complementary approach, we performed depletion of NDPK-D by RNA interference. Both loss-of-function mutations and NDPK-D depletion promoted epithelial-mesenchymal transition and increased migratory and invasive potential. Immunocompromised mice developed more metastases when injected with cells expressing mutant NDPK-D as compared to wild-type. This metastatic reprogramming is a consequence of mitochondrial alterations, including fragmentation and loss of mitochondria, a metabolic switch from respiration to glycolysis, increased ROS generation, and further metabolic changes in mitochondria, all of which can trigger pro-metastatic protein expression and signaling cascades. In human cancer, NME4 expression is negatively associated with markers of epithelial-mesenchymal transition and tumor aggressiveness and a good prognosis factor for beneficial clinical outcome.

Conclusions

These data demonstrate NME4 as a novel metastasis suppressor gene, the first localizing to mitochondria, pointing to a role of mitochondria in metastatic dissemination.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01155-5.

Identification of Novel FNIN2 and FNIN3 Fibronectin-Derived Peptides That Promote Cell Adhesion, Proliferation and Differentiation in Primary Cells and Stem Cells

In recent years, a major rise in the demand for biotherapeutic drugs has centered on enhancing the quality and efficacy of cell culture and developing new cell culture techniques. Here, we report fibronectin (FN) derived, novel peptides fibronectin-based intergrin binding peptide (FNIN)2 (18-mer) and FNIN3 (20-mer) which promote cell adhesion proliferation, and the differentiation of primary cells and stem cells. FNIN2 and 3 were designed based on the in silico interaction studies between FN and its receptors (integrin α5β1, αvβ3, and αIIbβ3). Analysis of the proliferation of seventeen-cell types showed that the effects of FNINs depend on their concentration and the existence of expressed integrins. Significant rhodamine-labeled FNIN2 fluorescence on the membranes of HeLa, HepG2, A498, and Du145 cells confirmed physical binding. Double coating with FNIN2 or 3 after polymerized dopamine (pDa) or polymerized tannic acid (pTA) precoating increased HBEpIC cell proliferation by 30–40 percent, suggesting FNINs potently affect primary cells. Furthermore, the proliferation of C2C12 myoblasts and human mesenchymal stem cells (MSCs) treated with FNINs was significantly increased in 2D/3D culture. FNINs also promoted MSC differentiation into osteoblasts. The results of this study offer a new approach to the production of core materials (e.g., cell culture medium components, scaffolds) for cell culture.

Optogenetic Control of Myocardin-Related Transcription Factor A Subcellular Localization and Transcriptional Activity Steers Membrane Blebbing and Invasive Cancer Cell Motility

The myocardin-related transcription factor A (MRTF-A) controls the transcriptional activity of the serum response factor (SRF) in a tightly controlled actin-dependent manner. In turn, MRTF-A is crucial for many actin-dependent processes including adhesion, migration, and contractility and has emerged as a novel target for anti-tumor strategies. MRTF-A rapidly shuttles between cytoplasmic and nuclear compartment via dynamic actin interactions within its N-terminal RPEL domain. Here, optogenetics is used to spatiotemporally control MRTF-A nuclear localization by blue light using the light-oxygen-voltage-sensing domain 2-domain based system LEXY (light-inducible nuclear export system). It is found that light-regulated nuclear export of MRTF-A occurs within 10-20 min. Importantly, MRTF-A-LEXY shuttling is independent of perturbations of actin dynamics. Furthermore, light-regulation of MRTF-A-LEXY is reversible and repeatable for several cycles of illumination and its subcellular localization correlates with SRF transcriptional activity. As a consequence, optogenetic control of MRTF-A subcellular localization determines subsequent cytoskeletal dynamics such as non-apoptotic plasma membrane blebbing as well as invasive tumor-cell migration through 3D collagen matrix. This data demonstrates robust optogenetic regulation of MRTF as a powerful tool to control SRF-dependent transcription as well as cell motile behavior.

The prognostic significance of interferon-stimulated gene 15 (ISG15) in invasive breast cancer

BACKGROUND

Lymphovascular invasion (LVI) is a prognostic factor in early-stage invasive breast cancer (BC). Through bioinformatics, data analyses of multiple BC cohorts revealed the positive association between interferon-stimulated gene 15 (ISG15) LVI status. Thus, we explored the prognostic significance of ISG15 in BC.

METHODS

The prognostic significance of ISG15 mRNA was assessed in METABRIC (n = 1980), TCGA (n = 854) and Kaplan-Meier Plotter (n = 3951). ISG15 protein was evaluated using immunohistochemistry (n = 859) in early-stage invasive BC patients with long-term follow-up. The associations between ISG15 expression and clinicopathological features, expression of immune cell markers and patient outcome data were evaluated.

RESULTS

High mRNA and protein ISG15 expression were associated with LVI, higher histological grade, larger tumour size, hormonal receptor negativity, HER2 positivity, p53 and Ki67. High ISG15 protein expression was associated with HER2-enriched BC subtypes and immune markers (CD8, FOXP3 and CD68). High ISG15 mRNA and ISG15 expressions were associated with poor patient outcome. Cox proportional multivariate analysis revealed that the elevated ISG15 expression was an independent prognostic factor of shorter BC-specific survival.

CONCLUSION

This study provides evidence for the role of ISG15 in LVI development and BC prognosis. Further functional studies in BC are warranted to evaluate the therapeutic potential of ISG15.

F-actin Regulates Osteoblastic Differentiation of Mesenchymal Stem Cells on TiO2 Nanotubes Through MKL1 and YAP/TAZ

Titanium and titanium alloys are widely used in orthopedic implants. Modifying the nanotopography provides a new strategy to improve osseointegration of titanium substrates. Filamentous actin (F-actin) polymerization, as a mechanical loading structure, is generally considered to be involved in cell migration, endocytosis, cell division, and cell shape maintenance. Whether F-actin is involved and how it functions in nanotube-induced osteogenic differentiation of mesenchymal stem cells (MSCs) remain to be elucidated. In this study, we fabricated TiO₂ nanotubes on the surface of a titanium substrate by anodic oxidation and characterized their features by scanning electron microscopy (SEM), X-ray energy dispersive analysis (EDS), and atomic force microscopy (AFM). Alkaline phosphatase (ALP) staining, Western blotting, qRT-PCR, and immunofluorescence staining were performed to explore the osteogenic potential, the level of F-actin, and the expression of MKL1 and YAP/TAZ. Our results showed that the inner diameter and roughness of TiO₂ nanotubes increased with the increase of the anodic oxidation voltage from 30 to 70 V, while their height was 2 μm consistently. Further, the larger the tube diameter, the stronger the ability of TiO₂ nanotubes to promote osteogenic differentiation of MSCs. Inhibiting F-actin polymerization by Cyto D inhibited osteogenic differentiation of MSCs as well as the expression of proteins contained in focal adhesion complexes such as vinculin (VCL) and focal adhesion kinase (FAK). In contrast, after Jasp treatment, polymerization of F-actin enhanced the expression of RhoA and transcription factors YAP/TAZ. Based on these data, we concluded that TiO₂ nanotubes facilitated the osteogenic differentiation of MSCs, and this ability was enhanced with the increasing diameter of the nanotubes within a certain range (30-70 V). F-actin mediated this process through MKL1 and YAP/TAZ.

Inducible microRNA-200c decreases motility of breast cancer cells and reduces filamin A

Cancer progression and metastases are frequently related to changes of cell motility. Amongst others, the microRNA-200c (miR-200c) was shown to maintain the epithelial state of cells and to hamper migration. Here, we describe two miR-200c inducible breast cancer cell lines, derived from miR-200c knock-out MCF7 cells as well as from the miR-200c-negative MDA-MB-231 cells and report on the emerging phenotypic effects after miR-200s induction. The induction of miR-200c expression seems to effect a rapid reduction of cell motility, as determined by 1D microlane migration assays. Sustained expression of miR200c leads to a changed morphology and reveals a novel mechanism by which miR-200c interferes with cytoskeletal components. We find that filamin A expression is attenuated by miRNA-200c induced downregulation of the transcription factors c-Jun and MRTF/SRF. This potentially novel pathway that is independent of the prominent ZEB axis could lead to a broader understanding of the role that miR200c plays in cancer metastasis.

Cell Adhesion by Integrins

Integrins are heterodimeric cell surface receptors ensuring the mechanical connection between cells and the extracellular matrix. In addition to the anchorage of cells to the extracellular matrix, these receptors have critical functions in intracellular signaling, but are also taking center stage in many physiological and pathological conditions. In this review, we provide some historical, structural, and physiological notes so that the diverse functions of these receptors can be appreciated and put into the context of the emerging field of mechanobiology. We propose that the exciting journey of the exploration of these receptors will continue for at least another new generation of researchers.

An intronic deletion in megakaryoblastic leukemia 1 is associated with hyperproliferation of B cells in triplets with Hodgkin lymphoma

Megakaryoblastic leukemia 1 (MKL1) is a coactivator of serum response factor and together they regulate transcription of actin cytoskeleton genes. MKL1 is associated with hematologic malignancies and immunodeficiency, but its role in B cells is unexplored. Here we examined B cells from monozygotic triplets with an intronic deletion in MKL1, two of whom had been previously treated for Hodgkin lymphoma (HL). To investigate MKL1 and B-cell responses in the pathogenesis of HL, we generated Epstein-Barr virus-transformed lymphoblastoid cell lines from the triplets and two controls. While cells from the patients with treated HL had a phenotype close to that of the healthy controls, cells from the undiagnosed triplet had increased MKL1 mRNA, increased MKL1 protein, and elevated expression of MKL1-dependent genes. This profile was associated with elevated actin content, increased cell spreading, decreased expression of CD11a integrin molecules, and delayed aggregation. Moreover, cells from the undiagnosed triplet proliferated faster, displayed a higher proportion of cells with hyperploidy, and formed large tumors in vivo This phenotype was reversible by inhibiting MKL1 activity. Interestingly, cells from the triplet treated for HL in 1985 contained two subpopulations: one with high expression of CD11a that behaved like control cells and the other with low expression of CD11a that formed large tumors in vivo similar to cells from the undiagnosed triplet. This implies that pre-malignant cells had re-emerged a long time after treatment. Together, these data suggest that dysregulated MKL1 activity participates in B-cell transformation and the pathogenesis of HL.

Long non-coding RNA urothelial cancer associated 1 can regulate the migration and invasion of colorectal cancer cells (SW480) via myocardin-related transcription factor-A

Colorectal cancer (CRC) is the third leading cause of cancer-associated mortalities. Long non-coding RNAs (lncRNAs) have been identified as key regulators in the occurrence and development of CRC. The lncRNA urothelial cancer associated 1 (UCA1) has been demonstrated to promote the development of numerous different types of cancer. In the present study, a novel molecular mechanism of UCA1, regulating the migratory and invasive capabilities of SW480 CRC cells was identified. UCA1 promoted the migration and invasion of SW480 cells by suppressing phosphorylation of myocardin-related transcription factor-A (MRTF-A). Our findings indicated that UCA1 competes with extracellular signal-regulated kinases1/2 to inhibit the phosphorylation of MRTF-A. These novel discoveries may reveal additional functions of UCA1, which may support future clinical development of novel drug targets.

MRTF-A controls myofibroblastic differentiation of human multipotent stromal cells and their tumour-supporting function in xenograft models

Tumour growth and metastatic colonization is strongly influenced by the tumour stroma, including cancer-associated fibroblasts (CAF). Multipotent mesenchymal stromal cells (MSC) are a possible source of CAF following myofibroblastic differentiation, and we have previously shown that MSC support tumour growth. Triggered by tumour cell-derived factors like transforming growth factor β1 (TGF-β1), myofibroblastic MSC differentiation is associated with the increased expression of markers including alpha smooth muscle actin (α-SMA). Here we show that myocardin-related transcription factor A (MRTF-A) plays an important role in myofibroblastic differentiation of primary human MSC in vitro and their tumour-supporting function in vivo. Recombinant TGF-β1 or tumour cell conditioned medium (TCM) elevated α-SMA, calponin 1 and collagen 1 A1 (COL1A1) amount on mRNA and protein level in MSC. This correlated with increased MRTF-A activity during MSC differentiation. MRTF-A knockdown by siRNA or shRNA impaired TGF-β1 and TCM induction of α-SMA and calponin 1, but not of COL1A1. Mixed xenograft experiments using HCT8 colorectal carcinoma cells and primary MSC of different donors revealed a significant reduction in tumour weight and volume upon MRTF-A knockdown in MSC. Our study suggests that MRTF-A is involved in the functional differentiation of MSC towards a tumour-promoting CAF phenotype in vivo.

Establishment and Characterization of a New Triple Negative Breast Cancer Cell Line from an Iranian Breast Cancer Tissue

Breast cancer is the most common malignancy and the leading cause of cancer-related death among women worldwide. The underlying mechanisms for breast cancer development, especially in young women, are not completely understood. Although there are several experimental models to understand the biology of breast cancer such as immortalized cell lines, many of these cell lines have been in culture for decades and most of them have been derived from Caucasians or African-Americans. So, it is required to establish a new cell line derived from primary tumors and Asian women. In this study Pari-Institute for Cancer Research (Pari-ICR) was derived from the primary breast tumor of a 36-years old patient with invasive ductal carcinoma. We characterized the cell line by examining morphology, expression of different markers, and functional profile. Immunocytochemistry showed that this cell line does not express estrogen and progesterone receptors as well as human epidermal growth factor receptor 2 (HER2). Pari-ICR cell line expresses high levels of Vimentin, Ezrin, and S100 but does not express EpCAM, Cytokeratin19, Pan-cytokeratin, Nestin, and Desmin. Its doubling time of Pari-ICR was about 22h and was able to grow as colonies in soft agar. It displayed a higher ability of migration and invasion in comparison with MCF-7 cell line. This breast cancer cell line can serve as a model for understanding the molecular mechanisms of breast carcinogenesis. Moreover, it can be used as an appropriate resource to find novel biomarkers or assess new drugs.

A β2-Integrin/MRTF-A/SRF Pathway Regulates Dendritic Cell Gene Expression, Adhesion, and Traction Force Generation

β2-integrins are essential for immune system function because they mediate immune cell adhesion and signaling. Consequently, a loss of β₂-integrin expression or function causes the immunodeficiency disorders, Leukocyte Adhesion Deficiency (LAD) type I and III. LAD-III is caused by mutations in an important integrin regulator, kindlin-3, but exactly how kindlin-3 regulates leukocyte adhesion has remained incompletely understood. Here we demonstrate that mutation of the kindlin-3 binding site in the β2-integrin (TTT/AAA-β2-integrin knock-in mouse/KI) abolishes activation of the actin-regulated myocardin related transcription factor A/serum response factor (MRTF-A/SRF) signaling pathway in dendritic cells and MRTF-A/SRF-dependent gene expression. We show that Ras homolog gene family, member A (RhoA) activation and filamentous-actin (F-actin) polymerization is abolished in murine TTT/AAA-β2-integrin KI dendritic cells, which leads to a failure of MRTF-A to localize to the cell nucleus to coactivate genes together with SRF. In addition, we show that dendritic cell gene expression, adhesion and integrin-mediated traction forces on ligand coated surfaces is dependent on the MRTF-A/SRF signaling pathway. The participation of β2-integrin and kindlin-3-mediated cell adhesion in the regulation of the ubiquitous MRTF-A/SRF signaling pathway in immune cells may help explain the role of β2-integrin and kindlin-3 in integrin-mediated gene regulation and immune system function.

Interferon-stimulated gene 15 modulates cell migration by interacting with Rac1 and contributes to lymph node metastasis of oral squamous cell carcinoma cells

In an effort to understand the underlying mechanisms of lymph node metastasis in oral squamous cell carcinoma (OSCC), through in vivo selection, LN1-1 cells were previously established from OEC-M1 cells and showed enhanced lymphangiogenesis and lymphatic metastasis capabilities. In the current study, we use a stable isotope labeling with amino acids in cell culture (SILAC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based proteomic platform to compare LN1-1 to OEC-M1 cells. Interferon-stimulated gene 15 (ISG15) was found highly expressed in LN1-1 cells. Immunohistochemical analysis and meta-analysis of publicly available microarray datasets revealed that the ISG15 level was increased in human OSCC tissues and associated with poor disease outcome. Knockdown of ISG15 had minimal effects on tumor growth but did decrease tumor lymphangiogenesis and lymphatic metastasis of LN1-1 cells. Consistent with the in vivo assay, ISG15 knockdown did not impair cell growth but diminished cell migration, invasion, and transendothelial migration in vitro. ISG15-induced cell migration was independent of ISGylation and associated with membrane protrusion. Ectopic expression of ISG15 increased Rac1 activity and knockdown of Rac1 impaired ISG15-enhanced migration. Furthermore, Rac1 colocalized with ISG15 to a region of membrane protrusion and ISG15 coimmunoprecipitated with Rac1, especially with the Rac1-GDP form. Importantly, as shown by proximity ligation assays, ISG15 and Rac1 physically interacted with each other. Our results indicated that ISG15 affects cell migration by interacting with Rac1 and regulating Rac1 activity and contributes to lymphatic metastasis in OSCC.

Non-muscle myosin IIA is post-translationally modified by interferon-stimulated gene 15 in breast cancer cells

ISG15 (interferon-stimulated gene 15) exists as free ISG15 or conjugated ISG15 modifying its target proteins via ISGylation. Few proteins have been identified and studied as ISGylation targets, and their relevance is not completely clear. Here, we isolated ISG15 from MDA-MB-231 breast cancer cells using immunoprecipitation and identified non-muscle myosin IIA (NMIIA) using mass spectrometry as endogenously associated with ISG15. The identification of NMIIA as an ISG15-interacting protein was important, because levels of NMIIA mRNA were not deregulated in all breast cancers, and because our in silico analysis indicated that NMIIA was the target of different posttranslational modifications and had an interactome associated with cytoskeletal remodeling. Furthermore, our experimental assays of co-immunoprecipitation and immunofluorescence confirmed that ISG15 was covalently associated with NMIIA in the cytoplasm of breast cancer cells and that interferon γ (IFN-γ) increased this association without alterations in the NMIIA levels. Thus, NMIIA ISGylation is regulated by IFN-γ, and this modification may modulate its interactions with proteins that remodel the cytoskeleton, participating in the growth and progression of mammary tumors.

A regulation loop between Nrf1α and MRTF-A controls migration and invasion in MDA-MB-231 breast cancer cells

As a strong transactivator of promoters containing CarG boxes, myocardin‑related transcription factor A (MRTF‑A) is critical for the process of metastasis in tumor cells. Nuclear factor erythroid 2‑like 1 (Nrf1) is well known as an important regulator of oxidative stress, which exists in multiple splicing forms with many unknown functions. The present study demonstrated a novel regulation loop between Nrf1α (the longest splicing form of Nrf1) and MRTF‑A that regulated the migration and invasion of breast cancer MDA‑MB‑231 cells. The underlying mechanism of this regulation look was further investigated. In particular, Nrf1α inhibited migration and invasion of breast cancer cells through inhibiting the expression of MRTF‑A via miR‑219. The current results revealed that miR‑219 could bind to the MRTF‑A 3'‑UTR to directly regulate its expression. However, MRTF‑A could reverse activate the Nrf1α expression through binding to the CarG box in the Nrf1α promoter. It can be speculated that this regulation loop may be a homeostasis mechanism in cells against tumorigenesis.

SRF'ing and SAP'ing - the role of MRTF proteins in cell migration

Actin-based cell migration is a fundamental cellular activity that plays a crucial role in a wide range of physiological and pathological processes. An essential feature of the remodeling of actin cytoskeleton during cell motility is the de novo synthesis of factors involved in the regulation of the actin cytoskeleton and cell adhesion in response to growth-factor signaling, and this aspect of cell migration is critically regulated by serum-response factor (SRF)-mediated gene transcription. Myocardin-related transcription factors (MRTFs) are key coactivators of SRF that link actin dynamics to SRF-mediated gene transcription. In this Review, we provide a comprehensive overview of the role of MRTF in both normal and cancer cell migration by discussing its canonical SRF-dependent as well as its recently emerged SRF-independent functions, exerted through its SAP domain, in the context of cell migration. We conclude by highlighting outstanding questions for future research in this field.

Micropatterning as a tool to identify regulatory triggers and kinetics of actin-mediated endothelial mechanosensing

Developmental processes, such as angiogenesis, are associated with a constant remodeling of the actin cytoskeleton in response to different mechanical stimuli. The mechanosensitive transcription factors MRTF-A (MKL1) and YAP (also known as YAP1) are important mediators of this challenging adaptation process. However, it is as yet unknown whether both pathways respond in an identical or in a divergent manner to a given microenvironmental guidance cue. Here, we use a micropatterning approach to dissect single aspects of cellular behavior in a spatiotemporally controllable setting. Using the exemplary process of angiogenesis, we show that cell-cell contacts and adhesive surface area are shared regulatory parameters of MRTF and YAP on rigid 2D surfaces. By analyzing MRTF and YAP under laminar flow conditions and during cell migration on dumbbell-shaped microstructures, we demonstrate that they exhibit different translocation kinetics. In conclusion, our work promotes the application of micropatterning techniques as a cell biological tool to study mechanosensitive signaling in the context of angiogenesis.

Making Heads or Tails of It: Cell-Cell Adhesion in Cellular and Supracellular Polarity in Collective Migration

Collective cell migration is paramount to morphogenesis and contributes to the pathogenesis of cancer. To migrate directionally and reach their site of destination, migrating cells must distinguish a front and a rear. In addition to polarizing individually, cell-cell interactions in collectively migrating cells give rise to a higher order of polarity, which allows them to move as a supracellular unit. Rather than just conferring adhesion, emerging evidence indicates that cadherin-based adherens junctions intrinsically polarize the cluster and relay mechanical signals to establish both intracellular and supracellular polarity. In this review, we discuss the various functions of adherens junctions in polarity of migrating cohorts.

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.

MRTFs- master regulators of EMT

Recent evidence implicates the myocardin-related transcription factors (MRTFs) as key mediators of the phenotypic plasticity leading to the conversion of various cell types into myofibroblasts. This review highlights the function of MRTFs during development, fibrosis and cancer, and the role of MRTFs during epithelial-mesenchymal transitions (EMTs) underlying these processes. EMT is a sequentially orchestrated process where cells undergo a rearrangement of their cell contacts and activate a fibrogenic and myogenic expression program. MRTFs interact with and regulate the major signaling pathways and the expression of key markers and transcription factors involved in EMT. These functions indicate a central role for MRTFs in controlling the process of EMT. Developmental Dynamics 247:396-404, 2018. © 2017 Wiley Periodicals, Inc.

Coping with Loss: Cell Adaptation to Cytoskeleton Disruption

Unravelling the role of cytoskeleton regulators may be complicated by adaptations to experimental manipulations. In this issue of Developmental Cell, Cerikan et al. (2016) reveal how acute effects of DOCK6 RhoGEF depletion on RAC1 and CDC42 activation are reversed over time by compensatory mechanisms that re-establish cellular homeostasis.

Cell-Intrinsic Adaptation Arising from Chronic Ablation of a Key Rho GTPase Regulator

Genome-editing technologies allow systematic inactivation of human genes. Whether knockout phenotypes always reflect gene functions as determined by acute RNAi is an important question. Here we show how the acute knockdown of the Adams-Oliver syndrome (AOS) gene DOCK6, coding for a RAC1/CDC42 guanine nucleotide exchange factor, results in strikingly different phenotypes to those generated by genomic DOCK6 disruption. Cell-intrinsic adaptation compensates for loss of DOCK6 function. Prolonged DOCK6 loss impacts upon the MRTF-A/SRF transcription factor, reducing levels of the ubiquitin-like modifier ISG15. Reduced ISGylation of the IQGAP1 protein increases levels of active CDC42 and RAC1 to compensate for DOCK6 disruption. Similar downregulation of ISG15 in cells from DOCK6 AOS patients indicates that such adaptation can compensate for genetic defects during development. Thus, phenotypes of gene inactivation are critically dependent on the timescale, as acute knockdown reflects a transient state of adjustment to a new equilibrium that is attained following compensation.