TRIM27/MRTF-B-dependent integrin β1 expression defines leading cells in cancer cell collectives

TRIM27 elicits protective immunity against tuberculosis by activating TFEB-mediated autophagy flux

Infectious diseases, such as Mycobacterium tuberculosis (Mtb)-caused tuberculosis (TB), remain a global threat exacerbated by increasing drug resistance. Host-directed therapy (HDT) is a promising strategy for infection treatment through targeting host immunity. However, the limited understanding of the function and regulatory mechanism of host factors involved in immune defense against infections has impeded HDT development. Here, we identify the ubiquitin ligase (E3) TRIM27 (tripartite motif-containing 27) as a host protective factor against Mtb by enhancing host macroautophagy/autophagy flux in an E3 ligase activity-independent manner. Mechanistically, upon Mtb infection, nuclear-localized TRIM27 increases and functions as a transcription activator of TFEB (transcription factor EB). Specifically, TRIM27 binds to the TFEB promoter and the TFEB transcription factor CREB1 (cAMP responsive element binding protein 1), thus enhancing CREB1-TFEB promoter binding affinity and promoting CREB1 transcription activity toward TFEB, eventually inducing autophagy-related gene expression as well as autophagy flux activation to clear the pathogen. Furthermore, TFEB activator 1 can rescue TRIM27 deficiency-caused decreased autophagy-related gene transcription and attenuated autophagy flux, and accordingly suppressed the intracellular survival of Mtb in cell and mouse models. Taken together, our data reveal that TRIM27 is a host defense factor against Mtb, and the TRIM27-CREB1-TFEB axis is a potential HDT-based TB target that can enhance host autophagy flux.Abbreviations: ATG5: autophagy related 5; BMDMs: bone marrow-derived macrophages; CFU: colony-forming unit; ChIP-seq: chromatin immunoprecipitation followed by sequencing; CREB1: cAMP responsive element binding protein 1; CTSB: cathepsin B; E3: ubiquitin ligase; EMSA: electrophoretic mobility shift assay; HC: healthy control; HDT: host-directed therapy; LAMP: lysosomal associated membrane protein; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MCOLN1: mucolipin TPR cation channel 1; Mtb: Mycobacterium tuberculosis; NLS: nuclear localization signal; PBMCs: peripheral blood mononuclear cells; PRKA/PKA: protein kinase cAMP-activated; qRT-PCR: quantitative real-time PCR; RFP: RET finger protein; TB: tuberculosis; TBK1: TANK binding kinase 1; TFEB: transcription factor EB; TRIM: tripartite motif; TSS: transcription start site; ULK1: unc-51 like autophagy activating kinase 1.

M1 macrophages induce PD-L1hi cell-led collective invasion in HPV-positive head and neck squamous cell carcinoma via TNF-α/CDK4/UPS14

BACKGROUND

Although the roles of PD-L1 in promoting tumor escape from immunosurveillance have been extensively addressed, its non-immune effects on tumor cells remain unclear.

METHODS

The spatial heterogeneity of PD-L1 staining in human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) tissues was identified by immunohistochemistry. Three-dimensional (3D) specific cell-led invasion assay and 3D cancer spheroid model were used to investigate the roles of PD-L1hileader cells in collective invasion. The impact of M1 macrophages on specific PD-L1 expression in leader cells and its mechanisms were further studied. Finally, the effect of combination therapy of anti-PD-L1 and CDK4 inhibitor on HPV-positive tumors were evaluated on a mice model.

RESULTS

Here, we observed a distinctive marginal pattern of PD-L1 expression in HPV-positive HNSCC tissues. By mimicking this spatial pattern of PD-L1 expression in the 3D invasion assay, we found that PD-L1hi cells led the tumor collective invasion. M1 macrophages induced specific PD-L1 expression in leader cells, and depletion of macrophages in tumor-bearing mice abrogated PD-L1hileader cells and collective invasion. Mechanistically, TNF-α secreted by M1 macrophages markedly increased the abundance of PD-L1 via CDK4/ubiquitin-specific peptidase 14-mediated deubiquitination of PD-L1. We also found that suppression of CDK4 enhanced the efficacy of anti-PD-L1 therapy in an E6/E7 murine model.

CONCLUSIONS

Our study identified TNF-α/CDK4/ubiquitin-specific peptidase 14-mediated PD-L1 stability as a novel mechanism underlying M1 macrophage-induced PD-L1hileader cells and collective tumor invasion, and highlighted the potential of the combination therapy of anti-PD-L1 and CDK4 inhibitor for HPV-positive HNSCC.

Matrix stiffening facilitates the collective invasion of breast cancer through the periostin-integrin mechanotransduction pathway

Matrix rigidity is a critical contributor to tumor progression; however, whether and how matrix stiffness modulates the collective invasion of tumor cells remain unknown. Here we demonstrate that increased matrix stiffness activates YAP to promote the secretion of periostin (POSTN) in cancer-associated fibroblasts, which in turn augments the matrix rigidity of mammary glands and breast tumor tissues by facilitating collagen crosslinking. Moreover, decreased tissue stiffening resulted from the POSTN deficiency impairs peritoneal metastatic potential of orthotopic breast tumors. Increased matrix stiffness also promotes three-dimensional (3D) collective breast tumor cell invasion via multicellular cytoskeleton remodeling. POSTN triggers the integrin/FAK/ERK/Cdc42/Rac1 mechanotransduction pathway during 3D collective invasion of breast tumor. Clinically, high POSTN expression correlates with high collagen levels in breast tumors and cooperatively determines the metastatic recurrence potential in breast cancer patients. Collectively, these findings indicate that matrix rigidity promotes 3D collective invasion of breast tumor cells via the YAP-POSTN-integrin mechanotransduction signaling.

TRIM40 is a pathogenic driver of inflammatory bowel disease subverting intestinal barrier integrity

The cortical actin cytoskeleton plays a critical role in maintaining intestinal epithelial integrity, and the loss of this architecture leads to chronic inflammation, as seen in inflammatory bowel disease (IBD). However, the exact mechanisms underlying aberrant actin remodeling in pathological states remain largely unknown. Here, we show that a subset of patients with IBD exhibits substantially higher levels of tripartite motif-containing protein 40 (TRIM40), a gene that is hardly detectable in healthy individuals. TRIM40 is an E3 ligase that directly targets Rho-associated coiled-coil-containing protein kinase 1 (ROCK1), an essential kinase involved in promoting cell-cell junctions, markedly decreasing the phosphorylation of key signaling factors critical for cortical actin formation and stabilization. This causes failure of the epithelial barrier function, thereby promoting a long-lived inflammatory response. A mutant TRIM40 lacking the RING, B-box, or C-terminal domains has impaired ability to accelerate ROCK1 degradation-driven cortical actin disruption. Accordingly, Trim40-deficient male mice are highly resistant to dextran sulfate sodium (DSS)-induced colitis. Our findings highlight that aberrant upregulation of TRIM40, which is epigenetically silenced under healthy conditions, drives IBD by subverting cortical actin formation and exacerbating epithelial barrier dysfunction.

Possible disease-protective roles of fibroblasts in cancer and fibrosis and their therapeutic application

Cancer and fibrotic diseases are characterized by continuous inflammation, tissue wounds, and injuries. Cancer is a "wound that does not heal," and the uncontrolled proliferation of cancer cells disrupts normal tissue integrity and induces stromal fibroinflammatory reactions. Fibroblasts proliferate extensively in the stroma, playing a major role in the development of these diseases. There has been considerable evidence that fibroblasts contribute to fibrosis and tissue stiffening and promote disease progression via multiple mechanisms. However, recent emerging findings, mainly derived from single-cell transcriptomic analysis, indicated that fibroblasts are functionally heterogeneous, leading to the hypothesis that both disease-promoting and -restraining fibroblasts exist. We recently showed that a fibroblast population, defined by the expression of the glycosylphosphatidylinositol-anchored membrane protein Meflin may suppress but not promote fibrotic response and disease progression in cancer and fibrotic diseases. Although currently hypothetical, the primary function of Meflin-positive fibroblasts may be tissue repair after injury and cancer initiation occurred. This observation has led to the proposal of a potential therapy that converts the phenotype of fibroblasts from pro-tumor to anti-tumor. In this short review, we summarize our recent findings on the function of Meflin in the context of cancer and fibrotic diseases and discuss how we can utilize this knowledge on fibroblasts in translational medicine. We also discuss several aspects of the interpretation of survival analysis data, such as Kaplan-Meier analysis, to address the function of specific genes expressed in fibroblasts.

TRIM27 cooperates with STK38L to inhibit ULK1-mediated autophagy and promote tumorigenesis

Autophagy represents a fundamental mechanism for maintaining cell survival and tissue homeostasis in response to physiological and pathological stress. Autophagy initiation converges on the FIP200-ATG13-ULK1 complex wherein the serine/threonine kinase ULK1 plays a central role. Here, we reveal that the E3 ubiquitin ligase TRIM27 functions as a negative regulatory component of the FIP200-ATG13-ULK1 complex. TRIM27 directly polyubiquitinates ULK1 at K568 and K571 sites with K48-linked ubiquitin chains, with proteasomal turnover maintaining control over basal ULK1 levels. However, during starvation-induced autophagy, TRIM27 catalyzes non-degradative K6- and K11-linked ubiquitination of the serine/threonine kinase 38-like (STK38L) kinase. In turn, STK38L ubiquitination promotes its activation and phosphorylation of ULK1 at Ser495, rendering ULK1 in a permissive state for TRIM27-mediated hyper-ubiquitination of ULK1. This cooperative mechanism serves to restrain the amplitude and duration of autophagy. Further evidence from mouse models shows that basal autophagy levels are increased in Trim27 knockout mice and that Trim27 differentially regulates tumorigenesis and metastasis. Our study identifies a key role of STK38L-TRIM27-ULK1 signaling axis in negatively controlling autophagy with relevance established in human breast cancer.

The interferon-β/STAT1 axis drives the collective invasion of skin squamous cell carcinoma with sealed intercellular spaces

The process by which cancer cells invade as a cell cluster, known as collective invasion, is associated with metastasis and worse prognosis of cancer patients; therefore, inhibition of collective invasion is considered to improve cancer treatment. However, the cellular characteristics responsible for collective invasion remain largely unknown. Here, we successfully established subclones with various invasive potentials derived from human skin squamous carcinoma cells. The cell cluster of the highly invasive subclone had a hermetically sealed and narrow intercellular space. Interferon-β was localized to the sealed intercellular spaces, leading to collective invasion via the activation of signal transducer and activator of transcription 1 (STAT1). On the other hand, interferon-β was not localized to non-sealed and wide intercellular spaces of the cell cluster of low-invasive subclone with deficient STAT1 activity. In the mixed cell cluster of high- and low-invasive subclones, the high-invasive sub-clonal cells were located at the invasive front of the invasive protrusion, leading to collective invasion by the low-invasive sub-clonal cells. Tissue microarray analysis of human skin squamous cell carcinoma (SCC) also showed enrichment of STAT1 in the invasive front of SCCs. These findings indicate that the intercellular structure controls the potential for collective invasion via STAT1 regulation in SCC.

Inner Nuclear Membrane Protein, SUN1, is Required for Cytoskeletal Force Generation and Focal Adhesion Maturation

The linker of nucleoskeleton and cytoskeleton (LINC) complex is composed of the inner nuclear membrane-spanning SUN proteins and the outer nuclear membrane-spanning nesprin proteins. The LINC complex physically connects the nucleus and plasma membrane via the actin cytoskeleton to perform diverse functions including mechanotransduction from the extracellular environment to the nucleus. Mammalian somatic cells express two principal SUN proteins, namely SUN1 and SUN2. We have previously reported that SUN1, but not SUN2, is essential for directional cell migration; however, the underlying mechanism remains elusive. Because the balance between adhesive force and traction force is critical for cell migration, in the present study, we focused on focal adhesions (FAs) and the actin cytoskeleton. We observed that siRNA-mediated SUN1 depletion did not affect the recruitment of integrin β1, one of the ubiquitously expressed focal adhesion molecules, to the plasma membrane. Consistently, SUN1-depleted cells normally adhered to extracellular matrix proteins, including collagen, fibronectin, laminin, and vitronectin. In contrast, SUN1 depletion reduced the activation of integrin β1. Strikingly, the depletion of SUN1 interfered with the incorporation of vinculin into the focal adhesions, whereas no significant differences in the expression of vinculin were observed between wild-type and SUN1-depleted cells. In addition, SUN1 depletion suppressed the recruitment of zyxin to nascent focal adhesions. These data indicate that SUN1 is involved in the maturation of focal adhesions. Moreover, disruption of the SUN1-containing LINC complex abrogates the actin cytoskeleton and generation of intracellular traction force, despite the presence of SUN2. Thus, a physical link between the nucleus and cytoskeleton through SUN1 is required for the proper organization of actin, thereby suppressing the incorporation of vinculin and zyxin into focal adhesions and the activation of integrin β1, both of which are dependent on traction force. This study provides insights into a previously unappreciated signaling pathway from the nucleus to the cytoskeleton, which is in the opposite direction to the well-known mechanotransduction pathways from the extracellular matrix to the nucleus.

MicroRNA as an Important Target for Anticancer Drug Development

Cancer has become the second greatest cause of death worldwide. Although there are several different classes of anticancer drugs that are available in clinic, some tough issues like side-effects and low efficacy still need to dissolve. Therefore, there remains an urgent need to discover and develop more effective anticancer drugs. MicroRNAs (miRNAs) are a class of small endogenous non-coding RNAs that regulate gene expression by inhibiting mRNA translation or reducing the stability of mRNA. An abnormal miRNA expression profile was found to exist widely in cancer cell, which induces limitless replicative potential and evading apoptosis. MiRNAs function as oncogenes (oncomiRs) or tumor suppressors during tumor development and progression. It was shown that regulation of specific miRNA alterations using miRNA mimics or antagomirs can normalize the gene regulatory network and signaling pathways, and reverse the phenotypes in cancer cells. The miRNA hence provides an attractive target for anticancer drug development. In this review, we will summarize the latest publications on the role of miRNA in anticancer therapeutics and briefly describe the relationship between abnormal miRNAs and tumorigenesis. The potential of miRNA-based therapeutics for anticancer treatment has been critically discussed. And the current strategies in designing miRNA targeting therapeutics are described in detail. Finally, the current challenges and future perspectives of miRNA-based therapy are conferred.

Tactics of cancer invasion: solitary and collective invasion

Much attention has been paid on the mechanism of cancer invasion from the viewpoint of the behaviour of individual cancer cells. On the other hand, histopathological analyses of specimens from cancer patients and of cancer invasion model animals have revealed that cancer cells often exhibit collective invasion, characterized by sustained cell-to-cell adhesion and polarized invasion as cell clusters. Interestingly, it has recently become evident that during collective invasion of cancer cells, the cells localized at invasion front (leader cells) and the cells following them (follower cells) exhibit distinct cellular characteristics, and that there exist the cells expressing representative proteins related to both epithelial and mesenchymal properties simultaneously, designated as hybrid epithelial-to-mesenchymal transition (EMT)-induced cells, in cancer tissue. Furthermore, the findings that cells adopted in hybrid EMT state form clusters and show collective invasion in vitro emphasize an importance of hybrid EMT-induced cells in collective cancer invasion. In this article, we overview recent findings of the mechanism underlying collective invasion of cancer cells and discuss the possibility of controlling cancer invasion and metastasis by targeting this process.

TRIM27 acts as an oncogene and regulates cell proliferation and metastasis in non-small cell lung cancer through SIX3-β-catenin signaling

The Wnt/β-catenin pathway plays vital roles in diverse biological processes, including cell differentiation, proliferation, migration, and insulin sensitivity. A recent study reported that the DNA-binding transcriptional factor SIX3 is essential during embryonic development in vertebrates and capable of downregulating target genes of the Wnt/β-catenin pathway in lung cancer, indicating negative regulation of Wnt/β-catenin activation. However, regulation of the SIX3-Wnt/β-catenin pathway axis remains unknown. We measured the expression of TRIM27 and SIX3 as well as investigated whether there was a correlation between them in lung cancer tissue samples. Herein, we found that the E3 ubiquitin ligase, TRIM27, ubiquitinates, and degrades SIX3. TRIM27 induces non-small cell lung cancer (NSCLC) cell proliferation and metastasis, and the expression of β-catenin, S100P, TGFB3, and MMP-9 were significantly inhibited by SIX3. Furthermore, XAV939 is a selective β-catenin-mediated transcription inhibitor that inhibited TRIM27- and SIX3-mediated NSCLC cell proliferation, migration, and invasion. Clinically, lung tissue samples of cancer patients showed increased TRIM27 expression and decreased SIX3 expression. Taken together, these data demonstrate that TRIM27 acts as an oncogene regulating cell proliferation and metastasis in NSCLC through SIX3-β-catenin signaling.

TRIM28 and TRIM27 are required for expressions of PDGFRβ and contractile phenotypic genes by vascular smooth muscle cells

Vascular smooth muscle cells (VSMCs) in the normal arterial media continually express contractile phenotypic markers which are reduced dramatically in response to injury. Tripartite motif-containing proteins are a family of scaffold proteins shown to regulate gene silencing, cell growth, and differentiation. We here investigated the biological role of tripartite motif-containing 28 (TRIM28) and tripartite motif-containing 27 (TRIM27) in VSMCs. We observed that siRNA-mediated knockdown of TRIM28 and TRIM27 inhibited platelet-derived growth factor (PDGF)-induced migration in human VSMCs. Both TRIM28 and TRIM27 can regulate serum response element activity and were required for maintaining the contractile gene expression in human VSMCs. At the same time, TRIM28 and TRIM27 knockdown reduced the expression of PDGF receptor-β (PDGFRβ) and the phosphorylation of its downstream signaling components. Immunoprecipitation showed that TRIM28 formed complexes with TRIM27 through its N-terminal RING-B boxes-Coiled-Coil domain. Furthermore, TRIM28 and TRIM27 were shown to be upregulated and mediate the VSMC contractile marker gene and PDGFRβ expression in differentiating human bone marrow mesenchymal stem cells. In conclusion, we identified that TRIM28 and TRIM27 cooperatively maintain the endogenous expression of PDGFRβ and contractile phenotype of human VSMCs.

To lead or to herd: optimal strategies for 3D collective migration of cell clusters

Cells migrating in clusters play a significant role in a number of biological processes such as embryogenesis, wound healing, and tumor metastasis during cancer progression. A variety of environmental and biochemical factors can influence the collective migration of cells with differing degrees of cell autonomy and inter-cellular coupling strength. For example, weakly coupled cells can move collectively under the influence of contact guidance from neighboring cells or the environment. Alternatively strongly coupled cells might follow one or more leader cells to move as a single cohesive unit. Additionally, chemical and mechanical signaling between these cells may alter the degree of coupling and determine effective cluster sizes. Being able to understand this collective cell migration process is critical in the prediction and manipulation of outcomes of key biological processes. Here we focus on understanding how various environmental and cellular factors influence small clusters of cells migrating collectively within a 3D fibrous matrix. We combine existing knowledge of single-cell migration in 2D and 3D environments, prior experimental observations of cell-cell interactions and collective migration, and a newly developed stochastic model of cell migration in 3D matrices, to simulate the migration of cell clusters in different physiologically relevant environments. Our results show that based on the extracellular environment and the strength of cell-cell mechanical coupling, two distinct optimal approaches to driving collective cell migration emerge. The ability to effectively employ these two distinct migration strategies might be critical for cells to collectively migrate through the heterogeneous tissue environments within the body.

PEP06 polypeptide 30 is a novel cluster-dissociating agent inhibiting v integrin/FAK/Src signaling in oral squamous cell carcinoma cells

Collectively migrating tumor cells have been recently implicated in enhanced metastasis of epithelial malignancies. In oral squamous cell carcinoma (OSCC), αv integrin is a crucial mediator of multicellular clustering and collective movement in vitro; however, its contribution to metastatic spread remains to be addressed. According to the emerging therapeutic concept, dissociation of tumor clusters into single cells could significantly suppress metastasis-seeding ability of carcinomas. This study aimed to investigate the anti-OSCC potential of novel endostatin-derived polypeptide PEP06 as a cluster-dissociating therapeutic agent in vitro. Firstly, we found marked enrichment of αv integrin in collectively invading multicellular clusters in human OSCCs. Our study revealed that metastatic progression of OSCC was associated with augmented immunostaining of αv integrin in cancerous lesions. Following PEP06 treatment, cell clustering on fibronectin, migration, multicellular aggregation, anchorage-independent survival and colony formation of OSCC were significantly inhibited. Moreover, PEP06 suppressed αv integrin/FAK/Src signaling in OSCC cells. PEP06-induced loss of active Src and E-cadherin from cell–cell contacts contributed to diminished collective migration of OSCC in vitro. Overall, these results suggest that PEP06 polypeptide 30 inhibiting αv integrin/FAK/Src signaling and disrupting E-cadherin-based intercellular junctions possesses anti-metastatic potential in OSCC by acting as a cluster-dissociating therapeutic agent.

The intercellular expression of type-XVII collagen, laminin-332, and integrin-β1 promote contact following during the collective invasion of a cancer cell population

Cancer cells can invade as a population in various cancer tissues. This phenomenon is called collective invasion, which is associated with the metastatic potential and prognosis of cancer patients. The collectiveness of cancer cells is necessary for collective invasion. However, the mechanism underlying the generation of collectiveness by cancer cells is not well known. In this study, the phenomenon of contact following, where neighboring cells move in the same direction via intercellular adhesion, was investigated. An experimental system was created to observe the two-dimensional invasion using a collagen gel overlay to study contact following in collective invasion. The role of integrin-β1, one of the major extracellular matrix (ECM) receptors, in contact following was examined through the experimental system. Integrin-β1 was localized to the intercellular site in squamous carcinoma cells. Moreover, the intercellular adhesion and contact following were suppressed by treatment of an integrin-β1 inhibitory antibody. ECM proteins such as laminin-332 and type-XVII collagen were also localized to the intercellular site and critical for contact following. Collectively, it was demonstrated that the activity of integrin-β1 and expression of ECM proteins in the intercellular site promote contact following in the collective invasion of a cancer cell population.

Cathepsin B defines leader cells during the collective invasion of salivary adenoid cystic carcinoma

Cathepsin B (CTSB) has been reported to be involved in cancer metastasis by altering extracellular matrix (ECM) remodeling and facilitating invasion. However, the contribution of CTSB to collective cell invasion in salivary adenoid cystic carcinoma (SACC) and the underlying mechanisms remain unclear. The present study demonstrated that collective cell invasion is commonly observed in SACC without a complete epithelial-mesenchymal transition signature. CTSB was found to be overexpressed in the invasive front of SACC compared to the tumor center, and was associated with a poor prognosis of patients with SACC. Subsequently, a 3D spheroid invasion assay was established in order to recapitulate the collective cell invasion of SACC and the results revealed that CTSB was only expressed in leader cells. The knockdown of CTSB by siRNA inhibited the migration and invasion of SACC-83 cells and impaired the formation of leader cells. CTSB knockdown also disrupted cytoskeletal organization, altered cell morphology and inhibited ECM remodeling by downregulating matrix metalloproteinase-9, focal adhesion kinase and Rho/ROCK function. Therefore, the present study provides evidence that CTSB may define leader cells in SACC and is required for collective cell invasion as a potential key regulator of ECM remodeling.

The metastasis suppressor NME1 inhibits melanoma cell motility via direct transcriptional induction of the integrin beta-3 gene

Expression of the metastasis suppressor NME1 in melanoma is associated with reduced cellular motility, invasion, and metastasis, but mechanisms underlying these activities are not completely understood. Herein we report a novel mechanism through which NME1 drives formation of large, stable focal adhesions (FAs) in melanoma cells via induction of integrin β3 (ITGβ3), and in one cell line, concomitant suppression of integrin β1 (ITGβ1) transcripts. Forced expression of NME1 resulted in a strong activation of the promoter region (-301 to +13) of the ITGB3 gene. Chromatin immunoprecipitation (ChIP) analysis revealed the transcriptional induction was associated with direct recruitment of NME1 and an increase in the epigenetic activation mark, acetylation of histone 3 on lysine 27 (H3K27Ac) to a 1 kb stretch of 5'-flanking sequence of the ITGB3 gene. Unexpectedly, NME1 did not affect the amount either ITGβ1 or ITGβ3 proteins were internalized and recycled, processes commonly associated with regulating expression of integrins at the cell surface. The ability of NME1 to suppress motile and invasive phenotypes of melanoma cells was dependent on its induction of ITGβ3. Expression of ITGβ3 mRNA was associated with increased disease-free survival time in melanoma patients of the TCGA collection, consistent with its potential role as an effector of the metastasis suppressor function of NME1. Together, these data indicate metastasis suppressor activity of NME1 in melanoma is mediated by induction of ITGB3 gene transcription, with NME1-driven enrichment of ITGβ3 protein at the cell membrane resulting in attenuated cell motility through the stabilization of large focal adhesions.

Girdin/GIV regulates collective cancer cell migration by controlling cell adhesion and cytoskeletal organization

Pathological observations show that cancer cells frequently invade the surrounding stroma in collective groups rather than through single cell migration. Here, we studied the role of the actin-binding protein Girdin, a specific regulator of collective migration of neuroblasts in the brain, in collective cancer cell migration. We found that Girdin was essential for the collective migration of the skin cancer cell line A431 on collagen gels as well as their fibroblast-led collective invasion in an organotypic culture model. We provide evidence that Girdin binds to β-catenin that plays important roles in the Wnt signaling pathway and in E-cadherin-mediated cell-cell adhesion. Girdin-depleted cells displayed scattering and impaired E-cadherin-specific cell-cell adhesion. Importantly, Girdin depletion led to impaired cytoskeletal association of the β-catenin complex, which was accompanied by changes in the supracellular actin cytoskeletal organization of cancer cell cohorts on collagen gels. Although the underlying mechanism is unclear, this observation is consistent with the established role of the actin cytoskeletal system and cell-cell adhesion in the collective behavior of cells. Finally, we showed the correlation of the expression of Girdin with that of the components of the E-cadherin complex and the differentiation of human skin cancer. Collectively, our results suggest that Girdin is an important modulator of the collective behavior of cancer cells.

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.

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.

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.

Following MicroRNAs Through the Cancer Metastatic Cascade

Approximately a decade ago the first MicroRNAs (MiRNAs) participating in cancer metastasis were identified and metastmiRs were initially only a handful. Since those first reports, MiRNA research has explosively thrived, mainly due to their revolutionary mechanism of action and the hope of having at hand a novel tool to control cancer aggressiveness. This has ultimately led to delineate an almost impenetrable regulatory network: hundreds of MiRNAs transversally dominating every aspect of normal and cancer biology, each MiRNA having hundreds of targets and context-dependent activity. Providing a comprehensive description of MiRNA roles in cancer metastasis is a daunting task; nevertheless, we still believe that grasping the big picture of MiRNAs in cancer metastasis can give a different perspective on the potential insights and approaches that MiRNAs can offer to understand cancer complexity (e.g., as predictive and prognostic markers) and to tackle cancer metastasis (e.g., as therapeutic targets or tools). This chapter presents a schematic overview of the role of MiRNAs in governing cancer metastasis, describing step by step the cellular and molecular processes whereby cancer cells conquer distant organs and can grow as secondary tumors at different distant sites, and for each step, we will introduce how MiRNAs impinge on each one of them. We deeply apologize with our colleagues for any of their research work that, for clarity, for our effort to streamline and due to space limitations, we did not cite.

G196 epitope tag system: a novel monoclonal antibody, G196, recognizes the small, soluble peptide DLVPR with high affinity

The recognition specificity of monoclonal antibodies (mAbs) has made mAbs among the most frequently used tools in both basic science research and in clinical diagnosis and therapies. Precise determination of the epitope allows the development of epitope tag systems to be used with recombinant proteins for various purposes. Here we describe a new family of tag derived from the epitope recognized by a highly specific mAb G196. The minimal epitope was identified as the five amino acid sequence Asp-Leu-Val-Pro-Arg. Permutation analysis was used to characterize the binding requirements of mAb G196, and the variable regions of the mAb G196 were identified and structurally analyzed by X-ray crystallography. Isothermal titration calorimetry revealed the high affinity (K_d = 1.25 nM) of the mAb G196/G196-epitope peptide interaction, and G196-tag was used to detect several recombinant cytosolic and nuclear proteins in human and yeast cells. mAb G196 is valuable for developing a new peptide tagging system for cell biology and biochemistry research.

Elevated Na+/H+ exchanger-1 expression enhances the metastatic collective migration of head and neck squamous cell carcinoma cells

Cancer cells can migrate as collectives during invasion and/or metastasis; however, the precise molecular mechanisms of this form of migration are less clear compared with single cell migration following epithelial-mesenchymal transition. Elevated Na⁺/H⁺ exchanger1 (NHE1) expression has been suggested to have malignant roles in a number of cancer cell lines and in vivo tumor models. Furthermore, a metastatic human head and neck squamous cell carcinoma (HNSCC) cell line (SASL1m) that was isolated based on its increased metastatic potential also exhibited higher NHE1 expression than its parental line SAS. Time-lapse video recordings indicated that both cell lines migrate as collectives, although with different features, e.g., SASL1m was much more active and changed the direction of migration more frequently than SAS cells, whereas locomotive activities were comparable. SASL1m cells also exhibited higher invasive activity than SAS in Matrigel invasion assays. shRNA-mediated NHE1 knockdown in SASL1m led to reduced locomotive and invasive activities, suggesting a critical role for NHE1 in the collective migration of SASL1m cells. SASL1m cells also exhibited a higher metastatic rate than SAS cells in a mouse lymph node metastasis model, while NHE1 knockdown suppressed in vivo SASL1m metastasis. Finally, elevated NHE1 expression was observed in human HNSCC tissue, and Cariporide, a specific NHE1 inhibitor, reduced the invasive activity of SASL1m cells, implying NHE1 could be a target for anti-invasion/metastasis therapy.

Tension in Cancer

Integrins represent a large family of cell receptors that mediate adhesion to the extracellular matrix (ECM), thereby modulating a variety of cellular functions that are required for proliferation, migration, malignant conversion and invasiveness. During tumorigenesis the conversion of a tumor cell from sessile, stationary phenotype to an invasive phenotype requires the ability of tumor cells to interact with their environment in order to transduce signals from the ECM into the cells. Hence, there is increasing evidence that changes in the composition, topography and tension of tumor matrix can be sensed by integrin receptors, leading to the regulation of intracellular signalling events which subsequently help to fuel cancer progression. The fact that intracellular signals perceived from integrin ligand binding impact on almost all steps of tumor progression, including tumor cell proliferation, survival, metastatic dissemination and colonization of a metastatic niche, renders integrins as ideal candidates for the development of therapeutic agents. In this review we summarize the role of integrins in cancer with the special focus on cancer therapies and the recent progress that has been made in the understanding of “integrin-induced tension in cancer”. Finally, we conclude with clinical evidence for the role of integrin-mediated mechanotransduction in the development of therapy-resistant tumors.

β1 Integrin as a Prognostic and Predictive Marker in Triple-Negative Breast Cancer

Triple negative breast cancer (TNBC) displays higher risk of recurrence and distant metastasis. Due to absence of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2), TNBC lacks clinically established targeted therapies. Therefore, understanding of the mechanism underlying the aggressive behaviors of TNBC is required for the design of individualized strategies and the elongation of overall survival duration. Here, we supported a positive correlation between β1 integrin and malignant behaviors such as cell migration, invasion, and drug resistance. We found that silencing of β1 integrin inhibited cell migration, invasion, and increased the sensitivity to anti-cancer drug. In contrast, activation of β1 integrin increased cell migration, invasion, and decreased the sensitivity to anti-cancer drug. Furthermore, we found that silencing of β1 integrin abolished Focal adhesion kinese (FAK) mediated cell survival. Overexpression of FAK could restore cisplatin-induced apoptosis in β1 integrin-depleted cells. Consistent to in vitro data, β1 integrin expression was also positively correlated with FAK (p = 0.031) in clinical tissue. More importantly, β1 integrin expression was significantly correlated with patient outcome. In summary, our study indicated that β1 integrin could regulate TNBC cells migration, invasion, drug sensitivity, and be a potential prognostic biomarker in TNBC patient survival.

Accumulation of arachidonic acid-containing phosphatidylinositol at the outer edge of colorectal cancer

Accumulating evidence indicates that cancer cells show specific alterations in phospholipid metabolism that contribute to tumour progression in several types of cancer, including colorectal cancer. Questions still remain as to what lipids characterize the outer edge of cancer tissues and whether those cancer outer edge-specific lipid compositions emerge autonomously in cancer cells. Cancer tissue-originated spheroids (CTOSs) that are composed of pure primary cancer cells have been developed. In this study, we aimed to seek out the cancer cell-autonomous acquisition of cancer outer edge-characterizing lipids in colorectal cancer by analysing phospholipids in CTOSs derived from colorectal cancer patients with matrix-assisted laser desorption/ionization (MALDI)-imaging mass spectrometry (IMS). A signal at m/z 885.5 in negative ion mode was detected specifically at the surface regions. The signal was identified as an arachidonic acid (AA)-containing phosphatidylinositol (PI), PI(18:0/20:4), by tandem mass spectrometry analysis. Quantitative analysis revealed that the amount of PI(18:0/20:4) in the surface region of CTOSs was two-fold higher than that in the medial region. Finally, PI(18:0/20:4) was enriched at the cancer cells/stromal interface in colorectal cancer patients. These data imply a possible importance of AA-containing PI for colorectal cancer progression, and suggest cells expressing AA-containing PI as potential targets for anti-cancer therapy.

Targeting oncomiRNAs and mimicking tumor suppressor miRNAs: Νew trends in the development of miRNA therapeutic strategies in oncology (Review)

MicroRNA (miRNA or miR) therapeutics in cancer are based on targeting or mimicking miRNAs involved in cancer onset, progression, angiogenesis, epithelial-mesenchymal transition and metastasis. Several studies conclusively have demonstrated that miRNAs are deeply involved in tumor onset and progression, either behaving as tumor-promoting miRNAs (oncomiRNAs and metastamiRNAs) or as tumor suppressor miRNAs. This review focuses on the most promising examples potentially leading to the development of anticancer, miRNA-based therapeutic protocols. The inhibition of miRNA activity can be readily achieved by the use of miRNA inhibitors and oligomers, including RNA, DNA and DNA analogues (miRNA antisense therapy), small molecule inhibitors, miRNA sponges or through miRNA masking. On the contrary, the enhancement of miRNA function (miRNA replacement therapy) can be achieved by the use of modified miRNA mimetics, such as plasmid or lentiviral vectors carrying miRNA sequences. Combination strategies have been recently developed based on the observation that i) the combined administration of different antagomiR molecules induces greater antitumor effects and ii) some anti-miR molecules can sensitize drug-resistant tumor cell lines to therapeutic drugs. In this review, we discuss two additional issues: i) the combination of miRNA replacement therapy with drug administration and ii) the combination of antagomiR and miRNA replacement therapy. One of the solid results emerging from different independent studies is that miRNA replacement therapy can enhance the antitumor effects of the antitumor drugs. The second important conclusion of the reviewed studies is that the combination of anti-miRNA and miRNA replacement strategies may lead to excellent results, in terms of antitumor effects.

Collective invasion of cancer: Perspectives from pathology and development

Clinical pathologists have long been aware that in many types of human malignant tumors, the cells are often connected and form groups of various sizes or "nests". In this way, they achieve "collective invasion" into the surrounding stroma, rather than spreading out individually. Such collective behavior is also a common feature of migration during embryonic and postnatal developmental stages, suggesting there are advantages gained by collective cell migration in the organisms. Recent studies have revealed the mechanisms underlying the collective invasion of cancer cells. These mechanisms differ from those observed in the migration of single cells in culture, including reliance on the epithelial-mesenchymal transition program. Whereas intercellular adhesion appears to be coordinated, cancer cell groups can be heterogenous, including cells that are leaders and those that are followers. There is also interaction with the tumor microenvironment that is a prerequisite for collective invasion of cancer. In this review, we describe recently emerging mechanisms underlying the collective migration of cells, with a particular focus in our studies on the actin-binding protein Girdin/GIV and the transcriptional regulator tripartite motif containing 27. These studies provide new perspectives on the mechanistic analogy between cancer and development.

CC chemokine ligand 18(CCL18) promotes migration and invasion of lung cancer cells by binding to Nir1 through Nir1-ELMO1/DOC180 signaling pathway

Non-small cell lung cancer (NSCLC) comprises nearly 80% of lung cancers and the poor prognosis is due to its high invasiveness and metastasis. CC chemokine ligand 18 (CCL18) is predominantly secreted by M2-tumor associated macrophages (TAMs) and promotes malignant behaviors of various human cancer types. In this study, we report that the high expression of CCL18 in TAMs of NSCLC tissues and increased expression of CCL18 in TAMs is correlated with the lymph node metastasis, distant metastasis, and poor prognosis NSCLC patients. CCL18 can increase the invasive ability of NSCLC cells by binding to its receptor Nir1. In addition, CCL18 is capable of modulating cell migration and invasion by regulating the activation of RAC1 which resulted in cytoskeleton reorganization in an ELMO1 dependent manner. Furthermore, we found that CCL18 could enhance adhesion of NSCLC cells via activating ELMO1-integrin β1 signaling. Thus, CCL18 and its downstream molecules may be used as targets to develop novel NSCLC therapy. © 2016 Wiley Periodicals, Inc.

The roles of microRNAs in the regulation of tumor metastasis

MicroRNAs (miRNAs) are small noncoding regulatory RNAs that regulate gene expression post-transcriptionally by either inhibiting protein translation or degrading target mRNAs. The differential expression profiles of miRNAs in different types of cancers and in the multi-step process of tumor progression indicate that miRNAs are involved in tumor onset, growth and progression. Metastasis is the most common cause of cancer-related mortality. Current evidence demonstrates that aberrant miRNA expression promotes or inhibits tumor metastasis by modulating the expression of numerous target genes. Therefore, the identification of metastasis-related miRNAs and a better understanding of the complex functions of miRNAs in tumor metastasis will provide potential diagnostic and prognostic biomarkers, as well as therapeutic targets for clinical application. Here, we review the functions of miRNAs in the control of multiple steps of tumor metastasis.

Potential involvement of kinesin-1 in the regulation of subcellular localization of Girdin

Girdin is an actin-binding protein that has multiple functions in postnatal neural development and cancer progression. We previously showed that Girdin is a regulator of migration for neuroblasts born from neural stem cells in the subventricular zone (SVZ) and the dentate gyrus of the hippocampus in the postnatal brain. Despite a growing list of Girdin-interacting proteins, the mechanism of Girdin-mediated migration has not been fully elucidated. Girdin interacts with Disrupted-In-Schizophrenia 1 and partitioning-defective 3, both of which have been shown to interact with the kinesin microtubule motor proteins. Based on this, we have identified that Girdin also interacts with kinesin-1, a member of neuronal kinesin proteins. Although a direct interaction of Girdin and kinesin-1 has not been determined, it is of interest to find that Girdin loss-of-function mutant mice with the mutation of a basic amino acid residue-rich region (Basic mut mice) exhibit limited interaction with kinesin-1. Furthermore, expression of a kinesin-1 mutant with motor defects, leads to Girdin mislocalization. Finally, consistent with previous studies on the role of kinesin proteins in trafficking a cell-cell adhesion molecule N-cadherin, Basic mut mice showed an aberrant expression pattern of N-cadherin in migrating SVZ neuroblasts. These findings suggest a potential role of Girdin/kinesin-1 interaction in the regulation of neuroblast migration in the postnatal brain.

Regulated genes in mesenchymal stem cells and gastric cancer

AIM: To investigate the genes regulated in mesenchymal stem cells (MSCs) and diffuse-type gastric cancer (GC), gene expression was analyzed.

METHODS: Gene expression of MSCs and diffuse-type GC cells were analyzed by microarray. Genes related to stem cells, cancer and the epithelial-mesenchymal transition (EMT) were extracted from human gene lists using Gene Ontology and reference information. Gene panels were generated, and messenger RNA gene expression in MSCs and diffuse-type GC cells was analyzed. Cluster analysis was performed using the NCSS software.

RESULTS: The gene expression of regulator of G-protein signaling 1 (RGS1) was up-regulated in diffuse-type GC cells compared with MSCs. A panel of stem-cell related genes and genes involved in cancer or the EMT were examined. Stem-cell related genes, such as growth arrest-specific 6, musashi RNA-binding protein 2 and hairy and enhancer of split 1 (Drosophila), NOTCH family genes and Notch ligands, such as delta-like 1 (Drosophila) and Jagged 2, were regulated.

CONCLUSION: Expression of RGS1 is up-regulated, and genes related to stem cells and NOTCH signaling are altered in diffuse-type GC compared with MSCs.

Leader cells regulate collective cell migration via Rac activation in the downstream signaling of integrin β1 and PI3K

Collective cell migration plays a crucial role in several biological processes, such as embryonic development, wound healing, and cancer metastasis. Here, we focused on collectively migrating Madin-Darby Canine Kidney (MDCK) epithelial cells that follow a leader cell on a collagen gel to clarify the mechanism of collective cell migration. First, we removed a leader cell from the migrating collective with a micromanipulator. This then caused disruption of the cohesive migration of cells that followed in movement, called “follower” cells, which showed the importance of leader cells. Next, we observed localization of active Rac, integrin β1, and PI3K. These molecules were clearly localized in the leading edge of leader cells, but not in follower cells. Live cell imaging using active Rac and active PI3K indicators was performed to elucidate the relationship between Rac, integrin β1, and PI3K. Finally, we demonstrated that the inhibition of these molecules resulted in the disruption of collective migration. Our findings not only demonstrated the significance of a leader cell in collective cell migration, but also showed that Rac, integrin β1, and PI3K are upregulated in leader cells and drive collective cell migration.