Signaling through focal adhesion kinase

Proline-rich tyrosine kinase 2 mediates transforming growth factor-beta-induced hepatic stellate cell activation and liver fibrosis

Hepatic fibrogenesis is characterized by activation of hepatic stellate cells (HSCs) and accumulation of extracellular matrix (ECM). The impact of ECM on TGF-β-mediated fibrogenic signaling pathway in HSCs has remained obscure. We studied the role of non-receptor tyrosine kinase focal adhesion kinase (FAK) family members in TGF-β-signaling in HSCs. We used a CCl₄-induced liver fibrosis mice model to evaluate the effect of FAK family kinase inhibitors on liver fibrosis. RT-PCR and Western blot were used to measure the expression of its target genes; α-SMA, collagen, Nox4, TGF-β1, Smad7, and CTGF. Pharmacological inhibitors, siRNA-mediated knock-down, and plasmid-based overexpression were adopted to modulate the function and the expression level of proteins. Association of PYK2 activation with liver fibrosis was confirmed in liver samples from CCl₄-treated mice and patients with significant fibrosis or cirrhosis. TGF-β treatment up-regulated expression of α-SMA, type I collagen, NOX4, CTGF, TGF-β1, and Smad7 in LX-2 cells. Inhibition of FAK family members suppressed TGF-β-mediated fibrogenic signaling. SiRNA experiments demonstrated that TGF-β1 and Smad7 were upregulated via Smad-dependent pathway through FAK activation. In addition, CTGF induction was Smad-independent and PYK2-dependent. Furthermore, RhoA activation was essential for TGF-β-mediated CTGF induction, evidenced by using ROCK inhibitor and dominant negative RhoA expression. We identified that TGF-β1-induced activation of PYK2-Src-RhoA triad leads to YAP/TAZ activation for CTGF induction in liver fibrosis. These findings provide new insights into the role of focal adhesion molecules in liver fibrogenesis, and targeting PYK2 may be an attractive target for developing novel therapeutic strategies for the treatment of liver fibrosis.

Beta-arrestins operate an on/off control switch for focal adhesion kinase activity

Focal adhesion kinase (FAK) regulates key biological processes downstream of G protein-coupled receptors (GPCRs) in normal and cancer cells, but the modes of kinase activation by these receptors remain unclear. We report that after GPCR stimulation, FAK activation is controlled by a sequence of events depending on the scaffolding proteins β-arrestins and G proteins. Depletion of β-arrestins results in a marked increase in FAK autophosphorylation and focal adhesion number. We demonstrate that β-arrestins interact directly with FAK and inhibit its autophosphorylation in resting cells. Both FAK-β-arrestin interaction and FAK inhibition require the FERM domain of FAK. Following the stimulation of the angiotensin receptor AT1AR and subsequent translocation of the FAK-β-arrestin complex to the plasma membrane, β-arrestin interaction with the adaptor AP-2 releases inactive FAK from the inhibitory complex, allowing its activation by receptor-stimulated G proteins and activation of downstream FAK effectors. Release and activation of FAK in response to angiotensin are prevented by an AP-2-binding deficient β-arrestin and by a specific inhibitor of β-arrestin/AP-2 interaction; this inhibitor also prevents FAK activation in response to vasopressin. This previously unrecognized mechanism of FAK regulation involving a dual role of β-arrestins, which inhibit FAK in resting cells while driving its activation at the plasma membrane by GPCR-stimulated G proteins, opens new potential therapeutic perspectives in cancers with up-regulated FAK.

SWELL1 regulates skeletal muscle cell size, intracellular signaling, adiposity and glucose metabolism

Maintenance of skeletal muscle is beneficial in obesity and Type 2 diabetes. Mechanical stimulation can regulate skeletal muscle differentiation, growth and metabolism; however, the molecular mechanosensor remains unknown. Here, we show that SWELL1 (Lrrc8a) functionally encodes a swell-activated anion channel that regulates PI3K-AKT, ERK1/2, mTOR signaling, muscle differentiation, myoblast fusion, cellular oxygen consumption, and glycolysis in skeletal muscle cells. LRRC8A over-expression in Lrrc8a KO myotubes boosts PI3K-AKT-mTOR signaling to supra-normal levels and fully rescues myotube formation. Skeletal muscle-targeted Lrrc8a KO mice have smaller myofibers, generate less force ex vivo, and exhibit reduced exercise endurance, associated with increased adiposity under basal conditions, and glucose intolerance and insulin resistance when raised on a high-fat diet, compared to wild-type (WT) mice. These results reveal that the LRRC8 complex regulates insulin-PI3K-AKT-mTOR signaling in skeletal muscle to influence skeletal muscle differentiation in vitro and skeletal myofiber size, muscle function, adiposity and systemic metabolism in vivo.

FAK Promotes Early Osteoprogenitor Cell Proliferation by Enhancing mTORC1 Signaling

Focal adhesion kinase (FAK) has important functions in bone homeostasis but its role in early osteoprogenitor cells is unknown. We show herein that mice lacking FAK in Dermo1-expressing cells exhibited low bone mass and decreased osteoblast number. Mechanistically, FAK-deficient early osteoprogenitor cells had decreased proliferation and significantly reduced mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling, a central regulator of cell growth and proliferation. Furthermore, our data showed that the pharmacological inhibition of FAK kinase-dependent function alone was sufficient to decrease the proliferation and compromise the mineralization of early osteoprogenitor cells. In contrast to the Fak deletion in early osteoprogenitor cells, FAK loss in Col3.6 Cre-targeted osteoblasts did not cause bone loss, and Fak deletion in osteoblasts did not affect proliferation, differentiation, and mTORC1 signaling but increased the level of active proline-rich tyrosine kinase 2 (PYK2), which belongs to the same non-receptor tyrosine kinase family as FAK. Importantly, mTORC1 signaling in bone marrow stromal cells (BMSCs) was reduced if FAK kinase was inhibited at the early osteogenic differentiation stage. In contrast, mTORC1 signaling in BMSCs was not affected if FAK kinase was inhibited at a later osteogenic differentiation stage, in which, however, the concomitant inhibition of both FAK kinase and PYK2 kinase reduced mTORC1 signaling. In summary, our data suggest that FAK promotes early osteoprogenitor cell proliferation by enhancing mTORC1 signaling via its kinase-dependent function and the loss of FAK in osteoblasts can be compensated by the upregulated active PYK2. © 2020 American Society for Bone and Mineral Research.

A non-GPCR-binding partner interacts with a novel surface on β-arrestin1 to mediate GPCR signaling

The multifaceted adaptor protein β-arr1 (β-arrestin1) promotes activation of focal adhesion kinase (FAK) by the chemokine receptor CXCR4, facilitating chemotaxis. This function of β-arr1 requires the assistance of the adaptor protein STAM1 (signal-transducing adaptor molecule 1) because disruption of the interaction between STAM1 and β-arr1 reduces CXCR4-mediated activation of FAK and chemotaxis. To begin to understand the mechanism by which β-arr1 together with STAM1 activates FAK, we used site-directed spin-labeling EPR spectroscopy-based studies coupled with bioluminescence resonance energy transfer-based cellular studies to show that STAM1 is recruited to activated β-arr1 by binding to a novel surface on β-arr1 at the base of the finger loop, at a site that is distinct from the receptor-binding site. Expression of a STAM1-deficient binding β-arr1 mutant that is still able to bind to CXCR4 significantly reduced CXCL12-induced activation of FAK but had no impact on ERK-1/2 activation. We provide evidence of a novel surface at the base of the finger loop that dictates non-GPCR interactions specifying β-arrestin-dependent signaling by a GPCR. This surface might represent a previously unidentified switch region that engages with effector molecules to drive β-arrestin signaling.

Circulating extracellular vesicles from patients with breast cancer enhance migration and invasion via a Src‑dependent pathway in MDA‑MB‑231 breast cancer cells

Triple negative breast cancer (TNBC) is a breast cancer subtype associated with high rates of metastasis, heterogeneity, drug resistance and a poor prognosis. Extracellular vesicles (EVs) are vesicles of endosomal and plasma membrane origin, and are secreted by healthy and cancer cells. In cancer, EVs contribute to tumor progression by mediating escape from the immune system surveillance, and are involved in extracellular matrix degradation, invasion, angiogenesis, migration and metastasis. Furthermore, EVs have been identified in several human fluids. However, the role of EVs from patients with breast cancer in the migration and invasion of human breast cancer cells is not fully understood. The present study investigated whether EVs isolated from Mexican patients with breast cancer can induce cellular processes related to invasion in breast cancer. Moreover, plasma fractions enriched in EVs and deprived of platelet-derived EVs obtained from blood samples of 32 Mexican patients with biopsy-diagnosed breast cancer at different clinical stages who had not received treatment were analyzed. Furthermore, one control group was included, which consisted of 20 Mexican healthy females. The present results demonstrated that EVs from women with breast cancer promote migration and invasion, and increase matrix metalloproteinase (MMP)-2 and MMP-9 secretion in TNBC MDA-MB-231 cells. In addition, it was found that EVs from patients with breast cancer induced Src and focal adhesion kinase activation, and focal adhesions assembly with an increase in focal adhesions number, while the migration and invasion was dependent on Src activity. Collectively, EVs from Mexican patients with breast cancer induce migration and invasion via a Src-dependent pathway in TNBC MDA-MB-231 cells.

Aquaporin 1 elicits cell motility and coordinates vascular bed formation by downregulating thrombospondin type-1 domain-containing 7A in glioblastoma

BACKGROUND

Aquaporin (AQP) 1 expression has been linked with tumor malignancy but its role in glioblastoma (GBM), a lethal glioma, remains to be clarified.

METHODS

AQP1 expression was examined in 33 human GBM specimens by immunohistochemistry. GBM cells (U251 and U87) that stably express AQP1 were established and used for cellular proliferation, migration, invasion, and vascular tube formation assays. The GeneChip assay was used to identify differentially expressed genes in AQP1-expressing cells.

RESULTS

AQP1 was expressed only in tumor cells. AQP1 dose-dependently accelerated cell migration and invasion, but not proliferation, in GBM cell lines. AQP1 also upregulated cathepsin B, focal adhesion kinase and activities of matrix metalloproteinase 9. AQP1 in GBM cells induced wall thickness of ECV304, vascular endothelial cells, in a contact-dependent manner. Downregulation of thrombospondin type 1 domain containing 7A (THSD7A) was identified in AQP1-expressing GBM cells in vitro, and was negatively correlated with AQP1 expression in human GBM specimens.

CONCLUSION

AQP1 is involved in tumor malignancy by facilitating the migration and invasion of GBM cells, and promoting the formation of vascular beds that are characteristic of GBM by downregulating THSD7A.

Mechanotransduction in osteogenesis

Bone is one of the most highly adaptive tissues in the body, possessing the capability to alter its morphology and function in response to stimuli in its surrounding environment. The ability of bone to sense and convert external mechanical stimuli into a biochemical response, which ultimately alters the phenotype and function of the cell, is described as mechanotransduction. This review aims to describe the fundamental physiology and biomechanisms that occur to induce osteogenic adaptation of a cell following application of a physical stimulus. Considerable developments have been made in recent years in our understanding of how cells orchestrate this complex interplay of processes, and have become the focus of research in osteogenesis. We will discuss current areas of preclinical and clinical research exploring the harnessing of mechanotransductive properties of cells and applying them therapeutically, both in the context of fracture healing and de novo bone formation in situations such as nonunion.

Cite this article: Bone Joint Res 2019;9(1):1–14.

Progressive Myofibril Reorganization of Human Cardiomyocytes on a Dynamic Nanotopographic Substrate

Cardiomyocyte (CM) alignment with striated myofibril organization is developed during early cardiac organogenesis. Previous work has successfully achieved in vitro CM alignment using a variety of biomaterial scaffolds and substrates with static topographic features. However, the cellular processes that occur during the response of CMs to dynamic surface topographic changes, which may provide a model of in vivo developmental progress of CM alignment within embryonic myocardium, remains poorly understood. To gain insights into these cellular processes involved in the response of CMs to dynamic topographic changes, we developed a dynamic topographic substrate that employs a shape memory polymer coated with polyelectrolyte multilayers to produce a flat-to-wrinkle surface transition when triggered by a change in incubation temperature. Using this system, we investigated cellular morphological alignment and intracellular myofibril reorganization in response to the dynamic wrinkle formation. Hence, we identified the progressive cellular processes of human-induced pluripotent stem cell-CMs in a time-dependent manner, which could provide a foundation for a mechanistic model of cardiac myofibril reorganization in response to extracellular microenvironment changes.

Side chain effect in the modulation of αvβ3/α5β1 integrin activity via clickable isoxazoline-RGD-mimetics: development of molecular delivery systems

Construction of small molecule ligand (SML) based delivery systems has been performed starting from a polyfunctionalized isoxazoline scaffold, whose αvβ3 and α5β1 integrins' potency has been already established. The synthesis of this novel class of ligands was obtained by conjugation of linkers to the heterocyclic core via Huisgen-click reaction, with the aim to use them as "shuttles" for selective delivery of diagnostic agents to cancer cells, exploring the effects of the side chains in the interaction with the target. Compounds 17b and 24 showed excellent potency towards α5β1 integrin acting as selective antagonist and agonist respectively. Further investigations confirmed their effects on target receptor through the analysis of fibronectin-induced ERK1/2 phosphorylation. In addition, confocal microscopy analysis allowed us to follow the fate of EGFP conjugated α5β1 integrin and 17b FITC-conjugated (compound 31) inside the cells. Moreover, the stability in water solution at different values of pH and in bovine serum confirmed the possible exploitation of these peptidomimetic molecules for pharmaceutical application.

Endosulfan promotes cell migration via PTP4A3-mediated signaling pathways in HUVECs

Endosulfan is a persistent organic pollutant and can cause endothelial dysfunction, closely related to cardiovascular diseases. Endothelial cell migration plays a critical role in atherosclerosis and angiogenesis. This study was aimed to investigate the effect of environmentally relevant doses of endosulfan and underlying molecular mechanism on endothelial cell migration. Human umbilical vein endothelial cells (HUVECs) were treated with DMSO (control) or endosulfan (0.1, 1, 10 and 20 μM) in the presence or absence of inhibitors. Wound healing and Transwell assay were employed to explore the effect of endosulfan on endothelial cell migration. The expression of genes or proteins was assayed by real-time PCR or immunoblotting. The results showed that endosulfan at relative low concentration (0.1, 1, 10 and 20 μM) increased cell migration ability horizontally and vertically at 12 h after exposure. In line with this cellular effect, Protein-tyrosine Phosphatase 4A3 (PTP4A3) expression was significantly increased in endosulfan-exposed endothelial cells. Specific inhibitor of PTP4A3 significantly inhibited 20 μM endosulfan-induced cell migration, the expression and phosphorylation of Src and phosphorylation of focal adhesion kinase (FAK). Exposure to endosulfan resulted in activation of various signaling pathways including phosphoinositide 3-kinase (PI3K)/AKT, mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB), which were suppressed by PTP4A3 inhibitor or specific inhibitor for each signaling pathway. Exposure to endosulfan significantly reduced nitric oxide production and caused oxidative stress in HUVECs. These findings suggest that endosulfan promoted cell migration through PTP4A3-mediated various signaling pathways in endothelial cells.

FAK-Dependent Cell Motility and Cell Elongation

Fibroblastic cells show specific substrate selectivity for typical cell–substrate adhesion. However, focal adhesion kinase (FAK) contributes to controlling the regulation of orientation and polarity. When fibroblasts attach to micropatterns, tyrosine-phosphorylated proteins and FAK are both detected along the inner border between the adhesive micropatterns and the nonadhesive glass surface. FAK likely plays important roles in regulation of cell adhesion to the substrate, as FAK is a tyrosine-phosphorylated protein that acts as a signal transduction molecule at sites of cell–substrate attachment, called focal adhesions. FAK has been suggested to play a role in the attachment of cells at adhesive micropatterns by affecting cell polarity. Therefore, the localization of FAK might play a key role in recognition of the border of the cell with the adhesive micropattern, thus regulating cell polarity and the cell axis. This review discusses the regulation and molecular mechanism of cell proliferation and cell elongation by FAK and its associated signal transduction proteins.

Adhesions Assemble!-Autoinhibition as a Major Regulatory Mechanism of Integrin-Mediated Adhesion

The advent of cell-cell and cell-extracellular adhesion enabled cells to interact in a coherent manner, forming larger structures and giving rise to the development of tissues, organs and complex multicellular life forms. The development of such organisms required tight regulation of dynamic adhesive structures by signaling pathways that coordinate cell attachment. Integrin-mediated adhesion to the extracellular matrix provides cells with support, survival signals and context-dependent cues that enable cells to run different cellular programs. One mysterious aspect of the process is how hundreds of proteins assemble seemingly spontaneously onto the activated integrin. An emerging concept is that adhesion assembly is regulated by autoinhibition of key proteins, a highly dynamic event that is modulated by a variety of signaling events. By enabling precise control of the activation state of proteins, autoinhibition enables localization of inactive proteins and the formation of pre-complexes. In response to the correct signals, these proteins become active and interact with other proteins, ultimately leading to development of cell-matrix junctions. Autoinhibition of key components of such adhesion complexes—including core components integrin, talin, vinculin, and FAK and important peripheral regulators such as RIAM, Src, and DLC1—leads to a view that the majority of proteins involved in complex assembly might be regulated by intramolecular interactions. Autoinhibition is relieved via multiple different signals including post-translation modification and proteolysis. More recently, mechanical forces have been shown to stabilize and increase the lifetimes of active conformations, identifying autoinhibition as a means of encoding mechanosensitivity. The complexity and scope for nuanced adhesion dynamics facilitated via autoinhibition provides numerous points of regulation. In this review, we discuss what is known about this mode of regulation and how it leads to rapid and tightly controlled assembly and disassembly of cell-matrix adhesion.

TMT-based quantitative proteomics revealed follicle-stimulating hormone (FSH)-related molecular characterizations for potentially prognostic assessment and personalized treatment of FSH-positive non-functional pituitary adenomas

BACKGROUND

Non-functional pituitary adenoma (NFPA) is highly heterogeneous with different hormone expression subtypes. Of them, follicle-stimulating hormone (FSH)-positive expression is an important subtype of NFPAs. It is well-known that FSH exerted its functions through binding its receptor. However, the expression rate of FSH receptor was significantly higher in aggressive pituitary adenomas. This study aimed to investigate the molecular characteristics of FSH-positive NFPAs for effective stratification of patient, target treatment, prognostic assessment, and personalized treatment of FSH-positive NFPAs.

METHODS

Tandem mass tag (TMT)-based quantitative proteomics was used to investigate differentially expressed proteins (DEPs) between FSH-positive and negative NFPAs. Gene ontology and KEGG pathway enrichment analyses were used to analyze the DEPs. Differentially expressed genes (DEGs) between invasive and non-invasive NFPAs from GEO database were analyzed with pathway enrichment analysis. Protein-protein interaction (PPI) networks were constructed based on DEPs in excetral cellular matrix (ECM)-receptor interaction, focal adhesion, and PI3K-Akt pathways. Cytoscape was used to obtain most significant modules. Western blot was used to validate the expressions of upregulated proteins (ITGA1, ITGA6, and ITGB4), the expression and phosphorylated status of Akt in PI3K-Akt pathway, and the expression of FSH receptors in FSH-positive relative to negative NFPAs.

RESULTS

A total of 594 DEPs (374 upregulated and 220 downregulated) were identified between FSH-positive and negative NFPAs. Nineteen KEGG pathway networks were identified to involve DEPs, and reveal molecular differences between FSH-positive and negative NFPAs, including three important pathways that were significantly associated with tumor invasiveness and aggressiveness: ECM-receptor interaction, focal adhesion, and PI3K-Akt signaling pathways. Further, focal adhesion pathway was also confirmed with invasiveness-related NFPA DEG data that were derived from GEO database. Moreover, the significantly upregulated DEPs (ITGA1, ITGA6, and ITGB4) that were associated with tumor invasiveness and aggressiveness were confirmed by immunoaffinity analysis in FSH-positive vs. negative NFPAs. Also, the phosphorylation level but not its expression level of AKT in PI3K-AKT signaling was significantly increased, and the expression level of FSH receptor was significantly increased in FSH-positive relative to negative NFPAs. Also, overlapping analysis of 594 DEPs and 898 DEGs revealed 45 invasiveness-related DEPs, including 11 upregulated DEPs (ITGA6, FARP1, PALLD, PPBP, LIMA1, SCD, UACA, BAG3, CLU, PLEC, and GATM) that were also upregulated genes in invasive NFPAs, and 8 downregulated DEPs (ALCAM, HP, FSTL4, IL13RA2, NPTX2, DPP6, CRABP2, and SLC27A2) that were also downregulated genes in invasive NFPAs.

CONCLUSIONS

FSH-positive expression was an important NFPA subtype. It was the first time for this study to reveal FSH-related proteomic variations and the corresponding molecular network alterations in FSH-positive relative to negative NFPAs. Also, three signaling pathways (ECM-receptor interaction, focal adhesion, and PI3K-Akt signaling pathways) and involved upregulated proteins (ITGA1, ITGA6, ITGB4, pAKT, and FSHR) were significantly associated with tumor invasiveness and aggressiveness, and a set of invasiveness-related DEPs were identified with overlapping analysis of 594 DEPs in FSH-positive vs. negative NFPAs and 898 DEGs in invasive vs. non-invasive NFPAs. These findings offered the scientific evidence to in-depth understand molecular characteristics of FSH-positive NFPAs, and effectively stratify the post-surgery patients for personalized prognostic assessment and targeted treatment of FSH-positive NFPAs.

Glutathione peroxidase-1 regulates adhesion and metastasis of triple-negative breast cancer cells via FAK signaling

Triple-negative breast cancer (TNBC) cells, which do not express genes for estrogen receptor (ER), progesterone receptor (PR), and Her2/neu, develop highly aggressive and metastatic tumors resistant to chemo- and hormonal therapies. We found that expression of glutathione peroxidase-1 (Gpx1) is silenced in the non-TNBC cells but significantly maintained in the TNBC cell lines. Such Gpx1 expression plays a vital role in the metastasis of TNBC cells by regulating cell adhesion. Transcriptomic and signaling pathway analyses demonstrate that depletion of Gpx1 essentially impairs cell adhesion/spreading by down-regulating FAK/c-Src activation. Mechanistically, Gpx1 interacts with FAK kinase and prevents the kinase inactivation by H₂O₂, not lipid hydroperoxide. As a result, depletion of Gpx1 suppresses lung metastasis of TNBC cells in vivo. Overall, our study identifies that Gpx1 is a redox safeguard of FAK kinase and its inhibition may provide an effective way to control the metastasis of deadly malignant TNBC.

Induced Pluripotent Stem Cells Attenuate Endothelial Leakage in Acute Lung Injury via Tissue Inhibitor of Metalloproteinases-1 to Reduce Focal Adhesion Kinase Activity

Induced pluripotent stem cells (iPSCs) can reduce the severity of endotoxin-induced acute lung injury (ALI). However, the interaction between iPSCs and vascular endothelium remains unclear. In this study, we investigated the effects of iPSCs in moderating pulmonary endothelial leakage in endotoxin-induced ALI. Murine iPSCs were delivered intravenously to male C57BL/6 mice (8-12 weeks old) 4 hours after intratracheal lipopolysaccharide (LPS) delivery. Histology, blood and bronchoalveolar lavage fluid (BALF) cytokine and junctional protein assays, and regulatory signaling pathway assays were performed 24 hours later. Human umbilical vein endothelial cells (HUVECs) were used as a model of junctional protein-expressing cells and stimulated with LPS. Our results showed that iPSC treatment alleviated histological signs of ALI, protein leakage, and proinflammatory cytokines. iPSC therapy restored vascular endothelial cadherin (VE-cadherin) expression in ALI mouse lungs. In HUVECs, human iPSCs (hiPSCs) restored disrupted VE-cadherin expression and reduced the activity of Snail and focal adhesion kinase (FAK) phosphorylation in Tyr397 in response to LPS. iPSC-conditioned medium contained extra antiangiogenic factor of tissue inhibitor of metalloproteinases-1 (TIMP-1) compared with control medium. TIMP-1 inhibition diminished the beneficial effects of iPSC-conditioned medium in ALI mice. Our study suggested that iPSCs attenuate endothelial cell leakage in endotoxin-induced ALI via a mechanism involving TIMP-1 and the FAK/Snail pathway. Stem Cells 2019;37:1516-1527.

Neutrophil-Derived Reactive Oxygen Orchestrates Epithelial Cell Signaling Events during Intestinal Repair

Recent evidence has demonstrated that reactive oxygen (eg, hydrogen peroxide) can activate host cell signaling pathways that function in repair. We show that mice deficient in their capacity to generate reactive oxygen by the NADPH oxidase 2 holoenzyme, an enzyme complex highly expressed in neutrophils and macrophages, have disrupted capacity to orchestrate signaling events that function in mucosal repair. Similar observations were made for mice after neutrophil depletion, pinpointing this cell type as the source of the reactive oxygen driving oxidation-reduction protein signaling in the epithelium. To simulate epithelial exposure to high levels of reactive oxygen produced by neutrophils and gain new insight into this oxidation-reduction signaling, epithelial cells were treated with hydrogen peroxide, biochemical experiments were conducted, and a proteome-wide screen was performed using isotope-coded affinity tags to detect proteins oxidized after exposure. This analysis implicated signaling pathways regulating focal adhesions, cell junctions, and maintenance of the cytoskeleton. These pathways are also known to act via coordinated phosphorylation events within proteins that constitute the focal adhesion complex, including focal adhesion kinase and Crk-associated substrate. We identified the Rho family small GTP-binding protein Ras-related C3 botulinum toxin substrate 1 and p21 activated kinases 2 as operational in these signaling and localization pathways. These data support the hypothesis that reactive oxygen species from neutrophils can orchestrate epithelial cell-signaling events functioning in intestinal repair.

The Pivotal Roles of the Epithelial Membrane Protein Family in Cancer Invasiveness and Metastasis

The members of the family of epithelial membrane proteins (EMPs), EMP1, EMP2, and EMP3, possess four putative transmembrane domain structures and are composed of approximately 160 amino acid residues. EMPs are encoded by the growth arrest-specific 3 (GAS3)/peripheral myelin protein 22 kDa (PMP22) gene family. The GAS3/PMP22 family members play roles in cell migration, growth, and differentiation. Evidence indicates an association of these molecules with cancer progression and metastasis. Each EMP has pro- and anti-metastatic functions that are likely involved in the complex mechanisms of cancer progression. We have recently demonstrated that the upregulation of EMP1 expression facilitates cancer cell migration and invasion through the activation of a small GTPase, Rac1. The inoculation of prostate cancer cells overexpressing EMP1 into nude mice leads to metastasis to the lymph nodes and lungs, indicating that EMP1 contributes to metastasis. Pro-metastatic properties of EMP2 and EMP3 have also been proposed. Thus, targeting EMPs may provide new insights into their clinical utility. Here, we highlight the important aspects of EMPs in cancer biology, particularly invasiveness and metastasis, and describe recent therapeutic approaches.

A study of the focal adhesion kinase inhibitor GSK2256098 in patients with recurrent glioblastoma with evaluation of tumor penetration of [11C]GSK2256098

Background

GSK2256098 is a novel oral focal adhesion kinase (FAK) inhibitor. Preclinical studies demonstrate growth inhibition in glioblastoma cell lines. However, rodent studies indicate limited blood-brain barrier (BBB) penetration. In this expansion cohort within a phase I study, the safety, tolerability, pharmacokinetics (PK), and clinical activity of GSK2256098 were evaluated in patients with recurrent glioblastoma. Biodistribution and kinetics of [11C]GSK2256098 were assessed in a substudy using positron-emission tomography (PET).

Methods

Patients were treated with GSK2256098 until disease progression or withdrawal due to adverse events (AEs). Serial PK samples were collected on day 1. On a single day between days 9 and 20, patients received a microdose of intravenous [11C]GSK2256098 and were scanned with PET over 90 minutes with parallel PK sample collection. Response was assessed by MRI every 6 weeks.

Results

Thirteen patients were treated in 3 dose cohorts (1000 mg, 750 mg, 500 mg; all dosed twice daily). The maximum tolerated dose was 1000 mg twice daily. Dose-limiting toxicities were related to cerebral edema. Treatment-related AEs (>25%) were diarrhea, fatigue, and nausea. Eight patients participated in the PET substudy, with [11C]GSK2256098 VT (volume of distribution) estimates of 0.9 in tumor tissue, 0.5 in surrounding T2 enhancing areas, and 0.4 in normal brain. Best response of stable disease was observed in 3 patients, including 1 patient on treatment for 11.3 months.

Conclusions

GSK2256098 was tolerable in patients with relapsed glioblastoma. GSK2256098 crossed the BBB at low levels into normal brain, but at markedly higher levels into tumor, consistent with tumor-associated BBB disruption. Additional clinical trials of GSK2256098 are ongoing.

Increased Expression and Activation of FAK in Small-Cell Lung Cancer Compared to Non-Small-Cell Lung Cancer

INTRODUCTION

Focal adhesion kinase (FAK) plays a crucial role in cancer development and progression. FAK is overexpressed and/or activated and associated with poor prognosis in various malignancies. However, in lung cancer, activated FAK expression and its prognostic value are unknown.

METHODS

FAK and activated FAK (phospho-FAK Y397) expressions were analyzed by multiplex immunofluorescence staining in formalin-fixed paraffin-embedded tissues from 95 non-small-cell lung cancer (NSCLC) and 105 small-cell lung cancer (SCLC) patients, and 37 healthy donors. The FAK staining score was defined as the percentage (%) of FAK-stained tumor area multiplied by (×) FAK mean intensity and phospho-FAK staining score as the (% of phospho-FAK-stained area of low intensity × 1) + (% of phospho-FAK-stained area of medium intensity × 2) + (% of the phospho-FAK-stained area of high intensity × 3). FAK and phospho-FAK staining scores were compared between normal, NSCLC, and SCLC tissues. They were also tested for correlations with patient characteristics and clinical outcomes.

RESULTS

The median follow-up time after the first treatment was 42.5 months and 6.4 months for NSCLC and SCLC patients, respectively. FAK and phospho-FAK staining scores were significantly higher in lung cancer than in normal lung and significantly higher in SCLC compared to NSCLC tissues (p < 0.01). Moreover, the ratio between phospho-FAK and FAK staining scores was significantly higher in SCLC than in NSCLC tissues (p < 0.01). However, FAK and activated FAK expression in lung cancer did not correlate with recurrence-free and overall survival in NSCLC and SCLC patients.

CONCLUSIONS

Total FAK and activated FAK expressions are significantly higher in lung cancer than in normal lung, and significantly higher in SCLC compared to NSCLC, but are not prognostic biomarkers in this study.

Micropatterned conductive hydrogels as multifunctional muscle-mimicking biomaterials: Graphene-incorporated hydrogels directly patterned with femtosecond laser ablation

Multifunctional biomaterials that can provide physical, electrical, and structural cues to cells and tissues are highly desirable to mimic the important characteristics of native tissues and efficiently modulate cellular behaviors. Especially, electrically conductive biomaterials can efficiently deliver electrical signals to living systems; however, the production of conductive biomaterials presenting multiple cell interactive cues is still a great challenge. In this study, we fabricafed an electrically conductive, mechanically soft, and topographically active hydrogel by micropatterning a graphene oxide (GO)-incorporated polyacrylamide hydrogel (GO/PAAm) with femtosecond laser ablation (FLA) and subsequent chemical reduction. FLA parameters were optimized to efficiently produce distinct line patterns on GO/PAAm hydrogels to induce myoblast alignment and maturation. The line patterns distances (PD) were varied to have different topographies (20-80 μm PD). In vitro studies with C2C12 myoblasts revealed that the micopatterned hydrogels are superior to the unpatterned substrates in inducing myogenesis and myotube alignment. Reduced GO/PAAm with 50 μm PD, i.e., PD50/r(GO/PAAm), showed the best results among the various features for differentiation and myotube alignment. Electrical stimulation of myoblasts on the micropatterned conductive hydrogels further promoted the differentiation of myoblasts. In vivo implantation studies indicated good tissue compatibility of PD50/r(GO/PAAm) samples. Altogether, we successfully demonstrated that the micropatterned r(GO/PAAm) may offer multiple properties capable of positively affecting myoblast responses. This hydrogel may serve as an effective multifunctional biomaterial, which possesses the topography for cell alignment/maturation, mechanical properties of the native skeletal muscle tissue, and desirable electrical conductivity for delivering electrical signals to cells, for various biomedical applications such as muscle tissue scaffolds. STATEMENT OF SIGNIFICANCE: Micropatterned conductive hydrogels were created by polymerization of a graphene oxide-incorporated polyacrylamide hydrogel, micropatterning with femtosecond laser ablation, and chemical reduction, which can mimic important characteristics of native skeletal muscle tissues. The micropatterned conductive hydro-gels promoted myogenesis/alignment, enabled electrical stimulation of myoblasts, and displayed good tissue compatibility, which can therefore serve as a multifunctional biomaterial that is topographically active, mechanically soft, and electrically conductive for delivering multiple cell stimulating signals for potential skeletal muscle tissue engineering applications.

Flow-induced mechanotransduction in skeletal cells

Human body is subject to many and variegated mechanical stimuli, actuated in different ranges of force, frequency, and duration. The process through which cells "feel" forces and convert them into biochemical cascades is called mechanotransduction. In this review, the effects of fluid shear stress on bone cells will be presented. After an introduction to present the major players in bone system, we describe the mechanoreceptors in bone tissue that can feel and process fluid flow. In the second part of the review, we present an overview of the biological processes and biochemical cascades initiated by fluid shear stress in bone cells.

Tumor Angiogenesis Is Differentially Regulated by Phosphorylation of Endothelial Cell Focal Adhesion Kinase Tyrosines-397 and -861

Expression of focal adhesion kinase (FAK) in endothelial cells (EC) is essential for angiogenesis, but how FAK phosphorylation at tyrosine-(Y)397 and Y861 regulate tumor angiogenesis in vivo is unknown. Here, we show that tumor growth and angiogenesis are constitutively reduced in inducible, ECCre+;FAKY397F/Y397F -mutant mice. Conversely, ECCre+;FAKY861F/Y861F mice exhibit normal tumor growth with an initial reduction in angiogenesis that recovered in end-stage tumors. Mechanistically, FAK-Y397F ECs exhibit increased Tie2 expression, reduced Vegfr2 expression, decreased β1 integrin activation, and disrupted downstream FAK/Src/PI3K(p55)/Akt signaling. In contrast, FAK-Y861F ECs showed decreased Vegfr2 and Tie2 expression with an enhancement in β1 integrin activation. This corresponds with a decrease in Vegfa-stimulated response, but an increase in Vegfa+Ang2- or conditioned medium from tumor cell-stimulated cellular/angiogenic responses, mimicking responses in end-stage tumors with elevated Ang2 levels. Mechanistically, FAK-Y861F, but not FAK-Y397F ECs showed enhanced p190RhoGEF/P130Cas-dependent signaling that is required for the elevated responses to Vegfa+Ang2. This study establishes the differential requirements of EC-FAK-Y397 and EC-FAK-Y861 phosphorylation in the regulation of EC signaling and tumor angiogenesis in vivo. SIGNIFICANCE: Distinct motifs of the focal adhesion kinase differentially regulate tumor blood vessel formation and remodeling.

Pharmacological profiling of a dual FAK/IGF-1R kinase inhibitor TAE226 in cellular and in vivo tumor models

Objective

A dual inhibitor of focal adhesion kinase (FAK) and insulin-like growth factor 1 receptor (IGF-1R), TAE226, was evaluated in a panel of cancer cell lines, MIA PaCa-2 human pancreatic tumor and 4T1 murine breast tumor models. The profiling data were generated during the drug discovery research prior to the first publication of TAE226 appeared in 2007 (Liu et al. in Mol Cancer Ther 6:1357–1367, 2007; Shi et al. in Mol Carcinog 46(6):488–496, 2007; Halder et al. in Cancer Res 67(22):10976–10983, 2007).

Results

In a panel of 37 cancer cell lines, TAE226 showed a mean GI₅₀ value of 0.76 μmol/L. In the MIA PaCa-2 model, TAE226 inhibited phosphorylation of Y397-FAK and phosphorylation of S473-Akt as IGF-1R signaling in the cell culture in vitro and the tumor in mice. Oral administration of TAE226 induced tumor stasis at 30 mg/kg and tumor regression at 100 mg/kg in the subcutaneous tumor, and inhibited the orthotopic tumor growth in a dose-dependent manner. Similarly in the 4T1 model, TAE226 inhibited phosphorylation of Y397-FAK and S473-Akt in the cell culture in vitro and the tumor in mice. Oral administration of TAE226 inhibited the orthotopic tumor growth and metastasis to the lung in a dose-dependent manner. Thus, TAE226 represents a novel class of selective and small molecule kinase inhibitor with a potent in vivo activity.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4389-7) contains supplementary material, which is available to authorized users.

Evaluation of therapeutic effects of FAK inhibition in murine models of atherosclerosis

Objective

Therapeutic effects of focal adhesion kinase (FAK) inhibition using a small molecule inhibitor was evaluated in apolipoprotein E (apoE) knockout (KO) and low-density lipoprotein receptor (LDLr) KO mouse atherosclerosis models.

Results

The prevention trial consisted of an 8-week treatment with an FAK inhibitor concurrent treatment with a high fat (HF)/high cholesterol (HC) diet. The intervention trial consisted of 6- and 8-week treatment after 6- and 8-week pre-loading, respectively, of a HF/HC diet in apoE KO and LDLr KO mice, respectively. The inhibitor was admixed with a HF/HC diet and mice were given free access to the admixture. The FAK inhibitor exhibited marked inhibition against the development of the atherosclerosis in both of prevention and intervention trials at a dose of 0.03% without showing any remarkable toxic properties in biochemical examinations. These results indicated that FAK inhibition might be a possible candidate for novel therapeutic targets against atherosclerosis.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4220-5) contains supplementary material, which is available to authorized users.

ZINC4085554 inhibits cancer cell adhesion by interfering with the interaction of Akt1 and FAK

Perioperative or circulatory forces enhance disseminated cancer cell adhesiveness by modulating focal adhesion kinase (FAK)-Akt1 interaction. Selectively blocking FAK-Akt1 interaction by a peptide derived from the FAK-Four-point-one, ezrin, radixin, moesin (FERM) domain reduces colon cancer cell adhesion in vitro and in mice. A preliminary in silico screening identified two small molecules resembling a peptide that may inhibit pressure-stimulated SW620 cancer cell adhesion to collagen I. The present study selected ZINC4085554 for further study to validate its proposed mechanism of action, using human SW620 colon cancer cells as a model system. At 25 and 50 µM, ZINC4085554 inhibited the pressure-stimulated adhesion of SW620 colon cancer cells to collagen I. This molecule prevented pressure-stimulated FAK-Tyr-397 phosphorylation; however, it did not affect Akt1-Ser-473 phosphorylation, indicating that ZINC4085554 acts downstream of Akt1, while Akt-Thr-308 remains unchanged in the presence of pressure and or ZINC4085554. Indeed, ZINC4085554 inhibited FAK-Akt1 interaction in response to increased extracellular pressure, consistent with the proposed mechanism. ZINC4085554 did not inhibit FAK-Tyr-397 phosphorylation in response to cell adhesion to collagen I, indicating the specificity of the inhibitory effects towards force-stimulated pathways. Finally, the present study confirmed that ZINC4085554 at 50 µM prevented pressure-activation of adhesion to surgical wounds in vivo in parallel to its ablation of intracellular signaling. In summary, ZINC4085554 is a small molecule mimicking part of the structure of FAK that reduces cancer cell adhesion by impairing pressure-stimulated FAK-Akt1 interaction and its downstream consequences. ZINC4085554 does not inhibit conventional outside-in FAK signaling and may be less toxic than global FAK inhibitors, and ZINC4085554 may be an important step towards the inhibition of metastasis.

Induction of the Epithelial-to-Mesenchymal Transition of Human Colorectal Cancer by Human TNF-β (Lymphotoxin) and its Reversal by Resveratrol

Objective: Tumor necrosis factor-beta (TNF-β), as an inflammatory mediator that has been shown to promote tumorigenesis, induces NF-κB. Natural multi-targeted agent resveratrol in turn shows anti-inflammatory and anti-cancer properties. Epithelial-to-mesenchymal transition (EMT) allows cancer cells to turn into a motile state with invasive capacities and is associated with metastasis and development of cancer stem cells (CSC). However, TNF-β-induced EMT and the anti-invasion mechanism of resveratrol on CRC are not yet completely understood. Methods: We investigated the underlying molecular mechanisms of resveratrol on TNF-β/TNF-βR-induced EMT and migration of CRC cells (HCT116, RKO, SW480) in monolayer or 3D alginate cultures. Results: TNF-β, similar to TNF-α, induced significant cell proliferation, morphological change, from an epithelial to a spindle-like mesenchymal shape with the formation of filopodia and lamellipodia associated with the expression of EMT parameters (elevated vimentin and slug, reduced E-cadherin), increased migration/invasion, and formation of CSC in all CRC cells. Interestingly, these effects were dramatically decreased in the presence of resveratrol or anti-TNF-βR with TNF-β co-treatment, inducing biochemical changes to the mesenchymal-epithelial transition (MET), with a planar cell surface and suppressed formation of CSC cells. This was associated with a significant increase in apoptosis. Furthermore, we found that resveratrol suppressed TNF-β-induced NF-κB and NF-κB-regulated gene biomarkers associated with growth, proliferation, and invasion. Finally, TNF-βR interacts directly with focal adhesion kinase (FAK) and NF-κB. Conclusion: These results suggest that resveratrol down-regulates TNF-β/TNF-βR-induced EMT, at least in part via specific suppression of NF-κΒ and FAK in CRC cells.

Comparing Transcriptome Profiles of Neurons Interfacing Adjacent Cells and Nanopatterned Substrates Reveals Fundamental Neuronal Interactions

Developing neuronal axons are directed by chemical and physical signals toward a myriad of target cells. According to current dogma, the resulting network architecture is critically shaped by electrical interconnections, the synapses; however, key mechanisms translating neuronal interactions into neuronal growth behavior during network formation are still unresolved. To elucidate these mechanisms, we examined neurons interfacing nanopatterned substrates and compared them to natural interneuron interactions. We grew similar neuronal populations under three connectivity conditions, (1) the neurons are isolated, (2) the neurons are interconnected, and (3) the neurons are connected only to artificial substrates, then quantitatively compared both the cell morphologies and the transcriptome-expression profiles. Our analysis shows that whereas axon-guidance signaling pathways in isolated neurons are predominant, in isolated neurons interfacing nanotopography, these pathways are downregulated, similar to the interconnected neurons. Moreover, in nanotopography, interfacing neuron genes related to synaptogenesis and synaptic regulation are highly expressed, that is, again resembling the behavior of interconnected neurons. These molecular findings demonstrate that interactions with nanotopographies, although not leading to electrical coupling, play a comparable functional role in two major routes, neuronal guidance and network formation, with high relevance to the design of regenerative interfaces.

Cullin5 deficiency promotes small-cell lung cancer metastasis by stabilizing integrin β1

Metastasis is the dominant cause of patient death in small-cell lung cancer (SCLC), and a better understanding of the molecular mechanisms underlying SCLC metastasis may potentially improve clinical treatment. Through genome-scale screening for key regulators of mouse Rb1-/- Trp53-/- SCLC metastasis using the pooled CRISPR/Cas9 library, we identified Cullin5 (CUL5) and suppressor of cytokine signaling 3 (SOCS3), two components of the Cullin-RING E3 ubiquitin ligase complex, as top candidates. Mechanistically, the deficiency of CUL5 or SOCS3 disrupted the functional formation of the E3 ligase complex and prevented the degradation of integrin β1, which stabilized integrin β1 and activated downstream focal adhesion kinase/SRC (FAK/SRC) signaling and eventually drove SCLC metastasis. Low expression levels of CUL5 and SOCS3 were significantly associated with high integrin β1 levels and poor prognosis in a large cohort of 128 clinical patients with SCLC. Moreover, the CUL5-deficient SCLCs were vulnerable to the treatment of the FDA-approved SRC inhibitor dasatinib. Collectively, this work identifies the essential role of CUL5- and SOCS3-mediated integrin β1 turnover in controlling SCLC metastasis, which might have therapeutic implications.

E-cadherin, actin, microtubules and FAK dominate different spheroid formation phases and important elements of tissue integrity

Spheroids resemble features of tissues and serve as model systems to study cell–cell and cell–ECM interactions in non-adhesive three-dimensional environments. Although it is generally accepted that mature spheroids resemble tissue properties very well, no studies relate different phases in the spheroid formation processes that contribute to tissue integrity. Tissue integrity involves the cellular processes adhesion formation, adhesion reinforcement, rearrangement as well as proliferation. They maintain the structure and function of tissues and, upon dysregulation, contribute to malignancy. We investigated spheroid formation dynamics in cell lines of different metastatic potential. We dissected spheroid formation into phases of aggregation, compaction and growth to identify the respective contributions of E-cadherin, actin, microtubules and FAK. E-cadherin, actin and microtubules drive the first two phases. Microtubules and FAK are involved in the proliferation phase. FAK activity correlates with the metastatic potential of the cells. A robust computational model based on a very large number of experiments reveals the temporal resolution of cell adhesion. Our results provide novel hypotheses to unveil the general mechanisms that contribute to tissue integrity.

Summary: The phases of spheroid formation resemble different stages of cell contact formation. This facilitates studying the temporal contribution of molecules in this process.

The extracellular topographical environment influences ovarian cancer cell behaviour

The importance of the biophysical cellular environment in cancer development has been increasingly recognised but so far has been only superficially studied. Here we investigated the effect of cell-like substrate topography on ovarian cancer cell behaviour and potential underlying signalling pathways. We observed changes in cell morphology in response to substrate topography, which implies modification of structure-function associations. Differences in focal adhesion signalling and Rho/ROCK activity suggested their involvement in the biomechanically-driven cellular responses. Cell-like topography was also shown to modulate the MAPK pathway and hence potentially regulate cell proliferation. The selective regulation of the cells by the mechanotransduction pathways that we noted has wide ranging implications for understanding cancer development. We established that the physical architecture of cell culture substrate is sufficient to influence cancer cell behaviour, independent of genetic composition or biochemical milieu.

Regulation of Cell Survival, Apoptosis, and Epithelial-to-Mesenchymal Transition by Nitric Oxide-Dependent Post-Translational Modifications

SIGNIFICANCE

Nitric oxide (NO) is a physiopathological messenger generating different reactive nitrogen species (RNS) according to hypoxic, acidic and redox conditions. Recent Advances: RNS and reactive oxygen species (ROS) promote relevant post-translational modifications, such as nitrosation, nitration, and oxidation, in critical components of cell proliferation and death, epithelial-to-mesenchymal transition, and metastasis.

CRITICAL ISSUES

The pro- or antitumoral properties of NO are dependent on local concentration, redox state, cellular status, duration of exposure, and compartmentalization of NO generation. The increased expression of NO synthase has been associated with cancer progression. However, the experimental strategies leading to high intratumoral NO generation have been shown to exert antitumoral properties. The effect of NO and ROS on cell signaling is critically altered by factors modulating tumor progression such as oxygen content, metabolism, and inflammatory response. The review describes the alteration of key components involved in cell survival and death, metabolism, and metastasis induced by RNS- and ROS-related post-translational modifications.

FUTURE DIRECTIONS

The identification of the molecular targets affected by nitrosation, nitration, and oxidation, as well as their interactions with other post-translational modifications, will improve the understanding on the complex signaling and cell fate decision in cancer. The therapeutic NO-based strategies have to address the complex crosstalk among NO and ROS with regard to critical components affecting tumor cell survival, metabolism, and metastasis in the progression of cancer, as well as close interaction with ionizing radiation and chemotherapy.

Priming stem cells with protein kinase C activator enhances early stem cell-chondrocyte interaction by increasing adhesion molecules

BACKGROUND

Osteoarthritis (OA) can be defined as degradation of articular cartilage of the joint, and is the most common degenerative disease. To regenerate the damaged cartilage, different experimental approaches including stem cell therapy have been tried. One of the major limitations of stem cell therapy is the poor post-transplantation survival of the stem cells. Anoikis, where insufficient matrix support and adhesion to extracellular matrix causes apoptotic cell death, is one of the main causes of the low post-transplantation survival rate of stem cells. Therefore, enhancing the initial interaction of the transplanted stem cells with chondrocytes could improve the therapeutic efficacy of stem cell therapy for OA. Previously, protein kinase C activator phorbol 12-myristate 13-acetate (PMA)-induced increase of mesenchymal stem cell adhesion via activation of focal adhesion kinase (FAK) has been reported. In the present study, we examine the effect PMA on the adipose-derived stem cells (ADSCs) adhesion and spreading to culture substrates, and further on the initial interaction between ADSC and chondrocytes.

RESULTS

PMA treatment increased the initial adhesion of ADSC to culture substrate and cellular spreading with increased expression of adhesion molecules, such as FAK, vinculin, talin, and paxillin, at both RNA and protein level. Priming of ADSC with PMA increased the number of ADSCs attached to confluent layer of cultured chondrocytes compared to that of untreated ADSCs at early time point (4 h after seeding).

CONCLUSION

Taken together, the results of this study suggest that priming ADSCs with PMA can increase the initial interaction with chondrocytes, and this proof of concept can be used to develop a non-invasive therapeutic approach for treating OA. It may also accelerate the regeneration process so that it can relieve the accompanied pain faster in OA patients. Further in vivo studies examining the therapeutic effect of PMA pretreatment of ADSCs for articular cartilage damage are required.

Therapeutic Potential of Focal Adhesion Kinase Inhibition in Small Cell Lung Cancer

Small cell lung cancer (SCLC) has a poor prognosis. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase regulating cell proliferation, survival, migration, and invasion, which is overexpressed and/or activated in several cancers, including SCLC. We wanted to determine whether FAK contributes to SCLC aggressive behavior. We first evaluated the effect of FAK small-molecule inhibitor PF-573,228 in NCI-H82, NCI-H146, NCI-H196, and NCI-H446 SCLC cell lines. PF-573,228 (0.1-5 μmol/L) inhibited FAK activity by decreasing phospho-FAK (Tyr397), without modifying total FAK expression. PF-573,228 decreased proliferation, decreased DNA synthesis, induced cell-cycle arrest in G₂-M phases, and increased apoptosis in all cell lines. PF-573,228 also decreased motility in adherent cell lines. To make sure that these effects were not off-target, we then used a genetic method to inhibit FAK in NCI-H82 and NCI-H446, namely stable transduction with FAK shRNA and/or FAK-related nonkinase (FRNK), a splice variant lacking the N-terminal and kinase domains. Although FAK shRNA transduction decreased total and phospho-FAK (Tyr397) expression, it did not affect proliferation, DNA synthesis, or progression through cell cycle. However, restoration of FAK-targeting (FAT) domain (attached to focal adhesion complex where it inhibits pro-proliferative proteins such as Rac-1) by FRNK transduction inhibited proliferation, DNA synthesis, and induced apoptosis. Moreover, although FAK shRNA transduction increased active Rac1 level, FRNK reexpression in cells previously transduced with FAK shRNA decreased it. Therefore, FAK appears important in SCLC biology and targeting its kinase domain may have a therapeutic potential, while targeting its FAT domain should be avoided to prevent Rac1-mediated protumoral activity.

Cortical Actin Dynamics in Endothelial Permeability

The pulmonary endothelial cell forms a critical semi-permeable barrier between the vascular and interstitial space. As part of the blood-gas barrier in the lung, the endothelium plays a key role in normal physiologic function and pathologic disease. Changes in endothelial cell shape, defined by its plasma membrane, determine barrier integrity. A number of key cytoskeletal regulatory and effector proteins including non-muscle myosin light chain kinase, cortactin, and Arp 2/3 mediate actin rearrangements to form cortical and membrane associated structures in response to barrier enhancing stimuli. These actin formations support and interact with junctional complexes and exert forces to protrude the lipid membrane to and close gaps between individual cells. The current knowledge of these cytoskeletal processes and regulatory proteins are the subject of this review. In addition, we explore novel advancements in cellular imaging that are poised to shed light on the complex nature of pulmonary endothelial permeability.

Tyrosine phosphorylation of HDAC3 by Src kinase mediates proliferation of HER2-positive breast cancer cells

The role of histone deacetylase 3 (HDAC3) is to repress the expression of various genes by eliminating acetyl group from histone. Thus, the regulation of HDAC3 activity is essential to maintain cellular homeostasis. In this study, we found that HDAC3 interacts with c-Src kinase. However, the interaction between HDAC3 and c-Src was previously reported, it has still been ambiguous whether c-Src phosphorylates HDAC3 and affects the function of HDAC3. First, we confirmed that HDAC3 directly binds to c-Src, and c-Src identified to interact with C-terminal domain (277-428 a.a.) of HDAC3. c-Src also phosphorylated three tyrosine sites of HDAC3 at tyrosine 325, 328, and 331. Importantly, wild-type c-Src increases HDAC3 activity, but not mutant c-Src^K298M (kinase inactive form). When these tyrosine residues are all substituted for alanine residues, the deacetylase activity of mutant HDAC3 was abolished. In addition, a proliferation of HER2-positive breast cancer cells expressing phosphorylation deficient mutant HDAC3 is decreased in comparison with control cells. Thus, our findings suggested that phosphorylation of HDAC3 by c-Src kinase regulates the HDAC3 activity and the proliferation of breast cancer cells.

Human soluble phospholipase A2 receptor is an inhibitor of the integrin-mediated cell migratory response to collagen-I

Murine membrane-bound phospholipase A2 receptor 1 (PLA2R) is shed and released into plasma in a soluble form that retains all of the extracellular domains. Relatively little is known about human PLA2R. This study examined whether human soluble PLA2R has biological functions and whether soluble PLA2R exists in human plasma. Here, we showed that human recombinant soluble PLA2R (rsPLA2R) bound to collagen-I and inhibited interaction of collagen-I with the extracellular domain of integrin β1 on the cell surface of human embryonic kidney 293 (HEK293) cells. As a result, rsPLA2R suppressed integrin β1-mediated migratory responses of HEK293 cells to collagen-I in Boyden chamber experiments. Inhibition of phosphorylation of FAK Tyr397 was also observed. Similar results were obtained with experiments using soluble PLA2R released from HEK293 cells transfected with a construct encoding human soluble PLA2R. rsPLA2R lacking the fibronectin-like type II (FNII) domain had no inhibitory effects on cell responses to collagen-I, suggesting an important role of the FNII domain in the interaction of rsPLA2R with collagen-I. In addition, rsPLA2R suppressed the migratory response to collagen-IV and binding of collagen-IV to the cell surface of human podocytes that endogenously express membrane-bound, full-length PLA2R. Immunoprecipitation and Western blotting showed the existence of immunoreactive PLA2R in human plasma. In conclusion, human recombinant soluble PLA2R inhibits integrin β1-mediated cell responses to collagens. Further studies are warranted to elucidate whether immunoreactive PLA2R in human plasma has the same properties as rsPLA2R.

Counterbalance: modulation of VEGF/VEGFR activities by TNFSF15

Vascular hyperpermeability occurs in angiogenesis and several pathobiological conditions, producing elevated interstitial fluid pressure and lymphangiogenesis. How these closely related events are modulated is a fundamentally important question regarding the maintenance of vascular homeostasis and treatment of disease conditions such as cancer, stroke, and myocardial infarction. Signals mediated by vascular endothelial growth factor receptors, noticeably VEGFR-1, −2, and −3, are centrally involved in the promotion of both blood vessel and lymphatic vessel growth. These signaling pathways are counterbalanced or, in the case of VEGFR3, augmented by signals induced by tumor necrosis factor superfamily-15 (TNFSF15). TNFSF15 can simultaneously downregulate membrane-bound VEGFR1 and upregulate soluble VEGFR1, thus changing VEGF/VEGFR1 signals from pro-angiogenic to anti-angiogenic. In addition, TNFSF15 inhibits VEGF-induced VEGFR2 phosphorylation, thereby curbing VEGFR2-mediated enhancement of vascular permeability. Third, and perhaps more interestingly, TNFSF15 is capable of stimulating VEGFR3 gene expression in lymphatic endothelial cells, thus augmenting VEGF-C/D-VEGFR3-facilitated lymphangiogenesis. We discuss the intertwining relationship between the actions of TNFSF15 and VEGF in this review.

The ability of tumor necrosis factor superfamily-15 (TNFSF15) protein to balance the actions of vascular endothelial growth factors (VEGFs) highlights new therapeutic strategies for the treatment of diseases that disrupt the circulatory system. Gui-Li Yang at the Tianjin Neurological Institute and Lu-Yuan Li at Nankai University describe the mechanisms through which TNFSF15 inhibits blood vessel growth mediated by VEGF receptor-1 (VEGFR1) and counterbalances the increase in vascular permeability mediated by VEGFR2. Interestingly, TNFSF15 enhances the effects of VEGFR3 on the formation of lymphatic vessels by promoting VEGFR3 gene expression in lymphatic endothelial cells. Further research will determine whether TNFSF15′s unique capacity to regulate the properties of both blood and lymph vessels can be harnessed to improve the treatment of conditions such as cancer, stroke, myocardial infarction and lymphoedema.

Cycloartane triterpenoid (23R, 24E)-23-acetoxymangiferonic acid inhibited proliferation and migration in B16-F10 melanoma via MITF downregulation caused by inhibition of both β-catenin and c-Raf-MEK1-ERK signaling axis

We recently reported that (23R, 24E)-23-acetoxymangiferonic acid (23R-AMA), a cycloartane triterpenoid isolated by activity-guided separation from a methanol extract of Garcinia sp. bark, inhibited melanin production via inhibition of tyrosinase (TYR) expression in the B16-F10 melanoma cell line. Since 23R-AMA also inhibited microphthalmia-associated transcription factor (MITF) expression, an upstream factor of TYR, these features of 23R-AMA were thought to be appropriate for development of whitening cosmetics. However, 23R-AMA exhibited growth inhibition other than inhibition of melanin production in B16-F10 cells. Therefore, we investigated biological activities of 23R-AMA in detail, focused on its application as an anti-melanoma compound. In this study, we demonstrated that 23R-AMA inhibited cell proliferation and basic FGF (bFGF)-induced migration in B16-F10 cells. Furthermore, 23R-AMA promoted ser45/thr41 phosphorylation of β-catenin and suppressed its intranuclear accumulation, which was suggested to be related to inhibition of MITF expression. The transcriptional activity of MITF is known to be regulated by phosphorylation via activated ERK. Further investigation revealed that 23R-AMA inhibited phosphorylation of c-Raf, MEK-1, and ERK, and also that of upstream molecules including FAK and c-Src. These results suggested that 23R-AMA inhibited growth and migration of B16-F10 melanoma by regulating both MITF expression and its activity. The activities of 23R-AMA reported in this study are new aspects of cycloartane triterpenoids.

The function of FAK/CCDC80/E-cadherin pathway in the regulation of B16F10 cell migration

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase involved in the development and progression of cancer. However, the regulatory role of FAK in cell migration remains unclear. The aim of the present study was to investigate the mechanism underlying the regulation of melanoma cell migration by FAK. The effect of FAK knockdown on gene expression in B16F10 cells was examined by gene chip analysis. The expression levels of coiled-coil domain containing 80 (CCDC80) and epithelial (E)-cadherin were analyzed by reverse transcription quantitative polymerase chain reaction and western blotting. Wound healing and transwell assays were used to monitor B16F10 cell migration. It was identified that the knockdown of FAK increased the expression levels of CCDC80 and E-cadherin, while the overexpression of CCDC80 elevated E-cadherin expression. Concurrently, upregulation of CCDC80 inhibited the migration of B16F10 cells, and downregulation of CCDC80 promoted the migration of B16F10 cells. The clinical data from the Oncomine database also revealed that the mRNA level of FAK was increased while the mRNA levels of CCDC80 and E-cadherin were decreased in patients with melanoma compared with normal controls. Taken together, the results of the present study suggest that the regulation of B16F10 melanoma cell migration by FAK is potentially mediated by CCDC80.

Cell matrix adhesions in cancer: The proteins that form the glue

The main purposes of Integrin-mediated cell contacts are to interpret bi-directional signals between the extracellular environment and intracellular proteins, as well as, anchor the cell to a matrix. Many cell adhesion molecules have been discovered with a wide spectrum of responsibilities, including recruiting, activating, elongating, and maintaining. This review will perlustrate some of the key incidences that precede focal adhesion formation. Tyrosine phosphorylation is a key signaling initiation event that leads to the recruitment of multiple proteins to focal adhesion sites. Recruitment and concentration of proteins such as Paxillin and Vinculin to Integrin clutches is necessary for focal adhesion development. The assembled networks are responsible for transmitting signals back and forth from the extracellular matrix (ECM) to Actin and its binding proteins. Cancer cells exhibit highly altered focal adhesion dynamics. This review will highlight some key discoveries in cancer cell adhesion, as well as, identify current gaps in knowledge.

Overexpression of epidermal growth factor receptor and its downstream effector, focal adhesion kinase, correlates with papillary thyroid carcinoma progression

Epidermal growth factor receptor (EGFR) and its downstream effector, focal adhesion kinase (FAK), have been shown to be overexpressed frequently in human malignancies and implicated in tumour aggressiveness. We aimed to investigate the relationship between EGFR and FAK expression and their possible correlation with the clinical phenotype of patients with papillary thyroid carcinoma (PTC). Expression profiles of EGFR and FAK were analysed in PTC tissue samples (n = 104) by immunohistochemistry and Western blotting. Additionally, EGFR and FAK were immunohistochemically analysed in 20 primary tumours paired with their metastatic tissue in lymph nodes. High expression of EGFR and FAK was found in 55.77% and 57.69% cases, respectively, with a strong positive association between them (P < 0.0001, Spearman's correlation coefficient = 0.844). Expression of each molecule and their coexpression correlated significantly with the presence of lymph node metastasis (LNM), degree of tumour infiltration, extrathyroid invasion and pT status of the patients. Western blot analysis confirmed that coexpression of high levels of EGFR and FAK correlated with adverse clinicopathological features. When compared to the corresponding primary tumour, increased or maintained high levels of EGFR and FAK were found in LNM, indicating their concordant expression during lymphatic spread. In conclusion, high levels of EGFR and its downstream effector, FAK, in association with lymphatic spread and tumour infiltration indicate their involvement in PTC progression and suggest that both molecules may predict its aggressive behaviour. Furthermore, FAK could be a potential target for anticancer therapy in patients with advanced thyroid cancer.

Hyperalgesic priming (type II) induced by repeated opioid exposure: maintenance mechanisms

We previously developed a model of opioid-induced neuroplasticity in the peripheral terminal of the nociceptor that could contribute to opioid-induced hyperalgesia, type II hyperalgesic priming. Repeated administration of mu-opioid receptor (MOR) agonists, such as DAMGO, at the peripheral terminal of the nociceptor, induces long-lasting plasticity expressed, prototypically as opioid-induced hyperalgesia and prolongation of prostaglandin E2-induced hyperalgesia. In this study, we evaluated the mechanisms involved in the maintenance of type II priming. Opioid receptor antagonist, naloxone, induced hyperalgesia in DAMGO-primed paws. When repeatedly injected, naloxone-induced hyperalgesia, and hyperalgesic priming, supporting the suggestion that maintenance of priming involves changes in MOR signaling. However, the knockdown of MOR with oligodeoxynucleotide antisense did not reverse priming. Mitogen-activated protein kinase and focal adhesion kinase, which are involved in the Src signaling pathway, previously implicated in type II priming, also inhibited the expression, but not maintenance of priming. However, when Src and mitogen-activated protein kinase inhibitors were coadministered, type II priming was reversed, in male rats. A second model of priming, latent sensitization, induced by complete Freund's adjuvant was also reversed, in males. In females, the inhibitor combination was only able to inhibit the expression and maintenance of DAMGO-induced priming when knockdown of G-protein-coupled estrogen receptor 30 (GPR30) in the nociceptor was performed. These findings demonstrate that the maintenance of DAMGO-induced type II priming, and latent sensitization is mediated by an interaction between, Src and MAP kinases, which in females is GPR30 dependent.

Toxoplasma gondii disrupts β1 integrin signaling and focal adhesion formation during monocyte hypermotility

The motility of blood monocytes is orchestrated by the activity of cell-surface integrins, which translate extracellular signals into cytoskeletal changes to mediate adhesion and migration. Toxoplasma gondii is an intracellular parasite that infects migratory cells and enhances their motility, but the mechanisms underlying T. gondii-induced hypermotility are incompletely understood. We investigated the molecular basis for the hypermotility of primary human peripheral blood monocytes and THP-1 cells infected with T. gondii Compared with uninfected monocytes, T. gondii infection of monocytes reduced cell spreading and the number of activated β1 integrin clusters in contact with fibronectin during settling, an effect not observed in monocytes treated with lipopolysaccharide (LPS) or Escherichia coli Furthermore, T. gondii infection disrupted the phosphorylation of focal adhesion kinase (FAK) at tyrosine 397 (Tyr-397) and Tyr-925 and of the related protein proline-rich tyrosine kinase (Pyk2) at Tyr-402. The localization of paxillin, FAK, and vinculin to focal adhesions and the colocalization of these proteins with activated β1 integrins were also impaired in T. gondii-infected monocytes. Using time-lapse confocal microscopy of THP-1 cells expressing enhanced GFP (eGFP)-FAK during settling on fibronectin, we found that T. gondii-induced monocyte hypermotility was characterized by a reduced number of enhanced GFP-FAK-containing clusters over time compared with uninfected cells. This study demonstrates an integrin conformation-independent regulation of the β1 integrin adhesion pathway, providing further insight into the molecular mechanism of T. gondii-induced monocyte hypermotility.

Focal adhesion kinase promotes progression and predicts poor clinical outcomes in patients with osteosarcoma

Osteosarcoma (OS) is a fatal form of musculoskeletal tumor that commonly leads to pulmonary metastatic disease. Traditional therapies such as surgery and chemotherapy are not effective treatment modalities in certain patients with OS; therefore, identifying the molecular mechanism of OS is imperative for the development of novel therapeutics. Previous studies have reported that focal adhesion kinase (FAK) is associated with numerous types of human malignancies. Therefore, in order to investigate the biological function of FAK in OS, the present study examined the expression levels of FAK in OS cell lines, OS tissues and paired normal tissue specimens by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). FAK expression in vitro was blocked using small interfering RNA (siRNA) to observe the invasion, proliferation and apoptosis trends of OS cells. Phosphoinositide-dependent kinase-1 (PDK1), AKT and BRAF protein levels were also evaluated by western blotting to analyze the effects of FAK depletion on the AKT and mitogen-activated protein kinase (MAPK) signaling pathways. A significantly reduced level of FAK mRNA was identified in paired normal tissues compared with OS tissues and cell lines. The invasive capability and proliferative potential of OS cells were suppressed due to the transient in vitro transfection of FAK siRNA. It was also demonstrated that decreased FAK expression facilitated the apoptosis of OS cells, as demonstrated by flow cytometric and western blotting analyses. Decreased FAK expression resulted in the downregulation of phosphorylated (p)-AKT, p-PDK1 and p-BRAF protein levels. Higher FAK expression levels are positively associated with clinicopathological characteristics of advanced Enneking stages (P<0.001) and recurrence (P=0.041) in patients with OS. Collectively, these data demonstrated that FAK is an important diagnostic biomarker for OS, and FAK siRNA therapy may be a potentially promising approach for the treatment of OS.

Prognostic significance of c-Met, β-catenin and FAK in patients with hepatocellular carcinoma following surgery

The present study aimed to investigate the prognostic value of specific molecular markers in patients with hepatocellular carcinoma (HCC) who had received surgery. Immunohistochemical analysis was used to measure the expression of hepatocyte growth factor receptor (c-Met), β-catenin and focal adhesion kinase (FAK) in patients with HCC. c-Met expression was identified to be high in patients with larger tumors, higher α-fetoprotein (AFP) levels, higher Edmondson grades, portal vein invasion and higher tumor-node-metastasis (TNM) stages. FAK expression was high in patients with portal vein invasion, higher Edmondson grades and higher TNM stages. β-catenin expression was high in patients with larger tumors, hepatitis B virus (HBV) infection, portal vein invasion, higher Edmondson grades and higher TNM stages. Following multivariate analysis, FAK (P=0.002) and β-catenin (P=0.006) expression levels were demonstrated to be significantly associated with Edmondson grade. Additionally, the tumor size (P=0.009) and HBV infection status (P=0.002) were revealed to be associated with β-catenin expression. Kaplan-Meier survival curve analysis demonstrated that patients with HCC with higher FAK expression, higher β-catenin expression, portal vein invasion, higher Edmondson grades, higher TNM stages, younger ages and higher AFP levels had significantly poorer prognoses. Cox's regression analysis revealed that the survival period was correlated with the Edmondson grade, age, AFP level, and FAK and β-catenin expression. Univariate analysis of c-Met, β-catenin and FAK identified a significant correlation between FAK and β-catenin (P=0.015). Correlation analysis revealed no significant correlation between the three molecular markers, but β-catenin and c-Met were markedly correlated (P=0.052). No significant correlation between FAK, c-Met or β-catenin expression was identified. FAK and β-catenin expression demonstrated a correlation with a range of clinicopathological factors, and high FAK and β-catenin expression levels were identified to be correlated with a poor survival rate of patients with HCC. Thus, patients with higher FAK and β-catenin expression may require more aggressive therapy. The results of the present study suggest that FAK and β-catenin expression possess more prognostic value than c-Met expression in patients with HCC.