Conditional deletion of the focal adhesion kinase FAK alters remodeling of the blood-brain barrier in glioma

Targeting a key FAK-tor: the therapeutic potential of combining focal adhesion kinase (FAK) inhibitors and chemotherapy for chemoresistant non-small cell lung cancer

INTRODUCTION

NSCLC is the leading cause of cancer-related deaths globally, with a low survival rate primarily due to NSCLC frequently becoming chemoresistant. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase involved in pathways regulating multiple processes in the cell, including survival, migration, and the TME, that contribute to both tumor progression and drug resistance. Recently, FAK inhibitors (FAKi) have shown promising potential for the treatment of NSCLC.

AREAS COVERED

This narrative review aims to summarize key signaling pathways involving FAK that contribute to tumor progression and drug resistance. It will further provide an overview of FAKi currently in pre- and early-phase clinical trials for solid tumors, as well as the therapeutic potential of combining FAKi with chemotherapy, as this has emerged as a promising strategy to overcome chemoresistance in NSCLC.

EXPERT OPINION

It is becoming increasingly clear that FAK is not an oncogenic driver but rather contributes to tumor progression and drug resistance. Hence, while FAKi have only demonstrated modest results in clinical trials when given by themselves, treatment regimens combining other therapies with FAKi have shown promising potential to overcome drug resistance. Lastly, of particular novelty are FAK-PROTACs (proteolysis-targeting chimaeras), which uniquely target both cytosolic and nuclear FAK.

Mouse Models to Evaluate the Functional Role of the Tumor Microenvironment in Cancer Progression and Therapy Responses

The tumor microenvironment (TME) is a complex ecosystem of both cellular and noncellular components that functions to impact the evolution of cancer. Various aspects of the TME have been targeted for the control of cancer; however, TME composition is dynamic, with the overall abundance of immune cells, endothelial cells (ECs), fibroblasts, and extracellular matrix (ECM) as well as subsets of TME components changing at different stages of progression and in response to therapy. To effectively treat cancer, an understanding of the functional role of the TME is needed. Genetically engineered mouse models have enabled comprehensive insight into the complex interactions within the TME ecosystem that regulate disease progression. Here, we review recent advances in mouse models that have been employed to understand how the TME regulates cancer initiation, progression, metastasis, and response to therapy.

Prospects of focal adhesion kinase inhibitors as a cancer therapy in preclinical and early phase study

INTRODUCTION

FAK, a nonreceptor cytoplasmic tyrosine kinase, plays a crucial role in tumor metastasis, drug resistance, tumor stem cell maintenance, and regulation of the tumor microenvironment. FAK has emerged as a promising target for tumor therapy based on both preclinical and clinical data.

AREAS COVERED

This paper aims to summarize the molecular mechanisms underlying FAK's involvement in tumorigenesis and progression. Encouraging results have emerged from ongoing clinical trials of FAK inhibitors. Additionally, we present an overview of clinical trials for FAK inhibitors, examining their potential as promising treatments. The pertinent studies gathered from databases including PubMed, ClinicalTrials.gov.

EXPERT OPINION

Since the first finding in 1990s, targeting FAK has became the focus of interests in many pharmaceutical companies. Through 30 years' discovery, the industry and academy gradually realized the features of FAK target which may not be a driver gene but a solid defense system for the cancer initiation and development. Currently, the ongoing clinical regimens involving FAK inhibition are all the combination strategies in which FAK inhibitors can further strengthen the cancer cell killing effects of other testing agents. The emerging positive signal in clinical trials foresee targeting FAK as class will be an effective mean to fight against cancers.

PYK2, a hub of signaling networks in breast cancer progression

Breast cancer (BC) involves complex signaling networks characterized by extensive cross-communication and feedback loops between and within multiple signaling cascades. Many of these signaling pathways are driven by genetic alterations of oncogene and/or tumor-suppressor genes and are influenced by various environmental cues. We describe unique roles of the non-receptor tyrosine kinase (NRTK) PYK2 in signaling integration and feedback looping in BC. PYK2 functions as a signaling hub in various cascades, and its involvement in positive and negative feedback loops enhances signaling robustness, modulates signaling dynamics, and contributes to BC growth, epithelial-to-mesenchymal transition (EMT), stemness, migration, invasion, and metastasis. We also discuss the potential of PYK2 as a therapeutic target in various BC subtypes.

Conditional expression of endorepellin in the tumor vasculature attenuates breast cancer growth, angiogenesis and hyaluronan deposition

The tumor stroma of most solid malignancies is characterized by a pathological accumulation of pro-angiogenic and pro-tumorigenic hyaluronan driving tumorigenesis and metastatic potential. Of all three hyaluronan synthase isoforms, HAS2 is the primary enzyme that promotes the build-up of tumorigenic HA in breast cancer. Previously, we discovered that endorepellin, the angiostatic C-terminal fragment of perlecan, evokes a catabolic mechanism targeting endothelial HAS2 and hyaluronan via autophagic induction. To explore the translational implications of endorepellin in breast cancer, we created a double transgenic, inducible Tie2CreERT2;endorepellin(ER)Ki mouse line that expresses recombinant endorepellin specifically from the endothelium. We investigated the therapeutic effects of recombinant endorepellin overexpression in an orthotopic, syngeneic breast cancer allograft mouse model. First, adenoviral delivery of Cre evoking intratumor expression of endorepellin in ERKi mice suppressed breast cancer growth, peritumor hyaluronan and angiogenesis. Moreover, tamoxifen-induced expression of recombinant endorepellin specifically from the endothelium in Tie2CreERT2;ERKi mice markedly suppressed breast cancer allograft growth, hyaluronan deposition in the tumor proper and perivascular tissues, and tumor angiogenesis. These results provide insight into the tumor suppressing activity of endorepellin at the molecular level and implicate endorepellin as a promising cancer protein therapy that targets hyaluronan in the tumor microenvironment.

Cancer-associated fibroblasts: Versatile mediators in remodeling the tumor microenvironment

Current cancer therapeutic strategies are generally not sufficient to eradicate malignancy, as cancer stroma cells contribute to tumor evasion and therapeutic resistance. Cancer-associated fibroblasts (CAFs) constitute a largely heterogeneous type of stromal cell population and are important components of the tumor microenvironment (TME). CAFs are the most abundant stromal cell type and are actively involved in tumor progression through complex mechanisms involving effects on other cell types. Research conducted in recent years has emphasized an emerging function of CAFs in the remodeling of the TME that promotes tumor progression with effects on response to treatment by various molecular mechanisms. A comprehensive mechanism of tumor-promoting activities of CAFs could facilitate the development of novel diagnostic and therapeutic approaches. In this review, the biological characterization of CAFs and the mechanisms of their effects on TME remodeling are summarized. Furthermore, we also highlight currently available therapeutic strategies targeting CAF in the context of optimizing the success of immunotherapies and briefly discuss possible future perspectives and challenges related to CAF studies.

Functional and clinical characteristics of focal adhesion kinases in cancer progression

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase and an adaptor protein that primarily regulates adhesion signaling and cell migration. FAK promotes cell survival in response to stress. Increasing evidence has shown that at the pathological level, FAK is highly expressed in multiple tumors in several systems (including lung, liver, gastric, and colorectal cancers) and correlates with tumor aggressiveness and patient prognosis. At the molecular level, FAK promotes tumor progression mainly by altering survival signals, invasive capacity, epithelial-mesenchymal transition, the tumor microenvironment, the Warburg effect, and stemness of tumor cells. Many effective drugs have been developed based on the comprehensive role of FAK in tumor cells. In addition, its potential as a tumor marker cannot be ignored. Here, we discuss the pathological and pre-clinical evidence of the role of FAK in cancer development; we hope that these findings will assist in FAK-based clinical studies.

Plasmodium falciparum and TNF-α Differentially Regulate Inflammatory and Barrier Integrity Pathways in Human Brain Endothelial Cells

Cerebral malaria is a severe complication of Plasmodium falciparum infection characterized by the loss of blood-brain barrier (BBB) integrity, which is associated with brain swelling and mortality in patients. P. falciparum-infected red blood cells and inflammatory cytokines, like tumor necrosis factor alpha (TNF-α), have been implicated in the development of cerebral malaria, but it is still unclear how they contribute to the loss of BBB integrity. Here, a combination of transcriptomic analysis and cellular assays detecting changes in barrier integrity and endothelial activation were used to distinguish between the effects of P. falciparum and TNF-α on a human brain microvascular endothelial cell (HBMEC) line and in primary human brain microvascular endothelial cells. We observed that while TNF-α induced high levels of endothelial activation, it only caused a small increase in HBMEC permeability. Conversely, P. falciparum-infected red blood cells (iRBCs) led to a strong increase in HBMEC permeability that was not mediated by cell death. Distinct transcriptomic profiles of TNF-α and P. falciparum in HBMECs confirm the differential effects of these stimuli, with the parasite preferentially inducing an endoplasmic reticulum stress response. Our results establish that there are fundamental differences in the responses induced by TNF-α and P. falciparum on brain endothelial cells and suggest that parasite-induced signaling is a major component driving the disruption of the BBB during cerebral malaria, proposing a potential target for much needed therapeutics.

Elucidating the role of the kinase activity of endothelial cell focal adhesion kinase in angiocrine signalling and tumour growth

A common limitation of cancer treatments is chemotherapy resistance. We have previously identified that endothelial cell (EC)-specific deletion of focal adhesion kinase (FAK) sensitises tumour cells to DNA-damaging therapies, reducing tumour growth in mice. The present study addressed the kinase activity dependency of EC FAK sensitisation to the DNA-damaging chemotherapeutic drug, doxorubicin. FAK is recognised as a therapeutic target in tumour cells, leading to the development of a range of inhibitors, the majority being ATP competitive kinase inhibitors. We demonstrate that inactivation of EC FAK kinase domain (kinase dead; EC FAK-KD) in established subcutaneous B16F0 tumours improves melanoma cell sensitisation to doxorubicin. Doxorubicin treatment in EC FAK-KD mice reduced the percentage change in exponential B16F0 tumour growth further than in wild-type mice. There was no difference in tumour blood vessel numbers, vessel perfusion or doxorubicin delivery between genotypes, suggesting a possible angiocrine effect on the regulation of tumour growth. Doxorubicin reduced perivascular malignant cell proliferation, while enhancing perivascular tumour cell apoptosis and DNA damage in tumours grown in EC FAK-KD mice 48 h after doxorubicin injection. Human pulmonary microvascular ECs treated with the pharmacological FAK kinase inhibitors defactinib, PF-562,271 or PF-573,228 in combination with doxorubicin also reduced cytokine expression levels. Together, these data suggest that targeting EC FAK kinase activity may alter angiocrine signals that correlate with improved acute tumour cell chemosensitisation. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Blood-brain barrier-restricted translocation of Toxoplasma gondii from cortical capillaries

The cellular barriers of the central nervous system proficiently protect the brain parenchyma from infectious insults. Yet, the single-celled parasite Toxoplasma gondii commonly causes latent cerebral infection in humans and other vertebrates. Here, we addressed the role of the cerebral vasculature in the passage of T. gondii to the brain parenchyma. Shortly after inoculation in mice, parasites mainly localized to cortical capillaries, in preference over post-capillary venules, cortical arterioles or meningeal and choroidal vessels. Early invasion to the parenchyma (days 1-5) occurred in absence of a measurable increase in blood-brain barrier (BBB) permeability, perivascular leukocyte cuffs or hemorrhage. However, sparse focalized permeability elevations were detected adjacently to replicative parasite foci. Further, T. gondii triggered inflammatory responses in cortical microvessels and endothelium. Pro- and anti-inflammatory treatments of mice with LPS and hydrocortisone, respectively, impacted BBB permeability and parasite loads in the brain parenchyma. Finally, pharmacological inhibition or Cre/loxP conditional knockout of endothelial focal adhesion kinase (FAK), a BBB intercellular junction regulator, facilitated parasite translocation to the brain parenchyma. The data reveal that the initial passage of T. gondii to the central nervous system occurs principally across cortical capillaries. The integrity of the microvascular BBB restricts parasite transit, which conversely is exacerbated by the inflammatory response.

Phosphorylation of pericyte FAK-Y861 affects tumour cell apoptosis and tumour blood vessel regression

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that is overexpressed in many cancer types and in vivo studies have shown that vascular endothelial cell FAK expression and FAK-phosphorylation at tyrosine (Y) 397, and subsequently FAK-Y861, are important in tumour angiogenesis. Pericytes also play a vital role in regulating tumour blood vessel stabilisation, but the specific involvement of pericyte FAK-Y397 and FAK-Y861 phosphorylation in tumour blood vessels is unknown. Using PdgfrβCre + ;FAKWT/WT, PdgfrβCre + ;FAKY397F/Y397F and PdgfrβCre + ;FAKY861F/Y861F mice, our data demonstrate that Lewis lung carcinoma tumour growth, tumour blood vessel density, blood vessel perfusion and pericyte coverage were affected only in late stage tumours in PdgfrβCre + ;FAKY861F/Y861F but not PdgfrβCre + ;FAKY397F/Y397F mice. Further examination indicates a dual role for pericyte FAK-Y861 phosphorylation in the regulation of tumour vessel regression and also in the control of pericyte derived signals that influence apoptosis in cancer cells. Overall this study identifies the role of pericyte FAK-Y861 in the regulation of tumour vessel regression and tumour growth control and that non-phosphorylatable FAK-Y861F in pericytes reduces tumour growth and blood vessel density.

The Adhesome Network: Key Components Shaping the Tumour Stroma

Beyond the conventional perception of solid tumours as mere masses of cancer cells, advanced cancer research focuses on the complex contributions of tumour-associated host cells that are known as "tumour microenvironment" (TME). It has been long appreciated that the tumour stroma, composed mainly of blood vessels, cancer-associated fibroblasts and immune cells, together with the extracellular matrix (ECM), define the tumour architecture and influence cancer cell properties. Besides soluble cues, that mediate the crosstalk between tumour and stroma cells, cell adhesion to ECM arises as a crucial determinant in cancer progression. In this review, we discuss how adhesome, the intracellular protein network formed at cell adhesions, regulate the TME and control malignancy. The role of adhesome extends beyond the physical attachment of cells to ECM and the regulation of cytoskeletal remodelling and acts as a signalling and mechanosensing hub, orchestrating cellular responses that shape the tumour milieu.

Association of Low Tumor Endothelial Cell pY397-Focal Adhesion Kinase Expression With Survival in Patients With Neoadjuvant-Treated Locally Advanced Breast Cancer

IMPORTANCE

Determining the risk of relapse after neoadjuvant chemotherapy in patients with locally advanced breast cancer is required to offer alternative therapeutic strategies.

OBJECTIVE

To examine whether endothelial cell phosphorylated-focal adhesion kinase (EC-pY397-FAK) expression in patients with treatment-naive locally advanced breast cancer is a biomarker for chemotherapy sensitivity and is associated with survival after neoadjuvant chemotherapy.

DESIGN, SETTING, AND PARTICIPANTS

In this prognostic study, expression levels of EC-pY397-FAK and tumor cell (TC)-pY397-FAK were determined by immunohistochemistry in prechemotherapy core biopsies from 82 female patients with locally advanced breast cancer treated with anthracycline-based combination neoadjuvant chemotherapy at Nottingham City Hospital in Nottingham, UK. Median follow-up time was 67 months. The study was conducted from December 1, 2010, to September 28, 2019, and data analysis was performed from October 2, 2019, to March 31, 2020.

EXPOSURES

All women underwent surgery followed by adjuvant radiotherapy and, if tumors were estrogen receptor-positive, 5-year tamoxifen treatment.

MAIN OUTCOMES AND MEASURES

Outcomes were pathologic complete response and 5-year relapse-free survival examined using Kaplan-Meier, univariable logistic, multivariable logistic, and Cox proportional hazards models.

RESULTS

A total of 82 women (age, 29-76 years) with locally advanced breast cancer (stage IIA-IIIC) were included. Of these, 21 women (26%) had high EC-pY397-FAK expression that was associated with estrogen receptor positivity (71% vs 46%; P = .04), progesterone receptor positivity (67% vs 39%; P = .03), high Ki67 (86% vs 41%; P < .001), 4-immunohistochemically stained luminal-B (52% vs 8%; P < .001), higher tumor category (T3/T4 category: 90% vs 59%; P = .01), high lymph node category (N2-3 category: 43% vs 5%; P < .001), and high tumor node metastasis stage (IIIA-IIIC: 90% vs 66%; P = .03). Of 21 patients with high EC-pY397-FAK expression levels, none showed pathologic complete response, compared with 11 of 61 patients with low EC-pY397-FAK expression levels who showed pathologic complete response (odds ratio, 0.70; 95% CI, 0.61-0.82; P = .04). High EC-pY397-FAK expression levels and high blood vessel density (BVD) were associated with shorter 5-year relapse-free survival compared with those with low EC-pY397-FAK expression levels (hazard ratio [HR], 2.21; 95% CI, 1.17-4.20; P = .01) and low BVD (HR, 2.2; 95% CI, 1.15-4.35; P = .02). High TC-pY397-FAK expression levels in 15 of 82 women (18%) were not associated significantly with pathologic complete response or 5-year relapse-free survival. A multivariable Cox regression model for 5-year relapse-free survival indicated that high EC-pY397-FAK expression levels was an independent poor prognostic factor after controlling for other validated prognostic factors (HR, 3.91; 95% CI, 1.42-10.74; P = .01). Combined analysis of EC-pY397-FAK expression levels, TC-pY397-FAK expression levels, and BVD improved prognostic significance over individually tested features.

CONCLUSIONS AND RELEVANCE

The findings of this study suggest that low EC-pY397-FAK expression levels are associated with chemotherapy sensitivity and improved 5-year relapse-free survival after systemic therapy. Combined analysis of high EC-pY397-FAK expression levels, high TC-pY397-FAK expression levels, and high BVD appeared to identify a high-risk population.

Targeting focal adhesion kinase in cancer cells and the tumor microenvironment

Focal adhesion kinase (FAK) is an integrin-associated protein tyrosine kinase that is frequently overexpressed in advanced human cancers. Recent studies have demonstrated that aside from FAK's catalytic activity in cancer cells, its cellular localization is also critical for regulating the transcription of chemokines that promote a favorable tumor microenvironment (TME) by suppressing destructive host immunity. In addition to the protumor roles of FAK in cancer cells, FAK activity within cells of the TME may also support tumor growth and metastasis through various mechanisms, including increased angiogenesis and vascular permeability and effects related to fibrosis in the stroma. Small molecule FAK inhibitors have demonstrated efficacy in alleviating tumor growth and metastasis, and some are currently in clinical development phases. However, several preclinical trials have shown increased benefits from dual therapies using FAK inhibitors in combination with other chemotherapies or with immune cell activators. This review will discuss the role of nuclear FAK as a driver for tumor cell survival as well as potential therapeutic strategies to target FAK in both tumors and the TME.

Pericyte FAK negatively regulates Gas6/Axl signalling to suppress tumour angiogenesis and tumour growth

The overexpression of the protein tyrosine kinase, Focal adhesion kinase (FAK), in endothelial cells has implicated its requirement in angiogenesis and tumour growth, but how pericyte FAK regulates tumour angiogenesis is unknown. We show that pericyte FAK regulates tumour growth and angiogenesis in multiple mouse models of melanoma, lung carcinoma and pancreatic B-cell insulinoma and provide evidence that loss of pericyte FAK enhances Gas6-stimulated phosphorylation of the receptor tyrosine kinase, Axl with an upregulation of Cyr61, driving enhanced tumour growth. We further show that pericyte derived Cyr61 instructs tumour cells to elevate expression of the proangiogenic/protumourigenic transmembrane receptor Tissue Factor. Finally, in human melanoma we show that when 50% or more tumour blood vessels are pericyte-FAK negative, melanoma patients are stratified into those with increased tumour size, enhanced blood vessel density and metastasis. Overall our data uncover a previously unknown mechanism of tumour growth by pericytes that is controlled by pericyte FAK.

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.

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.

Functional suppression of Epiregulin impairs angiogenesis and aggravates left ventricular remodeling by disrupting the extracellular-signal-regulated kinase1/2 signaling pathway in rats after acute myocardial infarction

Acute myocardial infarction (AMI), a severe consequence of coronary atherosclerotic heart disease, is often associated with high mortality and morbidity. Emerging evidence have shown that the inhibition of the extracellular-signal-regulated kinase (ERK) signaling pathway appears to protect against AMI. Epiregulin (EREG) is an autocrine growth factor that is believed to activate the MEK/ERK signaling pathway. Therefore, the aim of the present study was to determine the expression patterns of EREG in AMI and to further study its effects on AMI induced experimentally in rats focusing on angiogenesis and left ventricular remodeling. Microarray-based gene expression profiling of AMI was used to identify differentially expressed genes. To understand the biological significance of EREG and whether it is involved in AMI disease through the ERK1/2 signaling pathway, rats after AMI were treated with small interfering RNA (siRNA) against EREG, an ERK1/2 pathway inhibitor, PD98059, or both of them. The microarray data sets GSE66360 and GSE46395 showed that EREG was robustly induced in AMI. Both siRNA-mediated depletion of EREG and PD98059 treatment were shown to significantly increase infarct size and left ventricular cardiomyocyte loss and enhance left ventricular remodeling. In addition, we also found that the ERK1/2 signaling pathway was inhibited following siRNA-mediated EREG inhibition and PD98059 could enhance the effects of EREG inhibition on AMI. In conclusion, these findings highlight that the silencing of EREG inhibits angiogenesis and promotes left ventricular remodeling by disrupting the ERK1/2 signaling pathway, providing a novel therapeutic target for limiting AMI.

Angiopoietin-2 exacerbates cardiac hypoxia and inflammation after myocardial infarction

Emerging evidence indicates that angiopoietin-2 (Angpt2), a well-recognized vascular destabilizing factor, is a biomarker of poor outcome in ischemic heart disease. However, its precise role in postischemic cardiovascular remodeling is poorly understood. Here, we show that Angpt2 plays multifaceted roles in the exacerbation of cardiac hypoxia and inflammation after myocardial ischemia. Angpt2 was highly expressed in endothelial cells at the infarct border zone after myocardial infarction (MI) or ischemia/reperfusion injury in mice. In the acute phase of MI, endothelial-derived Angpt2 antagonized Angpt1/Tie2 signaling, which was greatly involved in pericyte detachment, vascular leakage, increased adhesion molecular expression, degradation of the glycocalyx and extracellular matrix, and enhanced neutrophil infiltration and hypoxia in the infarct border area. In the chronic remodeling phase after MI, endothelial- and macrophage-derived Angpt2 continuously promoted abnormal vascular remodeling and proinflammatory macrophage polarization through integrin α5β1 signaling, worsening cardiac hypoxia and inflammation. Accordingly, inhibition of Angpt2 either by gene deletion or using an anti-Angpt2 blocking antibody substantially alleviated these pathological findings and ameliorated postischemic cardiovascular remodeling. Blockade of Angpt2 thus has potential as a therapeutic option for ischemic heart failure.

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.

Protein Interactions at Endothelial Junctions and Signaling Mechanisms Regulating Endothelial Permeability

The monolayer of endothelial cells lining the vessel wall forms a semipermeable barrier (in all tissue except the relatively impermeable blood-brain and inner retinal barriers) that regulates tissue-fluid homeostasis, transport of nutrients, and migration of blood cells across the barrier. Permeability of the endothelial barrier is primarily regulated by a protein complex called adherens junctions. Adherens junctions are not static structures; they are continuously remodeled in response to mechanical and chemical cues in both physiological and pathological settings. Here, we discuss recent insights into the post-translational modifications of junctional proteins and signaling pathways regulating plasticity of adherens junctions and endothelial permeability. We also discuss in the context of what is already known and newly defined signaling pathways that mediate endothelial barrier leakiness (hyperpermeability) that are important in the pathogenesis of cardiovascular and lung diseases and vascular inflammation.

A dynamic in vivo-like organotypic blood-brain barrier model to probe metastatic brain tumors

The blood-brain barrier (BBB) restricts the uptake of many neuro-therapeutic molecules, presenting a formidable hurdle to drug development in brain diseases. We proposed a new and dynamic in vivo-like three-dimensional microfluidic system that replicates the key structural, functional and mechanical properties of the blood-brain barrier in vivo. Multiple factors in this system work synergistically to accentuate BBB-specific attributes-permitting the analysis of complex organ-level responses in both normal and pathological microenvironments in brain tumors. The complex BBB microenvironment is reproduced in this system via physical cell-cell interaction, vascular mechanical cues and cell migration. This model possesses the unique capability to examine brain metastasis of human lung, breast and melanoma cells and their therapeutic responses to chemotherapy. The results suggest that the interactions between cancer cells and astrocytes in BBB microenvironment might affect the ability of malignant brain tumors to traverse between brain and vascular compartments. Furthermore, quantification of spatially resolved barrier functions exists within a single assay, providing a versatile and valuable platform for pharmaceutical development, drug testing and neuroscientific research.

Molecular Pathways: Endothelial Cell FAK-A Target for Cancer Treatment

The nonreceptor protein tyrosine kinase, focal adhesion kinase (FAK, also known as PTK2), is a key mediator of signal transduction downstream of integrins and growth factor receptors in a variety of cells, including endothelial cells. FAK is upregulated in several advanced-stage solid tumors and has been described to promote tumor progression and metastasis through effects on both tumor cells and stromal cells. This observation has led to the development of several FAK inhibitors, some of which have entered clinical trials (GSK2256098, VS-4718, VS-6062, VS-6063, and BI853520). Resistance to chemotherapy is a serious limitation of cancer treatment and, until recently, most studies were restricted to tumor cells, excluding the possible roles performed by the tumor microenvironment. A recent report identified endothelial cell FAK (EC-FAK) as a major regulator of chemosensitivity. By dysregulating endothelial cell-derived paracrine (also known as angiocrine) signals, loss of FAK solely in the endothelial cell compartment is able to induce chemosensitization to DNA-damaging therapies in the malignant cell compartment and thereby reduce tumor growth. Herein, we summarize the roles of EC-FAK in cancer and development and review the status of FAK-targeting anticancer strategies. Clin Cancer Res; 22(15); 3718-24. ©2016 AACR.

Naringin suppresses the development of glioblastoma by inhibiting FAK activity

As the most common and lethal primary malignant brain cancer, glioblastoma is hard to timely diagnose and sensitive therapeutic monitoring. It is essential to develop new and effective drugs for glioblastoma multiform. Naringin belongs to citrus flavonoids and was found to display strong anti-inflammatory, antioxidant and antitumor activities. In this report, we found that naringin can specifically inhibit the kinase activity of FAK and suppress the FAK^p-Try397and its downstream pathway in glioblastoma cells. Our study showed out that naringin can inhibit cell proliferation by inhibiting FAK/cyclin D1 pathway, promote cell apoptosis through influencing FAK/bads pathway, at the same time, it can also inhibit cell invasion and metastasis by inhibiting the FAK/mmps pathway. All these showed that naringin exerts the anti-tumor effects in U87 MG by inhibiting the kinase activity of FAK.

The Src non-receptor tyrosine kinase paradigm: New insights into mammalian Sertoli cell biology

Src kinases are non-receptor tyrosine kinases that phosphorylate diverse substrates, which control processes such as cell proliferation, differentiation and survival; cell adhesion; and cell motility. c-Src, the prototypical member of this protein family, is widely expressed by several organs that include the testis. In the seminiferous epithelium of the adult rat testis, c-Src is highest at the tubule lumen during the release of mature spermatids. Other studies show that testosterone regulates spermatid adhesion to Sertoli cells via c-Src, indicating Src phosphorylates key substrates that prompt the disassembly of Sertoli cell-spermatid junctions. A more recent in vitro study reveals that c-Src participates in the internalization of proteins that constitute the blood-testis barrier, which is present between Sertoli cells, suggesting a similar mechanism of junction disassembly is at play during spermiation. In this review, we discuss recent findings on c-Src, with an emphasis on its role in spermatogenesis in the mammalian testis.

FAK is required for c-Met/β-catenin-driven hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is the third most common cause of cancer death worldwide and most patients with HCC have limited treatment options. Focal adhesion kinase (FAK) is overexpressed in many HCC specimens, offering a potential target for HCC treatment. However, the role of FAK in hepatocarcinogenesis remains elusive. Establishing whether FAK expression plays a role in HCC development is necessary to determine whether it is a viable therapeutic target. In this study, we generated mice with hepatocyte-specific deletion of Fak and investigated the role of Fak in an oncogenic (c-MET/β-catenin, MET/CAT)-driven HCC model. We found that deletion of Fak in hepatocytes did not affect morphology, proliferation, or apoptosis. However, Fak deficiency significantly repressed MET/CAT-induced tumor development and prolonged survival of animals with MET/CAT-induced HCC. In mouse livers and HCC cell lines, Fak was activated by MET, which induced the activation of Akt/Erk and up-regulated cyclin D1 and tumor cell proliferation. CAT enhanced MET-stimulated FAK activation and synergistically induced the activation of the AKT/ERK-cyclin D1 signaling pathway in a FAK kinase-dependent manner. In addition, FAK was required for CAT-induced cyclin D1 expression in a kinase-independent fashion.

CONCLUSION

Fak is required for c-Met/β-catenin-driven hepatocarcinogenesis. Inhibition of FAK provides a potential strategy to treat HCC.

Thrombin-processed Ecrg4 recruits myeloid cells and induces antitumorigenic inflammation

BACKGROUND

Extensive infiltration of brain tumors by microglia and macrophages is a hallmark of tumor progression, and yet the overall tumor microenvironment is characterized by an immunosuppressive phenotype. Here we identify esophageal cancer-related gene 4 (Ecrg4) as a novel thrombin-processed monocyte chemoattractant that recruits myeloid cells, promotes their activation, and leads to a blockade of tumor progression.

METHODS

Both xenograft glioma and syngeneic glioma models were used to measure orthotopic tumor progression and overall survival. Flow cytometry and immunohistochemical analyses were performed to assess myeloid cell localization, recruitment, and activation.

RESULTS

Ecrg4 promotes monocyte recruitment and activation of microglia in a T-/B-cell-independent mechanism, which leads to a reduction in glioma tumor burden and increased survival. Mutational analysis reveals that the biological activity of Ecrg4 is dependent on a thrombin-processing site at the C-terminus, inducing monocyte invasion in vivo and in vitro. Furthermore, tumor-induced myeloid cell recruitment is impaired in Ecrg4 knockout mice, leading to increased tumor burden and decreased survival.

CONCLUSIONS

Together, these results identify Ecrg4 as a paracrine factor that activates microglia and is chemotactic for monocytes, with potential as an antitumor therapeutic.

Vascular normalization in cerebral angiogenesis: friend or foe?

Current antiangiogenic therapies have led to the observation that such agents can lead to improved tumor vessel structure and function termed "vascular normalization" which reduces tumor burden. However, vessel normalization is a transient process, and patients often develop resistance/poor response to anti-vascular strategies that remains an important clinical challenge. Therefore, increasing effort has been made to better understand the cellular and molecular mechanisms of vascular normalization and its contribution to immunomodulation. Herein, we summarize the recent effort to better understand the cellular and molecular mechanisms of vascular normalization with a focus on preclinical genetic models. These studies remain important directions for a mechanistic understanding of the complexities of the maintenance of BBB integrity and the impact of its breakdown on tumor dissemination and pharmaco-distribution of therapeutics.

FAK in cancer: mechanistic findings and clinical applications

Focal adhesion kinase (FAK) is a cytoplasmic protein tyrosine kinase that is overexpressed and activated in several advanced-stage solid cancers. FAK promotes tumour progression and metastasis through effects on cancer cells, as well as stromal cells of the tumour microenvironment. The kinase-dependent and kinase-independent functions of FAK control cell movement, invasion, survival, gene expression and cancer stem cell self-renewal. Small molecule FAK inhibitors decrease tumour growth and metastasis in several preclinical models and have initial clinical activity in patients with limited adverse events. In this Review, we discuss FAK signalling effects on both tumour and stromal cell biology that provide rationale and support for future therapeutic opportunities.

Inhibition of endothelial FAK activity prevents tumor metastasis by enhancing barrier function

Endothelial cell focal adhesion kinase is a key intermediate between c-Src and the regulation of endothelial cell barrier function in the control of tumor metastasis.

Pharmacological focal adhesion kinase (FAK) inhibition prevents tumor growth and metastasis, via actions on both tumor and stromal cells. In this paper, we show that vascular endothelial cadherin (VEC) tyrosine (Y) 658 is a target of FAK in tumor-associated endothelial cells (ECs). Conditional kinase-dead FAK knockin within ECs inhibited recombinant vascular endothelial growth factor (VEGF-A) and tumor-induced VEC-Y658 phosphorylation in vivo. Adherence of VEGF-expressing tumor cells to ECs triggered FAK-dependent VEC-Y658 phosphorylation. Both FAK inhibition and VEC-Y658F mutation within ECs prevented VEGF-initiated paracellular permeability and tumor cell transmigration across EC barriers. In mice, EC FAK inhibition prevented VEGF-dependent tumor cell extravasation and melanoma dermal to lung metastasis without affecting primary tumor growth. As pharmacological c-Src or FAK inhibition prevents VEGF-stimulated c-Src and FAK translocation to EC adherens junctions, but FAK inhibition does not alter c-Src activation, our experiments identify EC FAK as a key intermediate between c-Src and the regulation of EC barrier function controlling tumor metastasis.

Hitting Them Where They Live: Targeting the Glioblastoma Perivascular Stem Cell Niche

Glioblastoma growth potential and resistance to therapy is currently largely attributed to a subset of tumor cells with stem-like properties. If correct, this means that cure will not be possible without eradication of the stem cell fraction and abrogation of those mechanisms through which stem cell activity is induced and maintained. Glioblastoma stem cell functions appear to be non-cell autonomous and the consequence of tumor cell residence within specialized domains such as the perivascular stem cell niche. In this review we consider the multiple cellular constituents of the perivascular niche, the molecular mechanisms that support niche structure and function and the implications of the perivascular localization of stem cells for anti-angiogenic approaches to cure.

VEGFA and tumour angiogenesis

In this review we summarize the current understanding of signal transduction downstream of vascular endothelial growth factor A (VEGFA) and its receptor VEGFR2, and the relationship between these signal transduction pathways and the hallmark responses of VEGFA, angiogenesis and vascular permeability. These physiological responses involve a number of effectors, including extracellular signal-regulated kinases (ERKs), Src, phosphoinositide 3 kinase (PI3K)/Akt, focal adhesion kinase (FAK), Rho family GTPases, endothelial NO and p38 mitogen-activated protein kinase (MAPK). Several of these factors are involved in the regulation of both angiogenesis and vascular permeability. Tumour angiogenesis primarily relies on VEGFA-driven responses, which to a large extent result in a dysfunctional vasculature. The reason for this remains unclear, although it appears that certain aspects of the VEGFA-stimulated angiogenic milieu (high level of microvascular density and permeability) promote tumour expansion. The high degree of redundancy and complexity of VEGFA-driven tumour angiogenesis may explain why tumours commonly develop resistance to anti-angiogenic therapy targeting VEGFA signal transduction.

Pharmacologic blockade of FAK autophosphorylation decreases human glioblastoma tumor growth and synergizes with temozolomide

Malignant gliomas are characterized by aggressive tumor growth with a mean survival of 15 to 18 months and frequently developed resistance to temozolomide. Therefore, strategies that sensitize glioma cells to temozolomide have a high translational impact. We have studied focal adhesion kinase (FAK), a tyrosine kinase and emerging therapeutic target that is known to be highly expressed and activated in glioma. In this report, we tested the FAK autophosphorylation inhibitor, Y15, in DBTRG and U87 glioblastoma cells. Y15 significantly decreased viability and clonogenicity in a dose-dependent manner, increased detachment in a dose- and time-dependent manner, caused apoptosis, and inhibited cell invasion in both cell lines. In addition, Y15 treatment decreased autophosphorylation of FAK in a dose-dependent manner and changed cell morphology by causing cell rounding in DBTRG and U87 cells. Administration of Y15 significantly decreased subcutaneous DBTRG tumor growth with decreased Y397-FAK autophosphorylation, activated caspase-3 and PARP. Y15 was administered in an orthotopic glioma model, leading to an increase in mouse survival. The combination of Y15 with temozolomide was more effective than either agent alone in decreasing viability and activating caspase-8 in DBTRG and U87 cells in vitro. In addition, the combination of Y15 and temozolomide synergistically blocked U87 brain tumor growth in vivo. Thus, pharmacologic blockade of FAK autophosphorylation with the oral administration of a small-molecule inhibitor Y15 has a potential to be an effective therapy approach for glioblastoma either alone or in combination with chemotherapy agents such as temozolomide.

Magnetic targeting of nanoparticles across the intact blood-brain barrier

Delivery of therapeutic or diagnostic agents across an intact blood-brain barrier (BBB) remains a major challenge. Here we demonstrate in a mouse model that magnetic nanoparticles (MNPs) can cross the normal BBB when subjected to an external magnetic field. Following a systemic administration, an applied external magnetic field mediates the ability of MNPs to permeate the BBB and accumulate in a perivascular zone of the brain parenchyma. Direct tracking and localization inside endothelial cells and in the perivascular extracellular matrix in vivo was established using fluorescent MNPs. These MNPs were inert and associated with low toxicity, using a non-invasive reporter for astrogliosis, biochemical and histological studies. Atomic force microscopy demonstrated that MNPs were internalized by endothelial cells, suggesting that trans-cellular trafficking may be a mechanism for the MNP crossing of the BBB observed. The silica-coated magnetic nanocapsules (SiMNCs) allow on-demand drug release via remote radio frequency (RF) magnetic field. Together, these results establish an effective strategy for regulating the biodistribution of MNPs in the brain through the application of an external magnetic field.

Nuclear-localized focal adhesion kinase regulates inflammatory VCAM-1 expression

Kinase-inhibited FAK limits VCAM-1 production via nuclear localization and promotion of GATA4 turnover.

Vascular cell adhesion molecule–1 (VCAM-1) plays important roles in development and inflammation. Tumor necrosis factor–α (TNF-α) and focal adhesion kinase (FAK) are key regulators of inflammatory and integrin–matrix signaling, respectively. Integrin costimulatory signals modulate inflammatory gene expression, but the important control points between these pathways remain unresolved. We report that pharmacological FAK inhibition prevented TNF-α–induced VCAM-1 expression within heart vessel–associated endothelial cells in vivo, and genetic or pharmacological FAK inhibition blocked VCAM-1 expression during development. FAK signaling facilitated TNF-α–induced, mitogen-activated protein kinase activation, and, surprisingly, FAK inhibition resulted in the loss of the GATA4 transcription factor required for TNF-α–induced VCAM-1 production. FAK inhibition also triggered FAK nuclear localization. In the nucleus, the FAK-FERM (band 4.1, ezrin, radixin, moesin homology) domain bound directly to GATA4 and enhanced its CHIP (C terminus of Hsp70-interacting protein) E3 ligase–dependent polyubiquitination and degradation. These studies reveal new developmental and anti-inflammatory roles for kinase-inhibited FAK in limiting VCAM-1 production via nuclear localization and promotion of GATA4 turnover.

Focal adhesion kinase is a phospho-regulated repressor of Rac and proliferation in human endothelial cells

Focal adhesion kinase (FAK) is critically positioned to integrate signals from the extracellular matrix and cellular adhesion. It is essential for normal vascular development and has been implicated in a wide range of cellular functions including the regulation of cell proliferation, migration, differentiation, and survival. It is currently being actively targeted therapeutically using different approaches. We have used human endothelial cells as a model system to compare the effects of inhibiting FAK through several different approaches including dominant negatives, kinase inhibitors and shRNA. We find that manipulations of FAK signaling that result in inhibition of FAK 397 phosphorylation inhibit proliferation and migration. However, abolition of FAK expression using stable (shRNA) or transient (siRNA) approaches does not interfere with these cellular functions. The ability to regulate cell proliferation by FAK manipulation is correlated with the activation status of Rac, an essential signal for the regulation of cyclin-dependent kinase inhibitors. The knockdown of FAK, while not affecting cellular proliferation or migration, dramatically interferes with vascular morphogenesis and survival, mirroring in vivo findings. We propose a novel model of FAK signaling whereby one of the multifunctional roles of FAK as a signaling protein includes FAK as a phospho-regulated repressor of Rac activation, with important implications on interpretation of research experiments and therapeutic development.

VEGF-induced vascular permeability is mediated by FAK

Endothelial cells (ECs) form cell-cell adhesive junctional structures maintaining vascular integrity. This barrier is dynamically regulated by vascular endothelial growth factor (VEGF) receptor signaling. We created an inducible knockin mouse model to study the contribution of the integrin-associated focal adhesion tyrosine kinase (FAK) signaling on vascular function. Here we show that genetic or pharmacological FAK inhibition in ECs prevents VEGF-stimulated permeability downstream of VEGF receptor or Src tyrosine kinase activation in vivo. VEGF promotes tension-independent FAK activation, rapid FAK localization to cell-cell junctions, binding of the FAK FERM domain to the vascular endothelial cadherin (VE-cadherin) cytoplasmic tail, and direct FAK phosphorylation of β-catenin at tyrosine-142 (Y142) facilitating VE-cadherin-β-catenin dissociation and EC junctional breakdown. Kinase inhibited FAK is in a closed conformation that prevents VE-cadherin association and limits VEGF-stimulated β-catenin Y142 phosphorylation. Our studies establish a role for FAK as an essential signaling switch within ECs regulating adherens junction dynamics.

Focal adhesion kinase and tumour angiogenesis

Angiogenesis, the formation of new blood vessels from pre-existing ones, is essential for tumour development. It is initiated and regulated by growth factors via their surface receptors, which activate several intracellular signalling pathways in endothelial cells. Cell adhesion molecules, such as integrins, also regulate angiogenesis. Despite these facts, inhibitors of endothelial cell growth factor receptors or integrins have not been as effective as initially hoped in the long-term inhibition of angiogenesis in cancer patients. Signalling downstream of growth factor receptors and integrins converge on the ubiquitously expressed non-receptor tyrosine kinase focal adhesion kinase (FAK). FAK is involved in endothelial cell proliferation, migration and survival, is up-regulated in many cancers and has recently been shown to control tumour angiogenesis. Indeed, FAK inhibitors are presently being developed for the treatment of cancer. However, recent studies have indicated the complexities of understanding the precise role for FAK in angiogenesis. Here we have summarized some of the key features of FAK, addressed some of the apparently contradictory roles of this molecule in angiogenesis and provided some perspectives for future studies.

Ghrelin prevents disruption of the blood-brain barrier after traumatic brain injury

Significant effort has been focused on reducing neuronal damage from post-traumatic brain injury (TBI) inflammation and blood-brain barrier (BBB)-mediated edema. The orexigenic hormone ghrelin decreases inflammation in sepsis models, and has recently been shown to be neuroprotective following subarachnoid hemorrhage. We hypothesized that ghrelin modulates cerebral vascular permeability and mediates BBB breakdown following TBI. Using a weight-drop model, TBI was created in three groups of mice: sham, TBI, and TBI/ghrelin. The BBB was investigated by examining its permeability to FITC-dextran and through quantification of perivascualar aquaporin-4 (AQP-4). Finally, we immunoblotted for serum S100B as a marker of brain injury. Compared to sham, TBI caused significant histologic neuronal degeneration, increases in vascular permeability, perivascular expression of AQP-4, and serum levels of S100B. Treatment with ghrelin mitigated these effects; after TBI, ghrelin-treated mice had vascular permeability and perivascular AQP-4 and S100B levels that were similar to sham. Our data suggest that ghrelin prevents BBB disruption after TBI. This is evident by a decrease in vascular permeability that is linked to a decrease in AQP-4. This decrease in vascular permeability may diminish post-TBI brain tissue damage was evident by decreased S100B.

Endothelial FAK as a therapeutic target in disease

Focal adhesions (FA) are important mediators of endothelial cytoskeletal interactions with the extracellular matrix (ECM) via transmembrane receptors, integrins and integrin-associated intracellular proteins. This communication is essential for a variety of cell processes including EC barrier regulation and is mediated by the non-receptor protein tyrosine kinase, focal adhesion kinase (FAK). As FA mediate the basic response of EC to a variety of stimuli and FAK is essential to these responses, the idea of targeting EC FAK as a therapeutic strategy for an assortment of diseases is highly promising. In particular, inhibition of FAK could prove beneficial in a variety of cancers via effects on EC proliferation and angiogenesis, in acute lung injury (ALI) via the attenuation of lung vascular permeability, and in rheumatoid arthritis via reductions in synovial angiogenesis. In addition, there are potential therapeutic benefits of FAK inhibition in cardiovascular disease and diabetic nephropathy as well. Several drugs that target EC FAK are now in existence and include agents currently under investigation in preclinical models as well as drugs that are readily available such as the sphingolipid analog FTY720 and statins. As the role of EC FAK in the pathogenesis of a variety of diseases continues to be explored and new insights are revealed, drug targeting of FAK will continue to be an important area of investigation and may ultimately lead to highly novel and effective strategies to treat these diseases.

Non-invasive detection of spatio-temporal activation of SBE and NFAT5 promoters in transgenic reporter mice following stroke

The characterization of molecular responses following cerebral ischemia-induced changes in animal models capable of undergoing real-time analysis is an important goal for stroke research. In this study, we use transgenic mice to examine the activation of two different promoters in a firefly luciferase reporter mouse analyzable through a non-invasive bioluminescent imaging system. In the first model, we examine the middle cerebral artery occlusion (MCAO)-induced activation of Smad-binding elements (SBE), a downstream target of Smad 1/2/3 transcription factors, in which SBEs regulate the expression of the fluc reporter. We observed that MCAO induces a bilateral activation (i.e., both ipsilateral and contralateral brain hemispheres) of the SBE-luc reporter with a peak at 24 h. In the second model, we examined MCAO-induced activation of the osmolarity-sensitive promoter nuclear factor of activated T-cell 5 (NFAT5) and identified a peak reporter expression 72 h post-MCAO in the ipsilateral but not contralateral hemisphere. In each of these models, the assessment of post-MCAO fluc-expression provided both a quantitative measure (i.e., radiance in photons/sec/cm(2) /steradian) as well as qualitative localization of the molecular response following focal ischemic injury.

Non-invasive quantification of brain tumor-induced astrogliosis

Background

CNS injury including stroke, infection, and tumor growth lead to astrogliosis, a process that involves upregulation of glial fibrillary acidic protein (GFAP) in astrocytes. However, the kinetics of astrogliosis that is related to these insults (i.e. tumor) is largely unknown.

Results

Using transgenic mice expressing firefly luciferase under the regulation of the GFAP promoter (GFAP-luc), we developed a model system to monitor astrogliosis upon tumor growth in a rapid, non-invasive manner. A biphasic induction of astrogliosis was observed in our xenograft model in which an early phase of activation of GFAP was associated with inflammatory response followed by a secondary, long-term upregulation of GFAP. These animals reveal GFAP activation with kinetics that is in parallel with tumor growth. Furthermore, a strong correlation between astrogliosis and tumor size was observed.

Conclusions

Our results suggest that non-invasive, quantitative bioluminescent imaging using GFAP-luc reporter animal is a useful tool to monitor temporal-spatial kinetics of host-mediated astrogliosis that is associated with glioma and metastatic brain tumor growth.