The pattern of enhancement of Src kinase activity on platelet-derived growth factor stimulation of glioblastoma cells is affected by the integrin engaged

Emerging opportunities to treat idiopathic pulmonary fibrosis: Design, discovery, and optimizations of small-molecule drugs targeting fibrogenic pathways

Idiopathic pulmonary fibrosis (IPF) is the most common fibrotic form of idiopathic diffuse lung disease. Due to limited treatment options, IPF patients suffer from poor survival. About ten years ago, Pirfenidone (Shionogi, 2008; InterMune, 2011) and Nintedanib (Boehringer Ingelheim, 2014) were approved, greatly changing the direction of IPF drug design. However, limited efficacy and side effects indicate that neither can reverse the process of IPF. With insights into the occurrence of IPF, novel targets and agents have been proposed, which have fundamentally changed the treatment of IPF. With the next-generation agents, targeting pro-fibrotic pathways in the epithelial-injury model offers a promising approach. Besides, several next-generation IPF drugs have entered phase II/III clinical trials with encouraging results. Due to the rising IPF treatment requirements, there is an urgent need to completely summarize the mechanisms, targets, problems, and drug design strategies over the past ten years. In this review, we summarize known mechanisms, target types, drug design, and novel technologies of IPF drug discovery, aiming to provide insights into the future development and clinical application of next-generation IPF drugs.

Human cytomegalovirus in cancer: the mechanism of HCMV-induced carcinogenesis and its therapeutic potential

Cancer is one of the leading causes of death worldwide. Human cytomegalovirus (HCMV), a well-studied herpesvirus, has been implicated in malignancies derived from breast, colorectal muscle, brain, and other cancers. Intricate host-virus interactions are responsible for the cascade of events that have the potential to result in the transformed phenotype of normal cells. The HCMV genome contains oncogenes that may initiate these types of cancers, and although the primary HCMV infection is usually asymptomatic, the virus remains in the body in a latent or persistent form. Viral reactivation causes severe health issues in immune-compromised individuals, including cancer patients, organ transplants, and AIDS patients. This review focuses on the immunologic mechanisms and molecular mechanisms of HCMV-induced carcinogenesis, methods of HCMV treatment, and other studies. Studies show that HCMV DNA and virus-specific antibodies are present in many types of cancers, implicating HCMV as an important player in cancer progression. Importantly, many clinical trials have been initiated to exploit HCMV as a therapeutic target for the treatment of cancer, particularly in immunotherapy strategies in the treatment of breast cancer and glioblastoma patients. Taken together, these findings support a link between HCMV infections and cellular growth that develops into cancer. More importantly, HCMV is the leading cause of birth defects in newborns, and infection with HCMV is responsible for abortions in pregnant women.

Myeloid-derived suppressor cells in head and neck squamous cell carcinoma

Myeloid-derived suppressor cells (MDSCs), which originated from hematopoietic stem cells, are heterogeneous population of cells that have different differentiation patterns and widely presented in tumor microenvironment. For tumor research, myeloid suppressor cells have received extensive attention since their discovery due to their specific immunosuppressive properties, and the mechanisms of immunosuppression and therapeutic approaches for MDSCs have been investigated in a variety of different types of malignancies. To improve the efficacy of treatment for head and neck squamous cell carcinoma (HNSCC), a disease with a high occurrence, immunotherapy has gradually emerged in after traditional surgery and subsequent radiotherapy and chemotherapy, and has made some progress. In this review, we introduced the mechanisms on the development, differentiation, and elimination of MDSCs and provided a detailed overview of the mechanisms behind the immunosuppressive properties of MDSCs. We summarized the recent researches on MDSCs in HNSCC, especially for targeting-MDSCs therapy and combination with other types of therapy such as immune checkpoint blockade (ICB). Furthermore, we looked at drug delivery patterns and collected the current diverse drug delivery systems for the improvement that contributed to therapy against MDSCs in HNSCC. Most importantly, we made possible outlooks for the future research priorities, which provide a basis for further study on the clinical significance and therapeutic value of MDSCs in HNSCC.

Identification of imidazo[4,5-c]pyridin-2-one derivatives as novel Src family kinase inhibitors against glioblastoma

Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumour in the central nervous system (CNS). As the ideal targets for GBM treatment, Src family kinases (SFKs) have attracted much attention. Herein, a new series of imidazo[4,5-c]pyridin-2-one derivatives were designed and synthesised as SFK inhibitors. Compounds 1d, 1e, 1q, 1s exhibited potential Src and Fyn kinase inhibition in the submicromolar range, of which were next tested for their antiproliferative potency on four GBM cell lines. Compound 1s showed effective activity against U87, U251, T98G, and U87-EGFRvIII GBM cell lines, comparable to that of lead compound PP2. Molecular dynamics (MDs) simulation revealed the possible binding patterns of the most active compound 1s in ATP binding site of SFKs. ADME prediction suggested that 1s accord with the criteria of CNS drugs. These results led us to identify a novel SFK inhibitor as candidate for GBM treatment.

Targeting RGD-binding integrins as an integrative therapy for diabetic retinopathy and neovascular age-related macular degeneration

Integrins are a class of transmembrane receptors that are involved in a wide range of biological functions. Dysregulation of integrins has been implicated in many pathological processes and consequently, they are attractive therapeutic targets. In the ophthalmology arena, there is extensive evidence suggesting that integrins play an important role in diabetic retinopathy (DR), age-related macular degeneration (AMD), glaucoma, dry eye disease and retinal vein occlusion. For example, there is extensive evidence that arginyl-glycyl-aspartic acid (Arg-Gly-Asp; RGD)-binding integrins are involved in key disease hallmarks of DR and neovascular AMD (nvAMD), specifically inflammation, vascular leakage, angiogenesis and fibrosis. Based on such evidence, drugs that engage integrin-linked pathways have received attention for their potential to block all these vision-threatening pathways. This review focuses on the pathophysiological role that RGD-binding integrins can have in complex multifactorial retinal disorders like DR, diabetic macular edema (DME) and nvAMD, which are leading causes of blindness in developed countries. Special emphasis will be given on how RGD-binding integrins can modulate the intricate molecular pathways and regulate the underlying pathological mechanisms. For instance, the interplay between integrins and key molecular players such as growth factors, cytokines and enzymes will be summarized. In addition, recent clinical advances linked to targeting RGD-binding integrins in the context of DME and nvAMD will be discussed alongside future potential for limiting progression of these diseases.

The Role of Hypoxia and SRC Tyrosine Kinase in Glioblastoma Invasiveness and Radioresistance

Advances in functional imaging are supporting neurosurgery and radiotherapy for glioblastoma, which still remains the most aggressive brain tumor with poor prognosis. The typical infiltration pattern of glioblastoma, which impedes a complete surgical resection, is coupled with a high rate of invasiveness and radioresistance, thus further limiting efficient therapy, leading to inevitable and fatal recurrences. Hypoxia is of crucial importance in gliomagenesis and, besides reducing radiotherapy efficacy, also induces cellular and molecular mediators that foster proliferation and invasion. In this review, we aimed at analyzing the biological mechanism of glioblastoma invasiveness and radioresistance in hypoxic niches of glioblastoma. We also discussed the link between hypoxia and radiation-induced radioresistance with activation of SRC proto-oncogene non-receptor tyrosine kinase, prospecting potential strategies to overcome the current limitation in glioblastoma treatment.

Fyn Tyrosine Kinase as Harmonizing Factor in Neuronal Functions and Dysfunctions

Fyn is a non-receptor or cytoplasmatic tyrosine kinase (TK) belonging to the Src family kinases (SFKs) involved in multiple transduction pathways in the central nervous system (CNS) including synaptic transmission, myelination, axon guidance, and oligodendrocyte formation. Almost one hundred years after the original description of Fyn, this protein continues to attract extreme interest because of its multiplicity of actions in the molecular signaling pathways underlying neurodevelopmental as well as neuropathologic events. This review highlights and summarizes the most relevant recent findings pertinent to the role that Fyn exerts in the brain, emphasizing aspects related to neurodevelopment and synaptic plasticity. Fyn is a common factor in healthy and diseased brains that targets different proteins and shapes different transduction signals according to the neurological conditions. We will primarily focus on Fyn-mediated signaling pathways involved in neuronal differentiation and plasticity that have been subjected to considerable attention lately, opening the fascinating scenario to target Fyn TK for the development of potential therapeutic interventions for the treatment of CNS injuries and certain neurodegenerative disorders like Alzheimer’s disease.

Src Family Kinases as Therapeutic Targets in Advanced Solid Tumors: What We Have Learned so Far

Src is the prototypal member of Src Family tyrosine Kinases (SFKs), a large non-receptor kinase class that controls multiple signaling pathways in animal cells. SFKs activation is necessary for the mitogenic signal from many growth factors, but also for the acquisition of migratory and invasive phenotype. Indeed, oncogenic activation of SFKs has been demonstrated to play an important role in solid cancers; promoting tumor growth and formation of distant metastases. Several drugs targeting SFKs have been developed and tested in preclinical models and many of them have successfully reached clinical use in hematologic cancers. Although in solid tumors SFKs inhibitors have consistently confirmed their ability in blocking cancer cell progression in several experimental models; their utilization in clinical trials has unveiled unexpected complications against an effective utilization in patients. In this review, we summarize basic molecular mechanisms involving SFKs in cancer spreading and metastasization; and discuss preclinical and clinical data highlighting the main challenges for their future application as therapeutic targets in solid cancer progression

The Role of Kinase Signaling in Resistance to Bevacizumab Therapy for Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is the most malignant primary brain tumor and is characterized by vascular hyperplasia, necrosis, and high cell proliferation. Despite current standard therapies, including surgical resection and chemoradiotherapy, GBM patients survive for only about 15 months after diagnosis. Recently, the U.S. Food and Drug Administration (FDA) has approved an antiangiogenesis medication for recurrent GBM-bevacizumab-which has improved progression-free survival in GBM patients. Although bevacizumab has resulted in significant early clinical benefit, it inescapably predisposes tumor to relapse that can be represented as an infiltrative phenotype. Fundamentally, bevacizumab antagonizes the vascular endothelial growth factor A (VEGF_A), which is consistently released on both endothelial cells (ECs) and GBM cells. Actually, VEGF_A inhibition on the ECs leads to the suppression of vascular progression, permeability, and the vasogenic edema. However, the consequence of the VEGF_A pathway blockage on the GBM cells remains controversial. Nevertheless, a piece of evidence supports the relationship between bevacizumab application and compensatory activation of kinase signaling within GBM cells, leading to a tumor cell invasion known as the main mechanism of bevacizumab-induced tumor resistance. A complete understanding of kinase responses associated with tumor invasion in bevacizumab-resistant GBMs offers new therapeutic opportunities. Thus, this study aimed at presenting a brief overview of preclinical and clinical data of the tumor invasion and resistance induced by bevacizumab administration in GBMs, with a focus on the kinase responses during treatment. The novel therapeutic strategies to overcome this resistance by targeting protein kinases have also been summarized.

Neuronal Wiskott-Aldrich syndrome protein regulates Pseudomonas aeruginosa-induced lung vascular permeability through the modulation of actin cytoskeletal dynamics

Pulmonary edema associated with increased vascular permeability is a severe complication of Pseudomonas (P.) aeruginosa-induced acute lung injury. The mechanisms underlying P aeruginosa-induced vascular permeability are not well understood. In the present study, we investigated the role of neuronal Wiskott Aldrich syndrome protein (N-WASP) in modulating P aeruginosa-induced vascular permeability. Using lung microvascular endothelial and alveolar epithelial cells, we demonstrated that N-WASP downregulation attenuated P aeruginosa-induced actin stress fiber formation and prevented paracellular permeability. P aeruginosa-induced dissociation between VE-cadherin and β-catenin, but increased association between N-WASP and VE-cadherin, suggesting a role for N-WASP in promoting P aeruginosa-induced adherens junction rupture. P aeruginosa increased N-WASP-Y256 phosphorylation, which required the activation of Rho GTPase and focal adhesion kinase. Increased N-WASP-Y256 phosphorylation promotes N-WASP and integrin αVβ6 association as well as TGF-β-mediated permeability across alveolar epithelial cells. Inhibition of N-WASP-Y256 phosphorylation by N-WASP-Y256F overexpression blocked N-WASP effects in P aeruginosa-induced actin stress fiber formation and increased paracellular permeability. In vivo, N-WASP knockdown attenuated the development of pulmonary edema and improved survival in a mouse model of P aeruginosa pneumonia. Together, our data demonstrate that N-WASP plays an essential role in P aeruginosa-induced vascular permeability and pulmonary edema through the modulation of actin cytoskeleton dynamics.

Direct contact with perivascular tumor cells enhances integrin αvβ3 signaling and migration of endothelial cells

The secretion of soluble pro-angiogenic factors by tumor cells and stromal cells in the perivascular niche promotes the aggressive angiogenesis that is typical of glioblastoma (GBM). Here, we show that angiogenesis also can be promoted by a direct interaction between brain tumor cells, including tumor cells with cancer stem-like properties (CSCs), and endothelial cells (ECs). As shown in vitro, this direct interaction is mediated by binding of integrin αvβ3 expressed on ECs to the RGD-peptide in L1CAM expressed on CSCs. It promotes both EC network formation and enhances directed migration toward basic fibroblast growth factor. Activation of αvβ3 and bone marrow tyrosine kinase on chromosome X (BMX) is required for migration stimulated by direct binding but not for migration stimulated by soluble factors. RGD-peptide treatment of mice with established intracerebral GBM xenografts significantly reduced the percentage of Sox2-positive tumor cells and CSCs in close proximity to ECs, decreased integrin αvβ3 and BMX activation and p130CAS phosphorylation in the ECs, and reduced the vessel surface area. These results reveal a previously unrecognized aspect of the regulation of angiogenesis in GBM that can impact therapeutic anti-angiogenic targeting.

Role of NRP-1 in VEGF-VEGFR2-Independent Tumorigenesis

Recent studies suggest that neuropilin-1 (NRP-1) promotes angiogenesis mainly via VEGF and its receptors. It promotes tumorigenesis via formation of the NRP-1/ VEGF (vascular endothelial growth factor)/VEGFR2 (vascular endothelial growth factor receptor 2) complex. In addition to VEGF and its receptors, NRP-1 also binds with other growth factors such as platelet-derived growth factor (PDGF) and platelet-derived growth factor receptor (PDGFR). PDGF plays important roles in cellular proliferation and, in particular, blood vessel formation. Moreover, recent studies show that NRP-1 promotes angiogenesis via the NRP-1-ABL pathway, but independent of VEGF-VEGFR2. RAD51 is a protein involved in the signaling pathways of NRP1-ABL and PDGF(R), the expression of which is positively associated with cell radioresistance and chemoresistance. NRP-1 activates the signaling pathways of ABL and PDGF(R) to upregulate RAD51, which induces resistance to radiotherapy and chemotherapy in cancer cells. Furthermore, NRP-1 activates the tumor microenvironment by binding with fibronectin and activating ABL, thereby promoting tumor growth. Inhibition of NRP-1 may overcome the limitations of individually inhibiting the VEGF-VEGFR2 pathway in cancer therapy and provide new ideas for cancer treatment. Therefore, we review the role of NRP-1 in VEGF-VEGFR2-independent tumorigenesis.

Human cytomegalovirus infection enhances cell proliferation, migration and upregulation of EMT markers in colorectal cancer-derived stem cell-like cells

Increasing evidence suggests a link between persistent human cytomegalovirus (HCMV) infection and cancer. Although the role of HCMV in cancer is still elusive, recent studies revealed the presence of HCMV nucleic acids and proteins in different cancer types such as glioblastoma, colorectal, breast, and prostate cancers, and neuroblastoma. Although HCMV may not be directly associated with the neoplastic transformation, the presence of HCMV DNA in the tumorous tissue has been associated with altered clinical outcomes in cancer patients. However, the mechanisms involved in the association between colorectal cancer (CRC) and HCMV are unclear. In this study, we investigated the influence of HCMV infection on CRC or their derived cells. Proliferation and migration assays revealed a high infection efficiency in CRC-derived HT29 and SW480 'stem-like' cells. After 24, 48 and 72 h of HCMV infection, both HT29 and SW480 parental and stem-like cells showed a significant increase in cell proliferation and viability (p<0.0001). Moreover, HCMV infection promoted cell migration. These results demonstrate a significant phenotypic alteration in the CRC cell line upon HCMV infection. Using epithelial to mesenchymal transition (EMT) assays, we demonstrated that the EMT markers and driver genes were upregulated during the virus infection. The WNT signaling pathway, which is associated with the proliferation and migration of CRC cells, was upregulated (6-fold) in HCMV-infected cells as compared to the non-infected cells at day 7 from infection.

Interaction of Src and Alpha-V Integrin Regulates Fibroblast Migration and Modulates Lung Fibrosis in A Preclinical Model of Lung Fibrosis

Src kinase is known to regulate fibroblast migration. However, the contribution of integrin and Src kinase interaction to lung fibrosis has not been mechanistically investigated. Our data demonstrate that integrin alpha v (αV) recruited Src kinase and that leads to subsequent Src activation in fibroblasts plated on fibrotic matrix, osteopontin. Src interaction with integrin αV is required for integrin αV-mediated Src activation, and the subsequent fibroblast migration. The study identified that β5 and β3 are the major integrins for this effect on osteopontin. In contrast, integrins β1, β6, and β8 did not have a critical role in this phenomenon. Importantly, Src inhibitor significantly reduces fibroblast migration stimulated by PDGF-BB and reduced in vivo lung fibrosis in mice. Src inhibitor reduced Src activation and blocked the signaling transduction by integrin αV, inhibited migration signaling pathways and reduced extracellular matrix protein production, and blocked myofibroblast differentiation in vivo in mouse lung tissues. The present study supports that the interaction of Src Kinase and integrins plays a critical role in the development of lung fibrosis and the signaling involved may present a novel opportunity to target deadly fibrotic diseases.

Focal adhesion kinase signaling determines the fate of lung epithelial cells in response to TGF-β

Alveolar epithelial cell (AEC) injury and apoptosis are prominent pathological features of idiopathic pulmonary fibrosis (IPF). There is evidence of AEC plasticity in lung injury repair response and in IPF. In this report, we explore the role of focal adhesion kinase (FAK) signaling in determining the fate of lung epithelial cells in response to transforming growth factor-β1 (TGF-β1). Rat type II alveolar epithelial cells (RLE-6TN) were treated with or without TGF-β1, and the expressions of mesenchymal markers, phenotype, and function were analyzed. Pharmacological protein kinase inhibitors were utilized to screen for SMAD-dependent and -independent pathways. SMAD and FAK signaling was analyzed using siRNA knockdown, inhibitors, and expression of a mutant construct of FAK. Apoptosis was measured using cleaved caspase-3 and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. TGF-β1 induced the acquisition of mesenchymal markers, including α-smooth muscle actin, in RLE-6TN cells and enhanced the contraction of three-dimensional collagen gels. This phenotypical transition or plasticity, epithelial-myofibroblast plasticity (EMP), is dependent on SMAD3 and FAK signaling. FAK activation was found to be dependent on ALK5/SMAD3 signaling. We observed that TGF-β1 induces both EMP and apoptosis in the same cell culture system but not in the same cell. While blockade of SMAD signaling inhibited EMP, it had a minimal effect on apoptosis; in contrast, inhibition of FAK signaling markedly shifted to an apoptotic fate. The data support that FAK activation determines whether AECs undergo EMP vs. apoptosis in response to TGF-β1 stimulation. TGF-β1-induced EMP is FAK- dependent, whereas TGF-β1-induced apoptosis is favored when FAK signaling is inhibited.

Inhibition of SRC family kinases reduces myeloid-derived suppressor cells in head and neck cancer

SRC family kinases (SFKs), a group of nonreceptor tyrosine kinases, modulate multiple cellular functions, such as cell proliferation, differentiation and metabolism. SFKs display aberrant activity in progressive stages of human cancers. However, the precise role of SFKs in the head and neck squamous cell carcinoma (HNSCC) signaling network is far from clear. In this study, we found that the inhibition of SFKs activity by dasatinib effectively reduced the tumor size and population of MDSCs in the HNSCC mouse model. Molecular analysis indicates that phosphorylation of LYN, rather than SRC, was inhibited by dasatinib treatment. Next, we analyzed LYN expression by immunostaining and found that it was overexpressed in the human HNSCC specimens. Moreover, LYN expression in stromal cells positively correlated with myeloid-derived suppressor cells (MDSCs) makers CD11b and CD33 in human HNSCC. The dual positive expression of LYN in epithelial and stromal cells (EPI⁺ SRT⁺ ) was associated with unfavorable overall survival of HNSCC patients. These findings indicate that SFKs may be a potential target for an effective immunotherapy of HNSCC by decreasing MDSCs and moreover, LYN will have an impact on such therapeutic strategy.

Neuronal Wiskott-Aldrich syndrome protein regulates TGF-β1-mediated lung vascular permeability

TGF-β1 induces an increase in paracellular permeability and actin stress fiber formation in lung microvascular endothelial and alveolar epithelial cells via small Rho GTPase. The molecular mechanism involved is not fully understood. Neuronal Wiskott-Aldrich syndrome protein (N-WASP) has an essential role in actin structure dynamics. We hypothesized that N-WASP plays a critical role in these TGF-β1-induced responses. In these cell monolayers, we demonstrated that N-WASP down-regulation by short hairpin RNA prevented TGF-β1-mediated disruption of the cortical actin structure, actin stress filament formation, and increased permeability. Furthermore, N-WASP down-regulation blocked TGF-β1 activation mediated by IL-1β in alveolar epithelial cells, which requires actin stress fiber formation. Control short hairpin RNA had no effect on these TGF-β1-induced responses. TGF-β1-induced phosphorylation of Y256 of N-WASP via activation of small Rho GTPase and focal adhesion kinase mediates TGF-β1-induced paracellular permeability and actin cytoskeleton dynamics. In vivo, compared with controls, N-WASP down-regulation increases survival and prevents lung edema in mice induced by bleomycin exposure-a lung injury model in which TGF-β1 plays a critical role. Our data indicate that N-WASP plays a crucial role in the development of TGF-β1-mediated acute lung injury by promoting pulmonary edema via regulation of actin cytoskeleton dynamics.-Wagener, B. M., Hu, M., Zheng, A., Zhao, X., Che, P., Brandon, A., Anjum, N., Snapper, S., Creighton, J., Guan, J.-L., Han, Q., Cai, G.-Q., Han, X., Pittet, J.-F., Ding, Q. Neuronal Wiskott-Aldrich syndrome protein regulates TGF-β1-mediated lung vascular permeability.

Cytomegalovirus-targeted immunotherapy and glioblastoma: hype or hope?

Malignant gliomas, including glioblastoma (GBM), are the most common primary brain tumors. Despite extensive research only modest gains have been made in long-term survival. Standard of care involves maximizing safe surgical resection followed by concurrent chemoradiation with temozolomide. Immunotherapy for GBM is an area of intense research in recent years. New immunotherapies, although promising, have not been integrated into standard practice. Human cytomegalovirus (HCMV) is a DNA virus of the family Herpesviridae. Human seroprevalence is approximately 80%, and in most cases, is associated with asymptomatic infection. HCMV may be an important agent in the initiation, promotion and/or progression of tumorigenesis. Regardless of a possible etiologic role in GBM, interest has centered on exploiting this association for development of immunomodulatory therapies.

Src family kinases differentially influence glioma growth and motility

Src-family kinase (SFK) signaling impacts multiple tumor-related properties, particularly in the context of the brain tumor glioblastoma. Consequently, the pan-SFK inhibitor dasatinib has emerged as a therapeutic strategy, despite physiologic limitations to its effectiveness in the brain. We investigated the importance of individual SFKs (Src, Fyn, Yes, and Lyn) to glioma tumor biology by knocking down individual SFK expression both in culture (LN229, SF767, GBM8) and orthotopic xenograft (GBM8) contexts. We evaluated the effects of these knockdowns on tumor cell proliferation, migration, and motility-related signaling in culture, as well as overall survival in the orthotopic xenograft model. The four SFKs differed significantly in their importance to these properties. In culture, Src, Fyn, and Yes knockdown generally reduced growth and migration and altered motility-related phosphorylation patterns while Lyn knockdown did so to a lesser extent. However the details of these effects varied significantly depending on the cell line: in no case were conclusions about the role of a particular SFK applicable to all of the measures or all of the cell types examined. In the orthotopic xenograft model, mice implanted with non-target or Src or Fyn knockdown cells showed no differences in survival. In contrast, mice implanted with Yes knockdown cells had longer survival, associated with reduced tumor cell proliferation. Those implanted with Lyn knockdown cells had shorter survival, associated with higher overall tumor burden. Together, our results suggest that Yes signaling directly affects tumor cell biology in a pro-tumorigenic manner, while Lyn signaling affects interactions between tumor cells and the microenvironment in an anti-tumor manner. In the context of therapeutic targeting of SFKs, these results suggest that pan-SFK inhibitors may not produce the intended therapeutic benefit when Lyn is present.

The Effect of Chemoradiotherapy with SRC Tyrosine Kinase Inhibitor, PP2 and Temozolomide on Malignant Glioma Cells In Vitro and In Vivo

PURPOSE

We investigated the effect of chemoradiotherapy with PP2 and temozolomide (TMZ) on malignant glioma cells using clonogenic assays and in vivo brain tumor model.

MATERIALS AND METHODS

The effect of PP2 on radiosensitivity of U251 and T98G cells was investigated using clonogenic assays. The expression of E-cadherin, matrix metalloproteinases 2 (MMP2), Ephrin type-A receptor 2 (EphA2), and vascular endothelial growth factor (VEGF) was measured by Western blotting and an accumulation of γH2AX foci 6 hours after radiotherapy was measured after PP2 treatment. The effect of PP2 on migration, invasion, and vasculogenic mimicry formation (VMF) of U251 cells was evaluated. In an orthotopical brain tumor model with U251 cells, PP2 was injected intraperitoneally with or without oral TMZ before, during and after whole brain radiotherapy. Bioluminescence images were taken to visualize in vivo tumors and immunohistochemical staining of VEGF, CD31, EphA2, and hypoxia-inducible factor 1a was performed.

RESULTS

PP2 increased radiosensitivity of U251 and T98G cells without decreasing survival of normal human astrocytes. Chemoradiotherapy with PP2 and TMZ resulted in increased accumulation of γH2AX foci. PP2 induced overexpression of E-cadherin and suppression of MMP2, VEGF, and EphA2. PP2 also compromised invasion, migration, and VMF of U251 cells. In brain tumors, chemoradiotherapy with PP2 and TMZ decreased tumor volume best, but not statistically significantly compared with chemoradiotherapy with TMZ. The expression of VEGF and CD31 was suppressed in PP2-treated tumors.

CONCLUSION

PP2 enhances radiosensitivity of malignant glioma cells and suppresses invasion and migration of U251 cells. Chemoradiotherapy with PP2 and TMZ resulted in non-significant tumor volume decrease.

Stromal transcriptional profiles reveal hierarchies of anatomical site, serum response and disease and identify disease specific pathways

Synovial fibroblasts in persistent inflammatory arthritis have been suggested to have parallels with cancer growth and wound healing, both of which involve a stereotypical serum response programme. We tested the hypothesis that a serum response programme can be used to classify diseased tissues, and investigated the serum response programme in fibroblasts from multiple anatomical sites and two diseases. To test our hypothesis we utilized a bioinformatics approach to explore a publicly available microarray dataset including rheumatoid arthritis (RA), osteoarthritis (OA) and normal synovial tissue, then extended those findings in a new microarray dataset representing matched synovial, bone marrow and skin fibroblasts cultured from RA and OA patients undergoing arthroplasty. The classical fibroblast serum response programme discretely classified RA, OA and normal synovial tissues. Analysis of low and high serum treated fibroblast microarray data revealed a hierarchy of control, with anatomical site the most powerful classifier followed by response to serum and then disease. In contrast to skin and bone marrow fibroblasts, exposure of synovial fibroblasts to serum led to convergence of RA and OA expression profiles. Pathway analysis revealed three inter-linked gene networks characterising OA synovial fibroblasts: Cell remodelling through insulin-like growth factors, differentiation and angiogenesis through _3 integrin, and regulation of apoptosis through CD44. We have demonstrated that Fibroblast serum response signatures define disease at the tissue level, and that an OA specific, serum dependent repression of genes involved in cell adhesion, extracellular matrix remodelling and apoptosis is a critical discriminator between cultured OA and RA synovial fibroblasts.

HCMV glycoprotein B is expressed in primary glioblastomas and enhances growth and invasiveness via PDGFR-alpha activation

Our laboratory first demonstrated that human cytomegalovirus (HCMV) is associated with the most deadly form of primary brain tumor, glioblastoma (GBM). We showed that HCMV glycoprotein B (gB) mediates viral cellular entry via the receptor tyrosine kinase PDGFR-alpha (PDGFRα), resulting in activation of the PI3K/Akt pathway, a critical signaling axis gliomagenesis. Here, we investigated the effects of gB overexpression on glioma progression. We demonstrate that gB is endogenously expressed in primary GBM samples and show that ectopic gB expression in glioma cells induced sustained phosphorylation of PDGFRα, Akt, and Src. Recombinant gB protein and the whole virus enhanced invasion of primary glioblastoma cells into Matrigel and rat brain slices, and this effect was specifically inhibited by neutralizing antibodies to either gB or PDGFRα. Importantly, neutralizing antibodies to gB significantly inhibited the invasiveness of patient-derived HCMV-positive glioblastoma cells, suggesting that functional inhibition of this viral protein could hinder glioblastoma progression. gB overexpression promoted in vivo glioma growth and enhanced phosphor-Akt levels and tumor cell dispersal relative to controls. Taken together, our results demonstrate that HCMV gB promotes key hallmarks of glioblastoma and suggest that targeting gB may have therapeutic benefits for patients with HCMV -positive gliomas.

S100A4 promotes pancreatic cancer progression through a dual signaling pathway mediated by Src and focal adhesion kinase

S100A4 expression is associated with poor clinical outcomes of patients with pancreatic cancer. The effects of loss or gain of S100A4 were examined in pancreatic cancer cell lines. S100A4 downregulation remarkably reduces cell migration and invasion, inhibits proliferation, and induces apoptosis in pancreatic tumor cells. S100A4 downregulation results in significant cell growth inhibition and apoptosis in response to TGF-β1, supporting a non-canonical role of S100A4 in pancreatic cancer. The role of S100A4 in tumor progression was studied by using an orthotopic human pancreatic cancer xenograft mouse model. Tumor mass is remarkably decreased in animals injected with S100A4-deficient pancreatic tumor cells. P27^Kip1 expression and cleaved caspase-3 are increased, while cyclin E expression is decreased, in S100A4-deficient pancreatic tumors in vivo. S100A4-deficient tumors have lower expression of vascular endothelial growth factor, suggesting reduced angiogenesis. Biochemical assays revealed that S100A4 activates Src and focal adhesion kinase (FAK) signaling events, and inhibition of both kinases is required to maximally block the tumorigenic potential of pancreatic cancer cells. These findings support that S100A4 plays an important role in pancreatic cancer progression in vivo and S100A4 promotes tumorigenic phenotypes of pancreatic cancer cells through the Src-FAK mediated dual signaling pathway.

Rapid synthesis of cyclic RGD conjugated gold nanoclusters for targeting and fluorescence imaging of melanoma A375 cells

A simple, rapid, and inexpensive method for the synthesis of cyclic arginine-glycine-aspartic acid (RGD) peptide conjugated gold nanoclusters (RGD-GNCs) was reported. The nanoclusters were synthesized with chloraurate as precursor and cyclic RGD peptides as both reducing and protecting agent directly under alkali condition, and the whole synthetic process only took 15 min at room temperature. The properties of the nanoclusters were characterized by means of ultraviolet-visible spectra, Fourier transform infrared spectroscopy (FTIR), fluorescence, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The prepared gold nanoclusters were successfully used as a contrast agent in fluorescence imaging of the melanoma A375 cells, which overexpress the integrin αvβ3. The results demonstrated that our nanoclusters possess good biocompatibility, stability, and low toxicity. Moreover, the method is expected to be applicable to the synthesis of nanoclusters conjugated with other biomolecules.

Therapeutic targeting of SRC kinase in myofibroblast differentiation and pulmonary fibrosis

Myofibroblasts are effector cells in fibrotic disorders that synthesize and remodel the extracellular matrix (ECM). This study investigated the role of the Src kinase pathway in myofibroblast activation in vitro and fibrogenesis in vivo. The profibrotic cytokine, transforming growth factor β1 (TGF-β1), induced rapid activation of Src kinase, which led to myofibroblast differentiation of human lung fibroblasts. The Src kinase inhibitor AZD0530 (saracatinib) blocked TGF-β1-induced Src kinase activation in a dose-dependent manner. Inhibition of Src kinase significantly reduced α-smooth muscle actin (α-SMA) expression, a marker of myofibroblast differentiation, in TGF-β1-treated lung fibroblasts. In addition, the induced expression of collagen and fibronectin and three-dimensional collagen gel contraction were also significantly inhibited in AZD0530-treated fibroblasts. The therapeutic efficiency of Src kinase inhibition in vivo was tested in the bleomycin murine lung fibrosis model. Src kinase activation and collagen accumulation were significantly reduced in the lungs of AZD0530-treated mice when compared with controls. Furthermore, the total fibrotic area and expression of α-SMA and ECM proteins were significantly decreased in lungs of AZD0530-treated mice. These results indicate that Src kinase promotes myofibroblast differentiation and activation of lung fibroblasts. Additionally, these studies provide proof-of-concept for targeting the noncanonical TGF-β signaling pathway involving Src kinase as an effective therapeutic strategy for lung fibrosis.

Platelet-derived growth factor β-receptor, transforming growth factor β type I receptor, and CD44 protein modulate each other's signaling and stability

Growth factors, such as platelet-derived growth factor BB (PDGF-BB) and transforming growth factor β (TGFβ), are key regulators of cellular functions, including proliferation, migration, and differentiation. Growth factor signaling is modulated by context-dependent cross-talk between different signaling pathways. We demonstrate in this study that PDGF-BB induces phosphorylation of Smad2, a downstream mediator of the canonical TGFβ pathway, in primary dermal fibroblasts. The PDGF-BB-mediated Smad2 phosphorylation was dependent on the kinase activities of both TGFβ type I receptor (TβRI) and PDGF β-receptor (PDGFRβ), and it was prevented by inhibitory antibodies against TGFβ. Inhibition of the activity of the TβRI kinase greatly reduced the PDGF-BB-dependent migration in dermal fibroblasts. Moreover, we demonstrate that the receptors for PDGF-BB and TGFβ interact physically in primary dermal fibroblasts and that stimulation with PDGF-BB induces internalization not only of PDGFRβ but also of TβRI. In addition, silencing of PDGFRβ by siRNA decreased the stability of TβRI and delayed TGFβ-induced signaling. We further show that the hyaluronan receptor CD44 interacts with both PDGFRβ and TβRI. Depletion of CD44 by siRNA increased signaling via PDGFRβ and TβRI by stabilizing the receptor proteins. Our data suggest that cross-talk between PDGFRβ and TβRI occurs in dermal fibroblasts and that CD44 negatively modulates signaling via these receptors.

Urokinase-type plasminogen activator receptor (uPAR) ligation induces a raft-localized integrin signaling switch that mediates the hypermotile phenotype of fibrotic fibroblasts

The urokinase-type plasminogen activator receptor (uPAR) is a glycosylphosphatidylinositol-linked membrane protein with no cytosolic domain that localizes to lipid raft microdomains. Our laboratory and others have documented that lung fibroblasts from patients with idiopathic pulmonary fibrosis (IPF) exhibit a hypermotile phenotype. This study was undertaken to elucidate the molecular mechanism whereby uPAR ligation with its cognate ligand, urokinase, induces a motile phenotype in human lung fibroblasts. We found that uPAR ligation with the urokinase receptor binding domain (amino-terminal fragment) leads to enhanced migration of fibroblasts on fibronectin in a protease-independent, lipid raft-dependent manner. Ligation of uPAR with the amino-terminal fragment recruited α5β1 integrin and the acylated form of the Src family kinase, Fyn, to lipid rafts. The biological consequences of this translocation were an increase in fibroblast motility and a switch of the integrin-initiated signal pathway for migration away from the lipid raft-independent focal adhesion kinase pathway and toward a lipid raft-dependent caveolin-Fyn-Shc pathway. Furthermore, an integrin homologous peptide as well as an antibody that competes with β1 for uPAR binding have the ability to block this effect. In addition, its relative insensitivity to cholesterol depletion suggests that the interactions of α5β1 integrin and uPAR drive the translocation of α5β1 integrin-acylated Fyn signaling complexes into lipid rafts upon uPAR ligation through protein-protein interactions. This signal switch is a novel pathway leading to the hypermotile phenotype of IPF patient-derived fibroblasts, seen with uPAR ligation. This uPAR dependent, fibrotic matrix-selective, and profibrotic fibroblast phenotype may be amenable to targeted therapeutics designed to ameliorate IPF.

Functionalization of small rigid platforms with cyclic RGD peptides for targeting tumors overexpressing αvβ3-integrins

Gadolinium based Small Rigid Plaforms (SRPs) have previously demonstrated their efficiency for multimodal imaging and radiosensitization. Since the RGD sequence is well-known to be highly selective for αvβ3 integrins, a cyclic pentapeptide containing the RGD motif (cRGDfK) has been grafted onto the SRP surface. An appropriate protocol led to the grafting of two targeting ligands per nano-object. The resulting nanoparticles have demonstrated a strong association with αvβ3 integrins in comparison with cRADfK grafted SRPs as negative control. Flow cytometry and fluorescence microscopy have also been used to highlight the ability of the nanoparticles to target efficiently HEK293(β3) and U87MG cells. Finally the grafted radiosensitizing nanoparticles were intravenously injected into Nude mice bearing subcutaneous U87MG tumors and the signal observed by optical imaging was twice as high for SRP-cRGDfK compared to their negative analogue.

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) promotes glioblastoma cell chemotaxis via Lyn activation

The long-term survival of patients with glioblastoma is compromised by the proclivity for local invasion into the surrounding normal brain, escaping surgical resection and contributing to therapeutic resistance. Tumor necrosis factor-like weak inducer of apoptosis (TWEAK), a member of the tumor necrosis factor superfamily, can stimulate glioma cell invasion via binding to fibroblast growth factor-inducible 14 (Fn14) and subsequent activation of the Rho guanosine triphosphatase family member Rac1. Here, we demonstrate that TWEAK acts as a chemotactic factor for glioma cells, a potential process for driving cell invasion into the surrounding brain tissue. TWEAK exposure induced the activation of Src family kinases (SFKs), and pharmacologic suppression of SFK activity inhibited TWEAK-induced chemotactic migration. We employed a multiplexed Luminex assay and identified Lyn as a candidate SFK activated by TWEAK. Depletion of Lyn suppressed TWEAK-induced chemotaxis and Rac1 activity. Furthermore, Lyn gene expression levels increase with primary glioma tumor grade and inversely correlate with patient survival. These results show that TWEAK-induced glioma cell chemotaxis is dependent upon Lyn kinase function and, thus, provides opportunities for therapeutic targeting of this deadly disease.

Lyn facilitates glioblastoma cell survival under conditions of nutrient deprivation by promoting autophagy

Members of the Src family kinases (SFK) can modulate diverse cellular processes, including division, death and survival, but their role in autophagy has been minimally explored. Here, we investigated the roles of Lyn, a SFK, in promoting the survival of human glioblastoma tumor (GBM) cells in vitro and in vivo using lentiviral vector-mediated expression of constitutively-active Lyn (CA-Lyn) or dominant-negative Lyn (DN-Lyn). Expression of either CA-Lyn or DN-Lyn had no effect on the survival of U87 GBM cells grown under nutrient-rich conditions. In contrast, under nutrient-deprived conditions (absence of supplementation with L-glutamine, which is essential for growth of GBM cells, and FBS) CA-Lyn expression enhanced survival and promoted autophagy as well as inhibiting cell death and promoting proliferation. Expression of DN-Lyn promoted cell death. In the nutrient-deprived GBM cells, CA-Lyn expression enhanced AMPK activity and reduced the levels of pS6 kinase whereas DN-Lyn enhanced the levels of pS6 kinase. Similar results were obtained in vitro using another cultured GBM cell line and primary glioma stem cells. On propagation of the transduced GBM cells in the brains of nude mice, the CA-Lyn xenografts formed larger tumors than control cells and autophagosomes were detectable in the tumor cells. The DN-Lyn xenografts formed smaller tumors and contained more apoptotic cells. Our findings suggest that on nutrient deprivation in vitro Lyn acts to enhance the survival of GBM cells by promoting autophagy and proliferation as well as inhibiting cell death, and Lyn promotes the same effects in vivo in xenograft tumors. As the levels of Lyn protein or its activity are elevated in several cancers these findings may be of broad relevance to cancer biology.

The role of endosomal signaling triggered by metastatic growth factors in tumor progression

Within tumor microenvironment, a lot of growth factors such as hepatocyte growth factor and epidermal growth factor may induce similar signal cascade downstream of receptor tyrosine kinase (RTK) and trigger tumor metastasis synergistically. In the past decades, the intimate relationship of RTK-mediated receptor endocytosis with signal transduction was well established. In general, most RTK undergoes clathrin-dependent endocytosis and/or clathrin-independent endocytosis. The internalized receptors may sustain the signaling within early endosome, recycling to plasma membrane for subsequent ligand engagement or sorting to late endosomes/lysosome for receptor degradation. Moreover, receptor endocytosis influences signal transduction in a temporal and spatial manner for periodical and polarized cellular processes such as cell migration. The endosomal signalings triggered by various metastatic factors are quite similar in some critical points, which are essential for triggering cell migration and tumor progression. There are common regulators for receptor endocytosis including dynamin, Rab4, Rab5, Rab11 and Cbl. Moreover, many critical regulators within the RTK signal pathway such as Grb2, p38, PKC and Src were also modulators of endocytosis. In the future, these may constitute a new category of targets for prevention of tumor metastasis.

FAK-related nonkinase is a multifunctional negative regulator of pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease whose underlying molecular mechanisms are largely unknown. Herein, we show that focal adhesion kinase-related nonkinase (FRNK) plays a key role in limiting the development of lung fibrosis. Loss of FRNK function in vivo leads to increased lung fibrosis in an experimental mouse model. The increase in lung fibrosis is confirmed at the histological, biochemical, and physiological levels. Concordantly, loss of FRNK function results in increased fibroblast migration and myofibroblast differentiation and activation of signaling proteins that drive these phenotypes. FRNK-deficient murine lung fibroblasts also have an increased capacity to produce and contract matrix proteins. Restoration of FRNK expression in vivo and in vitro reverses these profibrotic phenotypes. These data demonstrate the multiple antifibrotic actions of FRNK. More important, FRNK expression is down-regulated in human IPF, and down-regulation of FRNK in normal human lung fibroblasts recapitulates the profibrotic phenotype seen in FRNK-deficient cells. The effect of loss and gain of FRNK in the experimental model, when taken together with its down-regulation in human IPF, suggests that FRNK acts as an endogenous negative regulator of lung fibrosis by repressing multiple profibrotic responses.

Targeting Src family kinases inhibits bevacizumab-induced glioma cell invasion

Anti-VEGF antibody therapy with bevacizumab provides significant clinical benefit in patients with recurrent glioblastoma multiforme (GBM). Unfortunately, progression on bevacizumab therapy is often associated with a diffuse disease recurrence pattern, which limits subsequent therapeutic options. Therefore, there is an urgent need to understand bevacizumab's influence on glioma biology and block it's actions towards cell invasion.

To explore the mechanism(s) of GBM cell invasion we have examined a panel of serially transplanted human GBM lines grown either in short-term culture, as xenografts in mouse flank, or injected orthotopically in mouse brain. Using an orthotopic xenograft model that exhibits increased invasiveness upon bevacizumab treatment, we also tested the effect of dasatinib, a broad spectrum SFK inhibitor, on bevacizumab-induced invasion.

We show that 1) activation of Src family kinases (SFKs) is common in GBM, 2) the relative invasiveness of 17 serially transplanted GBM xenografts correlates strongly with p120 catenin phosphorylation at Y228, a Src kinase site, and 3) SFK activation assessed immunohistochemically in orthotopic xenografts, as well as the phosphorylation of downstream substrates occurs specifically at the invasive tumor edge. Further, we show that SFK signaling is markedly elevated at the invasive tumor front upon bevacizumab administration, and that dasatinib treatment effectively blocked the increased invasion induced by bevacizumab.

Our data are consistent with the hypothesis that the increased invasiveness associated with anti-VEGF therapy is due to increased SFK signaling, and support testing the combination of dasatinib with bevacizumab in the clinic.

Impact of the integrin signaling adaptor protein NEDD9 on prognosis and metastatic behavior of human lung cancer

PURPOSE

In a substantial population of non-small cell lung cancer (NSCLC), expression and activation of EGF receptor (EGFR) have been reported and is regarded as a novel molecular target. A growing body of evidence has shown the signaling crosstalk between EGFR and integrins in cellular migration and invasion. NEDD9 is an integrin signaling adaptor protein composed of multiple domains serving as substrate for a variety of tyrosine kinases. In the present study, we aimed at elucidating a role of NEDD9 in the signaling crosstalk between EGFR and integrins.

EXPERIMENTAL DESIGN

Using NSCLC cell lines, we conducted immunoblotting and cellular migration/invasion assay in vitro. Next, we analyzed metastasis assays in vivo by the use of xenograft transplantation model. Finally, we retrospectively evaluated clinical samples and records of patients with NSCLCs.

RESULTS

We showed that tyrosine phosphorylation of NEDD9 was reduced by the inhibition of EGFR in NSCLC cell lines. Overexpression of constitutively active EGFR caused tyrosine phosphorylation of NEDD9 in the absence of integrin stimulation. By gene transfer and gene knockdown, we showed that NEDD9 plays a pivotal role in cell migration and invasion of those cells in vitro. Furthermore, overexpression of NEDD9 promoted lung metastasis of an NSCLC cell line in NOD/Shi-scid, IL-2Rγ(null) mice (NOG) mice. Finally, univariate and multivariate Cox model analysis of NSCLC clinical specimens revealed a strong correlation between NEDD9 expression and recurrence-free survival as well as overall survival.

CONCLUSION

Our data thus suggest that NEDD9 is a promising biomarker for the prognosis of NSCLCs and its expression can promote NSCLC metastasis.

Gliomas and seizures

Glial neoplasms account for nearly 50% of all adult primary brain tumors. They originate from glial cells in the brain and/or spinal cord and include low-grade diffuse astrocytomas, anaplastic-astrocytomas, and glioblastomas. Of all brain tumors, glioblastoma multiforme (GBM) is the most aggressive and is characterized by rapid glial cell growth, resistance to radio- and chemo- therapies, and relentless infiltration and spreading throughout the central nervous system (CNS). In glioblastomas, primary tumor growth and CNS invasion are associated with the activation of complex structural molecular and metabolic changes within the tumor tissue, which profoundly affect the surrounding neuronal networks and may in part explain induction of epilepsy. In fact, epileptic seizures are very common among patients with glial tumors, reaching nearly 50% in glioblastoma patients and almost 90% in low-grade astrocytomas. The overall hypothesis presented here discusses the possibility that the aberrant tumor cell metabolism may act directly on neuronal network, and this leads to seizure susceptibility. Further invasion and growth of the malignant glial cells exacerbate this initial pathologic state which promotes recurrent seizures (epileptogenesis).

Neuronal Wiskott-Aldrich syndrome protein (N-WASP) is critical for formation of α-smooth muscle actin filaments during myofibroblast differentiation

Myofibroblasts are implicated in pathological stromal responses associated with lung fibrosis. One prominent phenotypic marker of fully differentiated myofibroblasts is the polymerized, thick cytoplasmic filaments containing newly synthesized α-smooth muscle actin (α-SMA). These α-SMA-containing cytoplasmic filaments are important for myofibroblast contractility during tissue remodeling. However, the molecular mechanisms regulating the formation and maturation of α-SMA-containing filaments have not been defined. This study demonstrates a critical role for neuronal Wiskott-Aldrich syndrome protein (N-WASP) in regulating the formation of α-SMA-containing cytoplasmic filaments during myofibroblast differentiation and in myofibroblast contractility. Focal adhesion kinase (FAK) is activated by transforming growth factor-β1 (TGF-β1) and is required for phosphorylation of tyrosine residue 256 (Y256) of N-WASP. Phosphorylation of Y256 of N-WASP is essential for TGF-β1-induced formation of α-SMA-containing cytoplasmic filaments in primary human lung fibroblasts. In addition, we demonstrate that actin-related protein (Arp) 2/3 complex is downstream of N-WASP and mediates the maturation of α-SMA-containing cytoplasmic filaments. Together, this study supports a critical role of N-WASP in integrating FAK and Arp2/3 signaling to mediate formation of α-SMA-containing cytoplasmic filaments during myofibroblast differentiation and maturation.

Functions of the Lyn tyrosine kinase in health and disease

Src family kinases such as Lyn are important signaling intermediaries, relaying and modulating different inputs to regulate various outputs, such as proliferation, differentiation, apoptosis, migration and metabolism. Intriguingly, Lyn can mediate both positive and negative signaling processes within the same or different cellular contexts. This duality is exemplified by the B-cell defect in Lyn-/- mice in which Lyn is essential for negative regulation of the B-cell receptor; conversely, B-cells expressing a dominant active mutant of Lyn (Lynup/up) have elevated activities of positive regulators of the B-cell receptor due to this hyperactive kinase. Lyn has well-established functions in most haematopoietic cells, viz. progenitors via influencing c-kit signaling, through to mature cell receptor/integrin signaling, e.g. erythrocytes, platelets, mast cells and macrophages. Consequently, there is an important role for this kinase in regulating hematopoietic abnormalities. Lyn is an important regulator of autoimmune diseases such as asthma and psoriasis, due to its profound ability to influence immune cell signaling. Lyn has also been found to be important for maintaining the leukemic phenotype of many different liquid cancers including acute myeloid leukaemia (AML), chronic myeloid leukaemia (CML) and B-cell lymphocytic leukaemia (BCLL). Lyn is also expressed in some solid tumors and here too it is establishing itself as a potential therapeutic target for prostate, glioblastoma, colon and more aggressive subtypes of breast cancer. LAY To relay information, a cell uses enzymes that put molecular markers on specific proteins so they interact with other proteins or move to specific parts of the cell to have particular functions. A protein called Lyn is one of these enzymes that regulate information transfer within cells to modulate cell growth, survival and movement. Depending on which type of cell and the source of the information input, Lyn can positively or negatively regulate the information output. This ability of Lyn to be able to both turn on and turn off the relay of information inside cells makes it difficult to fully understand its precise function in each specific circumstance. Lyn has important functions for cells involved in blood development, including different while blood cells as well as red blood cells, and in particular for the immune cells that produce antibodies (B-cells), as exemplified by the major B-cell abnormalities that mice with mutations in the Lyn gene display. Certain types of leukaemia and lymphoma appear to have too much Lyn activity that in part causes the characteristics of these diseases, suggesting it may be a good target to develop new anti-leukaemia drugs. Furthermore, some specific types, and even specific subtypes, of solid cancers, e.g. prostate, brain and breast cancer can also have abnormal regulation of Lyn. Consequently, targeting this protein in these cancers could also prove to be beneficial.

Lyn kinase mediates cell motility and tumor growth in EGFRvIII-expressing head and neck cancer

PURPOSE

EGF receptor variant III (EGFRvIII) has been detected in several cancers in which tumors expressing this truncated growth factor receptor show more aggressive behavior. The molecular mechanisms that contribute to EGFRvIII-mediated tumor progression that are amenable to targeted therapy are incompletely understood. The present study aimed to better define the role of Src family kinases (SFKs) in EGFRvIII-mediated cell motility and tumor growth of head and neck squamous cell carcinomas (HNSCC).

EXPERIMENTAL DESIGN

HNSCC models expressing EGFRvIII were treated with dasatinib, a pharmacologic inhibitor of SFKs.

RESULTS

SFK inhibition significantly decreased cell proliferation, migration, and invasion of EGFRvIII-expressing HNSCC cells. Administration of dasatinib to mice bearing EGFRvIII-expressing HNSCC xenografts resulted in a significant reduction of tumor volume compared with controls. Immunoprecipitation with anti-c-Src, Lyn, Fyn, and Yes antibodies followed by immunoblotting for phosphorylation of the SFK activation site (Y416) showed specific activation of Lyn kinase in EGFRvIII-expressing HNSCC cell lines and human HNSCC tumor specimens. Selective inhibition of Lyn using siRNA decreased cell migration and invasion of EGFRvIII-expressing HNSCCs compared with vector control cells.

CONCLUSIONS

These findings show that Lyn mediates tumor progression of EGFRvIII-expressing HNSCCs in which strategies to inhibit SFK may represent an effective therapeutic strategy.

Potentiation of platelet-derived growth factor receptor-β signaling mediated by integrin-associated MFG-E8

OBJECTIVE

Pericytes/pericyte precursors produce milk fat globule-associated protein with epidermal growth factor and factor VIII-like domains (MFG-E8) in vivo, and this α(v) integrin ligand enhances angiogenesis in tumors and in oxygen-induced retinopathy in mice. Inhibition of MFG-E8 production or function attenuates platelet-derived growth factor-BB (PDGF-BB)-induced migration of pericyte/pericyte precursor-like 10T1/2 cells in vitro. Herein, we describe mechanisms by which MFG-E8 modulates PDGF-BB:PDGF receptor β (PDGFRβ) signaling in 10T1/2 cells.

METHODS AND RESULTS

Small interfering RNA depletion of MFG-E8 from 10T1/2 cells or antibody inhibition of MFG-E8 action enhanced PDGF-BB-dependent degradation of PDGFRβ and attenuated signaling. Coimmunoprecipitation revealed transient association of MFG-E8 with PDGFRβ in PDGF-BB-treated 10T1/2 cells and reduced PDGFRβ-focal adhesion kinase association in MFG-E8-depleted cells. Confocal microscopy demonstrated that MFG-E8 binding to 10T1/2 cells was RGD motif and α(v) dependent but PDGF-BB treatment independent, whereas colocalization of MFG-E8 with PDGFRβ was enhanced by PDGF-BB. Ubiquitination of PDGFRβ was also increased in MFG-E8 small interfering RNA-transfected cells.

CONCLUSION

Integrin α(v)-bound MFG-E8 associates with PDGFRβ and focal adhesion kinase after PDGF-BB treatment, results in cell surface retention of PDGFRβ, delays receptor degradation, potentiates downstream signaling, and enhances migration of 10T1/2 cells. MFG-E8 may promote angiogenesis, in part, via cell autonomous actions on pericytes or pericyte precursors that result in enhanced PDGF-BB:PDGFRβ signaling mediated via integrin-growth factor receptor cross-talk.

Tumorigenesis and prognostic role of hepatoma-derived growth factor in human gliomas

Hepatoma-derived growth factor (HDGF) is a neurotrophic factor found in mouse spinal cord and hippocampal neurons. In various malignant tumors, the role of HDGF in tumor progression and its use as a diagnostic biomarker or therapeutic target have been extensively explored. However, the prognostic function and mitogenic role of HDGF in gliomagenesis are yet to be verified. In this study, we found a significant incidence of HDGF prevalence between the different pathological types and stages of glioma in 105 patients. We also found a prognostic significance in 41 glioblastoma multiforme (GBM) patients, with prevalence of nuclear HDGF predicting short survival of patients with GBM after surgery. To delineate the mitogenic role of HDGF in gliomagenesis, an adenoviral-expressed HDGF small interfering RNA (Ad-HDGF siRNA) was used to knock down expression of nuclear HDGF. After knocking down nuclear HDGF expression in human GBM cells, cell growth and cell invasion and induction on apoptosis by caspase-3 activation were significantly inhibited. We conclude that HDGF is a mitogenic growth factor in glioma progression and can be a useful prognostic marker for GBM and therapeutic target for clinical management of glioma in the future.

Downregulation of FIP200 induces apoptosis of glioblastoma cells and microvascular endothelial cells by enhancing Pyk2 activity

The expression of focal adhesion kinase family interacting protein of 200-kDa (FIP200) in normal brain is limited to some neurons and glial cells. On immunohistochemical analysis of biopsies of glioblastoma tumors, we detected FIP200 in the tumor cells, tumor-associated endothelial cells, and occasional glial cells. Human glioblastoma tumor cell lines and immortalized human astrocytes cultured in complete media also expressed FIP200 as did primary human brain microvessel endothelial cells (MvEC), which proliferate in culture and resemble reactive endothelial cells. Downregulation of endogenous expression of FIP200 using small interfering RNA resulted in induction of apoptosis in the human glioblastoma tumor cells, immortalized human astrocytes, and primary human brain MvEC. It has been shown by other investigators using cells from other tissues that FIP200 can interact directly with, and inhibit, proline-rich tyrosine kinase 2 (Pyk2) and focal adhesion kinase (FAK). In the human glioblastoma tumor cells, immortalized human astrocytes, and primary human brain MvEC, we found that downregulation of FIP200 increased the activity of Pyk2 without increasing its expression, but did not affect the activity or expression of FAK. Coimmunoprecipitation and colocalization studies indicated that the endogenous FIP200 was largely associated with Pyk2, rather than FAK, in the glioblastoma tumor cells and brain MvEC. Moreover, the pro-apoptotic effect of FIP200 downregulation was inhibited significantly by a TAT-Pyk2-fusion protein containing the Pyk2 autophosphorylation site in these cells. In summary, downregulation of endogenous FIP200 protein in glioblastoma tumor cells, astrocytes, and brain MvECs promotes apoptosis, most likely due to the removal of a direct interaction of FIP200 with Pyk2 that inhibits Pyk2 activation, suggesting that FIP200 expression may be required for the survival of all three cell types found in glioblastoma tumors.

Differential transformation capacity of Src family kinases during the initiation of prostate cancer

Src family kinases (SFKs) are pleiotropic activators that are responsible for integrating signal transduction for multiple receptors that regulate cellular proliferation, invasion, and metastasis in a variety of human cancers. Independent groups have identified increased expression of individual SFK members during prostate cancer progression, raising the question of whether SFKs display functional equivalence. Here, we show that Src kinase, followed by Fyn kinase and then Lyn kinase, exhibit ranked tumorigenic potential during both paracrine-induced and cell-autonomous-initiated prostate cancer. This quantitative variation in transformation potential appears to be regulated in part by posttranslational palmitoylation. Our data indicate that development of inhibitors against specific SFK members could provide unique targeted therapeutic strategies.

Cyclic RGD functionalized gold nanoparticles for tumor targeting

Integrin α(v)β(3) is an adhesion molecule involved in physiological and pathological angiogenesis as well as tumor invasion and metastasis. Therefore, it is considered an important target for molecular imaging and delivery of therapeutics for cancer, and there is a strong interest in developing novel agents interacting with this protein. Nevertheless, the interaction of individual ligands is often still weak for efficient tumor targeting, and many research groups have synthesized multivalent displays in order to overcome this problem. Gold nanoparticles can be considered a smart platform for polyvalent presentation on account of their globular shape, tunable size, facile surface chemistry, and biocompatibility. Moreover, their unique physical properties render gold nanoparticles ideal candidates for tumor diagnosis and therapy. Here, we report the synthesis and characterization of gold nanoparticles functionalized with cRGD integrin ligand and their employment for targeting human cancer cells expressing α(v)β(3) integrin.

Targeting SRC in glioblastoma tumors and brain metastases: rationale and preclinical studies

Glioblastoma (GBM) is an extremely aggressive, infiltrative tumor with a poor prognosis. The regulatory approval of bevacizumab for recurrent GBM has confirmed that molecularly targeted agents have potential for GBM treatment. Preclinical data showing that SRC and SRC-family kinases (SFKs) mediate intracellular signaling pathways controlling key biologic/oncogenic processes provide a strong rationale for investigating SRC/SFK inhibitors, e.g., dasatinib, in GBM and clinical studies are underway. The activity of these agents against solid tumors suggests that they may also be useful in treating brain metastases. This article reviews the potential for using SRC/SFK inhibitors to treat GBM and brain metastases.

Tumor necrosis factor-alpha regulates the Hypocretin system via mRNA degradation and ubiquitination

Recent studies recognize that Hypocretin system (also known as Orexin) plays a critical role in sleep/wake disorders and feeding behaviors. However, little is known about the regulation of the Hypocretin system. It is also known that tumor necrosis factor alpha (TNF-α) is involved in the regulation of sleep/wake cycle. Here, we test our hypothesis that the Hypocretin system is regulated by TNF-α. Prepro-Hypocretin and Hypocretin receptor 2 (HcrtR2) can be detected at a very low level in rat B35 neuroblastoma cells. In response to TNF-α, Prepro-Hypocretin mRNA and protein levels are down-regulated, and also HcrtR2 protein level is down-regulated in B35 cells. To investigate the mechanism, exogenous rat Prepro-Hypocretin and rat HcrtR2 were overexpressed in B35 cells. In response to TNF-α, protein and mRNA of Prepro-Hypocretin are significantly decreased (by 93% and 94%, respectively), and the half-life of Prepro-Hypocretin mRNA is decreased in a time- and dose-dependent manner. The level of HcrtR2 mRNA level is not affected by TNF-α treatment; however, HcrtR2 protein level is significantly decreased (by 86%) through ubiquitination in B35 cells treated with TNF-α. Downregulation of cellular inhibitor of apoptosis protein-1 and -2 (cIAP-1 and -2) abrogates the HcrtR2 ubiquitination induced by TNF-α. The control green fluorescent protein (GFP) expression is not affected by TNF-α treatment. These studies demonstrate that TNF-α can impair the function of the Hypocretin system by reducing the levels of both Prepro-Hypocretin and HcrtR2.

Is HCMV a tumor promoter?

Human cytomegalovirus (HCMV) is a beta-herpesvirus that causes persistent infection in humans and can cause severe disease in fetuses and immunocompromised individuals. Although HCMV is not currently causally implicated in human cancer, emerging evidence suggests that HCMV infection and expression may be specifically associated with human malignancies including malignant glioma, colon, and prostate cancer. In addition, multiple investigators have demonstrated that HCMV can dysregulate signaling pathways involved in initiation and promotion of malignancy, including tumor suppressor, mitogenic signaling, inflammatory, immune regulation, angiogenesis and invasion, and epigenetic mechanisms. This review highlights some of the recent evidence that HCMV might play a role in modulating the tumor microenvironment as well as in the initiation and promotion of tumor cells themselves.

Cooperative expression of junctional adhesion molecule-C and -B supports growth and invasion of glioma

Brain invasion is a biological hallmark of glioma that contributes to its aggressiveness and limits the potential of surgery and irradiation. Deregulated expression of adhesion molecules on glioma cells is thought to contribute to this process. Junctional adhesion molecules (JAMs) include several IgSF members involved in leukocyte trafficking, angiogenesis, and cell polarity. They are expressed mainly by endothelial cells, white blood cells, and platelets. Here, we report JAM-C expression by human gliomas, but not by their normal cellular counterpart. This expression correlates with the expression of genes involved in cytoskeleton remodeling and cell migration. These genes, identified by a transcriptomic approach, include poliovirus receptor and cystein-rich 61, both known to promote glioma invasion, as well as actin filament associated protein, a c-Src binding partner. Gliomas also aberrantly express JAM-B, a high affinity JAM-C ligand. Their interaction activates the c-Src proto-oncogene, a central upstream molecule in the pathways regulating cell migration and invasion. In the tumor microenvironment, this co-expression may thus promote glioma invasion through paracrine stimuli from both tumor cells and endothelial cells. Accordingly, JAM-C/B blocking antibodies impair in vivo glioma growth and invasion, highlighting the potential of JAM-C and JAM-B as new targets for the treatment of human gliomas.

The pathobiology of glioma tumors

The ongoing characterization of the genetic and epigenetic alterations in the gliomas has already improved the classification of these heterogeneous tumors and enabled the development of rodent models for analysis of the molecular pathways underlying their proliferative and invasive behavior. Effective application of the targeted therapies that are now in development will depend on pathologists' ability to provide accurate information regarding the genetic alterations and the expression of key receptors and ligands in the tumors. Here we review the mechanisms that have been implicated in the pathogenesis of the gliomas and provide examples of the cooperative nature of the pathways involved, which may influence the initial therapeutic response and the potential for development of resistance.