Redox-sensitive transactivation of epidermal growth factor receptor by tumor necrosis factor confers the NF-kappa B activation

Combined genetic and chemical screens indicate protective potential for EGFR inhibition to cardiomyocytes under hypoxia

The return of blood flow to ischemic heart after myocardial infarction causes ischemia-reperfusion injury. There is a clinical need for novel therapeutic targets to treat myocardial ischemia-reperfusion injury. Here we screened for targets for the treatment of ischemia-reperfusion injury using a combination of shRNA and drug library analyses in HL-1 mouse cardiomyocytes subjected to hypoxia and reoxygenation. The shRNA library included lentiviral constructs targeting 4625 genes and the drug library 689 chemical compounds approved by the Food and Drug Administration (FDA). Data were analyzed using protein-protein interaction and pathway analyses. EGFR inhibition was identified as a cardioprotective mechanism in both approaches. Inhibition of EGFR kinase activity with gefitinib improved cardiomyocyte viability in vitro. In addition, gefitinib preserved cardiac contractility in zebrafish embryos exposed to hypoxia-reoxygenation in vivo. These findings indicate that the EGFR inhibitor gefitinib is a potential candidate for further studies of repurposing the drug for the treatment of myocardial infarction.

Pyrogen retention: Comparison of the novel medium cut-off (MCO) membrane with other dialyser membranes

Haemodialysis effectively removes small solutes and smaller-sized middle molecules from the blood; however, the clearance of larger middle molecules, which have been associated with negative effects, is poor. The novel medium cut-off (MCO) dialysis membrane has larger pore sizes and a more open structure than other high-flux membranes, providing improved removal of larger middle molecules while retaining albumin. However, larger pore sizes may potentially increase permeability to pyrogens, including endotoxins and other bacterial contaminants, that could be present in the dialysis fluid. In this study, we tested the capacity of low-flux, high-flux, MCO and high cut-off dialyser membranes with different pore sizes to prevent pyrogens crossing from dialysate to the blood side in a closed-loop test system, differentiating among lipopolysaccharides, peptidoglycans and bacterial DNA using a toll-like receptor assay. Even though the bacterial contamination levels in our test system exceeded the acceptable pyrogen dose for standard dialysis fluid, levels of lipopolysaccharides, peptidoglycans and bacterial DNA in the blood-side samples were too low to identify potential differences in pyrogen permeability among the membranes. Our results suggest that MCO membranes are suitable for haemodialysis using ISO standard dialysis fluid quality, and retain endotoxins at a similar level as other membranes.

The expression status of TRX, AR, and cyclin D1 correlates with clinicopathological characteristics and ER status in breast cancer

Background

The ER signaling pathway plays a critical role in breast cancer. ER signaling pathway-related proteins, such as TRX, AR, and cyclin D1, may have an important function in breast cancer. However, the ways that they influence breast cancer development and progression are still unclear.

Patients and methods

A total of 101 Chinese female patients diagnosed with invasive ductal breast adenocarcinoma were retrospectively enrolled in the study. The expression levels of TRX, AR, and cyclin D1 were detected by immunohistochemistry and analyzed via correlation with clinicopathological characteristics and the expression status of ER, PR, and HER2.

Results

The expression status of TRX, AR, and cyclin D1 was not associated with the patient’s age, menopausal status, tumor size, or histological differentiation (P>0.05), but was positively correlated with ER and PR (P<0.001, respectively). Most (66/76, 86.8) TRX-positive patients were also HER2-positive (P=0.003). Of AR- or cyclin D1-positive patients, most had relatively earlier I–II tumor stage (P=0.005 and P=0.047, respectively) and no metastatic lymph node involvement (P=0.008 and P=0.005, respectively).

Conclusion

TRX was found to be positively correlated with ER and PR expression, whereas it was negatively correlated with HER2 expression. In addition, we found that the positive expression of AR and cyclin D1 was correlated with lower TNM stage and fewer metastatic lymph nodes, and it was more common in ER-positive breast cancer than in the basal-like subtype. This may indicate that AR and cyclin D1 are good predictive and prognostic factors and closely interact with ER signaling pathway. Further studies will be necessary to investigate the response and clinical outcomes of treatment targeting TRX, AR, and cyclin D1.

S100A4 and its role in metastasis – simulations of knockout and amplification of epithelial growth factor receptor and matrix metalloproteinases

The calcium-binding signalling protein S100A4 enhances metastasis in a variety of cancers. Despite a wealth of data available, the molecular mechanism by which S100A4 drives metastasis is unknown. Integration of the current knowledge defies straightforward intuitive interpretation and requires computer-aided approaches to represent the complexity emerging from cross-regulating species. Here we carried out a systematic sensitivity analysis of the S100A4 signalling network in order to identify key control parameters for efficient therapeutic intervention. Our approach only requires limited details of the molecular interactions and permits a straightforward integration of the available experimental information. By integrating the available knowledge, we investigated the effects of combined inhibition of signalling pathways. Through selective knockout or inhibition of the network components, we show that the interaction between epidermal growth factor receptor (EGFR) and S100A4 modulates the sensitivity of angiogenesis development to matrix metalloproteinases (MMPs) activity. We also show that, in cells that express high EGFR, MMP inhibitors are not expected to be useful in tumours if high activity of S100A4 is present.

Lung injury and lung cancer caused by cigarette smoke-induced oxidative stress: Molecular mechanisms and therapeutic opportunities involving the ceramide-generating machinery and epidermal growth factor receptor

Chronic obstructive pulmonary disease (COPD) and lung cancer are frequently caused by tobacco smoking. However, these diseases present opposite phenotypes involving redox signaling at the cellular level. While COPD is characterized by excessive airway epithelial cell death and lung injury, lung cancer is caused by uncontrolled epithelial cell proliferation. Notably, epidemiological studies have demonstrated that lung cancer incidence is significantly higher in patients who have preexisting emphysema/lung injury. However, the molecular link and common cell signaling events underlying lung injury diseases and lung cancer are poorly understood. This review focuses on studies of molecular mechanism(s) underlying smoking-related lung injury (COPD) and lung cancer. Specifically, the role of the ceramide-generating machinery during cigarette smoke-induced oxidative stress leading to both apoptosis and proliferation of lung epithelial cells is emphasized. Over recent years, it has been established that ceramide is a sphingolipid playing a major role in lung epithelia structure/function leading to lung injury in chronic pulmonary diseases. However, new and unexpected findings draw attention to its potential role in lung development, cell proliferation, and tumorigenesis. To address this dichotomy in detail, evidence is presented regarding several protein targets, including Src, p38 mitogen-activated protein kinase, and neutral sphingomyelinase 2, the major sphingomyelinase that controls ceramide generation during oxidative stress. Furthermore, their roles are presented not only in apoptosis and lung injury but also in enhancing cell proliferation, lung cancer development, and resistance to epidermal growth factor receptor-targeted therapy for treating lung cancer.

Oligosaccharide G19 inhibits U-87 MG human glioma cells growth in vitro and in vivo by targeting epidermal growth factor (EGF) and activating p53/p21 signaling

G19 is a novel homogeneous sulfated oligosaccharide, prepared from Grateloupia filicina. In the present study, we first reported that oligosaccharide G19 exhibited a dose- and time-dependent anti-proliferation effect against U-87 malignant gliomas (MG) human glioma cells. Further studies indicated that G19 strongly bound to epidermal growth factor (EGF), suppressed EGF receptor phosphorylation and interrupted the phosphatidylinositol-3 kinase/Akt pathway in the cancer cells. Moreover, G19 elevated intracellular reactive oxygen species levels and caused endogenous DNA damage. These actions were associated with activation of ataxia-telangiectasia-mutated/checkpoint kinase 2 pathway. The downregulation of MDM2 with stabilizing p53 and the nuclear location of p21 were induced by G19 to cause cell cycle arrest and apoptosis to some extent. Meanwhile, intrinsic mitochondrial pathway and extrinsic death receptor pathway were involved in G19-mediated apoptosis. Pretreatment with free radical scavenger N-acetyl-l-cysteine nearly completely inversed G19-induced cell growth inhibition, cell cycle arrest and apoptosis in U-87 MG cells. Importantly, G19 could inhibit the growth of U-87 MG tumor cells xenograft in nude mice. The results suggested that G19 could be served as a new targeting drug candidate for human glioma treatment.

Oncogenic K-Ras and loss of Smad4 mediate invasion by activating an EGFR/NF-κB Axis that induces expression of MMP9 and uPA in human pancreas progenitor cells

Activating K-Ras mutations and inactivating mutations of Smad4 are two common genetic alterations that occur in the development and progression of pancreatic ductal adenocarcinomas (PDAC). To further study the individual and combinatorial roles of these two mutations in the pathogenesis of PDAC, immortalized human pancreas nestin postive cells (HPNE) were genetically modified by either expressing oncogenic K-Ras (HPNE/K-Ras), by shRNA knock down of Smad4 (HPNE/ShSmad4) or by creating both alterations in the same cell line (HPNE/K-Ras/ShSmad4). We previously found that expression of oncogenic K-Ras caused an increase in expression of EGFR and loss of Smad4 further enhanced the up regulation in expression of EGFR and that this increase in EGFR was sufficient to induce invasion. Here we further investigated the mechanism that links mutational alterations and EGFR expression with invasion. The increase in EGFR signaling was associated with up regulation of MMP9 and uPA protein and activity. Moreover, the increase in EGFR signaling promoted a nuclear translocation and binding of RelA (p65), a subunit of NF-κB, to the promoters of both MMP-9 and uPA. Treatment of HPNE/K-Ras/ShSmad4 cells with an inhibitor of EGFR reduced EGF-mediated NF-κB nuclear translocation and inhibitors of either EGFR or NF-κB reduced the increase in MMP-9 or uPA expression. In conclusion, this study provides the mechanism of how a combination of oncogenic K-Ras and loss of Smad4 causes invasion and provides the basis for new strategies to inhibit metastases.

Role of thioredoxin in lung disease

Thioredoxin system is a ubiquitous thiol oxidoreductase system that regulates cellular reduction/oxidation (redox) status. It includes thioredoxin (Trx), thioredoxin reductase (TrxR), and NADPH. Trx plays an essential role in cell function by limiting oxidative stress directly via antioxidant effects and indirectly by proteins interaction with key signal transduction molecules. A variety of signaling molecules have been implicated in the cytoprotection conferred by Trx, such as autophagic proteins, p38 mitogen-activated protein kinase, nuclear factor-κB, phosphatidylinositol 3-kinase. Recent studies indicated that Trx may contribute to the pathogenesis of COPD, asthma and lung injury. Enhanced Trx expression or application of recombinant Trx afforded protection in preclinical models of pulmonary tissue injury, which suggested Trx may be used in future therapeutic applications. The focus of this review is on the significance of Trx in various pulmonary diseases, which as a potential therapeutic strategy to protect against oxidative stress and inflammation.

p38 mitogen-activated protein kinase-dependent transactivation of ErbB receptor family: a novel common mechanism for stress-induced IRS-1 serine phosphorylation and insulin resistance

OBJECTIVE

Stress stimuli such as tumor necrosis factor (TNF) have been shown to induce insulin receptor substrate (IRS)-1 serine phosphorylation and insulin resistance by transactivation of ErbB receptors. We aimed at elucidating the potential role of p38 mitogen-activated protein kinase (p38MAPK) in mediating stress-induced ErbB receptors activation.

RESEARCH DESIGN AND METHODS

p38MAPK effect on ErbBs transactivation and insulin signaling was assessed in Fao or HepG2 cells, exposed to stress stimuli, and on metabolic parameters in ob/ob and C57/BL6 mice.

RESULTS

High-fat diet-fed mice and ob/ob mice exhibited elevated hepatic p38MAPK activation associated with glucose intolerance and hyperinsulinemia. Liver expression of dominant-negative (DN)-p38MAPKα in ob/ob mice reduced fasting insulin levels and improved glucose tolerance, whereas C57/BL6 mice overexpressing wild-type p38MAPKα exhibited enhanced IRS-1 serine phosphorylation and reduced insulin-stimulated IRS-1 tyrosine phosphorylation. Fao or HepG2 cells exposed to TNF, anisomycin, or sphingomyelinase demonstrated rapid transactivation of ErbB receptors leading to PI3-kinase/Akt activation and IRS-1 serine phosphorylation. p38MAPK inhibition either by SB203580, by small interfering RNA, or by DN-p38MAPKα decreased ErbB receptors transactivation and IRS-1 serine phosphorylation and partially restored insulin-stimulated IRS-1 tyrosine phosphorylation. When cells were incubated with specific ErbB receptors antagonists or in cells lacking ErbB receptors, anisomycin- and TNF-induced IRS-1 serine phosphorylation was attenuated, despite intact p38MAPK activation. The stress-induced p38MAPK activation leading to ErbB receptors transactivation was associated with intracellular reactive oxygen species generation and was attenuated by treatment with antioxidants.

CONCLUSIONS

Hepatic p38MAPK is activated following various stress stimuli. This event is upstream to ErbB receptors transactivation and plays an important role in stress-induced IRS-1 serine phosphorylation and insulin resistance.

The epidermal growth factor receptor mediates tumor necrosis factor-alpha-induced activation of the ERK/GEF-H1/RhoA pathway in tubular epithelium

Tumor necrosis factor (TNF)-α induces cytoskeleton and intercellular junction remodeling in tubular epithelial cells; the underlying mechanisms, however, are incompletely explored. We have previously shown that ERK-mediated stimulation of the RhoA GDP/GTP exchange factor GEF-H1/Lfc is critical for TNF-α-induced RhoA stimulation. Here we investigated the upstream mechanisms of ERK/GEF-H1 activation. Surprisingly, TNF-α-induced ERK and RhoA stimulation in tubular cells were prevented by epidermal growth factor receptor (EGFR) inhibition or silencing. TNF-α also enhanced phosphorylation of the EGFR. EGF treatment mimicked the effects of TNF-α, as it elicited potent, ERK-dependent GEF-H1 and RhoA activation. Moreover, EGF-induced RhoA activation was prevented by GEF-H1 silencing, indicating that GEF-H1 is a key downstream effector of the EGFR. The TNF-α-elicited EGFR, ERK, and RhoA stimulation were mediated by the TNF-α convertase enzyme (TACE) that can release EGFR ligands. Further, EGFR transactivation also required the tyrosine kinase Src, as Src inhibition prevented TNF-α-induced activation of the EGFR/ERK/GEF-H1/RhoA pathway. Importantly, a bromodeoxyuridine (BrdU) incorporation assay and electric cell substrate impedance-sensing (ECIS) measurements revealed that TNF-α stimulated cell growth in an EGFR-dependent manner. In contrast, TNF-α-induced NFκB activation was not prevented by EGFR or Src inhibition, suggesting that TNF-α exerts both EGFR-dependent and -independent effects. In summary, in the present study we show that the TNF-α-induced activation of the ERK/GEF-H1/RhoA pathway in tubular cells is mediated through Src- and TACE-dependent EGFR activation. Such a mechanism could couple inflammatory and proliferative stimuli and, thus, may play a key role in the regulation of wound healing and fibrogenesis.

Thioredoxin regulates cell cycle via the ERK1/2-cyclin D1 pathway

Thioredoxin (TRX) is a key component of redox regulation and has been indicated to play an essential role in cell survival and growth. Here, we investigated the molecular mechanism of TRX in the regulation of cell survival and growth by using RNA interference (RNAi) in A549 lung cancer and MCF7 breast cancer cells. TRX knockdown did not significantly increase the basal level of cell death without exposure to stress, but CDDP-induced cell death was enhanced. Meanwhile, TRX knockdown resulted in significant cell-cycle arrest at the G(1) phase. Cyclin D1 expression was reduced by TRX knockdown at the protein and mRNA levels. TRX knockdown caused suppression of activation of the cyclin D1 promoter through elements including AP-1. TRX knockdown also reduced the levels of phosphorylated ERK1/2 and the nuclear translocation of ERK 1/2 induced by EGF. These results suggest that TRX is an important regulator of the cell cycle in the G(1) phase via cyclin D1 transcription and the ERK/AP-1 signaling pathways.

Pressure activates epidermal growth factor receptor leading to the induction of iNOS via NFkappaB and STAT3 in human proximal tubule cells

Ureteral obstruction leads to increased pressure and inducible nitric oxide synthase (iNOS) expression. This study examined the involvement of epidermal growth factor (EGF) receptor (EGFR), nuclear factor-kappaB (NFkappaB), and signal transducers and activators of transcription 3 (STAT3) in iNOS induction in human proximal tubule (HKC-8) cells in response to pressure or EGF. HKC-8 cells were subjected to 60 mmHg pressure or treated with EGF for 0-36 h. iNOS was more rapidly induced in response to EGF than pressure. The addition of EGFR, NFkappaB, and STAT3 inhibitors significantly suppressed pressure- or EGF-stimulated iNOS mRNA and protein expression. Analysis of the activated states of EGFR, NFkappaB p65, and STAT3 after exposure to both stimuli demonstrated phosphorylation within 2.5 min. Anti-EGF antibody inhibited iNOS induction in pressurized HKC-8 cells, providing evidence that endogenous EGF mediates the response to pressure. In ureteral obstruction, when pressure is elevated, phosphorylated EGFR was detected in the apical surface of the renal tubules, validating the in vitro findings. These data indicate that EGFR, NFkappaB, and STAT3 are required for human iNOS gene induction in response to pressure or EGF, indicating a similar mechanism of activation.

A conditional transposon-based insertional mutagenesis screen for genes associated with mouse hepatocellular carcinoma

We describe a system that permits conditional mobilization of a Sleeping Beauty (SB) transposase allele by Cre recombinase to induce cancer specifically in a tissue of interest. To demonstrate its potential for developing tissue-specific models of cancer in mice, we limit SB transposition to the liver by placing Cre expression under the control of an albumin enhancer/promoter sequence and screen for hepatocellular carcinoma (HCC)-associated genes. From 8,060 nonredundant insertions cloned from 68 tumor nodules and comparative analysis with data from human HCC samples, we identify 19 loci strongly implicated in causing HCC. These encode genes, such as EGFR and MET, previously associated with HCC and others, such as UBE2H, that are potential new targets for treating this neoplasm. Our system, which could be modified to drive transposon-based insertional mutagenesis wherever tissue-specific Cre expression is possible, promises to enhance understanding of cancer genomes and identify new targets for therapeutic development.

Hemolysate-induced expression of intercellular adhesion molecule-1 and monocyte chemoattractant protein-1 expression in cultured brain microvascular endothelial cells via through ROS-dependent NF-kappaB pathways

In order to determine the possible effects of hemolysate on brain microvascular endothelial cells (BMECs), we examined the effects of hemolysate on the expression of intercellular adhesion molecule-1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1), generation of reactive oxygen species (ROS), and NF-kappaB activation in rat BMECs. Hemolysate induced the expression of ICAM-1 and MCP-1 in endothelial cells. In addition, hemolysate stimulated nuclear translocation of the p65 subunit of NF-kappaB, and NF-kappaB DNA-binding activity in BMECs. Furthermore, hemolysate increased ROS generation, and hemolysate-induced ICAM-1and MCP-1 expression and NF-kappaB activation were abrogated in the presence of the direct scavenger of ROS. Taken together, our results indicate that hemolysate can induce inflammatory responses that increase expression of ICAM-1 and MCP-1, through ROS-dependent NF-kappaB activation in BMECs.

Nuclear factor-kB tumor expression predicts response and survival in irinotecan-refractory metastatic colorectal cancer treated with cetuximab-irinotecan therapy

PURPOSE

NF-kB expression has been shown to be responsible for resistance to antineoplastic agents and it also plays a part in the activation of the epidermal growth factor receptor downstream signaling pathway in colorectal tumors. The aim of our analysis was to investigate a correlation between NF-kB expression, response rate, time to progression, and survival in advanced colorectal cancer patients receiving cetuximab and irinotecan.

PATIENTS AND METHODS

We analyzed retrospectively the immunoreactivity for NF-kB in irinotecan-refractory patients receiving cetuximab and irinotecan. Results Seventy-six patients were analyzed. Cetuximab and irinotecan were administered as second-line chemotherapy in 19 patients and after > or = two lines of chemotherapy in the remaining 57 patients. We observed a partial response (PR) in 16 patients for an overall response rate of 24%. Thirty-two patients (48%) experienced progressive disease; median time to progression (TTP) was 3.6 months and median overall survival was 10.3 months. NF-kB was positive in 46 patients (60%). All main clinical characteristics were well balanced between NF-kB-positive and NF-kB-negative patients. The response rate was 10% (four PRs) versus 48% (12 PRs; P = .0007) in NF-kB-positive and NF-kB-negative tumors, respectively. Median TTP in NF-kB-positive patients was 3 v 6.4 months in the remaining patients (P = .021). Median overall survival was 9.5 v 15.8 months for NF-kB-positive and NF-kB-negative patients, respectively (P = .036)

CONCLUSION

The difference in median TTP, overall survival, and response rate seem to confirm that NF-kB may play a crucial role in predicting the efficacy of cetuximab and irinotecan in advanced colorectal tumors.

A tyrosine-based signal plays a critical role in the targeting and function of adenovirus RIDalpha protein

Early region 3 genes of human adenoviruses contribute to the virus life cycle by altering the trafficking of cellular proteins involved in adaptive immunity and inflammatory responses. The ability of early region 3 genes to target specific molecules suggests that they could be used to curtail pathological processes associated with these molecules and treat human disease. However, this approach requires genetic dissection of the multiple functions attributed to early region 3 genes. The purpose of this study was to determine the role of targeting on the ability of the early region 3-encoded protein RIDalpha to downregulate the EGF receptor. A fusion protein between the RIDalpha cytoplasmic tail and glutathione S-transferase was used to isolate clathrin-associated adaptor 1 and adaptor 2 protein complexes from mammalian cells. Deletion and site-directed mutagenesis studies showed that residues 71-AYLRH of RIDalpha are necessary for in vitro binding to both adaptor complexes and that Tyr72 has an important role in these interactions. In addition, RIDalpha containing a Y72A point mutation accumulates in the trans-Golgi network and fails to downregulate the EGF receptor when it is introduced into mammalian cells as a transgene. Altogether, our data suggest a model where RIDalpha is trafficked directly from the trans-Golgi network to an endosomal compartment, where it intercepts EGF receptors undergoing constitutive recycling to the plasma membrane and redirects them to lysosomes.

Activation of NADPH oxidase by transforming growth factor-beta in hepatocytes mediates up-regulation of epidermal growth factor receptor ligands through a nuclear factor-kappaB-dependent mechanism

The TGF-beta (transforming growth factor-beta) induces survival signals in foetal rat hepatocytes through transactivation of EGFR (epidermal growth factor receptor). The molecular mechanism is not completely understood, but both activation of the TACE (tumour necrosis factor alpha-converting enzyme)/ADAM17 (a disintegrin and metalloproteinase 17; one of the metalloproteases involved in shedding of the EGFR ligands) and up-regulation of TGF-alpha and HB-EGF (heparin-binding epidermal growth factor-like growth factor) appear to be involved. In the present study, we have analysed the molecular mechanisms that mediate up-regulation of the EGFR ligands by TGF-beta in foetal rat hepatocytes. The potential involvement of ROS (reactive oxygen species), an early signal induced by TGF-beta, and the existence of an amplification loop triggered by initial activation of the EGFR, have been studied. Results indicate that DPI (diphenyleneiodonium) and apocynin, two NOX (NADPH oxidase) inhibitors, and SB431542, an inhibitor of the TbetaR-I (TGF-beta receptor I), block up-regulation of EGFR ligands and Akt activation. Different members of the NOX family of genes are expressed in hepatocytes, included nox1, nox2 and nox4. TGF-beta up-regulates nox4 and increases the levels of Rac1 protein, a known regulator of both Nox1 and Nox2, in a TbetaR-I-dependent manner. TGF-beta mediates activation of the nuclear factor-kappaB pathway, which is inhibited by DPI and is required for up-regulation of TGF-alpha and HB-EGF. In contrast, EGFR activation is not required for TGF-beta-induced up-regulation of those ligands. Considering previous work that has established the role of ROS in apoptosis induced by TGF-beta in hepatocytes, the results of the present study indicate that ROS might mediate both pro- and anti-apoptotic signals in TGF-beta-treated cells.

MUC5AC, a gel-forming mucin accumulating in gallstone disease, is overproduced via an epidermal growth factor receptor pathway in the human gallbladder

Despite evidence that mucin overproduction is critical in the pathogenesis of gallstones, the mechanisms triggering mucin production in gallstone disease are unknown. Here, we tested the potential implication of an inflammation-dependent epidermal growth factor receptor (EGF-R) pathway in the regulation of gallbladder mucin synthesis. In gallbladder tissue sections from subjects with cholesterol gallstones, mucus accumulation was associated with neutrophil infiltration and with increased expressions of EGF-R and of tumor necrosis factor-alpha (TNF-alpha). In primary cultures of human gallbladder epithelial cells, TNF-alpha induced EGF-R overexpression. In the presence of TNF-alpha, EGF-R ligands (either EGF or transforming growth factor-alpha) caused significant increases in MUC5AC mRNA and protein production, whereas expression of the other gallbladder mucins MUC1, MUC3, and MUC5B was unchanged. In addition, on gallbladder tissue sections from subjects with gallstones, increased MUC5AC immunoreactivity was detected in the epithelium and within mucus gel in the lumen. Studies in primary cultures demonstrated that MUC5AC up-regulation induced by the combination of TNF-alpha with EGF-R ligands was completely blunted by inhibitors of EGF-R tyrosine kinase and mitogen-activated protein/extracellular signal-related kinase kinase. In conclusion, an inflammation-dependent EGF-R cascade causes overproduction of the gel-forming mucin MUC5AC, which accumulates in cholesterol gallstone disease. The ability to interrupt this cascade is of potential interest in the prevention of cholesterol gallstones.

TNF-alpha induces MMP-9 expression via activation of Src/EGFR, PDGFR/PI3K/Akt cascade and promotion of NF-kappaB/p300 binding in human tracheal smooth muscle cells

TNF-alpha has been shown to induce matrix metalloproteinase-9 (MMP-9) expression, which, in turn, degrades extracellular matrix in the inflammatory responses. However, the inductive mechanisms of the MMP-9 by TNF-alpha remain unclear. In human tracheal smooth muscle cells, TNF-alpha induced MMP-9 expression and Akt phosphorylation in a time-dependent manner, which was attenuated by the inhibitors of Src (PP1), epidermal growth factor receptor (AG1478), PDGFR (AG1296), and PI3K (LY294002), respectively, revealed by reporter gene assay, RT-PCR, zymographic, and Western blot analyses. Transfection with the dominant negative mutants of c-Src (KM, K295M [kinase inactive mutant]), p85, and Akt (KA, K179A) also reduced MMP-9 expression. These findings indicated that MMP-9 expression was regulated by PI3K/Akt via the transactivation of growth factor receptors. Furthermore, LY294002 or wortmannin inhibited Akt phosphorylation but had no effect on NF-kappaB translocation, which was blocked by helenalin. Mutated NF-kappaB DNA binding element in the MMP-9 promoter and helenalin also attenuated MMP-9 expression, suggesting that PI3K/Akt and NF-kappaB independently regulated MMP-9 expression. To support this notion, immunofluorescence staining and immunoprecipitation were applied to characterize the transcription factors involved in these responses. The results showed that LY294002 and curcumin blocked Akt translocation into nucleus. In contrast, p300, acetyl-histone (H3), and NF-kappaB p65 were found to be coimmunoprecipitated with the phosphorylated Akt, indicating that these components associated with the MMP-9 promoter are revealed by chromatin immunoprecipitation assay. Thus, our study provides a new insight into the molecular mechanisms that TNF-alpha-stimulated Akt phosphorylation mediated through transactivation of Src and growth factor receptors may stimulate the recruitment of p300, assemble transcription factor (p65), and then lead to MMP-9 expression.

p38 MAP kinase mediates stress-induced internalization of EGFR: implications for cancer chemotherapy

The epidermal growth factor receptor (EGFR) frequently associates with cancer and already serves as a target for therapy. We report that inflammatory cytokines and ultraviolet (UV) irradiation respectively induce transient or sustained phosphorylation of EGFR. Subsequently, EGFR internalizes via a Clathrin-mediated process. In cytokine-stimulated cells, EGFR recycles back to the cell surface, whereas in irradiated cells it arrests in Rab5-containing endosomes. Under both conditions, receptor internalization is instigated by the p38 stress-induced kinase. The underlying mechanism entails phosphorylation of EGFR at a short segment (amino acids 1002-1022) containing multiple serines and threonines, as well as phosphorylation of two Rab5 effectors, EEA1 and GDI. Like UV irradiation, a chemotherapeutic agent activates p38 and accelerates receptor internalization. We demonstrate that abrogating EGFR internalization reduces the efficacy of chemotherapy-induced cell death. Hence, by preventing EGFR-mediated survival signaling, the internalization route we uncovered enhances the cytotoxic effect of drugs like cis-platinum, which may underlie interactions between chemotherapy and EGFR-targeting drugs.

Transforming growth factor-alpha mediates nuclear factor kappaB activation in strained arteries

Mechanical factors regulate both blood vessel growth and the development and progression of vascular disease. Acting on apoptotic and inflammatory signaling, the transcription factor nuclear factor kappaB (NF-kappaB) is a likely mediator of these processes. Nevertheless, pressure-dependent NF-kappaB activation pathways remain mostly unknown. Here we report that high intraluminal pressure induces reactive oxygen species (ROS) in arteries and that inhibition of NADPH oxidase prevents both the generation of ROS and the activation of NF-kappaB associated with high pressure. We also identify the epidermal growth factor receptor (EGFR) as a ROS-dependent signaling intermediate. In arteries from EGFR mutant mice (waved-2), pressure fails to activate NF-kappaB. Moreover, using vessels from EGFR ligand-deficient mice, we show that transforming growth factor (TGF)-alpha, but neither heparin-binding EGF-like growth factor nor epiregulin, transduces NF-kappaB activation by high pressure. Preventing the release of the active form of TGF-alpha also abolishes NF-kappaB induction by strain. The role of TGF-alpha signaling in vascular remodeling is substantiated in vivo; angiotensin II-induced activation of NF-kappaB and associated cell proliferation and wall thickening are much reduced in TGF-alpha-mutant mice compared with wild-type, despite equivalent hypertension in both groups. Conversely, apoptotic cells are detected only in vessels from hypertensive TGF-alpha-mutant mice, outlining the role of NF-kappaB in cell survival. Finally, the NF-kappaB activation pathway contrasts with that of extracellular signal-regulated kinase 1/2, which is activated by stretch through the EGFR but does not implicate TGF-alpha. Hence, our data identify TGF-alpha as a potential specific target to modulate mechanosensitive NF-kappaB activation and associated vascular remodeling.

Metalloprotease-dependent amphiregulin release mediates tumor necrosis factor-α-induced IL-8 secretion in the human airway epithelial cell line NCI-H292

Tumor necrosis factor-alpha (TNF-alpha) is a potent multifunctional cytokine that plays a central role in the pathogenesis of many inflammatory diseases. Interleukin-8 (IL-8) is a principle neutrophil chemoattractant and activator in humans. The alveolar macrophage-derived TNF-alpha initiates lung inflammation through its ability to stimulate IL-8 synthesis in airway epithelial cells. Since recent studies demonstrated that the stimulation of epidermal growth factor receptor (EGFR) could induce IL-8 secretion, the involvement of EGFR in TNF-alpha-induced IL-8 secretion in airway epithelium-like NCI-H292 cells was investigated in this study. TNF-alpha and epidermal growth factor (EGF) stimulated IL-8 secretion in a time- and concentration-dependent manner. Inhibition of the EGFR by either an anti-EGFR neutralizing antibody or by its specific inhibitor AG1478 (1 microM) blocked TNF-alpha-induced IL-8 secretion. In addition, TNF-alpha stimulated tyrosine phosphorylation of the EGFR within 5 min after stimulation. Further, TNF-alpha-induced IL-8 secretion was completely inhibited by the neutralizing antibody against amphiregulin (AR), an EGFR ligand, suggesting that TNF-alpha-induced IL-8 secretion was mediated by the AR-EGFR pathway. Furthermore, TNF-alpha stimulated the release of AR in a concentration-dependent manner. Finally, both AR and IL-8 release-induced by TNF-alpha were eliminated by pretreatment with either GM6001, a broad-spectrum inhibitor for metalloprotease, or TAPI-1, relatively selective inhibitor for TNF-alpha converting enzyme (TACE). These findings indicate that metalloprotease-mediated AR shedding and subsequent activation of EGFR play a critical role in TNF-alpha-induced IL-8 secretion from the human airway epithelium-like NCI-H292 cells, and that TACE is one of the most possible candidates for metalloprotease responsible for TNF-alpha-induced AR shedding.

Enhancement of sensitivity to tumor necrosis factor alpha in non-small cell lung cancer cells with acquired resistance to gefitinib

Tumor cells that have acquired resistance to gefitinib through continuous drug administration may complicate future treatment. To investigate the mechanisms of acquired resistance, we established PC-9/ZD2001, a non-small-cell lung cancer cell line resistant to gefitinib, by continuous exposure of the parental cell line PC-9 to gefitinib. After 6 months of culture in gefitinib-free conditions, PC-9/ZD2001 cells reacquired sensitivity to gefitinib and were established as a revertant cell line, PC-9/ZD2001R. PC-9/ZD2001 cells showed collateral sensitivity to several anticancer drugs (vinorelbine, paclitaxel, camptothecin, and 5-fluorouracil) and to tumor necrosis factor alpha (TNF-alpha). Compared with PC-9 cells, PC-9/ZD2001 cells were 67-fold more sensitive to TNF-alpha and PC-9/ZD2001R cells were 1.3-fold more sensitive. Therefore, collateral sensitivity to TNF-alpha was correlated with gefitinib resistance. PC-9/ZD2001 cells expressed a lower level of epidermal growth factor receptor (EGFR) than did PC-9 cells; this down-regulation was partially reversed in PC-9/ZD2001R cells. TNF-alpha-induced autophosphorylation of EGFR (cross-talk signaling) was detected in all three cell lines. However, TNF-alpha-induced Akt phosphorylation and IkappaB degradation were observed much less often in PC-9/ZD2001 cells than in PC-9 cells or PC-9/ZD2001R cells. Expression of the inhibitor of apoptosis proteins c-IAP1 and c-IAP2 was induced by TNF-alpha in PC-9 and PC-9/ZD2001R cells but not in PC-9/ZD2001 cells. This weak effect of EGFR on Akt pathway might contribute to the TNF-alpha sensitivity of PC-9/ZD2001 cells. These results suggest that therapy with TNF-alpha would be effective in some cases of non-small-cell lung cancer that have acquired resistance to gefitinib.

A promiscuous liaison between IL-15 receptor and Axl receptor tyrosine kinase in cell death control

Discrimination between cytokine receptor and receptor tyrosine kinase (RTK) signaling pathways is a central paradigm in signal transduction research. Here, we report a 'promiscuous liaison' between both receptors that enables interleukin (IL)-15 to transactivate the signaling pathway of a tyrosine kinase. IL-15 protects murine L929 fibroblasts from tumor necrosis factor alpha (TNFalpha)-induced cell death, but fails to rescue them upon targeted depletion of the RTK, Axl; however, Axl-overexpressing fibroblasts are TNFalpha-resistant. IL-15Ralpha and Axl colocalize on the cell membrane and co-immunoprecipitate even in the absence of IL-15, whereby the extracellular part of Axl proved to be essential for Axl/IL-15Ralpha interaction. Most strikingly, IL-15 treatment mimics stimulation by the Axl ligand, Gas6, resulting in a rapid tyrosine phosphorylation of both Axl and IL-15Ralpha, and activation of the phosphatidylinositol 3-kinase/Akt pathway. This is also seen in mouse embryonic fibroblasts from wild-type but not Axl-/- or IL-15Ralpha-/- mice. Thus, IL-15-induced protection from TNFalpha-mediated cell death involves a hitherto unknown IL-15 receptor complex, consisting of IL-15Ralpha and Axl RTK, and requires their reciprocal activation initiated by ligand-induced IL-15Ralpha.

Tumor necrosis factor-alpha triggers mucus production in airway epithelium through an IkappaB kinase beta-dependent mechanism

Excessive mucus production by airway epithelium is a major characteristic of a number of respiratory diseases, including asthma, chronic bronchitis, and cystic fibrosis. However, the signal transduction pathways leading to mucus production are poorly understood. Here we examined the potential role of IkappaB kinase beta (IKKbeta) in mucus synthesis in vitro and in vivo. Tumor necrosis factor-alpha (TNF-alpha) or transforming growth factor-alpha stimulation of human epithelial cells resulted in mucus secretion as measured by MUC5AC mRNA and protein. TNF-alpha stimulation induced IKKbeta-dependent p65 nuclear translocation, mucus synthesis, and production of cytokines from epithelial cells. TNF-alpha, but not transforming growth factor-alpha, induced mucus production dependent on IKKbeta-mediated NF-kappaB activation. In vivo, TNF-alpha induced NF-kappaB as determined by whole mouse body bioluminescence. This activation was localized to the epithelium as revealed by LacZ staining in NF-kappaB-LacZ transgenic mice. TNF-alpha-induced mucus production in vivo could also be inhibited by administration into the epithelium of an IKKbeta dominant negative adenovirus. Taken together, our results demonstrated the important role of IKKbeta in TNF-alpha-mediated mucus production in airway epithelium in vitro and in vivo.

Selective inhibition of TNF-alpha-induced activation of mitogen-activated protein kinases and metastatic activities by gefitinib

We have reported that the selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, gefitinib (‘Iressa’, ZD1839), suppressed intrahepatic metastasis of hepatocellular carcinoma CBO140C12 cells. In this study, we focused on the tumour necrosis factor-α (TNF-α) signalling pathways. Real-time reverse transcription–polymerase chain reaction showed that TNF-α mRNA was expressed in large quantities in the implanted tumour. Gefitinib inhibited EGF- but not hepatocyte growth factor (HGF)-induced activation of mitogen-activated protein kinase (MAPK) cascades, suggesting selectivity of the inhibitor. However, gefitinib inhibited the TNF-α-induced activation of MAPKs and Akt. In addition, TNF-α-induced metastatic properties including adhesion to fibronectin, mRNA expression of integrin αv, production of matrix metalloproteinase-9 and invasion were inhibited by gefitinib without affecting cell proliferation. Furthermore, the TNF-α-induced responses except for NF-κB activation were blocked by metalloprotease inhibitors, suggesting that gefitinib inhibited the transactivation of EGFR induced by TNF-α. These results suggest that the TNF-α signalling pathway is a possible target of gefitinib in suppressing the intrahepatic metastasis of hepatocellular carcinoma.

Fish oil supplementation in the treatment of cachexia in pancreatic cancer patients

Patients with pancreatic cancer often experience a loss of weight and appetite, known as the anorexia-cachexia syndrome, which is associated with decreased quality of life and reduced survival. Research into the biological mechanisms of cachexia has demonstrated that an array of inflammatory mediators and tumor-derived factors cause appetite suppression, skeletal muscle proteolysis, and lipolysis,producing an overall hypercatabolic state that contributes to loss of fat and lean body mass. Omega-3 polyunsaturated fatty acids (n-3 PUFAs) have been shown to modulate levels of proinflammatory cytokines, hepatic acute phase proteins, eicosanoids, and tumor-derived factors in animal models of cancer and may reverse some aspects of the process of cachexia. Results of clinical trials of n-3 PUFAs in the form of fish oils have been mixed, but should encourage further investigation into dietary fish oil supplementation, including the most effective route of administration and the proper dosage to promote optimal weight maintenance and to limit side effects. Concerns about standardization and quality control should also be considered. With the current available evidence, a recommendation for the use of omega 3 polyunsaturated fatty acids in pancreatic cancer cachexia is premature.

Epidermal growth factor enhances TNF-α-induced priming of human neutrophils

The intensity of neutrophil inflammatory response could be rapidly amplified by priming with pro-inflammatory mediators such as TNF-alpha, GM-CSF or LPS at low concentrations prior to stimuli. We proposed that epidermal growth factor (EGF) increases TNF-alpha-induced priming of human neutrophils. This study showed that EGF enhanced TNF-alpha-induced activation of neutrophils functions. The addition of EGF to neutrophils cultured with TNF-alpha resulted in increased respiratory burst and phagocytic activity of polymorphonuclear leukocytes (PMN) and up-regulation of adhesion molecule CD11b. Moreover, EGF enhanced IL-8 production by TNF-alpha-primed PMN. EGF alone was able to prime CD11b expression and IL-8 production by PMN. EGF receptor selective tyrosine kinase inhibitor, tyrphostin AG-1517, blocked the effect of priming with EGF, whereas the status of non-primed and TNF-alpha-primed neutrophils remained unaffected. EGFR expression on neutrophils was confirmed by flow cytometry and CELISA methods. These data provide the original evidence that EGF significantly enhances TNF-alpha-induced priming of human neutrophils acting through EGFR tyrosine kinase pathway. The observed effect may be a result of co-operative action of EGF, TNF-alpha and reactive oxygen intermediates (ROI).

The γ-Glutamylcysteine Synthetase and Glutathione Regulate Asbestos-induced Expression of Activator Protein-1 Family Members and Activity

Asbestos fibers cause persistent increases in activator protein-1 (AP-1) family member proto-oncogenes in lung epithelial and mesothelial cells that are linked to proliferation and cell transformation. Using lung epithelial cells, the progenitor cells of lung cancers, we report that crocidolite asbestos initially depletes intracellular glutathione followed by up-regulation of both catalytic and modifier subunits of gamma-glutamylcysteine synthetase. In vivo asbestos inhalation experiments confirm increased protein levels of gamma-glutamylcysteine synthetase in mouse lungs. We also show that asbestos-induced mRNA levels of fos/jun proto-oncogenes, fra-1 transactivation, and AP-1 to DNA binding activity are glutathione-dependent. Epidermal growth factor receptor activity by asbestos is blocked by N-acetyl-l-cysteine, suggesting that it is an initial redox-activated event leading to downstream AP-1 proto-oncogene up-regulation. The overexpression of subunits of gamma-glutamylcysteine synthetase in combination completely blocked asbestos-induced up-regulation of AP-1 proto-oncogene expression. However, when overexpressed individually, the modifier subunit had more dramatic effects than the catalytic subunit. Our work shows that the glutathione-controlled redox status of the epithelial cell plays a pivotal role in asbestos-induced epidermal growth factor receptor and proto-oncogene activation as well as AP-1 activity.

Induction of Hypoxia-inducible Factor 1 Activity by Muscarinic Acetylcholine Receptor Signaling

Hypoxia-inducible factor-1 (HIF-1) is a master regulator of cellular adaptive responses to hypoxia. Levels of the HIF-1alpha subunit increase under hypoxic conditions. Exposure of cells to growth factors, prostaglandin, and certain nitric oxide donors also induces HIF-1alpha expression under non-hypoxic conditions. We demonstrate that muscarinic acetylcholine signals induce HIF-1alpha expression and transcriptional activity in a receptor subtype-specific manner using HEK293 cells transiently overexpressing each of M1-M4 muscarinic acetylcholine receptors. The muscarinic signaling pathways inhibited HIF-1alpha hydroxylation and degradation and induced HIF-1alpha protein synthesis that was confirmed by pulse labeling studies. Muscarinic signal-induced HIF-1alpha protein and HIF-1-dependent gene expression were blocked by treating cells with inhibitors of phosphatidylinositol 3-kinase, MAP kinase kinase, or tyrosine kinase signaling pathways. Dominant-negative forms of Ras and/or Rac-1 significantly suppressed HIF-1 activation by muscarinic signaling. Signaling via M1- and M3- but not M2- or M4-AchRs promote accumulation and transcriptional activation of HIF-1alpha. We conclude that muscarinic acetylcholine signals activate HIF-1 by both stabilization and synthesis of HIF-1alpha and by inducing the transcriptional activity of HIF-1alpha.

Soy isoflavone phyto-pharmaceuticals in interleukin-6 affections. Multi-purpose nutraceuticals at the crossroad of hormone replacement, anti-cancer and anti-inflammatory therapy

Interleukin-6 is a pleiotropic cytokine which plays a crucial role in immune physiology and is tightly controlled by hormonal feedback mechanisms. After menopause or andropause, loss of the normally inhibiting sex steroids (estrogen, testosterone) results in elevated IL6 levels that are further progressively increasing with age. Interestingly, excessive IL6 production promotes tumorigenesis (breast, prostate, lung, colon, ovarian), and accounts for several disease-associated pathologies and phenotypical changes of advanced age, such as osteoporosis, rheumatoid arthritis, multiple myeloma, neurodegenerative diseases and frailty. In this respect, pharmacological modulation of IL6 gene expression levels may have therapeutical benefit in preventing cancer progression, ageing discomforts and restoring immune homeostasis. Although "plant extracts" are used in folk medicine within living memory, it is only since the 20th century that numerous scientific investigations have been performed to discover potential health-protective food compounds or "nutraceuticals" which might prevent cancer and ageing diseases. About 2000 years ago, Hippocrates already highlighted "Let food be your medicine and medicine be your food". Various nutrients in the diet play a crucial role in maintaining an "optimal" immune response, such that deficient or excessive intakes can have negative consequences on the organism's immune status and susceptibility to a variety of pathologies. Over the last few decades, various immune-modulating nutrients have been identified, which interfere with IL6 gene expression. Currently, a broad range of phyto-pharmaceuticals with a claimed hormonal activity, called "phyto-estrogens", is recommended for prevention of various diseases related to a disturbed hormonal balance (i.e. menopausal ailments and/or prostate/breast cancer). In this respect, there is a renewed interest in soy isoflavones (genistein, daidzein, biochanin) as potential superior alternatives to the synthetic selective estrogen receptor modulators (SERMs), which are currently applied in hormone replacement therapy (HRT). As phyto-chemicals integrate hormonal ligand activities and interference with signaling cascades, therapeutic use may not be restricted to hormonal ailments only, but may have applications in cancer chemoprevention and/or NF-kappaB-related inflammatory disorders as well.

Induced Autocrine Signaling through the Epidermal Growth Factor Receptor Contributes to the Response of Mammary Epithelial Cells to Tumor Necrosis Factor α

In contrast to the well known cytotoxic effects of tumor necrosis factor (TNF) alpha in many mammary cancer cells, we have found that TNF stimulates the proliferation and motility of human mammary epithelial cells (HMECs). Since the response of HMECs to TNF is similar to effects mediated by epidermal growth factor receptor (EGFR) activation, we explored the potential role of cross-talk through the EGFR signaling pathways in mediating cellular responses to TNF. Using a microarray enzyme-linked immunoassay, we found that exposure to TNF stimulated the dose-dependent shedding of the EGFR ligand transforming growth factor alpha (TGFalpha). Both proliferation and motility of HMECs induced by TNF was prevented either by inhibiting membrane protein shedding with a metalloprotease inhibitor, by blocking epidermal growth factor receptor (EGFR) kinase activity, or by limiting ligand-receptor interactions with an antagonistic anti-EGFR antibody. EGFR activity was also necessary for TNF-induced release of matrix metalloprotease-9, thought to be an essential regulator of mammary cell migration. The cellular response to TNF was associated with a biphasic temporal pattern of extracellular signal-regulated kinase (ERK) phosphorylation, which was EGFR-dependent and modulated by inhibition of metalloprotease-mediated shedding. Significantly, the late phase of ERK phosphorylation, detectable within 4 h after exposure, was blocked by the metalloprotease inhibitor batimastat, indicating that autocrine signaling through ligand shedding was responsible for this secondary wave of ERK activity. Our results indicate a novel and important role for metalloprotease activation and EGFR transmodulation in mediating the cellular response to TNF.

NF-kappaB in pancreatic cancer

Although the genetic profile of pancreatic cancer is emerging as a result of much research, the role of specific genetic alterations that initiate tumorigenesis and produce its cardinal clinical features of locally aggressive growth, metastasis, and chemotherapy resistance remains unresolved. Recently, a number of studies have shown that the inhibition of constitutive NF-kappaB activation, one of the frequent molecular alterations in pancreatic cancer, inhibits tumorigenesis and metastasis. It also sensitizes pancreatic cancer cell lines to anticancer agent-induced apoptosis. Therefore because of the crucial role of NF-kappaB in pancreatic cancer, it is a potential target for developing novel therapeutic strategies for the disease. In vivo and in vitro models that mimic the tumorigenic phenotypes in the appropriate histological and molecular concert would be very useful for confirming the suspected role of the pancreatic cancer signature genetic lesions and better understanding the molecular basis of this disease.

Nuclear factor-kappa B activation promotes restitution of wounded intestinal epithelial monolayers

Epithelial restitution, the movement of wound-edge cells into an area of epithelial cell denudation, is an important early step in the ulcer healing process. Growth factors regulate epithelial restitution, yet little is known about the transcriptional pathways that mediate their effects on cell migration. The transcription factor nuclear factor (NF)-kappaB is a master regulator of the host inflammatory response that is activated in the epithelium in intestinal inflammation, which often accompanies epithelial injury. We hypothesized that NF-kappaB may be an important transcriptional regulator of epithelial restitution. In an in vitro model of scrape-wounded monolayers of nontransformed rat intestinal epithelial (RIE-1) cells, NF-kappaB was activated in epithelial cells at the wound edge. Blocking of NF-kappaB activation by either pharmacological or genetic approaches inhibited intestinal epithelial restitution. Moreover, scrape wounding activated the epidermal growth factor receptor (EGFR) in cells at the wound edge, and, importantly, inhibiting EGFR tyrosine kinase activity decreased scrape wound-induced NF-kappaB activation and cell migration. These results indicate a novel role of NF-kappaB activation in a signaling pathway important for restitution and healing of intestinal epithelia. To the extent NF-kappaB may have parallel functions in vivo, they also suggest a need for caution in the proposed use of NF-kappaB inhibitors for the treatment of conditions associated with inflammation and injury of intestinal and other mucosal surfaces.

Blockade of the EGF receptor induces a deranged chemokine expression in keratinocytes leading to enhanced skin inflammation

During inflammatory skin disorders such as psoriasis, atopic dermatitis, and allergic contact dermatitis, epidermal keratinocytes overexpress large amounts of soluble epidermal growth factor receptor ligands in response to tumor necrosis factor alpha and interferon gamma. These cytokines also promote de novo synthesis of numerous chemokines, including CCL2/MCP-1, CCL5/RANTES, CXCL10/IP-10, and CXCL8/IL-8, in turn responsible for the recruitment of different leukocyte populations. This study demonstrates that stimulation of EGFR down-regulates CCL2, CCL5, and CXCL10, while it increases CXCL8 expression in keratinocytes. Conversely, EGFR signaling blockade produces opposite effects, with increased CCL2, CCL5, and CXCL10, and reduced CXCL8 expression. In a mouse model of contact hypersensitivity, a single topical administration of a selective EGFR kinase blocker before antigen challenge results in a markedly enhanced immune response with increased chemokine expression and heavier inflammatory cell infiltrate. Targeting EGFR on epithelial cells may thus have profound impact on inflammatory and immune responses.

Regulation of interleukin-1alpha expression by integrins and epidermal growth factor receptor in keratinocytes from a mouse model of inflammatory skin disease

Transgenic mice expressing beta1 integrins in the suprabasal epidermal layers have sporadic skin hyperproliferation and inflammation correlated with activation of extracellular signal-regulated kinase (Erk) mitogen-activated protein kinase and increased interleukin (IL)-1alpha production. We investigated the link between aberrant integrin expression, Erk activation, and expression of IL-1alpha. Transgenic keratinocytes had higher basal Erk activity and IL-1alpha levels than nontransgenic controls and were more sensitive to stimulation of Erk activity and IL-1alpha production by IL-1alpha, 12-O-tetradecanoylphorbol-13-acetate (TPA), epidermal growth factor (EGF), and serum. Inhibition of Erk in transgenic keratinocytes reduced basal IL-1alpha levels and the stimulation of IL-1alpha production by serum or phorbol ester, demonstrating that Erk could regulate IL-1alpha expression. TPA or IL-1alpha treatment resulted in rapid down-regulation of the EGF receptor in transgenic cells, indicative of transactivation. Inhibition of transactivation blocked basal and TPA or IL-1alpha induced Erk activation, but not IkappaBalpha degradation, and abolished increased IL-1alpha production in transgenic cells. In transgene-negative cells, constitutive activation of IL-1-dependent signaling by wild type or kinase-dead IRAK1 stimulated IL-1alpha production independent of Erk. We conclude that suprabasal integrin expression leads to Erk activation and increased IL-1alpha expression by potentiating activation of the EGF receptor. These results provide a mechanism by which aberrant integrin expression triggers epidermal hyperproliferation and inflammation.

Differential responses by pancreatic carcinoma cell lines to prolonged exposure to Erbitux (IMC-C225) anti-EGFR antibody

BACKGROUND

Pancreatic cancer remains a devastating disease, with 95% of all patients diagnosed with the disease dying within 2 years. The combined therapy using Erbitux, gemcitabine, and radiation caused complete tumor regression using a nude mouse model inoculated with pancreatic MiaPaCa-2 cells but only a delay in tumor growth with BxPC-3. We investigated the effect of prolonged Erbitux treatment to the sensitivity to gemcitabine and/or radiation and the epidermal growth factor receptor (EGFR) signal transduction pathway.

METHODS

MiaPaCa-2 and BxPC-3 cells were cultured with or without Erbitux for 6 weeks. Cells were then treated with gemcitabine and/or radiation, harvested 48 h after treatment, and counted. Differences in EGFR expression after exposure to Erbitux were analyzed by FACS. Internalization rates of EGFR induced by Erbitux on these cell lines were determined using 125I-EGF binding assay after removal of Erbitux by acidic wash. Cell lysates were harvested after cells were stimulated with EGF, FGF, or IGF-1 respectively, and EGFR was immunoprecipitated using Erbitux. Samples were separated using SDS-PAGE and transferred to PVDF membrane. The membranes were probed with antibody against human growth factor receptor binding protein (Grb2) to detect the association of this Ras-MAPK upstream adaptor protein to EGFR. Cell lysates were also separated with SDS-PAGE and probed with rabbit anti-human PARP after samples were transferred to PVDF membrane. Expression of BAX and Bcl-(XL) were probed in the cells treated with or without Erbitux.

RESULTS

Proliferation assays indicated that prolonged exposure to Erbitux increased the sensitivities of MiaPaCa-2 to gemcitabine and radiation therapy (41 +/- 16% vs 52 +/- 9% for gemcitation, 28 +/- 9 vs 39 +/- 9% for combination; P = 0.015) but not for BxPC-3. FACS analysis showed that the expressed EGFR level decreased by about 42% on MiaPaCa 2 whereas no loss was seen on BxPC-3. Expression of BAX was upregulated on MiaPaCa-2. Poly (ADP-ribose) polymerase cleavage indicated the killing was mediated by apoptosis. Immunoblots showed that Grb2 was co-immunoprecipitated with EGFR after EGF stimulation. Incubation with Erbitux blocked Grb2 binding in MiaPaCa-2 but not BxPC 3. FGF transactivated EGFR down stream Ras-MAPK in the presence or absence of Erbitux. Internalization of EGFR induced by Erbitux did not differ between MiaPaCa-2 and BxPC-3.

CONCLUSIONS

1) Association of Grb2 to EGFR in BxPC-3 induced by EGF in the presence of Erbitux indicates an alternate pathway of Ras-MAPK activation, which may be related with the tumor resistance to treatment; 2) transactivation of EGFR downstream Ras-MAPK pathway by FGF contributes the resistance to treatment; and 3) downregulation of EGFR may increase the response to therapy.

Grape seed extract inhibits EGF-induced and constitutively active mitogenic signaling but activates JNK in human prostate carcinoma DU145 cells: possible role in antiproliferation and apoptosis

A loss of functional androgen receptor and an enhanced expression of growth factor receptors and associated ligands are causal genetic events in prostate cancer (PCA) progression. These genetic alterations lead to an epigenetic mechanism where a feedback autocrine loop between membrane receptor and ligand (e.g. EGFR-TGFalpha) results in a constitutive activation of MAPK-Elk1-AP1-mediated mitogenic signaling in human PCA at an advanced and androgen-independent stage. We rationalized that inhibiting these epigenetic events could be useful in controlling advanced PCA growth. Recently, we found that grape seed extract (GSE), a dietary supplement rich in flavonoid procyanidins, inhibits advanced and androgen-independent human PCA DU145 cell growth in culture and nude mice. Here, we performed detailed mechanistic studies to define the effect of GSE on EGFR-Shc-MAPK-Elk1-AP1-mediated mitogenic signaling in DU145 cells. Pretreatment of serum-starved cells with GSE resulted in 70% to almost complete inhibition of EGF-induced EGFR activation and 50% to complete inhibition of Shc activation, which corroborated with a comparable decrease in EGF-induced Shc binding to EGFR. Conversely, EGF-induced ERK1/2 phosphorylation was inhibited only by lower doses of GSE; in fact, higher doses showed an increase. Additional studies showed that GSE alone causes a dose- and time-dependent increase in ERK1/2 phosphorylation in starved DU145 cells that is inhibited by an MEK1 inhibitor PD98059. Independent of this increase in ERK1/2 phosphorylation, GSE showed a strong inhibition of ERK1/2 kinase activity to Elk1 in both cellular and cell-free systems. GSE treatment of cells also inhibited both EGF-induced and constitutively active Elk1 phosphorylation and AP1 activation. GSE treatment also showed DNA synthesis inhibition in starved and EGF-stimulated cells as well as loss of cell viability and apoptotic death that was further increased by adding MEK1 inhibitor. Since GSE strongly induced apoptosis independent of its affect on an increase in phospho-ERK1/2, we hypothesized that apoptotic effect of GSE could be by other mechanism(s) including its effect on stress-associated MAPK, the JNK. Indeed, GSE-treated cells showed a strong and sustained increase in phospho-JNK1/JNK2 levels, JNK activity and phospho-cJun levels. An inhibition of GSE-induced JNK activation by a novel JNK inhibitor SP600125 resulted in a significant reversal of GSE-induced apoptotic death suggesting the involvement of JNK activation by GSE in its apoptosis response. Together, these results suggest that anticancer effects of GSE in PCA be mediated via impairment of EGFR-ERK1/2-Elk1-AP1-mediated mitogenic signaling and activation of JNK causing growth inhibition and apoptosis, respectively.

Restoring apoptosis in pancreatic cancer cells by targeting the nuclear factor-kappaB signaling pathway with the anti-epidermal growth factor antibody IMC-C225

We have previously demonstrated that RelA is constitutively activated in the majority of human pancreatic cancers and plays an important role in tumorigenesis and metastasis. The antiapoptotic gene bcl-xl is a downstream target of RelA, and regulation of bcl-xl transcription is mediated directly by the nuclear factor kappaB (NF-kappaB) binding sites present in the upstream promoter element of the bcl-xl gene. In this study we investigated the effects of inhibition of epidermal growth factor receptor (EGFR) signaling pathway with the anti-EGFR monoclonal antibody IMC-C225 on constitutive NF-kappaB activation and regulation of apoptosis-related genes in human pancreatic cancer cells. We found that activation of EGFR can be blocked with the anti-EGFR antibody IMC-C225 in the human pancreatic cancer cell line MDA Panc-28, leading to a marked decrease in constitutive NF-kappaB DNA binding activity. Our data also suggest that downregulation of NF-kappaB DNA binding activity by IMC-C225 leads to a decrease in bcl-xl and bfl-1 expression. Therefore, targeting the NF-kappaB signaling pathway with an anti-EGFR antibody may be one strategy to restore apoptosis in human pancreatic cancer cells, thereby enhancing the effect of chemotherapy and radiation therapy.

Functional proteomics of breast cancer for signal pathway profiling and target discovery

The near completion of human genome sequencing and the introduction of mass spectrometry combined with advanced bioinformatics for protein identification have led to the emergence of proteomics as a powerful tool for characterizing new markers and therapeutic targets. Breast cancer proteomics has already identified proteins of potential clinical interest, such as the molecular chaperone 14-3-3 sigma and the heat shock protein HSP90, and technological innovations such as large scale and high throughput analysis are now driving the field. Methods in functional proteomics have also been developed to study the intracellular signaling pathways that underlie the development of breast cancer cells. As illustrated by fibroblast growth factor-2 and the H19 noncoding oncogenic mRNA, proteomics is a pertinent approach to identify signaling proteins and to decipher the complex signaling circuitry involved in tumor growth and metastasis. Together with genomics, proteomics is now providing a way to define molecular processes involved in breast carcinogenesis and to identify new therapeutic targets. The next challenge will be the introduction of proteomics as a tool for the clinic, for the establishment of diagnosis, prognosis, and the monitoring of treatment; however, this ambitious goal still requires further technological progress in the field.

Growth signaling in breast cancer cells: outcomes and promises of proteomics

Methods in functional proteomics are now used to study the intracellular signaling pathways that underlie the development of breast cancer. As shown with fibroblast growth factor-2, the oncogenic/non-coding mRNA H19 and 14-3-3 proteins, proteomics is a powerful approach to identify signaling proteins and to decipher the complex signaling circuitry involved in growth of breast cancer cells. Together with genomics, proteomics is now providing a way to define molecular processes involved in breast cancerogenesis and to identify new therapeutic targets.

Proteomics of breast cancer: outcomes and prospects

Breast cancer is a major public health problem. The identification of new markers to differentiate neoplastic from the normal cells, more thorough understanding of different stages of the pathology, as well as the definition of new therapeutic targets, are all of critical importance. With the completion of human genome sequencing and the introduction of mass spectrometry, combined with protein identification via advanced bioinformatics, proteomics has emerged as a valuable tool for the discovery of new molecular markers. New methods in functional proteomics have also been developed to study the intracellular signaling pathways that underline the development of breast cancer. As illustrated with the examples of fibroblast growth factor-2 and H19, an oncogenic, noncoding mRNA, proteomics have become a powerful approach for deciphering the complex signaling circuitry involved in tumor growth. Breast cancer proteomics have already identified proteins of potential clinical interest (such as the molecular chaperone 14-3-3 sigma) and technological innovations in large scale/high throughput analysis are now ushering in new prospects.

Activation of c-Raf kinase by ultraviolet light. Regulation by retinoids

The present study highlights retinoids as modulators of c-Raf kinase activation by UV light. Whereas a number of retinoids, including retinol, 14-hydroxyretroretinol, anhydroretinol (AR), and retinoic acid bound the c-Raf cysteine-rich domain (CRD) with equal affinity in vitro as well as in vivo, they displayed different, even opposing, effects on UV-mediated kinase activation; retinol and 14-hydroxyretroretinol augmented responses, whereas retinoic acid and AR were inhibitory. Oxidation of thiol groups of cysteines by reactive oxygen, generated during UV irradiation, was the primary event in c-Raf activation, causing the release of zinc ions and, by inference, a change in CRD structure. Retinoids modulated these oxidation events directly: retinol enhanced, whereas AR suppressed, zinc release, precisely mirroring the retinoid effects on c-Raf kinase activation. Oxidation of c-Raf was not sufficient for kinase activation, productive interaction with Ras being mandatory. Further, canonical tyrosine phosphorylation and the action of phosphatase were essential for optimal c-Raf kinase competence. Thus, retinoids bound c-Raf with high affinity, priming the molecule for UV/reactive oxygen species-mediated changes of the CRD that set off GTP-Ras interaction and, in context with an appropriate phosphorylation pattern, lead to full phosphotransferase capacity.

Transactivation of ErbB2 and ErbB3 by tumor necrosis factor-alpha and anisomycin leads to impaired insulin signaling through serine/threonine phosphorylation of IRS proteins

The cellular pathways involved in the impairment of insulin signaling by cellular stress, triggered by the inflammatory cytokine tumor necrosis factor-alpha (TNF) or by translational inhibitors like cycloheximide and anisomycin were studied. Similar to TNF, cycloheximide and anisomycin stimulated serine phosphorylation of IRS-1 and IRS-2, reduced their ability to interact with the insulin receptor, inhibited the insulin-induced tyrosine phosphorylation of IRS proteins, and diminished their association with phosphatidylinositol 3-kinase (PI3K). These defects were partially reversed by wortmannin and LY294002, indicating that a PI3K-regulated step is critical for the impairment of insulin signaling by cellular stress. Induction of cellular stress resulted in complex formation between PI3K and ErbB2/ErbB3 and enhanced PI3K activity, implicating ErbB proteins as downstream effectors of stress-induced insulin resistance. Indeed, stimulation of ErbB2/ErbB3 by NDFbeta1, the ErbB3 ligand, inhibited IRS protein tyrosine phosphorylation and recruitment of downstream effectors. Specific inhibitors of the ErbB2 tyrosine kinase abrogated the activation of ErbB2/ErbB3 and in parallel prevented the reduction in IRS protein functions. Taken together, our results suggest a novel mechanism by which cellular stress induces cross-talk between two different signaling pathways. Stress-dependent transactivation of ErbB2/ErbB3 receptors triggers a PI3K cascade that induces serine phosphorylation of IRS proteins culminating in insulin resistance.