NF-kappa B-like factors mediate interleukin 1 induction of c-myc gene transcription in fibroblasts

E-box binding transcription factors in cancer

E-boxes are important regulatory elements in the eukaryotic genome. Transcription factors can bind to E-boxes through their basic helix-loop-helix or zinc finger domain to regulate gene transcription. E-box-binding transcription factors (EBTFs) are important regulators of development and essential for physiological activities of the cell. The fundamental role of EBTFs in cancer has been highlighted by studies on the canonical oncogene MYC, yet many EBTFs exhibit common features, implying the existence of shared molecular principles of how they are involved in tumorigenesis. A comprehensive analysis of TFs that share the basic function of binding to E-boxes has been lacking. Here, we review the structure of EBTFs, their common features in regulating transcription, their physiological functions, and their mutual regulation. We also discuss their converging functions in cancer biology, their potential to be targeted as a regulatory network, and recent progress in drug development targeting these factors in cancer therapy.

Targeting Key Signaling Pathways in Glioblastoma Stem Cells for the Development of Efficient Chemo- and Immunotherapy

Glioblastoma multiforme (GBM) is the most aggressive and most common malignant brain tumor with poor patient survival despite therapeutic intervention. On the cellular level, GBM comprises a rare population of glioblastoma stem cells (GSCs), driving therapeutic resistance, invasion, and recurrence. GSCs have thus come into the focus of therapeutic strategies, although their targeting remains challenging. In the present study, we took advantage of three GSCs-populations recently established in our lab to investigate key signaling pathways and subsequent therapeutic strategies targeting GSCs. We observed that NF-κB, a crucial transcription factor in GBM progression, was expressed in all CD44+/CD133+/Nestin+-GSC-populations. Exposure to TNFα led to activation of NF-κB-RELA and/or NF-κB-c-REL, depending on the GBM type. GSCs further expressed the proto-oncogene MYC family, with MYChigh GSCs being predominantly located in the tumor spheres ("GROW"-state) while NF-κB-RELAhigh GSCs were migrating out of the sphere ("GO"-state). We efficiently targeted GSCs by the pharmacologic inhibition of NF-κB using PTDC/Bortezomib or inhibition of MYC by KJ-Pyr-9, which significantly reduced GSC-viability, even in comparison to the standard chemotherapeutic drug temozolomide. As an additional cell-therapeutic strategy, we showed that NK cells could kill GSCs. Our findings offer new perspectives for developing efficient patient-specific chemo- and immunotherapy against GBM.

Lipopolysaccharide stimulates endogenous β-glucuronidase via PKC/NF-κB/c-myc signaling cascade: a possible factor in hepatolithiasis formation

Hepatolithiasis is commonly encountered in Southeastern and Eastern Asian countries, but the pathogenesis mechanism of stone formation is still not well understood. Now, the role of endogenous β-glucuronidase in pigment stones formation is being gradually recognized. In this study, the mechanism of increased expression and secretion of endogenous β-glucuronidase during hepatolithiasis formation was investigated. We assessed the endogenous β-glucuronidase, c-myc, p-p65, and p-PKC expression in liver specimens with hepatolithiasis by immunohistochemical staining, and found that compared with that in normal liver samples, the expression of endogenous β-glucuronidase, c-myc, p-p65, and p-PKC in liver specimens with hepatolithiasis significantly increased, and their expressions were positively correlated with each other. Lipopolysaccharide (LPS) induced increased expression of endogenous β-glucuronidase and c-myc in hepatocytes and intrahepatic biliary epithelial cells in a dose- and time-dependent manner, and endogenous β-glucuronidase secretion increased, correspondingly. C-myc siRNA transfection effectively inhibited the LPS-induced expression of endogenous β-glucuronidase. Furthermore, NF-κB inhibitor pyrrolidine dithiocarbamate or PKC inhibitor chelerythrine could effectively inhibit the LPS-induced expression of c-myc and endogenous β-glucuronidase, and the expression of p-p65 was also partly inhibited by chelerythrine. Our clinical observations and experimental data indicate that LPS could induce the increased expression and secretion of endogenous β-glucuronidase via a signaling cascade of PKC/NF-κB/c-myc in hepatocytes and intrahepatic biliary epithelial cells, and endogenous β-glucuronidase might play a possible role in the formation of hepatolithiasis.

NFκB regulates expression of Polo-like kinase 4

Activation of the NFκB signaling pathway allows the cell to respond to infection and stress and can affect many cellular processes. As a consequence, NFκB activity must be integrated with a wide variety of parallel signaling pathways. One mechanism through which NFκB can exert widespread effects is through controlling the expression of key regulatory kinases. Here we report that NFκB regulates the expression of genes required for centrosome duplication, and that Polo-like kinase 4 (PLK4) is a direct NFκB target gene. RNA interference, chromatin immunoprecipitation, and analysis of the PLK4 promoter in a luciferase reporter assay revealed that all NFκB subunits participate in its regulation. Moreover, we demonstrate that NFκB regulation of PLK4 expression is seen in multiple cell types. Significantly long-term deletion of the NFκB2 (p100/p52) subunit leads to defects in centrosome structure. This data reveals a new component of cell cycle regulation by NFκB and suggests a mechanism through which deregulated NFκB activity in cancer can lead to increased genomic instability and uncontrolled proliferation.

N-acetyl-Ser-Asp-Lys-Pro inhibits interleukin-1β-mediated matrix metalloproteinase activation in cardiac fibroblasts

Myocardial matrix turnover involves a dynamic balance between collagen synthesis and degradation, which is regulated by matrix metalloproteinases (MMPs). N-acetyl-Ser-Asp-Lys-Pro (Ac-SDKP) is a small peptide that inhibits cardiac inflammation and fibrosis. However, its role in MMP regulation is not known. Thus, we hypothesized that Ac-SDKP promotes MMP activation in cardiac fibroblasts and decreases collagen deposition via this mechanism. To that end, we tested the effects of Ac-SDKP on interleukin-1β (IL-1β; 5 ng/ml)-stimulated adult rat cardiac fibroblasts. We measured total collagenase activity, MMP-2, MMP-9, and MMP-13 expressions, and activity along with their inhibitors, tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2. In order to examine the effects of Ac-SDKP on the signaling pathway that controls MMP transcription, we also measured nuclear factor-κB (NFκB) and p42/44 mitogen-activated protein kinase (MAPK) activation. Ac-SDKP did not alter collagenase or gelatinase activity in cardiac fibroblasts under basal conditions, but blunted the IL-1β-induced increase in total collagenase activity. Similarly, Ac-SDKP normalized the IL-1β-mediated increase in MMP-2 and MMP-9 activities and MMP-13 expression. Inhibition of MMPs by Ac-SDKP was associated with increased TIMP-1 and TIMP-2 expressions. Collagen production was not affected by Ac-SDKP, IL-1β, or a combination of both agents. Ac-SDKP blocked IL-1β-induced p42/44 phosphorylation and NFκB activation in cardiac fibroblasts. We concluded that the Ac-SDKP-inhibited collagenase expression and activation was associated with increased expression of TIMP-1 and TIMP-2. These pharmacological effects of Ac-SDKP may be linked to the inhibition of MAPK and NFκB pathway.

Literature review of the role of hydroxyl radicals in chemically-induced mutagenicity and carcinogenicity for the risk assessment of a disinfection system utilizing photolysis of hydrogen peroxide

We have developed a new disinfection system for oral hygiene, proving that hydroxyl radicals generated by the photolysis of 1 M hydrogen peroxide could effectively kill oral pathogenic microorganisms. Prior to any clinical testing, the safety of the system especially in terms of the risk of carcinogenicity is examined by reviewing the literature. Previous studies have investigated indirectly the kinds of reactive oxygen species involved in some sort of chemically-induced mutagenicity in vitro by using reactive oxygen species scavengers, suggesting the possible involvement of hydroxyl radicals. Similarly, possible involvement of hydroxyl radicals in some sort of chemically-induced carcinogenicity has been proposed. Notably, it is suggested that the hydroxyl radical can play a role in heavy metal-induced carcinogenicity that requires chronic exposure to the carcinogen. In these cases, hydroxyl radicals produced by Fenton-like reactions may be involved in the carcinogenicity. Meanwhile, potential advantages have been reported on the use of the hydroxyl radical, being included in host immune defense by polymorphonuclear leukocytes, and medical applications such as for cancer treatment and antibiotics. From these, we conclude that there would seem to be little to no risk in using the hydroxyl radical as a disinfectant for short-term treatment of the oral cavity.

MINING GENOME VARIATION TO ASSOCIATE GENETIC DISEASE WITH MUTATION ALTERATIONS AND ORTHO/PARALOGOUS POLIMORPHYSMS IN TRANSCRIPTION FACTOR BINDING SITE

We have developed a system rSNP_Guide, , predicting the transcription factor (TF) binding sites on DNA, which mutation-caused alterations may explain disease penetration. rSNP_Guide uses the detected alterations in the mutant DNA binding to unknown TF caused by diseases and, upon the DNA sequences, calculates the alterations in known TF sites so that to select only the known ones with calculated alterations in the best consistence with those detected. Our system has been control tested on the SNP's with known site-disease relationships. For practical aims, two TF sites associated with diseases were predicted and confirmed by the immune assay with anti-TF antibodies. In the case of tumor susceptibility, the GATA site in the second intron of mouse K-ras gene was truly predicted, whereas mutation damage of this site causes tumor resistance. In the case of alcohol dependencies and others behavioral diseases, the mutation-caused spurious YY1 site in the sixth intron of human tryptophan 2,3-dioxygenase (TDO2) gene was successfully predicted. Finally, sixteen non-documented TF sites localizable at both orthologous and paralogous genes were first characterized by three rates "present", "weakened" or "absent", with significance estimated by rSNP_Guide relatively to six TF sites with known mutation-caused alterations in DNA/TF-binding.

Pomegranate fruit extract impairs invasion and motility in human breast cancer

PURPOSE

Pomegranate fruit extracts (PFEs) possess polyphenolic and other compounds with antiproliferative, pro-apoptotic and anti-inflammatory effects in prostate, lung, and other cancers. Because nuclear transcription factor-kB (NF-kB) is known to regulate cell survival, proliferation, tumorigenesis, and inflammation, it was postulated that PFEs may exert anticancer effects at least in part by modulating NF-kB activity.

EXPERIMENTAL DESIGN

The authors investigated the effect of a novel, defined PFE consisting of both fermented juice and seed oil on the NF-kB pathway, which is constitutively active in aggressive breast cancer cell lines. The effects of the PFE on NF-kB-regulated cellular processes such as cell survival, proliferation, and invasion were also examined.

RESULTS

Analytical characterization of the bioactive components of the PFE revealed active constituents, mainly ellagitannins and phenolic acids in the aqueous PFE and conjugated octadecatrienoic acids in the lipid PFE derived from seeds.The aqueous PFE dose-dependently inhibited NF-kB-dependent reporter gene expression associated with proliferation, invasion, and motility in aggressive breast cancer phenotypes while decreasing RhoC and RhoA protein expression.

CONCLUSION

Inhibition of motility and invasion by PFEs, coincident with suppressed RhoC and RhoA protein expression, suggests a role for these defined extracts in lowering the metastatic potential of aggressive breast cancer species.

Molecular mechanisms of excitotoxicity and their relevance to pathogenesis of neurodegenerative diseases

A pivotal role for excitotoxicity in neurodegenerative diseases is gaining increasingly more acceptance, but the underlying mechanisms through which it participates in neurodegeneration still need further investigation. Excessive activation of glutamate receptors by excitatory amino acids leads to a number of deleterious consequences, including impairment of calcium buffering, generation of free radicals, activation of the mitochondrial permeability transition and secondary excitotoxicity. Recent studies implicate excitotoxicity in a variety of neuropathological conditions, suggesting that neurodegenerative diseases with distinct genetic etiologies may share excitotoxicity as a common pathogenic pathway. Thus, understanding the pathways involved in excitotoxicity is of critical importance for the future clinical treatment of many neurodegenerative diseases. This review discusses the current understanding of excitotoxic mechanisms and how they are involved in the pathogenesis of neurodegenerative diseases.

Cationic nano-copolymers mediated IKKbeta targeting siRNA inhibit the proliferation of human Tenon's capsule fibroblasts in vitro

PURPOSE

To synthesize a ternary cationic copolymer called CS-g-(PEI-b-mPEG) and characterize its features as a non-viral siRNA carrier; in turn, to investigate the influence of small interfering RNA (siRNA) targeting IkappaB kinase subunit beta (IKKbeta) on the proliferation of human Tenon's capsule fibroblasts (HTFs) in vitro.

METHODS

First, a novel cationic copolymer composed of low molecular weight, linear poly(ethyleneimine) [PEI] blocked with polyethylene glycol (PEG) and grafted onto a chitosan (CS) molecule was synthesized. CS-g-(PEI-b-mPEG) was then compacted with 21nt siRNA at various copolymer/siRNA charge (N/P) ratios, and the resulting complexes were characterized by dynamic light scattering, gel electrophoresis, and serum incubation. Cell Titer 96 AQ(ueous) One Solution cell proliferation assay was used to investigate the cytotoxicity of this cationic copolymer. Second, siRNAs targeting IKKbeta (IKKBeta-siRNAs) were delivered into the HTFs using CS-g-(PEI-b-mPEG) as the vehicle. Real-time reverse transcription polymerase chain reaction (RT-PCR) subsequently assessed the mRNA level of IKKbeta, and western blot assay was used to determine protein expression. After IKKB-siRNA transfection, Cell Titer 96 AQ(ueous) One Solution cell proliferation assay was used to evaluate the proliferation of HTFs.

RESULTS

The diameter of the CS-g-(PEI-b-mPEG)/siRNA complexes tended to decrease whereas their zeta potential tended to increase as the N/P ratio increased. The CS-g-(PEI-b-mPEG) copolymer showed good siRNA binding ability and high siRNA protection capacity. Furthermore, the copolymer presented remarkable transfection efficiency and showed much less cytotoxicity than 25 kDa PEI. IKKB-siRNAs were successfully delivered into HTFs using CS-g-(PEI-b-mPEG) as a vector. As a result, the expression of IKKbeta was downregulated at both the mRNA and protein levels, and the activation of nuclear factor-kappaB (NF-kappaB) in the HTFs was subsequently inhibited. Most impressively, the proliferation of HTFs was also effectively suppressed through the blocking of the NF-kappaB pathway.

CONCLUSIONS

All the results demonstrate that CS-g-(PEI-b-mPEG) is a promising candidate for siRNA delivery, featuring excellent biocompatibility, biodegradability, and transfection efficiency. The RNA interference (RNAi) strategy using cationic copolymers as siRNA carriers will be a safe and efficient anti-scarring method following glaucoma filtration surgery.

The role of translation in neoplastic transformation from a pathologist's point of view

Increased cell proliferation, which is a hallmark of aggressive malignant neoplasms, requires a general increase in protein synthesis and a specific increase in the synthesis of replication-promoting proteins. Transient increase in the general protein synthesis rate, as well as preferential translation of specific mRNAs coding for growth promoting proteins (e.g. cyclin D1), takes place during normal mitogenic response. A number of extensively studied growth signal transduction pathways (Ras, PI3K, MAPK, mTOR-dependent pathways) activate the function and expression of various components of the translational machinery. In abnormal situations, constitutive activation of signal transduction pathways (e.g. oncogenic activation of Ras or Myc) leads to continuous upregulation of key elements of translational machinery. On the other hand, tumor suppressor genes (p53, pRb) downregulate ribosomal and tRNA synthesis, and their inactivation results in uncontrolled production of these translational components. During recent years, a significant effort has been dedicated to determining whether expression of translation factors is increased in human tumors using clinical biopsy specimens. The results of these studies indicate that expression of particular translation initiation factors is not always increased in human neoplasms. The pattern of expression is characteristic for a particular tumor type. For example, eIF-4E is usually increased in bronchioloalveolar carcinomas but not in squamous cell carcinomas of the lung. Interestingly, in certain highly proliferative and aggressive neoplasms (e.g. squamous cell carcinoma of the lung, melanoma), the expression of eIF-4E is barely detectable. These findings suggest that mechanisms for increasing general protein synthesis in various neoplasms differ significantly. Finally, the possibility of qualitative alterations in the translational machinery, rather than a simple increase in the activity of its components, is discussed along with the possibility of targeting those qualitative differences for tumor therapy.

Down-regulation of the tumor suppressor PTEN by the tumor necrosis factor-alpha/nuclear factor-kappaB (NF-kappaB)-inducing kinase/NF-kappaB pathway is linked to a default IkappaB-alpha autoregulatory loop

The PTEN (phosphatase and tensin homolog deleted on chromosome ten) tumor suppressor gene affects multiple cellular processes including cell growth, proliferation, and cell migration by antagonizing phosphatidylinositol 3-kinase (PI3K). However, mechanisms by which PTEN expression is regulated have not been studied extensively. Similar to PTEN, tumor necrosis factor-alpha (TNF-alpha) affects a wide spectrum of diseases including inflammatory processes and cancer by acting as a mediator of apoptosis, inflammation, and immunity. In this study, we show that treatment of cancer cell lines with TNF-alpha decreases PTEN expression. In addition, overexpression of TNF-alpha downstream signaling targets, nuclear factor-kappaB (NF-kappaB)-inducing kinase (NIK) and p65 nuclear factor NF-kappaB, lowers PTEN expression, suggesting that TNF-alpha-induced down-regulation of PTEN is mediated through a TNF-alpha/NIK/NF-kappaB pathway. Down-regulation of PTEN by NIK/NF-kappaB results in activation of the PI3K/Akt pathway and augmentation of TNF-alpha-induced PI3K/Akt stimulation. Importantly, we demonstrate that this effect is associated with a lack of an inhibitor of kappaB (IkappaB)-alpha autoregulatory loop. Moreover, these findings suggest the interaction between PI3K/Akt and NF-kappaB via transcriptional regulation of PTEN and offer one possible explanation for increased tumorigenesis in systems in which NF-kappaB is chronically activated. In such a tumor system, these findings suggest a positive feedback loop whereby Akt activation of NF-kappaB further stimulates Akt via down-regulation of the PI3K inhibitor PTEN.

Regulation of c-myc gene by nitric oxide via inactivating NF-kappa B complex in P19 mouse embryonal carcinoma cells

Nitric oxide (NO) may regulate gene expression by directly modifying redox state-sensitive residues of transcription factors. Here we show that the NO donor, sodium nitroprusside (SNP), rapidly represses c-myc gene transcription in a protein synthesis-independent manner in P19 embryonal carcinoma cells by inactivation of NF-kappa B. SNP treatment reduces the DNA binding ability of the constitutively active NF-kappa B heterodimer, p65/p50, and its consequent transactivation of the c-myc promoter. Repression can be blocked by the peroxynitrite scavenger, deferoxamine, but not by dithiothreitol, which triggers reduction of S-nitrosylated residues. In HEK293 cells, where tumor necrosis factor-alpha can activate NF-kappa B, SNP likewise suppresses the binding of the active NF-kappa B complex, restoring the binding of the repressive p50/p50 homodimer complex. This effect of SNP in HEK293 cells is also blocked by deferoxamine. Chromatin immunoprecipitation analysis of SNP-treated P19 cells reveals reduced association of p65, but not of p50, with the promoter region of the endogenous c-myc gene. SNP-induced p65 dissociation was associated with the recruitment of histone deacetylase 1 and 2 to the endogenous c-myc gene promoter and the subsequent deacetylation of its chromatin histone. This study is the first to demonstrate that NO modulates the transcriptional activity of the c-myc gene promoter by dissociating the active form of NF-kappa B and replacing it with a repressive NF-kappa B complex, correlated with the recruitment of gene-silencing histone deacetylases. In light of findings that NF-kappa B stimulates Myc oncoprotein expression in cancers, our findings suggest that NO should be investigated as a prospective therapeutic cancer agent.

The clinical significance between activation of nuclear factor kappa B transcription factor and overexpression of HER-2/neu oncoprotein in Taiwanese patients with breast cancer

BACKGROUND

This study investigated the role of nuclear factor-kappa B (NF-kappaB) activity in human breast cancer with overexpression of HER-2/neu oncoprotein, as well as its role on expression of different histological grades of cancer cells taken from Taiwanese breast cancer patients.

MATERIALS AND METHODS

Specimens were collected from 82 female breast cancer patients. The HER-2/neu oncoprotein was measured by immunohistochemistry. NF-kappaB activity expression was assessed by the electrophoretic mobility shift assay, and confirmed by the supershift technique using anti-P65 antibody in both breast cancer tissue and the adjacent normal tissue. The histological grades were measured by Modified Bloom-Richardson Grading Scheme.

RESULTS

Of the 82 cancer specimens, 81 (98.7%) showed higher or equal expressions of NF-kappaB activity when compared to the adjacent normal tissue. Fifty-five cases (67.1%) had higher levels of NF-kappaB activity in the cancerous tissue than in the adjacent normal tissue (p<0.005). With regard to tumor size, steroid receptors, stages, histological types, and node status, there were no statistically significant differences in NF-kappaB activity between cancerous tissues and adjacent normal tissues. However, significantly higher expressions of NF-kappaB activity were seen in those cases with positive HER2/neu oncoprotein, poorly differentiated histological grades, high nuclear pleomorphisms, and high mitotic counts (p<0.05). Positive HER-2/neu overexpression of oncoprotein had higher NF-kappaB activity (86%) than negative overexpression (60%) (p<0.05). It has been shown that the NF-kappaB activity increases in the HER-2/neu oncoprotein overexpression in human breast cancer.

CONCLUSION

Overexpression of HER-2/neu gene could induce NF-kappaB activity in human breast cancer cells, as has been confirmed in other research on cell lines.

The reactive adventitia: fibroblast oxidase in vascular function

The vascular adventitia is activated in a variety of cardiovascular disease states and has recently been shown to be a barrier to nitric oxide bioactivity. Vascular fibroblasts produce substantial amounts of NAD(P)H oxidase-derived reactive oxygen species (ROS) that appear to be involved in fibroblast proliferation, connective tissue deposition, and perhaps vascular tone. However, the physiological and pathophysiological roles of the adventitia have not been extensively studied, possibly because of its location in large blood vessels remote from the vascular endothelium. In recent years, substantial information has been gathered on pathways leading to oxidase activation in smooth muscle cells and fibroblasts and the downstream signaling pathways leading to hypertrophy and proliferation. A clearer understanding of the molecular mechanisms involved will likely lead to therapeutic strategies aimed at preventing vascular dysfunction in diseases such as atherosclerosis, in which these pathways are activated.

Diseases caused by silica: mechanisms of injury and disease development

While silica particles are considered to be fibrogenic and carcinogenic agents, the mechanisms responsible are not well understood. This article summarizes literature on silica-induced accelerated silicosis, chronic silicosis, silico-tuberculosis, bronchogenic carcinoma, and immune-mediated diseases. This article also discusses the generation of reactive oxygen species (ROS) that occurs directly from the interaction of silica with aqueous medium and from silica-stimulated cells, the molecular mechanisms of silica-induced lung injuries with focus on silica-induced NF-kappaB activation, including its mechanisms, possible attenuation and relationship to silica-induced generation of cyclooxygenase II and TNF-alpha. Silica-induced AP-1 activation, protooncogene expression, and the role of ROS in these processes are also briefly discussed.

Microenvironment produced by acute myeloid leukemia cells prevents T cell activation and proliferation by inhibition of NF-kappaB, c-Myc, and pRb pathways

Tumors produce a variety of immunosuppressive factors which can prevent the proliferation and maturation of a number of normal hemopoietic cell types. We have investigated whether primary acute myeloid leukemia (AML) cells have an effect on normal T cell function and signaling. Tumor cell supernatant (TSN) from AML cells inhibited T cell activation and Th1 cytokine production and also prevented activated T cells from entering the cell cycle. These effects occurred in the absence of AML cell-T cell contact. We have demonstrated that AML TSN contained none of the immunosuppressors described to date, namely gangliosides, nitric oxide, TGF-beta, IL-10, vascular endothelial growth factor, or PGs. Furthermore, IL-2 did not overcome the block, despite normal IL-2R expression. However, the effect was overcome by preincubation with inhibitors of protein secretion and abolished by trypsinization, indicating that the active substance includes one or more proteins. To determine the mechanism of inhibition, we have studied many of the major pathways involved in T cell activation and proliferation. We show that nuclear translocation of NFATc and NF-kappaB are markedly reduced in T cells activated in the presence of primary AML cells. In contrast, calcium mobilization and activation of other signal transduction pathways, namely extracellular signal-regulated kinase1/2, p38, and STAT5 were unaffected, but activation of c-Jun N-terminal kinase 1/2 was delayed. Phosphorylation of pRb by cyclin-dependent kinase 6/4-cyclin D and of p130 did not occur and c-Myc, cyclin D3, and p107 were not induced, consistent with cell cycle inhibition early during the transition from G(0) to G(1). Our data indicate that TSN generated by AML cells induces T cell immunosuppression and provides a mechanism by which the leukemic clone could evade T cell-mediated killing.

Protein kinase CK2: signaling and tumorigenesis in the mammary gland

Breast cancer is a major cause of cancer death in women, and the genetic abnormalities leading to the common sporadic forms of the disease are still under active investigation. CK2 has been reported to be upregulated in human breast cancer, which these studies confirm; CK2 is also upregulated in rat carcinogen-induced breast tumors. Transgenic mice overexpressing CK2alpha in the mammary gland develop mammary hyperplasia, dysplasia, and eventually adenocarcinomas, demonstrating that dysregulated expression of CK2 can contribute to transformation of the mammary epithelium. These mammary tumors have evidence of activation of the Wnt and NFkappaB pathways and upregulation of c-Myc. CK2 is capable of phosphorylating the key signaling molecule in the Wnt pathway, the transcriptional cofactor beta-catenin, and regulating its turnover. CK2 is known to phosphorylate IkappaB and thereby regulate basal NFkappaB levels; in the mammary cell lines and tumors, CK2 activity correlates with NFkappaB levels and inhibition of CK2 downregulates NFkappaB. Thus, CK2 may promote breast cancer through dysregulation of key pathways of transcriptional control in the mammary epithelium, and inhibition of CK2 has a potential role in the treatment of breast and other cancers.

Keratinocyte-derived growth factors play a role in the formation of hypertrophic scars

In predisposed individuals, wound healing can lead to hypertrophic scar or keloid formation, characterized by an overabundant extracellular matrix. It has recently been shown that hypertrophic scars are accompanied by abnormal keratinocyte differentiation and proliferation, and significantly increased acanthosis, compared with normal scars. This study addressed the question of whether the development of normal and hypertrophic scars is regulated by differences in the growth factor profiles of both the epidermis and the dermis. The presence of interleukin-1alpha (IL-1alpha), IL-1beta, tumour necrosis factor-alpha (TNF-alpha), platelet-derived growth factor (PDGF), transforming growth factor-beta1 (TGF-beta1), and basic fibroblast growth factor (bFGF) was investigated in biopsies taken from breast reduction scars at 3 and 12 months following surgery. The samples were analysed by immunohistological methods and categorized as scars that remained hypertrophic (HH), became normal (HN) or remained normal after 12 months (NN). The epidermal expression of IL-1alpha was significantly increased in NN scars compared with HN and HH scars 3 and 12 months following operation, whereas the dermal expression showed no difference. PDGF was significantly increased in the dermis of normal scars after 3 months and in both the epidermis and the dermis of hypertrophic scars after 12 months. IL-1beta, TNF-alpha, TGF-beta and bFGF showed no differences. It is hypothesized that impaired production of keratinocyte-derived growth factors, such as IL-1alpha, leads to a decrease in the catabolism of the dermal matrix, whereas augmented epidermal PDGF production leads to increased formation of the dermal matrix in hypertrophic scars. These observations support the possibility that the epidermis is involved in preventing the formation of hypertrophic scars.

Regulation of c-myc expression by PDGF through Rho GTPases

Src family protein-tyrosine kinases have a central role in several biological functions, including cell adhesion and spreading, chemotaxis, cell cycle progression, differentiation and apoptosis. Surprisingly, these kinases also participate in mitogenic signalling by receptors that themselves exhibit an intrinsic protein-tyrosine kinase activity, including those for platelet-derived growth factor (PDGF), epidermal growth factor and colony-stimulating factor-1. Indeed, Src kinases are strictly required for the nuclear expression of the c-myc proto-oncogene and thus for DNA synthesis in response to PDGF. However, the nature of the signalling pathways by which Src kinases participate in the induction of c-myc expression by tyrosine kinase receptors is still unknown. Here we show that PDGF enhances c-myc expression and stimulates the c-myc promoter in a Src-dependent manner, and that neither Ras nor the mitogen-activated protein kinase pathway mediate these effects. In contrast, we present evidence that PDGF stimulates Vav2 through Src, thereby initiating the activation of a Rac-dependent pathway that controls the expression of the c-myc proto-oncogene.

Protein kinase CK2 in mammary gland tumorigenesis

Protein kinase CK2 is a ubiquitous and evolutionarily conserved serine/threonine kinase that is upregulated in many human cancers and can serve as an oncogene in lymphocytes. Recently, we have demonstrated that CK2 potentiates Wnt/beta-catenin signaling in mammary epithelial cells. To determine whether CK2 overexpression contributes to mammary tumorigenesis, we have performed comparative studies of human and rat breast cancer specimens and we have engineered transgenic mice with dysregulated expression of CK2alpha in the mammary gland. We find that CK2 is highly expressed in human breast tumor specimens and in carcinogen-induced rat mammary tumors. Overexpression of CK2alpha in the mammary gland of transgenic mice, under control of the MMTV-LTR, causes hyperplasia and dysplasia of the female mammary gland. Thirty per cent of the female MMTV-CK2alpha transgenic mice develop mammary adenocarcinomas at a median of 23 months of age, often associated with Wnt pathway activation, as evidenced by upregulation of beta-catenin protein. NF-kappaB activation and upregulation of c-Myc also occur frequently. Thus, in mice, rats, and humans, dysregulated expression of CK2 is associated with and is capable of contributing to mammary tumorigenesis. Targeted inhibition of CK2 could be useful in the treatment of breast cancer.

Her-2/neu overexpression induces NF-kappaB via a PI3-kinase/Akt pathway involving calpain-mediated degradation of IkappaB-alpha that can be inhibited by the tumor suppressor PTEN

The Nuclear Factor (NF)-kappaB family of transcription factors controls expression of genes which promote cell growth, survival, and neoplastic transformation. Recently we demonstrated aberrant constitutive activation of NF-kappaB in primary human and rat breast cancer specimens and in cell lines. Overexpression of the epidermal growth factor receptor (EGFR) family member Her-2/neu, seen in approximately 30% of breast cancers, is associated with poor prognosis. Previously, Her-2/neu has been shown to signal via a phosphatidylinositol 3 (PI3)-kinase to Akt/protein kinase B (PKB) pathway. Since this signaling pathway was recently shown to activate NF-kappaB, here we have tested the hypothesis that Her-2/neu can activate NF-kappaB in breast cancer. Overexpression of Her-2/neu and EGFR-4 in Ba/F3 cells led to constitutive PI3- and Akt kinase activities, and induction of classical NF-kappaB (p50/p65). Similarly, a tumor cell line and tumors derived from MMTV-Her-2/neu transgenic mice displayed elevated levels of classical NF-kappaB. Engagement of Her-2/neu receptor downregulated the level of NF-kappaB. NF-kappaB binding and activity in the cultured cells was reduced upon inhibition of the PI3- to Akt kinase signaling pathway via ectopic expression of kinase inactive mutants, incubation with wortmannin, or expression of the tumor suppressor phosphatase PTEN. Inhibitors of calpain, but not the proteasome, blocked IkappaB-alpha degradation. Inhibition of Akt did not affect IKK activity. These results indicate that Her-2/neu activates NF-kappaB via a PI3- to Akt kinase signaling pathway that can be inhibited via the tumor suppressor PTEN, and is mediated by calpain rather than the IkappaB kinase complex.

Regulation of PDGFR-alpha in rat pulmonary myofibroblasts by staurosporine

Upregulation of the platelet-derived growth factor (PDGF) receptor-alpha (PDGFR-alpha) is a mechanism of myofibroblast hyperplasia during pulmonary fibrosis. We previously identified interleukin (IL)-1beta as a major inducer of the PDGFR-alpha in rat pulmonary myofibroblasts in vitro. In this study, we report that staurosporine, a broad-spectrum kinase inhibitor, upregulates PDGFR-alpha gene expression and protein. A variety of other kinase inhibitors did not induce PDGFR-alpha expression. Staurosporine did not act via an IL-1beta autocrine loop because the IL-1 receptor antagonist protein did not block staurosporine-induced PDGFR-alpha expression. Furthermore, staurosporine did not activate a variety of signaling molecules that were activated by IL-1beta, including nuclear factor-kappaB, extracellular signal-regulated kinase, and c-Jun NH2-terminal kinase. However, both staurosporine- and IL-1beta-induced phosphorylation of p38 mitogen-activated protein kinase and upregulation of PDGFR-alpha by these two agents was inhibited by the p38 inhibitor SB-203580. Finally, staurosporine inhibited basal and PDGF-stimulated mitogenesis over the same concentration range that induced PDGFR-alpha expression. Collectively, these data demonstrate that staurosporine is a useful tool for elucidating the signaling mechanisms that regulate PDGFR expression in lung connective tissue cells and possibly for evaluating the role of the PDGFR-alpha as a growth arrest-specific gene.

The RelA NF-kappaB subunit and the aryl hydrocarbon receptor (AhR) cooperate to transactivate the c-myc promoter in mammary cells

NF-kappaB/Rel transcription factors regulate many genes involved in control of cellular proliferation, neoplastic transformation, and apoptosis, including the c-myc oncogene. Recently, we have observed that levels of NF-kappaB and aryl hydrocarbon receptor (AhR), which mediates malignant transformation by environmental carcinogens, are highly elevated and appear constitutively active in breast cancer cells. Rel factors have been found to functionally interact with other transcription factors. Here we demonstrate a physical and functional association between the RelA subunit of NF-kappaB and AhR resulting in the activation of c-myc gene transcription in breast cancer cells. RelA and AhR proteins were co-immunoprecipitated from cytoplasmic and nuclear extracts of non-malignant MCF-10F breast epithelial and malignant Hs578T breast cancer cells. In transient co-transfection, RelA and AhR gene products demonstrated cooperation in transactivation of the c-myc promoter, which was dependent on the NF-kappaB elements, and in induction of endogenous c-Myc protein levels. A novel AhR/RelA-containing NF-kappaB element binding complex was identified by electrophoretic mobility shift analysis of nuclear extracts from RelA and AhR co-transfected Hs578T cells. Thus, the RelA and AhR proteins functionally cooperate to bind to NF-kappaB elements and induce c-myc gene expression. These findings suggest a novel signaling mechanism whereby the Ah receptor can stimulate proliferation and tumorigenesis of mammary cells.

Proliferative response of different human osteoblast-like cell models to proinflammatory cytokines

Children with inflammatory bowel disease are known to be at risk of osteopenia. The cause of this osteopenia is likely to be multifactorial, but the inflammatory process with its characteristic overproduction of cytokines has been implicated. To investigate this possible contribution of the disease activity to the development of osteopenia, we performed in vitro assays of the proliferation of osteoblast-like cells of differing origins in response to the inflammatory cytokines tumor necrosis factor-alpha and IL-1/beta. Osteoblast-like cells derived from pediatric bone explants, adherent stromal cells derived from bone marrow (osteoprogenitors), MG-63 osteosarcoma cells, and SV-40 virally transformed osteoprogenitor cells (HCC1) were studied. Tumor necrosis factor-alpha stimulated the proliferation of cells in primary cultures (i.e. from explants and marrow samples) in a linear, dose-dependent manner. In contrast, inhibition of proliferation was observed with the established cell lines (MG-63 and HCC1). IL-1beta stimulated proliferation of all cells apart from the immortalized human bone marrow cell line, HCC1, in which case potent inhibition was observed. We conclude that proinflammatory cytokines are potent regulators of osteoblast-like cell proliferation, and that the responses are specific to cell type. The opposite results obtained with established cell lines compared with the primary cultures suggest that careful consideration should be given to choosing the most suitable cell line for in vitro studies relating to in vivo mechanisms predisposing to osteopenia.

Co-stimulation of cyclic-AMP-linked metabotropic glutamate receptors in rat striatum attenuates excitotoxin-induced nuclear factor-kappaB activation and apoptosis

Interactions between glutamatergic mechanisms mediated by receptors of the ionotropic and metabotropic classes in the central nervous system are complex and incompletely understood. To explore the consequences of these interactions on excitotoxicity, we examined the influence of group II and group III selective metabotropic glutamate receptor agonists on the N-methyl-D-aspartate-induced apoptotic destruction of GABAergic neurons in rat striatum. The intrastriatal administration of a group III metabotropic glutamate receptor agonist (amino-4-phosphonobutyric acid, 900-1800 nmol), but not of a group II agonist [(2S,1'S,2'S)-(carboxycyclopropyl)glycine, 100-1800 nmol] produced internucleosomal DNA fragmentation. Similarly, amino-4-phosphonobutyric acid (600 nmol) but not (2S,1'S,2'S)-(carboxycyclopropyl)glycine (100-1800 nmol) destroyed some striatal neurons as indicated by a loss of D1 dopamine receptors and 67,000 mol. wt glutamate decarboxylase (glutamate decarboxylase-67) messenger RNA. On the other hand, the intensity of internucleosomal DNA fragmentation induced by N-methyl-D aspartate (150 nmol) was substantially decreased by the intrastriatal co-administration of either (2S,1'S,2'S)-(carboxycyclopropyl)glycine or amino-4-phosphonobutyric acid (100-600 nmol). Both (2S, 1'S,2'S)-(carboxycyclopropyl)glycine and amino-4-phosphonobutyric acid also reduced the N-methyl-D-aspartate-induced loss of striatal D1 dopamine receptors by 67% and 68% (both P < 0.001), and glutamate decarboxylase-67 messenger RNA by 68% and 61%, respectively. Furthermore, both (2S,1'S,2'S)-(carboxycyclopropyl)glycine and amino-4-phosphonobutyric acid also attenuated the N-methyl-D-aspartate-induced decline in striatal IKB-alpha protein levels by 62% and 37%, as well as the increase in nuclear transcription factor nuclear factor-kappaB binding activity by 135% and 94% (both P < 0.001), and the subsequent rise in p53 and c-Myc protein levels. These results suggest that stimulation of cyclic-AMP-linked metabotropic glutamate receptors inhibits ionotropic glutamate receptor-mediated activation of apoptotic cascades involving IkappaB-alpha degradation and nuclear factor-kappaB nuclear translocation, as well as p53 and c-Myc induction. Certain selective metabotropic glutamate receptor agonists might thus find utility as adjuncts to N-methyl-D-aspartate antagonists in the protection against the neurotoxicity initiated by excessive ionotropic glutamate receptor stimulation.

Kainic acid-induced apoptosis in rat striatum is associated with nuclear factor-kappaB activation

The present study evaluated whether nuclear factor-kappaB (NF-kappaB) activation contributes to the apoptotic-like death of striatal neurons induced by kainic acid (KA) receptor stimulation. Intrastriatally infused KA (1.25-5.0 nmol) produced substantial neuronal loss as indicated by an 8-73% decrease in 67-kDa glutamic acid decarboxylase (p<0.05). KA (1.25-5.0 nmol) elicited internucleosomal DNA fragmentation that was inhibited by the AMPA/KA receptor antagonist NBQX (1,2,3,4-tetrahydro-6-nitro-2,3-dibenzo[f]quinoxaline-7-sulfonamide) but not by the NMDA receptor antagonist MK-801. A decrease in IkappaB-alpha protein levels, which was accompanied by an increase in NF-kappaB binding activity, was found from 6 to 72 h after KA (2.5 nmol) infusion. NF-kappaB was composed mainly of p65 and c-Rel as revealed by supershift assay. In addition, c-Myc and p53 increased from five- to sevenfold from 24 to 72 h after KA (2.5 nmol) administration. Immunohistochemistry revealed high levels of c-Myc and p53 immunoreactivity, mainly in medium-sized striatal neurons. Pretreatment with the cell-permeable recombinant peptide NF-kappaB SN50 (5-20 microg) blocked NF-kappaB nuclear translocation, but had no effect on AP-1 binding. NF-kappaB SN50 also inhibited the KA-induced up-regulation of c-Myc and p53, as well as internucleosomal DNA fragmentation. The apoptotic-like destruction of rat striatal neurons induced by KA receptor stimulation thus appears to involve biochemical mechanisms similar to those mediating the excitotoxic response to NMDA receptor stimulation. The present results provide additional support for the view that NF-kappaB activation contributes to c-Myc and p53 induction and subsequent apoptosis in an excitotoxic model of Huntington's disease.

Drosophila myc regulates cellular growth during development

Transcription factors of the Myc proto-oncogene family promote cell division, but how they do this is poorly understood. Here we address the functions of Drosophila Myc (dMyc) during development. Using mosaic analysis in the fly wing, we show that loss of dMyc retards cellular growth (accumulation of cell mass) and reduces cell size, whereas dMyc overproduction increases growth rates and cell size. dMyc-induced growth promotes G1/S progression but fails to accelerate cell division because G2/M progression is independently controlled by Cdc25/String. We also show that the secreted signal Wingless patterns growth in the wing primordium by modulating dMyc expression. Our results indicate that dMyc links patterning signals to cell division by regulating primary targets involved in cellular growth and metabolism.

NF-kappaB is a target of AKT in anti-apoptotic PDGF signalling

The mechanisms of cell proliferation and transformation are intrinsically linked to the process of apoptosis: the default of proliferating cells is to die unless specific survival signals are provided. Platelet-derived growth factor (PDGF) is a principal survival factor that inhibits apoptosis and promotes proliferation, but the mechanisms mediating its anti-apoptotic properties are not completely understood. Here we show that the transcription factor NF-kappaB is important in PDGF signalling. NF-kappaB transmits two signals: one is required for the induction of proto-oncogene c-myc and proliferation, and the second, an anti-apoptotic signal, counterbalances c-Myc cytotoxicity. We have traced a putative pathway whereby PDGF activates NF-kappaB through Ras and phospatidylinositol-3-kinase (PI(3)K) to the PKB/Akt protein kinase and the IkappaB kinase (IKK); NF-kappaB thus appears to be a target of the anti-apoptotic Ras/PI(3)K/Akt pathway. We show that, upon PDGF stimulation, Akt transiently associates in vivo with IKK and induces IKK activation. These findings establish a role for NF-kappaB in growth factor signalling and define an anti-apoptotic Ras/PI(3)K/Akt/IKK/NF-kappaB pathway, thus linking anti-apoptotic signalling with transcription machinery.

Nuclear factor kappaB nuclear translocation upregulates c-Myc and p53 expression during NMDA receptor-mediated apoptosis in rat striatum

Nuclear factor kappaB (NF-kappaB) appears to participate in the excitotoxin-induced apoptosis of striatal medium spiny neurons. To elucidate molecular mechanisms by which this transcription factor contributes to NMDA receptor-triggered apoptotic cascades in vivo, rats were given the NMDA receptor agonist quinolinic acid (QA) by intrastriatal infusion, and the role of NF-kappaB in the induction of apoptosis-related genes and gene products was evaluated. QA administration induced time-dependent NF-kappaB nuclear translocation. The nuclear NF-kappaB protein after QA treatment was comprised mainly of p65 and c-Rel subunits as detected by gel supershift assay. Levels of c-Myc and p53 mRNA and protein were markedly increased at the time of QA-induced NF-kappaB nuclear translocation. Immunohistochemical analysis showed that c-Myc and p53 induction occurred in the excitotoxin-sensitive medium-sized striatal neurons. NF-kappaB nuclear translocation was blocked in a dose-dependent manner by the cell-permeable recombinant peptide NF-kappaB SN50, but not by the NF-kappaB SN50 control peptide. NF-kappaB SN50 significantly inhibited the QA-induced elevation in levels of c-Myc and p53 mRNA and protein. Pretreatment or posttreatment with NF-kappaB SN50, but not the control peptide, also substantially reduced the intensity of QA-induced internucleosomal DNA fragmentation. The results suggest that NF-kappaB may promote an apoptotic response in striatal medium-sized neurons to excitotoxic insult through upregulation of c-Myc and p53. This study also provides evidence indicating an unique signaling pathway from the cytoplasm to the nucleus, which regulates p53 and c-Myc levels in these neurons during apoptosis.

Nuclear factor kappaB nuclear translocation upregulates c-Myc and p53 expression during NMDA receptor-mediated apoptosis in rat striatum

Nuclear factor kappaB (NF-kappaB) appears to participate in the excitotoxin-induced apoptosis of striatal medium spiny neurons. To elucidate molecular mechanisms by which this transcription factor contributes to NMDA receptor-triggered apoptotic cascades in vivo, rats were given the NMDA receptor agonist quinolinic acid (QA) by intrastriatal infusion, and the role of NF-kappaB in the induction of apoptosis-related genes and gene products was evaluated. QA administration induced time-dependent NF-kappaB nuclear translocation. The nuclear NF-kappaB protein after QA treatment was comprised mainly of p65 and c-Rel subunits as detected by gel supershift assay. Levels of c-Myc and p53 mRNA and protein were markedly increased at the time of QA-induced NF-kappaB nuclear translocation. Immunohistochemical analysis showed that c-Myc and p53 induction occurred in the excitotoxin-sensitive medium-sized striatal neurons. NF-kappaB nuclear translocation was blocked in a dose-dependent manner by the cell-permeable recombinant peptide NF-kappaB SN50, but not by the NF-kappaB SN50 control peptide. NF-kappaB SN50 significantly inhibited the QA-induced elevation in levels of c-Myc and p53 mRNA and protein. Pretreatment or posttreatment with NF-kappaB SN50, but not the control peptide, also substantially reduced the intensity of QA-induced internucleosomal DNA fragmentation. The results suggest that NF-kappaB may promote an apoptotic response in striatal medium-sized neurons to excitotoxic insult through upregulation of c-Myc and p53. This study also provides evidence indicating an unique signaling pathway from the cytoplasm to the nucleus, which regulates p53 and c-Myc levels in these neurons during apoptosis.

Critical role of glass fiber length in TNF-alpha production and transcription factor activation in macrophages

Recent studies have demonstrated that dielectrophoresis is an efficient method for the separation of fibers according to fiber length. This method allows the investigation of fiber-cell interactions with fiber samples of the same composition but of different lengths. In the present study, we analyzed the effects of length on the interaction between glass fibers and macrophages by focusing on production of the inflammatory cytokine tumor necrosis factor (TNF)-alpha in a mouse macrophage cell line (RAW 264.7). The underlying molecular mechanisms controlling TNF-alpha production were investigated at the gene transcription level. The results show that glass fibers induced TNF-alpha production in macrophages and that this induction was associated with activation of the gene promoter. Activation of the transcription factor nuclear factor (NF)-kappaB was responsible for this induced promoter activity. The inhibition of both TNF-alpha production and NF-kappaB activation by N-acetyl-L-cysteine, an antioxidant, indicates that generation of oxidants may contribute to the induction of this cytokine and activation of this transcription factor by glass fibers. Long fibers (17 micrometer) were significantly more potent than short fibers (7 micrometer) in inducing NF-kappaB activation, the gene promoter activity, and the production of TNF-alpha. This fiber length-dependent difference in the stimulatory potency correlated with the fact that macrophages were able to completely engulf short glass fibers, whereas phagocytosis of long glass fibers was incomplete. These results suggest that fiber length plays a critical role in the potential pathogenicity of glass fibers.

STAT3 is required for the gp130-mediated full activation of the c-myc gene

The signal transducers and activators of transcription (STAT) family members have been implicated in regulating the growth, differentiation, and death of normal and transformed cells in response to either extracellular stimuli, including cytokines and growth factors, or intracellular tyrosine kinases. c-myc expression is coordinately regulated by multiple signals in these diverse cellular responses. We show that STAT3 mostly mediates the rapid activation of the c-myc gene upon stimulation of the interleukin (IL)-6 receptor or gp130, a signal transducing subunit of the receptor complexes for the IL-6 cytokine family. STAT3 does so most likely by binding to cis-regulatory region(s) of the c-myc gene. We show that STAT3 binds to a region overlapping with the E2F site in the c-myc promoter and this site is critical for the c-myc gene promoter- driven transcriptional activation by IL-6 or gp130 signals. This is the first identification of the linkage between a member of the STAT family and the c-myc gene activation, and also explains how the IL-6 family of cytokines is capable of inducing the expression of the c-myc gene.

Role of Nuclear Factor-κB and Mitogen-Activated Protein Kinase Signaling Pathways in IL-1β-Mediated Induction of α-PDGF Receptor Expression in Rat Pulmonary Myofibroblasts

Induction of the α-platelet-derived growth factor receptor (PDGF-Rα) by IL-1β in lung myofibroblasts enhances mitogenic and chemotactic responses to PDGF, and this could be a mechanism of myofibroblast hyperplasia during lung fibrogenesis. Since the regulation of many genes by IL-1β involves activation of NF-κB and mitogen-activated protein (MAP) kinases, we examined these signaling pathways in the control of PDGF-Rα expression by IL-1β in cultured rat lung myofibroblasts. Treatment of cells with pyrrolidine dithiocarbamate (PDTC), an antioxidant that inhibits NF-κB activation, completely blocked PDGF-Rα up-regulation by IL-1β as assayed by [125I]PDGF-AA binding and PDGF-Rα mRNA expression, suggesting a role for NF-κB. However, while IL-1β and TNF-α both induced nuclear binding of the Rel proteins p50 and p65 to an NF-κB consensus oligonucleotide in gel shift assays and caused transient degradation of inhibitor of NF-κB-α (IκB-α) in the cytoplasm of myofibroblasts, only IL-1β up-regulated PDGF-Rα. These results suggest that NF-κB activation alone is not sufficient for up-regulation of PDGF-Rα. An investigation of MAP kinase signaling pathways revealed that IL-1β or PDTC activated extracellular signal-regulated kinase-2 (ERK-2) and c-jun NH2 terminal kinase-1 (JNK-1) phosphorylation of PHAS-1 and c-Jun substrates, respectively. Pretreatment of cells with the MAP kinase kinase-1 (MEK1) inhibitor PD 98059 blocked IL-1β-induced activation of ERK-2 by more than 90% but enhanced IL-1β-stimulated induction of PDGF-Rα expression fourfold. Taken together, these data suggest that IL-1β activates both positive and negative signaling pathways that control the expression of PDGF-Rα. IL-1β appears to mediate its negative effects on PDGF-Rα expression via MAP kinase activation, while the factor(s) that mediate induction of PDGF-Rα remain to be elucidated.

Requirement for Dual Signals by Anti-CD40 and IL-4 for the Induction of Nuclear Factor-κB, IL-6, and IgE in Human B Lymphocytes

Stimulation of human peripheral B cells via the CD40 receptor and IL-4R together lead to IgE synthesis and secretion, but the intracellular signaling mechanisms by which these signals lead to IgE production are unclear. Roles for the transcription factor NF-κB and IL-6 have been postulated in the induction of IgE synthesis by IL-4/CD40. We found that neither anti-CD40 Ab nor IL-4 alone was able to induce significant proliferation of human B cells. However, the combination of anti-CD40 and IL-4 was a potent inducer of B cell proliferation in addition to IgE production from purified human B cells. Furthermore, IL-4 and anti-CD40 synergized for the production of IL-6. While neither IL-4 alone nor anti-CD40 alone was able to induce significant NF-κB DNA binding activity, the combination of IL-4 and anti-CD40 induced a strong activation of NF-κB, a transcription factor that regulates IL-6 production. These data indicate that both IL-4 and anti-CD40 are required to induce NF-κB activation and IL-6 transcription and production, and implicate these events in a signaling pathway augmenting IgE production in human B lymphocytes.

Biosafety monitoring of patients receiving intracerebral injections of murine retroviral vector producer cells

Patients with recurrent malignant brain cancer, who were receiving gene therapy by intracerebral injection of murine retroviral vector producer cells (VPCs), were monitored for the presence of replication-competent retrovirus (RCR). RCR sequences were not detected by polymerase chain reaction (PCR) in any of the 608 peripheral blood leukocyte (PBL) samples analyzed. Vector DNA sequences were detected transiently in PBL samples from a subset of 34 patients. Humoral immune responses to a retroviral core protein p30 and murine VPC were detected in some patients, most frequently in patients receiving repeated administrations of VPC. RCR was not detected in biological assays of PBLs from 41 patients who had either anti-retroviral antibodies in sera and/or vector DNA in PBLs. Our data suggest that in situ generation of RCR was not detected following intracerebral inoculation of VPCs in any of the 128 patients evaluated.

The human cytomegalovirus UL55 (gB) and UL75 (gH) glycoprotein ligands initiate the rapid activation of Sp1 and NF-kappaB during infection

The cellular transcription factors Sp1 and NF-kappaB were upregulated shortly after the binding of purified live or UV-inactivated human cytomegalovirus (HCMV) to the cell surface. The rapid time frame of transcription factor induction is similar to that seen in other systems in which cellular factors are induced following receptor-ligand engagement. This similarity suggested that a cellular receptor-viral ligand interaction might be involved in Sp1 and NF-kappaB activation during the earliest stages of HCMV infection. To focus on the possible role viral ligands play in initiating cellular events following infection, we first used purified viral membrane extracts to demonstrate that constituents on the membrane are responsible for cellular activation. Additionally, these studies showed, through the use of neutralizing antibodies, that the viral membrane mediators of this activation are the major envelope glycoproteins gB (UL55) and gH (UL75). To confirm these results, neutralizing anti-gB and -gH antibodies were used to block the interactions of these glycoproteins on whole purified virus with their cell surface receptors. In so doing, we found that Sp1 and NF-kappaB induction was inhibited. Lastly, through the use of purified viral gB protein and an anti-idiotypic antibody that mimics the image of the viral gH protein, it was found that the engagement of individual viral ligands with their appropriate cell surface receptors was sufficient to activate cellular Sp1 and NF-kappaB. These results support our hypothesis that HCMV glycoproteins mediate an initial signal transduction pathway which leads to the upregulation of host cell transcription factors and suggests a model wherein the orderly sequence of virus-mediated changes in cellular activation initiates with viral binding via envelope glycoproteins to the cognate cellular receptor(s).

Evaluation of PCR and ELISA assays for screening clinical trial subjects for replication-competent retrovirus

Gene delivery via murine-based recombinant retroviral vectors is currently widely used in gene therapy clinical trials. The vectors are engineered to be replication defective by replacing the structural and nonstructural genes of a cloned infectious retrovirus with a therapeutic gene of interest. The retroviral particles are currently generated in packaging cell lines, which supply all retroviral proteins in trans. Recombination between short homologous regions of the retroviral vector and packaging cell line elements can theoretically generate replication-competent retrovirus (RCR) and hence the Food and Drug Administration (FDA) requires the monitoring of clinical trial subjects for the presence of RCR. Sensitive polymerase chain reaction (PCR) assays have been used for the detection of murine leukemia virus (MLV) nucleotide sequences in peripheral blood mononuclear cells (PBMCs). A novel serological enzyme-linked immunosorbent assay (ELISA) for the detection of anti-MLV specific immunoglobulin (Ig) has been developed to be used as an alternative to the PCR assay. Both assays were used to monitor human immunodeficiency virus (HIV)-positive clinical trial subjects who had received multiple injections of HIV-IT (V), a retroviral vector encoding HIV-1 IIIBenv/rev. Western blot analysis and an in vitro vector neutralization assay were used to characterize further a subset of serum samples tested by ELISA. Results show no evidence of RCR infection in clinical trial subjects. PCR and ELISA assays are discussed in terms of their advantages and limitations as routine screening assays for RCR. The PCR assay is our current choice for monitoring clinical trial subjects receiving direct administration of vector, and the ELISA is our choice for those receiving ex vivo treatment regimens.

Anti-vector immunoglobulin induced by retroviral vectors

Replication-incompetent retroviruses have been employed as gene therapy vectors in experimental settings for more than a decade. More recently, these vectors have been tested in the clinic as immunotherapeutic agents and anticancer agents. One potential problem with the use of such vectors is the possible development of immune responses directed against the vector particles themselves. Here, we examine immunoglobulin (Ig) responses specific for retroviral vectors derived from murine leukemia virus (MLV). Anti-MLV Ig is seen following intramuscular (i.m.) administration of retroviral vectors in mice, and in nonhuman primates; as expected, these responses are dependent upon the vector dose delivered. Furthermore, serum from vector-treated animals is capable of partially neutralizing vector-mediated transduction of target cells in an in vitro assay. Nevertheless, even in the presence of significant levels of anti-vector Ig in vivo, i.m. administration of retroviral vector is still capable of driving both Ig and cytotoxic T lymphocyte (CTL) responses specific for vector-encoded gene products. This work suggests that although retroviral vectors may readily induce immune responses directed against the vector particles themselves, such responses will not significantly affect the efficiency of these vectors in an immunotherapeutic protocol.

Establishment of parameters for optimal transduction efficiency and antitumor effects with purified high-titer HSV-TK retroviral vector in established solid tumors

Suicide gene therapy using the herpes simplex thymidine kinase gene and ganciclovir is an attractive strategy for solid tumors. Early animal studies involved intratumoral injection of retroviral producer cells or unprocessed supernatant to generate an antitumor effect. Xenotransplantation of producer cells proved effective in several models, but the crude supernatants from the same cells were of insufficient titer to produce antitumor effects. We have developed new non-murine producer lines that yield replication-defective retroviral vectors encoding thymidine kinase at high titer which are then further purified and processed, resulting in pharmaceutical grade retroviral vectors with titers of up to 10(8) cfu/ml. Purified, high-titer retroviral preparations were injected directly into solid tumors in two syngeneic mouse tumor models. Significant antitumor responses and some cures were observed following systemic ganciclovir therapy. Assays using monoclonal antibodies to measure thymidine kinase protein expression at the single cell level in vitro and in vivo were developed so that therapeutic transgene expression could be quantified. Intralesional delivery resulted in transduction of over 20% of tumor cells in a protocol designed to maximize transduction on the basis of separate analyses of route, dosage, and schedule of vector administration. A consensus strategy evolved in which the combined effects of increased titer and a longer duration of retroviral vector administration interact to maximize transduction efficiency. These results indicate that purified high-titer retroviral vectors have the potential to transfer effective quantities of therapeutic genes into solid tumors in human subjects and highlight some pharmacologic factors that could be valuable in the design of clinical gene therapy protocols.

Lack of site-specific integration of the recombinant adeno-associated virus 2 genomes in human cells

The adeno-associated virus 2 (AAV)-based vector system has been suggested for its potential use in human gene therapy because the wild-type (wt) AAV genome appears to integrate into the human chromosomal DNA in a site-specific manner. We systematically investigated the integration patterns of the recombinant AAV genomes lacking one or both the viral coding sequences. Four recombinant AAV genomes were constructed containing the genes for resistance to tetracycline (TcR) and the herpesvirus thymidine kinase (TK) promoter-driven gene for resistance to neomycin (neoR; vTc.Neo), the genes for resistance to ampicillin (ApR) and TK-neoR (vAp.Neo), the genes for AAV replication (rep) genes and TK-neoR (vRep.Neo), and the AAV capsid (cap) genes and TK-neoR (vCap.Neo). The integration pattern of each of the recombinant AAV genomes in individual clonal isolates of the human nasopharyngeal carcinoma cell line (KB) analyzed on Southern blots using a neo-specific DNA probe was distinctly different. In addition, in none of the clones examined was the proviral genome covalently linked to the previously described AAV right-junction (Rt.Jn.) human chromosomal DNA fragment, the putative specific-site of integration for the wt AAV genome. Furthermore, whereas a 276-bp DNA fragment could be readily amplified from each of these clones, using a neo-specific primer-pair by polymerase chain reaction (PCR), no amplified DNA product was obtained using the neo- and the Rt.Jn. primer-pair under identical conditions. Fluorescence in situ hybridization (FISH) analyses further revealed the lack of integration of the recombinant AAV into human chromosome 19, even in the presence of a functional rep gene as determined by rescue of the recombinant AAV genome in the presence of adenovirus. These data suggest that the recombinant AAV genomes integrate at sites that are different from that characterized for the wt AAV genome. These studies may have implications in the development of the AAV-based vector system for its potential use in human gene therapy.

Gene marking

Gene marking studies were the first gene transfer protocols to enter clinical practice. To date, clinical marking studies have been limited to the hematopoietic stem cell and its progeny. In this setting, they have provided valuable information about stem cell biology, the factors that influence gene transfer efficiency, and the mechanism of relapse in patients receiving stem cell rescue as therapy for malignant disease. Second-generation studies are beginning to provide even more information about a wider variety of clinical and biological issues. Although marker studies have been useful, it is becoming apparent that the indicator genes used up to now have a number of undesirable characteristics. Future applications of marking, in the hematopoietic system and elsewhere, will require the use of marker elements that will not produce any modification of the cells' behavior. Finally, marker studies have proved safe so far, but follow-up of the treated patients continues.

Gene transfer into hematopoietic stem cells of nonhuman primates

Nonhuman primates provide an appropriate preclinical large-animal model to test the efficacy of bone marrow gene therapy procedures. Successful retroviral vector-mediated gene transfer into monkey pluripotent hematopoietic stem cells (PHSC) has closed the gap between gene transfer experiments in mouse models and clinical application of bone marrow gene therapy. After initial bone marrow transplant failures, ex vivo bone marrow culture conditions were found that sufficiently supported maintenance of the long-term repopulating ability of genetically modified autologous monkey grafts. The efficiency of gene transfer into primate PHSC has, however, remained at least one order of magnitude lower than has been achieved in mice. Similar gene transfer efficiencies have been obtained with total bone marrow grafts, CD34+ bone marrow grafts, and mobilized peripheral blood progenitor cell grafts; however, various attempts to increase the transduction efficiency have been without significant success. Primate PHSC seem to require quite different culture conditions for their maintenance and transduction than mouse PHSC, in particular regarding hematopoietic growth factor addition. In contrast to observations in other species, some form of conditioning appeared essential for engraftment of transduced PHSC in monkeys. Although it has been shown that mouse retroviruses can replicate in monkeys and are capable of inducing neoplasms, experiments in monkeys have sufficiently confirmed the safety of current gene transfer procedures to allow their clinical application.

Inhibition of NF-kappaB/Rel induces apoptosis of murine B cells

Apoptosis of the WEHI 231 immature B cell lymphoma line following membrane interaction with an antibody against the surface IgM chains (anti-IgM) is preceded by dramatic changes in Nuclear Factor-kappaB (NF-kappaB)/ Rel binding activities. An early transient increase in NF-kappaB/Rel binding is followed by a significant decrease in intensity below basal levels. Here we have explored the role of these changes in Rel-related factors in B cell apoptosis. Treatment of WEH1 231 cells with N-tosyl-L-phenylalanine chloromethyl ketone (TPCK), a protease inhibitor which prevents degradation of the inhibitor of NF-kappaB (IkappaB)-alpha, or with low doses of pyrrolidinedithiocarbamate (PDTC) selectively inhibited NF-kappaB/Rel factor binding and induced apoptosis. Bcl-XL expression protected WEHI 231 cells from apoptosis induced by these agents. Microinjection of WEHI 231 cells with either IkappaB-alpha-GST protein or a c-Rel affinity-purified antibody induced apoptosis. Ectopic c-Rel expression ablated apoptosis induced by TPCK or anti-IgM. Treatment of BALENLM 17 and A20 B lymphoma cells or normal murine splenic B lymphocytes with either TPCK or PDTC also resulted in apoptosis. These findings indicate that the drop in NF-kappaB/Rel binding following anti-IgM treatment activates apoptosis of WEHI 231 cells; furthermore, they implicate the NF-kappaB/Rel family in control of apoptosis of normal and transformed B cells.