New insights into the role of nuclear factor-kappaB in cell growth regulation

The feasibility of monitoring NF-kappaB associated cytokines: TNF-alpha, IL-1alpha, IL-6, and IL-8 in whole saliva for the malignant transformation of oral lichen planus

Previous investigations have demonstrated that immune activation and chronic inflammation may be one of the causes of oncogenesis. A previous study from our lab has shown significant increases of NF-kappaB dependent cytokines, TNF-alpha, IL-1alpha, IL-6, and IL-8 in different oral fluids from oral lichen planus (OLP) patients. The aim of this analysis was to explore the potential of detecting these cytokines in whole unstimulated saliva (WUS) in monitoring the malignant transformation of OLP. Thirteen patients with OLP (with epithelial dysplasia), 13 cases with oral squamous cell carcinoma (OSCC), and 13 age-sex matched controls were enrolled in the study. The WUS samples were collected and the level of TNF-alpha, IL-1alpha, IL-6, and IL-8 in WUS was determined by ELISA. In moderate and severe dysplasia, the level of each cytokine was significantly higher than in control. In moderate dysplasia, TNF-alpha and IL-1alpha were significantly increased at a level without difference from OSCC, but IL-6 and IL-8 was detected at a concentration significantly lower than OSCC. In severe dysplasia, the level of TNF-alpha was also not significantly different from that of OSCC, and the level of IL-1alpha, IL-6, and IL-8 was still significantly lower than that of OSCC. The level of four cytokines between smokers and non-smokers in each group did not show a significant difference. These results indicate that the change of NF-kappaB dependent cytokines in WUS may in part reflect the malignant transformation of OLP and the analysis of these cytokines and may provide a useful, non-invasive surrogate endpoint for monitoring malignant transformation as well as the therapeutic response of OLP. This is the first in vivo study utilizing saliva to confirm preclinical data that NF-kappaB is upregulated in oral carcinogenesis.

Glucose-induced Akt1 activation mediates fibronectin synthesis in endothelial cells

AIMS/HYPOTHESIS

Increased expression and decreased degradation of extracellular matrix (ECM) proteins are key features of chronic diabetic complications. Fibronectin, a predominant ECM protein, has been shown to be overexpressed in all target organs of diabetic complications and in endothelial cells cultured in high levels of glucose. The present study was designed to elucidate the role of protein kinase B (Akt/PKB) in glucose-induced fibronectin mRNA expression and protein production in vascular endothelial cells.

METHODS

Human umbilical vein endothelial cells were cultured in the presence of high glucose to study Akt/PKB activation. The upstream and downstream mediators in the Akt/PKB pathway were also investigated using dominant negative transfections and specific inhibitors of signalling pathways. Cells were subjected to real time RT-PCR, western blotting, and confocal microscopy to assess Akt1/PKBalpha activation and fibronectin mRNA expression and protein production. To detect transcription factor activation, electrophoretic mobility shift assay was carried out.

RESULTS

Our data demonstrate that fibronectin mRNA expression and protein production that are induced by high glucose are mediated via activation of Akt/PKB, which is modulated by mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and protein kinase C. Glucose-induced fibronectin mRNA expression and protein production are also mediated by Akt1/PKBalpha-dependent activation of the transcription factors nuclear factor-kappaB and activating protein-1.

CONCLUSIONS/INTERPRETATION

Our study provides insight into the mechanical basis of glucose-induced increases in fibronectin mRNA expression and protein production. High levels of glucose may increase fibronectin mRNA expression and protein production by activating Akt/PKB.

Silibinin inhibits cell invasion through inactivation of both PI3K-Akt and MAPK signaling pathways

Silibinin, isolated from Silybum marianum, has been known for its hepatoprotective properties and recent studies have revealed its antiproliferative and apoptotic effects on several cancer cells. An inhibitory effect of silibinin on tumor invasion and matrix metalloproteinase-2 (MMP-2) and urokinasetype plasminogen activator (u-PA) activities in culture medium has been observed in our previous study and the impacts of silibinin on enzyme activities of MMPs, u-PA, mitogen-activated protein kinase (MAPK) and Akt in A549 cells were continued to explore in this study. Our results showed that silibinin exerted an inhibitory effect on the phosphorylation of Akt, as well as extracellular signal-regulated kinases 1 and 2 (ERK1/2), which are the members of the MAPK family involved in the up-regulation of MMPs or u-PA, while no effects on the activities of p38(MAPK) and stress-activated protein kinase/c-Jun N-terminal kinase were observed. A treatment with silibinin to A549 cells also led to a dose-dependent inhibition on the activation of NF-kappaB, c-Jun and c-Fos. Additionally, the treatment of inhibitors specific for MEK (U0126) or PI3K (LY294002) to A549 cells could result in a reduced expression of MMP-2 and u-PA concomitantly with a marked inhibition on cell invasion. These findings suggested that the inhibition on MMP-2 and u-PA expression by silibinin may be through a suppression on ERK1/2 or Akt phosphorylation, which in turn led to the reduced invasiness of the cancer cells.

Parthenolide and sulindac cooperate to mediate growth suppression and inhibit the nuclear factor-kappa B pathway in pancreatic carcinoma cells

Activation of the transcription factor nuclear factor-kappa B (NF-kappa B) has been implicated in pancreatic tumorigenesis. We evaluated the effect of a novel NF-kappa B inhibitor, parthenolide, a sesquiterpene lactone isolated from the herb feverfew, in three human pancreatic tumor cell lines (BxPC-3, PANC-1, and MIA PaCa-2). Parthenolide inhibited pancreatic cancer cell growth in a dose-dependent manner with substantial growth inhibition observed between 5 and 10 micromol/L parthenolide in all three cell lines. Parthenolide treatment also dose-dependently increased the amount of the NF-kappa B inhibitory protein, I kappa B-alpha, and decreased NF-kappa B DNA binding activity. We have previously shown that nonsteroidal anti-inflammatory drugs (NSAID) suppress the growth of pancreatic cancer cells. To determine whether inhibition of the NF-kappa B pathway by parthenolide could sensitize pancreatic cancer cells to NSAID inhibition, BxPC-3, PANC-1, and MIA PaCa-2 cells were treated with parthenolide and the NSAID sulindac, either alone or in combination. Treatment with the combination of parthenolide and sulindac inhibited cell growth synergistically in MIA PaCa-2 and BxPC-3 cells and additively in PANC-1 cells. In addition, treatment with the parthenolide/sulindac combination lowered the threshold for apoptosis. Increased levels of I kappa B-alpha protein were detected, especially in MIA PaCa-2 cells, after treatment with parthenolide and sulindac compared with each agent alone. Similarly, decreased NF-kappa B DNA binding and transcriptional activities were detected in cells treated with the combination compared with the single agents, demonstrating cooperative targeting of the NF-kappa B pathway. These data provide preclinical support for a combined chemotherapeutic approach with NF-kappa B inhibitors and NSAIDs for the treatment of pancreatic adenocarcinoma.

Effect of a small molecule inhibitor of nuclear factor-kappaB nuclear translocation in a murine model of arthritis and cultured human synovial cells

A small cell-permeable compound, dehydroxymethylepoxyquinomicin (DHMEQ), does not inhibit phosphorylation and degradation of IκB (inhibitor of nuclear factor-κB [NF-κB]) but selectively inhibits nuclear translocation of activated NF-κB. This study aimed to demonstrate the antiarthritic effect of this novel inhibitor of the NF-κB pathway in vivo in a murine arthritis model and in vitro in human synovial cells. Collagen-induced arthritis was induced in mice, and after onset of arthritis the mice were treated with DHMEQ (5 mg/kg body weight per day). Using fibroblast-like synoviocyte (FLS) cell lines established from patients with rheumatoid arthritis (RA), NF-κB activity was examined by electrophoretic mobility shift assays. The expression of molecules involved in RA pathogenesis was determined by RT-PCR, ELISA, and flow cytometry. The proliferative activity of the cells was estimated with tritiated thymidine incorporation. After 14 days of treatment with DHMEQ, mice with collagen-induced arthritis exhibited decreased severity of arthritis, based on the degree of paw swelling, the number of swollen joints, and radiographic and histopathologic scores, compared with the control mice treated with vehicle alone. In RA FLS stimulated with tumor necrosis factor-α, activities of NF-κB components p65 and p50 were inhibited by DHMEQ, leading to suppressed expression of the key inflammatory cytokine IL-6, CC chemokine ligand-2 and -5, matrix metalloproteinase-3, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1. The proliferative activity of the cells was also suppressed. This is the first demonstration of an inhibitor of NF-κB nuclear translocation exhibiting a therapeutic effect on established murine arthritis, and suppression of inflammatory mediators in FLS was thought to be among the mechanisms underlying such an effect.

Inhibition of Cellular Proliferation and Induction of Apoptosis by Curcumin in Human Malignant Astrocytoma Cell Lines

Nuclear factor (NF)-kappaB is known to control cellular proliferation and apoptosis. In malignant astrocytoma cells, it was reported that NF-kappaB was activated aberrantly and promoted their proliferation. Thus, inhibition of NF-kappaB activity is considered to be a promising therapeutic strategy for malignant astrocytoma. Recently, curcumin, the major constituent of turmeric, was reported to inhibit NF-kappaB activity. In this study, we investigated inhibitory effects of curcumin on NF-kappaB activity and cellular proliferation, and induction of apoptosis by curcumin in human malignant astrocytoma cell lines. Alteration of NF-kappaB activity in NP-2 human malignant astrocytoma cell line after treatment with curcumin was examined using electrophoretic mobility shift assay. Alterations of DNA synthesis and cellular growth in five human malignant astrocytoma cell lines after treatment with curcumin were examined using [(3)H]thymidine incorporation assay and the trypan blue dye exclusion method, respectively. Induction of apoptosis by curcumin in NP-2 and NP-3 human malignant astrocytoma cell lines was examined by DNA-fragmentation analysis and morphological observation. We found that the NF-kappaB activity in NP-2 was significantly reduced by curcumin. The DNA synthesis and the cellular growth were inhibited by curcumin in dose-dependent manner in all the five malignant astrocytoma cell lines. Nuclear condensation and fragmentation, and DNA fragmentation were observed in both NP-2 and NP-3 after the treatment with curcumin. These results indicate that curcumin inhibits the cellular proliferation and induces apoptosis in human malignant astrocytoma cell lines. These results are considered to be resulted from the inhibition of NF-kappaB activity by curcumin.

Retinoid-induced activation of NF-κB in APL cells is not essential for granulocytic differentiation, but prolongs the life span of mature cells

All-trans retinoic acid (ATRA) significantly improves the survival of patients with acute promyelocytic leukemia (APL) by inducing granulocytic differentiation of leukemia cells. Since an activation of the transcription factor NF-kappaB occurs during ATRA-induced maturation of APL cells, a mechanistic link between these two processes was investigated. Using an in vitro model for APL, we report that ectopic overexpression of a repressor of NF-kappaB activation did not affect granulocytic differentiation. Importantly, NF-kappaB inhibition markedly resulted in a decreased viability of the differentiated cells, which correlated with increased apoptosis. Apoptosis was accompanied by a sustained activation of the c-Jun N-terminal kinase (JNK). Inhibition of JNK by the specific inhibitor SP600125 or by transfection of a dominant-negative mutant of JNK1 reduced the percentage of apoptotic cells, thus showing that JNK activation constitutes a death signal. Furthermore, impairment of NF-kappaB activation resulted in increased levels of reactive oxygen species (ROS) upon ATRA treatment. ROS accumulation was suppressed by the antioxidant butylated hydroxyanisol, which also abolished ATRA-induced JNK activation and apoptosis. Altogether, our results demonstrate an anti-apoptotic effect of NF-kappaB activation during ATRA-induced differentiation of NB4 cells and identify repression of ROS-mediated JNK activation as a mechanism for this effect. Our observations also suggest that NF-kappaB signalling may contribute to an accumulation of mature APL cells and participate in the development of ATRA syndrome.

Therapeutic effect of topical administration of SN50, an inhibitor of nuclear factor-kappaB, in treatment of corneal alkali burns in mice

We evaluated the therapeutic efficacy of topical administration of SN50, an inhibitor of nuclear factor-kappaB, in a corneal alkali burn model in mice. An alkali burn was produced with 1 N NaOH in the cornea of C57BL/6 mice under general anesthesia. SN50 (10 microg/microl) or vehicle was topically administered daily for up to 12 days. The eyes were processed for histological or immunohistochemical examination after bromodeoxyuridine labeling or for semi-quantification of cytokine mRNA. Topical SN50 suppressed nuclear factor-kappaB activation in local cells and reduced the incidence of epithelial defects/ulceration in healing corneas. Myofibroblast generation, macrophage invasion, activity of matrix metalloproteinases, basement membrane destruction, and expression of cytokines were all decreased in treated corneas compared with controls. To elucidate the role of tumor necrosis factor (TNF)-alpha in epithelial cell proliferation, we performed organ culture of mouse eyes with TNF-alpha, SN50, or an inhibitor of c-Jun N-terminal kinase (JNK) and examined cell proliferation in healing corneal epithelium in TNF-alpha-/- mice treated with SN50. An acceleration of epithelial cell proliferation by SN50 treatment was found to depend on TNF-alpha/JNK signaling. In conclusion, topical application of SN50 is effective in treating corneal alkali burns in mice.

Relative Ability of Dietary Compounds to Modulate Nuclear Factor-κB Activity as Assessed in a Cell-Based Reporter System

The ability of various dietary compounds to modulate the activity of the transcription factor nuclear factor kappaB (NF-kappaB) was examined using a cell-based reporter system. NF-kappaB is central to the response of cells to stress and has been linked to cancer. HCT 116 (human colon carcinoma) and HepG2 (human liver carcinoma) cell lines were stably transfected with a NF-kappaB luciferase reporter vector. The reporter cell lines were preincubated with different concentrations (0-50 microM) of ascorbic acid, epigallocatechin gallate, genistein, quercetin, naringenin, and resveratrol for varying periods of times (1-12 hours), after which the NF-kappaB inducer tumor necrosis factor-alpha (TNF-alpha) was added (4-8 ng/mL) for 4 hours. Compound alone, without TNF-alpha, did not alter luciferase activity. Levels of TNF-alpha-induced luciferase (NF-kappaB) activity varied depending on compound type and concentration, whereas preincubation time and cell type contributed less. Significant changes in luciferase (NF-kappaB) activity were detected for some of the compounds at more physiological concentrations (1-10 microM). Our data suggest that dietary modulation of NF-kappaB activity involves distinct mechanisms, depending on compound type and concentration. More generally, this approach can be utilized for analyzing dietary compounds for effects on specific cellular factors over a range of concentrations and incubation times, in combination, and in different cell types.

Is NF-κB a culprit in type 2 diabetes?

It has been generally viewed that salicylates ameliorate type 2 diabetes through interfering with the NF-kappaB signaling. Earlier studies indicated that IKKbeta was the key for the development of insulin resistance. However, it was unknown whether IKKbeta itself, or its downstream target, NF-kappaB, plays major roles in insulin resistance. New data suggest that NF-kappaB and NF-kappaB-regulated cytokines are crucial for the diabetogenesis.

Downregulation of NF-kappaB activity associated with alteration in proliferative response in the spleen after burn injury

Alterations in proliferation status and cellular composition of immune organs are among key events in the modulation of immune function after burn injury. Nuclear factor (NF)-kappaB is a transcription factor that plays a pivotal role in the response to injury as well as immune cell differentiation and proliferation. In this study, we investigated the effects of burn injury on the activity of NF-kappaB and its association with cellular proliferation in the spleen. Western analysis of whole spleen tissues of mice after 18% burn injury revealed a marked reduction in nuclear NF-kappaB rel A protein expression 3 to 21 days after injury when there was an increase in proliferative activity in the red pulp of the spleen after injury as indicated by an increase in proliferating cell nuclear antigen (PCNA). In the splenic B cells, however, the down-regulation of NF-kappaB rel A was associated with decreased PCNA expression as well as IkappaBalpha and phosphorylated IkappaBalpha. In contrast, no significant change in NF-kappaB rel A or PCNA expression was observed for splenic T cells. These data suggest that there is a differential regulation of NF-kappaB and proliferative activity in the splenic cell subsets after burn injury. Furthermore, the regulation of NF-kappaB may be linked to the proliferative changes seen in the spleen after burn injury.

Diabetes-induced fetal growth retardation is associated with suppression of NF-kappaB activity in embryos

BACKGROUND

Mechanisms underlying diabetes-induced fetal growth retardation remain largely undefined. Two events such as the persistent activation of apoptosis or suppression of cell proliferation in embryos might directly result in fetal growth retardation. Evidence implicating the transcription factor NF-kappaB in the regulation of the physiological and teratogen-induced apoptosis as well as cell proliferation suggests that it may be a component of mechanisms underlying this pathology. To address this issue, this study was designed to test: 1) whether diabetes-induced fetal growth retardation is preceded by the modulation of NF-kappaB activity in embryos at the late stage of organogenesis and 2) whether apoptosis is altered in these embryos.

METHODS

The embryos and placentas of streptozotocin-induced diabetic mice collected on days 13 and 15 of pregnancy were used to evaluate the expression of NF-kappaB, IkappaBalpha and phosphorylated (p)-IkappaBalpha proteins by Western blot analysis and NF-kappaB DNA binding by an ELISA-based method. The detection of apoptotic cells was performed by the TUNEL assay and the expression of a proapoptotic protein Bax was evaluated by the Western blot.

RESULTS

The embryos of diabetic mice were significantly growth retarded, whereas the placental weight did not differ in diabetic or control females. Levels of NF-kappaB and p-IkappaBalpha proteins as well as the amount of NF-kappaB DNA binding was lower in embryos of diabetic mice as compared to those in controls. However, neither excessive apoptosis nor an increased Bax expression was found in growth-retarded embryos and their placentas.

CONCLUSION

The study herein revealed that diabetes-induced fetal growth retardation is associated with the suppression of NF-kappaB activity in embryos, which seems to be realized at the level of IkappaB degradation.

Expression of tumor necrosis factor alpha, TNF-related apoptosis-inducing ligand, and their associated molecules in ameloblastomas

BACKGROUND

To clarify the roles of the apoptosis signaling pathway mediated by death receptors in oncogenesis and cytodifferentiation of odontogenic tumors, expression of tumor necrosis factor alpha (TNFalpha), TNF-related apoptosis-inducing ligand (TRAIL), and their associated molecules was analyzed in ameloblastomas as well as in tooth germs.

METHODS

Tissue specimens of 10 tooth germs, 40 benign ameloblastomas, and five malignant ameloblastomas were examined by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry to determine the expression of TNFalpha, TNF receptor I (TNFRI), TRAIL, TRAIL receptor 1 (TRAIL-R1), TRAIL-R2, caspase-8, and nuclear factor-kappaB (NF-kappaB).

RESULTS

Expression of TNFalpha, TNFRI, TRAIL, TRAIL-R1, TRAIL-R2, and NF-kappaB mRNA was detected in most samples of normal and neoplastic odontogenic tissues. Expression of caspase-8 mRNA was identified in six of 33 ameloblastomas, but not in 10 tooth germs or one malignant ameloblastoma. Immunohistochemical reactivity for TNFalpha, TRAIL, their receptors, and NF-kappaB was detected in both normal and neoplastic odontogenic tissues. Epithelial expression of TNFalpha was focal in about 50% of tooth germs and ameloblastomas, and TNFalpha expression in neoplastic cells was significantly higher in follicular ameloblastomas than in plexiform ameloblastomas. TRAIL reactivity was evident in epithelial cells neighboring the basement membrane. Receptors for TNFalpha and TRAIL were diffusely expressed in both normal and neoplastic odontogenic epithelium. Expression of caspase-8 was found in some neoplastic cells in three of 37 ameloblastomas, but not in 10 tooth germs or five malignant ameloblastomas. Nuclear NF-kappaB expression was much lower than cytoplasmic expression in both normal and neoplastic odontogenic epithelium.

CONCLUSION

Expression of TNFalpha, TRAIL, and their receptors in tooth germs and ameloblastomas suggests that these death factors might be involved in cytodifferentiation of odontogenic epithelium and tissue structuring of ameloblastomas. Expression of caspase-8 and NF-kappaB suggests that signaling of TNFalpha and TRAIL minimally affects the biological properties of odontogenic epithelial components.

Signal transducer and activator of transcription 3alpha and specificity protein 1 interact to upregulate intercellular adhesion molecule-1 in ischemic-reperfused myocardium and vascular endothelium

OBJECTIVE

Intercellular adhesion molecule-1 (ICAM-1) is upregulated rapidly on endothelial cells during ischemia-reperfusion (I-R) and mediates tissue leukocyte accumulation. The ICAM-1 proximal promoter contains a signal transducer and activator of transcription (Stat) binding motif (gamma-interferon activation site [GAS] sequence), which flanks a specificity protein 1 (Sp1) binding site. We examined the roles of Stat and Sp1 in the regulation of ICAM-1 after myocardial I-R.

METHODS AND RESULTS

Open-chest anesthetized rats underwent coronary artery occlusion for 35 minutes and reperfusion for 0 to 240 minutes. Stat became activated within 15 minutes after reperfusion, primarily in vascular endothelial cells; the activated Stat protein was identified as Stat3 (alpha-isoform). After phosphorylation on serine 727 (p-S727), Stat3alpha was found in association with the transcriptional regulator Sp1, and the complex bound to an ICAM-1-GAS probe. ICAM-1 expression increased after I-R and lagged shortly behind Stat3alpha activation. In cultured human umbilical vein endothelial (HUVE) cells, activation of Stat3alpha after hypoxia-reoxygenation (H-R) was dependent on the small GTPase Rac1. Transfection of a dominant-negative Stat3 (Y705F) adenovirus or a GAS decoy oligonucleotide reduced ICAM-1 mRNA expression after H-R. Using a reporter gene transfected into HUVE cells, mutation of the GAS element in the ICAM-1 promoter resulted in reduced transcriptional activity after H-R. Sp1 coimmunoprecipitated with p-S727 Stat3 during H-R, and Sp1 or Stat3alpha interfering RNA markedly reduced ICAM-1 mRNA expression.

CONCLUSIONS

The Sp1-Stat3 complex appears to play an important role in the upregulation of ICAM-1 transcription after reoxygenation or reperfusion.

NF-kB in development and progression of human cancer

The nuclear factor kB (NF-kB) comprises a family of transcription factors involved in the regulation of a wide variety of biological responses. NF-kB plays a well-known function in the regulation of immune responses and inflammation, but growing evidences support a major role in oncogenesis. NF-kB regulates the expression of genes involved in many processes that play a key role in the development and progression of cancer such as proliferation, migration and apoptosis. Aberrant or constitutive NF-kB activation has been detected in many human malignancies. In recent years, numerous studies have focused on elucidating the functional consequences of NF-kB activation as well as its signaling mechanisms. NF-kB has turned out to be an interesting therapeutic target for treatment of cancer.

Rel/Nuclear factor-kappa B apoptosis pathways in human cervical cancer cells

Cervical cancer is considered a common yet preventable cause of death in women. It has been estimated that about 420 women out of the 1400 women diagnosed with cervical cancer will die during 5 years from diagnosis. This review addresses the pathogenesis of cervical cancer in humans with a special emphasis on the human papilloma virus as a predominant cause of cervical cancer in humans. The current understanding of apoptosis and regulators of apoptosis as well as their implication in carcinogenesis will follow. A special focus will be given to the role of Rel/NF-kappaB family of genes in the growth and chemotherapeutic treatment of the malignant HeLa cervical cells emphasizing on Xrel3, a cRel homologue.

A comparison of the pro-inflammatory, NF-kappaB-dependent cytokines: TNF-alpha, IL-1-alpha, IL-6, and IL-8 in different oral fluids from oral lichen planus patients

To explore the feasibility of detection of the level of NF-kappaB-dependent cytokines in oral fluids from patient with oral lichen planus (OLP) for clinical application, 13 OLP subjects were enrolled in the study as were 13 age-sex-matched controls. In each subject, the whole unstimulated saliva (WUS), mixture of saliva and isotonic saline oral rinse (Saliva-NaCl), and lesion tissue transudates (TT) were collected by standard techniques. The level of cytokines, TNF-alpha, IL-1-alpha, IL-6, and IL-8 in three types of oral fluids was determined by ELISA. In the three types of oral fluids, a significantly higher level of these cytokines was detected in OLP patients than in normal controls. These results indicate that NF-kappaB-dependent inflammatory cytokines may be detected at increased levels in certain oral fluids which may have diagnostic and prognostic potential for monitoring disease activity and making therapeutic decisions in patients with OLP.

Nuclear factor-kappaB/p65 (Rel A) is constitutively activated in human prostate adenocarcinoma and correlates with disease progression

Aberrant nuclear factor-kappaB (NF-kappaB) activation has been implicated in the pathogenesis of several human malignancies. In this study, we determined whether NF-kappaB is constitutively activated in human prostate adenocarcinoma, and, if so, whether increased NF-kappaB activation and its binding to DNA influence tumor progression. Using tissue samples obtained during transurethral prostatic resection and paraffin-embedded sections of benign and cancer specimens, we determined the nuclear expression of NF-kappaB/p65 and NF-kappaB/p50, cytoplasmic expression of IkappaBalpha, its phosphorylation, and expression of NF-kappaB-regulated genes, specifically Bcl2, cyclin D1, matrix metalloproteinase-9 (MMP-9), and vascular endothelial growth factor (VEGF). A progressive increase in the expression of NF-kappaB/p65 (but not of p50) was observed in cancer specimens compared to benign tissue, which correlated with increasing levels of IkappaBalpha and its phosphorylation. NF-kappaB DNA-binding activity increased with increasing tumor grade and the binding complex mainly consisted of NF-kappaB/p65-p50 heterodimers. Immunohistochemical analysis showed enhanced nuclear staining for NF-kappaB/p65 in both high-grade (P <.0001) and low-grade (P <.003) cancer specimens, compared to benign tissue. The nuclear levels of NF-kappaB/p65 correlated with concurrent increase in cytosolic levels of IkappaBalpha along with NF-kappaB-dependent expression of Bcl2, cyclin D1, MMP-9, and VEGF. These results demonstrate that NF-kappaB/p65 is constitutively activated in human prostate adenocarcinoma and is related to tumor progression due to transcriptional regulation of NF-kappaB-responsive genes.

Quantitative Chemiluminescent Immunoassay for NF‐κB–DNA Binding Activity

Nuclear factor-kappaB (NF-kappaB) is a ubiquitous redox-sensitive transcription factor involved in the pro-inflammatory response to several factors, including cytokines and oxidative stress. Upon activation, NF-kappaB translocates into the nucleus and binds to specific nucleotide sequences. The cellular responses to inflammatory and stress signals have been implicated in disease conditions, such as atherosclerosis, cancer, diabetes, and Alzheimer's disease. The conventional method for detection of NF-kappaB -DNA binding activity is the electrophoretic mobility shift assay (EMSA), which is time-consuming and non-quantitative. Here, we report (a) development of a rapid, sensitive and quantitative chemiluminescent immunoassay (QCI) for analysis of NF-kappaB DNA-binding activity, and (b) validation of the QCI with the EMSA using nuclear and cytosolic extracts from cultured prostate cancer cells (PC3), rat liver homogenates and human lymphocytes. The QCI for analysis of NF-kappaB DNA binding activity has advantages over the EMSA: (1) Higher speed: 3-5h post sample preparation, (2) Greater sensitivity: 10pg NF-kappaB/well, (3) Quantitative: linear range: 10-1000pg NF-kappaB; r2 = 0.999 (4) High throughput adaptability: 96-well plate format can analyze up to 40 samples in duplicate, (5) SAFETY: No radioactive isotopes, (6) Simplicity, and (7) Capability of measurement of both activated (free) NF-KB which is translocated into the nucleus and total (bound + unbound) NF-kappaB present in the cytosol/cell.

DNA binding of repressor nuclear factor-kappaB p50/p50 depends on phosphorylation of Ser337 by the protein kinase A catalytic subunit

The NF-kappaB p50/p50 homodimer is mainly associated with transcriptional repression. Previously, we demonstrated that phosphorylation of NF-kappaB p50 Ser(337) is critical for DNA binding. Here, we report that p50 Ser(337) is constitutively phosphorylated by the protein kinase A catalytic subunit (PKAc) in three different cell types, which may account for the constant binding of p50/p50 to DNA in unstimulated cells. This was demonstrated first by showing that treatment of cells with PKAc-specific inhibitors blocked p50/p50 DNA binding. Second, phosphorylation of p50 by PKAc was prevented by substitution of Ser(337) to alanine. Third, both p50 and PKAc proteins as well as kinase activity that phosphorylates p50 were found to co-fractionate following gel filtration chromatography. Finally, PKAc and p50 were shown to be able to reciprocally co-immunoprecipitate one another, and their physical association was blocked by a PKA catalytic site inhibitory peptide. This indicates that phosphorylation of p50 Ser(337) involves direct contact with the PKAc catalytic center. In contrast to the dramatic elevation of nuclear p50/p65 heterodimers induced by tumor necrosis factor alpha, DNA binding of p50/p50 homodimers was not greatly altered. Taken together, these findings reveal for the first time that there is a direct interaction between PKAc and p50 that accounts for constitutive phosphorylation of p50 Ser(337) and the existence of DNA bound p50/p50 in the nuclei of most resting cells. This mechanism of DNA binding by p50/p50 following phosphorylation of Ser(337) by PKAc may represent an important means for maintaining stable negative regulation of NF-kappaB gene expression in the absence of extracellular stimulation.

Quinic acid is a biologically active component of the Uncaria tomentosa extract C-Med 100®

We have previously reported that the C-Med 100 extract of the plant Uncaria tomentosa induces prolonged lymphocyte half life and hence increased spleen cell number in mice receiving the extract in their drinking water. Further, the extract induces cell proliferation arrest and inhibits activation of the transcriptional regulator nuclear factor kappaB (NF-kappaB) in vitro. We now report that mice exposed to quinic acid (QA), a component of this extract, had significantly increased number of spleen cells, thus recapitulating the in vivo biological effect of C-Med 100 exposure. Commercially supplied QA (H(+) form) did not, however, inhibit cell proliferation in vitro, while the ammonia-treated QA (QAA) was a potent inhibitor. Both QA and QAA inhibited NF-kappaB activity in exposed cells at similar concentrations. Thus, our present data identify QA as a candidate component for both in vivo and in vitro biological effects of the C-Med 100 extract.

Signal pathways underlying homocysteine-induced production of MCP-1 and IL-8 in cultured human whole blood

AIM

To elucidate the mechanisms underlying homocysteine (Hcy)-induced chemokine production.

METHODS

Human whole blood was pretreated with inhibitors of calmodulin (CaM), protein kinase C (PKC), protein tyrosine kinase (PTK), mitogen-activated protein kinase (MAPK), and NF-kappaB and activators of PPARgamma for 60 min followed by incubation with Hcy 100 micromol/L for 32 h. The levels of mitogen chemokine protein (MCP)-1 and interleukin-8 (IL-8) were determined by enzyme-linked immunosorbant assay (ELISA).

RESULTS

Inhibitors of PKC (calphostin C, 50-500 nmol/L and RO-31-8220, 10-100 nmol/L), CaM (W7, 28-280 micromol/L), ERK1/2 MAPK (PD 98059, 2-20 micromol/L), p38 MAPK (SB 203580, 0.6-6 micromol/L), JNK MAPK (curcumin, 2-10 micromol/L), and NF-kappaB (PDTC, 10-100 nmol/L) markedly reduced Hcy 100 micromol/L-induced production of MCP-1 and IL-8 in human cultured whole blood, but the inhibitors of PTK (genistein, 2.6-26 micromol/L and tyrphostin, 0.5-5 micromol/L) had no obvious effect on MCP-1 and IL-8 production. PPARgamma activators (ciglitazone 30 micromol/L and troglitazone 10 micromol/L) depressed the Hcy-induced MCP-1 production but not IL-8 production in the cultured whole blood.

CONCLUSION

Hcy-induced MCP-1 and IL-8 production is mediated by activated signaling pathways such as PKC, CaM, MAPK, and NF-kappaB. Our results not only provide clues for the signal transduction pathways mediating Hcy-induced chemokine production, but also offer a plausible explanation for a pathogenic role of hyperhomocysteinemia in these diseases.

Desloratadine Inhibits Constitutive and Histamine-Stimulated Nuclear Factor-κB Activity Consistent with Inverse Agonism at the Histamine H1 Receptor

BACKGROUND

The human histamine H1 receptor is constitutively active and exhibits basal activation of nuclear factor-kappaB (NF-kappaB), an important modulator of allergic inflammation. Certain H1 antihistamines have recently been shown to inhibit basal NF-kappaB activity by stabilizing the H1 receptor in an inactive state, a phenomenon called 'inverse agonism'.

METHODS

We evaluated the effect of the new H1 antihistamine, desloratadine, on basal and histamine-stimulated NF-kappaB activity and compared it with the activities of other H1 antihistamines.

RESULTS

Transiently transfected COS-7 cells co-expressing NF-kappaB-luciferase and the H1 receptor exhibited constitutive NF-kappaB activity. H1 antihistamines reduced basal NF-kappaB activity (rank order of potency: desloratadine > pyrilamine > cetirizine > loratadine > fexofenadine). Histamine stimulated basal NF-kappaB activity 8-fold, which was blocked by H1 antihistamines (rank order of potency: desloratadine > cetirizine > pyrilamine > loratadine > fexofenadine). Neither histamine nor antihistamines had any effect on NF-kappaB activity in the absence of the H1 receptor.

CONCLUSIONS

Desloratadine, acting through the histamine H1 receptor, inhibited basal NF-kappaB activity and can thus be classified as an inverse agonist. Inhibition of basal and histamine-stimulated NF-kappaB activity may help to explain previously reported inhibitory effects of desloratadine on allergic inflammatory mediators.

Metal-induced oxidative stress and signal transduction

Occupational and environmental exposures to metals are associated with the development of various cancers. Although carcinogenesis caused by metals has been intensively investigated, the mechanisms of action, especially at the molecular level, are still unclear. Accumulating evidence indicates that reactive oxygen species generated by metals may play an important role in the etiology of disease. This review covers recent advances in (1) metal-induced generation of reactive oxygen species; (2) the receptors, kinases, and nuclear transcription factors affected by metals and metal-induced oxidative stress, including growth factor receptors, src kinase, ras signaling, mitogen-activated protein kinases, the phosphoinositide 3-phosphate/Akt pathway, nuclear transcription factor kappaB, activator protein 1, p53, nuclear factor of activated T cells, and hypoxia-inducible factor 1; and (3) global cellular phenomena (signal transduction, cell cycle regulation, and apoptosis) associated with metal-induced ROS production and gene expression.

Molecular basis of chemoprevention by resveratrol: NF-kappaB and AP-1 as potential targets

Recently, chemoprevention by the use of naturally occurring substances is considered as a priority to reduce the ever-increasing incidence of cancer. The intervention of multistage carcinogenesis by modulating intracellular signaling pathways may provide molecular basis of chemoprevention with a wide variety of dietary phytochemicals. Resveratrol, a red wine polyphenol, has been studied extensively for the chemopreventive activity in the context of its ability to interfere with the multistage carcinogenesis. Numerous intracellular signaling cascades converge with the activation of nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1), which act independently or coordinately to regulate expression of target genes. These ubiquitous eukaryotic transcription factors mediate pleiotropic effects on cellular transformation and tumor promotion. This review aims to update the molecular mechanisms underlying chemoprevention by resveratrol with special focus on its effect on cellular signaling cascades mediated by NF-kappaB and AP-1.

Control of Atm-/- thymic lymphoma cell proliferation in vitro and in vivo by dexamethasone

AIM

Ataxia telangiectasia (A-T) is an autosomal recessive disease in humans caused by mutations in the Atm (A-T mutated) gene. The disease involves multiple organ systems, and is associated with a high incidence of leukemias and lymphomas that develop in childhood. We have reported previously that thymic lymphoma development in Atm knockout (Atm-/-) mice is associated with elevated spontaneous DNA synthesis in thymocytes, and that dexamethasone (Dex) attenuates the elevated DNA synthesis and prevents thymic lymphoma development. The primary objectives of the present study were (1) to investigate possible mechanisms underlying the tumor-suppressing effect of Dex on Atm-/- thymic lymphoma cells, and (2) to determine whether Dex is an effective tumor-suppressing treatment in mice bearing transplanted Atm-/- thymic tumors.

METHODS

Establishment of a number of Atm-/- thymic lymphoma (ATL) cell lines from Atm-/- mice, cell proliferation assays, cell cycle analyses, Western blotting and Hoechst nuclear staining were used to analyze the effects of Dex on Atm-/- thymic lymphoma cells. Atm-/- tumor cells were transplanted into the right flanks of Atm+/+ mice prior to the initiation of Dex treatment.

RESULTS

Atm-/- tumor cells were highly sensitive to Dex, both in culture and in vivo as ectopic tumors in mice. In cultured ATL-1 cells, Dex induced apoptosis, arrested the cell cycle at the G1 phase and downregulated NF-kappaB and multiple cell cycle regulators, while upregulating the NF-kappaB inhibitor IkappaBalpha. In Atm+/+ mice transplanted subcutaneously with ATL-1 cells, tumor growth was either prevented completely or significantly suppressed by Dex treatment.

CONCLUSIONS

Our findings identify potential mechanisms by which Dex affects the proliferation and survival of ATL-1 cells in culture, and provide evidence that Dex can suppress the proliferation of Atm-/- thymic lymphoma cells growing in the body. Together these results add to our earlier published data suggesting that the cellular pathways regulated by Dex may be promising therapeutic targets for prevention and treatment of thymic lymphomas in A-T individuals.

Identification of target genes involved in the antiproliferative effect of glucocorticoids reveals a role for nuclear factor-(kappa)B repression

Glucocorticoid hormones (GCs) exert an antiproliferative effect on most cells. However, the molecular mechanism is still largely unclear. We investigated the antiproliferative mechanism by GCs in human embryonic kidney 293 cells with stably introduced glucocorticoid receptor (GR) mutants that discriminate between cross-talk with nuclear factor-(kappa)B (NF-(kappa)B) and activator protein-1 signaling, transactivation and transrepression, and antiproliferative vs. non-antiproliferative responses. Using the GR mutants, we here demonstrate a correlation between repression of NF-(kappa)B signaling and antiproliferative response. Gene expression profiling of endogenous genes in cells containing mutant GRs identified a limited number of genes that correlated with the antiproliferative response. This included a GC-mediated up-regulation of the NF-(kappa)B-inhibitory protein I(kappa)B(alpha), in line with repression of NF-(kappa)B signaling being important in the GC-mediated antiproliferative response. Interestingly, the GC-stimulated expression of I(kappa)B(alpha) was a direct effect despite the inability of the GR mutant to transactivate through a GC-responsive element. Selective expression of I(kappa)B(alpha) in human embryonic kidney 293 cells resulted in a decreased percentage of cells in the S/G2/M phase and impaired cell proliferation. These results demonstrate that GC-mediated inhibition of NF-(kappa)B is an important mechanism in the antiproliferative response to GCs.

Improving the selectivity of cancer treatments by interfering with cell response pathways

The cellular response to the stress induced by treatment with anticancer agents is a key determinant of drug activity. A pivotal role in this response is played by checkpoint proteins that control the normal passage of cells through the cell cycle. There is evidence that cancer cells often have defects in one checkpoint control that makes them more vulnerable to inhibition of a second checkpoint, thereby enhancing the overall response to treatment. The G1 and G2 checkpoints are particularly crucial for the decision of a cell to arrest in the cell cycle after damage. The checkpoints are used to try to allow the repair of any damage, or to activate the apoptotic (programmed cell death) machinery. Inhibition of both G1 and G2 checkpoints in cancer cells is therefore likely to result in an induction of the death response in cancer cells. Similarly, an increasing knowledge of the molecular mechanisms that form the basis of apoptotic pathways has helped to define why cancer cells have a reduced propensity to undergo apoptosis following the activation of apoptotic inhibitory pathways or the inhibition of pro-apoptotic pathways. Therefore, the possibility to modulate these pathways is likely to result not only in the increased activity of anticancer agents, but also in an increase in their specificity.

Interleukin 1beta enhances invasive ability of gastric carcinoma through nuclear factor-kappaB activation

PURPOSE

We examined the role of interleukin (IL)-1beta in activation of nuclear factor kappaB (NF-kappaB) and the biological function of activated NF-kappaB in gastric carcinoma cells.

EXPERIMENTAL DESIGN

Human gastric carcinoma cell line GCTM-1 was used to examine NF-kappaB activation by immunostaining and electrophoretic mobility shift assay. Matrix metalloproteinase (MMP)-9 expression, which plays an important role in tumor invasion, was assessed by semiquantitative reverse transcription-PCR, Western blotting, and immunostaining. The invasive ability of GCTM-1 cells was measured by Matrigel invasion assay. In vivo expression of IL-1beta and MMP-9 and activation of NF-kappaB in 10 surgically resected gastric carcinoma specimens were examined immunohistochemically.

RESULTS

IL-1beta enhanced NF-kappaB activation, MMP-9 expression, and the invasive ability of GCTM-1. A NF-kappaB inhibitor, pyrrolidine dithiocarbamate, suppressed both MMP-9 expression and invasiveness of IL-1beta-treated GCTM-1 cells. IL-1beta did not increase the invasive ability of GCTM-1 cells transfected with MMP-9 antisense oligonucleotide. Concomitant expression of IL-1beta and nuclear NF-kappaB was observed in 3 of 10 gastric carcinoma specimens. Cells producing IL-1beta were tumor-infiltrating macrophages in two specimens and gastric carcinoma cells in one specimen.

CONCLUSIONS

One of the molecules that may play a role in NF-kappaB activation in some gastric carcinomas is IL-1beta. The present results suggest that IL-1beta increases the invasive ability of carcinoma cells through activation of NF-kappaB and the resulting MMP-9 expression.

Herpesvirus ateles Tio can replace herpesvirus saimiri StpC and Tip oncoproteins in growth transformation of monkey and human T cells

Herpesvirus saimiri group C strains are capable of transforming human and simian T-lymphocyte populations to permanent antigen-independent growth. Two viral oncoproteins, StpC and Tip, that are encoded by a single bicistronic mRNA, act in concert to mediate this phenotype. A closely related New World monkey herpesvirus, herpesvirus ateles, transcribes a single spliced mRNA at an equivalent genome locus. The encoded protein, Tio, has sequence homologies to both StpC and Tip. We inserted the tio sequence of herpesvirus ateles strain 73 into a recombinant herpesvirus saimiri C488 lacking its own stpC/tip oncogene. Simian as well as human T lymphocytes were growth transformed by the chimeric Tio-expressing viruses. Thus, a single herpesvirus protein appears to be responsible for the oncogenic effects of herpesvirus ateles.

Signal transduction pathways regulating cyclooxygenase-2 expression: potential molecular targets for chemoprevention

Expression of cyclooxygenase-2 (COX-2) has been reported to be elevated in human colorectal adenocarcinoma and other tumors, including those of breast, cervical, prostate, and lung. Genetic knock-out or pharmacological inhibition of COX-2 has been shown to protect against experimentally-induced carcinogenesis. Results from epidemiological and laboratory studies indicate that regular intake of selective COX-2 inhibitors reduces the risk of several forms of human malignancies. Thus, it is conceivable that targeted inhibition of abnormally or improperly elevated COX-2 provides one of the most effective and promising strategies for cancer chemoprevention. The COX-2 promoter contains a TATA box and binding sites for several transcription factors including nuclear factor-kappaB (NF-kappaB), nuclear factor for interleukin-6/CCAAT enhancer-binding protein (NF-IL6/C/EBP) and cyclic AMP response element (CRE) binding protein. Upregulation of COX-2 is mediated by a variety of stimuli including tumor promoters, oncogenes, and growth factors. Stimulation of either protein kinase C (PKC) or Ras signaling enhances mitogen-activated protein kinase (MAPK) activity, which, in turn, activates transcription of cox-2. Celecoxib, the first US FDA approved selective COX-2 inhibitor, initially developed for the treatment of adult rheumatoid arthritis and osteoarthritis, has been reported to reduce the formation of polyps in patients with familial adenomatous polyposis. This COX-2 specific inhibitor also protects against experimentally-induced carcinogenesis, but the underlying molecular mechanisms are poorly understood. The present review covers the signal transduction pathways responsible for regulating COX-2 expression as novel molecular targets of chemopreventive agents with celecoxib as a specific example.

Signal transduction pathways relevant for neoplastic effects of fibrous and non-fibrous particles

Apart from their genotoxic effects, both fibrous and non-fibrous particles are known to induce signalling pathways involved in the development of malignant lung diseases. Different direct effects of particles as well as indirect cellular effects are believed to induce changes in apoptosis or proliferation in target cells. Signalling events, e.g. the induction of mitogen-activated protein kinase (MAPK) cascades resulting in the activation of the transcription factor AP-1, as well as the induction of the transcription factor NFkappaB which mainly mediates the expression of pro-inflammatory genes are discussed. There is some insight into the molecular mechanisms eliciting these pathways. Therefore, this review aims to give an overview on signalling pathways as well as initial events including effects of reactive oxygen and nitrogen species, membrane receptors and particle uptake.

To die or not to die: the function of the transcription factor NF-kappaB in embryos exposed to stress

BACKGROUND

Cytokines operating in the embryo and embryonic microenvironment determine, to a significant extent, whether pregnancy is completed successfully or results in embryonic loss or maldevelopment. They act as activators of specific transcription factors, which control cell responses such as cell proliferation differentiation and apoptosis. One such transcription factor is the nuclear factor-kappaB (NF-kappaB), which is presently seen as a key molecule controlling the apoptosis process. In the light of evidence that a majority of embryopathic stresses, regardless of their nature, first disturb the apoptotic process, it is conceivable, that NF-kappaB may play an important role in regulating the resistance of embryos to embryopathic stresses. In this brief review, we discuss such a possibility based on data characterizing expression and function of NF-kappaB in the embryo and extraembryonic tissues during normal embryogenesis as well as after exposure to various embryopathic stresses.

METHODS

Critical review of existing data.

RESULTS

Data summarized in this review suggest that (a) practically all NF-kappaB/Rel family members are expressed in embryonic, trophoblast and uterine cells in a developmental stage- and cell type-specific manner; (b) NF-kappaB-mediated anti-apoptotic signaling in embryonic cells seems to be indispensable for proper development during the organogenesis stage, (c) NF-kappaB activity in stress-targeted embryonic and extraembryonic structures directly correlates with their ability to resist stress-induced process of embryo loss and maldevelopment.

CONCLUSION

Data presented in this review suggest that NF-kappaB may act as a protector of embryos exposed to embryopathic stresses, possibly, because of the ability of NF-kappaB to prevent the induction of programmed cell death as well as to activate cell proliferation.

Inflammatory Time Course after Quartz Instillation

Inflammation has been suggested as the key factor in the development of quartz-induced fibrosis and carcinogenesis, and particle surface properties are argued as an important characteristic responsible for these pathologic alterations. To evaluate the effect of surface modification on acute and subchronic inflammation, female Wistar rats were intratracheally instilled with 2 mg native quartz, or quartz coated either with polyvinyl-pyridine-N-oxide or with aluminium lactate. Various markers of lung toxicity, inflammation, and oxidative stress were found to be enhanced at 3, 7, 21, and 90 d after instillation of native quartz. Quartz-treated animals also showed enhanced immunostaining of nuclear factor-kappaB (NF-kappaB) in alveolar macrophages and lung epithelium, as well as reduced IkappaBalpha levels in whole lung homogenate. Both surface modifications were found to inhibit most of the effects as observed with native quartz. NF-kappaB activation was also observed in vitro in rat lung epithelial cells following treatment with lavage fluid from quartz-treated animals, as well as with conditioned medium of quartz-treated macrophages, and these effects appeared to be at least partly tumor necrosis factor-alpha-independent. In conclusion, the persistent subchronic inflammatory lung response after quartz exposure appears to be particle surface-driven and is associated with NF-kappaB activation in both alveolar macrophages and the lung epithelium.

HTLV-I Tax induces a novel interaction between p65/RelA and p53 that results in inhibition of p53 transcriptional activity

Nuclear factor kappaB (NF-kappaB) activation plays a critical role in oncogenesis by human T-cell lymphotrophic virus type I (HTLV-I), the etiologic agent of adult T-cell leukemia (ATL), and is indispensable for maintenance of the malignant phenotype. In T lymphocytes, Tax-mediated p53 inhibition is dependent on Tax activation of the NF-kappaB pathway and is linked to p53 phosphorylation. We now report that blocking NF-kappaB transcriptional activation in HTLV-I-transformed cells restores p53 activity. Further, using mouse embryo fibroblast (MEF) null cells and antisense oligonucleotides to inhibit expression of NF-kappaB family members, we demonstrate that the p65 subunit of NF-kappaB is uniquely involved in p53 inhibition. Coimmunoprecipitation assays demonstrate an interaction between p65 and p53 in HTLV-I-transformed cells. In transient transfection assays, we demonstrate that Tax induces the p53-p65 interaction. Phosphorylation of p53 at serines 15 and 392 is critical for complex formation. Importantly, Tax-mediated p53 inhibition correlates with p65 and p53 interaction. By using chromatin immunoprecipitation (ChIP) assays, we find that in HTLV-I-transformed cells p53 and p65 form a complex on the inactive, p53-responsive murine double minute 2 (MDM2) promoter. Consistent with reduced transcriptional activity, transcription factor IID (TFIID) binding is not observed. These studies identify a unique mechanism for p53 regulation by the p65/RelA subunit of NF-kappaB.

Inverse correlation between p16INK4A expression and NF-kappaB activation in melanoma progression

Expression of p16INK4A, the product of the melanoma susceptibility gene CDKN2A, has been shown to decrease in correlation with tumor progression. P16INK4A is a key regulator of cell-cycle function, and likely interacts with a variety of targets alongside cyclin-dependent kinases (CDKs). One such target is nuclear factor KB (NF-kappaB), a pleiotropic transcription factor that plays a crucial role in apoptosis, oncogenesis and cell cycle control. NF-kappaB p65 has been shown to be activated in melanoma cell lines but few studies decribe its expression in the tissue. In the present study we focused on synchronous expression of p16INK4A and NF-kappaB p65 and their functional activation in melanoma cell lines and biopsy tissue. Activation of NF-kappaB p65, as observed by electrophoretic mobility shift assay in cell lines, was correlated with expression and cellular localization of the active and inactive forms of its inhibitor, IkappaB-alpha. In melanocytic lesions, p16INK4A and NF-kappaB p65 expression were inversely correlated with levels of the nuclear component of NF-kappaB p65 increasing from nevi to primary melanomas and metastases.

Novel therapies for pancreatic adenocarcinoma

Despite advances in our understanding of the molecular and genetic basis of pancreatic cancer, the disease remains a clinical challenge. Gemcitabine, the standard chemotherapy for pancreatic cancer, offers modest improvement of tumor-related symptoms and marginal advantage of survival. New approaches, alone and in combination with gemcitabine, are being developed to combat this cancer. In this article we review the current status of investigations into several classes of agents: matrix metalloproteinase inhibitors; farnesyl transferase inhibitors; epidermal growth factor receptor inhibitors, including monoclonal antibodies and tyrosine kinase inhibitors; cyclooxygenase-2 inhibitors, and others. The scientific rationale, mechanism of action, and clinical trial data for these novel agents are discussed.

Nuclear factor-kappaB: its role in health and disease

Nuclear factor-kappaB (NF-kappaB) is a major transcription factor that plays an essential role in several aspects of human health including the development of innate and adaptive immunity. The dysregulation of NF-kappaB is associated with many disease states such as AIDS, atherosclerosis, asthma, arthritis, cancer, diabetes, inflammatory bowel disease, muscular dystrophy, stroke, and viral infections. Recent evidence also suggests that the dysfunction of NF-kappaB is a major mediator of some human genetic disorders. Appropriate regulation and control of NF-kappaB activity, which can be achieved by gene modification or pharmacological strategies, would provide a potential approach for the management of NF-kappaB related human diseases. This review summarizes the current knowledge of the physiological and pathophysiological functions of NF-kappaB and its possible role as a target of therapeutic intervention

The role of oxidative stress in carcinogenesis

Chemical carcinogenesis follows a multistep process involving both mutation and increased cell proliferation. Oxidative stress can occur through overproduction of reactive oxygen and nitrogen species through either endogenous or exogenous insults. Important to carcinogenesis, the unregulated or prolonged production of cellular oxidants has been linked to mutation (induced by oxidant-induced DNA damage), as well as modification of gene expression. In particular, signal transduction pathways, including AP-1 and NFkappaB, are known to be activated by reactive oxygen species, and they lead to the transcription of genes involved in cell growth regulatory pathways. This review examines the evidence of cellular oxidants' involvement in the carcinogenesis process, and focuses on the mechanisms for production, cellular damage produced, and the role of signaling cascades by reactive oxygen species.

Suppression of Constitutive and Tumor Necrosis Factor α-Induced Nuclear Factor (NF)-κB Activation and Induction of Apoptosis by Apigenin in Human Prostate Carcinoma PC-3 Cells: Correlation with Down-Regulation of NF-κB-Responsive Genes

PURPOSE

Development of androgen independence and resistance to apoptosis in prostate cancer are often correlated with high levels of serum tumor necrosis factor (TNF)-alpha in these patients. The loss of sensitivity to TNF-alpha-induced apoptosis in androgen-insensitive prostate carcinoma cells is due in part to constitutive activation of Rel/nuclear factor (NF)-kappaB transcription factors that regulate several cell survival and antiapoptotic genes. Our previous studies have demonstrated growth inhibitory and apoptotic effects of apigenin, a common plant flavonoid, in a variety of human prostate carcinoma cells. Here we examined whether apigenin is effective in inhibiting NF-kappaB expression in androgen-insensitive human prostate carcinoma cells exhibiting high constitutive levels of NF-kappaB.

EXPERIMENTAL DESIGN

Using androgen-insensitive human prostate carcinoma PC-3 cells, the effect of apigenin was assessed on NF-kappaB activation by electrophoretic mobility shift assay and reporter gene assay. Expression of NF-kappaB subunits p65 and p50, IkappaBalpha, p-IkappaBalpha, in-beads kinase assay and NF-kappaB-regulated genes were determined by Western blot analysis. Apoptosis was determined by annexin V/propidium iodide staining after fluorescence-activated cell-sorting analysis.

RESULTS

Treatment of cells with 10-40- micro M doses of apigenin inhibited DNA binding and reduced nuclear levels of the p65 and p50 subunits of NF-kappaB. Apigenin inhibited IkappaBalpha degradation and IkappaBalpha phosphorylation and significantly decreased IKKalpha kinase activity. Apigenin also inhibited TNF-alpha-induced activation of NF-kappaB via the IkappaBalpha pathway, thereby sensitizing the cells to TNF-alpha-induced apoptosis. The inhibition of NF-kappaB activation correlated with a decreased expression of NF-kappaB-dependent reporter gene and suppressed expression of NF-kappaB-regulated genes [specifically, Bcl2, cyclin D1, cyclooxygenase-2, matrix metalloproteinase 9, nitric oxide synthase-2 (NOS-2), and vascular endothelial growth factor].

CONCLUSIONS

Our results indicate that inhibition of NF-kappaB by apigenin may lead to prostate cancer suppression by transcriptional repression of NF-kappaB-responsive genes as well as selective sensitization of prostate carcinoma cells to TNF-alpha-induced apoptosis.

Glucagon-like peptide-1 prevents beta cell glucolipotoxicity

AIMS/HYPOTHESIS

We have provided evidence that glucagon-like peptide-1, a potential therapeutic agent in the treatment of diabetes, activates phosphatidylinositol-3 kinase/protein kinase B signalling in the pancreatic beta cell. Since this pathway promotes cell survival in a variety of systems, we tested whether glucagon-like peptide-1 protects beta cells against cell death induced by elevated glucose and/or non-esterified fatty acids.

METHODS

Human islets and INS832/13 cells were cultured at glucose concentrations of 5 or 25 mmol/l in the presence or absence of palmitate. Apoptosis was evaluated by monitoring DNA fragmentation and chromatin condensation. Wild-type and protein kinase B mutants were overexpressed in INS832/13 cells using adenoviruses. Nuclear factor-kappa B DNA binding was assayed by electrophoretic mobility shift assay.

RESULTS

In human pancreatic beta cells and INS832/13 cells, glucagon-like peptide-1 prevented beta cell apoptosis induced by elevated concentrations of (i) glucose (glucotoxicity), (ii) palmitate (lipotoxicity) and (iii) both glucose and palmitate (glucolipotoxicity). Overexpression of a dominant-negative protein kinase B suppressed the anti-apoptotic action of glucagon-like peptide-1 in INS832/13 cells, whereas a constitutively active protein kinase B prevented beta cell apoptosis induced by elevated glucose and palmitate. Glucagon-like peptide-1 enhanced nuclear factor-kappa B DNA binding activity and stimulated the expression of inhibitor of apoptosis protein-2 and Bcl-2, two anti-apoptotic genes under the control of nuclear factor-kappa B. Inhibition of nuclear factor-kappa B by BAY 11-7082 abolished the prevention of glucolipotoxicity by glucagon-like peptide-1.

CONCLUSIONS/INTERPRETATION

The results demonstrate a potent protective effect of glucagon-like peptide-1 on beta cell gluco-, lipo- and glucolipotoxicity. This effect is mediated via protein kinase B activation and possibly its downstream target nuclear factor-kappa B.

Platelet-type 12-lipoxygenase activates NF-kappaB in prostate cancer cells

Platelet-type arachidonate 12-lipoxygenase (12-LOX) is highly expressed in many types of cancers and plays an important role in cancer pathophysiology. Arachidonic acid metabolism by 12-LOX results in the stable end product 12(S)-hydroxy eicosatetraenoic acid (12(S)-HETE), which is a signaling molecule with effects on cell proliferation, motility, invasiveness, angiogenesis, and inhibition of apoptosis. The myriad biological activities manifested by 12(S)-HETE appear to be mediated, at least in part, by the activation of NF-kappaB. Overexpression of the 12-LOX in PC-3 prostate cancer cells resulted in the constitutive activation of the transcription factor. The enzymatic product of arachidonic acid metabolism, 12(S)-HETE, mediates the activation of NF-kappaB by the 12-LOX. 12(S)-HETE treatment of PC-3 cells induced the degradation of IkappaB by the S6 proteasomal pathway and the activated NF-kappaB translocated to the nucleus causing kappaB-induced transcription. Specificity of the NF-kappaB activation by 12(S)-HETE was established by the use of a 12-LOX-specific inhibitor and 13(S)-HODE, a known 12(S)-HETE antagonist. Considering the known involvement of MAP kinase pathway in NF-kappaB activation and that of 12(S)-HETE in MAP kinase pathway, 12-LOX present in prostate cancer tissues may contribute to the constitutive activation of NF-kappaB in prostate cancer cells.

Effects of the proteasome inhibitor PS-341 on tumor growth in HTLV-1 Tax transgenic mice and Tax tumor transplants

Recent studies have shown that the transcription factor nuclear factor kappaB (NF-kappaB) regulates critical survival pathways in a variety of cancers, including human T-cell leukemia/lymphotrophic virus 1 (HTLV-1)-transformed CD4 T cells. The activation of NF-kappaB is controlled by proteasome-mediated degradation of the inhibitor of nuclear factor kappaBalpha (IkappaBalpha). We investigated the effects of PS-341, a peptide boronate inhibitor of the proteasome in HTLV-1 Tax transgenic tumors in vitro and in vivo. In Tax transgenic mice, PS-341 administered thrice weekly inhibited tumor-associated NF-kappaB activity. Quantitation of proliferation, apoptosis, and interleukin 6 (IL-6) and IL-10 secretion by tumor cells in culture revealed that the effects of PS-341 on cell growth largely correlated with inhibition of pathways mediated by NF-kappaB. However, the effect of PS-341 on the growth of tumors in Tax transgenic mice revealed heterogeneity in drug responsiveness. The tumor tissues treated with PS-341 show no consistent inhibition of NFkappaB activation in vivo. Annexin V staining indicated that PS-341 response in vivo correlated with sensitivity to apoptosis induced by gamma irradiation. On the other hand, transplanted Tax tumors in Rag-1 mice showed consistent inhibition of tumor growth and prolonged survival in response to the same drug regimen. TUNEL staining indicated that PS-341 treatment sensitizes Tax tumors to DNA fragmentation.

Microarray analysis identifies Autotaxin, a tumour cell motility and angiogenic factor with lysophospholipase D activity, as a specific target of cell transformation by v-Jun

We have used chicken cDNA microarrays to investigate gene-expression changes induced during transformation of chick embryo fibroblasts (CEF) by the viral Jun oncoprotein encoded by ASV17. This analysis reveals that v-Jun induces increases and decreases of varying magnitude in the expression of genes involved in diverse cellular functions, most of which have not been detected in previous screens for putative v-Jun targets. In all, 27 individual genes were identified, whose expression is increased threefold or more in v-Jun-transformed cells, including genes involved in energy generation, protein synthesis, and gene transcription. Interestingly, this group includes the hypoxia-inducible factor-1 alpha (Hif-1alpha) transcription factor and the glycolytic enzyme enolase, suggesting that adaptation to hypoxia could play a role in tumorigenesis by v-Jun. We also identified 32 genes whose expression is decreased threefold or more, including chaperones, components of the cytoskeleton, and, unexpectedly, DNA replication factors. The gene whose expression is upregulated most dramatically (approximately 100-fold) encodes Autotaxin (ATX), a secreted tumor motility-promoting factor with lysophospholipase D activity. Strikingly, v-Jun-transformed CEF secrete catalytically active ATX and chemotactic activity, which can be detected in conditioned medium. ATX is not detectably expressed in normal CEF or CEF transformed by the v-Src or v-Myc oncoproteins, indicating that induction of this putative autocrine/paracrine factor is a specific consequence of cell transformation by v-Jun. ATX has been implicated in both angiogenesis and invasion, and could therefore play an important role in tumorigenesis by v-Jun in vivo.

Hydrostatic pressure induces apoptosis in human chondrocytes from osteoarthritic cartilage through up-regulation of tumor necrosis factor-alpha, inducible nitric oxide synthase, p53, c-myc, and bax-alpha, and suppression of bcl-2

Hydrostatic pressure (HP) is thought to increase within cartilage extracellular matrix as a consequence of fluid flow inhibition. The biosynthetic response of human articular chondrocytes to HP in vitro varies with the load magnitude, load frequency, as well as duration of loading. We found that continuous cyclic HP (5 MegaPascals (MPa) for 4 h; 1 Hz frequency) induced apoptosis in human chondrocytes derived from osteoarthritic cartilage in vitro as evidenced by reduced chondrocyte viability which was independent of initial cell densities ranging from 8.1 x 10(4) to 1.3 x 10(6) cells ml(-1). HP resulted in internucleosomal DNA fragmentation, activation of caspase-3, and cleavage of poly-ADP-ribose polymerase (PARP). At the molecular level, induction of apoptosis by HP was characterized by up-regulation of p53, c-myc, and bax-alpha after 4 h with concomitant down-regulation of bcl-2 after 2 h at 5 MPa as measured by RT-PCR. In contrast, beta-actin expression was unchanged. Real-time quantitative RT-PCR confirmed a HP-induced (5 MPa) 1.3-2.6 log-fold decrease in bcl-2 mRNA copy number after 2 and 4 h, respectively, and a significant increase (1.9-2.5 log-fold) in tumor necrosis factor-alpha (TNF-alpha) and inducible nitric oxide synthase (iNOS) mRNA copy number after 2 and 4 h, respectively. The up-regulation of p53 and c-myc, and the down-regulation of bcl-2 caused by HP were confirmed at the protein level by Western blotting. These results indicated that HP is a strong inducer of apoptosis in osteoarthritic human chondrocytes in vitro.

A cellular UDP-glucose deficiency causes overexpression of glucose/oxygen-regulated proteins independent of the endoplasmic reticulum stress elements

A low level of UDP-Glc occurs in cells exposed to hypoxia or glucose starvation. This work reveals that a 65% reduction in the cellular UDP-Glc level causes up-regulation of the mitochondrial chaperone GRP75 and the endoplasmic reticulum (ER) resident chaperones GRP58, ERp72, GRP78, GRP94, GRP170, and calreticulin. Conditions that cause misfolding of proteins within the ER activate the transcription factors ATF6alpha/beta and induce translation of the transcription factors XBP-1/TREB5 and ATF4/CREB2. These transcription factors induce the overexpression of ER chaperones and CHOP/GADD153. However, the 65% decrease in the cellular UDP-Glc level does not cause activation of ATF6alpha, splicing of XBP-1/TREB5, induction of ATF4/CREB2, or expression of CHOP/GADD153. The activity of the promoters of the ER chaperones is increased in UDP-Glc-deficient cells, but the activity of the CHOP/GADD153 promoter is not affected, in comparison with their respective activities in cells having compensated for the UDP-Glc deficiency. The results demonstrate that the unfolded protein response remains functionally intact in cells with a 65% decrease in the cellular UDP-Glc level and provide evidence that this decrease is a stress signal in mammalian cells, which triggers the coordinate overexpression of mitochondrial and ER chaperones, independently of the ER stress elements.

Hepatocyte growth factor-induced proliferation of hepatic stem-like cells depends on activation of NF-kappaB

BACKGROUND/AIMS

Hepatocyte growth factor (HGF) regulates proliferation of hepatic stem cells. Transcription factor nuclear factor kappa B (NF-kappaB) has been demonstrated as a key mediator for cell growth regulation. We investigated the role of NF-kappaB in HGF-mediated cellular proliferation responses in a rat liver-derived hepatic stem-like cell line WB-F344.

METHODS

Cell proliferation was determined by incorporation of [3H]thymidine. Phosphorylation of ERK1/2, p38 MAPK, Akt and IkappaBalpha by HGF stimulation was detected by Western blotting. NF-kappaB activation was determined by electrophoretic mobility shift assay and NF-kappaB-mediated SEAP reporter assay. NF-kappaB activation was inhibited by treatment with an IkappaBalpha dominant-negative vector or inhibitor BAY-11-7082.

RESULTS

We found that stimulation of WB-F344 cells with HGF promoted cell proliferation and effectively protected WB-F344 cells from apoptosis induced by TNF-alpha. We also observed activation of ERK1/2, p38 MAPK, Akt and NF-kappaB signaling pathways by HGF in WB-F344 cells. HGF-induced cell proliferation was partly blocked by pre-treatment of the cells with inhibitors against MEK1 or p38 MAPK, and completely blocked using an inhibitor for NF-kappaB activity. Furthermore, it was demonstrated that IkappaB mutant that suppressed NF-kappaB activity completely blocked HGF-induced cell proliferation.

CONCLUSIONS

NF-kappaB activity is required for HGF-induced proliferation in hepatic stem-like cell line WB-F344, and this activity requires ERK1/2 and p38 MAPK pathways.

Multifaceted roles of TNF-alpha in myoblast destruction: a multitude of signal transduction pathways

In catabolic conditions, such as cancer cachexia, a balance favouring a cytokine environment culminates in muscle destruction. Utilising an in vitro model to mimic muscle wasting, we elucidate here the multifaceted roles that one such cytokine, TNF-alpha, invokes in the degeneration process. Treatment of C2 skeletal myoblasts with TNF-alpha not only suppresses morphological and biochemical differentiation, but following an initial wave of proliferation, and of survival (24 h), induces apoptosis. Investigating the mechanisms underlying these diverse actions of TNF-alpha, we demonstrate that cell replication is dependent on rapid and sustained activation of MAP kinase. Map kinase is not, however, central to the death process, which is associated with a progressive rise in caspase-8 activity, and is accompanied by sustained activation of JNK1 and transient activation of JNK2. Caspase inhibition caused a dose responsive reduction in cell death, while inhibition of the JNKs caused a significant increase in apoptosis. We further report that PI3 kinase is not involved in conferring early protection against TNF-alpha-induced death. By contrast, inhibition of NF-kappaB in the presence of TNF-alpha culminates in increased cell cycle progression, decreased gadd45beta expression and significant and precociously increased cell death, when compared with TNF-alpha alone. Our results begin to characterise the mechanisms underlying the acute mitogenic and anti-apoptotic roles of TNF-alpha, which appear to be defined by a balance between MAP kinase, Jun kinase (JNK), NF-kappaB and gadd45beta. They establish that inhibition of any one of these molecules, as may occur following caspase activation, could eliminate vital stem cells required for skeletal muscle regeneration during chronic catabolic conditions.

Thioredoxin is associated with proliferation, p53 expression and negative estrogen and progesterone receptor status in breast carcinoma

We investigated the expression of thioredoxin and thioredoxin reductase in a large set of breast invasive and in situ carcinomas by immunohistochemistry. Additionally, NF-kappa B, p53 and proliferating cell nuclear antigen (PCNA) expression was studied. Thioredoxin and thioredoxin reductase expression was located in both cytoplasmic and nuclear compartments of the cell. Cytoplasmic thioredoxin positivity was found in 67 % and nuclear in 59 % of the cases, while thioredoxin reductase was found in 55 % and 6 % of cases, respectively. Ductal carcinomas showed stronger cytoplasmic thioredoxin immunoreactivity than lobular ones. Nuclear thioredoxin positivity was more often found in in situ lesions, and lobular carcinomas were more often negative than ductal ones. Both cytoplasmic and nuclear thioredoxin-positive cases had a high proliferation measured by PCNA staining. Positive nuclear immunostaining was associated with negative estrogen and progesterone receptor status. Cases with high p53 expression showed significantly higher nuclear thioredoxin positivity, but lower thioredoxin reductase positivity. Whilst thioredoxin or thioredoxin reductase was not associated with patient survival, cases showing both cytoplasmic and nuclear thioredoxin reductase-positive tumours had a shorter disease-free interval than those with negative immunostaining.

Acquired resistance of human T cells to sulfasalazine: stability of the resistant phenotype and sensitivity to non-related DMARDs

BACKGROUND

A recent study from our laboratory showed that induction of the multidrug resistance related drug efflux pump ABCG2 contributed to acquired resistance of human T cells to the disease modifying antirheumatic drug (DMARD) sulfasalazine (SSZ).

OBJECTIVES

To investigate the duration of SSZ resistance and ABCG2 expression after withdrawal of SSZ and rechallenging with SSZ, and to assess the impact of SSZ resistance on responsiveness to other DMARDs.

METHODS

Human CEM cells (T cell origin) with acquired resistance to SSZ (CEM/SSZ) were characterised for (a) SSZ sensitivity and ABCG2 expression during withdrawal and rechallenge of SSZ, and (b) antiproliferative efficacy of other DMARDs.

RESULTS

ABCG2 protein expression was stable for at least 4 weeks when CEM/SSZ cells were grown in the absence of SSZ, but gradually declined, along with SSZ resistance levels, to non-detectable levels after withdrawal of SSZ for 6 months. Rechallenging with SSZ led to a rapid (<2.5 weeks) resumption of SSZ resistance and ABCG2 expression as in the original CEM/SSZ cells. CEM/SSZ cells displayed diminished sensitivity to the DMARDs leflunomide (5.1-fold) and methotrexate (1.8-fold), were moderately more sensitive (1.6-2.0 fold) to cyclosporin A and chloroquine, and markedly more sensitive (13-fold) to the glucocorticoid dexamethasone as compared with parental CEM cells.

CONCLUSION

The drug efflux pump ABCG2 has a major role in conferring resistance to SSZ. The collateral sensitivity of SSZ resistant cells for some other (non-related) DMARDs may provide a further rationale for sequential mono- or combination therapies with distinct DMARDs upon decreased efficacy of SSZ.