Yasunari Takada

Nuclear factor-κB: its role in health and disease

Nuclear factor-κB (NF-κB) 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-κB 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-κB is a major mediator of some human genetic disorders. Appropriate regulation and control of NF-κB activity, which can be achieved by gene modification or pharmacological strategies, would provide a potential approach for the management of NF-κB related human diseases. This review summarizes the current knowledge of the physiological and pathophysiological functions of NF-κB and its possible role as a target of therapeutic intervention

Nuclear factor-?B: its role in health and disease

Nuclear factor-κB (NF-κB) 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-κB 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-κB is a major mediator of some human genetic disorders. Appropriate regulation and control of NF-κB activity, which can be achieved by gene modification or pharmacological strategies, would provide a potential approach for the management of NF-κB related human diseases. This review summarizes the current knowledge of the physiological and pathophysiological functions of NF-κB and its possible role as a target of therapeutic intervention

Curcumin Suppresses the Paclitaxel-Induced Nuclear Factor-κB Pathway in Breast Cancer Cells and Inhibits Lung Metastasis of Human Breast Cancer in Nude Mice

Currently, there is no effective therapy for metastatic breast cancer after surgery, radiation, and chemotherapy have been used against the primary tumor. Because curcumin suppresses nuclear factor-κB (NF-κB) activation and most chemotherapeutic agents activate NF-κB that mediates cell survival, proliferation, invasion, and metastasis, we hypothesized that curcumin would potentiate the effect of chemotherapy in advanced breast cancer and inhibit lung metastasis. We tested this hypothesis using paclitaxel (Taxol)-resistant breast cancer cells and a human breast cancer xenograft model. As examined by electrophoretic mobility gel shift assay, paclitaxel activated NF-κB in breast cancer cells and curcumin inhibited it; this inhibition was mediated through inhibition of IκBα kinase activation and IκBα phosphorylation and degradation. Curcumin also suppressed the paclitaxel-induced expression of antiapoptotic (XIAP, IAP-1, IAP-2, Bcl-2, and Bcl-xL), proliferative (cyclooxygenase 2, c-Myc, and cyclin D1), and metastatic proteins (vascular endothelial growth factor, matrix metalloproteinase-9, and intercellular adhesion molecule-1). It also enhanced apoptosis. In a human breast cancer xenograft model, dietary administration of curcumin significantly decreased the incidence of breast cancer metastasis to the lung and suppressed the expression of NF-κB, cyclooxygenase 2, and matrix metalloproteinase-9. Overall, our results indicate that curcumin, which is a pharmacologically safe compound, has a therapeutic potential in preventing breast cancer metastasis possibly through suppression of NF-κB and NF-κB–regulated gene products.

Evidence that curcumin suppresses the growth of malignant gliomas in vitro and in vivo through induction of autophagy: role of Akt and extracellular signal-regulated kinase signaling pathways.

Autophagy is a response of cancer cells to various anticancer therapies. It is designated as programmed cell death type II and characterized by the formation of autophagic vacuoles in the cytoplasm. The Akt/mammalian target of rapamycin (mTOR)/p70 ribosomal protein S6 kinase (p70S6K) and the extracellular signal-regulated kinases 1/2 (ERK1/2) pathways are two major pathways that regulate autophagy induced by nutrient starvation. These pathways are also frequently associated with oncogenesis in a variety of cancer cell types, including malignant gliomas. However, few studies have examined both of these signal pathways in the context of anticancer therapy-induced autophagy in cancer cells, and the effect of autophagy on cell death remains unclear. Here, we examined the anticancer efficacy and mechanisms of curcumin, a natural compound with low toxicity in normal cells, in U87-MG and U373-MG malignant glioma cells. Curcumin induced G2/M arrest and nonapoptotic autophagic cell death in both cell types. It inhibited the Akt/mTOR/p70S6K pathway and activated the ERK1/2 pathway, resulting in induction of autophagy. It is interesting that activation of the Akt pathway inhibited curcumin-induced autophagy and cytotoxicity, whereas inhibition of the ERK1/2 pathway inhibited curcumin-induced autophagy and induced apoptosis, thus resulting in enhanced cytotoxicity. These results imply that the effect of autophagy on cell death may be pathway-specific. In the subcutaneous xenograft model of U87-MG cells, curcumin inhibited tumor growth significantly (P < 0.05) and induced autophagy. These results suggest that curcumin has high anticancer efficacy in vitro and in vivo by inducing autophagy and warrant further investigation toward possible clinical application in patients with malignant glioma.

Hydrogen Peroxide Activates NF-κB through Tyrosine Phosphorylation of IκBα and Serine Phosphorylation of p65 EVIDENCE FOR THE INVOLVEMENT OF IκBα KINASE AND Syk PROTEIN-TYROSINE KINASE

Although it is well established that reactive oxygen intermediates mediate the NF-κB activation induced by most agents, how H2O2 activates this transcription factor is not well understood. We found that treatment of human myeloid KBM-5 cells with H2O2 activated NF-κB in a dose- and time-dependent manner much as tumor necrosis factor (TNF) did but unlike TNF, H2O2 had no effect on IκBα degradation. Unexpectedly, however, like TNF-induced activation, H2O2-induced NF-κB activation was blocked by the calpain inhibitor N-Ac-Leu-Leu-norleucinal, suggesting that a proteosomal pathway was involved. Although H2O2 activated IκBα kinase, it did not induce the serine phosphorylation of IκBα. Like TNF, H2O2 induced the serine phosphorylation of the p65 subunit of NF-κB, leading to its nuclear translocation. We found that H2O2 induced the tyrosine phosphorylation of IκBα, which is needed for NF-κB activation. We present several lines of evidence to suggest that the Syk protein-tyrosine kinase is involved in H2O2-induced NF-κB activation. First, H2O2 activated Syk in KBM-5 cells; second, H2O2 failed to activate NF-κB in cells that do not express Syk protein; third, overexpression of Syk increased H2O2-induced NF-κB activation; and fourth, reduction of Syk transcription using small interfering RNA inhibited H2O2-induced NF-κB activation. We also showed that Syk induced the tyrosine phosphorylation of IκBα, which caused the dissociation, phosphorylation, and nuclear translocation of p65. Thus, overall, our results demonstrate that H2O2 induces NF-κB activation, not through serine phosphorylation or degradation of IκBα, but through Syk-mediated tyrosine phosphorylation of IκBα

Nonsteroidal anti-inflammatory agents differ in their ability to suppress NF-κB activation, inhibition of expression of cyclooxygenase-2 and cyclin D1, and abrogation of tumor cell proliferation

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin have been shown to suppress transcription factor NF-κB, which controls the expression of genes such as cyclooxygenase (COX)-2 and cyclin D1, leading to inhibition of proliferation of tumor cells. There is no systematic study as to how these drugs differ in their ability to suppress NF-κB activation and NF-κB-regulated gene expression or cell proliferation. In the present study, we investigated the effect of almost a dozen different commonly used NSAIDs on tumor necrosis factor (TNF)-induced NF-κB activation and NF-κB-regulated gene products, and on cell proliferation. Dexamethasone, an anti-inflammatory steroid, was included for comparison with NSAIDs. As indicated by DNA binding, none of the drugs alone activated NF-κB. All compounds inhibited TNF-induced NF-κB activation, but with highly variable efficacy. The 50% inhibitory concentration required was 5.67, 3.49, 3.03, 1.25, 0.94, 0.60, 0.38, 0.084, 0.043, 0.027, 0.024, and 0.010 mM for aspirin, ibuprofen, sulindac, phenylbutazone, naproxen, indomethacin, diclofenac, resveratrol, curcumin, dexamethasone, celecoxib, and tamoxifen, respectively. All drugs inhibited IκBα kinase and suppressed IκBα degradation and NF-κB-regulated reporter gene expression. They also suppressed NF-κB-regulated COX-2 and cyclin D1 protein expression in a dose-dependent manner. All compounds inhibited the proliferation of tumor cells, with 50% inhibitory concentrations of 6.09, 1.12, 0.65, 0.49, 1.01, 0.19, 0.36, 0.012, 0.016, 0.047, 0.013, and 0.008 mM for aspirin, ibuprofen, sulindac, phenylbutazone, naproxen, indomethacin, diclofenac, resveratrol, curcumin, dexamethasone, celecoxib, and tamoxifen, respectively. Overall these results indicate that aspirin and ibuprofen are least potent, while resveratrol, curcumin, celecoxib, and tamoxifen are the most potent anti-inflammatory and antiproliferative agents of those we studied.

Inhibition of growth and survival of human head and neck squamous cell carcinoma cells by curcumin via modulation of nuclear factor-κB signaling

Increased expression of proinflammatory and proangiogenic factors are associated with aggressive tumor growth and decreased survival of patients with head and neck squamous cell carcinoma (HNSCC). In as much as genes that are regulated by nuclear factor NF‐κB suppress apoptosis, induce proliferation, and mediate inflammation, angiogenesis and tumor metastasis, agents that suppress NF‐κB activation have potential as treatment for various cancers including HNSCC. We demonstrate that all HNSCC cell lines expressed constitutively active NF‐κB and IκBα kinase (IKK), which is needed for NF‐κB activation. Treatment of MDA 686LN cells with curcumin (diferuloylmethane), a pharmacologically safe chemopreventive agent, inhibited NF‐κB activation through abrogation of IKK. As a result expression of various cell survival and cell proliferative genes including Bcl‐2, cyclin D1, IL‐6, COX‐2 and MMP‐9 was suppressed. This, in turn, inhibits proliferation of all HNSCC cell lines, arrests cell cycle in G1/S phase (MDA 686LN) and induces apoptosis as indicated by upstream and downstream caspase activation, PARP cleavage, annexin V staining in MDA 686LN cells. Suppression of NF‐κB by cell‐permeable p65‐based peptide and NBD peptide also inhibited the proliferation and induced apoptosis in these cells. Our results indicate that curcumin is a potent inhibitor of cell proliferation and an inducer of apoptosis in HNSCC through suppression of IKK‐mediated NF‐κB activation and of NF‐κB‐regulated gene expression.

(DIFERULOYLMETHANE) INHIBITS RECEPTOR ACTIVATOR OF NFKAPPA B LIGAND-INDUCED NF-KAPPA B ACTIVATION IN OSTEOCLAST PRECURSORS AND SUPPRESSES OSTEOCLASTOGENESIS

Numerous studies have indicated that inflammatory cytokines play a major role in osteoclastogenesis, leading to the bone resorption that is frequently associated with cancers and other diseases. Gene deletion studies have shown that receptor activator of NF-κB ligand (RANKL) is one of the critical mediators of osteoclastogenesis. How RANKL mediates osteoclastogenesis is not fully understood, but an agent that suppresses RANKL signaling has potential to inhibit osteoclastogenesis. In this report, we examine the ability of curcumin (diferuloylmethane), a pigment derived from turmeric, to suppress RANKL signaling and osteoclastogenesis in RAW 264.7 cells, a murine monocytic cell line. Treatment of these cells with RANKL activated NF-κB, and preexposure of the cells to curcumin completely suppressed RANKL-induced NF-κB activation. Curcumin inhibited the pathway leading from activation of IκBα kinase and IκBα phosphorylation to IκBα degradation. RANKL induced osteoclastogenesis in these monocytic cells, and curcumin inhibited both RANKL- and TNF-induced osteoclastogenesis and pit formation. Curcumin suppressed osteoclastogenesis maximally when added together with RANKL and minimally when it was added 2 days after RANKL. Whether curcumin inhibits RANKL-induced osteoclastogenesis through suppression of NF-κB was also confirmed independently, as RANKL failed to activate NF-κB in cells stably transfected with a dominant-negative form of IκBα and concurrently failed to induce osteoclastogenesis. Thus overall these results indicate that RANKL induces osteoclastogenesis through the activation of NF-κB, and treatment with curcumin inhibits both the NF-κB activation and osteoclastogenesis induced by RANKL.

Withanolides potentiate apoptosis, inhibit invasion, and abolish osteoclastogenesis through suppression of nuclear factor-κB (NF-κB) activation and NF-κB–regulated gene expression

The plant Withania somnifera Dunal (Ashwagandha), also known as Indian ginseng, is widely used in the Ayurvedic system of medicine to treat tumors, inflammation, arthritis, asthma, and hypertension. Chemical investigation of the roots and leaves of this plant has yielded bioactive withanolides. Earlier studies showed that withanolides inhibit cyclooxygenase enzymes, lipid peroxidation, and proliferation of tumor cells. Because several genes that regulate cellular proliferation, carcinogenesis, metastasis, and inflammation are regulated by activation of nuclear factor-κB (NF-κB), we hypothesized that the activity of withanolides is mediated through modulation of NF-κB activation. For this report, we investigated the effect of the withanolide on NF-κB and NF-κB-regulated gene expression activated by various carcinogens. We found that withanolides suppressed NF-κB activation induced by a variety of inflammatory and carcinogenic agents, including tumor necrosis factor (TNF), interleukin-1β, doxorubicin, and cigarette smoke condensate. Suppression was not cell type specific, as both inducible and constitutive NF-κB activation was blocked by withanolides. The suppression occurred through the inhibition of inhibitory subunit of IκBα kinase activation, IκBα phosphorylation, IκBα degradation, p65 phosphorylation, and subsequent p65 nuclear translocation. NF-κB-dependent reporter gene expression activated by TNF, TNF receptor (TNFR) 1, TNFR-associated death domain, TNFR-associated factor 2, and IκBα kinase was also suppressed. Consequently, withanolide suppressed the expression of TNF-induced NF-κB-regulated antiapoptotic (inhibitor of apoptosis protein 1, Bfl-1/A1, and FADD-like interleukin-1β-converting enzyme–inhibitory protein) and metastatic (cyclooxygenase-2 and intercellular adhesion molecule-1) gene products, enhanced the apoptosis induced by TNF and chemotherapeutic agents, and suppressed cellular TNF-induced invasion and receptor activator of NF-κB ligand-induced osteoclastogenesis. Overall, our results indicate that withanolides inhibit activation of NF-κB and NF-κB-regulated gene expression, which may explain the ability of withanolides to enhance apoptosis and inhibit invasion and osteoclastogenesis. [Mol Cancer Ther 2006;5(6):1434–45]

Betulinic Acid Suppresses Carcinogen-Induced NF-κB Activation Through Inhibition of IκBα Kinase and p65 Phosphorylation: Abrogation of Cyclooxygenase-2 and Matrix Metalloprotease-9

Betulinic acid (BA), a pentacyclic triterpene isolated from the bark of the white birch tree, has been reported to be a selective inducer of apoptosis in tumor cells. It also exhibits anti-inflammatory and immunomodulatory properties. How BA mediates these effects is not known. Because of the critical role of the transcription factor NF-κB in growth modulatory, inflammatory, and immune responses, we postulated that BA modulates the activity of this factor. In this study we investigated the effect of BA on NF-κB and NF-κB-regulated gene expression activated by a variety of inflammatory and carcinogenic agents. BA suppressed NF-κB activation induced by TNF, PMA, cigarette smoke, okadaic acid, IL-1, and H2O2. The suppression of NF-κB activation was not cell-type specific. BA suppressed the activation of IκBα kinase, thus abrogating the phosphorylation and degradation of IκBα. We found that BA inhibited NF-κB activated by TNFR 1, TNFR-associated death domain, TNFR-associated factor 2, NF-κB-inducing kinase, and IκBα kinase. Treatment of cells with this triterpinoid also suppressed NF-κB-dependent reporter gene expression and the production of NF-κB-regulated gene products such as cyclooxygenase-2 and matrix metaloproteinase-9 induced by inflammatory stimuli. Furthermore, BA enhanced TNF-induced apoptosis. Overall, our results indicated that BA inhibits activation of NF-κB and NF-κB-regulated gene expression induced by carcinogens and inflammatory stimuli. This may provide a molecular basis for the ability of BA to mediate apoptosis, suppress inflammation, and modulate the immune response.