Haruyo Ichikawa

Targeting Signal-Transducer-and-Activator-of-Transcription-3 for Prevention and Therapy of Cancer

Abstract:  Recent evidence indicates a convergence of molecular targets for both prevention and therapy of cancer. Signal‐transducer‐and‐activator‐of‐transcription‐3 (STAT3), a member of a family of six different transcription factors, is closely linked with tumorigenesis. Its role in cancer is indicated by numerous avenues of evidence, including the following: STAT3 is constitutively active in tumor cells; STAT3 is activated by growth factors (e.g., EGF, TGF‐α, IL‐6, hepatocyte growth factor) and oncogenic kinases (e.g., Src); STAT3 regulates the expression of genes that mediate proliferation (e.g., c‐myc and cyclin D1), suppress apoptosis (e.g., Bcl‐xL and survivin), or promote angiogenesis (e.g, VEGF); STAT3 activation has been linked with chemoresistance and radioresistance; and chemopreventive agents have been shown to suppress STAT3 activation. Thus inhibitors of STAT3 activation have potential for both prevention and therapy of cancer. Besides small peptides and oligonucleotides, numerous small molecules have been identified as blockers of STAT3 activation, including synthetic molecules (e.g., AG 490, decoy peptides, and oligonucleotides) and plant polyphenols (e.g., curcumin, resveratrol, flavopiridol, indirubin, magnolol, piceatannol, parthenolide, EGCG, and cucurbitacin). This article discusses these aspects of STAT3 in more detail.

Molecular targets and anticancer potential of indole-3-carbinol and its derivatives

Indole-3-carbinol (I3C) is produced by members of the family Cruciferae, and particularly members of the genus Brassica (e.g., cabbage, radishes, cauliflower, broccoli, Brussels sprouts, and daikon). Under acidic conditions, 13C is converted to a series of oligomeric products (among which 3,3’-diindolylmethane is a major component) thought to be responsible for its biological effects in vivo. In vitro, 13C has been shown to suppress the proliferation of various tumor cells including breast cancer, prostate cancer, endometrial cancer, colon cancer, and leukemic cells; induce G1/S arrest of the cell cycle, and induce apoptosis. The cell cycle arrest involves downregulation of cyclin D1, cyclin E, cyclin-dependent kinase (CDK)2, CDK4, and CDK6 and upregulation of p15, p21, and p27. Apoptosis by I3C involves downregulation antiapoptotic gene products, including bcl-2, bcl-xl, survivin, inhibitor-of-apoptosis protein (IAP), X chromosome-linked IAP (XIAP), and Fas-associated death domain protein-like interleukin-1-b-converting enzyme inhibitory protein (FLIP); upregulation of proapoptotic protein bax; release of micochondrial cytochrome C; and activation of caspase-9 and caspase-3. This agent inhibits the activation of various transcription factors including nuclear factor-kappaB, SP1, estrogen receptor, androgen receptor and nuclear factor-E2-related factor 2 (Nrf2). This indole potentiates the effects of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) through induction of death receptors and synergises with chemotherapeutic agents through downregulation of P-glycoprotein (P-gp). In vivo, I3C was found to be a potent chemopreventive agent for hormonal-dependent cancers such as breast and cervical cancer. These effects are mediated through its ability to induce apoptosis, inhibit DNA-carcinogen adduct formation, and suppress free-radical production, stimulate 2-hydroxylation of estradiol, inhibit invasion and angiogenesis. Numerous studies have indicated that I3C also has a strong hepatoprotective activity against various carcinogens. Initial clinical trials in women have shown that I3C is a promising agent against breast and cervical cancers.

Plumbagin (5-Hydroxy-2-methyl-1,4-naphthoquinone) Suppresses NF-κB Activation and NF-κB-regulated Gene Products Through Modulation of p65 and IκBα Kinase Activation, Leading to Potentiation of Apoptosis Induced by Cytokine and Chemotherapeutic Agents

Plumbagin, derived from the medicinal plant Plumbago zeylanica, modulates cellular proliferation, carcinogenesis, and radioresistance, all known to be regulated by the activation of the transcription factor NF-κB, suggesting plumbagin might affect the NF-κB activation pathway. We found that plumbagin inhibited NF-κB activation induced by TNF, and other carcinogens and inflammatory stimuli (e.g. phorbol 12-myristate 13-acetate, H2O2, cigarette smoke condensate, interleukin-1β, lipopolysaccharide, and okadaic acid). Plumbagin also suppressed the constitutive NF-κB activation in certain tumor cells. The suppression of NF-κB activation correlated with sequential inhibition of the tumor necrosis factor (TNF)-induced activation of IκBα kinase, IκBα phosphorylation, IκBα degradation, p65 phosphorylation, p65 nuclear translocation, and the NF-κB-dependent reporter gene expression activated by TNF, TNFR1, TRAF2, NIK, IKK-β, and the p65 subunit of NF-κB. Plumbagin also suppressed the direct binding of nuclear p65 and recombinant p65 to the DNA, and this binding was reversed by dithiothreitol both in vitro and in vivo. However, plumbagin did not inhibit p65 binding to DNA when cells were transfected with the p65 plasmid containing cysteine 38 mutated to serine. Plumbagin down-regulated the expression of NF-κB-regulated anti-apoptotic (IAP1, IAP2, Bcl-2, Bcl-xL, cFLIP, Bfl-1/A1, and survivin), proliferative (cyclin D1 and COX-2), and angiogenic (matrix metalloproteinase-9 and vascular endothelial growth factor) gene products. This led to potentiation of apoptosis induced by TNF and paclitaxel and inhibited cell invasion. Overall, our results indicate that plumbagin is a potent inhibitor of the NF-κB activation pathway that leads to suppression of NF-κB-regulated gene products. This may explain its cell growth modulatory, anticarcinogenic, and radiosensitizing effects previously described.

From traditional Ayurvedic medicine to modern medicine: identification of therapeutic targets for suppression of inflammation and cancer

Cancer is a hyperproliferative disorder that involves transformation, dysregulation of apoptosis, proliferation, invasion, angiogenesis and metastasis. Extensive research during the last 30 years has revealed much about the biology of cancer. Drugs used to treat most cancers are those that can block cell signalling, including growth factor signalling (e.g., epidermal growth factor); prostaglandin production (e.g., COX-2); inflammation (e.g., inflammatory cytokines: NF-κB, TNF, IL-1, IL-6, chemokines); drug resistance gene products (e.g., multi-drug resistance); cell cycle proteins (e.g., cyclin D1 and cyclin E); angiogenesis (e.g., vascular endothelial growth factor); invasion (e.g., matrix metalloproteinases); antiapoptosis (e.g., bcl-2, bcl-XL, XIAP, survivin, FLIP); and cellular proliferation (e.g., c-myc, AP-1, growth factors). Numerous reports have suggested that Ayurvedic plants and their components mediate their effects by modulating several of these recently identified therapeutic targets. However, Ayurvedic medicine requires rediscovery in light of our current knowledge of allopathic (modern) medicine. The focus of this review is to elucidate the Ayurvedic concept of cancer, including its classification, causes, pathogenesis and prevention; surgical removal of tumours; herbal remedies; dietary modifications; and spiritual treatments.

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]

Evidence that TNF-TNFR1-TRADD-TRAF2-RIP-TAK1-IKK pathway mediates constitutive NF-κB activation and proliferation in human head and neck squamous cell carcinoma

Constitutively activated nuclear factor-κB (NF-κB) has been associated with a variety of aggressive tumor types, including head and neck squamous cell carcinoma (HNSCC); however, the mechanism of its activation is not fully understood. Therefore, we investigated the molecular pathway that mediates constitutive activation of NF-κB in a series of HNSCC cell lines. We confirmed that NF-κB was constitutively active in all HNSCC cell lines (FaDu, LICR-LON-HN5 and SCC4) examined as indicated by DNA binding, immunocytochemical localization of p65, by NF-κB-dependent reporter gene expression and its inhibition by dominant-negative (DN)-inhibitory subunit of NF-κB (IκBα), the natural inhibitor of NF-κB. Constitutive NF-κB activation in HNSCC was found to be due to constitutive activation of IκBα kinase (IKK); and this correlated with constitutive expression of phosphorylated forms of IκBα and p65 proteins. All HNSCC showed the expression of p50, p52, p100 and receptor-interacting protein; all linked with NF-κB activation. The expression of constitutively active NF-κB in HNSCC is mediated through the tumor necrosis factor (TNF) signaling pathway, as NF-κB reporter activity was inhibited by DN-TNF receptor-associated death domain (TRADD), DN-TNF receptor-associated factor (TRAF)2, DN-receptor-interacting protein (RIP), DN-transforming growth factor-β-activated kinase 1 (TAK1), DN-κ-Ras, DN-AKT and DN-IKK but not by DN-TRAF5 or DN-TRAF6. Constitutive NF-κB activation was also associated with the autocrine expression of TNF, TNF receptors and receptor-activator of NF-κB and its ligand in HNSCC cells but not interleukin (IL)-1β. All HNSCC cell lines expressed IL-6, a NF-κB-regulated gene product. Furthermore, treatment of HNSCC cells with anti-TNF antibody downregulated constitutively active NF-κB, and this was associated with inhibition of IL-6 expression and cell proliferation. Our results clearly demonstrate that constitutive activation of NF-κB is mediated through the TRADD-TRAF2-RIP-TAK1-IKK pathway, making TNF a novel target in the treatment of head and neck cancer.

Acetyl-11-Keto-β-Boswellic Acid Potentiates Apoptosis, Inhibits Invasion, and Abolishes Osteoclastogenesis by Suppressing NF-κB and NF-κB-Regulated Gene Expression

Acetyl-11-keto-β-boswellic acid (AKBA), a component of an Ayurvedic therapeutic plant Boswellia serrata, is a pentacyclic terpenoid active against a large number of inflammatory diseases, including cancer, arthritis, chronic colitis, ulcerative colitis, Crohn’s disease, and bronchial asthma, but the mechanism is poorly understood. We found that AKBA potentiated the apoptosis induced by TNF and chemotherapeutic agents, suppressed TNF-induced invasion, and inhibited receptor activator of NF-κB ligand-induced osteoclastogenesis, all of which are known to require NF-κB activation. These observations corresponded with the down-regulation of the expression of NF-κB-regulated antiapoptotic, proliferative, and angiogenic gene products. As examined by DNA binding, AKBA suppressed both inducible and constitutive NF-κB activation in tumor cells. It also abrogated NF-κB activation induced by TNF, IL-1β, okadaic acid, doxorubicin, LPS, H2O2, PMA, and cigarette smoke. AKBA did not directly affect the binding of NF-κB to the DNA but inhibited sequentially the TNF-induced activation of IκBα kinase (IKK), IκBα phosphorylation, IκBα ubiquitination, IκBα degradation, p65 phosphorylation, and p65 nuclear translocation. AKBA also did not directly modulate IKK activity but suppressed the activation of IKK through inhibition of Akt. Furthermore, AKBA inhibited the NF-κB-dependent reporter gene expression activated by TNFR type 1, TNFR-associated death domain protein, TNFR-associated factor 2, NF-κB-inducing kinase, and IKK, but not that activated by the p65 subunit of NF-κB. Overall, our results indicated that AKBA enhances apoptosis induced by cytokines and chemotherapeutic agents, inhibits invasion, and suppresses osteoclastogenesis through inhibition of NF-κB-regulated gene expression.

From Ancient Medicine to Modern Medicine: Ayurvedic Concepts of Health and Their Role in Inflammation and Cancer

Recent statistics indicate that the overall cancer incidence in the United States, in spite of billions of dollars spent on research each year, has not changed significantly in the last half-century. Cancers of the prostate, breast, lung, and colon, although most common in the Western world, are least common in the Eastern world. Allopathic medicine commonly practiced currently is only 100 years old. Although traditional medicine has been around for thousands of years, no integration exists between it and allopathic medicine. Ayurveda, the science of long life and one of the most ancient medical systems still practiced on the Indian subcontinent, can be used in combination with modern medicine to provide better treatment of cancer. This review focuses on the ayurvedic concept of the causes of cancer and its linkage with inflammation, diagnosis, prevention, and treatment. How ayurvedic medicine can be integrated with allopathic medicine is also discussed in this review.

Suberoylanilide hydroxamic acid potentiates apoptosis, inhibits invasion, and abolishes osteoclastogenesis by suppressing nuclear factor-κB activation

Because of its ability to suppress tumor cell proliferation, angiogenesis, and inflammation, the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) is currently in clinical trials. How SAHA mediates its effects is poorly understood. We found that in several human cancer cell lines, SAHA potentiated the apoptosis induced by tumor necrosis factor (TNF) and chemotherapeutic agents and inhibited TNF-induced invasion and receptor activator of NF-κB ligand-induced osteoclastogenesis, all of which are known to require NF-κB activation. These observations corresponded with the down-regulation of the expression of anti-apoptotic (IAP1, IAP2, X chromosome-linked IAP, Bcl-2, Bcl-xL, TRAF1, FLIP, and survivin), proliferative (cyclin D1, cyclooxygenase 2, and c-Myc), and angiogenic (ICAM-1, matrix metalloproteinase-9, and vascular endothelial growth factor) gene products. Because several of these genes are regulated by NF-κB, we postulated that SAHA mediates its effects by modulating NF-κB and found that SAHA suppressed NF-κB activation induced by TNF, IL-1β, okadaic acid, doxorubicin, lipopolysaccharide, H2O2, phorbol myristate acetate, and cigarette smoke; the suppression was not cell type-specific because both inducible and constitutive NF-κB activation was inhibited. We also found that SAHA had no effect on direct binding of NF-κB to the DNA but inhibited sequentially the TNF-induced activation of IκBα kinase, IκBα phosphorylation, IκBα ubiquitination, IκBα degradation, p65 phosphorylation, and p65 nuclear translocation. Furthermore, SAHA inhibited the NF-κB-dependent reporter gene expression activated by TNF, TNFR1, TRADD, TRAF2, NF-κB-inducing kinase, IκBα kinase, and the p65 subunit of NF-κB. Overall, our results indicated that NF-κB and NF-κB-regulated gene expression inhibited by SAHA can enhance apoptosis and inhibit invasion and osteoclastogenesis.

Identification of a Novel Blocker of IκBα Kinase That Enhances Cellular Apoptosis and Inhibits Cellular Invasion through Suppression of NF-κB-Regulated Gene Products

1′-Acetoxychavicol acetate (ACA), extracted from rhizomes of the commonly used ethno-medicinal plant Languas galanga, has been found to suppress chemical- and virus-induced tumor initiation and promotion through a poorly understood mechanism. Because several genes that regulate cellular proliferation, carcinogenesis, metastasis, and survival are regulated by activation of the transcription factor NF-κB, we postulated that ACA might mediate its activity through modulation of NF-κB activation. For this report, we investigated the effect of ACA on NF-κB and NF-κB-regulated gene expression activated by various carcinogens. We found that ACA suppressed NF-κB activation induced by a wide variety of inflammatory and carcinogenic agents, including TNF, IL-1β, PMA, LPS, H2O2, doxorubicin, and cigarette smoke condensate. Suppression was not cell type specific, because both inducible and constitutive NF-κB activations were blocked by ACA. ACA did not interfere with the binding of NF-κB to the DNA, but, rather, inhibited IκBα kinase activation, IκBα phosphorylation, IκBα degradation, p65 phosphorylation, and subsequent p65 nuclear translocation. ACA also inhibited NF-κB-dependent reporter gene expression activated by TNF, TNFR1, TNFR-associated death domain protein, TNFR-associated factor-2, and IκBα kinase, but not that activated by p65. Consequently, ACA suppressed the expression of TNF-induced NF-κB-regulated proliferative (e.g., cyclin D1 and c-Myc), antiapoptotic (survivin, inhibitor of apoptosis protein-1 (IAP1), IAP2, X-chromosome-linked IAP, Bcl-2, Bcl-xL, Bfl-1/A1, and FLIP), and metastatic (cyclooxygenase-2, ICAM-1, vascular endothelial growth factor, and matrix metalloprotease-9) gene products. ACA also enhanced the apoptosis induced by TNF and chemotherapeutic agents and suppressed invasion. Overall, our results indicate that ACA inhibits activation of NF-κB and NF-κB-regulated gene expression, which may explain the ability of ACA to enhance apoptosis and inhibit invasion.