Phytochemical inhibition of interleukin-4-activated Stat6 and expression of VCAM-1

Parthenolide as Cooperating Agent for Anti-Cancer Treatment of Various Malignancies

Primary and acquired resistance of cancer to therapy is often associated with activation of nuclear factor kappa B (NF-κB). Parthenolide (PN) has been shown to inhibit NF-κB signaling and other pro-survival signaling pathways, induce apoptosis and reduce a subpopulation of cancer stem-like cells in several cancers. Multimodal therapies that include PN or its derivatives seem to be promising approaches enhancing sensitivity of cancer cells to therapy and diminishing development of resistance. A number of studies have demonstrated that several drugs with various targets and mechanisms of action can cooperate with PN to eliminate cancer cells or inhibit their proliferation. This review summarizes the current state of knowledge on PN activity and its potential utility as complementary therapy against different cancers.

Xanthium strumarium´s xanthatins induces mitotic arrest and apoptosis in CT26WT colon carcinoma cells

BACKGROUND

Colorectal cancer is one of the most common malignancies worldwide and is associated with high mortality rates. We previously reported that Xanthium strumarium L. induces mitotic arrest in proliferating cells, a process mediated by xanthatins.

HYPOTHESIS/AIM

The aim of this work is to study if xanthatins, isolated from X. strumarium total extract, affect the proliferative capacity of CT26WT colon cancer cells and, in consequence, if tumor growth and proliferation of (lung) metastatic sites can also be arrested in vivo.

STUDY DESIGN

This study consisted of both in vitro and in vivo experiments involving the CT26WT cell line and a subcutaneous mouse model of colon cancer. In vitro cell cycle progression, in vivo tumoral growth and anti-metastatic activity were analyzed to investigate whether xanthatins of X. strumarium induce mitotic arrest in proliferating colorectal carcinoma.

RESULTS

Our in vitro results show that X. strumarium, mediated by xanthatins, induces G₂/M arrest and impair anaphase entrance. This leads to a significant induction of apoptotic and necrotic in CT26WT cells, demonstrating their significant anti-proliferative activity through interfering with the mitotic apparatus. Furthermore, our in vivoresults reveal that X. strumarium inhibits both tumor growth and metastasis progression.

CONCLUSION

X. strumarium antitumor activities are mainly mediated by xanthatins through inhibition of tumor growth and metastasis, inducing mitotic arrest and apoptosis in colon carcinoma cells. These findings further confirm the therapeutic potential of X. strumarium in colorectal cancer.

Dietary phytochemicals alter epigenetic events and signaling pathways for inhibition of metastasis cascade: phytoblockers of metastasis cascade

Cancer metastasis is a multistep process in which a cancer cell spreads from the site of the primary lesion, passes through the circulatory system, and establishes a secondary tumor at a new nonadjacent organ or part. Inhibition of cancer progression by dietary phytochemicals (DPs) offers significant promise for reducing the incidence and mortality of cancer. Consumption of DPs in the diet has been linked to a decrease in the rate of metastatic cancer in a number of preclinical animal models and human epidemiological studies. DPs have been reported to modulate the numerous biological events including epigenetic events (noncoding micro-RNAs, histone modification, and DNA methylation) and multiple signaling transduction pathways (Wnt/β-catenin, Notch, Sonic hedgehog, COX-2, EGFR, MAPK-ERK, JAK-STAT, Akt/PI3K/mTOR, NF-κB, AP-1, etc.), which can play a key role in regulation of metastasis cascade. Extensive studies have also been performed to determine the molecular mechanisms underlying antimetastatic activity of DPs, with results indicating that these DPs have significant inhibitory activity at nearly every step of the metastatic cascade. DPs have anticancer effects by inducing apoptosis and by inhibiting cell growth, migration, invasion, and angiogenesis. Growing evidence has also shown that these natural agents potentiate the efficacy of chemotherapy and radiotherapy through the regulation of multiple signaling pathways. In this review, we discuss the variety of molecular mechanisms by which DPs regulate metastatic cascade and highlight the potentials of these DPs as promising therapeutic inhibitors of cancer.

FRNK negatively regulates IL-4-mediated inflammation

Focal adhesion kinase (FAK)-related nonkinase (PTK2 isoform 6 in humans, hereafter referred to as FRNK) is a cytoskeletal regulatory protein that has recently been shown to dampen lung fibrosis, yet its role in inflammation is unknown. Here, we show for the first time that expression of FRNK negatively regulates IL-4-mediated inflammation in a human model of eosinophil recruitment. Mechanistically, FRNK blocks eosinophil accumulation, firm adhesion and transmigration by preventing transcription and protein expression of VCAM-1 and CCL26. IL-4 activates STAT6 to induce VCAM-1 and CCL26 transcription. We now show that IL-4 also increases GATA6 to induce VCAM-1 expression. FRNK blocks IL-4-induced GATA6 transcription but has little effect on GATA6 protein expression and no effect on STAT6 activation. FRNK can block FAK or Pyk2 signaling and we, thus, downregulated these proteins using siRNA to determine whether signaling from either protein is involved in the regulation of VCAM-1 and CCL26. Knockdown of FAK, Pyk2 or both had no effect on VCAM-1 or CCL26 expression, which suggests that FRNK acts independently of FAK and Pyk2 signaling. Finally, we found that IL-4 induces the late expression of endogenous FRNK. In summary, FRNK represents a novel mechanism to negatively regulate IL-4-mediated inflammation.

Natural and synthetic α-methylenelactones and α-methylenelactams with anticancer potential

α-Methylene-γ- and δ-lactones, as well as α-methylene-γ- and δ-lactams, are plant-derived compounds often used in traditional medicine for the treatment of inflammatory diseases. In recent years, the anticancer properties of these compounds and the molecular mechanisms of their action have been studied extensively. In the search for modern anticancer drugs, various synthetic analogs of α-methylene-γ- and δ-lactones and lactams have been synthesized and tested for their cytotoxic activity. In this review, we give a brief description of the occurrence and biological activity of such compounds isolated from plants and their diverse synthetic analogs.

Genome-wide approaches reveal functional interleukin-4-inducible STAT6 binding to the vascular cell adhesion molecule 1 promoter

Endothelial cell activation and dysfunction underlie many vascular disorders, including atherosclerosis and inflammation. Here, we show that interleukin-4 (IL-4) markedly induced vascular cell adhesion molecule 1 (VCAM-1), both in cultured endothelial cells and in the intact endothelium in mice. Combined treatment with IL-4 and tumor necrosis factor alpha (TNF-α) resulted in further, sustained induction of VCAM-1 expression. IL-4-mediated induction of VCAM-1 and secondary monocyte adhesion was predominantly regulated by the transcription factor STAT6. Genome-wide survey of IL-4-mediated STAT6 binding from sequential chromatin-immunoprecipitation with deep sequencing (chromatin immunoprecipitation sequencing [ChIP-seq]) in endothelial cells revealed regions of transient and sustained transcription factor binding. Through the combination of DNA microarrays and ChIP-seq at the same time points, the majority of IL-4-responsive genes were shown to be STAT6 dependent and associated with direct STAT6 binding to their promoter. IL-4-mediated stable binding of STAT6 led to sustained target gene expression. Moreover, our strategy led to the identification of a novel functionally important STAT6 binding site within 16 kb upstream of the VCAM-1 gene. Taken together, these findings support a critical role for STAT6 in mediating IL-4 signal transduction in endothelial cells. Identification of a novel IL-4-mediated VCAM-1 enhancer may provide a foundation for targeted therapy in vascular disease.

Toxoplasma rhoptry protein 16 (ROP16) subverts host function by direct tyrosine phosphorylation of STAT6

The obligate intracellular parasite, Toxoplasma gondii, modulates host immunity in a variety of highly specific ways. Previous work revealed a polymorphic, injected parasite factor, ROP16, to be a key virulence determinant and regulator of host cell transcription. These properties were shown to be partially mediated by dysregulation of the host transcription factors STAT3 and STAT6, but the molecular mechanisms underlying this phenotype were unclear. Here, we use a Type I Toxoplasma strain deficient in ROP16 to show that ROP16 induces not only sustained activation but also an extremely rapid (within 1 min) initial activation of STAT6. Using recombinant wild-type and kinase-deficient ROP16, we demonstrate in vitro that ROP16 has intrinsic tyrosine kinase activity and is capable of directly phosphorylating the key tyrosine residue for STAT6 activation, Tyr(641). Furthermore, ROP16 co-immunoprecipitates with STAT6 from infected cells. Taken together, these data strongly suggest that STAT6 is a direct substrate for ROP16 in vivo.

Gastrin induces the interaction between human mononuclear leukocytes and endothelial cells through the endothelial expression of P-selectin and VCAM-1

Gastric mucosal inflammation is frequently associated with hypergastrinemia, and a correlation exists between the level of gastrin and degree of gastritis. We have previously observed that gastrin promotes leukocyte-endothelial interactions and contributes to Helicobacter-induced inflammation in the rat mesentery. In the present study, we aimed to evaluate a possible proinflammatory activity of gastrin in humans. The interaction between human leukocytes [U-937 cells, peripheral blood polymorphonuclear (PMN), and peripheral blood mononuclear (PBMC) cells] and human umbilical vein endothelial cells (HUVEC) was analyzed in static and dynamic conditions. The endothelial expression of adhesion molecules [P-selectin, E-selectin, intercellular adhesion molecule-1, vascular cell adhesion molecule (VCAM)-1] was analyzed by flow cytometry and fluorescent microscopy screening. Gastrin increased the static adhesion of U-937 cells to HUVEC (1 h; 10(-9) M: 122 +/- 9%; 10(-8) M: 143 +/- 17%; 10(-7) M: 162 +/- 14% vs. control, all P < 0.05). Incubation of HUVEC with gastrin (4 h) also increased PBMC rolling (vehicle: 63 +/- 12; 10(-9) M: 109 +/- 29; 10(-8) M: 141 +/- 24; 10(-7) M: 261 +/- 16 leukocytes/min, P < 0.05) and adhesion (vehicle: 3 +/- 2, 10(-9) M: 11 +/- 4, 10(-8) M: 17 +/- 5, 10(-7) M: 15 +/- 5 leukocytes/mm(2), all P < 0.05) in the parallel-plate flow chamber. Treatment of PBMC with gastrin had no effects. The cholecystokinin (CCK)-2 receptor antagonist (L-365,260, 10(-7) M) prevented the effects of gastrin. P-selectin and VCAM-1 expression were enhanced by gastrin, and neutralizing antibodies against these molecules prevented PBMC rolling and adhesion. Gastrin did not affect the interactions between HUVEC and PMN. Gastrin induces interactions between human mononuclear leukocytes and endothelial cells through the activation of CCK-2 receptors and the enhancement of endothelial P-selectin and VCAM-1.

Molecular basis of parthenolide-dependent proapoptotic activity in cancer cells

This review outlines the molecular events that accompany the anti-tumor action of parthenolide (PN). Parthenolide (PN) is naturally derived compound, isolated from plant Tanacetum parthenium. PN has been previously shown to withdraw cells from cell cycle or to promote cell differentiation, and finally to induce programmed cell death. Recent advances in molecular biology indicate that this sesquiterpene lactone might evoke the above-mentioned effects by indirect action on genes. PN was shown to inhibit NF-kappaB- and STATs-mediated antiapoptotic gene transcription. On one hand, the proapoptotic activity of PN includes stimulation of intrinsic apoptotic pathway with the higher level of intracellular ROS and modifications of Bcl-2 family proteins (conformational changes of Bak and Bax, Bid cleavage). On the other hand, PN amplifies the apoptotic signal through the sensitization of cancer cells to extrinsic apoptosis, induced by TNF-alpha. These effects are specific to tumor cells. Unique properties of PN make this agent a promising metabolic inhibitor to retard tumorigenesis and to suppress tumor growth.

IL-4-stimulated NF-kappaB activity is required for Stat6 DNA binding

IL-4 is a critical cytokine in the regulation of immune responses. In B lymphocytes, IL-4 signaling promotes the Stat6-dependent cell surface expression of several proteins including MHC Class II and CD86. However, the requirement for other transcription factors in IL-4-induced B cell gene expression has not been studied extensively. Here, we show that IL-4 induces NF-kappaB p100 processing to NF-kappaB p52 in B cells but not in T cells or macrophages. IL-4 induced NF-kappaB p52 production requires PI-3K activity and correlates with IkappaB kinase phosphorylation and TNF receptor-associated factor 3 degradation. Blocking NF-kappaB activity eliminates IL-4-stimulated gene expression in B cells by reducing IL-4-induced DNA binding but not phosphorylation or nuclear localization of Stat6. These results describe a novel role for NF-kappaB in IL-4-induced signaling and gene expression.

TH1-dominant granulomatous pathology does not inhibit fibrosis or cause lethality during murine schistosomiasis

Schistosoma mansoni egg-induced inflammation is accompanied by TH2 cell polarization and development of fibrotic granulomas in host tissue. The interleukin (IL)-4 receptor alpha (IL-4Ralpha), which mediates IL-4 and IL-13 signaling, is essential for granulomatous pathology through a putative CD4+ T-cell-dependent mechanism. In this study, we asked whether CD4+ T-cell-specific IL-4Ralpha-deficient mice (Lck(Cre)IL-4Ralpha(-/lox)) developed granulomas and egg-driven collagen production. Although eosinophilia and goblet cell hyperplasia were impaired in Lck(Cre)IL-4Ralpha(-/lox) mice, there was no reduction in size or collagen content of lung and liver granulomas. The lack of CD4+ T-cell IL-4Ralpha expression caused significant increases in interferon-gamma-producing cells, inducible nitric-oxide synthetase production, and hepatic damage, compared with similarly infected wild-type mice. Interestingly, this TH1-associated liver injury did not lead to premature mortality in this strain. Instead, lower levels of serum endotoxin in Lck(Cre)IL-4Ralpha(-/lox) mice suggest that intestinal barrier function may be the dominant factor for survival during natural infection.

Molecular targets of dietary agents for prevention and therapy of cancer

While fruits and vegetables are recommended for prevention of cancer and other diseases, their active ingredients (at the molecular level) and their mechanisms of action less well understood. Extensive research during the last half century has identified various molecular targets that can potentially be used not only for the prevention of cancer but also for treatment. However, lack of success with targeted monotherapy resulting from bypass mechanisms has forced researchers to employ either combination therapy or agents that interfere with multiple cell-signaling pathways. In this review, we present evidence that numerous agents identified from fruits and vegetables can interfere with several cell-signaling pathways. The agents include curcumin (turmeric), resveratrol (red grapes, peanuts and berries), genistein (soybean), diallyl sulfide (allium), S-allyl cysteine (allium), allicin (garlic), lycopene (tomato), capsaicin (red chilli), diosgenin (fenugreek), 6-gingerol (ginger), ellagic acid (pomegranate), ursolic acid (apple, pears, prunes), silymarin (milk thistle), anethol (anise, camphor, and fennel), catechins (green tea), eugenol (cloves), indole-3-carbinol (cruciferous vegetables), limonene (citrus fruits), beta carotene (carrots), and dietary fiber. For instance, the cell-signaling pathways inhibited by curcumin alone include NF-kappaB, AP-1, STAT3, Akt, Bcl-2, Bcl-X(L), caspases, PARP, IKK, EGFR, HER2, JNK, MAPK, COX2, and 5-LOX. The active principle identified in fruit and vegetables and the molecular targets modulated may be the basis for how these dietary agents not only prevent but also treat cancer and other diseases. This work reaffirms what Hippocrates said 25 centuries ago, let food be thy medicine and medicine be thy food.

Selective inhibition of NF-?B in dendritic cells by the NEMO-binding domain peptide blocks maturation and prevents T cell proliferation and polarization

Dendritic cells (DC) are the only antigen-presenting cells for naive T cells and, therefore, they are crucial players in the initiation of immune responses. Because DC maturation and cytokine production are NF-kappaB dependent, we hypothesized that blocking NF-kappaB activity in DC by selectively targeting the inhibitor of kappaB (IkappaB) kinase (IKK) complex using the novel NF-kappaB inhibitor NEMO-binding domain (NBD) peptide could inhibit DC maturation and other functional characteristics, resulting in modulation of the immune response. We used human monocyte-derived DC to test the biological effects of the NBD peptide in vitro. NF-kappaB inhibition by the NBD peptide resulted in blockade of IKK-mediated IkappaBalpha phosphorylation and subsequent nuclear translocation and DNA binding of NF-kappaB p65 in DC. In addition, IL-6, IL-12, and TNF-alpha production was dose-dependently blocked and NBD peptide treatment also led to a strong reduction of LPS-induced maturation. Functional analysis of these DC showed marked inhibition of T cell proliferation in the allogeneic mixed lymphocyte reaction, accompanied by less Th1 and Th2 polarization. The current study reveals for the first time the unique properties of this novel, highly specific NF-kappaB inhibitor in DC. Also, these data indicate that the NBD peptide could be used as an elegant tool in DC based immunotherapy for unwanted cellular immune responses.

IL-4 and IL-13 induce SOCS-1 gene expression in A549 cells by three functional STAT6-binding motifs located upstream of the transcription initiation site

Proteins of the suppressors of cytokine signaling (SOCS) family have important functions as negative regulators of cytokine signaling. We show here that SOCS-1 expression can be induced in the human epithelial lung cell line A549 by IL-4 and IL-13. Analysis of reporter gene constructs under control of the SOCS-1 promoter provides evidence that IL-4- and IL-13-induced up-regulation is dependent on three IFN-gamma-activated sequence motifs of the sequence TTC(N)(4)GAA, which is known for binding STAT6. The three motifs are situated close to each other approximately 600 bp upstream of the transcriptional initiation site. When mutations were inserted into all three IFN-gamma-activated sequence motifs at the same time, IL-4-IL-13-induced luciferase activity was abrogated. With single and double mutants, promoter activity was diminished in comparison with the wild-type promoter. STAT6 is therefore required for IL-4-IL-13-dependent SOCS-1 expression in A549 cells, and the three identified binding motifs cooperate to induce maximal transcription. EMSAs conducted with nuclear extracts of IL-4- and IL-13-stimulated A549 cells showed that STAT6 was able to bind to each of the three binding motifs. Finally, cotransfection of a SOCS-1 expression vector inhibited activation of SOCS-1 promoter luciferase constructs. Thus, SOCS-1 is able to autoregulate its expression via a negative feedback loop.

Influence of helenanolide-type sesquiterpene lactones on gene transcription profiles in Jurkat T cells and human peripheral blood cells: anti-inflammatory and cytotoxic effects

Sesquiterpene lactones (SLs) are known to have potent anti-inflammatory and cytotoxic properties. So far, the anti-inflammatory effects have mainly been attributed to their inhibition of DNA-binding of the transcription factor NF-kappa B (p65), which is a pivotal regulator of the cellular immune response. Since NF-kappa B is involved in the transcriptional control of several pro-inflammatory and regulatory genes, we investigated the effects of one bifunctional NF-kappa B (p65) inhibiting and two monofunctional NF-kappa B (p65) inactive helenanolide-type SLs on PMA and LPS-induced mRNA expression in CD4(+) Jurkat T and human peripheral blood mononuclear cells (PBMCs) with reverse transcription real-time PCR (RT-rt-PCR). The monofunctional SLs 11 alpha,13-dihydrohelenalin acetate (DHAc) and chamissonolide significantly reduced mitogen-induced cytokine and iNOS mRNA levels in PBMCs and Jurkat T cells at low micromolar concentrations. DHAc also showed significant effects on the gene expression of the house-keeping genes GAP-DH and beta-actin, as well as on NF-ATc, p65, I-kappa B alpha, bcl-2, and cyclin D1. The bifunctional NF-kappa B inhibitor helenalin not only effectively inhibited pro-inflammatory gene expression, but also strongly down-regulated all investigated mRNA levels in a time-dependent manner. Flow cytometry and caspase-8 and -3 assays revealed that helenalin strongly and DHAc moderately induced apoptosis in Jurkat T cells, whereas chamissonolide caused cytoprotective effects. In PBMCs, DHAc and chamissonolide did not inhibit NF-kappa B (p65) DNA-binding at concentrations effective on the transcriptome. Thus, it can be concluded that the biological effects of SLs are not only due to NF-kappa B inhibition, but must be coupled to other mechanisms.

The anti-inflammatory sesquiterpene lactone parthenolide suppresses IL-4 gene expression in peripheral blood T

Sesquiterpene lactones (SL) derived from Mexican India medicinal plants and parthenolide, the major SL from European feverfew, have raised considerable interest because of their anti-inflammatory and complex pharmacological action. Interleukin-4 (IL-4) is a key cytokine that influences the development of T helper 2 cells and plays an important role in the pathogenesis of allergic diseases. We show here that the anti-inflammatory parthenolide suppresses IL-4 expression at the mRNA and the protein levels in a dose-dependent manner. We demonstrate that parthenolide blocks NF-kappaB binding to two important IL-4 promoter regulatory elements and suppresses promoter activity upon T cell activation. Differences regarding the effects of parthenolide on expression levels of IL-4, IL-2 and IFN-gamma were observed. Parthenolide (2.5 microM) could completely suppress IL-4 protein levels secreted in anti-CD3/CD28-stimulated peripheral blood T cells from allergic and normal donors. Complete inhibition of IL-2 and IFN-gamma requires higher doses of parthenolide. So far, drugs directed against IL-4 expression have not been described. This finding raises the potential to develop parthenolide to treat IL-4-mediated allergic-like inflammation.