NF-kappaB-dependency and consequent regulation of IL-8 in echinomycin-induced apoptosis of HT-29 colon cancer cells.

The present study was to see whether echinomycin-induced apoptosis would be NF-kappaB-dependent and if so, whether echinomycin would activate or inhibit NF-kappaB as well as resultant chemokine IL-8 expression. In HT-29 cells echinomycin activated NF-kappaB in time-dependent manner. EMSA in the presence of antibodies specific for p50 and p65 subunits indicated that echinomycin-induces the translocation of p50-p65 heterodimeric subunits of NF-kappaB. Levels of IkappaB were detected at initial echinomycin treatment and thereafter decreased, faintly seen after a 6h treatment. In contrast p-IkappaB levels were clearly detected throughout 6-24h of echinomycin treatment, albeit initially fainted. To clarify the role of NF-kappaB on IL-8 expression in echinomycin-mediated apoptosis of HT-29 cells, ELISA plus RT-PCR clearly showed that IL-8 production is inducible by echinomycin treatment. Using a specific inhibitor, IL-8 regulation at echinomycin treatment in HT-29 cells occurred via both caspase-3 and NF-kappaB-dependent signal pathway. To confirm whether two different pathways (NF-kappaB and caspase) would be coupled, only NF-kappaB inhibitor (PDTC) and caspase-3 specific inhibitor (Z-DEVD-FMK) together significantly attenuated echinomycin-initiated apoptosis of HT-29 cells, pretreatment of HT-29 cells with PDTC rarely affected echinomycin-induced caspase-3 activation. So echinomycin-induced apoptosis in HT-29 cells occurs via NF-kappaB activation independent of caspase-3 activation modulating the resultant-linked key chemokine IL-8 expression and echinomycin-induced apoptosis is NF-kappaB-dependant and directly related to NF-kappaB activation, consequently regulating IL-8 expression.

Cancer immunotherapeutic effects of novel CpG ODN in murine tumor model.

While CpG oligodeoxynucleotides (ODN) are excellent candidates for cancer immunotherapeutics, the numbers of usable CpG ODNs are limited in current clinical settings. To resolve this, we investigated whether novel CpG ODN (KSK-CpG) would be an effective immunotherapeutic in a murine tumor model by affecting in vivo and in vitro parameters, such as survival span, the number of tumor nodules, natural killer (NK) cell and cytotoxic T lymphocyte (CTL) activity and interleukin (IL)-6 or IL-12 cytokine release in splenocytes. We found that KSK-CpG was effective in the murine cancer model by way of prolonging survival span, reducing the number of tumor nodules, augmenting NK cell and CTL cytotoxicity, as well as evoking IL-6 and IL-12 cytokine release in splenocytes. Collectively, these data demonstrate that KSK-CpG is active against the highly malignant B16BL6 and EL4 tumor mouse model via innate immune augmentation.

Dependence on p38 MAPK signalling in the up-regulation of TLR2, TLR4 and TLR9 gene expression in Trichomonas vaginalis-treated HeLa cells.

Toll-like receptors (TLRs) are pattern recognition receptors (PRRs) that recognize conserved pathogen-associated molecular patterns (PAMPs) synthesized by micro-organisms. Despite the essential requirement for TLRs in prokaryotic infection, the pattern and regulation of TLR gene expression by Trichomonas vaginalis in the mucocutaneous barrier are still unknown. Our hypothesis is that T. vaginalis-infected epithelial cells are major effector cells in the skin barrier. These cells function as a central regulator of TLR gene expression, thus accelerating the process of barrier dysfunction via increased release of chemokines and proinflammatory cytokines. To test this hypothesis, RT-PCR was performed on TLRs, interleukin (IL)-8 and tumour necrosis factor (TNF)-alpha. Stimulation of HeLa cells by T. vaginalis was observed to up-regulate TLR2, 4 and 9 mRNA expression as well as that of IL-8 and TNF-alpha. To further clarify the molecular mechanism of barrier devastation triggered by these up-regulatory stimuli, we examined the profiles of extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-kappaB activation in HeLa cells using specific inhibitors. Interestingly, pretreatment of HeLa cells with the p38 MAPK inhibitor SB203580 demonstrated inhibition of T. vaginalis-induced up-regulation of TLR2, 4, and 9 mRNA expression. By contrast, inhibition of ERK or NF-kappaB activation failed to block T. vaginalis-induced up-regulation of TLR9 mRNA expression or TLR2 and TLR4 mRNA expression, respectively. In addition, pretreatment with SB203580 reduced epithelium-derived IL-8 and TNF-alpha release evoked by T. vaginalis. Our results show that T. vaginalis infection of the mucocutaneous barrier could up-regulate TLR2, 4 and 9 gene expression via the p38 MAPK signalling pathway in epithelial cells; this process then leads to modulation of p38 MAPK-dependent IL-8 and TNF-alpha release from the epithelium.

Molecular signaling cascade in DNA bisintercalator, echinomycin-induced apoptosis of HT-29 cells: evidence of the apoptotic process via activation of the cytochrome c-ERK-caspase-3 pathway.

The DNA-interactive drug, echinomycin, is a potent antitumor agent, which is able to induce apoptosis in a multitude of cancer cell lines. Previously, we showed that echinomycin strongly inhibited the growth of a variety of cancer cell lines, and the activation of mitogen-activated protein kinases (MAPK) in human colon cancer cells (HT-29). However, little information currently exists regarding the details of intracellular signaling pathways such as the MAPK, mitochondrial, and caspase pathways. In order to clarify this issue, we verified the plausible molecular signaling cascade by performing an immunobiochemical apoptosis experiment involving the mitochondrial and caspase pathways. The apoptotic process of HT-29 cells was accompanied by the activation of procaspase-9, -3 and cytochrome c release. Both caspase and MAPK inhibitors were used in the determination of the specific roles of MAPK and caspase in echinomycin-induced apoptosis. ERK (PD98059) or caspase-3-specific (Z-DEVD-FMK) inhibitors were discovered to significantly attenuate echinomycin-induced apoptosis. PD98059 treatment or overexpression of kinase-inactive ERK did not alter the echinomycin-induced cytochrome c release into the cytosol, but did diminish the activation of procaspase-3. Also, Z-DEVD-FMK was found to have no effect on either cytochrome c release or ERK activation. Taken together, these results indicate that cytochrome c release, and the activation of ERK and caspase-3 in the final apoptosis pathway are all relevant factors in echinomycin-induced apoptosis. To our knowledge, this study is the first to delineate the echinomycin's direct detrimental effects on colon cancer cells.

Involvement of MAP kinases in apoptosis of macrophage treated with Trichomonas vaginalis.

A primitive protozoan parasite Trichomonas vaginalis selectively activates the signal transduction pathways in macrophages (RAW264.7). This study evaluated the correlation of these signaling pathways and T. vaginalis-induced cell apoptosis. In macrophages infected with T. vaginalis, apoptosis was assessed on the basis of DNA fragmentation on agarose gel electrophoresis. Infection of macrophages with T. vaginalis induced tyrosine phosphorylation of several proteins. Infected cells with T. vaginalis were shown to associate with phosphorylation of the extracellular signal-regulated (ERK)1/2 kinase, p38, c-Jun N-terminal kinase (JNK) mitogen-activated protein (MAP) kinases on Western blot analysis. The present finding also demonstrated a link between the ERK1/2, JNK and p38 apoptotic pathways that was modulated by T. vaginalis infection.

Echinomycin and a novel analogue induce apoptosis of HT-29 cells via the activation of MAP kinases pathway.

Echinomycin, in typical DNA minor groove binder, had comparable efficacy compared to 5-FU in the phase II trail of colon cancer treatment. To improve echinomycin's drawback (hydrophobicity, toxicity), we synthesized the YK-2000 series (echinomycin analogues). Among these, YK-2000 had the best in vitro cytotoxicity on six different human solid cancer cell lines. Echinomycin and YK-2000 were enabled to induce the apoptosis on the HT-29 colorectal cancer cell line. The hypothesis that apoptosis in the HT-29 cell was triggered by echinomycin and YK-2000 were supported through DNA laddering, poly-(ADP-ribose) polymerase (PARP) cleavage, and flow cytometric analysis. In order to explore the signaling pathway of echinomycin and YK-2000, we examined the phosphorylation of extracellular signal-regulated kinase1/2 (ERK1/2), stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), and p38 MAP kinase. However, what the mechanism of cancer cell death would be induced by echinomycin and YK-2000 is unknown. Here, we present some evidence that one of the major apoptotic signaling pathways induced by echinomycin and YK-2000 is possibly the MAP kinases pathway in HT-29 human colon cancer cells.

Synthesis and biological activity of new quinoxaline antibiotics of echinomycin analogues.

Novel quinoxaline antibiotics having the methylenedithioether bridge as an analogue of echinomycin have been synthesized by insertion of methylene moiety between -S-S- bond. The compound 1a shows remarkable cytotoxicities against human tumor various cell lines, and is active VRE (vancomycin-resistant enterococci) within MIC range 0.5-8 microg/mL. According to the eukaryotic or prokaryotic data, 1a might be a first analogue to replace echinomycin.