Dehydroxymethylepoxyquinomicin Research Articles

Significance of Autologous Interleukin‐6 Production in the HA22T/VGH Cell Model of Hepatocellular Carcinoma

Cancer cells may often support their own growth, survival, and drug resistance by autocrine/paracrine loops based on the production of different factors; results from us and others have shown that similar interleukin-6 (IL-6)-related loops are operative in multiple myeloma and prostate or renal cancer. Because this aspect has not been investigated in detail for hepatocellular carcinoma (HCC), we have examined it in HA22T/VGH cells. These differ from other primary liver cancer cell lines (that is, HepG2, HuH-6, and HuH-7) in that enzyme-linked immunosorbent assay (ELISA) showed the HA22T/VGH cells to secrete remarkable amounts of IL-6 (16.8 ng/10(6) cells/24 h); this production, due to constitutive activation of NF-kappaB, is inhibited by agents like curcumin and dehydroxymethylepoxyquinomicin (DHMEQ), which interfere with the transcription factor. Flow cytometry, ELISA, mRNA, and Western blotting analyses were performed to characterize the status of the IL-6 receptor in HA22T/VGH cells. Two transmembrane glycoproteins that form the functional IL-6 receptor have been identified: the ligand-binding gp80 and the signal-transducer gp130. Soluble forms of gp80 also trigger membrane gp130 signaling when complexed with IL-6, while soluble forms of gp130 inhibit the same process. Our results showed that HA22T/VGH cells express gp130 at their surface, but release only traces of its soluble form. For gp80, the cells produced the mRNAs of both its membrane and soluble form. However, in immunoblotting they exhibited a very faint content of the same subunit, which, in addition, was neither expressed at the cell surface nor secreted. In MTT assays, incubation with a neutralizing anti-IL-6 antibody for up to 7 days did not affect the growth of HA22T/VGH cells. Also, other specific anti-IL-6 approaches (siRNA or AODN) failed to produce this result. In conclusion, autostimulatory loops mediated by IL-6 are less likely to occur in HCC than in other kinds of cancer. However, since release of IL-6 is frequent in HCC, especially in its more advanced stages, the use of agents like curcumin or DHMEQ might be beneficial to counteract its adverse systemic effects (e.g., cachexia).

DHMEQ, a novel NF-kB inhibitor, induces apoptosis and cell-cycle arrest in human hepatoma cells

Several reports have indicated that nuclear factor-kappaB (NF-kappaB) is constitutively activated in a variety of cancer cells including hepatoma cells and plays a key role in their growth and survival. Dehydroxymethylepoxyquinomicin (DHMEQ) derived from the structure of an antibiotic epoxyquinomicin C is a novel NF-kappaB inhibitor. In the present study, we evaluated the effect of DHMEQ on the NF-kappaB activity in human hepatoma cells, Huh-7, HepG2 and Hep3B, and the anti-tumor effect of DHMEQ on these cells in vitro and in vivo. DHMEQ inhibited the steady-state transcriptional activity of NF-kappaB in all hepatoma cells. DHMEQ blocked the constitutive DNA-binding activity and TNF-alpha-mediated nuclear translocation of NF-kappaB in Huh-7 cells. DHMEQ (5-20 microg/ml) dose-dependently reduced the viable cell number of all hepatoma cells. DHMEQ (20 microg/ml) induced apoptosis in all hepatoma cells, especially in Hep3B cells, and cell-cycle arrest in Huh-7 and HepG2 cells. These effects were accompanied by downregulation of proteins involved in anti-apoptosis (Bcl-xL, XIAP or c-IAP2) and cell-cycle progression (cyclin D1), and induction of proteins involved in pro-apoptosis (Bax) and cell-cycle retardation (p21Waf1/Cip1), although the degree of changes by DHMEQ was different in each hepatoma cell type. Moreover, intraperitoneal administration of DHMEQ (8 mg/kg) significantly repressed the growth of Huh-7 tumor subcutaneously transplanted into BALB/c nu/nu athymic mice. Our results suggest that DHMEQ could qualify as a candidate for a new chemotherapeutic agent against human hepatoma.

Inhibition of macrophage activation and phagocytosis by a novel NF-κB inhibitor, dehydroxymethylepoxyquinomicin

Previously, we designed and synthesized a new NF-κB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ). In the present research we looked into the effect of DHMEQ on the activation of macrophages, especially on the phagocytotic activity of cells of the mouse macrophage-like cell line RAW264.7. DHMEQ inhibited lipopolysaccharide (LPS)-induced NF-κB activation by inhibiting its nuclear translocation from the cytoplasm. It also inhibited the expression of inducible NO synthase (iNOS) and nitric oxide (NO) production induced by LPS and interferon-γ. Using enzyme-linked immunosorbent assays (ELISAs) we showed DHMEQ to inhibit LPS-induced secretion of IL-6, IL-12, interleukin-1β (IL-1β), and TNF-α. Furthermore, DHMEQ also inhibited the phagocytosis of fluorescently labeled Escherichia coli by RAW264.7 cells treated with LPS or IL-1β, thus being the first evidence for the involvement of NF-κB in the regulation of phagocytosis by use of this inhibitor. Deletion of p65 by siRNA also inhibited the phagocytosis. DHMEQ inhibited the LPS-induced but not IL-1β-induced phagocytosis of glass beads, indicating that activation of not only NF-κB but also Toll-like receptor 4 (TLR-4) is essential for the phagocytosis of E. coli. Previously we found that DHMEQ inhibited type 2 collagen-induced rheumatoid arthritis and the growth of various human carcinomas in mice. It is thus likely that inhibition of macrophage activation is involved in the mechanism of these anti-inflammatory and antitumor activities of DHMEQ in mice.

Antitumor effects of the novel NF-κB inhibitor dehydroxymethyl-epoxyquinomicin on human hepatic cancer cells: analysis of synergy with cisplatin and of possible correlation with inhibition of pro-survival genes and IL-6 production

We tested the novel NF-kappaB inhibitor dehydroxymethylepoxyquinomicin (DHMEQ) in the hepatic cancer (HCC) HepG2, HA22T/VGH and HuH-6 cells. The sensitivity to the cell growth inhibitory and apoptotic effects of the agent increased along with the levels of constitutively activated NF-kappaB, which were low in HepG2 and higher in HA22T/VGH and HuH-6. In HA22T/VGH, DHMEQ exhibited synergy with cisplatin. In the same cells, DHMEQ exerted dose-dependent decreases in the nuclear levels of activated NF-kappaB and attenuated NF-kappaB activation by cisplatin. It down-regulated Bcl-XL mRNA in a dose-dependent manner and up-regulated that of Bcl-XS. It also decreased interleukin 6 (IL-6), NAIP and, after 16 h of exposure to the higher concentration tested (10 microg/ml), c-IAP-1 mRNA levels. At 10 microg/ml it caused significant increase in Bax, XIAP, cyclin D1 and beta-catenin mRNAs. The combination of DHMEQ with cisplatin produced unexpected significant decrease in c-IAP-2 and Bcl-XS mRNAs as well as additive decrease (IL-6, NAIP and, after 16 h, Bcl-XL) or increase (XIAP at 8 h) in gene expression. HA22T/VGH produce IL-6; in agreement with the results on mRNA, DHMEQ inhibited such a process. HA22T/VGH lack the IL-6 receptor alpha chain, ruling out that in these cells the antitumor effects of DHMEQ may be attributed to an interference with a growth stimulatory autocrine loop based on IL-6. However, the use of DHMEQ in HCC might be beneficial to contrast the adverse systemic effects of the released cytokine.

Survivin associates with cell proliferation in renal cancer cells: Regulation of survivin expression by insulin-like growth factor-1, interferon-γ and a novel NF-κB inhibitor

Although survivin has been widely recognized as an attractive target for cancer therapy, the exact mechanism regarding the regulation of survivin and its effect on cell proliferation have yet to be clearly defined in renal cell carcinoma (RCC). We investigated herein the association between survivin expression and cell proliferation in a RCC cell line, KU19-20. In KU19-20 cells, cell proliferation and survivin expression were significantly induced by IGF-1, whereas they were inhibited by a novel NF-kappaB inhibitor dehydroxymethyl-epoxyquinomicin (DHMEQ) and IFN-gamma. The combination of DHMEQ and IFN-gamma inhibited cell proliferation synergistically with a pronounced attenuation of survivin expression. Furthermore, treatment with survivin-specific siRNA reduced expression of survivin and significantly inhibited cell proliferation. Survivin expression was thus associated with cell proliferation in KU19-20 cells. The regulation of survivin by IFN-gamma and/or an NF-kappaB inhibitor may therefore be a potential treatment modality for RCC.

DHMEQ, a new NF-κB inhibitor, induces apoptosis and enhances fludarabine effects on chronic lymphocytic leukemia cells

Chronic lymphocytic leukemia (CLL) is a low-grade lymphoid malignancy incurable with conventional modalities of chemotherapy. Strong and constitutive nuclear factor kappa B (NF-kappaB) activation is a characteristic of CLL cells. We examined the effects of a new NF-kappaB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), on CLL cells. Dehydroxymethylepoxyquinomicin completely abrogated constitutive NF-kappaB activity and induced apoptosis of CLL cells. Apoptosis induced by DHMEQ was accompanied by downregulation of NF-kappaB-dependent antiapoptotic genes: c-IAP, Bfl-1, Bcl-X(L) and c-FLIP. Dehydroxymethylepoxyquinomicin also inhibited NF-kappaB induced by CD40 and enhanced fludarabine-mediated apoptosis of CLL cells. Results of this study suggest that inhibition of constitutive and inducible NF-kappaB by DHMEQ in combination with fludarabine is a promising strategy for the treatment of CLL.

Effects of a novel NF-κB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), on growth, apoptosis, gene expression, and chemosensitivity in head and neck squamous cell carcinoma cell lines

Recent studies provide evidence that the constitutive activation of nuclear factor-kappa B, NF-kappaB plays a critical role in enhancing the growth of several types of malignancies, including head and neck squamous cell carcinoma (HNSCC). In this study, we examined the effects of a newly synthesized NF-kappaB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), on growth, induction of apoptosis, gene expression, and chemosensitivity in two HNSCC cell lines (YCU-H891 and KB), which expressed high levels of nuclear NF-kappaB protein. DHMEQ showed strong growth inhibitory effects on these two cell lines, with a 50% cell growth inhibition (IC50) concentration of approximately 20 microg/mL. These growth inhibitory effects were associated with inhibition of the NF-kappaB activity. Treatment with DHMEQ induced apoptosis in a dose-dependent manner accounting, at least in part, for the growth inhibition by DHMEQ. DHMEQ strongly inhibited cyclin D1 and vascular endothelial growth factor (VEGF) promoter activity and decreased the levels of cyclin D1 protein and VEGF mRNA in KB cells. In addition, low concentrations of DHMEQ (1.0 or 5.0 microg/mL) synergistically enhanced the cellular sensitivity of YCU-H and KB cells to cisplatin, which is a key chemotherapeutic agent in the treatment of HNSCC. These results suggest that DHMEQ may be effective when used alone or in combination with other agents in the treatment of HNSCC.

P.433 Epigenetic down-regulation of death-associated protein kinase in hepatocellular carcinoma

In a previous work of ours dehydroxymethyl-epoxyquinomicin (DHMEQ), an inhibitor of NF-κB, was shown to induce apoptosis through Reactive Oxygen Species (ROS) production in hepatoma cells. The present study demonstrated that DHMEQ cooperates with Celecoxib (CLX) to decrease NF-κB DNA binding and to inhibit cell growth and proliferation more effectively than treatment with these single agents alone in the hepatoma cell lines HA22T/VGH and Huh-6. ROS production induced by the DHMEQ–CLX combination in turn generated the expression of genes involved in endoplasmic reticulum (ER) stress and silencing TRB3 mRNA significantly decreased DHMEQ–CLX-induced cell growth inhibition. Moreover, the DHMEQ–CLX combination was associated with induction of PARP cleavage and down-regulation of the anti-apoptotic proteins Bcl-2, Mcl-1 and survivin, as well as activated Akt. CD95 and CD95 ligand expression increased synergistically in the combination treatment, which was reversed in the presence of NAC. Knockdown of CD95 mRNA expression significantly decreased DHMEQ–CLX-induced cell growth inhibition in both cell lines. These data suggest that the DHMEQ–CLX combination kills hepatoma cells via ROS production, ER stress response and the activation of intrinsic and extrinsic apoptotic pathways.

Blocking NF-κB as a Potential Strategy to Treat Adult T-cell Leukemia/Lymphoma.

Adult T-cell leukemia/lymphoma (ATL), a fatal T-cell leukemia/lymphoma resistant to chemotherapy, is caused by human T-cell leukemia/lymphoma virus type I (HTLV-1), occurring even after 50 years of clinical latency from initial transmission. Constitutively activated nuclear factor kappaB (NF-kappaB) appears to be a molecular basis for the aberrant growth and cytokine gene expression observed in ATL cells, thereby serving as an ideal target in the treatment of ATL. Dehydroxymethylepoxyquinomicin (DHMEQ) is a new NF-kappaB inhibitor that is a 5-dehydroxymethyl derivative of epoxyquinomicin C, having a 4-hydroxy-5,6-epoxycyclohexenone structure similar to panepoxydone. This unique compound acts in the translocation of NF-kappaB into the nucleus. Dehydroxymethylepoxyquinomicin inhibits NF-kappaB activation in ATL cells and induces apoptotic cell death. In addition, DHMEQ selectively targets HTLV-1-infected cells in the peripheral blood of virus carriers in vitro, resulting in a decreased number of infected cells. We have concluded that blocking NF-kappaB is a potential strategy for the treatment and prevention of ATL. As a potent NF-kappaB inhibitor, DHMEQ is a promising compound for translating this strategy into clinical medicine.

Enhancement of the caspase-independent apoptotic sensitivity of pancreatic cancer cells by DHMEQ, an NF-κB inhibitor

The effects of the nuclear factor (NF)-kappaB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), combined with tumor necrosis factor (TNF)-alpha were evaluated in PK-8 pancreatic cancer cells. NF-kappaB was activated by TNF-alpha; however, the administration of DHMEQ abrogated its transcriptional activity. The addition of DHMEQ to TNF-alpha markedly induced apoptosis in PK-8 cells with down-regulation of anti-apoptotic c-FLIP and survivin. Combined treatment significantly suppressed cell viability in vitro, and the anti-tumor effect of DHMEQ was also significant in vivo. We investigated the apoptosis signaling pathway involved in these cell killing effects. Truncated Bid was produced by activated caspase-8, and the subsequent depolarization of the mitochondrial membrane potential (Delta Psi m) peaked at 6 h. Then, the activity of caspase-3 was up-regulated 8-fold. Z-VAD-fmk (a pan-caspase inhibitor) perfectly inhibited the up-regulation of caspase-3 but failed to reverse the cell viability. The above findings indicated that the growth inhibitory effect of combined treatment largely depended on mitochondria-associated caspase-independent apoptosis. The intracellular behavior of apoptosis-inducing factor (AIF) following depolarization of Delta Psi m suggested that AIF executed such a caspase-independent apoptosis. Interestingly, caspase-dependent apoptosis appeared within 6 h, whereas the caspase-independent apoptosis lagged. Thus, the addition of DHMEQ to TNF-alpha was capable of inducing caspase-independent apoptosis in pancreatic cancer cells. Once caspase-independent apoptosis was induced, the apoptosis demonstrated powerful cytotoxicity. Therefore, DHMEQ in combination with TNF-alpha may be a promising treatment for pancreatic cancer.

Dual targeting of transformed and untransformed HTLV-1–infected T cells by DHMEQ, a potent and selective inhibitor of NF-κB, as a strategy for chemoprevention and therapy of adult T-cell leukemia

AbstractHuman T-cell leukemia virus type I (HTLV-1) causes adult T-cell leukemia (ATL), a fatal T-cell leukemia resistant to chemotherapy, after more than 50 years of clinical latency from transmission through breast-feeding. Polyclonal expansion of virus-infected T cells predisposes them to transformation. Constitutive activation of nuclear factor-κB (NF-κB) in the leukemic cells is essential for their growth and survival. Blocking NF-κB has been shown to be a potential strategy to treat ATL. We tested this approach using a novel NF-κB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), and also examined its application to chemoprevention by selective purging of the HTLV-1-infected cells. DHMEQ inhibited NF-κB activation in primary ATL cells and cell lines derived from them and induced apoptotic cell death. NF-κB inhibition down-regulated expression of genes involved in antiapoptosis or cell-cycle progression. DHMEQ protected severe combined immunodeficiency (SCID) mice inoculated with HTLV-1-transformed cells from death. In addition, DHMEQ selectively targeted HTLV-1-infected cells in the peripheral blood of virus carriers in vitro, resulting in a decreased number of infected cells. We conclude that NF-κB is a potential molecular target for treatment and prevention of ATL. As a potent NF-κB inhibitor, DHMEQ is a promising compound allowing the translation of this strategy into clinical medicine. (Blood. 2005;106:2462-2471)

Prevention of Cancer Cachexia by a Novel Nuclear Factor κB Inhibitor in Prostate Cancer

To investigate the association between serum interleukin-6 (IL-6) and cachexia in patients with prostate cancer and the inhibitory effect of a new nuclear factor kappaB (NF-kappaB) inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), on IL-6 production and cachexia in an animal model of hormone-refractory prostate cancer. The association between serum IL-6 levels and variables of cachexia was evaluated in 98 patients with prostate cancer. The inhibitory effects of DHMEQ on IL-6 secretion and cachexia were investigated in in vitro and in vivo studies using JCA-1 cells derived from human prostate cancer. Serum IL-6 levels were significantly elevated and cachexia developed in JCA-1 tumor-bearing mice as well as in prostate cancer patients with progressive disease. IL-6 secretion was significantly inhibited in JCA-1 cells exposed to DHMEQ. Intraperitoneal administration of DHMEQ (8 mg/kg) to tumor-bearing mice produced a significant amelioration of the reduction in body weight, epididymal fat weight, gastrocnemius muscle weight, hematocrit, and serum levels of triglyceride and albumin when compared with administration of DMSO or no treatment. DHMEQ caused a significant decrease of serum IL-6 level in JCA-1 tumor-bearing mice (all P < 0.05). These results suggested an association between serum IL-6 and cachexia in patients with prostate cancer and in JCA-1 tumor-bearing mice and that a new NF-kappaB inhibitor, DHMEQ, could prevent the development of cachexia in JCA-1 tumor-bearing mice presumably through the inhibition of IL-6 secretion. DHMEQ seems to show promise as a novel and unique anticachectic agent in hormone-refractory prostate cancer.

In vitro and in vivo antitumor activity of the NF-κB inhibitor DHMEQ in the human T-cell leukemia virus type I-infected cell line, HUT-102

Adult T-cell leukemia (ATL) is an aggressive neoplasm caused by human T-cell leukemia virus type I (HTLV-I). The NF-κB pathway is activated in ATL cells and in virus-infected cells, and plays a central role in oncogenesis. We examined the effect of the novel NF-κB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), on a well-characterized HTLV-I-infected cell line, HUT-102, in vitro and in vivo. DHMEQ inhibited translocation of NF-κB p65 to the nucleus and induced apoptotic cell death in vitro. In vivo, DHMEQ inhibited the growth and infiltration of HUT-102 tumor cells transplanted subcutaneously in SCID mice lacking natural killer cell activity.

Dehydroxymethylepoxyquinomicin, a novel nuclear factor-κB inhibitor, induces apoptosis in multiple myeloma cells in an IκBα-independent manner

Nuclear factor-kappaB (NF-kappaB) is constitutively activated in multiple myeloma cells. Several proteasome inhibitors have been shown to be effective against multiple myeloma and may act by inhibiting degradation of IkappaBalpha. Here, we examined the biological effects of a new type of NF-kappaB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), which is reported to directly inhibit the cytoplasm-to-nucleus translocation of NF-kappaB. A multiple myeloma cell line, 12PE, which is defective for IkappaBalpha protein, was utilized to determine if IkappaBalpha is concerned with the action of DHMEQ. Meanwhile, U266 was used as a multiple myeloma cell line with normal IkappaBalpha. A proteasome inhibitor, gliotoxin, which is an inhibitor of degradation of phosphorylated IkappaBalpha, failed to inhibit translocation of NF-kappaB in 12PE. In contrast, DHMEQ equally inhibited translocation of NF-kappaB to the nucleus and induced apoptosis to both multiple myeloma cell lines, suggesting that apoptosis resulting from DHMEQ is IkappaBalpha independent. DHMEQ also induced apoptosis in freshly isolated multiple myeloma cells. After DHMEQ treatment, cleavage of caspase-3 and down-regulation of cyclin D1 were observed in both cell lines. In addition, administration of DHMEQ resulted in a significant reduction in tumor volume in a plasmacytoma mice model compared with control mice. Our results show that DHMEQ could potentially be a new type of molecular target agent for multiple myeloma.

Inhibition of inflammatory cytokine secretion from mouse microglia cells by DHMEQ, an NF-κB inhibitor

Activation of microglia has been implicated in various neurodegenerative disorders, and thus the inhibition of microglial activity may suppress these disorders. Earlier we designed and synthesized an NF-κB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ) that showed anti-inflammatory and anti-tumor activities in vivo. In the present research, we studied whether DHMEQ would inhibit the activation of mouse microglial cells. DHMEQ inhibited lipopolysaccharide (LPS)-induced activation of NF-κB in an electrophoresis mobility shift assay. It also inhibited LPS-induced secretions of TNF-α and IL-6 from mouse microglial cell line 6-1 cells.

In vivo antitumor activity of the NF-κB inhibitor dehydroxymethylepoxyquinomicin in a mouse model of adult T-cell leukemia

Adult T-cell leukemia (ATL) is an aggressive neoplasm caused by human T-cell leukemia virus type I (HTLV-I). The nuclear transcription factor, NF-kappaB, is induced by HTLV-I and is central to the ensuing neoplasia. To examine the effect of a novel NF-kappaB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), on ATL in vivo, we developed an improved severe combined immunodeficiency (SCID) mouse model for ATL. Five-week-old SCID mice in which natural killer (NK) cell activity had been eliminated were inoculated intraperitoneally with the HTLV-I-infected cell lines, TL-Om1, MT-1, MT-2 and HUT-102. No engraftment of TL-Om1 cells and little tumorigenesis of MT-1 cells were detected 40 days after injection. In contrast, inoculation of mice with MT-2 and HUT-102 cells elicited high mortality, 100% frequency of gross tumor formation and tumor cell infiltration of various organs, all of which were reduced by coadministration of DHMEQ during the inoculation. Moreover, tumors from mice treated with DHMEQ had a high frequency of apoptosis. These results suggest that DHMEQ induces apoptosis in HTLV-I-transformed cells in vivo, resulting in inhibition of tumor formation and organ infiltration, thereby enhancing survival.

Targeting of Nuclear Factor κB Pathways by Dehydroxymethylepoxyquinomicin, a Novel Inhibitor of Breast Carcinomas: Antitumor and Antiangiogenic Potential In vivo

Abstract We previously designed and synthesized the new nuclear factor κB (NF-κB) inhibitor dehydroxymethylepoxyquinomicin (DHMEQ) derived from the structure of the antibiotic epoxyquinomicin C. We looked into the effect of DHMEQ on cellular phenotypes and tumor growth in mice injected with human breast carcinoma cell line MDA-MB-231 or MCF-7. In estrogen-independent breast adenocarcinoma cell line MDA-MB-231, NF-κB is constitutively activated. The addition of DHMEQ (10 μg/mL) completely inhibited the activated NF-κB for at least 8 hours. On the other hand, NF-κB is not activated in estrogen-dependent MCF-7 cells. In this cell line, DHMEQ completely inhibited the tumor necrosis factor-α-induced activation of NF-κB. DHMEQ did not inhibit the degradation of IκB but inhibited the nuclear translocation of NF-κB by both p65/p50 and RelB/p52 pathways. MDA-MB-231 cells secrete interleukin (IL)-6 and IL-8 without stimulation, and DHMEQ decreased the secretion levels of both cytokines. When MDA-MB-231 or MCF-7 cells were stimulated by tumor necrosis factor-α, the inhibitory effects of DHMEQ were still maintained. I.p. administration of DHMEQ (thrice a week) significantly inhibited the tumor growth of MDA-MB-231 (12 mg/kg) or MCF-7 (4 mg/kg) in severe combined immunodeficiency mice. No toxicity was observed during the experiment, including the loss of body weight. An immunohistological study on resected MCF-7 tumors showed that DHMEQ inhibited angiogenesis and promoted apoptosis. Furthermore, in Adriamycin-resistant MCF-7 cells highly expressing multidrug resistance gene-1, DHMEQ also exhibited the above capability, including down-regulation of IL-8. Thus, DHMEQ might be a potent drug for the treatment of various breast carcinomas by inhibiting the NF-κB activity.

Effect of a small molecule inhibitor of nuclear factor-κB 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.

Targeting NF-κB and Induction of Apoptosis by Dehydroxymethylepoxyquinomicin (DHMEQ) in Multiple Myeloma Cells.

We previously designed and synthesized a new NF-κB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ) (J Biol Chem, 2002). DHMEQ is a derivative of the weak antibiotics epoxyquinomicin C, which was isolated from the culture broth of Amycolaptosis sp. NF-κB is a critical regulatory protein that activates the transcription of a number of genes, including growth factors, angiogenesis modifiers, cell adhesion molecules and anti-apoptotic factors. As NF-κB has been shown as a good target for the new therapies such as bortezomib, we studied the effects of the new specific NFκB inhibitor, DHMEQ, to myeloma cells. In the present study, we demonstrated that DHMEQ inhibited the proliferation of human myeloma cell lines, RPMI8226 and U266 in dose- and time-dependent manners. Apoptosis was detected using fluorescein-conjugated Annexin-V by FACS. Around 45.3%of RPMI8226 and 45.2% of U266 were in apoptosis 12 hours after treatment with 10 μg/ml DHMEQ. Formation of apoptotic bodies were observed 24 hour-treatment with DHMEQ in both cell lines by Giemsa staining. In contrast, no obvious cell cycle arrest was observed with DHMEQ, indicating DHMEQ directly induces apoptosis without cell cycle arrests in these myeloma cell lines. The activation of caspase-3 in RPMI8226 and U266 cells were detected with the specific antibody against the active form of caspase-3 by FACS. When the myeloma cells were pretreated with 20 μM pan-caspase inhibitor, z-VAD-FMK, DHMEQ-induced apoptosis was inhibited by 62.1% in RPMI8226 and 71.9% in U266 cells, indicating DHMEQ-induced apoptosis was caspase-dependent. The binding activities of nuclear NF-κB protein to the oligonucleotides including NF-κB binding sites was suppressed by 81.9% in RPMI8226 and 69.0% in U266 1 hour after treatment with DHMEQ. NF-κB protein seemed more accumulated in cytoplasm of myeloma cells after treatment with DHMEQ under the confocal microscope, indicating DHMEQ prevents the translocation of NF-κB protein into the nucleus. Bcl-XL is the anti-apoptotic factor and its transcription is regulated by NF-κB. However, the expression level of Bcl-XL protein was not altered 24 hours after treatment with DHMEQ in RPMI8226 and U266. We also studied the effects of DHMEQ to the patient materials. We found that DHMEQ induced apoptosis in CD138-positive plasma cells from the myeloma patients (n=3), demonstrating that DHMEQ is also effective for primary cells. We previsously developed the model of human multiple myeloma by simply injecting U266 cells into the tail vein of the immunodeficient NOG mice. This myeloma model demostrated the massive osteolytic lesions and hind leg paralysis around 7 weeks after transplantation. We did not observe any invasion of U266 cells into other organs except bone marrow. As NF-κB regulates the proliferation of myeloma cells and osteoclasts, we expect DHMEQ will inhibit the tumor growth and prevent pathological fractures by inducing apoptosis in both myeloma cells and osteoclasts in vivo. We are currently evaluating the in vivo efficacies of DHMEQ using this experimental animal model of multiple myeloma. In conclusion, we demonstrated that DHMEQ targets NF-κB and induces apoptosis in myeloma cells through caspase-dependent pathways.

Induction of Thyroid Cancer Cell Apoptosis by a Novel Nuclear Factor κB Inhibitor, Dehydroxymethylepoxyquinomicin

The objective of the study was to determine the effects of a novel selective nuclear factor kappaB (NF-kappaB) inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), in thyroid carcinoma cells in vitro and in vivo and to additionally elucidate the molecular mechanisms underlying the action of this chemotherapeutic agent. In the in vitro experiments, the induction of apoptosis by DHMEQ in various human thyroid carcinoma cell types was determined by flow cytometry analysis of annexin-V binding and the caspase activation by Western blotting. For the in vivo study, female nu/nu mice were xenografted with s.c. FRO thyroid tumors. DHMEQ solution was injected i.p. at a dose of 8 mg/kg/day for two weeks. Tumor dimensions were monitored twice weekly, and apoptosis in tumor specimens was determined by terminal deoxynucleotidyl transferase-mediated nick end labeling staining. Treatment with DHMEQ substantially inhibited the translocation of p65 and p50 NF-kappaB subunits to the nucleus, the DNA-binding activity of the RelA/p65, NF-kappaB-dependent expression of the inhibitor of apoptosis (IAP)-family proteins, cIAP-1, cIAP-2, and XIAP, and the de novo synthesis of inhibitor of nuclear factor kappaB alpha. At concentration levels ranging from 0.1 to 5 microg/ml, DHMEQ induced a caspase-mediated apoptotic response that could be abrogated by the c-Jun NH(2)-terminal kinase inhibitor SP600125 but not by either mitogen-activated protein/extracellular signal-regulated kinase kinase or p38 inhibitors. In contrast, normal human thyrocytes were resistant to DHMEQ-induced apoptosis. At higher doses of DHMEQ we observed the necrotic-like killing of both normal and malignant thyrocytes, which was resistant to mitogen-activated protein kinase inhibitors. In nude mice DHMEQ substantially inhibited tumor growth without observable side effects, and increased numbers of apoptotic cells were observed in the histologic sections of tumors treated with DHMEQ. Our results show the potential usefulness of the novel NF-kappaB inhibitor, DHMEQ, in future therapeutic strategies for the treatment of thyroid cancers that do not respond to conventional approaches.