Specific IKKbeta inhibitor IV blocks Streptonigrin-induced NF-kappaB activity and potentiates its cytotoxic effect on cancer cells.
ABSTRACT Many anticancer agents activate NF-kappaB, which plays an important role in the survival of cancer cells. Inhibition of NF-kappaB activity may therefore potentiate the efficacy of anticancer agents. We found that a previously used anticancer agent Streptonigrin (SN) was also a potent NF-kappaB inducer. Using a specific IKKbeta inhibitor IV (Podolin et al., J Pharmacol Exp Ther 2005; 312: 373-381), we revealed that the activation of NF-kappaB was mediated through DNA damage-induced activation of IKK complex. Furthermore, we demonstrated that SN-induced DNA damage was unrelated to reactive oxygen species but to the hydroquinone form of SN converted by the NAD(P)H:quinine oxidoreductase (NQO1). The study suggests that the combination of SN with IKK inhibitor may improve efficacy over the use of single agent.
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ABSTRACT: Human T cell leukemia virus type 1 (HTLV-1) inhibits host antiviral signaling pathways although the underlying mechanisms are unclear. Here we found that the HTLV-1 Tax oncoprotein induced the expression of SOCS1, an inhibitor of interferon signaling. Tax required NF-κB, but not CREB, to induce the expression of SOCS1 in T cells. Furthermore, Tax interacted with SOCS1 in both transfected cells and in HTLV-1-transformed cell lines. Although SOCS1 is normally a short-lived protein, in the presence of Tax, the stability of SOCS1 was greatly increased. Accordingly, Tax enhanced the replication of a heterologous virus, vesicular stomatitis virus (VSV), in a SOCS1-dependent manner. Surprisingly, Tax required SOCS1 to inhibit RIG-I-dependent antiviral signaling, but not the interferon-induced JAK/STAT pathway. Inhibition of SOCS1 by RNA-mediated interference in the HTLV-1-transformed cell line MT-2 resulted in increased IFN-β expression accompanied by reduced HTLV-1 replication and p19(Gag) levels. Taken together, our results reveal that Tax inhibits antiviral signaling, in part, by hijacking an interferon regulatory protein.Journal of Virology 07/2011; 85(14):6955-62. · 5.08 Impact Factor
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ABSTRACT: Accumulating evidence supports the concept that melanoma is highly heterogeneous and sustained by a small subpopulation of melanoma stem-like cells. Those cells are considered as responsible for tumor resistance to therapies. Moreover, melanoma cells are characterized by their high phenotypic plasticity. Consequently, both melanoma stem-like cells and their more differentiated progeny must be eradicated to achieve durable cure. By reevaluating compounds in heterogeneous melanoma populations, it might be possible to select compounds with activity not only against fast-cycling cells but also against cancer stem-like cells. Natural compounds were the focus of the present study. We analyzed 120 compounds from The Natural Products Set II to identify compounds active against melanoma populations grown in an anchorage-independent manner and enriched with cells exerting self-renewing capacity. Cell viability, cell cycle arrest, apoptosis, gene expression, clonogenic survival and label-retention were analyzed. Several compounds efficiently eradicated cells with clonogenic capacity and nanaomycin A, streptonigrin and toyocamycin were effective at 0.1 µM. Other anti-clonogenic but not highly cytotoxic compounds such as bryostatin 1, siomycin A, illudin M, michellamine B and pentoxifylline markedly reduced the frequency of ABCB5 (ATP-binding cassette, sub-family B, member 5)-positive cells. On the contrary, treatment with maytansine and colchicine selected for cells expressing this transporter. Maytansine, streptonigrin, toyocamycin and colchicine, even if highly cytotoxic, left a small subpopulation of slow-dividing cells unaffected. Compounds selected in the present study differentially altered the expression of melanocyte/melanoma specific microphthalmia-associated transcription factor (MITF) and proto-oncogene c-MYC. Selected anti-clonogenic compounds might be further investigated as potential adjuvants targeting melanoma stem-like cells in the combined anti-melanoma therapy, whereas selected cytotoxic but not anti-clonogenic compounds, which increased the frequency of ABCB5-positive cells and remained slow-cycling cells unaffected, might be considered as a tool to enrich cultures with cells exhibiting melanoma stem cell characteristics.PLoS ONE 01/2014; 9(3):e90783. · 3.53 Impact Factor
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ABSTRACT: Various inflammatory stimuli that activate the nuclear factor kappa B (NF-κB) signaling pathway converge on a serine/threonine kinase that displays a key role in the activation of NF-κB: the I kappa B kinase β (IKK-β). Therefore, IKK-β is considered an interesting target for combating inflammation and cancer. In our study, we developed a ligand-based pharmacophore model for IKK-β inhibitors. This model was employed to virtually screen commercial databases, giving a focused hit list of candidates. Subsequently, we scored by molecular shape to rank and further prioritized virtual hits by three-dimensional shape-based alignment. One out of ten acquired and biologically tested compounds showed inhibitory activity in the low micromolar range on IKK-β enzymatic activity in vitro and on NF-κB transactivation in intact cells. Compound 8 (2-(1-adamantyl)ethyl 4-[(2,5-dihydroxyphenyl)methylamino]benzoate) represents a novel chemical class of IKK-β inhibitors and shows that the presented model is a valid approach for identification and development of new IKK-β ligands.Bioorganic & medicinal chemistry letters 10/2010; 21(1):577-83. · 2.65 Impact Factor