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Melanoma is one of the most lethal skin malignancies in the world. Interferons (IFNs) have been also demonstrated in response to tumor cell and IFNs such as IFN-α have been used for melanoma treatment. The long chain double-stranded RNA (dsRNA) (from a variety of nonviral sources) is a potent activator of the IFN system and an inducer of cell apoptosis. Panaxadiolsaponins (PDS) is a major Panax ginseng-derived active component with known antitumor activity and immune modulation. Here, we investigated a hypothesis that the combination of PDS and total natural dsRNA (as opposed to the synthetic dsRNA) will suppress tumor growth better than the individual agents. We have evaluated the antitumor and immunostimulatory effects of the combination of natural long chain dsRNA (derived from yeast) and PDS on melanoma cell line B16 and mice xenograft model. The underlying mechanisms of growth suppression were investigated by analyzing dsRNA-activated pathways, apoptosis, and cell cycle. Natural dsRNA and PDS exert superior anticancer effects than either agent alone. Natural dsRNA and PDS combination might be a promising strategy for treating malignancies, including melanoma.

Interferon-gamma (IFN-gamma) regulates a number of cellular genes using a variety of cellular signaling pathways. Previously, we identified a novel IFN-regulated element, IFN-gamma-activated transcriptional element (GATE), in the promoter of the murine IFN regulatory factor-9 (IRF-9) gene. This element binds to novel factors. We have recently characterized a novel regulatory factor, GATE binding factor 1 (GBF1), which promoted IFN-gamma-induced transcription. Although GBF1 was a potent inducer of transcription, it did not bind to DNA well in vitro. To understand its role in IFN-gamma-induced actions, we raised monoclonal antibodies (mAb) against GBF1. These antibodies are highly useful in Western, immunoprecipitation, and immunocytochemical analyses. Employing these antibodies, we show that GBF1 is recruited to the endogenous IRF-9 promoter. We also show GBF1 interacts with CAAAT/enhancer binding protein-beta (C/EBP-beta), the other GATE binding factor. Furthermore, other cytokines, such as interleukin-1 (IL-1) and IL-6, induced the expression of GBF1. These antibodies may be useful tools for investigating the role of GBF1 in cytokine-induced responses.

A combination of interferon-beta (IFN-beta) and all-trans retinoic acid (IFN/RA) induces tumor cell apoptosis via some unknown mechanisms. Apoptosis is a gene-directed process that limits the proliferation of undesired cells. Several genes are required to regulate cell death in the higher-order animals. Earlier, we employed a gene expression knockout technique to isolate cell death-related genes. A novel gene, the gene associated with retinoid-interferon-induced mortality-19 (GRIM-19), was found to be essential for tumor cell death induced by IFN/RA. Here, we describe the development and characterization of three monoclonal antibodies (mAbs) against GRIM-19. GRIM-19 is present in the nucleus and cytoplasm. Its expression is induced by the IFN/RA combination. We also show that GRIM-19 inhibits the cell-transforming property of viral oncogenic protein viral IFN regulatory factor-1 (vIRF-1) via a physical interaction. mAbs developed in this study should be useful for studying the other physiologic roles of GRIM-19 and serve as a potent tool for studying tumor responses to IFN/RA therapy.