*, < 0.05; **, < 0.005. level. Conditioned medium from antigen-stimulated bone marrow-derived mouse mast cell cultures induced the expression of HDAC3, MCP1, and CCR2, a receptor for MCP1, in B16F1 mouse melanoma cells and enhanced migration and invasion potential of B16F1 cells. The conditioned medium from B16F10 cultures induced the activation of Fc?RI signaling in lung mast cells in an HDAC3-dependent manner. Fc?RI signaling was observed in lung tumors derived from B16F10 cells. Target scan analysis predicted HDAC3 to be as a target of miR-384, and miR-384 and HDAC3 were found to form a opinions regulatory loop. miR-384, which is usually decreased by PSA, negatively regulated HDAC3 expression, allergic inflammation, and the positive opinions regulatory loop between anaphylaxis and tumor metastasis. We show the miR-384/HDAC3 opinions loop to be a novel regulator of the positive opinions relationship between anaphylaxis and tumor metastasis. and (23). Although we reported the role of HDAC3 in allergic skin inflammatory reactions, such as passive cutaneous anaphylaxis (23), the role of HDAC3 in PSA has not been investigated. Furthermore, the possible role of HDAC3 in mediating an conversation between tumor and mast cells remains. MicroRNAs (miRNAs) are small, single-stranded noncoding RNAs that play important functions in the Mevalonic acid post-transcriptional regulation of gene expression in mammalian Mevalonic acid cells by regulating translation. The inhibition of mmu-miR-106a decreases interleukin (IL) 1C10 expression while increasing pro-inflammatory cytokine expression (24). Alveolar macrophage-derived vascular endothelial growth factor (VEGF) is necessary for allergic airway inflammation in asthmatic mice, and miR-20b negatively regulates the expression of VEGF (25). miR-1248 interacts with the IL-5 transcript in the 3-untranslated region and serves as a positive regulator of IL-5 expression (26). Let-7 miRNA inhibits allergic lung airway inflammation by decreasing the expression of IL-5 (27). miRNA let-7a regulates the expression of IL-13, a cytokine necessary for allergic lung disease (28). The down-regulation of miR-145 inhibits Th2 cytokine production and airway hyper-responsiveness (29). These reports address the functions of miRNAs in allergic inflammation and in mediating the conversation between tumor and mast cells. To date, miRNAs that bind to and regulate the expression of HDAC3 BTLA and participate in mediating tumor and mast cell conversation have not been identified. In this study, we examined the relationship between PSA and tumor metastasis, with the aim of delineating the PSA-mediated molecular mechanisms in enhancing the tumorigenic and metastatic potential of tumor cells. We investigated the effect of HDAC3 and the effect of MCP1, a target of HDAC3-mediated up-regulation, on PSA and the positive opinions relationship between anaphylaxis and tumor. We recognized miR-384 as a novel regulator of HDAC3. We investigated the effect of miR-384 on allergic inflammation and on the tumor-mast cell conversation using a mouse melanoma model. In this study, we provide evidence that a miR-384/HDAC3 opinions regulatory loop functions as a novel regulator of the positive opinions relationship between anaphylaxis and tumor metastasis. EXPERIMENTAL PROCEDURES Cell Culture Rat basophilic leukemia (RBL2H3) cells were obtained from the Korea Cell Collection Lender (Seoul, Korea). Cells were produced in Dulbecco’s altered Eagle’s medium made up of heat-inactivated fetal bovine serum, 2 mm l-glutamine, 100 models/ml penicillin, and 100 g/ml streptomycin (Invitrogen). Cultures were managed in 5% CO2 at 37 C. Bone marrow-derived mast cells (BMMC) and lung mast cells were isolated and managed according to the standard procedures (30). Malignancy cell lines used in this study were cultured in Dulbecco’s altered minimal essential medium (DMEM; Invitrogen) supplemented with heat-inactivated 10% fetal bovine serum (FBS, Invitrogen) and antibiotics at 37 C in a humidified incubator with a mixture of 95% air flow and 5% CO2. Chemicals and Reagents Oligonucleotides used in this study were commercially synthesized by the Bionex Co. (Seoul, Korea). DNP-HSA and DNP-specific IgE antibody were purchased from Sigma. Chemicals used in this study were purchased from Sigma. All other antibodies were purchased from Cell Signaling Co. (Beverly, MA). Anti-mouse and anti-rabbit IgG-horseradish peroxidase-conjugated antibody was purchased from Pierce. Lipofectamine and PlusTM reagent for transfection were purchased from Invitrogen. Cytokine ELISA kit was purchased from Koma Biotech (Seoul, Korea). Mice Female 5C6-week-old BALB/c mice were purchased from Orient Co. (Seongnam, Korea). All animal care, experiments, and euthanasia were performed in accordance with protocols approved by the Kangwon National University Animal Research Committee (Chunchon, Korea). To measure tumorigenic potential, mouse melanoma B16F1 cells (1 106 cells in 100 l of PBS), after induction of passive systemic anaphylaxis, were injected subcutaneously into the right flank of each mouse (= 5). Tumor growth was evaluated by measuring the tumor diameters with calipers and calculating the tumor volumes Mevalonic acid using an approximated formula for any prolate ellipsoid as follows: volume = ((is the longest axis of the tumor, and is the shortest axis. After 3.