The recruitment of osteoclast precursors toward osteoblasts and subsequent cell-cell interactions are critical for osteoclast differentiation. Chemokines are known to regulate cell migration and adhesion. CX3CL1 (also called fractalkine) is a unique membrane-bound chemokine that has dual functions for cells expressing its receptor CX3CR1: a potent chemotactic factor in its soluble form and a type of efficient cell adhesion molecule in its membrane-bound form. In this paper, we demonstrate a novel role of CX3CL1 in osteoblast-induced osteoclast differentiation. We found that osteoclast precursors selectively expressed CX3CR1, whereas CX3CL1 is expressed by osteoblasts. We confirmed that soluble CX3CL1 induced migration of bone marrow cells containing osteoclast precursors, whereas immobilized CX3CL1 mediated firm adhesion of osteoclast precursors. Furthermore, a blocking mAb against CX3CL1 efficiently inhibited osteoclast differentiation in mouse bone marrow cells cocultured with osteoblasts. Anti-CX3CL1 also significantly suppressed bone resorption in neonatal mice by reducing the number of bone-resorbing mature osteoclasts. Collectively, CX3CL1 expressed by osteoblasts plays an important role in osteoclast differentiation, possibly through its dual functions as a chemotactic factor and adhesion molecule for osteoclast precursors expressing CX3CR1. The CX3CL1-CX3CR1 axis may be a novel target for the therapeutic intervention of bone resorbing diseases such as rheumatoid arthritis, osteoporosis, and cancer bone metastasis.

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Japanese traditional herbal medicine (Kampo) have been used to improve the general physical condition after surgery and to mitigate the side effects of radiation and chemotherapy in tumor patients. Juzentaihoto (JTT) consists of ten medical herbs, and is also called Shi-Quan-Da-Bu-Tang in Chinese herbal medicine. Among Kampo medicines, JTT has especially gained attention as a biological response modifier. Currently, clinical trials of various tumor vaccine therapies are being performed world-wide. However, tumor antigens that are inoculated as vaccines do not have high immunogenicity; thus, it is difficult to obtain an effective therapeutic effect. Thus, it is necessary to develop a tumor vaccine adjuvant that is more potent and very safe. In the present study, we examined the efficacy of JTT as an oral adjuvant when given together with tumor vaccines. As a result, JTT enhanced the phagocytic ability of OVA antigen and the presentation ability of OVA antigen in dendritic cells in vitro. Furthermore, tumor growth was markedly decreased, and the survival period was significantly prolonged in mice inoculated with mouse lymphoma, which is expressed with tumor model antigen. In conclusion, these findings suggest that JTT can be used with tumor vaccines as an immune adjuvant.

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Abstract. Chemokines are known to have anti-tumor effects due to their chemoattractant properties, which stimulate the accumulation of infiltrating immune cells in tumors. CCL22 (macrophage-derived chemokine, MDC) attracts killer T cells, helper T cells and antigen-presenting cells expressing the CCL22 receptor, CCR4. Thus, CCL22 gene expression results in the accumulation of these cells in tumors, and has been shown to suppress lung and colon cancer growth in mice. In the present study, early-stage subcutaneous tumor growth in a mouse multiple myeloma cell line stably expressing CCL22 (MPC-CCL22) was decreased compared to tumor growth in control cells (MPC-mock). However, the final extent of tumor growth in these cell lines was almost equivalent. Regulatory T cells, which express CD25, CD4 and CCR4, are known to cause immune disruption. We therefore investigated the association of regulatory T cells with the progressive decrease in CCL22 anti-tumor effect observed in late-stage experimental multiple myelomas. Tumor growth in MPC-CCL22 cells was observed to drastically decrease, to the point of complete tumor regression, when CD4 or CD25 T cells were depleted. Here, we document the drastic anti-tumor effect of a combination of CCL22 and anti-CD25 antibody on multiple myeloma cells. IntroductionChemokines are a family of small cytokines that primarily induce the directed migration of hematopoietic cells when bound to their seven-transmembrane, G protein-coupled receptors (1,2). Because they function as chemoattractants for several immune effector cell types, chemokines are attractive candidates for immune cell-based approaches to cancer gene therapy. Several studies describe the anti-tumor effects induced by infiltrating immune cells upon their chemokine-mediated accumulation within the tumor mass. The regression of XCL1 (lymphotactin)-expressing engineered myeloma was mediated by increased infiltration of T cells, neutrophils and macrophages, leading to a reduction in tumorigenicity (3,4). CCL22 (macrophage-derived chemokine, MDC) is a CC chemokine that appears to be specifically secreted by a macrophage. CCL22 is a potent chemoattractant for CD8 and CD4 T cells, as well as for dendritic cells expressing the CCL22 receptor CCR4 (5,6), and is involved in chronic inflammation mediated by the continuous homing of dendritic cells and lymphocytes (7,8). Solid tumor growth in mice was suppressed by the recruitment of these cell types into tumors induced to express CCL22 using an adenoviral vector (9). Due to its tendency to function as a chemoattractant for killer T cells, helper T cells and antigen-presenting cells, CCL22 is considered to be an attractive candidate gene for immune cell-based cancer therapy. However, one drawback for such CCL22-based therapy is the immunosuppressive condition caused by the fact that CCL22 also recruits regulatory T cells into the tumor mass. Here, we demonstrate that a drastic anti-tumor CCL22 effect can be sustained in multiple myeloma tumors by reducing the recruitment of regulatory...