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.

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