['Potent antitumor responses can be induced through cytokine immunotherapy. Interleukin (IL)-2 and granulocyte-macrophage colony-stimulating factor (GM-CSF) are among the most effective cytokines to induce tumor-specific systemic immune responses and can act synergistically. To overcome the limitations of combined use of these two cytokines, we have constructed an IL2-GMCSF fusion protein and characterized its antitumor effects in this study.', 'The expression of IL-2 receptor and GM-CSF receptor of cell lines were detected with quantitative real-time PCR. On this basis, the bioactivities of IL2-GMCSF, especially effects on DC2.4 cells were assayed. Another function of IL2-GMCSF-bridge two types of cells-was assessed by cell contact counting and cytotoxicity assays. The anti-tumor activity in vivo of IL2-GMCSF was evaluated in the melanoma model. The statistical significance among treatment groups were determined by One-Way ANOVA.', 'The fusion protein IL2-GMCSF maintained the activities of IL-2 and GM-CSF, and could significantly promote DC2.4 cell activities, including phagocytosis, proliferation and cytokine secretion. In addition to the inherent cytokine activity, IL2-GMCSF bridges direct cell-cell interactions and enhances splenocyte killing efficacy against multiple tumor cell lines in vitro. Co-injection of IL2-GMCSF and inactivated B16F10 mouse melanoma cells induced complete immunoprotective responses in about 30 % of mice.'] Does fusion cytokine IL-2-GMCSF enhance anticancer immune responses through promoting cell-cell interactions?