OBJECTIVE: METHODS: The combination of the Toll like receptor (TLR) ligands and/or 5-Fu/ oxaliplatin was added into myeloid-derived DCs in vitro culture. DC phenotypic changes were detected by flow cytometry, and the secretion of DC cytokines was detected by cytometric bead array (CBA). A MC38 mouse colon cancer model was constructed and the DCs were isolated from the spleen, tumor tissue and lymph nodes following intraperitoneal injection of 5-Fu/ oxaliplatin. The cell phenotypes were detected by flow cytometry. The tumor infiltrating leukocytes, splenocytes and lymph node cells were co-cultured with the dead MC38 tumor cells, and the secretion levels of interferon-γ (IFN-γ) were detected. 5-Fu/ oxaliplatin combined with our previously developed CD1d-MC38/α-GC tumor vaccine was used to inhibit the growth of MC38 colon cancer in mice, and the tumor growth rate and survival time were recorded. RESULTS: 5-Fu/ oxaliplatin exerted no significant effect on the expression of the stimulating phenotypes of DCs in vitro, while it could reduce the expression of programmed death ligand 1/2 (PD-L1/L2) and promote interleukin-12 (IL-12) secretion by DCs. Furthermore 5-Fu/ oxaliplatin was beneficial to the differentiation of T-helper 1 (Th1) cells. 5-Fu/ oxaliplatin further enhanced the stimulating phenotypic expression of DCs in tumor bearing mice, decreased PD-L1/L2 expression, and specifically activated the lymphocytes. The CD1d-MC38/α-GC tumor vaccine combined with 5-Fu/ oxaliplatin could exert a synergistic role that resulted in a significant delay of the tumor growth rate, and an increase in the survival time of tumor bearing mice. CONCLUSIONS: 5-Fu/ oxaliplatin decreased the expression of the DC inhibitory phenotypes PD-L1/L2, promoted DC phenotypic maturation in tumor bearing mice, activated the lymphocytes of tumor bearing mice, and exerted synergistic effects with the CD1d-MC38/α-GC colon cancer tumor vaccine.
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