Synergistic combination of murine bone marrow-derived dendritic cells loaded ex vivo with whole tumor lysate and systemic chemotherapy mediates antitumor immune responses in vivo

In order to get mature dendritic cells (DC) that is a crucial prerequisite for success in tumor immunotherapy protocols. Herein, we assumed that administration of murine bone marrow (BM)-derived DC (BM-DC), loaded ex vivo with whole Ehrlich ascites carcinoma (EAC) lysate, in the context of systemic chemotherapy cyclophosphamide (CTX) to induce antitumor immune responses, may be a good strategy to improve the presentation of tumor-specific antigens to the immune system. In the first series of experiments, BM cells generated either from BM of naïve mice or from BM of EAC-bearing mice were cultured in the presence of GM-CSF and IL-4 for 6 days. At day 7, cells were loaded for 48 h with one of the following maturation agents: EAC lysate (1 mg/ml), poly-inosinic: polycytidylic acid [poly(I:C)] (25 μg/ml) or mRNA encoding human telomerase reverse transcriptase (hTERT-mRNA) (2 μg/ml). In the second series of experiments, EAC-bearing mice were intraperitoneally (i.p.) injected with CTX followed by i.p. vaccination with DC, loaded ex vivo with EAC lysate. DC yield and the phenotypic expression of maturity-related surface markers of DC (i.e. CD11b and CD11c) in both series of experiments were investigated. As a result, a significant decrease in the number of DC generated from poly(I:C)-supplemented BM culture from EAC-bearing mice has been detected. Loading of BM cells with poly(I:C), EAC lysate or hTERT-mRNA could induce the expression of CD11b and CD11c. Additionally, vaccination of EAC-bearing mice with DC loaded ex vivo with EAC lysate following CTX treatment, resulted in increases in the percentage of multiple populations of CD11b+CD11c+ in BM, spleen and peripheral blood (PB). To conclude, further researches to clarify the mechanism involved in DC maturation are crucial not only to comprehend DC biology but also to optimize DC immunotherapy protocols.