[Treatment of hepatic cancer in mice by beta-elemene combined DC/Dribble vaccine: an immune mechanism research].

Objective: To observe the therapeutic effects of beta-elemene combined DC/Dribble vaccine in treating mice with hepatic cancer, thus exploring their anti-tumor mechanisms.

Methods: Dentritic cells were derived from Balb/c mice's spleen and their phenotypes were identified. Using hepatic cancer cell line BNL1MEA.7R.1 (abbreviated as BNL) originated from Balb/c mice as target cell, DC/Dribble vaccine was prepared via raising the antigen representing carrier autophagosomes (DRips in Blebs, DRibbles), which were rich in tumor antigen information. The mice previously immunized were divided into 4 groups, i.e., the control group, the beta-elemene group, the vaccine group, and the combined group. The PBS was subcutaneously and intraperitoneally injected to mice in the control group. The beta-elemene was intraperitoneally injected at the daily dose of 50 mg/kg to mice in the beta-elemene group and the combined group for 7 successive days. DC/Dribble vaccine was injected into the lymph node of mice in the vaccine group and the combined group on the 1st day, and DC/Dribble vaccine was subcutaneously injected on the 3rd day and the 5th day. All the mice were sacrificed on the 10th day. Their spleens were obtained sterilely, and the suspension was incubated with or without Dribble. The cells were inoculated for 72 h. The contents of IFN-gamma in the supernatant were measured by ELISA. In addition, the spleen cells obtained from the combined group were incubated with different stimulations for 72 h, which were then divided into the control group, the DRibble group, the DC group, and the DC/Dribble vaccine group. The supernatant of cultured cells were collected and the contents of IFN-gamma were measured by ELISA. The liver tumor-bearing mouse model was established, and then the BNL bearing mice were randomly divided into 4 groups, i.e., the control group, the beta-elemene group, the vaccine group, and the combined group. The treatment ways were the same as the immune ways. The tumor size and the survival period were observed in each group. On the 23rd day the mice were sacrificed. The tumor tissue was stripped and stained by HE staining. The pathomorphological manifestations of the tumor tissue were observed by light microscope.

Results: In vitro detection of mice immunized previously by different ways showed that the secretion of IFN-gamma was significantly higher in the combined group than in the rest groups (P < 0.01). The secretion of IFN-gamma was significantly higher in the beta-elemene group and the vaccine group than in the control group (P < 0.01). The spleen cells could be stimulated to secrete a large amount of IFN-gamma in the vaccine group and the Dribble group (P < 0.01). When the beta-elemene was 10 microg/mL as the stimulating dose, the secretion of IFN-gamma obviously increased (P < 0.01). In vivo observation showed that the growth velocity of tumors in mice of the combined group was slowed down. There was statistical difference in the tumor area or the survival period of mice in the combined group, when compared with the other groups (P < 0.01). In HE staining, the surrounding connective tissues of the tumor were wrapped tightly and compactedly, with infiltration of a large amount of inflammatory cells.

Conclusions: beta-elemene combined DC/Dribble vaccine could induce specific immune cells to secrete secretory cells, thus exerting its anti-tumor effect. Its immunological effects might be associated with enhancing the DC antigen presenting function.