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[Dendritic cell-tumor cell fusion vaccine prevents growth of subcutaneous transplanted esophageal carcinomas].

BACKGROUND AND OBJECTIVE
Our previous studies have shown that dendritic cell (DC)-tumor cell fusion vaccine can induce specific antitumor response against esophageal carcinoma cells. This study was to investigate the inhibitory effect of intratumor injection of the antigen-specific cytotoxic T lymphocytes (CTLs) induced by DC-tumor cell fusion vaccine against subcutaneously transplanted esophageal carcinoma cells in nude mice, and to analyze the influence of DC/tumor cell fusion vaccine on proliferation and apoptosis of esophageal carcinoma cells.


METHODS
Fusion cell vaccine of mature DCs with EC109 cells were generated by the polyethylene glycol (PEG) protocol and the antigen-specific CTLs were induced. The models of transplanted human esophageal carcinoma in nude mouse were established using EC-109 cell line. Thirty-three nude mice with subcutaneous tumors were randomly divided into three groups. Subcutaneous tumors of group A (n=11), group B (n=11) and group C (n=11) were intratumorally injected with the CTLs induced by DC/tumor fusion vaccine, T lymphocytes and RPMI 1,640 medium respectively once a week. After four weeks of intratumor injection, the nude mice were killed and the nodules were anatomized. The mean volume and weight of tumors of each group were measured, and the tumor inhibitory rates of the Group A and the Group B were calculated and compared. The expression of proliferating cell nuclear antigen (PCNA) was detected by immunohistochemistry (S-P method). The mean PCNA-label index (LI) of three groups was compared. The cell cycle and cell apoptosis of the xenograft tumor cells were analyzed by flow cytometry. The mean S-phase fraction (SPF) and the mean rate of cell apoptosis of three groups was compared respectively.


RESULTS
Both the mean volume and the mean weight of xenograft tumors in group A (881.45+/-31.14 mm3 and 0.88+/-0.04 g) were significantly smaller than those of group B (1493.37+/-51.67 mm3 and 1.38+/-0.07 g) and group C (2065.77+/-87.55 mm3 and 2.04+/-0.11 g). The tumor inhibitory rates of Group A was significantly higher than that of group B (56.86% vs. 32.35%, F=1218.08, P=0.001). The mean PCNA-LI of xenograft tumors was less in the group A (26.83+/-0.95)% than in the group B (51.82+/-1.51)% and group C (68.93+/-2.40)% (F=1528.39, P=0.000). The mean SPF of xenograft tumors was less in the group A (12.46+/-0.36)% than in the group B (29.39+/-0.96)% and the group C (42.25+/-1.43)% (P<0.05). The mean apoptotic rate of xenograft tumors was less in the group A (38.03+/-1.21)% than in the group B (17.75+/-0.56)% and the group C (6.59+/-0.22)% (P<0.05).


CONCLUSION
The model of subcutaneous xenograft tumors in nude mice using human esophageal carcinoma cell line EC-109 has been successfully established. CTLs induced by DC/tumor fusion vaccine has specific antitumor immunity efficacy in vivo. CTLs can inhibit the proliferation of tumor cells and induce apoptosis of tumor cells in local tumors.