A DNA vaccine against extracellular domains 1-3 of flk-1 and its immune preventive and therapeutic effects against H22 tumor cell in vivo

摘要

AIM: To construct a DNA vaccine against extracellular domains 1-3 of fetal liver kinase-1 (flk-1), and to investigate its preventive and therapeutic effect against H22 cell in vivo. METHODS: Flk-1 DNA vaccine was produced by cloning extracellular domains 1-3 of flk-1 and by inserting the cloned gene into pcDNA3.1 (+). Fifteen mice were divided into 3 groups and inoculated by vaccine, plasmid and saline respectively to detect specific T lymphocyte response. Thirty Mice were equally divided into preventive group and therapeutic group. Preventive group was further divided into V, P, and S subgroups, namely immunized by vaccine, pcDNA3.1 (+) and saline, respectively, and attacked by H22 cell. Therapeutical group was divided into 3 subgroups of V, P and S, and attacked by H22, then treated with vaccine, pcDNA3.1 (+) and saline, respectively. The tumor size, tumor weight, mice survival time and tumor latency period were compared within these groups. Furthermore, intratumoral microvessel density (MVD) was assessed by immunohistochemistry. RESULTS: DNA vaccine pcDNA3.1 (+) flk-1-domains 1-3 was successfully constructed and could raise specific CTL activity. In the preventive group and therapeutic group, tumor latency period and survival time were significantly longer in vaccine subgroup than that in P and S subgroups (P<0.05); the tumor size, weight and MVD were significantly less in vaccine subgroup than that in P and S subgroups (P<0.05). The survival time of therapeutic vaccine subgroup was significantly shorter than that of preventive vaccine subgroup (P<0.05); the tumor size, and MVD of therapeutic vaccine subgroup were significantly greater than that of preventive vaccine subgroup (P<0.05). CONCLUSION: DNA vaccine against flk-1 domains 1-3 can stimulate potent specific CTL activity; and has distinctive prophylactic effect on tumor H22; and also can inhibit the tumor growth in vivo. This vaccine may be used as an adjuvant therapy because it is less effective on detectable tumor.