Human chorionic gonadotropin ß (hCGß) is a kind of pregnancy hormones, moreover, it is a tumor-associated antigen ectopically expressed on a variety of human non-trophoblastic tumors such as pancreatic cancer, bladder cancer and lung cancer. Therefore, hCGß is considered as an ideal target antigen. However, as a self-antigen, hCGß is tolerated by the immune system and immune response is hardly induced. 9-mer of L-arginine (Arg9), a type of cell penetrating peptide, can play an important role in the translocation process.
Firstly, we designed and constructed two eukaryotic expressing plasmids including pCDNA3.1-hCGß-Arg9 (phCGß-Arg9) and pCDNA3.1-hCGß (phCGß). Secondly, B16.E5, a B16 cell line expressing hCGß, was acquired by transfected B16-F10 cells with phCGß and selected with G418. Meanwhile we constructed hCGß-Arg9 gene modified tumor cell vaccine by transient transfection of phCGß-Arg9 into B16-F10 cells with liposome. Finally, we took the prophylactic vaccination experiment in vivo to investigate the protective efficacy and the immune mechanisms.
The transfectant with highest expression of hCGß was screened and named B16.E5 as a tumor model in this experiment. The results of protective experiment demonstrated 60% mice of hCGß-Arg9 group were protected from the challenge of B16.E5 cells. Moreover, survival benefit was also observed in mice vaccinated with the hCGß-Arg9 tumor vaccine (48.4 ± 4.9 days) compared with controls. Then, the experiments for immune mechanism were conducted, including T lymphocytes adoptive transfer experiment, CTL-mediated cytotoxicity analysis, hCGß antibody tests of serum after vaccination and serum transfer analysis. All of these suggested cellular immunity, rather than humoral immunity, may play the major role in the antitumor activity.
We designed and constructed the tumor cell vaccine modified with hCGß-Arg9 gene and demonstrated that this vaccine can induce cellular immunity, through which the vaccine can play protective efficacy in animal experiments. Our work may contribute to designing novel generation of tumor vaccines.
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Department of Thoracic Oncology, Cancer Center, State Key Laboratory of Biotherapy, West China Hospital, West China Medical School, Sichuan University, Chengdu, Sichuan, China
National Natural Science Funds of China (81402561)
All authors have declared no conflicts of interest.