| This thesis explores using four different strategies to manipulate our immune system to generate T cell immunity toward hepatocellular carcinoma (HCC): (i) fusion cells generated from dendritic cells (DCs) combined with the HCC cell line SMMC-7721; (ii) stable CD80 cDNA-transfected BEL-7402 cells; (iii) DCs transduced with recombinant adenovirus encoding a novel CT antigen (HCA661); and (iv) T3 cells, a TAP-deficient cell line transfected with CD80, presenting co-stimulatory element on the cell surface. All four experimental approaches were able to arouse anti-tumor specific CD8+ T cell activity in vitro, showing that these strategies could activate the body's naive T cells to become cytotoxic T lymphocytes (CTLs)---the major effector cells targeting HCC cells.; In the first approach, HCC SMMC-7721 cells were fused with DCs. The resulting dendritoma was determined to possess the features of an antigen presenting cell and was able to present HCC-specific tumor antigen. Dendritomas were co-cultured with autologous T cells, resulting in activation of T cell proliferation and priming of naive T cells to induce MHC class I restricted lysis of HCC SMMC-7721 cells.; In the second approach, cDNA encoding co-stimulatory molecule CD80 was introduced into ICAM-1+ HCC BEL-7402 cells. The CD80-tranfected cells were able enhance the immunogenicity of BEL-7402 cells as detected by T cell proliferation assay. The CD80-transfected cell line was able to activate T cells which subsequently induced cell lysis of the SMMC-7721, QGY-7703 and parent BEL-7402 cell lines as detected by cytotoxicity assay.; In the third approach, a recombinant adenovirus expressing the full-length cDNA of a novel cancer/testis (CT) antigen gene HCA661 was constructed and transduced into immature DCs. After maturation, the transduced DCs were able to prime naive T cells to become CTLs. Intracellular flow cytometry and enzyme-linked immunospot (ELISPOT) assay showed that these CTLs were able to target a hepatoma cell line, HepG2, which is HLA-A2 and HCA661 positive.; In the last approach of this thesis, T2 (a TAP-deficient cell line) cells were stably transfected with CD80 by electroporation and the CD80 positive cells were identified. The newly developed stable transfected cell line, T3, expressing CD80 on its surface, was able to present exogenous HLA-A2 associated peptides and directly activate CTL reaction as detected by ELISPOT assay. The results demonstrate that T3 cells could be used for the identification of CTL epitopes in vitro and could potentially be important for the development of peptide vaccines in immunotherapy.; The results from all four experiments have provided basic data for developing future tumor vaccines against HCC. |
