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Abstract: The effects of BCG heat shock protein 70 (BCG HSP70) gene transfection on tumorigenicity and immunogenicity of murine lymphocytic leukemia cell line (L1210) were studied. After HSP70 gene transfection, the tumor cells became strongly immunogenic and lost their tumorigenicity in syngeneic mice. It mainly exhibited that tumor growth was slow or without the formation of tumor, mean survival time of mice was significantly prolonged and a marked stimulating effect on L1210 specific Th1 cells detected by IFN-γ ELISPOT assay. Tumor-bearing mice treated with the L1210-HSP70 cells showed thorough coagulation necrosis and abundant CD8+ T lymphocyte infiltration. Meanwhile, as the tumor vaccine, the HSP70-transfected tumor cells could induce a protective immune response in vivo. It showed that the tumor growth was significantly inhibited, tumor diameter was markedly reduced and the survival time of tumor-bearing mice was further prolonged. Immunization with it also resulted in regression of the established L1210 tumor and prolonged survival time of mice. These results suggest that gene transfection of BCG HSP70 could effectively improve the immunogenicity of tumor cells and it may be used as a suitable candidate gene-modified cell vaccine for cancer immunotherapy. [Copyright &y& Elsevier]