Dendritic Cells Derived from K562/A02 Cell Line Treated by Recombinant Adenovirus Encoding Human p53

Purpose Leukemia, a malignant tumor derived from hemotological system, belongs to a malignant clone disease of hemopoietic stem cell. Studies of immunology have indicated a close relationship between occurrence and development of leukemia and immunity of organism. Immunotherapy can completely clear up residual leukemic cells and cure the disease. The occurrence of multidrug resistance ( MDR ) is known for the main barrier of leukemia chemical therapy. And also, dendritic cells ( DCs ) are the most potent antigen-presenting cells for initiating cellular immune responses in vivo. DCs are attractive immunoregulatory cells for cancer immunotherapy, and their efficacy has been investigated in clinical trials. If we can induce multidrug resistant leukemic cell into a DC which is named with multidrug resistant leukemia-derived DC and promote its maturity with effective and harmless drugs, multidrug resistant leukemia-derived DC not only carries the special antigens of leukemia but also can present the special antigens to immune system to kill corresponding leukemic cells. At the same time, it can reverse indirectly leukemic multidrug resistance. Tumor suppressor gene p53 is pivotal in the regulation of apoptosis, and p53-based immunization is an attractive approach to cancer immunotherapy because of the mutant of p53 protein in malignant but not in normal cells. It has been shown that monocyte-derived human dendritic cells transduced with an adenoviral wild-type p53 (wt-p53) construct mediate the antitumor immune responses against p53-overexpressing tumor cells. We examined whether K562/A02 Cells -derived dendritic cells pulsed with the purified full-length wt-p53 protein were also capable of inducing the specific antitumor responses against K562/A02 cells in vitro.

Methods P53 gene was transferred to monoclonal K562/A02 cells. P53 gene transcription was detected with RT-PCR. Proliferation test was conducted by using ³H-thymidine (³H-TdR) incorporation. Immature dendritic cells generated in the presence of interleukin-4 and granulocyte/macrophage colony-stimulating factor from K562/A02 cell line were transduced with an wt-p53. Uptake of p53 protein by dendritic cells was assessed by Western blotting. Induction of p53-specific CTL response was also evaluated by the cytotoxic assay against K562/A02 cells.

Results Both Western blotting and and immunohistochemical analysis showed the accumulation of p53 protein in immature dendritic cells. T cells obtained from peripheral blood mononuclear cells of healthy volunteers were stimulated with wt-p53 and then applied to the cytotoxicity assay against the target cells-K562/A02. The CTL activity generated by adenoviral wt-p53-transduced dendritic cells was specific for K562/A02 cells.

Conclusion Our results indicate that adenoviral wt-p53-transduced dendritic cells could induce the specific antitumor effect against the target tumor cells and that this in vitro model offers a new and more simple approach to the development of p53 and dendritic cellsbased immunogenetherapy. This offers a novel and promising immunogenetherapeutic srtategy to overcome multidrug resistant leukemia in the future.