Development of Thrombospondin 1 shRNA as anti-cancer agent

• Main Authors: Tzu-YangWeng, 翁子洋
• Other Authors: Ming-Derg Lai
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/36626879905977351109

博士 === 國立成功大學 === 基礎醫學研究所 === 102 === Induction of thrombospondin 1 (TSP-1) is generally assumed to suppress tumors by inhibiting angiogenesis; however, it is less clear how the TSP-1 in dendritic cells (DCs) influences tumor progression. We hypothesized that silencing TSP-1 expression in DCs via skin administration of TSP-1 shRNA (short hairpin RNA) plasmid may produce antitumor effects by inducing immune responses. In this study, we investigated three specific aims: First, we evaluated whether down-regulating the expression of TSP-1 in DCs may enhance antitumor response. Second, the possible immunological mechanisms of antitumor response induced by TSP-1 shRNA were explored. Third, to investigate the application of TSP-1 shRNA in anti-cancer therapy, TSP-1 shRNA was combined with neu DNA vaccine. In this study, we found that skin administration of TSP-1 shRNA produced anticancer therapeutic effects. The therapeutic effects were not likely due to off-target effect since three TSP-1 shRNA targeting different sites showed therapeutic effects. Tumor-infiltrating CD4+ and CD8+ T cells were increased after administration of TSP-1 shRNA. The expression of interleukin-12 (IL-12) and interferon-γ (IFN-γ) in the lymph nodes was enhanced by injection of TSP-1 shRNA. Lymphocytes from the mice injected with TSP-1 shRNA selectively killed the tumor cells, and the cytotoxicity of lymphocytes was abolished by the depletion of CD8+ T cells. Injection of CD11c+ TSP-1-knockout (TSP-1-KO) bone marrow-derived dendritic cells (BMDCs) delayed tumor growth in tumor-bearing mice. Similarly, anti-tumor activity induced by TSP-1-KO BMDCs was abrogated by the depletion of CD8+ T cells. TSP-1 shRNA did not exhibit antitumor activity in MBT-2-tumor bearing NOD-SCID mice. In contrast, the administration of shRNA targeting TSP-2, another TSP family member, did not extend the survival of tumor-bearing mice. Finally, TSP-1 shRNA functioned as an immunotherapeutic adjuvant to augment the therapeutic efficacy of Neu-DNA vaccination. Together, our results implicate that the downregulation of TSP-1 in DCs produces an effective anti-tumor response that is opposite to the pro-tumor effects by silencing of the TSP-1 within tumor cells.