Strengthening of antitumor immune memory and prevention of thymic atrophy mediated by adenovirus expressing IL-12 and GM-CSF

Interleukin (IL)-12 and granulocyte-monocyte colony-stimulating factor (GM-CSF) have recently been used as immunotherapeutic agents in cancer gene therapy. IL-12 and GM-CSF have differential roles in the antitumor immune response, as IL-12 targets T, NK and natural killer T (NKT) cells and GM-CSF principally targets antigen-presenting cells (APCs). To strengthen the therapeutic efficacy of these two cytokines, we generated an oncolytic adenovirus (Ad), Ad-Delta B7/IL12/GMCSF, coexpressing IL-12 and GM-CSF. Using a murine B16-F10 syngeneic tumor model, we show that Ad-Delta B7/IL12/GMCSF promoted antitumor responses and increased survival compared with an oncolytic Ad expressing IL-12 or GM-CSF alone (Ad-Delta B7/IL12 or Ad-Delta B7/GMCSF, respectively). By measuring cytotoxic T lymphocyte activity and interferon-gamma production, we show that the enhanced therapeutic effect was mediated by the induction of immune cell cytotoxicity. In situ delivery of Ad-Delta B7/IL12/GMCSF resulted in massive infiltration of CD4(+) T cells, CD8(+) T cells, NK cells and CD86(+) APCs into the tissue surrounding the necrotic area of the tumor. Moreover, GM-CSF effectively promoted antitumor immune memory, which was significantly augmented by IL-12. Lastly, IL12-expressing oncolytic Ads prevented tumor-induced thymic atrophy and was associated with reduced apoptosis and increased proliferation in the thymus. Taken together, these data demonstrate that an oncolytic Ad coexpressing IL-12 and GM-CSF is a potential therapeutic tool for the treatment of cancer. Gene Therapy (2012) 19, 711-723; doi:10.1038/gt.2011.125; published online 13 October 2011This work was supported by Grants from the Ministry of Knowledge Economy (10030051, Dr C-O Yun), the Korea Science and Engineering Foundation (R15-2004-024-02001-0, 2009K001644, 2010-0029220, Dr C-O. Yun), the Korea Food and Drug Administration (KFDA-10172-332 to Dr C-O Yun), and Yonsei University College of Medicine faculty research Grant (6-2010-0052, Dr C-O Yun). Kyung-Ju Choi, Song-Nan Zhang and Ji-Seong Kim are graduate students sponsored by the Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea. Il-Kyu Choi is a graduate student sponsored by KOSEF through National Core Research Center for Nanomedical Technology, Seoul, South Korea