NANOG-conjugated Toll-Like Receptor 7 Agonist Suppresses Tumor Growth in Testicular Embryonic Carcinoma

Background Induced pluripotent stem cells (iPSCs) present gene expression profiles similar to cancer cells. Thus, the iPSCs could be used as a cancer vaccine. However, the iPSCs-based vaccines might lead to tumorigenesis, and strategies to solve this problem are urgently required. In this study, we evaluated the use of NANOG, an iPSC marker, in the propagation of cancer vaccines.Methods We designed the T7a-NANOG conjugate, a cancer vaccine, by covalently combining toll-like receptor 7 agonist (T7a) with NANOG. The in vitro cytokine induction was assessed using the enzyme-linked immunosorbent assay. We then used a testicular embryonic cancer challenge BALB/c mice model for prophylactic vaccination. The cytotoxic T lymphocyte (CTL) activity and antibody-dependent cellular cytotoxicity (ADCC) were determined using the lactose dehydrogenase assay, whereas CD4⁺/IL-4⁺ T cells and CD4⁺/IFN-γ⁺ cells were evaluated using flow cytometric assays. Further, we assessed the side effects of the vaccine through routine blood tests, testicular weight index measurement, and sperm morphology and histopathological organ examinations.Results Our analysis showed rapid interferon-γ (IFN-γ) and IL-12 induction in a bone marrow-derived dendritic cell line of the mice treated with the T7a-NANOG conjugate. Additionally, immunization of the T7a-NANOG-treated BALB/c mice significantly increased tumor-specific survival rates by improving T-cell responses, such as induction of CTLs, CD4⁺/IL-4 + T, CD4⁺/IFN-γ+, cells, and ADCC. Of note, the T7a-NANOG conjugate was associated with minimal toxicity, without adverse autoimmunity as well as vaccine-associated peripheral blood cytopenia.Conclusions Our data demonstrated that the T7a-NANOG conjugate triggered tumor-specific adaptive immune reactions, which caused delayed growth of primary tumor cells in the testicular embryonic carcinoma BALB/c mice model.