Genetically engineered neural stem cells expressing cytosine deaminase and interferon-beta enhanced T cell-mediated antitumor immunity against gastric cancer in a humanized mouse model.

AIMS: Gastric cancer (GC) is an invasive, fatal disease with a poor prognosis. Gene-directed enzyme prodrug therapy via genetically engineered neural stem cells (GENSTECs) has been widely studied in various malignancies, such as breast, ovarian, and renal cancer. In this study, the human neural stem cells expressing cytosine deaminase and interferon beta (HB1.F3.CD.IFN-ß) cells were applied to convert non-toxic 5-fluorocytosine to cytotoxic 5-fluorouracil and secrete IFN-ß. MATERIALS AND METHODS: Human lymphokine-activated killer cells (LAKs) were generated by stimulating human peripheral blood mononuclear cells (PBMCs) by interleukin-2, and we evaluated the cytotoxic activity and migratory ability of LAKs co-cultured with GNESTECs or their conditioned media in vitro. A GC-bearing human immune system (HIS) mouse model was generated by transplanting human PBMCs followed by subcutaneous engraftment of MKN45 cells in NSG-B2m mice to evaluate the involvement of T cell-mediated anti-cancer immune activity of GENSTECs. KEY FINDINGS: In vitro studies showed the presence of HB1.F3.CD.IFN-ß cells facilitated the migration ability of LAKs to MKN45 cells and activated their cytotoxic potential. In MKN45-xenografted HIS mice, treatment with HB1.F3.CD.IFN-ß cells resulted in increased cytotoxic T lymphocyte (CTL) infiltration throughout the tumor, including the central area. Moreover, the group treated to HB1.F3.CD.IFN-ß showed increased granzyme B expression in the tumor, eventually enhancing the tumor-killing potential of CTLs and significantly delaying tumor growth. SIGNIFICANCE: These results indicate that the HB1.F3.CD.IFN-ß cells exert anti-cancer effects on GC by facilitating the T cell-mediated immune response, and GENSTECs are a promising therapeutic strategy for GC.