Potent immunotherapy against well-established thymoma using adoptively transferred transgene IL-6-engineered dendritic cell-stimulated CD8+ T-cells with prolonged survival and enhanced cytotoxicity

Abstract

Background: Adoptive transfer of CD8(+) T-cells specific for tumor-antigens is an attractive strategy for anti-tumor therapy. In the present study, the subsets TA and TB were used to represent the population of CD8(+) T cells generated by culturing the respective cells with irradiated dendritic cells (DCs) pulsed with ovalbumin (OVA) protein and transfected with adenoviral vector constructs as described.

Methods: Naïve OVA specific CD8(+) T cells were isolated from the spleen of OVA-specific T-cell receptor transgenic OTI mice. The subsets TA and TB were then generated by in vitro activating the population of CD8(+) T cells with OVA-pulsed DCs transfected with IL-6-expressing adenoviral vector (AdVIL-6 ) or the control vector (AdVNull ). To assess their in vivo immunotherapeutic effects, TA - or TB -cells were intravenously transferred into C57BL/6 mice bearing EG7 thymoma (6-8 mm in diameter).

Results: TA -cells displayed a higher level of expression of CD62 l, IL-7R, FasL, perforin and CCR6, and also exhibited more potent in vitro cytotoxicity to OVA-expressing EG7 thymoma cells via perforin- and Fas/FasL-mediated apoptosis than TB -cells. CD8(+) T-cell survival was kinetically analyzed in C57BL/6 mice transferred with TA - or TB -cells by flow cytometry. We found that the adoptively transferred TA -cells had prolonged survival and enhanced T-cell memory development compared to TB -cells. In addition, TA -, but not TB -cells were able to eradicate well-established EG7 thymomas in all eight tumor-bearing mice.

Conclusions: Our data suggest that AdVIL-6 -transfected DC-stimulated CD8(+) T cells with potent cytotoxicity and survival advantage may serve as an effective adoptive CD8(+) T-cell immunotherapy strategy for anti-tumor treatment.

Keywords: EG7 thymoma; adoptive T-cell transfer; cytotoxicity; immunotherapy; memory; survival.