B7-H3 and 4-1BBL cooperatively enhance the antitumor response of CD8 T cells in oral cancer

Abstract

The aim of this study was to enhance the antitumor immunity of CD8 T cells directed against human oral cancer using B7-H3 and 4-1BBL gene transfer. Recombinant replication-defective adenovirus 5 (Adv) expressing human 4-1BBL, B7-H3 or 4-1BBL/B7-H3 was constructed using the two-plasmid rescue method. Primary human oral cancer cell vaccines (OCV) were prepared by treating cells with 20 μg/ml mitomycin-C after primary human oral cancer cells were infected with Adv transduced with 4-1BBL, B7-H3, 4-1BBL/B7-H3 or control Adv. Then, autologous, purified CD8 T cells were stimulated by coculture with OCV for 4 days. At the end of the culture, CD8 T cell activation was evaluated by ELISA to assay the production of IFNγ and IL-2 in the culture supernatants. Cytotoxic CD8 T cell effector function was analyzed by a 51Chromium (Cr)-release assay, and CD8 T cell proliferation was evaluated by flow cytometry and Cell Counting Kit-8 (CCK-8) assays. Primary human oral cancer cells expressed low levels of B7-H3 and 4-1BBL and weakly stimulated autologous T cells. The primary human oral cancer cell vaccine transduced with the combination of 4-1BBL with B7-H3 retroviruses resulted in significantly enhanced CD8 T cell activation and proliferation. This was associated with increased IFNγ and IL-2 production by CD8 T cells and improved CD8 T cell proliferation. CD8 T cells stimulated with the autologous B7-3/4-1BBL primary human oral cancer cell vaccine efficiently killed the autologous parental B7-H3/4-1BBL primary human oral cancer cells. Strong CD8 T cell activation, proliferation and longer survival time could be obtained by this vaccine. These data provide a mechanism for developing tumor vaccines using modified tumor cells in patients with oral cancer. © 2011 American Scientific Publishers.