Combined CD4+ Th1 effect and lymphotactin transgene expression enhance CD8+ Tc1 tumor localization and therapy.

Type 1 T cells are the major components in antitumor immunity. The lack of efficient CD8(+) cytotoxic T (Tc) cell infiltration of tumors is a major obstacle to adoptive Tc-cell therapy. We have previously demonstrated that adenovirus (AdV)-mediated transgene lymphotactin (Lptn) expression by intratumoral AdVLptn injection and intravenous CD4(+) helper T (Th) cell transfer can enhance Tc-cell tumor infiltration and eradication of early stage tumors (5 mm in diameter). In this study, we generated ovalbumin (OVA)-specific Tc1 and Th1 cells in vitro by incubation of OVA-pulsed dendritic cells with naive T cells from T-cell receptor (TCR) transgenic OT I and OT II mice. We then investigated the potential synergy of Th1 help effect and Lptn transgene expression in Tc1-cell therapy of well-established OVA-expressing EG7 solid tumors (7 mm in diameter). Our data showed that a combined adoptive T-cell therapy of Th1 (2.5 x 10(6) cells per mouse) and Tc1 (5 x 10(6) cells per mouse) resulted in regression of all eight (100%) transgene Lptn expressed EG7 tumors, which is significantly higher than four from eight (50%) in AdVLptn/Tc1 group and two from eight (25%) in Tc1/Th1 group (P < 0.05). The amount of transferred Tc1 cells detected in Lptn-expressed tumors with Th1 treatment is 0.72%, which is significantly higher than those of AdVLptn (0.22%), Th1 (0.41%) and the control AdVpLpA (0.09%) treatment groups (P < 0.05). Enhanced Tc1 tumor localization may be derived from the chemotactic effect of Lptn and the proliferative effect of Th1 and Lptn. This novel therapeutic strategy with enhancement of Tc1 tumor localization in the therapy of well-established tumors may become a tool of considerable conceptual interest in the implementation of future clinical objectives.