Synergistic effect of adoptive T-cell therapy and intratumoral interferon γ-inducible protein-10 transgene expression in treatment of established tumors

The lack of efficient T-cell infiltration of tumors is a major obstacle to successful adoptive T-cell therapy. We have previously shown that transplanted SP2/0 myeloma tumors engineered to express lymphotactin invariably induced tumor regress mediated by SP2/0 tumor-specific T cells. Herein, we further systemically characterize these activated T cells and investigate their therapeutic efficacy, either alone or with the chemokine interferon γ (IFN-γ)-inducible protein-10 (IP-10) gene therapy. Following stimulation with SP2/0 cells, these activated T cells were CD25+FasL+ L-selectinlow, expressed CXCR3 receptor and were chemoattracted by IP-10 in vitro. They comprised 64% CD4+ Th1 and 36% CD8+ Tc1 cells, both of which expressed IFN-γ, perforin, and TNF-α, but not IL-4. The activated T cells were strongly cytotoxic for SP2/0 tumor cells (79% specific killing; E:T ratio, 50), mainly via perforin-mediated pathway. Cell tracking using labeled T cells confirmed that these T cells infiltrated better into the IP-10-expressing tumors than non-IP-10-expressing ones. In vivo, combined intratumoral IP-10 gene transfer and adoptive T-cell immunotherapy for well-established SP2/0 tumors eradicated the tumors in 7 of the 8 mice. Control or IP-10 adenoviral treatments by themselves neither alter the lethal outcome for tumor-bearing mice nor did T-cell therapy by itself, although the latter two treatments did slow its time-frame. Taken together, our data provide solid evidence of a potent synergy between adoptive T-cell therapy and IP-10 gene transfer into tumor tissues, which culminated in the eradication of well-established tumor masses.