Figure 2.

Combining intratumorally injected heat-killed bacteria with adoptive T cell therapy prevents tumor relapse. (A) MC57 SIY-LO cancer cells were injected s.c. onto the backs of OT-1 mice. Tumors were established ≥2 weeks prior to being treated with intravenously-injected adoptively-transferred activated 2C T cells, intratumoral HK bacteria, or combined 2C T cells + HK bacteria. Data represent mice compiled from three independent experiments, with each experiment consisting of each treatment group. The tumor relapse rate following combined treatment with HK bacteria and T cells was significantly lower (p < 0.05) compared to either monotherapy. Similarly, MC57 EGFP tumors were treated with the combination of HK bacteria and 2C T cells in two independent experiments. Blue arrows represent the initial time of treatment and the green cross represents one mouse death. (B) Re-isolated cancer cells from two relapsed MC57 SIY-LO tumors following monotherapy 2C T cell treatment were analyzed for SIY expression by EGFP fluorescence using flow cytometry. The MC57 parental and MC57 SIY-LO cell line, that was originally injected into mice, were used in this analysis. Data represent three relapsed tumors from two independent experiments.