Figure 1.

Viable cancer cell supernatants prime whereas supernatants of apoptotic cells suppress specific cytotoxicity. (A) Experimental outline. Human monocyte-derived DC were controls or incubated with supernatants of viable (VCM), apoptotic (ACM) or necrotic (NCM) MCF-7 cells at a ratio of 1:1 (Supernatants of 2 × 10⁵ MCF-7 added to 2 × 10⁵ DC) for 16 h. Subsequently, supernatants were removed by washing and autologous T cell-enriched PBMC were added at a ratio of 10:1 (Tcells/DC) and cultured for another 3 d. The resulting polarized T cells were then co-cultured with living tumor cells for 4 h to determine cytotoxicity as described under Materials and Methods. Experimental interventions as outlined in the manuscript are indicated as dotted arrows. (B) CellTracker Blue-stained MCF-7 cells were incubated with T cells from individual co-cultures at effector to target (E:T) ratios of 0.1:1, 0,5:1, 1:1, 1:2, 1:5, 1:10, 1:20 for 4h. Cytotoxicity calculated for the ACM, VCM, NCM groups was compared to the control group. Data are means ± SEM from five individual donors. (C) CellTracker Blue-stained MCF-7 cells were incubated with T cells from individual co-cultures as well as control T cells at ratios of 1:5 for 4 h. Cytotoxicity was calculated compared to non co-cultured MCF-7. Data are means ± SEM from five individual donors. (D) CellTracker Blue-stained MCF7 (black bars) or T47D (white bars) breast carcinoma cells were incubated with T cells from individual co-cultures at 1:5 ratio for 4 h prior to cytotoxicity measurements. Data are means ± SEM from four individual donors. Asterisks indicate significant differences between groups, * = p < 0.05. p-values were calculated using ANOVA with Bonferroni’s correction.