Figure 2. Sublethal exposure to ²²³Ra increases CTL lysis of breast, prostate, and lung carcinoma cells in vitro.

(A) Tumor cells were either left untreated (0 Gy, white bars) or exposed to 4 Gy (grey bars) or 10 Gy (black bars) of ²²³Ra over a 96-h incubation period, then used as targets in an overnight CTL lysis assay. CEA-, MUC-1-, and brachyury-specific CD8⁺ T cells were used as effectors at an E:T ratio of 30:1. (B) CTL HLA restriction was verified by incubating tumor cells with anti-HLA-A2 blocking mAb (top) or by performing the killing assay with CEA⁺HLA-A2⁻ AsPC-1 cells as target controls (bottom). Experiments were repeated 1–3 times with similar results. *denotes statistical significance relative to untreated cells (P < 0.05).