Proliferation assays were undertaken in an attempt to ascertain the optimal dose of IR to maximize cytokine production while minimizing cell death. (A) Proliferation assays after radiation exposure demonstrated a dose of 5 Gy to yield the optimal setting of cytokine up-regulation with minimal cell death (n = 6). (B) Apoptotis of hypoxic cells with and without 5 Gy radiation exposure was assessed by annexin V expression. Cells exposed to 5 Gy radiation showed a decrease in apoptosis, suggesting a cytoprotective role. This dose was therefore used for all subsequent experiments (n = 3).