IR was selected as the DNA damaging agent because a) it is effective and commonly used in cancer therapy, b) it reliably induces G2 accumulation in M059J and Fus-1 cells allowing direct comparison with the cell cycle data and c) published data indicates 1 μM VE-821 is a potent radiosensitiser [25] Interpretation of γH2AX data (Figure 4A) is somewhat complicated by the fact that DNA-PKcs is the major kinase responsible for H2AX phosphorylation immediately after IR. Here, PRKDC is linked to cancer.