H2AX and neoplasm: To examine the unexpected role of UVRAGFS in tumour chemosensitivity, we measured the levels of γ-H2AX, a sensitive marker of double strand breaks (DSBs)35, and observed that UVRAGFS SW480-tumours accumulated higher levels of γ-H2AX than the controls, which further increased with 5-FU that produces DNA strand breaks (Fig. 6d).