Fig. 4

Esophageal cancer cells incompletely repair DNA double strand breaks induced by particle irradiation. Normalized γH2AX levels at 2 and 24 h after irradiation with biologically isoeffective doses of photons (X), protons (¹H) and heavy ions (¹²C, ¹⁶O) (mean and SD of n = 3 replicate samples). Values were corrected for cell cycle-specific differences as detailed in Materials and Methods. *p < 0.05, **p < 0.01 (two-sided Student’s t-test against unirradiated controls)