Figure 11.

Frequencies of normal NFF28 primary fibroblast anchorage-independent (A–I) colony formation in soft agar per unit dose ± SEM at low (≤25 cGy) and higher doses (>50 cGy) of cesium-137 γ-rays (A), 200 MeV protons (B), 290 MeV/n C-12 ions (C) and 350 MeV/n O-16 ions (D). IR-induced yields of transformants are background-corrected for levels of transformants measured in DMSO and HDACi-treated/sham-irradiated cultures (~6.1–7.2). Low dose transformation frequencies are calculated from the slope of induction from 5 to 25 cGy and the higher dose transformation frequencies obtained from the mean transformation frequencies at 1 Gy, the dose where peak (maximal) transformation occurs for both protons and C-12 ions. Both cesium-137 γ-rays and protons show a pronounced hyper-radiosensitivity for NFF28 fibroblast in vitro transformation at low doses. Asterisks mark significant differences at p-values of ≤0.05 (*), ≤0.01 (**), ≤0.001 (***), and ≤10⁻⁴ (****) by two-way ANOVA.